GB2089475A

GB2089475A - Rotary couplings

Info

Publication number: GB2089475A
Application number: GB8137330A
Authority: GB
Original assignee: QUALITY INSPECTION SERVICES LT
Current assignee: QUALITY INSPECTION SERVICES LT
Priority date: 1980-12-12
Filing date: 1981-12-10
Publication date: 1982-06-23
Also published as: IT1140133B; IT8125551A0; FR2496203A1

Abstract

A coupling between elongate members (2) comprises a connector (10) having a web (14) and two spaced beads (12) thereon which extends between complementary recesses or slots (6) formed in the end faces (4) of the members (2). The beads are retained in enlargements (8) at the bases of the recesses (6). The coupling can be used to hold two members (2) in close end to end engagement as shown and/or to provide torsional flexibility e.g. to provide a universal joint. It is possible, according to the invention, to provide flush joints which do not increase the overall cross-section of the coupled members, facilitating replacement and repair of worn parts. The members (2) may comprise shafts or rollers. The coupling may be utilised in a gear train to prevent backlash. <IMAGE>

Description

SPECIFICATION Couplings The present invention relates to coupling techniques for connecting the ends of elongate members such as shafts or guide-track rollers.

Particularly, the invention contemplates such a connection which does not encroach on the space around the members and which enables a flush joint to be made, particularly where the members are of circular cross-section.

Known methods of connecting the ends of shafts, such as flange connections or muff-type couplings, result in an increased overall diameter or section in the region of the connection. Apart from the loss of a smooth external surface, this increase prevents the passage of a close fitting bearing or gear for example past the joint. Such a bearing or gear cannot normally be located at the joint, and the joint may frequently occupy a substantial length of the coupled shaft or track.

The prior techniques also involve installation and operational problems. The additionai bulk of the coupled shaft can result in difficulties in assembly where space is at a premium; and maintenance can be complicated as the enlarged coupling reduces manoeuvrability of the shaft within an installation.

The present invention seeks to alleviate the above problems and providing a coupling technique which enables a joint to be made between juxtaposed ends of aligned members, which technique is suited to a number of types of coupling. In a coupling according to the invention between substantially aligned elongate members, a connector comprising a web and two spaced beads thereon extends between complementary recesses formed in the juxtaposed ends of the members, each recess being enlarged at its base to receive a respective bead therein. The connector is typically of a dumbell type crosssection.

In one variant of the invention, the elongate members abut each other, and the connector serves to hold the ends in abutting engagement. in order to ensure that the abutting ends are held securely in place, the connector is preferably under stress, such stress having been generated as the connector is positioned. For example, the connector might be formed in spring steel, its web being normally curved and requiring straightening as it is positioned. In an alternative, the enlarged edges might be wedge-shaped, putting the web under tension as the connector is forced home.

Alignment of the member ends can be assured by providing a mating projection and recess on the abutting faces. Shafts coupled according to this variant of the invention can be used as rollers in roller tracks with the advantage that they can pass through bearings and access openings without having to take account of any enlarged joints. This is particularly beneficial when replacing or repairing rollers, the invention enabling the replacement of a worn portion only of a roller, not the entire part. Similar advantages of course accrue in other applications.

According to another variant of the invention, the member ends are spaced from one another, the web being deformable and defining a degree of torsional flexibility between the members.

Additionally or alternatively, the recesses may be enlarged towards the end faces of the respective members to permit a degree of deformation of the web therein. Torsional resilience may be provided by using a connector having a web which is resiliently deformable. This may be exploited in a gear train to provide anti-backlash characteristics by twisting two coupled shafts relative to one another before gears supported on the shafts are meshed with a common pinion. A connector which is twisted in its equilibrium shape can be used to form a universal joint, more particularly suited to light duty work.

The invention enables a joint to be made without any projections, the connector being wholly within the periphery of the joined shafts or tracks. This characteristic enables the location of a connection within the confines of a bearing. Thus, at least insofar as location is concerned two or more connected shafts may be considered as a single element. The location of such a connection in a bearing can also enhance the stability of the connection. However, the connector may be formed with an extension, for example from its web, which can act either as a Icey for a component to be mounted on the shafts or some other securement. Such an extension may also be adapted to cut a keyway in a part forced thereover.

The joint of the invention is primarily intended for light or medium duty couplings, but can be satisfactory in certain heavy duty applications. For some light duty work, the connector may be formed of rubber or a plastics material which is cast in place, the shafts being held together until the rubber is cured. One of the various R.T.V.

(room temperature vulcanizing) silicon rubbers can be suitable. A preformed rubber or plastics connector can also be adequate in some circumstances. These techniques have the advantage of requiring less accuracy in the formation of the recesses. Normally though, and particularly for heavier duty work, the connector will be preformed, in metal.

Various embodiments of the invention will now be described by way of example and with reference to the accompanying drawings wherein: Figure 1 is a perspective view of a coupling according to one embodiment of the invention; Figure 2 is a perspective view of an alternative form of connector for use in the embodiment of Figure 1; Figure 3 is a longitudinal section of another embodiment according to the invention; Figure 4 is a plsn view of the connector shown in Figure 3.

Figure 5 is a sectional view of a gear train incorporating another embodiment of the invention; Figure 6 shows a variation of the embodiment of Figure 5; and Figure 7 illustrates an universal joint embodying the invention.

The joint shown in Figure 1 is made between two shafts 2 having planar faces which abut at 4.

Extending from each face is a slot 6 which is enlarged at its base 8. The two slots 6 are aligned when the shafts 2 are brought together to define a channel for receiving a connector 10.

The connector 10 is formed from a plate of spring steel folded at two opposed edges to form two parallel beads 12 joined by a web 14. The web 14 is curved in its unstressed state defining a spacing between the beads 1 2 less than that between the slot bases 8 in the channel defined by the aligned slots 6 of the shafts 2. Thus, the web 14 of the connector 1 0 must be straightened as it is inserted into the channel, and once in place resiliently urges the shafts 2 together.

When in place, the connector 10 will be wholly received in the channel, leaving a smooth continuous external surface of the joined shafts Normally, the slots 6 will extend through the entire cross-section of the shafts 2, enabling the connector to be introduced or removed from both sides, but they may terminate short of one side if desired. The precise cross-section of the connector 0 and the slots 6 is of course not critical and might be symmetricai, in which case termination of the slots 6 short of one side can be valuable if the relative orientation of the joined shafts must be predetermined.

If desired, the connector may be used to provide a key on the periphery of the joint. The connector may have a projection attached which protrudes from the peripheral surface of the joined shafts when installed. An example is shown in Figure 2 in the form of an extension 16 from web 14. The extension 1 6 tapers away from the web 14 to form a cutting edge which may be used to cut a keywayin a part forced past the joint. It can be beneficial, where this feature is adopted, if the depth of the channel is limited, as this facilitates predetermination of the depth of any cut made by the extension 1 6. Of course, other forms of projection may be used. For example, one may be adopted which functions both as a key if desired and a tab with which to withdraw the connector when the joint is to be dismantled.A projection might also be formed from one or both of the beads 12. If, for example, a bead is extended at one or both ends, it can usefully form a stop or locating feature against which a bearing or gear can be located.

The joint shown in Figure 1 has the channel located substantially across a diameter of the shafts 2. This is best suited to light duty joints where torsional and bending stresses are not great; A joint better suited to heavier duty work is shown in Figure 3. In this embodiment the channel is located to one side of the joint, alignment of the shafts or tracks 2 being assured by a pin 1 8 projecting from one shaft or track 2 received in a socket 20 in the other. Further, the connector 10, is a solid, normally metal body 22 having wedgeshaped beads 24 on either side of a flat web 26.

The taper on the beads 24 is typically about 40 (included angle), as shown in Figure 4, the connector being forced into the channel to urge the two shafts 2 together. The connector 10 in this embodiment is dimensioned to be a close fit at and around the enlarged bases 8 of the slots 6, clearance being provided at the mouths of the slots as shown. As in the first embodiment described, a projection from the web may be included to form a key and/or a removal tab as desired. This second embodiment particularly permits the deployment of a jacking screw or fitment therefor.

Where a degree of flexibility between connected members is desired, a joint may be made in which a gap is maintained between the juxtaposed ends of the respective members. This is illustrated in Figure 5 where the joint is used in a standard gear train to provide anti-backlash characteristics. Each shaft member 28, 30 supports a respective gear 32, 34 which both mesh with a pinion 36. The gears are loaded by simply twisting one in relation to the other by an appropriate amount against the resilience of the connector 38 before meshing with the pinion 36.

Such an arrangement provides an inexpensive means by which a frequently recurring design requirement can be met. In some applications, for example with very fine pitch gears 32, 34, the gap can be reduced and the requisite space for twisting of the connector 38 provided in slots 40 formed in one or both juxtaposed ends of the shaft member 28, 30, as shown in Figure 6.

A twisted connector might also be used to form an universal joint suitable for light duty, between shaft members as shown in Figure 7. In this case though, the connector 38 has a twisted orientation in the unstressed state, and accommodates axiai misalignment of the shaft members 28, 30 by deforming from that orientation. In each of the embodiments of Figures 5, 6 and 7, the connector 38 is preferably formed of sprung steel and is generally similar to that shown in Figure 1 with the web 14 substantially planar.

As stated above, the metallic connectors illustrated may be replaced by rubber or plastics components. Such components may be preformed, or cast in situ to make the joint. A plurality of alignment pins may be used to assure torsional rigidity where space permits, allowing the use of less rigid connectors where axial or bending forces are less prevalent. The use of a rubber or plastics connector of course reduces the accuracy required in machining the slots 6.

Claims

1. A coupling between substantially aligned elongate members wherein a connector comprising a web and two spaced beads thereon extends between complementary recesses formed in the juxtaposed ends of the members, each recess being enlarged at its base to receive a respective bead therein.

2. A coupling according to Claim 1 wherein the ends of the members abut each other, and wherein the connector serves to hold the ends in abutting engagement.

3. A coupling according to Claim 2 wherein the web of the connector is resiliently deformed from its equilibrium shape, such resilience urging the member ends towards one another.

4. A coupling according to Claim 2 wherein the equilibrium shape of the web is curved, it having been flattened as the connector is located in the coupling.

5. A coupling according to Claim 2 or Claim 3 wherein opposed faces of the beads on the connector are convergent, and cooperate with the enlarged recess bases to urge the member ends together as the connector is located in the coupling.

6. A coupling according to any preceding Claim including a locking pin extending between sockets in the juxtaposed member ends to inhibit relative rotation of the members.

7. A coupling according to any preceding Claim wherein a projection extends from the connector to protrude from a lateral surface of the coupling.

8. A coupling according to Claim 8 wherein the projection comprises an extension of the connector web.

9. A coupling according to Claim 1 wherein the member ends are spaced from one another, the web being deformable and defining a degree of torsional flexibility between the members.

10. A coupling according to Claim 1 or Claim 9 wherein the recesses are enlarged towards the end faces of the respective members to permit a degree of formation of the web therein.

11. A coupling according to Claim 9 or Claim 10 wherein the web is resiliently deformable.

12. A coupling according to any of Claims 9 to 11 wherein the web is twisted in its equilibrium shape.

13. A universal joint comprising two members coupled by means of a coupling according to Claim 12.

14. A gear train comprising a pair of coaxial gears meshing with a common pinion, the gears being coupled by means of a coupling according to any of Claims 9 to 12.

15. A gear train according to Claim 14 using a coupling according to Claim 11 wherein the gears have been twisted relative to one another prior to meshing with the pinion.

16. A coupling between elongate members substantially as described herein with reference to Figures 1 and 2; Figures 3 and 4; Figure 5; Figure 6 or Figure 7 of the accompanying drawings.