THE FIELD OF THE ART

The present invention is directed to a fastening device adapted to provide secure releasable connection of enhanced strength of orthogonally abutting components of knock-down structures, providing a handy and rapid assembly and dismantling process without the use of any special tools whatsoever.

THE BACKGROUND OF THE INVENTION

It is commonly known that a variety of fastening means are employed in the interconnection of components of knock-down structures of furniture and the like. A commonly used connector comprises a pair of elongate body members, each body member being provided with a pair of projecting bosses adapted to be inserted in appropriately spaced bores of respective furniture panels, wherein the two elongate bodies are brought in alignment when the furniture panels are brought at orthogonal abutment and are secured together by a screw passing through the axial direction of their aligned assembly. This mode of connection might result in fatigue of the connection due to the continuously acting loads along the screw that secures together the elongate bodies, whilst in case of an improper action that tends to displace one panel with respect to the other, the forces acting along the axial direction of alignment of the two elongate bodies might become excessive and therefore give rise to excessive loads acting along the screw that secures them together. Furthermore dismantling of the furniture components necessitates unscrewing of the screw holding the two elongate bodies together, such unscrewing process naturally employing a screw-driver and often being an awkward task due to the location of the connector and the difficulty encountered in inserting and operating the screwdriver.

It is therefore a first object of the invention to provide a fastening device for knock-down structures and the like that will provide an enhanced strength of connection through extending the area subject to exertion of either the continuously acting forces in supporting the panels together and also the forces that might be exerted in case of possible improper displacement of one panel against the other, thereby minimizing the loads acting per unit area of the fastening device and accordingly providing a long service life thereof.

A further object of the invention is to provide at the same time a fast and handy engagement and disengagement of the parts of the fastening device without using any tools and without using any third item, screw or other, that would connect together the parts thereof and would therefore become subject to receiving and withstanding the long- term and accidental loads being exerted onto the fastening device.

Various connector types have yet been developed that might provide an extended area subject to receiving and withstanding the long-term and accidental loads being exerted therein, such connectors providing connection of furniture parts without the use of any special tools. By way of example a commonly used connector of bed frames and shelving structures comprises a first member with one or more downwardly projecting hooks and a second member with appropriately spaced slots for receiving the aforementioned hooks as the frames are brought in abutment. Such an assembly is however not lockable and provides support in one direction only since it necessitates gravity, whereas a force acting in the opposite direction, i.e. a mere upwardly acting force might remove the hooks from the slots thereby disengaging the bed frames or shelving components and such a mode of connection is obviously undesirable in most cases of knock-down structures, such as cabinets or desks.

Furthermore, a variety of knock-down structures, such as cabinets, desks, shelving structures is currently sold to the end customers in the state of packaged components and fastening accessories that the customers can thereafter assemble to build up the purchased item. A handy process of assembling the components and yielding an adequately strong connection preferably without the use of tools is then required. The same requirement for a handy assembling and disassembling process also applies when the usage of such knock-down structures necessitates repeated assembling and disassembling, such as is the case with camping equipment.

It is thus a further object of the invention with a scope of providing an enhanced strength in the connection of a pair of components of knock-down structures, such enhanced strength being obtained with a fastening device having mating parts fixedly mounted at correspondingly appropriate positions of pairs of components so that they may be brought in interactive condition when the components are connected, the connection necessitating merely the rotation of one of the mating parts around the other and snugly fitting of a member provided in one of the mating parts within a slot provided in the other resulting in an adequately locked connection of the two mating parts without the employment of any screw or other means of holding them together.

In building up a closed box structure, such as a cabinet from releasable components, it is noted that when disassembling of the structure is required while some of the components may be handily disassembled, after unlocking the device maintaining them in secure attachment, through laterally sliding one against the other, this is not the case with an initial component that needs to be removed through lifting away from the remaining box structure, since it may not be slid laterally in any direction.

It is a further object of the invention to propose the fitting device in such a form as to allow disassembly through lifting one component away from the other components of the knock-down structure following disengagement of the devices holding it in secure attachment with the other components.

SUMMARY OF THE INVENTION

The invention discloses a fastening device for the releasable connection of orthogonally abutting components of knock-down structures comprising a base member that is fixedly attached proximally at one edge of a first component of a knock-down structure and a latching member that is pivotally attached proximally at one edge of a second component of the knock-down structure, the base member comprising an elongate parallelepipedal section with a medially upwardly extending inverted L configured member, a first portion of the medially upwardly extending inverted L configured member perpendicularly oriented onto the elongate parallelepipedal section and a second portion extending at right angles with respect to the first portion at one side thereof, wherein a pair of transverse grooves are respectively provided across a first portion of the elongate parallelepipedal section at one side of the first portion of the inverted L configured member and across a second portion thereof at the other side of the first portion of the inverted L configured member, and the latching member being a continuous Π-section singular item with an elongate side and a pair of relatively short first and second side legs, respectively extending at a bottom end adapted to fit within one transverse groove of the base member and at a tubular bottom end adapted to snugly fit within another transverse groove of the base member when the fastening device is set at locked condition for connection of the components of the knock-down structure.

In accordance with a first embodiment of the invention, the base member of the fastening device is a single item comprising the elongate parallelepipedal section with the medially upwardly extending inverted L configured member, and in accordance with a second embodiment the base member of the fastening device comprises a pair of portions, wherein a columnar member and a rectangularly configured strip underlying the columnar member extends medially along the longitudinal direction at the bottom of the elongate parallelepipedal section with the medially upwardly extending inverted L configured member, and a further portion of an elongate parallelepipedal body is provided with a channel being adapted to receive the abovementioned rectangularly configured strip entering therein through an open end of this further portion and terminating at an opposite closed end thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be best understood by those skilled in the art by reference to the accompanying drawings in which:

Fig. 1 shows an exploded perspective view of a first embodiment of the fastening device of the invention comprising a base member and a latching member including the screws employed in fixedly mounting the same onto a pair of first and second mating components of a knock-down structure.

Figs, la and lb show a frontal view of the latching member and of the base member of the fastening device depicted in Fig. 1 respectively.

Fig. 2a shows a perspective view of a pair of a first and a second mating components of a knock-down structure and of the base member and latching member of the fastening device depicted in Fig. 1 being respectively brought in a position for mounting thereupon, wherein a covering surface of the latching member is shown partially cut to reveal the underlying latching member.

Fig. 2b shows a perspective view of the pair of first and second mating components of the knock-down structure of Fig. 2a with a screw being driven through the latching member for pivotally mounting it onto the second component of the knock-down structure and with the base member of the fastening device being aligned with a pair of protruding tubular extensions at the bottom thereof overlying a pair of receiving bores onto the first component of the knock-down structure.

Fig. 2c shows a perspective view of the pair of first and second mating components of the knock-down structure of Fig. 2b with the screw having been driven through and having pivotally mounted the latching member onto the second component of the knockdown structure and with the pair of protruding tubular extensions at the bottom of the base member of the fastening device having been inserted within the pair of receiving bores onto the first component of the knock-down structure.

Fig. 2d shows a perspective view of the pair of first and second mating components of the knock-down structure of Fig. 2c with the latching member pivotally mounted onto the second component of the knock-down structure and a screw being driven through the base member for fixedly mounting it onto the first component of the knock-down structure.

Fig. 2e shows a perspective view of the pair of first and second mating components of the knock-down structure of Fig. 2d with the second component having the latching member pivotally mounted thereupon being brought in a condition of orthogonal abutment onto the first component of the knock-down structure, whereby the latching member is positioned at an operationally rightful orientation for interacting with the base member of the fastening device.

Fig. 2e' shows a detailed view of the positioning of the latching member and of the base member as depicted in Fig. 2e without the surface partially covering the latching member so as to allow viewing of the process of interaction of the members of the fastening device.

Fig. 2f shows a perspective view of the pair of first and second mating components of the knock-down structure of Fig. 2e with the second component having the latching member pivotally mounted thereupon being displaced laterally so as to bring a side leg of the latching member within the area underneath an arm of an L-configured portion of the base member of the fastening device.

Fig. 2f shows a detailed view of the positioning of the latching member within the base member of the fastening device as depicted in Fig. 2f without the surface partially covering the latching member so as to allow viewing of the process of interaction of the members of the fastening device.

Fig. 2g shows a perspective view of the pair of first and second mating components of the knock-down structure of Fig. 2f wherein rotation of the latching member is initiated with a scope of setting the fastening device at a locked condition.

Fig. 2g' shows a detailed view of the positioning and initiation of rotation of the latching member within the base member of the fastening device as depicted in Fig. 2g without the surface partially covering the latching member so as to allow viewing of the process of interaction of the members of the fastening device.

Fig. 2h shows a perspective view of the pair of first and second mating components of the knock-down structure of Fig. 2g wherein rotation of the latching member has been terminated and the fastening device has been set at a locked condition through snugly fitting of a tubular bottom end of a side leg of the latching member within a transverse groove of the base member thereof.

Fig. 2h' shows a detailed view of the locked condition of the fastening device of the invention as shown in Fig. 2h following termination of the rotation of the latching member and snuggly fitting of a tubular bottom end of a side leg thereof within a transverse groove of the base member thereof, wherein the surface partially covering the latching member has been removed so as to allow viewing of the process of interaction of the members of the fastening device.

Fig. 2h" shows a frontal view of the fastening device at a locked condition with an overall view of the surface covering thereof.

Fig. 3 shows an exploded perspective view of a second embodiment of the fastening device of the invention comprising a latching member and a base member, the latter consisting of two mating portions, including the screws employed in fixedly mounting the latching and base members onto a pair of first and second mating components of a knock-down structure.

Fig. 3a shows a frontal view of the latching member of the fastening device depicted in Fig. 3.

Fig. 3b shows a transverse view taken along the middle of the parallelepipedal section portion of the base member and Fig. 3 c shows a planar view thereof.

Fig. 3d shows a transverse view at one end of the parallelepipedal section underlying an inverted L-configured member portion of the base member.

Fig. 4a shows a perspective view of a pair of a first and a second mating components of a knock-down structure and of the latching member and of a pair of portions constituting the base member of the fastening device depicted in Fig. 3 being respectively brought in a position for mounting onto the components of the knock-down structure, wherein a covering surface of the latching member is shown partially cut to reveal the underlying latching member and an elongate parallelepipedal body portion of the base member of the fastening device is shown in a position of alignment of a pair of protruding tubular extensions at the bottom thereof over a pair of receiving bores onto the first component of the knock-down structure.

Fig. 4b shows a perspective view of the pair of first and second mating components of the knock-down structure of Fig. 4a with the latching member being ready for pivotally mounting onto the second component of the knock-down structure and with the pair of protruding tubular extensions at the bottom of the elongate parallelepipedal body portion of the base member of the fastening device having been inserted within the pair of receiving bores provided onto the first component of the knock-down structure.

Fig. 4c shows a perspective view of the pair of first and second mating components of the knock-down structure of Fig. 4b with a screw being driven through the latching member for pivotally mounting it onto the second component of the knock-down structure and with a screw being driven through the elongate parallelepipedal body portion of the base member for fixedly mounting it onto the first component of the knock-down structure.

Fig. 4d shows a perspective view of the pair of first and second mating components of the knock-down structure of Fig. 4c with the elongate parallelepipedal body portion of the base member fixedly mounted onto the first component of the knock-down structure and a screw being driven through the latching member for pivotally mounting it onto the second component of the knock-down structure.

Fig. 4e shows a perspective view of the pair of first and second mating components of the knock-down structure of Fig. 4d with the second component having the latching member pivotally mounted thereupon being brought in a condition of orthogonal abutment onto the first component of the knock-down structure, whereby the latching member is positioned at an operationally rightful orientation for interacting with the elongate parallelepipedal body portion of the base member of the fastening device.

Fig. 4e' shows a detailed view of the positioning of the latching member and of the base member as depicted in Fig. 4e without the surface partially covering the latching member so as to allow viewing of the process of interaction of the members of the fastening device.

Fig. 4f shows a perspective view of the pair of first and second mating components of the knock-down structure of Fig. 4e with the elongate parallelepipedal section having a medially upwardly extending inverted L configured member portion of the base member being inserted within the elongate parallelepipedal body portion of the base member of the fastening device and taking an appropriate position for interacting with the latching member pivotally mounted onto the second component of the knock-down structure.

Fig. 4f shows a detailed view of the positioning of the latching member within the base member of the fastening device as depicted in Fig. 4f without the surface partially covering the latching member so as to allow viewing of the process of interaction of the members of the fastening device.

Fig. 4g shows a perspective view of the pair of first and second mating components of the knock-down structure of Fig. 4f wherein rotation of the latching member is initiated with a scope of setting the fastening device at a locked condition.

Fig. 4g' shows a detailed view of the positioning and initiation of rotation of the latching member within the base member of the fastening device as depicted in Fig. 4g without the surface partially covering the latching member so as to allow viewing of the process of interaction of the members of the fastening device.

Fig. 4h shows a perspective view of the pair of first and second mating components of the knock-down structure of Fig. 4g wherein rotation of the latching member has been terminated and the fastening device has been set at a locked condition through snugly fitting of a tubular bottom end of a side leg of the latching member within a transverse groove of the base member thereof.

Fig. 4h' shows a detailed view of the locked condition of the fastening device of the invention as shown in Fig. 4h following termination of the rotation of the latching member and snuggly fitting of a tubular bottom end of a side leg thereof within a transverse groove of the base member thereof, wherein the surface partially covering the latching member has been removed so as to allow viewing of the process of interaction of the members of the fastening device.

Fig. 4h" shows a frontal view of the fastening device at a locked condition with an overall view of the surface covering.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

The invention relates to a fastening device used in connecting together the components of knock-down structures, e.g. of furniture, such as of a desk and of a cabinet, of panel components as used to assemble stands in an exhibition hall and of rack structures adapted to provide storage space of various items.

The fastening device of the invention is particularly used to provide releasable connection of orthogonally abutting components of knock-down structures and comprises a base member that is fixedly attached proximally at one edge of a first component 10 of the knock-down structure and a latching member that is pivotally attached proximally at one edge of a second component 20 of the knock-down structure that is brought at orthogonal abutment with the first component 10 thereof. In accordance with a first preferred embodiment of the invention, as shown in the exploded view of Fig. 1, the fastening device of the invention comprises a base member 1 and a latching member 2. In accordance with a second preferred embodiment of the invention as shown in the exploded view of Fig. 3 the base member of the fastening device comprises a pair of detachably assembled mating portions 6 and 7.

The latching member 2 of the invention, as illustratively shown in the cross sectional view of Fig. la of the first embodiment or of Fig. 3a of the second embodiment is a continuous Π-section singular item with an elongate side 21 and a pair of first and second side legs 22 and 23 respectively, which are relatively shorter than the elongate side 21. A first side leg 22 of the latching member 2 is perpendicularly oriented at one end of the elongate side 21 and thereafter extends into an inwardly inclined portion 22a and into a triangularly configured block having a base 22a and sides 24a and 24b, this triangularly configured block thereby extending inwardly the Π-section and being provided with a through hole 25 adapted to receive a cylindrical bracket 3. The latching member 2 is mounted onto the aforementioned second component 20 of the knock-down structure with a screw 4 being driven into the cylindrical bracket 3 that is previously inserted in the through hole 25 and into the body of the second component 20 of the knock-down structure, whereby the latching member 2 is pivotally attached therein and may, as will be explained hereinafter, perform a rotation around the axial direction of the screw 4 with a scope of alternatively setting the latching member 2 at a position of engagement or disengagement with the base member 1 or 6,7 of the fastening device.

A preferably rounded bottom end 27 is formed at the point of convergence of sides 22a and 24a of the triangularly configured block at the end of the first side leg 22-22a, whilst side 24b of the triangularly configured block extends perpendicularly onto the side leg 22 inwardly the Π-section, whereby this side 24b of the triangularly configured block is being oriented in a direction parallel to the aforementioned elongate side 21 of the Π- section and a cavity 26 is thereby being formed between side 24b of the triangularly configured block and the elongate side 21.

The aforementioned second side leg 23 of the Π-section of the latching member 2 is shown slightly inclined outwardly and extends at a tubular bottom end 28 that is adapted to snugly fit within an appropriately configured transverse groove of the base member when the fastening device is being set at a locked condition. An outwardly extending angularly configured extension 29 of this second side leg 23 serves to provide a handy handle means of manually rotating latching member 2 with a scope of alternatively setting it a condition of engagement with or disengagement from the base member 1 or 6,7 of the fastening device.

In accordance with the first preferred embodiment of the invention as shown in the exploded view of Fig. 1 and the cross sectional view of Fig. lb, the base member 1 of the fastening device of the invention consists of an elongate parallelepipedal section with a medially upwardly extending inverted L configured member, wherein the medially upwardly extending inverted L configured member consists of a first portion 13 perpendicularly oriented onto the elongate parallelepipedal section and a second portion 14 extending at right angles with respect to the first portion 13 at one side thereof. Accordingly the elongate parallelepipedal section comprises a first portion 1 1 at one side of the aforementioned first portion 13 of the inverted L configured member and a second portion 12 at the other side of the aforementioned first portion 13 of the inverted L configured member. A pair of transverse grooves 17 and 18 are respectively provided across the aforementioned second and first portions 12 and 1 1 of the elongate parallelepipedal section, such transverse grooves 17 and 18 being respectively adapted to receive the rounded bottom end 27 of the first side leg 22-22a and the tubular bottom end 28 of the second side leg 23 of the latching member 2 when the latter interacts with the base member 1.

A through hole 15 is provided axially through the aforementioned first portion 13 of the inverted L configured member and through the underlying parallelepipedal section, such through hole 15 being adapted to receive a screw 5 that is being driven through this hole 15 and into the body of the first component 10 of the knock-down structure to fixedly mount the base member 1 therein.

In accordance with a second preferred embodiment of the invention as shown in the exploded view of Fig. 3 and the cross sectional views of Figs. 3b, 3c and 3d, the base member of the fastening device of the invention comprises two portions 6 and 7, wherein portion 7 again represents the elongate parallelepipedal section of the first abovementioned embodiment that comprises a medially upwardly extending inverted L configured member, wherein the medially upwardly extending inverted L configured member consists of a first portion 73 perpendicularly oriented onto the elongate parallelepipedal section and a second portion 74 extending at right angles with respect to the first portion 73 and at one side thereof. Accordingly the elongate parallelepipedal section comprises a first portion 71 at one side of the aforementioned first portion 73 of the inverted L configured member and a second portion 72 at the other side of the aforementioned first portion 73 of the inverted L configured member. A pair of transverse grooves 77 and 78 are respectively provided across the aforementioned second and first portions 72 and 71 of the elongate parallelepipedal section, such transverse grooves 77 and 78 being respectively adapted to receive the rounded bottom end 27 of the first side leg 22-22a and the tubular bottom end 28 of the second side leg 23 of the latching member 2 when the latter interacts with the base member.

In this second preferred embodiment the herein described elongate parallelepipedal section of portion 7 is formed with a bottom extension of a columnar member 79 and a rectangularly configured strip 80 underlying the columnar member 79, wherein the columnar member 79 and underlying strip 80 is provided medially along the longitudinal direction from one side of the first portion 71 to the other side of the second portion 72 of the elongate parallelepipedal section.

A lower portion 6 of the base member as illustratively depicted in Fig. 3 and in the sectional view of Fig. 3b is an elongate parallelepipedal body having a length and width equivalent to the length and width of the elongate parallelepipedal section of base portion 7 with a bottom surface 61 and parallel side surfaces 62, 63 at either end thereof, wherein the ends of these side surfaces 62, 63 are being turned inwardly into short flanges 62a, 63a oriented in a direction parallel to the bottom surface 61, whereby a channel 60 is being formed in between bottom surface 61 and these upper flanges 62a, 63a, such channel 60 being appropriately configured for receiving the aforementioned rectangularly configured strip 80 of base portion 7 that enters within channel 60 through an opened end 67a of one of the short sides of portion 6 and terminates at the opposite closed end 67b of the other one of the short sides thereof.

In accordance with a preferred embodiment of the invention with a scope of achieving a unidirectional introduction of portion 7 into portion 6, the latter is provided with a medially longitudinally extending shallow groove 66 disposed along a portion of the length of portion 6 inwardly from the open end 67a thereof and portion 7 is provided with a correspondingly configured protrusion 76 extending medially underneath the rectangularly configured strip 80 along a portion of the length of portion 7 corresponding to the aforementioned length of grove 66 of portion 6, whereby introduction of portion 7 within portion 6 may only be effected through introduction of the side thereof that is provided with such protrusion 76 operationally inserted within the shallow groove 66.

As shown in Fig. 3, a pair of semicircularly configured recessions 68 is provided at symmetrically opposing locations of the flanges 62a, 63a, such recessions 68 being configured to lie underneath the aforementioned transverse groove 78 of base member portion 7 in the assembled mode of portions 6 and 7 and being adapted to receive the tubular end 28 of the latching member 2 of the fastening device as the device is being set at a locked condition.

As the cross sectional view of portion 6 in Fig. 3b has been taken across the middle thereof it also shows a through hole 65 (also shown in the planar view of Fig. 3c) wherein is being driven screw 5 for appropriately fixedly mounting portion 6 onto the component 10 of the knock-down structure. As shown in Fig. 3c a further hole 65a might be provided for a supplementary screw being employed in the process of fixedly mounting portion 6 onto the component 10.

Whilst fixedly mounting portion 6 onto the component 10 of the knock-down structure and subsequently inserting portion 7 therein to obtain a fully operational base portion for the fastening device of the invention is expected to provide an adequately strong connection onto the component 10 of the knock-down structure, in accordance with an alternative embodiment of the invention, an appropriately elongate screw 5 is employed which passes through a hole 75 provided axially along the portion 73 of the inverted L configured member of portion 7 and is subsequently driven through the underlying hole 65 of portion 6 and into the body of component 10 of the knock-down structure. Evidently in this case portions 6 and 7 are matched together prior to insertion of screw 5.

It is herein noted that whilst employment of the base portion 1 of the first embodiment of the invention allows dismantling of the mating components 10, 20 of the knock-down structure connected with the fastening device of the invention through sideward movement of one component against the other following rotation of the latching member 2 so as to render a condition of disengagement thereof from the base portion, employment of the base portion 6,7 of the second embodiment of the invention additionally allows dismantling of the mating components 10, 20 of the knock-down structure connected with the fastening device of the invention through lifting of component 20 with the latching member 2 of the fastening device fixedly mounted thereupon away from the component 10 of the knock-down structure to which it is connected. As seen from consecutive figures 2e and 2f of the first embodiment of the invention, the component 20 of the knock-down structure is first moved downwardly to abut the component 10 (Fig. 2e) and thereafter it is being laterally displaced in order to bring the latching member 2 mounted thereupon in a condition of interaction with the base member 1 mounted onto the component 10 of the knock-down structure (Fig. 2f). A reverse lateral displacement of component 20 is therefore required in order to free the latching member 2 from the base member 1 and take the component 20 away from component 10 during a dismantling operation of the knock-down structure. Such lateral displacement is however not required when, in accordance with the second embodiment of the invention, the fastening device uses the base member that consists of the two portions 6 and 7, whereby reference to consecutive Figures 4e and 4f reveals that instead it is portion 7 that is laterally displaced in order to fit within portion 6 that is fixedly mounted onto the component 10.

In accordance with a preferred embodiment of the invention, a pair of protruding tubular extensions 19 in the first embodiment of base member 1 or 69 in the second embodiment of base member 6,7 is provided underneath the base portion 1 of the first embodiment or of the portion 6 of the base portion 6,7 of the second embodiment, such tubular extensions 19 or 69 being adapted to fit within bores 9 of appropriate depth provided along a standardized linear direction of component 10 of the knock-down structure at a predetermined spacing therein. The abovementioned bores 9 along the component 10 of the knock-down structure are provided at a distance from the edge of the side of component 10 that is adapted to abut the mating component 20 of the structure with the latching member 2 of the fastening device mounted thereupon, such distance being determined by the thickness of mating components 10, 20 and the requirement of achieving an operational positioning of the base member for interacting with the latching member of the fastening device when such mating components 10, 20 are led at connection as shown e.g. in Fig. 4e. Employment of such tubular extensions 19 or 69 therefore on the one hand provides means of secure attachment of base portion 1 or 6,7 onto component 10 of the knock-down structure and on the other hand provides a guided fixing of such base portion 1 or 6,7 that results in an operationally correct positioning for interacting with the latching member 2 fixedly mounted onto the mating component 20 of the knock-down structure.

It is herein noted that the base member 1 preferably has a width equivalent or nearly equivalent to the width of the latching member 2.

In accordance with an optional embodiment of the invention a rectangularly configured surface 30 covers the entire latching member 2 and in particular it covers the exposed side thereof, i.e. the side opposite to the side abutting the component 20 of the knockdown structure. When the fastening device is set at a locked condition the abovementioned rectangularly configured surface 30 actually covers the entire device including the base portion 1 or base portion 6,7 thereof as illustrated in Fig. 2h" and in Fig. 4h".