Field

[0001 ] The present disclosure relates to modular building components such as building blocks, and more particularly to building blocks for use in toys or industry that are modular, inter- connectible, and/or stackable.

Background

[0002] Building blocks are widely used in the construction of structures including buildings, figures and apparatus, as toys, stationary or in industry. Building blocks which are modular, inter-connectible, and/or stackable can be used as components to create structures of many types of structures of many different shapes and configurations. Inter-connectible building blocks comprising built-in connection members are advantageous to facilitate expeditious, efficient and convenient interconnection of adjacent blocks to facilitate construction with less time and less manual work. Building blocks which can facilitate additional useful functions and properties are advantageous.

Disclosure

[0003] Modular components, for example, modular building blocks herein, are widely used in modular construction of articles such as toys, figures, furniture, cars, buildings, food, can be made of many materials, for example mouldable materials such as plastics (including hard and soft plastics), rubber (including natural and synthetic), metal, concrete, porcelain, foam, flour, etc. The building blocks can be rigid or resilient, and the rigidity or resilience can be made to suit applications by selecting appropriate materials or appropriate mix of materials.

[0004] A building block comprising a plurality of connector bearing panel members and a block peripheral wall member is disclosed. Each connector bearing panel member comprises a rigid panel member, one or a plurality of connection members integrally formed on the panel member. Each said connection member has characteristic mating mechanical features which are defined by a hollow cell member and an intermediate aperture, the intermediate aperture being a through aperture which extends through the panel member, defined by an internal peripheral of the panel member and in communication with an internal cavity defined by the hollow shell member wherein the hollow shell has a top cap portion having a top aperture in communication with the internal cavity and the intermediate aperture. The connection member, the top aperture, and the intermediate aperture or the internal periphery is axially aligned and share a common centre axis. The plurality of connector bearing panel members comprises a first connector bearing panel member having a rigid first panel member and a second connector bearing panel member having a rigid second panel member, the first panel member and the second panel member being spaced apart, parallel and interconnected by the block peripheral wall member. The first panel member, the second panel member and the block peripheral wall member cooperate to define a hollow block internal compartment inside the building block. A connector member on the first panel member has a corresponding connector member on the second panel member which is axially aligned and share a common centreline, the connector member and the corresponding connector member forming a connector member pair. The building block comprises an axially extending through- passageway. The through-passageway extending through the hollow shell members of the connection member pair. In some embodiments, the building block has a single connector bearing panel member and the other connector bearing panel member is a rigid panel member without a punctured hollow shell member or exposed electrical contacts.

[0005] The top cap portion defines a rigid end cap. The rigid cap may be arcuate or non- arcuate (for example, having a flat surface, a conical surface or frusto-conical surface) and/or having a roof surface and/or ceiling which tapers to expand on progressing towards a base surface of the panel member and extends transversely or radially about the centre axis. The hollow shell member comprises an intermediate shell portion, the intermediate shell portion surrounding said intermediate aperture, being in abutment with both the top cap portion and the panel member and connecting the end cap portion to the panel member. The intermediate shell portion joins the peripheral portion of the panel member which defines the intermediate aperture. The top portion of the hollow shell member may be arc-shaped, arch-shaped, dome- shaped, cap-shaped, egg shell shaped, or has an arc-shaped, arch-shaped, dome-shaped, cap-shaped, and/or egg-shell shaped and defines a top, a top structure, and/or a ceiling of or having any of the aforesaid shape or profile. The upper or top portion of the hollow shell member extends radially, arcuately, curved, or non-arcuate or non-curved, in more than one transverse directions or a plurality of transverse directions orthogonal to the axial direction, and spans across the intermediate aperture as a spanning structure.

[0006] A building block disclosed herein in general comprises a first surface bearing member on which a first surface is defined and a plurality of protrusion members is formed, a second surface bearing member on which a second surface is defined and a corresponding plurality of coupling receptacles is formed, and a peripheral wall portion interconnecting the first surface bearing member and the second surface bearing member. The first surface and the second surface are oppositely facing and the protrusion member extends in a first axial direction away from the first surface, the first axial direction being orthogonal to the first surface. The plurality of protrusion members on the first surface and the plurality of coupling receptacles on the second surface are axially aligned such that a protrusion member on the first surface and a corresponding coupling receptacles on the second surface cooperate to form a pair of counterpart connection members and share a common centre line. A through passageway is formed on the counterpart connection members of a connection member pair, the through- passageway extending between a first end aperture defined on a first axial end of the protrusion member and a second end aperture defined on a second axial end of the coupling receptacle, the first and second end apertures being on or along the centre line of the connection member.

[0007] In some embodiments, the through-passageway or a portion of the through- passageway is defined by an internal peripheral wall of an axially extending first tubular member, the first tubular member extending from the first axial end towards the second axial end.

[0008] In some embodiments, the first tubular member is suspended from or dependent from the first axial end of a protrusion member of a connection member. The protrusion member has a hollow protrusion body and the first tubular member is surrounded by a shell of a hollow shell member defining the hollow protrusion body. The first tubular member, the protrusion member and/or the hollow protrusion body, and the first surface may be integrally or singly moulded into a single connector bearing panel member. The transversal clearance defined by the top aperture on the hollow shell member may be comparable to that of the tubular member. The transversal clearance defined by the top aperture and/or the tubular member is substantially smaller than that of the intermediate aperture. The through-passageway or a portion of the through-passageway may be defined by an internal peripheral wall of an axially extending second tubular member, the second tubular member protruding from the second axial end and extending towards the first axial end. The second axial end is at an axial level inside a main body which is defined by the first surface bearing member, the second surface bearing member and the peripheral wall portion.

[0009] A first conductive terminal may be formed on the first axial end and/or a second conductive terminal electrically connected to the first conductive terminal is formed on the second axial end. The first conductive terminal is a protrusion terminal comprising a conductive protrusion, a receptacle terminal comprising a conductive socket or a contact pad, and the second conductive terminal is a protrusion terminal comprising a conductive protrusion, a receptacle terminal comprising a conductive socket or a conductive pad. The second conductive terminal may be a conductive socket compatible with or electrically engage-able with the conductive protrusion when the first conductive terminal is a conductive protrusion or a conductive pad, or a conductive protrusion compatible with or electrically engage-able with the conductive socket when the first conductive terminal is a conductive socket or a conductive pad. [0010] The protrusion terminal is to protrude from an axial end of the through passageway by an axial spring urge force and is to retract when an axial retraction force against the axial spring urge force is applied.

[001 1 ] In some embodiments, a plurality of protrusion members is formed on the first surface and/or a corresponding plurality of coupling receptacles is formed on the second surface to form a corresponding plurality pairs of counterpart connection member pairs.

[0012] The plurality of protrusion members comprises a first plurality of conductive terminals bearing a first electrical polarity and a second plurality of conductive terminals bearing a second electrical polarity opposite to the first electrical polarity, and adjacent conductive terminals bear opposite electrical polarity.

[0013] The protrusion members and/or the coupling receptacles may be arranged in one row, one column, a plurality of rows, and/or a plurality of columns, including circular rows and circular columns. The spacing between adjacent protrusion members in a row and/or in a column is uniform.

[0014] In some embodiments, a plurality of coupling receptacles is formed on the second surface and inside the building block main body. The plurality of coupling receptacles may comprise a first plurality of conductive terminals bearing a first electrical polarity and a second plurality of conductive terminals bearing a second electrical polarity opposite to the first electrical polarity, and adjacent conductive terminals bear opposite electrical polarity.

Figures

[0015] The present disclosure will be described by way of example and with reference to the accompanying figures, in which:

Figure 1 A is a perspective view of an example building block 100 referred to in this disclosure,

Figure 1 B is a side view of the example building block 100,

Figures 1 C and 1 D are cross-sectional views of the example building block 100 taken along line A-A' and B-B' of Figure 1A respectively,

Figure 2A is a schematic view of an example building block,

Figure 2A1 is a schematic view of another example building block,

Figure 2B is a schematic view of an example building block,

Figure 2B1 is a schematic view of another example building block,

Figure 2A2 is an exploded view of the example building block of Figure 2A, Figure 3 is a schematic view of an assembly of building block comprising a plurality of example building blocks of the disclosure,

Figure 4 is a schematic view of an assembly of building block comprising a plurality of example building blocks of the disclosure,

[0016] Figure 5A is a top perspective view of an example building block,

[0017] Figure 5B is a bottom perspective view of the building block of Figure 5A,

[0018] Figure 5C is a side elevation view of the building block of Figure 5A,

[0019] Figure 5D is a cross-sectional view taken along line X-X' of Figure 1A and axially,

[0020] Figure 5E is a locally enlarged view of a first portion of Figure 5D,

[0021 ] Figure 5F is a locally enlarged view of a second portion of Figure 5D,

[0022] Figure 5A1 is a cross-sectional view of an example assembly of building blocks formed from stacked engagement of a plurality of the building blocks of Figure 5A, and

[0023] Figure 5A2 is a locally enlarged view of a connected portion of Figure 5A1 .

Description

[0024] An example building block 100 of Figure 1 A comprises a first surface bearing member 120 on which a first surface is defined, a second surface bearing member 140 on which a second surface is defined, and a peripheral wall portion which extends between the first and the second surface bearing members. The first surface and the second surface are oppositely facing surfaces and the peripheral wall portion extends between the first surface and the second surface. The peripheral wall portion comprises a peripheral wall which extends around the outer boundaries of the first surface bearing member and the second surface bearing member. The example building block 100 is a hollow body, or a substantially hollow body, with the first surface bearing member, the second surface bearing member and the peripheral wall portion cooperating to define a main body and an internal compartment. The height of the internal compartment is defined by separation distance between the first surface bearing member and the second surface bearing member.

[0025] An example plurality of four connection members of a first type is formed on the first surface. An example corresponding plurality of four connection members of a second type is formed on the second surface. The connection members on the first surface and the connection members on the second surface are aligned such that a connection member on the first surface has a corresponding connection member on the second surface which share a common centreline. A connection member on the first surface and a corresponding connection members on the second surface which share a common centreline are referred to as a pair of centreline aligned connection members. A pair of centreline aligned connection members comprising connection members which have opposite and complementary mating features, properties and/or characteristics is referred to herein as a pair of counterpart connection members.

[0026] The example plurality of connection members of the first type is arranged in an example square matrix of two rows and two columns having uniform row and column spacing. Uniform row and column spacing means that the spacing between adjacent connection members in a row and the spacing adjacent connection members in a column is the same. A square matrix of two rows and two columns is used herein as a convenient example. The connection members may be arranged in matrixes having uniform or non-uniform spacing without loss of generality. For example, the connection members may be arranged in square matrixes of 3x3 (i.e., three rows and three columns), 4x4, 5x5, 6x6, etc.; rectangular matrixed of 2x3, 2x4, 2x5, 2x6, 3x4, 3x5, 3x6, 3x7, 4x5, 4x6, 4x7; circular matrixes of two, three, four, five etc. of concentric rows (or rings) having uniform or non-uniform spacing.

[0027] An example connection member of the first type is a male type connector device having a protrusion member defining an engagement portion such as an engagement head. The protrusion member also defines a retention portion which tapered portion intermediate an enlarged engagement portion and a base surface in the case of a snap connector. An example connection member of the second type of the example building block of comprises a coupling receptacle having a receptacle compartment which is defined by a receptacle body. The receptacle body in the example herein is a hollow protrusion member which projects away from a base surface on a panel member and/or projects into the internal compartment of the building block and comprises an engagement device characteristic of a female snap connector for anchoring on the retention portion of a corresponding male type snap connector. A connection member of the first type and a connection member of the second type herein are counterpart connection members having opposite and/or complementary mating features and properties. When counterpart connection members which are formed on different articles are brought to approach each other and then pressed together along an axis of coupling alignment or an axis of coupling engagement, mated coupling connection or mated engagement connection between the counterpart connection members will be formed and the connected pair is referred to herein as a pair of mated counterpart connection members. When the counterpart connection members are in a coupled engagement or coupled connection, the engagement member of a male connection member is received by the coupling receptacle of a counterpart female connection member in a closely or interference fitted manner. Where the counterpart connection members are snap connectors in coupled engagement or coupled connection, an enlarged engagement portion of the protrusion member is received inside the receptacle compartment of a receptacle body having a narrowed entry/exit defined by its engagement device, with the engagement device of the coupling receptacle received inside the retention portion of the protrusion member and functions as an anchoring device.

[0028] The example connection members on that first panel member and those on the second panel member of the example building block of Figure 1 A are shaped and dimensioned to form and function as a pair of counterpart snap connection members, and the snap connection members comprises a pair of counterpart snap fit connection devices having opposite, complementary and/or compatible mating features or characteristics so that the example protrusion member and the example coupling receptacle are to enter into mated coupling connection or a mated engagement connection and/or to form a snap-fit joint when they are brought together along the axis of coupling alignment or the axis of engagement alignment and press fitted together.

[0029] The protrusion member comprises a protruding body which projects away from a base on the first surface and extends away from the first surface along a first axial direction to form a free axial end. The first axial direction is orthogonal to the first base surface and is parallel to a centreline or centre axis of the protrusion member. The protrusion member is circularly symmetrical about its centreline to permit relative rotation between the protrusion member and a counterpart receiving coupling receptacle about the centreline when the protrusion member and the counterpart receiving coupling receptacle are in mated engagement connection, and/or to permit the protrusion member and the receiving coupling receptacle to enter into mated engagement connection at different relative angular orientations about the centreline.

[0030] The free axial end of the example protrusion member is a rounded free end, and more specifically, a rounded free end having the shape of a spherical cap, and the protruding body has a bulb shape or the shape of a boss. In some embodiments, the protrusion member may be a cylindrical body, for example, a cylindrical body having a narrowed base portion defined by a periphery extending groove or channel.

[0031 ] An end aperture or a top aperture is formed at the free axial end of the protrusion member and on the centreline of the protrusion member. A channel is formed inside the protrusion member. The channel projects from the end aperture and extends towards the second surface bearing member in an axial direction opposite to the first axial direction to define a portion of a through-passageway. In the example building block 100 of Figure 1 A, the protrusion body is a hollow body formed or moulded of hard plastics and the axially extending channel is defined by a tubular member which is axially dependent from the free axial end of the protrusion member and surrounded by an internal peripheral wall of the protrusion body. The tubular member extends between a first end which is on the free axial end of the protrusion member and a second end which is facing and approaching a counterpart coupling receptacle, with the tubular axis of the tubular member aligned with the centreline or centre axis of the protrusion member.

[0032] The receptacle body comprises an internal peripheral wall (or a receptacle internal peripheral wall) which defines the receptacle compartment. The internal peripheral wall defines a first axial end and a second axial end of the receptacle compartment. The first and second axial ends of the receptacle compartment are, respectively, the first and second axial ends of the coupling receptacle. The first axial end is on or proximal to the second surface (as a base surface of the coupling receptacle) and defines an entry aperture for axial entry into the receptacle compartment. The second axial end of the receptacle compartment is a distal axial end of the receptacle compartment which is distal to the second surface.

[0033] The first and second axial ends of the coupling receptacle are on the centreline of the coupling receptacle. The centreline of the coupling receptacle is also the centreline of the receptacle body and the centreline of the receptacle compartment. Each of the coupling receptacle, the receptacle body and the receptacle compartment is circularly symmetrical about the centreline to permit relative rotation between the coupling receptacle and a counterpart protrusion member in mated engagement connection therewith, and/or to permit the receiving coupling receptacle to enter into mated engagement connection with a counterpart protrusion member at different relative angular orientations about the centreline. The coupling receptacle has opposite and complementary mating features and properties to a counterpart protrusion member to facilitate mated engagement connection with a counterpart protrusion member.

[0034] The receptacle body projects away from its base surface (which is the second surface in this example) and extends along a second axial direction, the second axial direction being parallel to and opposite to the first axial direction.

[0035] The receptacle internal peripheral wall of the receptacle body is shaped and dimensioned to correspond to the shape and dimensions of a counterpart protrusion member of a counterpart connection member. For example, the receptacle internal peripheral wall may be shaped to define a receptacle compartment for receiving a connector head having a rounded free end, such as a rounded free end having the shape of a spherical cap, having a bulb shape or having the shape of a boss. In some embodiments, the receptacle internal peripheral wall is shaped to receive a protrusion member having cylindrical body, or a cylindrical body having a narrowed base portion defined by a periphery extending groove or channel. [0036] For a coupling receptacle which is a counterpart connection member of a pair of counterpart connection members and which shares a common centreline with a counterpart and matched protrusion member, the axial directions of the counterpart connection members are aligned and opposite.

[0037] An end aperture is formed on the second axial end of the coupling receptacle and is on the centreline of the coupling receptacle. The end aperture is defined by an axial end portion receptacle internal peripheral wall. The receptacle body tapers to narrow as it extends towards the second axial end so that the end aperture is substantially smaller than the end aperture on the second axial end of the coupling receptacle. A tubular portion is formed at the second axial end of the coupling receptacle and projects away from the coupling receptacle in the second axial direction to extend towards the tubular member.

[0038] The tubular portion extends between a first tubular end which is on the receptacle body and a second tubular end which is a free end proximal to the tubular member. The tubular axes of the tubular member and the tubular portion are aligned. The end aperture on the protrusion member, the tubular member, the tubular portion and the end aperture on the coupling receptacle cooperate to define a through-passageway which extends through the building block. The end aperture on the protrusion member and the end aperture on the coupling receptacle define the longitudinal ends of the thro ugh -passageway.

[0039] An example building block 200 depicted in Figure 2 comprises a building block 100 of Figure 1 A with built-in electrical devices. A plurality of conductive terminals is formed on the protrusion members, as depicted in Figure 2. Each conductive terminal comprises a protruding conductor 250 which protrudes from the axial free end of the protrusion member and through the end aperture under spring 260 bias. The protruding conductor 250, for example, a rigid copper pin, is to retract into the protruding body when an axial retraction force is applied to retract the protruding conductor. While the protruding conductor is retractable, the spring 260 urge force on the protruding conductor should be sufficient to form an effective electrical contact when encountering a counterpart conductive terminal.

[0040] A plurality of conductive terminals, for example naked or exposed electrical contact terminals, is formed on the coupling receptacles. Each conductive terminal comprises a conductive contact such as a conductive pad. The conductive contact is formed on the second axial end of the receptacle compartment which is distal to the entry aperture to the receptacle compartment. The conductive terminals on connection members of a pair of centreline aligned connection members or a pair of counterpart connection members are electrically connected, for example, by a conductive wire 270. [0041 ] In some embodiments, the conductive terminals on the connection members of a pair of centreline aligned connection members or a pair of counterpart connection members which are electrically connected may be electrical polarity bearing. For example, a pair of centreline aligned connection members or a pair of counterpart connection members may be connected to a first terminal of an electrical device or a first terminal of a power supply bearing a first electrical polarity, and another pair of centreline aligned connection members or another pair of counterpart connection members may be connected to a second terminal of the electrical device or a second terminal of the power supply bearing a second electrical polarity opposite to the first polarity.

[0042] In some embodiments, a plurality of conductive terminals is formed on the receptacle body, as depicted in Figures 2A and 2A2. Each conductive terminal comprises a protruding conductor 350 which protrudes from the axial free end of the receptacle body and through the end aperture under spring 360 bias. The spring 360 urge force on the protruding conductor to form an effective electrical contact when encountering a counterpart conductive terminal on the protrusion member.

[0043] Where the conductive terminals are electrical polarity bearing, and a plurality of more than two conductive terminals is formed and on a corresponding plurality of connection members on a base surface, adjacent conductive terminals are arranged to have opposite or different electrical polarity bearing.

[0044] Where the conductive terminals are electrical polarity bearing, and a plurality of four or more than four conductive terminals is formed on a base surface and on a corresponding plurality of connection members such that the conductive terminals are disposed in symmetry about a diagonal line of symmetry, conductive terminals on opposite sides of the diagonal of symmetry are arranged to have the same electrical polarity bearing, and adjacent conductive terminals one the diagonal of lateral symmetry have opposite or different electrical polarity bearing.

[0045] When a plurality of building blocks having corresponding and matched electrical arrangements are stacked connected to form a building block assembly, conductive terminals on adjacently stacked building blocks are electrically connected and an electrical circuit is formed in the building block assembly. Example of such a building block assembly is shown in Figure 3 and Figure 4.

[0046] In some embodiments, conductive terminals are only formed on the first surface or are only formed on the second surface, or conductive terminals formed on different base surfaces are not electrically connected to have the same electrical polarity bearing. For example, where the building block is to function only as a power supply block, the battery terminals may be connected to conductive terminals on a single base surface or both bases surfaces. On the other hand, if the building block is to function as an inter-block electrical connector, a pair of centreline aligned connection members or a pair counterpart connection members would be connected to have the same electrical polarity bearing.

[0047] In some embodiments, the tubular members and/or the tubular portions and/or the through-passageway may function as guides. For example, integral electrical conductors, light conductors or light emitting sticks may extend through through-passageways formed by a plurality of stacked building blocks.

[0048] In some embodiments, a motor and a gear train is built into the building block so that the motor can be operated by power coming from a power source block. A power source block may contain a battery, for example, a rechargeable battery with a battery charging circuit, with the battery and battery charging circuits connected to the conductive terminals for power input and/or output.

[0049] Example variations of the example building block Figures 2A are depicted schematically in Figure 2A1 , 2B and 2B1 . Figure 2B1 is a schematic view of another example building block.

[0050] Referring to Figures 5A, 5B and 5C, an example building block 100' having features which are identical to the building block 100 of Figure 1 A, except for the tubular portions, electrical arrangements and a top aperture on the hollow shell member. The example building block 100, 100' comprises a first panel member 120, a second panel member 140 and a block peripheral member 160 which cooperate to define a main block body 180. A plurality of first connection members 122 is formed on the first panel member 120 to collectively define a first coupling portion, a plurality of second connection members 142 is formed on the second panel member 140 to collectively define a second coupling portion, and the block peripheral member 160 defines a lateral peripheral wall of the building block 100, 100'. A panel member 120, 140 is also referred to as a panel member or a surface bearing member herein, since it also defines the inward/outward or the upward/downward facing surfaces. The panel member 120, 140 is formed of a rigid material such as hard plastics or metal which has a high rigidity and a very small elasticity and is a rigid panel member. A rigid panel member and one or a plurality of connection members integrally formed on the rigid panel member collectively define a panel member connector bearing panel member.

[0051 ] The first connection member 122 is configured for making coupled engagement with a counterpart and matched connection member and is to enter into the coupled engagement in a first coupling direction. The second connection member 142 is configured for making coupled engagement with a counterpart and matched connection member and is to enter into the coupled engagement in a second coupling direction.

[0052] The main body 180 is a shell-like structure comprising a hollow body which defines a hollow internal block compartment 190, as depicted in Figure 5D. Each of the first panel member 120, the second panel member 140 and the block peripheral member 160 is a sheetlike member ( or "sheet member" in short) or a plate-like member (or "plate member" in short) having a thickness which is substantially smaller than the thickness of the building block, the thickness of the building block being measured in a direction orthogonal to the line X-X' of Figure 5 between the outward facing surface 1201 (or the upward facing surface in the normal orientation of Figure 5D) of the first panel member 120 and the outward facing surface 1401 (or the downward facing surface in the normal orientation of Figure 5D) of the second panel member 140.

[0053] The hollow internal block compartment 190 defines an internal cavity which extends axially between the first panel member 120 and the second panel member 140 and delimited laterally by the block peripheral member 160. Axial clearance of the internal cavity, as defined by the axial separation distance between the inward facing surface 1202 (downward facing in the normal orientation of Figure 5D) of the first panel member 120 and the inward facing surface 1402 (or upward facing in the normal orientation of Figure 5D) of the second panel member 140, is substantially larger than the sheet thickness or plate thickness of the individual panel members 120, 140 and/or the block peripheral member 160. The axial clearance of the internal cavity is substantially equal to the height of the block peripheral member 160 minus the aggregated thickness of the first panel member 120 and the second panel member 140. The height of the block peripheral member 160 is defined in an axial direction A-A', B-B' which is orthogonal to the first panel member 120 and/or the second panel member 140 and the thickness of the block peripheral member 160 is measured in a transverse direction which is orthogonal to the axial direction. A panel member 120, 140 is also referred to as a panel member or a surface bearing member herein, since it also defines the inward/outward or the upward/downward facing surfaces.

[0054] The connection member 122, 142 comprises a hollow shell body as an example of a shell-like structure. The hollow shell body is defined by a rigid shell member which projects axially from the panel member 120, 140 and extends in both the axial and transverse directions to define a rigid structure. The hollow shell body defines a connector main body, a connector internal cavity and a hollow connector compartment inside the connector main body. The hollow shell body is defined by a sheet-like member or a plate-like member shell member. A sheet-like member or the plate-like member herein has a first surface and a second surface. The first surface and the surface are parallel and thickness of the shell member is defined by the separation distance, that is orthogonal distance, between the first surface and the surface. For the example first connection member 122, the first surface is an outer peripheral surface of the connection member 122 defining the outer profile of the connection member 122, and the second surface is an inner peripheral surface of the connection member 122 defining the internal profile of the connection member 122 or boundary of the connector internal cavity. For the example connection member 122, 142 the first surface is an outer peripheral surface of the connection member 122,142 defining the outer profile of the connection member 122, 142, and the second surface is an inner peripheral surface of the connection member 122, 142 defining the shape or boundary of the connector internal cavity. The internal cavity of the first connection member 122, which is inside and defined by the shell body of the first connection member 122, is in communication with the internal cavity of the internal block compartment 190 and the communication is facilitated by means of a through aperture formed on the first panel member 120. The portion of the first panel member 120 which defines the through aperture also defines a through passageway, through which the internal cavity inside the connection member 122 and the internal block compartment 190 are in communication. This through aperture, which is formed on the first panel member 120, is an intermediate aperture which interconnects the internal block compartment 190 and the internal cavity inside the first connection member 122.

[0055] The internal cavity of the second connection member 142, which is inside and defined by the shell body of the second connection member 142, is open to the outside (that is, exterior to the main body 180) by means of a through aperture which is formed on the second panel member 140. The portion of the second panel member 140 which defines the through aperture also defines a through passageway through which an external protrusion member can move into the internal cavity and then received or retained by the internal cavity . This through aperture, which is formed on the second panel member 140, is an intermediate aperture which interconnects the internal cavity of the second connection member 142 and the exterior.

[0056] The hollow shell body of the connection member 122, 142 is integrally formed on or with the panel member 120, 140 and the hollow shell body joins the panel member 120, 140 at the periphery of the intermediate aperture so that the inner peripheral surface of the hollow shell body is a smooth continuation from the inner peripheral surface defining the intermediate aperture, for example, with seamless or non-salient transition between the surfaces.

[0057] The first connection members 122 are integrally formed on or integrally formed with the first panel member 120 and the second connection members 142 are integrally formed on or integrally formed with the second panel member 140. [0058] Where there is a plurality of connection members formed on a panel member 120, 140, a corresponding plurality of associated intermediate apertures is also defined on the panel member 120, 140

[0059] In some embodiments, the first connection members 122, the first panel member 120 and the block peripheral member 160 are integrally formed as a single first integral piece; the second connection members 142 and the second panel member 140 are integrally formed as a single second integral piece; and the building block is formed by joining the first and second integral pieces together. More specifically, the second integral piece is joined to the bottom end of the block peripheral member 160 which is an axial end of the block peripheral member 160 most distal to the first panel member 120.

[0060] In some embodiments, the first connection members 122 and the first panel member 120 are integrally formed as a single first integral piece; the second connection members 142, the second panel member 140 and the block peripheral member 160 are integrally formed as a single second integral piece; and the building block is formed by joining the first and second integral pieces together. More specifically, by joining the first integral piece to the top end of the block peripheral member 160 which is an axial end of the block peripheral member 160 most distal to the second panel member 140.

[0061 ] In example embodiments, the components of the building block are made of structural materials such as hard and/or rigid plastics, for example, ABS (acrylonitrile butadiene styrene) or PC (polycarbonate), or metal for use in structures such as steel, aluminium or aluminium alloys and are joined by gluing, welding or other appropriate known joining methods available.

[0062] The first panel member 120 and the second panel member 140 are parallel and are spaced apart, separated by the internal cavity of the internal block compartment (or "compartment internal cavity"). The first coupling direction and the second coupling direction are parallel to the axial direction and the axial centrelines of the connection members are parallel. The axial centreline of a connection member herein is a centreline about which the connection member is laterally or circularly symmetrical.

[0063] An example plurality of four first connection members 122 is formed on the first panel member 120 and an example plurality of four second connection members 142 is formed on the second panel member 140. The connection members 122, 142 are distributed in a regular matrix such that the separation distance between adjacent connection members along a row or along a column on the same panel member is the same. The separation distance between adjacent connection members is conveniently taken as the distance between the axial centrelines of the adjacent connection members for sake of simplicity. [0064] The connection members 122, 142 on the first panel members 120 and the second panel member 140 are centreline aligned such that for a first connection member 122 on the first panel member 120 there is a corresponding centreline aligned second connection member 142 on the second panel member 140.

[0065] In the example building block of Figure 5A, the connection members 122 on the first panel member 120 are connection members of a first type and the connection members 142 on the second panel member 140 are connection member of a second type. A connection member of the first type herein is also referred to as a male-type or a protrusion-type connection member, and a connection member of the second type herein is also referred a female-type or a receptacle-type connection member. A connection member of the first type has opposite mechanical mating properties to a connection member of a second type.

[0066] The example first connection member 122 and the example second connection member 142 are matched and compatible connection members. A pair of matched and compatible connection members is one which comprises component connection members and the component connection members have mechanical mating features which are opposite, complementary and dimensions matched. The component connection members, when formed on separate carriers, are to enter into coupled engagement (which means coupled mechanical engagement, snap engagement, or snap latching) when the component connection members are relatively moved along a coupling direction and pressed together.

[0067] The hollow shell body of the first connection member 122 projects axially away from the main body 180 (and away from the second panel member 140) and the centreline of the first connection member 122 is orthogonal to the outward or upward facing surface 1201 of the first panel member 120. The hollow shell body of the second connection member 142 projects axially away from the second panel member 140 and projects into the internal block compartment 190, and the centreline of the second connection member 142 is orthogonal to the outward or downward facing surface 1401 of the second panel member 140.

[0068] The hollow shell member of a connection member 122, 142 has an arcuate or curved cross sectional profile and the rigid shell spans or extends across the through aperture on the panel member 120, 140. An arcuate or curve shaped shell member which spans or extends across the bridging apertures forms a spanning structure which provides structural reinforcement or supplemental structural reinforcement to compensate for structural weakness on the panel member 120, 140 due to formation of the bridging apertures thereon.

[0069] In example embodiments, the hollow shell member is arc-shaped, arch-shaped, dome- shaped, cap-shaped, egg shell shaped, or has an arc-shaped, arch-shaped, dome-shaped, cap-shaped, and/or egg-shell shaped top or top structure, and the arcuate or curved upper or top portions of the hollow shell member extends radially, in more than one transverse directions or a plurality of transverse directions orthogonal to the axial direction, and spans across the intermediate aperture as a spanning structure. A shell-like spanning structure having an arc-shaped or arch-shaped cap-shaped top or top structure which spans across an intermediate aperture on the panel member 120, 140 provides structural reinforcement to the panel member 120, 140 in the direction of extension of the arc or arch. A shell-like structure having a dome-shaped, cap-shaped, or egg-shell-shaped top structure when spanning across an intermediate aperture on the panel member 120, 140 provides radial or multi-directional structural reinforcement to the panel member 120, 140 in the directions of extension of the dome, cap, or egg-shell. In such embodiments, the connection member provides structure reinforcement to the associated panel member 120, 140 while at the same time defining a connection member and its associated features such as the internal cavity and the bridging aperture.

[0070] The shell-like structure or the hollow shell member may be in the form of a continuous smooth shell, a gridded or textured shell, or in the form of a grid-like structure, a net-like structure, a grille-like structure, or a web-like structure without loss of generality.

[0071 ] In some embodiments, including the example of Figures 5A to 5D, the hollow shell member comprises an upper portion (or first portion) defining an end cap at the axial free end of the hollow shell member and a lower portion (or second portion) which extends between the end cap and lower surface, that is the downward facing surface 1401 of the panel member.

[0072] In some embodiments, a through aperture may be formed on the end cap or the centre of the hollow shell member, the centre being where the centreline of the hollow shell member passes.

[0073] In some embodiments, such as the example embodiment of Figure 5A, the hollow shell member of the first connection member 122 defines a protrusion member which is closely matched with a receptacle defined by the hollow shell member of the second connection member 142.

[0074] The connection member 122, 142 projects above the base panel member 120, 140 by an axial height which is substantially larger than the thickness of the base panel member 120, 140. In example embodiments, the axial height is 3 to 10 times or more (including 3, 4, 5, 6, 7, 8, 9, 10, or any range or ranges formed by combination of the aforesaid values) the thickness of the base panel member 120, 140. A base panel member 120, 140 herein means the panel member 120, 140 from which a surface of which the connection member 122, 142 projects or extends. In example embodiments for tor application as toy building blocks, the thickness of the panel member 120, 140 or the block peripheral wall 160 may be in the region of 0.5mm to 2mm, (including 0.5, 0.6, 0.7, 0.8, 0.9, 1 .0. 1 .1 , 1 .2, 1 .3, 1 .4, 1 .5, 1 .6, 1 .7, 1 .8, 1 .9, 2.0, or any range or ranges formed by combination of the aforesaid values). In other applications, such as industrial applications, the thickness would be substantially higher, for example, 3 to10 times of that for toy applications (including 3, 4, 5, 6, 7, 8, 9, 10, or any range or ranges formed by combination of the aforesaid values) to provide sufficient structural strength and rigidity as required or appropriate.

[0075] In the example of Figure 5A, the four example connection members 122, 142 are distributed in a square matrix of two rows by two columns, each of the panel members 120, 140 is substantially square, and the block peripheral member extends in an axial direction to interconnect the first and second panel members 120, 140, and extends transversely to surround the first and second panel members 120, 140.

[0076] The connection members may be distributed in any desirable order or configuration. In typical examples, the connection members are distributed in a matrix comprising N rows and M columns, N, M being an integer, where separation distance between adjacent rows and adjacent columns are equal and uniform. In some embodiments, the connection members are distributed in a circular matrix comprising N circular rows, where separation distance between adjacent rows and adjacent connection members are equal and uniform. For example, the connection members may be arranged in a square matrix of 3x3 (i.e., three rows and three columns), 4x4, 5x5, 6x6, etc.; rectangular matrixed of 2x3, 2x4, 2x5, 2x6, 3x4, 3x5, 3x6, 3x7, 4x5, 4x6, 4x7, circular matrixes of two, three, four, five etc. concentric rows (or rings) having uniform or non-uniform spacing.

[0077] In some embodiments, the spanning structure extends radially from the connection member and/or passes through the centreline of the connection member.

[0078] In some embodiments, the spanning structure is laterally, circularly or radially symmetrical about the centreline of the connection member.

[0079] A connection member having a substantially hollow interior which is defined by a hollow shell member that spans across the bridging aperture as a spanning structure provides structural reinforcement to strengthen the panel member while also functioning as a connection member for making mechanical detachable engagement with a matched and complementary counterpart and possessing the benefits of light weight due to being hollow or being substantial hollow.

[0080] In some embodiments, the volume of the internal cavity of the connection member 122, 142 (excluding the tubular portions of Figures 1 C and 1 D) accounts for between 40% to 90% (including 40% or more, 45% or more, 50% or more, 55% or more, 60% or more, 65% or more, 70% or more, 75% or more, 80% or more, 85% or more, 90% or less, or any range or ranges select from a combination of the aforesaid values or range or ranges) of the volume of the connection member. In other words, the connection member 122, 142 is between 40% to 90% hollow or unfilled.

[0081 ] The hollow shell member of a connection member 122, 142 comprises an internal peripheral wall and an external peripheral wall. The internal cavity of the connection member 122, 142 is defined by the internal peripheral wall of the hollow shell member.

[0082] In some embodiments, the internal peripheral wall of the hollow shell member has a dome-shaped, curved or arcuate downward facing ceiling portion to provide material effective structural strengthening, the ceiling being an inner facing surface of the end cap.

[0083] In some embodiments, the internal peripheral wall of the hollow shell member of a connection member defines a receptacle for closely fitted reception of a protrusion portion of a matched counterpart protrusion member of a counterpart connection member having a free or top axial end in the shape of a spherical cap or a spherical segment when the connection member and the counterpart connection member are in mechanical engagement, for example, in snap-fit engagement. When in said mechanical engagement, the downward facing curved or arcuate shaped ceiling portion of the hollow shell member will be in abutment contact and engagement with the upward facing surface of the free or top axial end of the corresponding or counterpart protrusion member. In preferred embodiments, the area in abutment contact would be at least 40% of the area of the curved or arcuate shaped ceiling portion, including more than 40%, 45% or more or less, 50% or more or less, 55% or more or less, 60% or more or less, 65% or more or less, 70% or more or less, 75% or more or less, 80% or more or less, 85% or more or less, 90% or more or less, 95% or more or less, 100% or less, or any range or ranges select from a combination of the aforesaid values or range or ranges).

[0084] In some embodiments, the portion of the internal peripheral wall of the hollow shell member which is in abutment with the portion of the panel member delimiting the bridging apertures extends in the axial direction to define a tubular portion.

[0085] In some embodiments, the shell forming the hollow shell member has a shell thickness which is comparable to, or smaller (for example slightly smaller) than the thickness of the panel member or the block peripheral member. In some embodiments, the shell thickness is substantially uniform.

[0086] The panel member may have other shapes such as geometrical shapes, for example, circular, elliptical or polygonal, or non-geometric shapes without loss of generality.

[0087] An example building block assembly 10 depicted in Figure 5A1 comprises an aggregate of a first building block 100A and a second building block100B in stacked engagement. Each of the building blocks 100A and 100B is identical to the building block 100 and the descriptions thereon are incorporated by reference for the benefit of succinctness with the same numerals applied with suffixes a or b optionally appended to correspond respectively with the building blocks 100A and 100B where appropriate.

[0088] The second building block 100B is stacked on the first building block 100A to form a stacked aggregate of connected or interconnected building blocks so that the first building block 100A and the second building block 100B are in a stack engaged configuration. When in this stacked engaged configuration, the first coupling portion which is defined by the ensemble of the first connection members 122A of the first building block 100A is in mechanical engagement with the second coupling portion which is defined by the ensemble of the second connection members 142B of the second building block 100B, and the downward facing surface of the second panel member 140B of the second the second building block 100B is in abutment contact with the upward facing surface of the first panel member 140A of the first building block 100A. When in this mechanical engagement relationship, the protrusion portions of the first connection members 122A which project above the first panel member are received in the receptacles which are defined by the corresponding second connection members 142B and are received in a closely fitted or interference fitted manner.

[0089] As a hollow shell member of the first connection member 122A, 122B defines a protrusion member which is closely matched with a receptacle which is defined by the hollow shell member of the second connection member 142A, 142B, the protrusion member of the first connection member 122A on the first building block 100A is substantially wrapped around by the inside surface or the downward facing surface of the hollow shell member of the second connection member 142B of the second building block 100B when the protrusion member and the receptacle member are in mechanical engagement when in the mechanical engagement relationship.

[0090] More specifically, the downward facing surface and the laterally facing surface of the hollow shell body of the second connection member 142B of the second building block 100B is in abutment contact with the upward facing surface and the laterally facing surface of the hollow shell body of the first connection member 122A of the first building block 100A. In other words, the corresponding hollow shell members of the corresponding first and second connection member 122A, 142B are in closely fitted and stacked abutment contact when in this stack engaged configuration. As the corresponding hollow shell members of the corresponding first and second connection member 122A, 142B are arcuate and in closely fitted abutment contact, the mechanical engagement between the corresponding coupling portions provides supplemental structural reinforcement to the assembly as the two engaging hollow shell members would function as a stronger or double arcuate reinforcement structure. Connection member of the first type

[0091 ] An example connection member of the first type comprises a protrusion member 122 which projects away from a base surface and extends in an axial direction (A-A' of Figure 5E) away from the base surface which is the upward facing surface 1201 of the first panel member 120 in this example. The protrusion member comprises a head portion 126 having a free axial end and a neck portion 128 which is intermediate the head portion 126 and the base surface 1201 . The neck portion 128 extends between the head portion 126 and the base surface 1201 and projects axially away from the base surface 1201 . The free axial end of the head portion 126 is a rounded end having a dome-shaped or arcuate top which is distal to the base surface 1201 and the head portion has a second end which is distal to the rounded end and proximal to the base surface 1201 and is in abutment connection with the neck portion 128. A connection member of the first type has male type mating features and properties and is also referred to herein as a "male type connector", a male type connector member or a male connector in short where the context requires or is appropriate^

[0092] In some embodiments, including that of Figure 5A, the connection members are adapted for snap-fit engagement, so that a connection member of the first type is a male-type snap connector, a connection member of the second type is a female-type snap connector, and a pair of snap connectors comprising a male-type snap connector and a correspondingly shaped and sized matched female connector are in snap-fit engagement (or "coupled engagement") when the counterpart male and female connectors are snap-fitted together.

[0093] The neck portion 128 of a male type snap connector diverges or flares to expand (at least initially) as it departs or projects axially away from an axial end which is in abutment with the base surface 1201 , and then joins the head portion at its distal axial end which is distal to the base surface 1201. The neck portion 128 ceases to diverge and/or begins to taper or converge at its distal axial end meets or joins the head portion 126. A narrowed region is formed around the base of the neck portion which is immediately adjacent the base surface 1201 due to the initial divergence or flaring of the neck portion. The initial divergence or flaring of the neck portion can be viewed as a finishing convergence or tapering when progress is considered or viewed in the opposite axial direction. When so considered or viewed, the head portion tapers or converge gradually to narrow as it extends axially towards the base surface. The narrowed region defines a retention region which extends around the outer periphery of the base portion of the neck portion. The retention region is configured to cooperate with an anchoring device on a counterpart and matched connection member to form a coupled mechanical or anchored engagement. [0094] In some embodiments, including the example of Figure 5A, the maximum transverse dimensions of the protrusion member occur at where the neck portion abuts the head portion. The head portion gradually converges or tapers to narrow as it extends away from the neck portion and the base surface until reaching its free axial end. The head portion may have a hemispherical shape as in this example, but may have a truncated end or may be in the form of a spherical frustum. The example head portion follows the surface curvature of a defining sphere and an example defining sphere is one which is defined by a circle having circular dimensions of the maximum transverse dimensions of the protrusion member. Where the head portion has a truncated end or frustum free end, the free axial end of the head portion may have a chamfered periphery so that a transversely extending a top shell portion of the hollow shell member is joined to an axially extending peripheral shell portion of the hollow shell member to provide more effective structural reinforcement in the transversal direction.

[0095] Referring to Figure 5D, the protrusion member 122 comprises, on progressing along an axis of circular symmetry A-A', a base portion or a neck portion 128 having a base end which is proximal or in abutment with the base surface 1201 , a head portion 126 which is distal from the base surface 1201 defining a free end and a free end portion, and a middle portion which is intermediate the base surface 1201 and the head portion. The middle portion is a bulged junction portion where the maximum transversal dimensions of the protrusion member 122 occurs. The neck portion 128 tapers or converge to narrow as it extends towards its base end along the axis of circular symmetry and following a spherical curvature. The head portion tapers or converge to narrow as it extends from its free end towards the base end and the middle portion following a spherical curvature, which is the same spherical curvature as that of the neck portion.

[0096] In a different perspective, the neck portion flares or diverge to widen as it extends away from the base end along the axis of circular symmetry following a spherical curvature, and the head portion flares or diverge to widen as it extends towards the base end and the middle portion following the same spherical curvature.

[0097] In some embodiments, the protruding member has the shape of a spherical frustum and has a depth or height H in an axial direction, the axial direction being a direction extending along the axis of circular symmetry, and comprises a first spherical frustum having a depth hi , a second spherical frustum having a depth h2, and a middle plane defining the middle portion which is intermediate the first and second spherical frustum, where H=h1 +h2. Referring to Figures 5A and 5D, hi is the axial height of the head portion 126 and h2 is the axial height of the neck portion 128. In general, the value of hi and h2 can be between zero and R1 , where R1 is the radius of a circular plane at the maximum transversal span of the protrusion member. Where hi equals R1 , the head portion 126 is hemispherical, as in the case of Figure 5A. Where h2 is zero, the height of the protruding member is equal to the height of the head portion.

[0098] In example embodiments, hi is in the region of 0%-100% of R1 , for example, 0%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100% and/or any range or ranges selected from the aforesaid values, and the values of h2 are in the same or similar range but H must be smaller than D1 which is equal to 2R1 . For example, H may be in the region of 25-85% of D1 , for example, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, and/or any range or ranges selected from the aforesaid values. A preferred range of h2 is between 20%-40% for making effective snap-fit engagement with wedging.

[0099] The value of h2, which equals the axial extent of a neck portion, may be determined with reference to the strength rigidity and resilience of the materials of the protrusion member and/or the counterpart engagement member to be coupled with the protrusion member without loss of generality.

[0100] The protrusion member tapers to join the base surface at an acute angle to define a retention region at the base of the protrusion member. In some embodiments, the protrusion member curves convexly to converge towards the centreline and joins the base surface at an acute angle.

[0101 ] In some embodiments, including the example of Figure 5A, the protrusion member has a convexly curved base portion which is oppositely facing the base surface, and the convexly curved base portion of the protrusion member cooperates with the base surface to form a peripherally extending base wedging portion. The protrusion member curves convexly on projecting away from the base surface to cooperate with the base surface to define a tapered or narrowed retention region, the narrowed region is to function as a wedging portion for entering into wedging engagement with a corresponding anchoring portion of a counterpart and matched snap connector. The wedging portion progressively narrows, converges or tapers to narrow in a radial direction towards the centreline of the protrusion member as it extends in the axial direction towards the base surface. The axial end of the convexly curved portion which is proximal the base surface makes an acute angle with the base surface, in other word, it joins the base surface at an acute angle.

[0102] The acute joining angle may be between 20 degrees to 85 degrees, for example, the joining angle may be 20 degrees or more, 25 degrees or more or less, 30 degrees or more or less, 35 degrees or more or less, 40 degrees or more or less, 45 degrees or more or less, 50 degrees or more or less, 55 degrees or more or less, 60 degrees or more or less, 65 degrees or more or less, 70 degrees or more or less, 75 degrees or more or less, 80 degrees or more or less, or 85 degrees or less, or a range defined by a combination of any of the aforesaid values and/or ranges. An example preferred range is 30 to 60 degrees. The joining angle is between 5 degrees to 70 degrees to the centreline, and the aforesaid angular values are each to be minus by 90 degrees if the joining angle is with reference to the centreline or axial line.

[0103] In some embodiments, the convexly curved base wedging portion extends from its base to reach a maximum transversal span at axial distance from the base, the transversal span being defined in a transversal direction which is orthogonal to the axial direction, and wherein the axial distance is ad1 % of a transversal width D1 at the maximum transversal span, ad1 being between 10% to 45% of D1 , including 10% or more, 15%or more or less, 20%or more or less, 25%or more or less, 30%or more or less, 35%or more or less, 40%or more or less, 45 % or less, or any range or ranges defined by any combination of the aforesaid values, range or ranges.

[0104] In some embodiments, the convexly curved based wedging portion extends from an initial transversal span at its base end to reach a maximum transversal span at an axial level from the base surface, the transversal span being defined in a transversal direction which is also the radial direction that is orthogonal to the axial direction. The initial transversal span is ts2% of the maximum transversal span D1 , and ts2 is between 55% to 95% of D1 , including 55% or more, 60% or more or less, 65% or more or less, 70% or more or less, 75% or more or less, 80% or more or less, 85% or more or less, 90% or more or less, 95% or less, or any range or ranges defined by any combination of the aforesaid values, range or ranges.

[0105] In some embodiments, the base of the convexly curved portion is on the base surface or at an axial distance from the base surface.

[0106] In some embodiments, the neck portion has the curved peripheral surface of a lower spherical segment of a sphere S having a spherical radius SR and an axial height of ah1. A lower spherical segment herein being a spherical segment which extends for the axial height ah1 from a transversal plane of the sphere having a maximum transversal span, the axial height being measured in an axial direction parallel to the axis of circular symmetry of the spherical segment and the maximum transversal plane being a circular plane defined by SR. The transversal span of the neck portion, defined by a transversal plane which is orthogonal to the axial direction, progressively reduces on approaching the base surface so that the outer peripheral surface at or near the base end of the neck portion follows a convex curvature and forms an acute angle with the base surface, the base end of the neck portion being in abutment with on approaches the base surface.

[0107] In some embodiments, the neck portion is a cylindrical body or a prismatic body which projects away from the base surface, and a tapered portion is formed at a peripheral region in abutment with or in proximity to the base surface. The tapered portion defines a peripheral depression or a peripheral recess which extends around the outer periphery of the neck portion and forms a retention groove or a retention channel as an example of a retention device or a wedging device. Where the tapered portion is in abutment with the base surface, the periphery of the neck portion defining the tapered portion defines the initial or narrowest transversal span of the neck portion on the base surface. Where the protrusion member is circularly symmetrical, the initial transversal span defines a circular plane which is orthogonal to the axial direction.

[0108] In some embodiments, the protrusion member defines a first circular plane which is parallel to the first surface and orthogonal to a centre axis defined by the centreline at where the protrusion member meets the base surface and having a first radius r1 , the protrusion member flares outwardly as it projects axially away from the first surface and defines a second circular plane which is parallel to the first circular plane and at an axial height away from the first surface and having a second radius r2, the second radius being larger than the first radius and the first radius r1 is between 55% to 95% of SR, including 55% or more, 60% or more or less, 65% or more or less, 70% or more or less, 75% or more or less, 80% or more or less, 85% or more or less, 90% or more or less, 95% or less,, or any range or ranges defined by any combination of the aforesaid values, range or ranges .

[0109] The head portion continues from the neck portion and extends away from the neck portion in the axial direction and has the shape of a second spherical segment. The second spherical segment has an axial height ah2 which is defined between a second circular plane having a second radius r2 and a third circular plane which is axially spaced apart from the second circular plane and has a third radius r3, the third radius being smaller than the second radius r2.

[01 10] As the head portion extends axially away from the base surface or the neck portion, its transversal span gradually decreases and the rate of decrease gradually increases so that an outer side of the head portion is also convexly curved when viewed in the transversal direction. The head portion is laterally symmetrical about the centreline and, in some embodiments, the outside of the head portion follows the curvature of a sphere as it extends axially away from the neck portion. In a longitudinal cross-sectional view taken along the centreline, two mirror symmetrical arcuate portions are disposed on two diametrically opposite ends of the neck portion at the same axial level, as the head portion is laterally or circularly symmetrical about the centreline. Each of the convex sides has its convex surface facing away from the centreline or facing outwards. [01 1 1 ] In some embodiments, the head portion converges to a rounded end at its free axial end. The rounded end may be a spherical segment of a sphere.

[01 12] In some embodiments, the second radius r2 is the radius of a sphere and the head portion follows the curvature of the sphere to converge to form a free rounded end.

[01 13] In some embodiments, the neck portion diverges in the transversal direction or flares as it extends axially away from the base surface until reaching a maximum transversal span at its axial end. The head portion then continues from the maximum transversal span at the axial end of the neck portion and tapers to converge at its axial free end as it extends in the axial direction.

[01 14] A head portion which flares to expand its transversal span as it extends in an axial direction towards the base surface or towards the retention device facilitates easier or more convenient coupling insertion of a counterpart engagement device towards the retention device. A head portion that has a smaller transversal span at its axial free end would facilitate more convenient alignment with a retention or engagement device of a counterpart connection member.

[01 15] A neck portion having a retention device which flares to expand its transversal span as it extends in an axial direction away from the base surface or towards the head portion facilitates more effective retention of a retention or engagement device of a counterpart connection member. The continuity in transversal span at the junction of the head and neck portion facilitates easy movement across the junction.

[01 16] In some embodiments, the head portion is a spherical segment having a truncated free end. In some embodiments, the head portion is a rounded end or a spherical cap.

[01 17] In some embodiments, there is a continuity of curvature on transitioning from the neck portion to the head portion or on transitioning from the head portion to the neck portion.

[01 18] In some embodiments, the head portion and the neck portion have different curvatures.

[01 19] To form a matched pair of counterpart connection members, a counterpart connection member would have features which are opposite and complementary to that of the connection member of the first type and in matching correspondence in feature sizes, shapes and dimensions.

[0120] The protrusion member may have a circular symmetry or is circularly symmetrical about a centre axis to facilitate coupling in different angular orientations about the centre axis. [0121 ] In embodiments where the protrusion member or a portion of the protrusion member is in the shape of a spherical segment or a spherical cap, the centre axis of the protrusion member is coaxial with the centre axis of the spherical segment or the spherical cap.

[0122] In embodiments where the protrusion member has a convexly curved peripheral profile which extends across and about the maximum transversal span, the protrusion member has a bulging profile about the maximum transversal span.

[0123] In some embodiments, the protrusion member flares away from the base surface and extends along a linear path to form a frusto-conical neck portion or extends along a convex path to form a neck portion in the shape of a spherical segment.

[0124] In some embodiments, the protrusion member flares to reach a maximum transversal span, and the maximum transversal span is defined by a circular plane defining a sphere of the spherical segment and then tapers to reduce its cross-sectional area as it extends axially away from a height of the maximum cross-sectional area.

[0125] In some embodiments, the protrusion member flares to reach a maximum cross- sectional area and then tapers to reduce its cross-sectional area as it extends axially away from a height of the maximum cross-sectional area.

[0126] In some embodiments, the connection members are adapted for interference-fit engagement or interference-fit in short, wherein a connection member of the first type is a male-type interference connector, a connection member of the second type is a female-type interference connector, and a pair of interference connectors comprising a male-type interference connector and a correspondingly shaped and sized matched female connector are in interference-fit engagement (or "coupled engagement") when the counterpart male and female connectors are interference-fitted together.

[0127] In example embodiments where the connection member of the first type is a male-type interference connector, the protrusion member comprises a substantially cylindrical or prismatic body, or a frusto-conical body which tapers monotonously to narrow as it extends away from the base surface.

[0128] In some embodiments, including the example of Figures 5A and 5E, the connection members are adapted for both interference-fit and snap-fit engagement, so that a connection member of the first type is a male-type snap connector, a connection member of the second type is a female-type snap connector, and a pair of snap connectors comprising a male-type snap connector and a correspondingly shaped and sized matched female connector are in snap-fit engagement (or "coupled engagement") when the counterpart male and female connectors are snap-fitted together. Connection member of the second type

[0129] A connection member of the second type 142 has female type mating features and properties and is also referred to herein as a "female type connector", a female type connector member or a female connector in short where the context requires or is appropriate.

[0130] An example connection member of the second type comprises a coupling receptacle 146. The coupling receptacle 146, also referred to herein as a connector receptacle, comprises a receptacle body which defines a receptacle compartment. The receptacle compartment is for receiving an engagement portion of a matched counterpart connector of the opposite type, that is, a matched counterpart connection member of the second type. The receptacle body comprises an internal peripheral wall which extends between a first axial level and a second axial level to respectively define a first axial end and a second axial end of the receptacle compartment or the connector receptacle. The axial levels are at different levels along the axial direction and the axial direction is parallel to the centreline B-B' of the connection member and is orthogonal to the base surface. The first axial end of the receptacle compartment is proximal to the base surface and is defined by the first axial end of the internal peripheral wall of the receptacle body. The first axial end of the internal peripheral wall extends in a transversal circuit about a centreline of the coupling receptacle 146 to define an initial transversal clearance. The first axial end or the transversal circuit of the internal peripheral wall at the first axial end defines an entry aperture to the receptacle compartment and has a transversal span which defines an initial transversal clearance of the receptacle body at an entry end. The second axial end of the receptacle compartment is distal to an entry end where the entry aperture is defined. The transversal circuit of the internal peripheral wall at an axial level away from the base surface defines a transversal span at that axial level.

[0131 ] Referring to Figures 1 F and 5A to 5D, the second connection member 142 is a female- type snap connector, and the first axial end of the connector receptacle is at or is flush with the outward or downward facing surface 1401 of the second panel member 140.

[0132] The internal peripheral wall of the coupling receptacle comprises a first peripheral wall portion which is proximal to a downward facing surface 1401 of the surface bearing member 140 and a second peripheral wall portion which is distal to the base surface. The first peripheral wall portion extends in a transversal direction as a transversal circuit. The transversal direction is orthogonal to the axial direction and the axial direction is parallel to the centre line B-B' of the coupling receptacle. The first peripheral wall portion is a up standing wall which projects from a base. The base is joined to the surface bearing member by a bridging portion, with a peripheral groove formed between the first peripheral wall portion and the surface bearing member. [0133] The internal peripheral wall of the coupling receptacle comprises a second peripheral wall portion which defines a receptacle base member. The receptacle base member projects in an axial direction away from the inward facing surface 1402.

[0134] Each of the coupling receptacle, the receptacle body and the receptacle compartment is circularly symmetrical about the centreline to permit relative rotation between the coupling receptacle and a counterpart protrusion member in mated engagement connection therewith, and/or to permit the receiving coupling receptacle to enter into mated engagement connection with a counterpart protrusion member at different relative angular orientations about the centreline. The coupling receptacle has opposite and complementary mating features and properties to a counterpart protrusion member to facilitate mated engagement connection with a counterpart protrusion member.

[0135] The first and second axial ends of the coupling receptacle are on the centreline of the coupling receptacle. The centreline of the coupling receptacle is also the centreline of the receptacle body and the centreline of the receptacle compartment.

[0136] The receptacle body projects away from the base surface and extends along a second axial direction, the second axial direction being parallel to centreline.

[0137] The receptacle internal peripheral wall of the receptacle body is shaped and dimensioned to correspond to the shape and dimensions of a counterpart protrusion member of a counterpart connection member. For example, the receptacle internal peripheral wall may be shaped to define a receptacle compartment for receiving a connector head having a rounded free end, such as a rounded free end having the shape of a spherical cap, having a bulb shape or having the shape of a boss. In some embodiments, the receptacle internal peripheral wall is shaped to receive a protrusion member having spherical frustum body, or a cylindrical body having a narrowed base portion defined by a periphery extending groove or channel.

[0138] In some embodiments, the coupling receptacle compartment comprising the collar compartment and the receptacle base compartment defines a continuous compartment for snap-fitted reception of an engaging portion having the shape of a spherical segment.

[0139] The internal peripheral wall at the first axial end which defines an entry aperture to the receptacle compartment has a transversal span which defines an initial transversal clearance of the receptacle body at an entry end. The transversal circuit of the internal peripheral wall at an axial level away from the base surface defines a transversal span at that axial level.

[0140] The internal peripheral wall (or the receptacle internal wall) flares to expand to increase its transversal span to reach a maximum transversal span as it extends away from the base surface in the axial direction (first axial end) and then tapers to converge to decrease its transversal span as it extends away from the maximum transversal span and towards its second axial end.

[0141 ] In some embodiments, the internal peripheral wall flares or diverges with a constant gradient or along a linear path as it extends away from the base surface to form a frusto- conical engaging portion.

[0142] In some embodiments, the internal peripheral wall tapers or converges to narrow with a constant gradient or along a linear path as it extends away from the maximum transversal span and progress towards the second axial end to form a frusto-conical compartment.

[0143] The second axial end of the receptacle body is a rounded end having an axis of symmetry which is coaxial with the centre axis of the receptacle body. The rounded second axial end defines a receptacle compartment having a dome-shaped or hemispherical distal end.

[0144] The internal peripheral wall flares or expand with an increasing gradient and defines a concave profile as it extends away from the base surface. The radial end of the internal peripheral wall forms a wedging end for engaging with a retention device on a counterpart connection member.

[0145] The internal peripheral wall tapers to narrow with an increasing gradient and defines a concave profile as it extends away from the maximum transversal span to form a rounded axial free end.

[0146] The internal peripheral wall has a concave profile which extends across the maximum transversal span as the internal peripheral wall progresses in the axial direction, the concave profiles on two axial sides of the maximum transversal span cooperate to form a bulging retention compartment which is part of the receptacle compartment.

[0147] The portion of the internal peripheral wall between the base and the maximum transversal span is in the form of a spherical segment and/or has an outer peripheral surface which follows the shape and curvature of the curved surface of a spherical segment.

[0148] The internal peripheral wall has a concavely curved portion which is proximal to the base surface, the convexly curved portion form a peripherally extending wedging portion.

[0149] In embodiments where the coupling receptacle is formed as a depression on a surface defining body, the internal peripheral wall cooperates with the base surface to form a peripherally extending wedging portion. The peripherally extending wedging portion is a wedging portion which progressively narrows, converges or tapers to narrow on extending radial inwards towards an axially extending centreline of the protrusion member. [0150] In embodiments where the internal peripheral wall tapers to narrow as it extends towards the base surface or flares to expand as it extends away from the base surface, the tapered or flaring end of the protrusion member makes an acute angle with the base surface. The acute angle is typically between 20 degrees to 85 degrees, for example, the acute angle may be 20 degrees or more, 25 degrees or more or less, 30 degrees or more or less, 35 degrees or more or less, 40 degrees or more or less, 45 degrees or more or less, 50 degrees or more or less, 55 degrees or more or less, 60 degrees or more or less, 65 degrees or more or less, 70 degrees or more or less, 75 degrees or more or less, 80 degrees or more or less, or 85 degrees or less, or a range defined by a combination of any of the aforesaid values and/or ranges. An example preferred range is 30 to 60 degrees. The joining angle is between 5 degrees to 70 degrees to the centreline, and the aforesaid angular values are each to be minus by 90 degrees if the joining angle is with reference to the centreline B-B' or axial line.

[0151 ] In some embodiments, the internal peripheral wall flares from an initial transversal clearance at the first axial end to reach a maximum transversal clearance in an axial direction along the axis of circular symmetry. The axial height d2 between the first axial end and the axial level of the maximum transversal clearance is a fraction of W, where W is the transversal width at the maximum transversal clearance. The axial height d2 is in the region of 0%-100% of W, for example, 0%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100% and/or any range or ranges selected from the aforesaid values.

[0152] In some embodiments, the internal peripheral wall tapers or converges to narrow from a maximum transversal clearance to reach a second axial end in an axial direction along the axis of circular symmetry, the axial height d1 between the axial level of the maximum transversal clearance and the second axial end of the receptacle body or receptacle compartment is in the region of 0%-100% of W, for example, 0%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100% and/or any range or ranges selected from the aforesaid values.

[0153] In some embodiments, the maximum transversal clearance W equals the diameter of the spherical frustum compartment of the coupling compartment and the maximum transversal clearance is defined by a circular plane encircled by the internal peripheral wall.

[0154] The axial height of the internal peripheral wall between the first axial end and the maximum transversal clearance may be determined with reference to the strength, rigidity and resilience of the materials of the protrusion member and/or the counterpart engagement member to be coupled with the protrusion member without loss of generality. [0155] In embodiments where the portion of the internal peripheral wall between the first axial end and the maximum transversal clearance is a concavely curved portion having the shape of a lower spherical segment or bowl shape, the initial transversal clearance w at the first axial end has a transversal width which is a fraction of W, where W is the transversal width at the maximum transversal span. The initial transversal clearance w is between 55% to 95% of W, including 55% or more, 60% or more or less, 65% or more or less, 70% or more or less, 75% or more or less, 80% or more or less, 85% or more or less, 90% or more or less, 95% or less, or any range or ranges defined by any combination of the aforesaid values, range or ranges. A lower spherical segment herein is one where the maximum transversal clearance is a transversal span defined by a diameter of the sphere and is parallel to and spaced apart from the base surface.

[0156] The internal peripheral wall may have a circular symmetry about a centre axis to facilitate coupling in different angular orientations about the centre axis.

[0157] Where the internal peripheral wall or a portion of the internal peripheral wall is in the shape of a spherical segment or a spherical cap, the centre axis of the internal peripheral wall is coaxial with the centre axis of the spherical segment or the spherical cap.

[0158] In embodiments where the internal peripheral wall has a concavely curved peripheral profile which extends across and about the maximum transversal clearance, the internal peripheral wall has a bulging profile about the maximum transversal clearance to define a middle bulging receptacle compartment.

[0159] In some embodiments, the receptacle body defines a ball-joint socket or a bulb-shaped receptacle compartment or a dome-shaped receptacle compartment for snap-fit reception of a ball-shaped coupling head of a counterpart connection member. The internal peripheral wall may follow the curved surface of a spherical segment in order to form snap-fit coupling engagement with an engagement portion of a counterpart connection member having a spherical segment shape. For example, the maximum internal transversal span of the internal peripheral wall which defines the maximum transversal clearance of the collar portion that may equal to the maximum transversal clearance of a sphere defining the spherical segment. In other words, the maximum transversal clearance is defined by a circular periphery having a radius SR, where SR is the radius of the sphere defining the spherical segment. The axial span or thickness of the collar member may equal to t% of the radius SR of the sphere, where t% may be larger than 15% or 20%, for example, 15% or more, 20% or more or less, 25% or more or less, 30% or more or less, 35% or more or less, 40% or more or less, 45% or more or less, 50% or more or less, 55% or more or less, 60% or more or less, 65% or more or less, 70% or more or less, 75% or more or less, 80% or less, or any range or ranges formed by a combination of any of the aforesaid values and/or ranges.

[0160] In some embodiments, the receptacle body comprises a collar portion which extends around an internal boundary of the base surface to define an entry aperture to the receptacle compartment.

[0161 ] In some embodiments, the coupling receptacle includes an axial free end, the axial free end defining the entry aperture and being flush with the base surface of the panel member.

[0162] The first axial end of the second connection member 142 is configured as a collar member 144. The collar member is an up-standing member which projects away from the second axial end in the axial direction and extends along a transverse circuit to surrounds the entry aperture to the receptacle compartment. A peripheral groove or channel is formed on the panel member 140 to surround the collar member. The peripheral groove or channel is an open channel with the channel bottom surface facing away from the second axial end. The peripheral groove or channel is formed as a depression on the second panel member 140, and the depth of the channel groove or channel defines or is equal to the axial height of the collar member 144. The collar member is a part or an extension of the hollow shell member and thickness of the collar member 144 is smaller than the thickness of the other shell parts of the hollow shell member. The peripheral groove provides a buffer space for lateral deflection of the collar member 144 so that when the internal peripheral surface of the collar member 144 is subject to an outward deflection surface, for example, when the internal peripheral surface of the collar member 144 encounters a slightly oversized engaging head of a protrusion member, the collar member 144 will deflect radially outwards into the peripheral groove.

[0163] The collar member defines a radial entry clearance or a transversal entry clearance which is smaller than the maximum transversal span of the head portion or the engaging head of a counterpart protrusion member so that the collar member 144 has to deform resiliently and to expand radially outwards to enlarge the inner boundary defined by its internal peripheral wall. When the engaging head moves in the axial direction and towards the second axial end in order to enter the receptacle compartment, the transversal clearance defined by the internal peripheral wall will be increased when the engaging head encounters the internal peripheral wall of the collar member. The peripheral groove 148 defines a clearance which is sufficiently large to permit a necessary and sufficient amount of radial outward deflection to permit through-passage of the engaging head on progressing into the receptacle compartment. In general, the width of the peripheral groove 148 at the downward facing surface 1401 of the panel member is comparable to, including equal to, or slightly larger than, the difference between the maximum transversal span and the radial entry clearance or a transversal entry clearance. Adjacent connection members or peripheral grooves 148 of adjacent connection members are connected by a web-like bridging portion which is a transversely extending portion of the sheet-like or plate-like panel member 140.

[0164] In some embodiments, including the example of Figure 5A, the inner periphery of the collar member is concavely curved as it extends between the first and second axial ends to define a concavely curved bulging receptacle compartment. The bulging receptacle compartment bulges in a transversal direction as it extends in the axial direction which is orthogonal to the transversal direction. The concavely curved bulging receptacle compartment is fit for reception of an engaging head of a counterpart connection member having a correspondingly matched convexly curved bulging head portion, for example, in the shape of a spherical segment shape, so that a snap-fit joint or a snap-fit coupling engaging with the engagement portion of the counterpart connection device. For example, the collar member 144 can function as a ball socket to receive a ball-shaped engagement portion of the counterpart connection member 122. The collar member inner periphery follows the curved surface of a spherical segment in order to form snap-fit coupling engagement with an engagement portion of a counterpart connection device having a spherical segment shape. For example, the maximum internal transversal span of the collar member inner periphery which defines the maximum transversal clearance of the collar member is equal to the maximum transversal span of a sphere defining the spherical segment. In other words, the maximum transversal clearance is defined by a circular periphery having a radius R, where R is the radius of the sphere defining the spherical segment. The axial span or thickness of the collar member may equal to h% of the diameter D of the sphere, where h may be larger than 15% or 20%, for example, 15% or more or less, 20% or more or less, 25% or more or less, 30% or more or less, 35% or more or less, 40% or more or less, 45% or more or less, 55% or more or less, 60% or more or less, 65% or more or less, 75% or more or less, 80% or more or less, 85% or more or less, 90% or less, or any ranges formed by a combination of any of the aforesaid values and/or ranges.

[0165] In general, the collar member inner periphery is to define a receptacle compartment having an initially flaring, diverging or widening compartment portion and a subsequently tapering, converging, or narrowing compartment portion for snap-fit retention of an engagement portion of a counterpart connection device

[0166] In some embodiments, the collar member inner periphery may be simply concavely curved without following the curvature of a sphere to define a generally concavely curved bulging receptacle compartment. [0167] In some embodiments, the collar member inner periphery may follow the outer curved surface of a truncated cone or a frusto-cone to define the initially flaring, diverging or widening compartment portion and/or subsequently tapering, converging, or narrowing compartment portion.

[0168] In some embodiments, the collar member inner periphery may have a combination of a frusto-conical portion and a spherical segment portion.

[0169] In some embodiments, the height or axial extend of the up standing portion of the collar member is less than the height or axial extent of the collar member. The height of the up standing portion of the collar member is about c% of the height or axial extend of the collar member, where c is typically in the region of 35% to 65%, for example, for example, 35% or more or less, 40% or more or less, 45% or more or less, 50% or more or less, 55% or more or less, 60% or more or less, 65% or less, or any ranges formed by a combination of any of the aforesaid values and/or ranges.

[0170] The coupling receptacle 146 extends beyond the collar member to form a receptacle base member. The receptacle base member extends axially away from an axial end of the collar member which is distal to the entry aperture and projecting in the axial direction away from the collar member and comprises a free axial end which is distal to the collar member. The receptacle base member defines a receptacle base compartment which is for receiving a portion of engaging portion of a counterpart connection device which projects beyond the collar portion. The receptacle base member may define a receptacle base for receiving a spherical segment portion or of other shapes complementary to the shape of the portion of the engaging portion of a counterpart connection device which projects beyond the collar portion without loss of generality. In some embodiments, the coupling receptacle comprising the collar compartment and the receptacle base compartment defines a continuous compartment for snap-fitted reception of an engaging portion having the shape of a spherical segment.

[0171 ] While the disclosure has been made with reference to the examples herein, it should be understood that the examples are for reference and should not be used for restricting the scope of disclosure.

[0172] For example, while the connection members are formed on sides and ends in the above examples, the connection members may be formed on ends, sides, a combination of ends and sides, sides only, or ends only without loss of generality.

[0173] For example, while each of the example surface bearing members has a square outer boundary, it will be appreciated that a surface bearing member can have an outer boundary of any appropriate shape, for example, circular, rectangular, polygonal, or other shapes with loss of generality. The receptacle body may comprise a collar portion which extends around an internal boundary of the base surface to define an entry aperture to the receptacle compartment. The axial free end of the receptacle body defining the entry aperture may be flush with the base surface. The collar portion and the base surface may be separated by a peripheral groove which extends around an outer periphery of the collar portion and the internal boundary of the base surface. The collar portion and the base surface is joined by a bridging portion, the bridging portion connecting an axial end of the collar portion which is distal to the axial free end of the collar portion with the base surface to define a base of the peripheral groove.

[0174] The collar portion and/or the receptacle body, the bridging portion and the base surface may be integrally or singly formed as one piece.

[0175] The collar portion may be defined by a collar member, the collar member having a collar internal peripheral wall which extends in a transversal peripheral direction to define a transversal span and a transversal clearance. The transversal clearance gradually increases from a first transversal clearance at the entry aperture to a maximum transversal clearance as the collar member extends along the second axial direction.

[0176] The collar internal peripheral wall may be a curved surface which follows curvature of a curved surface of a spherical segment as it extends in the second axial direction.

[0177] The collar portion may be circularly symmetrical about a collar centre line which is parallel to the second axial direction, and the collar internal peripheral wall is concavely curved with respect to the collar centre line to define an arcuate bulging receptacle compartment.

[0178] The receptacle body may comprise a socket body which extends axially away from the collar portion in the second axial direction.

[0179] The receptacle body may define a ball-joint socket or a bulb-shaped receptacle compartment or a dome-shaped receptacle compartment for snap-fit reception of a ball- shaped coupling head of a counterpart connection member.

[0180] The protrusion member may have a transversal span which is defined by an outer peripheral wall of a protrusion body and the transversal span gradually increases from a base transversal span to a maximum transversal span as it extends away from the first surface in the first axial direction, the transversal span being defined by a transversal plane which is orthogonal to the first axial direction and delimited by an outer boundary of the outer peripheral wall of the protrusion body.

[0181 ] The transversal span gradually decreases from the maximum transversal span to form a rounded axial end of the protrusion member. [0182] The outer peripheral wall of the protrusion body is a curved surface which follows curvature of a curved surface of a spherical segment as it extends in the first axial direction.

[0183] The protrusion body may be circularly symmetrical about a protrusion body centre line which is parallel to the first axial direction, and outer peripheral wall of the protrusion body is concavely curved with respect to the protrusion body centre line to define an arcuate bulging protrusion body.

[0184] The protrusion body may have a ball-shaped head or a bulb-shaped head or a dome- shaped head for snap-fit engagement with a ball-joint socket or a bulb-shaped receptacle compartment or a dome-shaped receptacle compartment.

[0185] The protrusion member may have a narrowed neck portion which is defined between the maximum transversal span location and the base surface, the neck portion has an arcuate base which cooperates with the base surface to define a wedging region.