GB2086319A

GB2086319A - Improvements relating to lever biasing mechanisms

Info

Publication number: GB2086319A
Application number: GB8126985A
Authority: GB
Original assignee: SWINDON RACING ENGINES Ltd
Current assignee: SWINDON RACING ENGINES Ltd
Priority date: 1980-10-14
Filing date: 1981-09-07
Publication date: 1982-05-12
Also published as: GB2086319B

Abstract

A mechanism is provided for biasing a lever 2 which may be the support arm for the wheel of a motor bicycle. The lever 2 is connected directly to a support 1 through a pivot 3 and a pair of control links 8 and 9 are pivoted together at a common pivot 7 and respectively by pivots 10 and 11 to the support 1 and the lever 2. The common pivot 7 also carries the end of a shock absorber 4 whose other end is pivoted to the support 1. Movement of the lever 2 in the direction of the arrow 12 will be resisted by the shock absorber 4 which acts to force the control links 8 and 9 out of alignment. The arrangement is such that a linear rate of movement and load of the lever 2 will produce a non-linear rate of operation of the shock absorber 4 and vice versa. The end of the shock absorber 4 need not be connected directly to the common pivot 7 but could be pivotally connected to an intermediate or extended portion of one of the control links. <IMAGE>

Description

SPECIFICATION Improvements relating to lever biasing mechanisms This invention relates to lever biasing mechanisms which have general applications but it is more specifically concerned with a suspension arrangement wherein the lever is a support arm for the wheel of a vehicle, such as a motor bicycle.

It will be appreciated, however, that the mechanism could be used in other situations where it is desired to produce a controlled effort against movement of a lever in a particular direction.

According to this invention there is provided a lever biasing mechanism comprising a pivot point on the lever for mounting the lever on a support, two control links pivotally connected together at their one ends to provide a common pivot, the other end of one control link providing a pivot point for mounting the one control link on the support, and the other end of the other control link being pivotally connected to the lever at a position displaced from the lever pivot point, and a compressible member whose two ends provide pivotal connections, one of which is for mounting the one end of the compresssible member to the support and the other being pivotally connected to one or both of the control links so as to have its pivotal centre at or adjacent to the pivotal interconnection of the two control links.

As the lever is moved about its pivot point the control links (if they are initially set at an angle of less than 1 800 with respect to each other) can be moved into a more aligned condition and in the process will reduce the distance between their pivotal interconnection (the common pivot) and the pivotal mounting point of the one end of the compressible member, thus causing the compressible member to reduce in length. Thus movement of the lever will tend to be resisted.

It is preferred that the lever pivot point should be provided at one end of the lever, with the pivotal connection of the other control link being at a position between the ends of the lever, although for particular uses it may be convenient to reverse this arrangement.

Where the mechanism is to be used in supporting the wheel of a vehicle then the compressible member could take the form of a shock absorber or damper. The compressible member can be of any convenient form and thus may comprise a compression spring, a pneumatic or hydraulic ram, a body of rubber or other resilient material or a combination of such members.

In the preferred embodiment at least some of the pivots provide spherical bearings. Thus the ends of the control links themselves may provide such spherical bearings. The provision of spherical bearings allows the mechanism to be self-aligning.

The other end of the compressible member can, if required, extend beyond its pivotal connection to the control link(s). Thus there could be a return portion such as a sleeve surrounding part of the other end of the compressible member, leading back to that pivotal connection.

In one preferred arrangement the other end of the compressible member is pivotally connected to the common pivot between the two control links. Where the pivotal centre of the pivotal connection at the other end of the compressible member is not common with the pivotal interconnection of the two control links, it can be pivotally connected to one of the control links at a point between the two ends of the control link or on an extended portion of the control link which projects beyond the interconnection of the two control links. These modifications produce special characteristics for the operation of the lever biasing mechanism which are suitable for particular purposes.

The lever may carry a wheel or a wheel mounting at its other end. Furthermore a support may be incorporated in the mechanism to which the lever pivot point, the one end of the compressible member and the other end of the one control link are pivotally interconnected. Such a support may comprise part of the frame of a vehicle such as a motor bicycle.

The invention may be performed in various ways and preferred embodiments thereof will now be described with reference to the accompanying drawings, in which: Figure 1 A illustrates a shock absorber for the rear wheel of a motor bicycle, constructed in accordance with the invention; Figure 1 B illustrates the shock absorber in a compressed state; Figure 2 shows interconnections to one end of the shock absorber in more detail; Figure 3 illustrates control links to which the shock absorber is connected; Figure 4 illustrates a modification of the interconnection of the shock absorber with the control links; and Figures 5 and 6 illustrate shock absorbers of this invention in two further possible forms.

In Figure 1 A a support structure 1 forms part of the framework of a motor bicycle. An arm 2 is one of a pair, both of which are pivotally connected at 3 to the support structure 1 and each has at its other end a mounting for the rear wheel of the motor bicycle (not shown). A damper 4, incorporating a compression spring 5, is pivotally attached to the support structure 1 at one end by a pivot pin 6 and at the other end is pivotally connected by a common pivot pin 7 to the pivotal interconnection of two control links 8 and 9. The other end of the control link 8 is pivotally connected by a pivot pin 10 to part of the support structure 1. The other end of the control link 9 is pivotally connected by a pivot pin 11 to each of the levers 2.When the lever arm 2 is caused to move in the direction of the arrow 12, the control links 8 and 9 will move upwardly into a more aligned condition (as shown in Figure 1 B) with the result that the damper 4 is compressed so as to absorb the shock.

The interconnection of the control links 8 and 9 with the damper 4 can be seen in more detail in Figures 2 and 3 of the drawings. The pivot pin 10 for the other end of the control link 8 onto the support structure 1 is provided with a spherical bearing 1 3 which allows the axis of the control link 8, within limits, to move out of a position at 900 to the axis of the pivot pin 10. Similarly the control link 9 incorporates a spherical bearing 14 for the pivot pin 11 on the lever arm 2. The common pivot pin 7, interconnecting the ends of the control links 8 and 9, carries a spherical bearing 1 5 by means of which the free end of the damper 4 is interconnected concentrically with the interconnected ends of the control links.These spherical bearings, 13, 14 and 1 5 provide for selfcentering or aligning of the damper 4 and the control links 8 and 9 with respect to the fixed points on the support structure 1 and the pivot pin 11 connecting to the lever arms 2. Thus any small intolerances in the parts of the mechanism will not be critical.

Figure 4 illustrates a modification of the manner in which the free end of the damper 4 is interconnected with the common pivot pin 7 joining the ends of the control links 8 and 9. In this arrangement a portion of the end of the damper 4 extends beyond the interconnection point of the control links 8 and 9 but is supported by a bracket 1 6 connected at one end to the free end of the damper 4 and at the other end to the pivot pin 7, by a spherical bearing 15, as before. Thus the pivotal centre of the free end of the damper 4 is still basically concentric with the pivotal interconnection of the control links 8 and 9, as with the embodiment of Figure 1. The brackets 1 6 could be replaced by a sleeve member which totally surrounds the end portion of the damper, if desired.

In both of Figures 5 and 6 the parts of the mechanism which are substantially identical to those shown in Figures 1 to 4 are given the same reference numbers. In Figure 5, the modification shown is in the form of an extension of the control link 8 beyond the common pivot pin 7 to a position where a further pivot pin 1 7 connects to the free end of the damper 4. In the arrangement of Figure 6, a further pivot pin 1 7A is provided on a portion of the control link 8 lying between the pivot pins 7 and 10 and again links to the free end of the damper 4. By constructing the control link 8 to a suitable shape, the pivot pin 1 7 or 1 7A can be positioned at any angle and at any desired radius relative to the common pivot pin 7 interconnecting the control links 8 and 9.The pivot point for the pivot pin 1 7 or 1 7A could alternatively be carried by the control link 9, but ideally will be set below the connecting line between the axes of the pivot pins 7 and 11. It will readily be appreciated that the free end of the damper 4 could carry a bracket, such as that illustrated at 1 6 in Figure 4, which will lead back to the pivot pin 17.

Various modifications can be made to the design of the mechanisms as illustrated. Thus, whilst the control link 9 is shown in Figure 3 as being Y-shaped, there could be provided a pair of straight links 9 interconnected with the link 8 to either side at the pivot 7. The other ends of the pair of links 9 would then be associated respectively with the pair of levers 2, ideally through a common pivot pin 11.

The various designs of lever biasing mechanism described make it possible to obtain a non-linear rate of movement and load of the levers 2 in relation to a linear rate of operation of the damper 4. The arrangements shown in Figures 5 and 6 could be made to provide different characteristics to those where the end of the damper 4 is connected to the common pivot 7 and thus may make for increased versatility of operational characteristics.

Claims

1. A lever biasing mechanism comprising a pivot point on the lever for mounting the lever on a support, two control links pivotally connected together at their one ends to provide a common pivot, the other end of one control link providing a pivot point for mounting the one control link on the support, and the other end of the other control link being pivotally connected to the lever at a position displaced from the lever pivot point, and a compressible member whose two ends provide pivotal connections, one of which is for mounting the one end of the compressible member to the support and the other being pivotally connected to one or both of the control links so as to have its pivotal centre at or adjacent to the pivotal interconnection of the two control links.

2. A mechanism according to claim 1 , wherein the other end of the compressible member is pivotally connected to the common pivot between the two control links.

3. A mechanism according to claim 1, wherein the other end of the compressible member is pivotally connected to one of the control links at a point between the two ends of the control link or on an extended portion of the control link which projects beyond the interconnection of the two control links.

4. A mechanism according to any one of claims 1 to 3, wherein the lever pivot point is provided at one end of the lever, and the pivotal connection of the other control link is at a position between the ends of the lever.

5. A mechanism according to any one of claims 1 to 4, wherein the compressible member is a shock absorber or damper.

6. A mechanism according to any one of claims 1 to 5, wherein the compressible member is a compression spring, a pneumatic or hydraulic ram, a body of rubber or other resilient material or a combination of such members.

7. A mechanism according to any one of claims 1 to 6, wherein at least some of the pivots provide spherical bearings.

8. A mechanism according to claim 7, wherein the ends of the control links provide spherical bearings.

9. A mechanism according to any one of claims 1 to 8, wherein the other end of the compressible member extends beyond its pivotal connection to the control link(s).

10. A mechanism according to claim 9, wherein a return portion leads from the other end of the compressible member, back to the pivotal connection to the control link(s).

1 A mechanism according to claim 10, wherein the return portion is a sleeve surrounding part of the other end of the compressible member.

12. A mechanism according to any one of claims 1 to 11, wherein the lever carries a wheel or a wheel mounting at its other end.

13. A mechanism according to any one of claims 1 to 12, including a support to which the lever pivot point, the one end of the compressible member, and the other end of the one control link are pivotally interconnected.

14. A mechanism according to claim 12 and claim 13, wherein the support is part of the frame of a vehicle.

1 5. A mechanism according to claim 14, wherein the vehicle is a motor bicycle.

16. A lever biasing mechanism substantially as herein described with reference to the accompanying drawings.