DESCRIPTION

The present invention concerns a spherical gear according to the characterizing part of claim 1.

In mechanical applications it is often necessary to transmit a rotary motion from a first to a second apparatus; more specifically, the transmission of a rotary motion is required between two rotating shafts, one guiding and the other guided.

To do this, solutions such as the use of toothed wheels and drive belts are known in the art.

For the former it is sufficient that a toothed wheel is integral with the guide shaft and is kinematically linked to one or more further intermediate toothed wheels capable of transmitting the motion to the toothed wheel integral with the guided shaft. In an alternative embodiment, the toothed wheels of the guide shaft and the guided shaft can engage directly with each other.

Conversely, for the drive belts, the guide shaft and the guided shaft each have a pulley on which the drive belt is wrapped.

These solutions have important application limitations since they require a considerable space for housing the components and do not offer the possibility of varying their configuration without completely disassembling the system and reassembling it with the elements in different positions.

In the applications of robotics it is often necessary to transmit a rotary motion from a guide shaft to a guided shaft using very small spaces and it is also advantageous to be able to benefit from a flexible system capable of allowing the transmission of the motion continuously even when the shafts in question vary their mutual angle, as can happen for example inside a robotic arm, where more elements of the arm must be able to be free to rotate with respect to each other and therefore it is advantageous that the internal components of the arm that deal with the transmission of the motion from, for example an electric motor to a guided shaft, can flex, adapting to the movements of the robotic arm. Obviously, a device for the transmission of the motion of this type must be provided with a gear with a shape suitably designed to allow continuous operation during its deformation. The gears of known type have teeth whose shape is not compatible with the variation of the inclination of their axes of rotation during operation, since the head surfaces of the teeth and the bottom surfaces are straight and therefore can only operate correctly when two successive toothed wheels are perfectly aligned otherwise, with a continuous change of inclination of the wheels, the contact surface between the respective teeth would continue to vary, compromising the correct operation of the apparatus. In addition, the heads of the teeth could slam against the bottom surfaces effectively blocking the mechanism.

The object of the present invention is to provide a spherical gear having the tooth heads and the bottom surfaces shaped in such a way as to allow a continuous variation of the mutual inclination between two mutually engaged gears.

This is achieved, according to the invention, by conforming the spherical gear according to the characterizing part of claim 1.

This type of spherical gear is suitable for use in a device for transmitting the motion capable of transmitting a rotary motion starting from a guide shaft up to a guided shaft by means of a series of spherical gears connected to each other so as to be able to vary their mutual angle to follow a possible variation of the mutual angle between the aforesaid shafts.

Further features of the invention are present in the dependent claims. The terms used in the present document are used for the description of the embodiments and are not intended to limit the inventive concept. As used herein, the singular forms are intended to comprise plural forms as well, unless the context clearly dictates otherwise. It will also be understood that the terms “comprises” and/or “comprising” specify the presence of indicated features, components and/or operations, but do not preclude the presence or the addition of one or more other features, components and/or operations. In addition, identical numerals shall indicate identical components throughout the description and the meaning of “and/or” comprises each mentioned element and each combination of mentioned elements. It shall be understood that although the terms first, second, etc. may be used herein to describe various components, these components should not be limited by these terms. These terms are only used to distinguish one component from another component. Thus, a first component could be defined as a second component without departing from the teachings of the inventive concept.

Unless otherwise defined, all the terms (including the technical-scientific terms) used herein have the same meaning as commonly understood by those skilled in the art to which the inventive concept belongs.

The spatially related terms, such as “below,” “under”, “lower,” “over”, “upper”, “above”, and the like, may be used in the present document for ease of description to describe the relationship of one component or of one feature to another component or feature as illustrated in the figures. It shall be understood that the spatially related terms are intended to comprise different orientations of the device in use or in operation in addition to the orientation illustrated in the figures. For example, if the component in the figures is inverted, the components described as “under” or “below” other components or features would then be oriented “above” the other components or features. Thus, for example the term “under” may comprise an orientation both above and below. The component may be differently oriented and the spatially related descriptive elements used herein may be interpreted accordingly.

The characteristics of the invention will now be described in detail below, with reference to some particular embodiments thereof, made by way of non-limiting example only, with the help of the attached drawing tables, where:

- Fig. 1 shows a perspective view in a rectilinear configuration of a device for transmitting motion that uses in its inside spherical gears referred to in the invention;

- Fig. 2 shows a perspective view in a folded configuration of a device for transmitting motion that uses in its inside the spherical gears referred to in the invention;

- Fig. 3 shows an exploded view of an end shell comprising a spherical gear referred to in the invention;

- Fig. 4 shows an exploded view of a shell compri sing a spherical gear referred to in the invention;

- Fig. 5 shows an exploded view of a particular embodiment of an end shell.

- Fig. 6 shows a schematic perspective view of a spherical gear referred to in the invention;

- Fig. 7 shows a schematic side view of a spherical gear referred to in the invention;

- Fig. 8 shows a schematic top view of a spherical gear referred to in the invention.

- Figs. 9A and 9B show the variation of an angle a between two adjacent intermediate shells after their movement; - Figs. 10A and 1OB show two constructional details that exemplify the geometries of a tooth of a spherical gear referred to in the invention;

- Fig. 11 shows an exploded view of a rotating drum which may be provided at the end of a device for transmitting motion referred to in the invention;

- Fig. 12 shows an exploded of a pinion-rack assembly which may be provided at the end of a device for transmitting motion referred to in the invention.

A spherical gear 100 referred to in the invention (Figs. 6-8) consists of a toothed wheel comprising two flat and parallel base surfaces 101 and whose peculiarity is that the head surfaces 102 present on the tooth heads consist of spherical spindles which are interrupted with respect to their ideal geometric development at the base surfaces 101 and which belong to an imaginary sphere, whose centre coincides with the geometric centre of the gear.

As visible in Figs. 10A and 10B, the teeth of the spherical gear 100 have a crosssection composed of a head section 110 from whose ends a pair of flanks 104 each ending in at least one base section 111 branch downwards.

The bottom surfaces 103 are defined by the development of each base section 111 along equatorial circumferences that are interrupted at the base surfaces 101, the diameter of which lies on the radial axis of symmetry X-X of the gear and each passing through a geometric point of said base section 111.

The bottom surfaces 103 and the head surfaces 102 are joined to each other through flanks 104 defined by the development of the side sections along the equatorial end circumferences of the head surfaces 102 and of the bottom surfaces 103.

This configuration of the teeth guarantees the constancy of the contact surface between two spherical gears during their use, leading to the minimisation of the plays, frictions, wear and consequently maximisation of the mechanical yield. Figs. 10A and 10B illustrates the geometric lines that are used for the construction of the teeth of a spherical gear referred to in the invention. The above-mentioned equatorial circumferences in Fig. JOB correspond to the circumferences 200’, 200” and 200’” and are exemplary circumferences that correspond respectively: to the circumference passing through the outer end of the base section 111, a circumference passing through an intermediate point of the base section 111 and the circumference passing through the inner end of the base section 111.

These figures show the construction of a single tooth, but it is evident that for the construction of the entire gear it is sufficient to bring closer several teeth built in this way.

The sides 104 of the spherical gear teeth may be straight or non-straight, for example curvilinear, depending on the particular needs connected with the transmission of the motion.

It is important to note that a spherical gear referred to in the invention is not simply made up of teeth with profiles of an arc of a circle and the structure obtained by developing the tooth along equatorial circumferences allows to obtain a gear that reaches the advantages mentioned above.

“Equatorial circumference” means any circumference having its centre coinciding with the geometric centre of the spherical gear 100.

Gears of this type can engage with each other without the need for their mutual orientation to remain constant during operation, thanks to the particular shape of the head and bottom surfaces which, being curvilinear, follow the variation in inclination between the gears without blocking them and keeping constant the size of the contact surface of two gear teeth engaged. A device for transmitting motion is described below which comprises spherical gears in its inside referred to in the invention.

As visible in Fig. 1, a preferred embodiment of the transmission device comprises a plurality of shells 2, advantageously rectangular in shape, arranged side by side along a longitudinal direction of development, which is clearly identifiable when the shells all lie on the same plane and are aligned with each other, so that the device is in a rectilinear configuration. The shells 2 are divided into intermediate shells 2’ and end shells 2”, the latter being the two shells placed at the ends of the device 1, which comprise between them all the intermediate shells 2’.

The aforesaid longitudinal direction of development is a straight line that ideally joins the two end shells when the device is in the rectilinear configuration of Fig. 1.

The shells 2 can be made of plastic, metal or in any case any material that has sufficient strength for the application for which the device is intended and have two opposite major surfaces 4 and side walls 5.

As visible in Figs. 3 and 4, the shells 2 can consist of a pair of half-shells 3’, 3”, adapted to be fixed to each other by means of screws, rivets or any reversible or non-reversible fastener that allows sufficient structural solidity.

In order to allow the shells 2 to be able to rotate with respect to each other independently, so as to follow the movements of the shafts that the device connects, they are fixed to each other by means of rotatable coupling means 6 that allow a rotation of each shell 2, with respect to the previous or following one in order to vary the angle a that subsists between the major surfaces 4 of the shells in question that are facing the same side of the device 1. The variation of the angle a is visible in Figs. 9 A and 9B where, in Fig. 9A with the shells 2 in a rectilinear configuration is equal to 180°, while in Fig. 9B with the shells 2 inclined between them has a value of less than 180°. These Figures are given for exemplary purposes only and without intending to limit the invention to a particular limit value of the angle a.

A folded configuration of the device 1 is visible in Fig. 2 and the variation of the different angles a with respect to the rectilinear configuration of Fig. 1 is evident.

The aforesaid rotatable coupling means 6 can consist, for each shell 2, of a pair of arms 6’ each placed at a side wall 5 thereof and having a first end pivoted to the shell 2 in question and a second end pivoted to an adj cent shell 2.

Advantageously, the arms 6’ coming from the previous shell 2 and those going towards the next shell 2 have their ends ending on the shell 2 in question which are superimposed on each other and pivoted on the shell 2 by means of a single pin, as visible from Figs. 1 and 2. In this way it is possible to make the device 1 more compact.

To allow the transmission of the motion between the shells 2, the pair of end shells 2” has an open side wall 7 and the intermediate shells 2’ have a pair of open walls 7 mutually opposite and each shell 2 comprises in its inside a spherical gear 100 whose teeth engage with the teeth of the spherical gears 100 adjacent thereto through said open walls 7. Thus, the spherical gear 100 of an end shell 2” engages with a single spherical gear 100 of the intermediate shell 2’ adjacent thereto, while the spherical gear 100 of an intermediate shell 2’ engages with the two spherical gears 100 of the shells 2 between which it is placed.

The shells 2 in their inside provide a special housing 9 able to accommodate the spherical gears 100.

In one embodiment the end shells 2” have a second open wall 7 opposite the first and the teeth of the spherical gears 100 protruding from this second open wall do not engage with other teeth of further shells 2. The aforesaid end shells 2” have means suitable for the connection of their spherical gear 100 to elements for the entry and exit of the motion. For example, in a preferred embodiment clearly visible in Fig. 3, the hub of their spherical gears 100 has a square-shaped hole capable of receiving a complementary-shaped shaft in its inside, so that the mechanical interlock that occurs allows the transmission of the motion from said shaft to the device referred to in the invention or vice versa. Obviously, in order to allow the interlock with the shaft, the major surfaces 4 of the end shells 2” have a through hole at the position where the square-shaped hole of the gear 100 is located.

In another alternative embodiment shown in Fig. 5 at least one end shell 2” has two opposite open side walls 7 and is fixed to a connecting shell 10, which can advantageously consist of two half-shells, which comprises in its inside a compartment 11 which contains an endless screw 12 fixed to a shaft 13 adapted to transmit a rotary motion in or out of the device, which projects from the compartment 11 through an opening 14.

The open wall 7 can be fixed to the end shell 2” for example by interlocking elements protruding therefrom to be fixed with complementary openings provided on the major surfaces 4 of the end shell 2” or vice versa, as visible in Fig. 5.

The endless screw 12 is arranged with its axis of rotation orthogonal to the direction of development of the device and lying on the plane of rotation of the spherical gear 100 of the end shell 2” to which it is linked.

The spherical gear 100 engages with the endless screw 12 through the open side wall 7 turned outwards of the device 1. The shaft 13 can be linked to a source of a rotary motion, so as to transmit a motion at the entry to the device or it can transmit a rotary motion to a mechanical element to be guided.

In an alternative embodiment not illustrated, the structural element 10 and the end shell 2” form a single element and form a monoblock.

In a further alternative embodiment both end shells 2” have this configuration just described.

In a further embodiment of the device referred to in the invention, in order to ensure greater structural solidity, in particular with respect to forces that can influence transversely the invention, it is provided that for each shell 2 the side walls 5 end at the open walls 7 with an end provided with horizontal teeth 15, i.e. parallel to the planes identified by the major surfaces 4, and adapted to engage with the respective teeth 15 present on the end of the side wall 5 on which the adjacent shell 2 faces.

In this way the shells 2 are more closely linked to each other and the support ensured by this configuration helps reduce the side bending of the device. The device will therefore be able to bend only as far as the rotatable coupling means 6 allow.

Advantageously, it can also be provided that the side walls 5 of the shells end at the open walls 7 either with a convex profile or with a concave profile in an arc of a circle complementary to each other, as visible in Figs. 3 and 4. The intermediate shells 2’ thus made have the convex profiles at an open wall 7, while at the other one the concave profiles are arranged so that between adj cent shells the aforesaid profiles are facing those complementary to them. The same applies to the end shells 2” whose profile of the side walls 5 is complementary to that of the side walls 5 of the intermediate shells 2’ adjacent to them. This solution further increases the resistance to the transverse forces that can affect the device, since in case of transverse bending the complementary profiles would come into contact opposing deformation.

Considering what has been described, it is evident that the rotary motion at the entry to an end shell 2” can cross the entire device 1 referred to in the invention by means of the spherical gears 100 of the intermediate shells 2’, and then exit at the other end shell 2”.

In an alternative embodiment illustrated in Fig. 11 at least one end shell 2” is connected to a rotating drum 300 for transmission of the motion. A bevel wheel 301 is mechanically connected to the spherical gear 100 of the end shell 2” in question and is placed outside of it. This connection can take place, for example, by means of a shaft that connects the spherical gear 100 with the bevel wheel and that is coaxial to said gear. For the latter solution it is provided that the end shell 2” is provided with a hole to allow the passage of said shaft.

The aforesaid bevel wheel 301 is coupled to a further bevel wheel 302 integral with the rotating drum 300 and whose axis of rotation is the same as that of said rotating drum 300.

To hold the drum 300 in place on the end shell 2”, a circular plate 303 is provided which has a housing 304 in which said end shell 2” is inserted and which rests on an abutment bead 305 present on the inner surface of the rotation drum 300. During operation, the rotating drum 300 is able to rotate with respect to the circular plate 303, thus a sliding will take place between the circular plate 303 and the surface of the abutment bead 305 on which it rests. The circular plate 303 is retained on the rotation drum 300 by means of a threaded crown 306 screwed onto a thread present on the inner surface of the rotation drum 300, above the abutment bead 305.

In a further embodiment illustrated in Fig. 12, at least one end shell 2” is connected to a pinion-rack system 400. A shaft 402 mechanically connects the spherical gear 100 of the end shell 2” in question and the pinion 401 with the same modalities described above with respect to the embodiment having the rotation drum 300. Said pinion 401 is able to slide along a rack 403.

This configuration can be used for example in a gate opener device. From the above it can therefore be inferred how spherical gears referred to in the invention can engage each other with no need for their mutual orientation to remain constant during operation allowing to obtain a device for transmitting motion capable of bending as described above.

While the inventive concept has been described with reference to exemplary embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the scope of the inventive concept. Therefore, it should be understood that the above embodiments are not limiting, but illustrative. The invention is defined by the following claims.