GB2158195A

GB2158195A - Torque transmission device

Info

Publication number: GB2158195A
Application number: GB08510823A
Authority: GB
Inventors: Howard Stuart Atkin
Original assignee: Dunlop Ltd
Current assignee: Dunlop Ltd
Priority date: 1984-05-01
Filing date: 1985-04-29
Publication date: 1985-11-06
Also published as: GB2158195B; GB8510823D0

Abstract

A torque transmission device suitable for use as a sprocket device to transmit torque between a drive shaft and a flexible endless track comprises a hub member to which drive torque may be applied, two part-circular support members 12 securable together to form an annular support member which extends around the hub member, and a plurality of resilient bushes 13 circumferentially spaced apart to interconnect the hub and annular support members. Preferably the part-circular support members are secured together at least in part by an annular member such as an annular sprocket wheel 14. <IMAGE>

Description

SPECIFICATION Torque transmission device This invention relates to a torque transmission device and in particular, though not exclusively, to a torque transmission device for use as a sprocket device suitable for transmitting torque between a drive shaft and a flexible endless track of a track type vehicle.

In a track type vehicle it is common for drive force to be transmitted to the endless track by means of a sprocket device to which is secured a sprocket wheel provided with a series of circumferentially spaced teeth arranged to engage and transmit drive to the endless track. In this arrangement sudden loads experienced by the track when traversing uneven ground result in the application of sudden loads to the sprocket wheel, and these loads have an adverse effect on the ride quality of the vehicle as experienced by its occupants. Furthermore the shock loads generate unwanted noise additional to the usual track noise caused by successive track plates continually coming into contact with the ground and track plate bearing surfaces of the sprocket device.

It is an object of the present invention to provide an improved torque transmission device wherein in use of the device the transmission of shock loads and generation of noise is reduced.

In accordance with the present invention a torque transmission device comprises: a hub member for the application of drive torque thereto, at least two part circular support members securable together to form an annular support member which extends around at least a part of the hub member in spaced relationship therewith, and a plurality of resilient bearing means provided at circumferentially spaced positions between said hub member and annular support member resiliently to interconnect said members and maintain said members in a normally spaced relationship.

The invention is of particular use for sprocket devices of a kind having a bearing surface for engagement by the track plates of a track type vehicle to withstand loads acting on the sprocket device in a generally radial direction relative to the axis of rotation of the sprocket device, and a sprocket wheel or like torque transmission member associated with the sprocket device for engagement with the track to transmit force thereto only or primarily in a circumferential direction relative to the axis of rotation of the sprocket device.

The present invention further provides that the annular support member be provided with location means for a torque transmission member, for example a sprocket wheel, and a track plate load bearing surface or location means therefor.

It is preferred that at least one of the hub and annular support members be of a channel section as viewed in a plane containing the normal axis of rotation of the device and that the other of said members be provided with housing means which in the assembled device extends into said channel and supports the resilient bearing means.

Preferably the plurality of resilient bearing means comprises a plurality of cylindrical resilient bushes each of which fits into a tubular housing means of one member and each of which is bonded to a rigid inner tube through which extends a location pin or rod supported by the channel section shape portion of the other member. Preferably the resilient bearing means are located by means of hollow pins to assist cooling of the resilient material. The bushes may be formed of a resilient elastomeric material such as rubber.

The resilient bearing means may comprise a plurality of cylindrical resilient bushes each of which is formed with outwardly extending shoulder portions at the axially outer ends thereof so as to assist in withstanding, during use, side thrust forces, ie forces tending to move the bush in the direction transverse to the normal direction of vehicle movement when the bush is mounted with the major axis thereof perpendicular to said normal direction of vehicle movement.

In a preferred construction each resilient bush is of waisted profile, by which is meant that the outer dimension of the bush decreases progressively from each end thereof to a position midway between said ends.

Preferably the torque transmission device is provided with a circumferentially continuous annular sprocket wheel and/or track plate bearing member secured to the part circular support members so as to assist in maintaining said support members in the form of an annular support member.

The part circular support members may comprise reinforcing webs, in which case preferably reinforcing webs are provided in the region of each end of the part circular support members, said webs being adapted for connection of successive part circular members for example by being provided with holes to receive location bolts.

The torque transmission device may comprise a track plate bearing surface in the form of an annular band of resilient elastomeric material which may be bonded to an annular metal support adapted for attachment to the annular support member.

One embodiment of the invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings wherein: Figure 1 is a side view of part of a sprocket device in accordance with the present invention; Figure 2 is a section on the line Z-Z of Fig.

1; Figure 3 is a section on the line Y-Y of Fig.

1; Figure 4 is a view in the opposite direction to that of Fig. 1 of a part of the sprocket device lying between the lines Y-Y and Z-Z of Fig. 1; Figure 5 is a section on the line X-X of Fig.

4, and Figure 6 is a view similar to that of Fig. 2 showing an alternative construction.

A sprocket device 10 in accordance with the present invention and for transmitting drive to the track plates of a track type vehicle comprises a hub member 11, two semi-circular support members 12, a plurality of resilient bush assemblies 1 3 between said hub and support members, an annular sprocket wheel 14 and an annular tyre band 1 5.

The hub member 11 comprises an annular flange portion 1 6 apertured for the location of bolts 1 7 by means of which the hub member is secured to drive means (not shown). The hub member comprises additionally a substantially cylindrical shaped rim portion 1 8 which extends from a radially outer edge of the flange portion 1 6 and has formed integrally therewith fourteen circumferentially uniformly spaced bush location means 19, said location means being cast integral with the cylindrical rim portion 18, and typically formed of aluminium.

Located in each bush location means 1 9 is a cylindrical shaped rubber bush 20 which is a compression fit within the bore of location means 1 9. The radially inner surface of the cylindrical bush 20 is bonded to an inner rigid sleeve 21 (see Fig. 2), and the major axis of said sleeve 21 and the bore of the location means 1 9 are parallel with the normal axis of rotation of the hub member 11.

The two semi-circular support members 1 2 are of a channel shape in section (as viewed in Figs. 2 and 3) and comprise each a central portion 22 and a pair of side portions 23a, 23b which extend radially inwards from said central portion 22. The dimensions of the semi-circular support members are such that when assembled together to form a circumferentially continuous annular support member around the hub member the bush location means 1 9 and their respective bushes 20 lies between said side members 23a, 23b.

The side members are each formed with fourteen circular openings 24a, 24b which in the assembled sprocket device are aligned with the bush inner sleeves 21, and a pin type fastener 25 is provided in each respective pair of openings 24a, 24b to extend through the bush sleeve 21 and thereby connect the support members 12 to the respective bushes 20. Each pin 25 preferably is a type formed with a small protrusion 26 at one end 27, the pin being force fitted into position, end 27 first, and automatically resisting withdrawal in a reverse direction by virtue of the protrusion 26. The other end, 28, of the pin is outwardly flared to limit movement of the pin in the direction of insertion.

When assembled around the hub member 11 the two semi-circular support members 1 2 define a circumferentially continuous annular radially outwardly extending face 29 to which an annular sprocket wheel 14 is secured by means of bolts 30 (see Fig. 3).

The semi-circular support members 1 2 each comprisesadditionally a semi-cylindrical shaped flange portion 31 which extends in line with the central portion 22 of the support member, in a direction away from the face 29, and said flange portion provides support for the tyre band 1 5.

The tyre band comprises a band of relatively hard, eg shore A hardness 80, elastomeric material 32 bonded to a metal plate 34 one edge 35 of which is formed with apertures for receiving screw fastenings 36 to hold the band relative to the support members. The other edge portion 37 is curved in a manner which conforms with the curvature of the outer edge of flange portion 31.

Accordingly, in the assembled condition the two semi-circular support members 1 2 are held in a circumferentially continuous configuration firstly by means of the circumferentially continuous sprocket wheel 14 bolted to the support members, and by the circumferentially continuous tyre band 1 5 which engages the support members both by means of retention screws 36 and the turned over edge portion 37.

To ensure adequate strength to resist shock loads the flange portion 37 of the support members is supported relative to the side portion 23b by means of reinforcing webs 38.

Similarly the cylindrical portion 1 8 of the hub member is supported relative to the flange portion 1 6 by means of reinforcing webs 39.

To further assist in ensuring that the two semi-circular support members 1 2 do not separate, reinforcing webs 38 are provided at each end of each semi-circular member 1 2 so that on assembly the respective end webs of the support members come into contact one with another. Said webs are apertured for location of bolts 40 provided to prevent separation of the webs 38.

In the resulting assembly of the sprocket device the resilient bushes serve to attenuate the transmission to the hub member of those loads experienced by the annular support member 1 2 and which arise in use in a track type vehicle primarily by virtue of the track plates engaging the sprocket wheel 14 and the tyre band 15.

By virtue of the circumferentially continuous form of the sprocket wheel 14 and tyre band 15, together with the bolt connection of webs 38, it is ensured that the two semi-circular support members 1 2 are maintained in an annular form. Accordingly, notwithstanding any failure that might occur in respect of the resilient bushes 20 the channel section of the support member is maintained in position relative to the bush location means 1 9 of the hub member 11 to provide a fail-safe form of construction.

In the above described embodiment of the invention the support members 1 2 are connected to the respective bushes 20 by means of pin type fasteners 25 as shown in Fig. 2.

In an alternative construction, shown in Fig.

6, bolts 40 and lock nuts 41 are employed to interconnect the support members 1 2 and bushes 20.

Claims

1. A sprocket device comprising: a hub member for the application of drive torque thereto, at least two part-circular support members securable together to form an annular support member which extends around at least a part of the hub member in spaced relationship therewith, a plurality of resilient bearing means provided at circumferentially spaced positions between said hub member and annular support member resiliently to interconnect said members and maintain said members in a normally spaced relationship, and an annular sprocket wheel secured to said two part circular-support members to assist in maintaining said support members in a circumferentially continuous form and to transmit drive forces from the annular support member to vehicle track plates.

2. A torque transmission device comprising: a hub member for the application of drive torque thereto, at least two part-circular support members securable together to form an annular support member which extends around at least a part of the hub member in spaced relationship therewith, and a plurality of resilient bearing means provided at circumferentially spaced positions between said hub member and annular support member resiliently to interconnect said members and maintain said members in a normally spaced relationship.

3. A torque transmission device according to claim 2 wherein at least one of the hub and annular support members is of a channel section as viewed in a plane containing the normal axis of rotation of the device.

4. A torque transmission device according to claim 3 and wherein the other of said members is provided with housing means which in the assembled device extends into said channel and supports the resilient bearing means.

5. A torque transmission device according to any one of claims 2 to 4 wherein the resilient bearing means comprises a plurality of cylindrical resilient bushes each of which is located in a tubular housing means of one member and is connected to a channel section shaped portion of the other member.

6. A torque transmission device according to claim 5 wherein said resilient bearing means are located relative to said other member by means of a hollow pin.

7. A torque transmission device according to any one of claims 2 to 6 wherein said resilient bearing means comprises a plurality of resilient bushes each formed with outer shoulder portions at the axial ends thereof.

8. A torque transmission device according to any one of claims 2 to 7 wherein the resilient bearing means comprises a plurality of cylindrical resilient bushes of a waisted profile.

9. A torque transmission device according to any one of the claims 2 to 8 and comprising a circumferentially continuous torque transmission member and/or track plate bearing member secured to the part-circular support members to assist in maintaining said members in annular form.

10. A torque transmission device according to any one of the claims 2 to 9 and having secured to the support members an annular support to which is bonded a band of elastomeric material.

11. A torque transmission device according to Claim 2 and constructed and arranged substantially as hereinbefore described with reference to the accompanying drawings.

1 2. A sprocket device comprising a torque transmission device according to any one of Claims 2 to 11 and adapted to transmit torque between a drive shaft and a flexible endless track.

1 3. A sprocket device according to Claim 1 and constructed and arranged substantially as hereinbefore described with reference to the accompanying drawings.