GB2235034A

GB2235034A - Flexible coupling

Info

Publication number: GB2235034A
Application number: GB8916045A
Authority: GB
Inventors: Graham Edward Harpin
Original assignee: Holset Engineering Co Ltd
Current assignee: Cummins Turbo Technologies Ltd
Priority date: 1989-07-13
Filing date: 1989-07-13
Publication date: 1991-02-20
Also published as: GB8916045D0

Abstract

A flexible coupling comprises a coupling element 6a, 6b of elastomeric material interconnecting two coupling members 1, 3 and fixed to at least one of them by means of a fastening system including a plurality of rigid bushes 20, 21, 22, 23 embedded in the coupling element and held immovably with respect to the coupling member by clamping plates 9, 10, 14, 15 which are urged together with fasteners 24, 25 extending through said bushes. <IMAGE>

Description

A FLEXIBLE COUPLING This invention relates to a flexible coupling.

According to the present invention there is provided a flexible coupling comprising a coupling element of elastomeric material interconnecting two coupling members and fixed to at least one of them by means of a fastening system including a plurality of rigid bushes embedded in the coupling element and held immovably with respect to the coupling member by clamping plates which are urged together by fasteners extending through said bushes.

Preferably, the coupling element is fixed to both coupling members by respective fastening systems which are radially spaced with the coupling element extending radially and circumferentially therebetween. In operation of this flexible coupling the elastomeric material of the coupling element will therefore be subject to shear stresses but by virtue of the fastening system as defined such stresses are not imparted to the fasteners with obvious advantages in terms of the life of the coupling.

The invention will now be further described by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a longitudinal section of one embodiment of flexible coupling in accordance with the invention, on the line I-I of Fig. 2; Fig. 2 is an end view mainly from the right of Fig. 1 but with a partial view in the direction of arrow X; Fig. 3 is an end view of one segment of the elastomeric coupling element, and Fig. 4 is a section of the coupling element segment on the line IV-IV of Fig. 3.

Referring now to the drawings, the flexible coupling of Figs. 1 and 2 comprises a cylindrical inner coupling member 1 having an axial bore 2 for receiving a shaft (not shown).

Radially spaced from the inner member 1 is a cylindrical outer coupling member 3 with a radial connecting flange 4 having apertures as indicated at 5 for receiving fasteners for fastening the coupling member 3 to a flywheel or flanged shaft (not shown). The inner and outer coupling members 1, 3 are resiliently interconnected by an elastomeric coupling element which is provided in this case in two mirror-symmetrical axially spaced halves 6a, 6b each of which is divided equiangularly into four closely adjacent circumferential segments indicated at 6b1/2/3 and 4 in Fig. 2. The coupling element 6a, 6b is made of unreinforced elastomeric material which may be natural or synthetic rubber.

The radially inner and outer edges of the coupling element are fixed to the coupling members 1, 3 by respective fastening systems 7, 8. The fastening system 7 comprises axially spaced annular clamping plates 9, 10 slidably mounted on the outer cylindrical surface of the coupling member 1 at opposite sides of an integral flange 11 having opposite side faces ila and 11b which provide clamping surfaces cooperating with the plates 9, 10 respectively. The clamping plate 9 thus defines with the opposed clamping surface lia of the integral flange 11 a recess 12 which is filled by the radially inner edge of the coupling element half 6a, the corresponding edge of the coupling element half 6b filling the similarly defined adjacent recess 13 between surface llb and plate 10.

In like manner the fastening system 8 of the outer coupling member 3 comprises clamping plates 14, 15 slidable on the inner cylindrical surface 3a of the coupling member 3 which has an integral flange 16 projecting inwardly towards the opposing flange 11 of the fastening system 7. The clamping plates 14, 15 and the wall 16 together define recesses 17, 18 facing the corresponding recesses 12, 13. The integral flanges 11, 16 are dimensioned so as to provide a substantial air space between the coupling element halves 6a, 6b and the outer wall 16 is provided with radial air passages 19 for ventilating this air space through centrifugal force.

In addition, passages 30 in member 3 provide a cooling flow of air past grooves 32 in clamping plate 14 for ventilating the space to the aft of coupling half 6a, as viewed in Fig.

1.

Each circumferential segment of coupling element halves 6a, 6b is provided with a ring of bushes at its inner and outer edges as shown in more detail in Figs. 3 and 4 which illustrate one segment 6bl in greater detail. It should be noted that in the illustrated embodiment one 900 segment is duplicated 8 times to make up the elastomeric part of the coupling, thus enabling a saving in manufacturing cost due to small moulds and in servicing because only the appropriate segment need be replaced. The inner bushes 20, 21 are received in the recesses 12, 13 respectively whereas the outer bushes 22, 23 are received in the recesses 17, 18 respectively.The bushes 20, 21 and 22, 23 form part of the respective fastening systems 7, 8 and are aligned with apertures in the plates 9, 10 and wall 11 ( n the case of the fastening system 7) and in the clamping plates 14, 15 and the wall 16 (in the case of the fastening system 8). The bushes 20, 21 are also aligned with each other as are the bushes 22, 23. Sets of fasteners 24, 25 hold the bushes in position in the respective recesses. The fasteners 24, 25 are bolts in screw-threaded engagement with the walls 9 and 14 so that on tightening they clamp the bushes in their recesses by means of the clamping plates.

As seen in Fig. 4, which shows the segment 6bl of the coupling element in the relaxed condition, the inner and outer bushes 20-23 are embedded in the respective edges of the coupling element in such a way that each end of a bush is slightly recessed into the elastomeric material. The respective edge of the relaxed coupling element 6a, 6b is thus axially wider than the respective recess in the fully tightened condition of the respective fasteners 24, 25 but has a small clearance with respect to the adjacent cylindrical surface so as to facilitate assembly. In the fully tightened condition, as seen in Fig. 1, the bushes 20-23 are tightly clamped in their recesses and rendered immovable by frictional engagement with the respective clamping walls or surfaces which laterally define the respective recess.Elastomeric material is therefore forced inwardly of the respective recesses 12 and 13 to take up the clearance mentioned above and outwardly towards the inner facing recesses 17 and 18.

In consequence, the coupling elements 6a, 6b are subjected to radial compressive stresses which is an advantage in giving the elastomeric material greater endurance under oscillating load conditions. This radial loading also ensures that the bond between the bushes and the elastomeric material, which may be a vulcanised bond, is under a compressive load during operation thus reinforcing the bond.

The clamping plate 9 has an outward radial projection 26 which is circumferentially aligned with but spaced from an inward radial projection 27 from the clamping plate 14, the two projections 26, 27 serving to limit the relative angular movement of the two coupling members 1, 3 to an arc of say 450 for a fail safe limit.

It will be noted that the radially inner edge of the coupling element is substantially wider in the axial direction than the radially outer edge thereof with a shaped transition between these regions. This configuration of the coupling element i.e. of its two halves 6a, 6b is intended to ensure an equal distribution of the -tangentially directed shear forces in the coupling element over the radial extent thereof during operation.

It will be appreciated that numerous modifications may be made without departing from the scope of the invention.

Thus, for example, the coupling element need not be divided into two halves 6a, 6b nor need it be segmental as described and illustrated. Furthermore, if the coupling element is segmental the number of segments may be reduced or increased to a number less than or greater than 4.

Claims

1. A flexible coupling comprising a coupling element of elastomeric material interconnecting two coupling members and fixed to at least one of them by means of a fastening system including a plurality of rigid bushes embedded in the coupling element and held immovably with respect to the coupling member by clamping plates which are urged together with fasteners extending through said bushes.

2. A coupling as claimed in claim 1, wherein the coupling element is fixed to both coupling members by respective fastening systems which are radially spaced with the coupling element extending radially and circumferentially therebetween.

3. A coupling as claimed in claim 2, wherein each fastening system comprises a recess defined laterally by the clamping plates and filled by the respective radial edge of the coupling element, said edge in its relaxed condition projecting laterally beyond the bushes embedded therein such that the action of the clamping plates forces the elastomeric material out of the respective recess thereby radially stressing the coupling element.

4. A coupling as claimed in claim 2 or 3, wherein the coupling element is circumferentially divided into a plurality of adjacent segments.

5. A coupling as claimed in any one of claims 2 to 4, wherein the coupling element is radially divided into two halves and each fastening system has two adjacent recesses for adjacent edges of the coupling element halves, said recesses being separated in each fastening system by a fixed wall serving as a clamping plate for each recess and penetrated by the fasteners.

6. A coupling as claimed in claim 5, wherein the fixed wall of the radially outer fastening system is provided with one or more air passages for ventilating a gap between the two halves of the coupling element.

7. A coupling as claimed in any one of the preceding claims, wherein ventilating holes are provided in an outer one of the coupling members.

8. A coupling as claimed in any one of claims 2 to 7, wherein the two coupling members have angularly spaced opposed projections for limiting the angular movement of the coupling members relative to each other.

9. A flexible coupling substantially as herein described with reference to the accompanying drawings.