GB2116671A - Rotary shaft coupling - Google Patents

Abstract

A coupling between rotary shafts 11, 12 allows limited relative rotation against a variable resistance. The coupling includes collar members 13, 14 affixed one to each shaft and projecting therefrom, the members having pads 55 to which air spring bags 56 are affixed with each bag entrapped between a pad from each shaft. The pad arrangements are alternated so that alternate air bags are compressed and expanded upon relative rotation in one circumferential direction. In this manner alternate air springs will resist rotation in alternate relative directions. The air bags have inflation nipples 80 and can be adjustably inflated so that the resistance to relative rotation is controllable and so that a predetermined relative positional rotational difference between the two shafts can be adjustably set. Stops 87 may limit relative rotation. <IMAGE>

Description

SPECIFICATION A shaft coupling resistant to relative rotation between the coupled shafts This invention relates to shaft couplings and, more particularly, to relative rotation resistant shaft couplings.

Couplings for connecting together two shafts are widely used. Such couplings generally fall into three distinct categories, those allowing no relative rotation between the shafts, such as splined couplings, those allowing total freedom of rotation between the shafts, such as bearing couplings, and those which allow some limited amount of relative rotation. In the third category devices such as friction clutches, friction brakes and the like, produce an initial resistance to rotation while devices utilising springs and the like produce a substantially constant resistance to relative rotation.

A further type of rotation resistant coupling has also been known which employs compressible elastomer members between spaced shaft projections on the shafts being coupled. In such devices rotation of one shaft relative to the other shaft will initially cause a compression of the elastomer members.

Shaft rotational force (torque) can be transmitted through the compressed members and the resistance to compression of the elastomer will tend to realign the shafts to the preset normal position.

While such relative rotation resisting couplings are useful in many instances, they have a disadvantage in that the amount of resistance per increment of relative rotation is predetermined by the nature of the chosen elastomer or spring. Thus, once such a coupling has been installed, further adjustment to facilitate changing environmental conditions is not practical. Moreover, due to the use of fixed dimensional springs or elastomer members, the initial set position of the two shafts with respect to one another cannot be altered and the coupling will always act to return the two shafts to that initial position.

It would therefore be an advance in the artto provide a relative rotation resistant shaft coupling where the resistance to relative rotation increases as a function of the relative displacement of the two shafts, where the resistance increase is adjustable and where the initial or rest position of the shafts could be easily modified.

According to the invention there is provided a shaft coupling comprising first and second shaft attachment members for attachment to shafts to be coupled, each of said members having a plurality of circumferentially spaced radial projections, circumferentially spaced inflatable air bags each interposed between and affixed to two said projections of the members respectively and effective to rotationally couple the members, a first set of said bags being compressed by torque transmission through the coupling in a first rotational direction and a second set of said bags being compressed bytorque transmission through the coupling in a second rotational direction and means for selectively inflating each of said air bags.

The following is a detailed description of an embodiment of the invention, reference being made to the accompanying drawings in which: Figure 1 is an end plan view of a variable shaft coupling according to the invention with underlying members shown by broken lines, Figure 2 is a part-sectional view taken along the line II - II of Figure 1, Figure 3 is an enlarged, fragmentary view of a circumferential portion of a flange of the coupling of Figure land Figure 4 is an enlarged, fragmentary view taken along the line IV - IV of Figure 1 showing a rotation limiting abutment stop assembly.

As best shown in Figures 1 and 2, the coupling includes a collar member 10 for attaching together the ends of a first shaft 11 and a second shaft 12. The collar member includes first 13 and second 14 shaft engaging base members. These are attached to the shaft by wedge locks 17 and 18 which are received in grooves 19 and 20 extending circumferentially.

Through bolts 21, when tightened, cause a wedging action to occur between the outer diameter of the grooves 18 and 19 and the outer diameters of the shafts to lock the members 13 and 14 to the shafts.

Thjstypeofconnection allows the members 13 and 14to be infinitely rotationally positioned to the shaft ends and thereafter locked in position. Other types of shaft attachments may, of course, be utilised if desired. Preferably, the shafts are bearing supported closely adjacent the collar aseembly 10 so as to prevent shaft end droop, although other methods of longitudinally supporting the shafts may be provided if preferred.

Each of the base members 13, 14 has an opposed axial end face 22. Adjacent the end face 22, at the outer diameter of the base members 13, 14, radially projecting ring portions 24 are attached, by means such as welding. Opposed flanges 30 and 31 are affixed to the axial ends of ring members 24 by bolts 25. The flanges 30 and 31 are provided with welded axial projections 27 at one axial end face of the flanges, the axial projections 27 having threaded axial bores therein for receipt of the bolts 25 from the rings 24.

In the preferred embodiment illustrated, the flanges 30 and 31 extend outwardly from the ring areas but terminate radially inwardly in closely spaced relation to the bolt attachments thereby providing a large open central area 40. The provision of this open central area allows access to the shaft clamps 18. In other embodiments it may be desired to minimise the radial projection of the flanges.

In the embodiment illustrated, which is designed for use with eight air bags, each of the flanges is provided with four radially outwardly extending projections. In the embodiment shown in Figure 1, with the view from the right-hand side of Figure 2 illustrating flange 30, the projections of flange 30 are numbered 50 with the aligned intermediate projections of the underlying flange 31 numbered -51. The projections of each flange are circumferentially spaced apart defining troughs 60 therebetween, as best illustrated in Figure 3 the troughs 60 are defined between circumferential radial walls 52 and 53 of the radial projections. The troughs 60 have a radial depth determined by the particular air bag being utilised.

The troughs 60 of one flange are aligned with the radial projections 50, 51 of the opposed flange so that in an axial direction each trough is backed, in its mid-reaches, by a projection of the opposed flange.

As best illustrated in Figure 3, on the circumferentially fore and aft walls 52, 53 of each projection, adjacent the outer diameter thereof air spring mounting pads 55 are attached by means such as welding. As best shown in Figure 2, the pads 55 are axially offset from the flanges so as to have centre sections thereof circumferentially axially aligned with centre sections of pads from the opposing flange. The pads 55 serve as mounting bases for air springs 56 with each sir spring 56 being entrapped between and mounted on pads of different flanges.

In this manner, as relative rotation occurs between the shafts, the pads of the opposed shafts will move towards or away from one another thereby compressing or expanding the air bag trapped therebetween.

Further, by providing that the projections of one flange are axially aligned with the troughs of the other flange, alternate air bags will, for any direction of relative rotation of the shafts be expanded and compressed.

In the embodiment illustrated in Figure 1, if the bags are numbered clockwise from the top, from 71 to 78, clockwise rotation of the flange 30 with respect to the flange 31 will compress air bags 72,74,76 and 78 while expanding bags 71,73,75 and 77. Alternatively counter clockwise rotation of flange 30 relative to flange 31 will compress air bags 71,73,75 and 77 while expanding air bags 72,74,76 and 78.

Air bags 56 are provided with inflation nipples 80 which may conveniently extend through the mounting pad 55 thereby allowing each of the bags 56 to be selectively inflated to a desired pressure. If desired air supply lines can be attached to the nipples and run along or through the shafts 11,12. Different lines may be provided for each bag set.

Since the resistance to compression of the air bags is determined by the inflation pressure, a predetermined range of torsional resistance can be set by adjusting bag inflation. Moreover, since resistance to bag compression increases with the degree of bag compression, the coupling can be set with a relative ly low resistance to slight amounts of torsional relative rotation while providing increased stiffness with increasing amounts of relative rotation.

For some types of air bags, as the bag is compressed, its diameter will increase thus increasing its effective area. When the bag is expanded or extended, the diameter decreases thus reducing the effective area. This variation in effective areas varies the spring rate.

Importantly, also, the relative rest or neutral position of shafts 11 and 12 can also be adjusted by means of inflation of the air bags. If the odd numbered air bags are inflated to a lower pressure than the even numbered air bags in the embodiment of Figure 1, the neutral position of shaft 11 with respect to shaft 12 can be rotated counter clockwise.

Alternatively, the neutral position can be rotated clockwise by increasing the inflation pressure of the odd numbered bags with respectto the even numbered bags. This feature can be very beneficial in situations where, due to wear causing slack or the like in equipment affixed to the shafts 11 and 12, a repositioning of the normal rotational relationship of the two shafts may be desirable. Through the use of a multiplicity of air bags, this adjustment can be accomplished without significantly effecting the torsional resistance characteristics of the overall coupling assembly.

Obviously the number, spacing and size of the chosen air bags will be determined by numerous factors including the applied torsional forces, the desired degree of relative rotation to be allowed between the shafts, space considerations and the like. Further, although the air bags are shown as being located at the radially outer periphery of the collar, in other constructions the bags may be located intermediate the inner and outer diameters of the collar, and in some instances, for example, when using large diameter shafts, can be located within the diameter of the shafts.

In order to provide an absolute relative rotational limitation, in the embodiment illustrated some of the troughs 50 are provided with intermediate radial projections 85 having radially extending abutment faces 86. The abutment faces 86 are opposable by abutment members 87 carried by the projections of the opposing flange. As best illustrated in Figure 4, the abutment projections 87 may be affixed axially offset to the flange projections so as to provide a radial abutment face 88 in direct opposition to the face 86. The face 88 may be formed on an abutment pad 89 affixable to the projection 87 by means such as a bolt 90. If desired, the pad 89 may be elastomeric. By means of the abutment provided between face 86 and 88, the relative degree of permissible relative rotation between the shafts is limited.

It can therefore be seen from the above that this invention provided a coupling for connecting together two shafts in a manner which allows a limited degree of relative rotation between the shafts to occur and wherein such relative rotation is increasingly resisted by means of compressible air bags which are selectively inflatable to control the tortional resistance curve. Additionally, the coupling provides for selective setting of the neutral or at rest position of the shafts with respect to one another.

Claims (12)

1. A shaft coupling comprising first and second shaft attachment members for attachment to shafts to be coupled, each of said members having a plurality of circumferentially spaced radial projections, circumferentially spaced inflatable air bags each interposed between and affixed to two said projections of the members respectively and effective to rotationally couple the members, a first set of said bags being compressed bytorquetransmission through the coupling in a first rotational direction and a second set of said bags being compressed by torque transmission through the coupling in a second rotational direction and means for selectively inflating each of said air bags.

2. Coupling according to claim 1, including relative rotation limiting abutment members carried by each attachment member.

3. A coupling according to claim 1 or claim 2, including means for affixing the attachment members to the shafts.

4. A coupling according to claim 3, wherein the means for affixing allows attachment of the attachment members at a plurality of circumferentially spaced positions on the shafts.

5. A coupling according to claim 4, wherein the means for affixing allows attachment of the attachment members at an infinite number of circumferentially spaced positions on the shafts.

6. A coupling according to any of claims 1 to 5, wherein the means for selectively inflating each set of air bags allows each air bag set to be inflated at different initial pressures from the bags of the other air bag set whereby a neutral relative rotational positioning of the two shafts can be adjusted.

7. A coupling according to any of claims 1 to 6, wherein said attachment members are adapted for attachment to shafts which are substantially axially aligned, and each radial projection comprising an air bag mounting pad, said pads of said first shaft attachment member lying in circumferential opposition to pads of said second shaft member, sets of two circumferentially oppositelyfaced pads of said first shaft attachment member being positioned between circumferentially opposed faced pads of said second shaft attachment member such that in a group of four circumferentially spaced pads, pads 2 and 3 are carried by said first shaft member and pads 1 and 4 are carried by said second shaft member, said inflatable air bags being attached to opposed faces of opposed pads between pads carried respectively by said first and second shaft attachment members, each air bag having opposite ends attached to a pad, a first bag end being attached to a pad carried by said first shaft attachment member and a second bag end being attached to a pad carried by said second shaft attachment member whereby during relative rotation of said first shaft attachment member with respect to said second shaft attachment member in a first circumferential direction said first set of said air bags will be compressed between said pads and said second set of said air bags will be expanded between said pads and during relative rotation of said first shaft attachment member with respect to said second shaft attachment member in a second circumferential direction opposite the first circumferential direction, said second set of air bags will be compressed and said first set of air bags will be expanded.

8. A coupling according to any of claims 1 to 6, wherein said attachment members are adapted for attachment to shafts which are substantially axially aligned and each radial projection comprising an air bag attachment pad, the pads of said first shaft attachment member lying in circumferentially opposition to the pads of said second shaft attachment member, each said air bag having first and second opposite ends, the first end of each air bag being attached to a pad carried by one of said shaft attachment members and the second end of each air bag being attached to a pad carried by the other of said shaft attachment members, said air bags being circumferentially spaced from one another, said first ends of circumferentially successive air bags being attached alternately to pads carried by said first and said second shaft attachment members whereby relative rotation of said first shaft attachment member with respect to said second shaft attachment member in a first circumferential direction will compress alternate air bags and expand interme'diate air bags between the alternate bags and relative circumferential rotation of said first shaft attachment member and said second shaft attachment member in a second circumferential direction opposite the first circumferential direction will compress said intermediate air bags and expand said alternate air bags.

9. A coupling according to any of claims 1 to 8, wherein said first and second shaft attachment members comprise first and second collar members which, in use, are affixed to shaft end portions adjacent ends thereof, first and second flange members being affixed respectively to said first and second collar members and extending circumferentially outwardly thereof, said flange members being relatively closely axially spaced from one another, each of said flange members including circumferentially alternating radial troughs and radial projections, air spring attachment pads being provided at the circumferential ends of said projections, and said flange members being aligned with one another whereby said projections of said first flange member lie circumferentially intermediate ends of troughs of said second flange member and the projections of said second flange member lie circumferentially intermediate ends of said troughs of said first flange member with said pads of said first and second flange members lying circumferentially opposed to one another, said air bags being disposed between each opposed projection carried pad of one collar member and its opposed projection carried pad of said other collar member, said air bags extending into said troughs, and each air bag having ends affixed to said opposed pads.

10. Acoupling according to claim 9, including circumferentially opposed abutment members on said first and second flanges, said abutment members being normally spaced apart and effective to limit relative rotation between said first and second collar members by engagement between the opposed abutment members.

11. A coupling according to claim 10, including a plurality of said abutment members, a first of said abutment members being positioned to be engaged by relative rotation in a first circumferential direction and a second of said abutment members being positioned to be engaged by relative rotation in a second direction opposite the first direction.

12. Ashaftcoupling substantially as hereinbefore described with reference to the accompanying drawings.