GB2092396A

GB2092396A - Push-pull connector

Info

Publication number: GB2092396A
Application number: GB8200223A
Authority: GB
Original assignee: Bunker Ramo Corp
Current assignee: Bunker Ramo Corp
Priority date: 1981-01-07
Filing date: 1982-01-05
Publication date: 1982-08-11
Also published as: GB2092396B; DE3200265A1; DE3200265C2

Abstract

A connecting device includes a connector 1 shown as a male connector which includes an interior sleeve 2 and an exterior cylindrical sleeve 3, axially sliding in regard to the interior sleeve. An insulating block 4, arranged at the interior of the sleeve 2, contains a contact element 6. Elastic tongues 15 ensure the retention of an element of a female connector connectable with the element of a male connector 1 and are held in a locking position by a portion 21 of the exterior sleeve 3. The sleeve 2 includes at its periphery an open V- groove 22 determining two inclined surfaces 23 and 24. The exterior sleeve 3 includes elastic tongues 25, the ends of which have a rounded protuberance 26, which tend to restore the sleeve 3 into its locking position after having been manually pushed towards the connecting front surface or pulled in the opposite direction. In alternative embodiments the tongues 25 are replaced by a split ring 32 (Figure 2) bearing against the V-groove 22, by a split ring 64 (Figure 5) bearing on the V-groove through balls 63, or by a split ring 71 (Figure 6) having integral rounded protuberances 72. The device may be used, for example, with either an electrical connector or a fibre optic connector. <IMAGE>

Description

SPECIFICATION Push-pull connector Technical field The present invention relates to a connecting device of the "push-pull" type. The device preferably includes first and second connectors. One of the first or second connectors has an axial sleeve which is movable between a central locking position for locking the first and second connectors together and two unlocking positions.

Background of the prior art The connecting devices of the "push-pull" type are already known especially electrical connectors.

"Push-pull" connectors are currently used for connecting coaxial cables.

The U.S. Patent No. 4,017,139 describes a female connector element including an external movable sleeve, coaxially sliding on a cylindrical body, housing at least one electrical contact member as well as a spring for automatically restoring the said sleeve into a central locking position, which corresponds to the connecting position of the female connector with a complementary male connector. The spring is a spiral spring, coaxially arranged between the said cylindrical body and the external movable body.

This known device necessitates the production and the preparation of the spiral spring, which may lose at least one part of its elasticity.

The present invention is directed to a "push-pull" connector of simple and economical construction, having no spiral spring for the restoration of its external sleeve into its locking position.

Briefsummary of the invention The invention is defined in the appended claims to which reference should now be made.

A preferred connecting device embodying the invention includes at least one connector having a body and an axial sleeve movable on the body between a central locking position and two unlocking positions. Means are provided for the restoration of the axial sleeve to its central locking position from either unlocking position. This restoration means includes an open V-shaped groove in the body of the connector, the groove having two inclined surfaces whose total width is at least equal to the travel of the axial sleeve on the body. The restoration means also includes a spring means forming a crown at least partially encircling the axial sleeve and elastically disposed toward a resting position at the bottom of the V-shaped groove.

In accordance with the preferred embodiment, the device includes a V-groove arranged at the periphery of an interior cylindrical sleeve of the body of the connector, and the spring means are integral with the exterior axial sleeve. In accordance with another embodiment, the V-groove is arranged at the internal surface of the external axial sleeve, and, the spring means, in this case, are integral with the interior cylindrical sleeve.

In one especially interesting embodiment, the spring means includes a split ring, stressed by its elasticity to adopt a position where its diameter is minimal, which is housed in a U-groove arranged opposite to the Groove. The ring is dimensioned in such a manner that in its resting position it is partially housed in the V-groove, resting against the bottom of the latter, and partially housed in the U-groove, guided by its lateral walls. In this manner, when the time when the axial sleeve is pushed toward the connecting front surface of the connector, or pulled in the opposite direction, the ring, resting on one or the other of the lateral inclined surfaces of the V-groove is forced open and penetrates further into the U-groove as it rides up the inclined surface.

This U-groove preferably has a depth at least equal to the thickness of the ring in the radial direction. In order to facilitate the gentle sliding of this ring on the inclined surface formed by the inclined surfaces of the V-groove, it preferably has a rounded surface on its side opposite to the Ugroove, that is to say, on its side intended to take rest on the lateral sides of the V-groove.

In accordance with one particular embodiment, the ring has a toroidal shape.

In the case where the V-groove is arranged at the interior surface of the exterior axial sleeve, the split ring will be of the type prestressed by stretching, that is to say, it will have a tendency to adopt a position where its diameter is maximal.

In accordance with another embodiment of the device in accordance with the invention, the spring means include a series of axial elastic tongues, integral with the end of the external axial sleeve opposite to the connecting front surface of the connector element. These tongues are arranged around the periphery of the internal sleeve and include a rounded protuberance at their respective ends. These protuberances are arranged to rest on the sides of the V-groove, and are prestressed in such a manner that they have a tendency to adopt a resting position in which the crown composed of these proturberances has a minimal diameter This resting position coincides with the locking position of the external sleeve and occurs when the protuberances engage the bottom of the V-groove.These tongues have a tendency to return into this resting position when the sleeve is manually pushed beyond its locking position in the direction of the connecting front surface of the connector element or at the time when the sleeve is pulled in the opposition direction, because the crown of protuberances bear on the lateral inclined surfaces of the V-groove.

These tongues can be either machine-finished in one piece with the external cylindrical sleeve, or joined with this sleeve by known means.

An advantageous application of the connecting device in accordance with the invention consists of providing an electrical connector, one of the two connector elements of which, male or female, includes the means for restoring the external sleeve into its central locking position, such as previously described.

Another advantageous application consists of using the device in accordance with the invention for connecting at least two sections of optical cable.

The V-groove working together with the spring means, can be adapted, by selection, to the male connector element or female connector element.

With a connector which comprises a toroidal spring which is theoretically in contact with at least one wall of the V-groove, along a continuous circular line, when the exterior sleeve member is moved with respect to the interior sleeve member, the friction of the spring on the walls is relatively considerable. It is preferred therefo to ameliorate this slight inconvenience by making a device in which this friction is reduced, and whose manufacture requires standard elements, currently used and consequently available at relatively modest prices.

With this aim in mind, the said spring means may comprise a slit ring obliged by its elasticity to adopt a position in which its diameter tends to become minimal, and a series of protuberant members placed at regular intervals in contact with the interior surface of the slit ring, these protuberant members bearing against one or the other of the lateral walls of the V-groove provided on the peripheral wall of the interior sleeve member.

The protuberant members are conveniently constituted by independent spherical balls and the slit ring may be a flat spring whose elastic coercions tend to tighten this ring and push the balls towards its centre.

However, the protuberant elements could also be solid with the slit ring and mounted on the interior surface of the latter. In this case, they comprise a rounded end to facilitate the sliding on the walls of the V-groove. The slit ring is preferably located in a U-groove open towards the outside of the exterior sleeve member and the protuberant members are preferably fitted in openings crossing the bottom of this groove to allow said protuberant members to bear against the lateral walls of the V-groove.

In this arrangement the width of the U-groove is at least equal and preferably slightly larger than the width of the slit ring, the diameter of the protuberant members is at least equal and preferably slightly smaller than the diameter of the openings provided in the bottom of this groove, and the diameter of these openings is desirably as equal as possible and preferably slightly smaller than the width of the U-groove.

Brief description of the drawings The present invention will be better understood in reference to the following detailed description given by way of example when read in conjunction with the drawings in which Figure 1 is a section view of one male connector element of a connector device embodying the invention; Figure 2 is a partial section view of another embodiment of a male connector element of a device; Figure 3 is a partial section view of an embodiment of a female connector of a device; Figure 4 is a partial view of another embodiment of the connectors of Figures 2 and 3;; Figure 5 represents a longitudinal cross section of another connector element embodying the invention, the top part of this view illustrting the connector ready to receive a complementary connector element and the lower half illustrating this connector element in the locking position; Figure 6 represents a partial view of a modification of the connector element of Figure 5, and Figure 7 is a view from above of the slit ring illustrated by Figure 6.

Detailed description of the invention With reference to Figure 1, the depicted male connector element 1 has a ring-shaped body including an internal cylindrical sleeve 2, and an external cylindrical sleeve 3, axially movable with respect to sleeve 2. An insulating block 4 is disposed in the interior of sleeve 2, the peripheral surface of which is preferably cylindrical, and which has at least one electrical contact memberS, disposed in an appropriate axial bore. The contact member 5 includes an end plug 6, for connection with a complementary female element (not shown), a central section 7 for maintaining the plug in place in the central axial bore of the insulating block 4, and a connecting member 8 for receiving and fixing an electrical conductor thereto.The plug 6 and the connecting member 8 are respectively located at the interior of two recesses 9 and 10, arranged in the insulating block 4, on both sides of the central bore containing the central section 7 of the contact member 5.

The internal sleeve 2 includes a supporting ringshaped piece 11, mounted on insulating block 4. It may be mounted, for example, by screwing down its frontal end 12 on a metallic sleeve 13 which is placed at the periphery of the insulating block 4 from the side of the connecting frontal surface of the connector element 1. Moreover, the internal sleeve 2 includes a ring-shaped piece 14 preferably mounted coaxially on support piece 11 by being screwed thereon. Piece 14 includes a crown of elastic tongues 15 arranged around the periphery of the metallic sleeve 13. Each of these tongues includes a first radial boss 16 directed towards the main axis "A" of the connector element 1. The first bosses 16, in use, penetrate the interior of a complementary ringshaped groove (not shown) arranged at the periphery of a female connector element connectable with the shown male connector male element.

Each tongue 15 has a second radial boss 17 directed towards exterior sleeve 3. The second bosses 17 cooperate with a cam surface 18, arranged along the interior front surface of the sleeve 3. The cam surface 18 has two zones of smaller thickness 19 and 20, and a shoulder diposed between zones 19 and 20. As will be seen, the shoulder 21 causes the elastic tongues 15 to clamp in their locking position.

At the time when the sleeve 3 is manually pushed in the direction of the connecting front surface of the connector element 1, the zone of smaller thickness 20 is moved opposite the second bosses 17 of tongues 14, and allows these tongues to move radially away from axis "A" so that the crown formed by the set of tongues 15may slacken by enlarging its diameter to permit the penetration of a female connector element connectable to the male connector element 1. In a similar manner, when the external sleeve 3 is manually pulled in the opposite direction to the connecting front surface of the connector element 1, the zone of lesser thickness 19 places itself opposite the second boss 17, which permits to disengagement of the female connector element, initially connected with the male connector element 1.

The internal sleeve 2 is provided, at its peripheric frontal surface, with a very open annular groove 22, in the shape of a V, the lateral partitions of which define two inclined planes 23 and 24 which are inclined in regard to axis "A" of the connector element. The bottom of the groove constitutes a zone of a minimal diameter of the interior sleeve 2.

The exterior sleeve 3, on its end which is remote from the connecting frontal surface of the connector element 1, has a series of elastic tongues 25 arranged in a parallel manner with respect to axis "A" of the connector element, and in the crown around the peripheral surface of the interior sleeve 2.

Each one of these tongues 25 has a protuberance 26 and are prestressed toward the elongated axis of the connector element, in such a manner that the protuberances 26 are lodged at the bottom of the groove 22. The crown formed by the set of protuberances 26 disposed at the respective ends of the tongues 25 tends to adopt a position where its diameter is minimal. In this manner, when the external sleeve 3 is manually pushed in the direction of the connecting frontal surface, the protuberances 26 of the elastic tongue 25 are displaced on the inclined surfaces 23 of the V-shaped groove 22 causing them to deflect outwards. Thus tongues 25 serve as spring elements.Since the maximal opening of the groove 22 is larger than the travel of the external sleeve 3, the protuberances 26 stay in contact with the inclined plane 23 as the exterior sleeve 3 is pushed as far as it is free to travel in the direction toward the front surface of the connector element. In this manner, when the operator releases the exterior sleeve 3, the elasticity of the tongues 25 permits protuberances 26 to slide down inclined surface 23, and thereby cause sleeve 3 to return to its locking position where the protuberances 26 are located at the bottom of the groove 22.In a similar manner, when the time when the external sleeve 3 is pulled to allow disengagement (previously described) of a female conductor element connected to male connector element 1, the protuberances 26 slide on the inclined surface 24 of the V-shaped groove 22, in a manner to deflect or load the springs comprised by tongues 25. As before, when the operator releases the external sleeve 3, the elasticity of the tongues 25 pulls sleeve 3 back into its locking position, that is to say, into a position where the protuberances 26 rest at the bottom of groove 22.

At the end adjacent to the connecting front surface the exterior sleeve 3 preferably has an annular protuberance 27, for facilitating the guidance and the axial maintenance of the female donnector element with the male connector element 1.

In the above described example, the connector 1 has two elements or a group of elements insulated from each other in order to provide an electrical connecting function. The first element is formed by the central contact 5. The second element is formed by the metallic sleeve 13, connected to the annular support piece 11 by its frontal end 12 and by the elastic tongues 15. The insulating block 4 ensures insulation between these two groups of conductor elements.

Figure 2 depicts another male connector element 31, the general construction of which is very similar to that of the male connector element 1, depicted in Figure 1. As previously, it includes a interior sleeve 2, an exterior sleeve 3, an insulating body 4 and a central contact memberS, very similar in their shape and their function to the corresponding elements of Figure 1.

The embodiment of Figure 2 differs from that of Figure 1 with regard to the mechanism allowing the external sleeve 3 automatically seek its locking position. In this embodiment, the external sleeve does not have elastic tongues, but rather has a split ring 32, lodged in a U-shaped groove 33, located in the thickness of the sleeve, and located opposite the V-shaped groove 22. The U-shaped groove has a width slightly larger than that of the ring 32, so that ring 32 can slide into groove 33, guided by its side walls. The split ring is prestressed to elastically adopt a position where its diameter is minimal. In this position, as shown in Figure 2, the ring 32 is located at the bottom of the groove 22, and is partially lodged in the U-shaped groove 33.When the operator manually pushes the external sleeve 3 in the direction of the connecting front surface of the connector element 31, the split ring 32 which is rounded at least at its interior front surface and preferably has a toroidal shape, slides on the inclined surface 23. Consequently, this action causes the ring to penetrate further into the groove 33, and at the same time provides a spring action by elastically increasing its diameter. When the external sleeve is subsequently released, the elasticity of the ring exerts a restoring force having an axial resultant which tends to urge ring 32 back towards the bottom of the groove 22. In a similar manner, when the external sleeve is pushed in the direction opposite to the connecting front surface of the connector element, the split ring 32 slides on the inclined surface 24 enlarging its diameter.When it is released, its elasticity tends to restore it into position where its diameter is minimal, that is to say, at the bottom of the V-shaped groove 22. Of course, this device also causes the external sleeve 3 to automatically restore to its central locking position.

Figure 3 is a view of a female connector element 41, which utilizes the same principle as that which has been described in reference to Figure 2. This connector element includes an external sleeve 3 and an internal sleeve 2, an insulating block 4 and having a V-shaped groove 22. A U-shaped groove 33 is arranged in the external sleeve 3 for receiving an elastic ring 32. This ring, as in the previous example, is prestressed in such a manner as to automatically return into a central locking position, that is to say, into a position in which its diameter is minimal and where it is lodged at the bottom of the V-shaped groove 22.

As is shown in Figure 4, it is also possible to inverse the positions of the V-shaped groove and the split ring. In this case, an inverted V-shaped groove 22 is arranged at the interior of the external sleeve 3, and a U-shaped groove 33 is arranged at the periphery of the internal sleeve 2. However, in this case the ring 32 is prestressed in such a manner as to have the tendency to expand, that is to say, of constantly returning into a position where its diameter is maximal.

The modification illustrated by Figures 5 to 7 will now be described.

With reference to Figure 5, the connector element 51 illustrated comprises a ring-shaped body 52 hereinafter called the interior cylindrical sleeve member and an exterior cylindrical sleeve member 53, axially movable with respect to the sleeve member 52. Inside the interior sleeve member 52 are mounted different elements (not shown) which are strictly identical to corresponding elements, described and represented in the previous Figures.

Similarly, the interior sleeve member 52 is comprised essentially of a ring-shaped support 54 and a ring-shaped sleeve 55, mounted for example by screwing at the front end of the ring-shaped support 54. This sleeve 55 comprises a ring of elastic tongues 56, mounted parallel to each other and parallel to the main axis of the connector element, at the front end of the cylindrical sleeve 55. Each one of these tongues comprises a protuberance 57, which cooperates either with a ring-shaped groove 58 provided on the interior side of the exterior sleeve member 53, or with a ring-shaped protuberance 59, adjacent to groove 58, to ensure respectively the unlocking (see top part of Figure 5) and the locking (see the lower part of the connector on Figure 5) of the exterior sleeve member 53.

The exterior sleeve member 53 further comprises a U groove 60 the bottom 61 of which is crossed by openings 62, preferably circular, provided at regular intervals all round the interior surface of this sleeve member. In the cavities 62 are located spherical balls 63, the diameter of these balls being such that their upper surfaces are in contact with a flat ring-shaped spring 64 which is in the form of a slit ring, and that their lower surfaces bear against at least one of the lateral walls of the V-groove 65 with which the interior sleeve member 52 is provided. The slit ring 64 tends to push the balls towards the centre. The U-groove had a width slightly smaller than that of the flat spring 64, to allow this spring to move readily in this groove.Moreover, the balls have a diameter slightly smaller than that of the circular openings 62, to allow the balls to move radially under the influence of the spring 64. The openings 64 have preferably a diameter smaller or equal to the width ofthe U-groove.

In practice, the device is generally similar to that of the previous Figures. When the operator pulls (or pushes) the exterior sleeve member 53 out of its locking position (represented by the lower part of Figure 5), the balls 63 slide or roll on one (orthe other) of the lateral walls of the groove 65, creating an extension of the flat spring 64 which is charged.

When the operator releases the exterior sleeve member 53, the spring resting on the balls 63, creates a pushing movement which tends to bring the balls back to the bottom of the groove 65, driving the exterior sleeve member 53 towards its locking position.

Figure 6 represents a variant in which the flat spring 64 and the independent balls 63 have been replaced by a unitary part 70 made up, as Figure 7 shows in more detail, of a spring plate 71 which constitutes the slit ring, provided, on its interior side with protuberances 72 with rounded ends which rest against at least one of the lateral walls of the V-groove 65 provided at the periphery of the interior sleeve member 52.

Protuberances 72 have the same function as bails 63 of the previous example. In a similar way, the slit ring 71 has the same function as the slit ring 64 of Figure 5. Protuberances 72 can be made from one piece with the slit ring 71 or adapted by any appropriate known means.

Those skilled in the art will appreciate that the embodiment disclosed show the use of the present invention in connection with the electrical type connectors. The invention is not limited to use with electrical type connectors; it can also be used in other applications as well. For example, the male contact member 5 of Figures 1 and 2 or the corresponding female member of Figure 3 may be easily replaced with equivalent fibre optic structures and the resulting connectors will still function in the "push-pull" manner described herein. Additionally, having described the invention in connection with certain specific embodiment thereof, further modification may now suggest itself to those skilled in the art. It is to be understood that this invention is not limited to the specific embodiments disclosed.

Claims

1. A push-pull connecting device for connecting a first connector element with a second connector eiement, said first connector element having mechanical means arranged for allowing the connection of the first and the second connector elements and for clamping them in a connected position, said mechanical means including: an external cylindrical sleeve axially movable between a central locking position and two unlocking positions arranged on both sides of the central position; and internal sleeve having a cylindrical shape, disposed coaxially to the external sleeve and provided with a series of eleastic tongues axially extending in the direction of a connecting end of the said first connector element, each one of these tongues including connecting members arranged for co-operation with complementary connecting elements on the second connector element when the two connector elements are connected together; an externally directed radial boss arranged for cooperation with a cam surface disposed on the interior of said external sleeve for effecting the locking and for allowing the unlocking of the second connector element with respect to the first connector element; and means for automatically restoring the external cylindrical sleeve into its central locking position, said restoring means including an open V-shaped groove, said groove forming two inclined surfaces on the sides of said groove, the width of the groove being at least equal to the travel distance of the movable external sleeve between the two unlocking positions, and spring means encircling at least partially the internal sleeve and being urged by their elasticity towards a rest position at the bottom of the V-shaped groove, said spring means being mounted in relation to the internal sleeve and the external sleeve in such a manner that the rest position of said spring means coincides with the locking position of the external sleeve.

2. The device as claimed in Claim 1, wherein the V-shaped groove is arranged at the periphery of the cylindrical internal sleeve and wherein the spring means are integral with the cylindrical external sleeve.

3. The device as claimed in Claim 1, wherein the V-shaped groove is arranged at the internal surface of the external cylindrical sleeve and wherein the spring means are integral with the internal cylindrical sleeve.

4. The device as claimed in Claims 1 or 2, wherein the spring means comprises a split ring, stressed by its elasticity to adopt a predetermined position, said ring being lodged in a U-shaped groove disposed opposite to the V-shaped groove, and being dimensioned in such a manner that in its resting position it is partially lodged in the V-shaped groove leaning against the bottom of of the groove and partially lodged in the U-shaped groove, and guided by the side walls of the U-shaped groove and wherein, in use, the ring, when engaging on one or the other of the lateral inclined surfaces of the V-shaped groove, penetrates further into the Ushaped groove in response to the sleeve being manually pushed toward one or the other of its two unlocking positions.

5. The device as claimed in Claim 4, wherein the U-shaped groove has a depth at least equal to the thickness of the ring in a radial direction.

6. The device as claimed in Claim 4, wherein the ring has at least one rounded surface on its side facing the V-shaped groove, in order to permit gentle sliding on the inclined surfaces.

7. The device as claimed in Claims 4, wherein the split ring as a toroidal shape.

8. The device as claimed in Claims 1 or 2, wherein spring means include a serial of axial elastic tongues, integral with the end of the external sleeve opposite to the connecting front surface of the first connector element, said tongues being located all around the periphery of the internal sleeve, including, attheirfree end, a rounded protuberance arranged for resting on the V-shaped groove, and being prestressed in such a manner that they seek a resting position in which the crown formed by these protuberances has a minimal diameter, said resting position of the crown of protuberances coincidence with said locking position.

9. The device as claimed in Claim 8, wherein the tongues are integral with the external cylindrical sleeve.

10. The device as claimed in Claim 8, wherein the tongues are join with the end of the external cylindrical sleeve opposite to the connecting front surface of the said first connector element.

11. The device as claimed in Claim 1,wherein the first connector element includes guidance means, integral with the end of the external sleeve adjacent to the connecting front surface, for guiding the second connector element in place for increasing its lateral stability.

12. The device as claimed in Claim 11,wherein the elastic tongues each include an internally directed boss, said guidance means includes an annular protuberance disposed at the frontal end of the external sleeve, the internal diameter of this protuberance being essentially equal to the internal diameter of said internally directed boss of said elastic tongues.

13. The device as claimed in Claim 1, wherein the first connector element is an electrical male connector and wherein the second connector element is a female connector element.

14. The device as claimed in Claim 1, wherein first connector element is an electrical female connector element and the second connector element is a male connector element.

15. The device as claimed in Claims 13 or 14, wherein the said first and second connector elements each include an insulating block at least partially mounted at the interior of a cylindrical sleeve, and at least one electrical contact member lodged in the said insulating block, the electrical members of the first and of the second connector element being complementary and arranged in such a manner that they are electrically connected when the two connector elements are connected.

16. The device as claimed in Claim 1, wherein the said spring means comprise a slit ring stressed by its elasticity to adopt a position in which its diameter tends to become minimal, and a series of protuberant members at regular intervals on the interior surface of the slit ring, these protuberant members bearing against one or the other of the lateral walls of the V-groove provided on the peripheral wall of the interior sleeve member.

17. The device as claimed in Claim 16, wherein the slit ring is located in a V-groove which is open towards the outside of the exterior sleeve member, and the protuberant members are fitted in openings crossing the bottom of this groove to allow said protuberant members to bear against the lateral walls of the V-groove.

18. The device as claimed in Claim 16, wherein the protuberant members are mounted on the interior surface of the slit ring and comprise a rounded end to facilitate their sliding on the walls of the V-groove.

19. The device as claimed in Claim 16, wherein the protuberant members are constituted by independent spherical balls and in that the slit ring is a flat spring whose elastic coercions tend to tighten this ring and push the balls towards its centre.

20. The device as claimed in Claim 19, wherein the width of the V-groove is at least equal and preferably slightly larger than the width of the slit ring, in that the diameter of the balls is as equal as possible and preferably slightly smaller than the diameter of the openings provided in the bottom of this groove and in that the diameter of these openings is as equal as possible and preferably slightly smaller than the width of the Groove.

21. A push-pull connecting device substantially as herein described with reference to Figures 1 to 3 of the drawings taken with or without Figure 4.

22. A push-pull connecting device substantially as herein described with reference to Figures 5 to 7 of the drawings.