GB2564831A - Suspension pivot - Google Patents

Abstract

A composite suspension pivot where plain bushes or bearings 4 fitted into moving spool 3 and bearing on pivot journal 1 are supplemented by elastomeric elements (for example O-rings) 5 that provide a damping force to the pivot by means of torsional shear or friction. The elastomeric elements also eliminate bearing play and seal the pivot by closing the gap between fixed pivot ears 2 and moving spool 3, this prevents the ingress of water or dirt. The elastomeric elements may be bonded to the pivot. The elastomeric elements may provide a hermetic seal.

Description

Suspension Pivot

This invention relates to a pivot between structures, such as on a suspension mechanism on a bicycle. A suspension mechanism typically requires a pivot allowing movement in one plane, ensuring the horizontal alignment of the bicycle whilst allowing vertical compliance. Often, the pivot is located behind the bottom bracket of the bicycle, as shown in Figure 1.

Typically, one half of suspension pivot comprises a pivot journal clamped between two plates. The other half comprises an assembly with a tubular bore, containing bearing bushes (usually plastic or metal). These bushes fit over the pivot journal and, when the assembly is clamped (typically by a bolt through the end plates and journal) one half of the pivot assembly is free to rotate in relation to the other half, with one degree of freedom. This is shown in Figure 2.

There are several drawbacks to this arrangement, including wear or damage to the inner surfaces of the end plates caused by the pivoting assembly, the requirement for a small amount of 'end float' to ensure that the pivoting assembly is not clamped between the plates, and vulnerability to the ingress of dirt and other contaminents.

The present invention provides a simple solution to these three problems, and also provides and advantageous damping force to the pivot.

According to the invention, with reference to Fig. 3 (section view) and Fig. 4 (exploded view), there is provided a pivot journal (1) of length between 40-100mm and diameter in the range of 10 to 50mm clamped between two end plates (2) (between 2 and 10mm thick) in the conventional manner. Spool (3) is able to pivot around journal (1), with tubular bearings (metallic or plastic) (4) providing a smooth bearing surface. '0' - rings (5), typically of a rubber compound material and of diameter between 10mm and 50mm and round section between 2 and 10mm, are fitted into the recess formed by the pivot journal, bearings and spool. When the assembly is clamped together by means of a central bolt or otherwise, the 'o'-rings are compressed by a set amount (typically 1030%) and deform against the end plates and into the recess.

The 'o'-rings therefore become both an axial spring (eliminating end float) and a contact seal to prevent contamination of the bearing surfaces and avoiding any hard contact between pivoting surfaces.

Damping of the pivot assembly is provided in two separate ways. For large articulation angles (rarely found on bicycles), the 'o'-rings form a simple friction damper as the 'o'-ring rubs against the outer plate during pivot rotation. For small articulation angles as often found on bicycle suspension (2-5 degrees) the damping is provided by rotational shear of the 'o'-ring itself. This is advantageous as there is no friction between the 'o'-ring and the end plates or pivot spool, so there is no wear on these parts and there is no 'breakaway' torque required to articulate the pivot other than that caused by the tubular bearings.

In addition, with careful design in regarding to sizing of the 'o'-rings and the recess into which they fit, the 'o'-rings are able to act as a return spring acting of the pivot. In such applications, using an 'o'-ring of modified section (typically square section) may be desirable, as may bonding the 'o'-ring or other similar element to one or both of the pivoting assemblies. If bonded to both pivoting assemblies, the articulation angles must be restricted.

Explanatory note to Fig. 2

The Pivot Journal is clamped between pivot ears using either through bolt or two bolts - one from each side.

Pivot spool and bushes rotate around pivot journal.

For bearing to work effectively, some axial play ('end float') is required between pivot bush flanges and pivot ears.

Any lateral force results in pivot bush flanges bearing on pivot ears.

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Claims (7)

Claims

1 A composite suspension pivot where plain bushes or bearings are supplemented by compressible elastomeric elements at each end of the pivot to act as axial springs to eliminate end-float and to seal the bearing mechanism against ingress of water, dirt and other foreign matter.

2 A suspension pivot according to claim 1, where the elastomeric elements provide a damping force to the suspension movement by virtue of torsional shear over small angular movements.

3 A suspension pivot according to claim 1, where the elastomeric elements provide a damping force by virtue of friction between the elastomeric elements and the pivoting surfaces.

4 A suspension pivot according to preceding claims 1, 2 and 3, where the elastomeric elements are bonded to either the 'fixed' or the 'moving' part of the pivot, to reduce the number of loose parts on disassembly.

5 A suspension pivot according to preceding claim 2, where the elastomeric elements are bonded to both the 'fixed' and 'moving' parts of the pivot to provide an hermetic seal.

6 A suspension pivot according to preceding claims 1, 2 and 3, where the elastomeric elements are bonded to either the 'fixed' or the 'moving' part of the pivot, and arranged so as to provide a spring force (self-centring) to the pivot by virtue of torsional elasticity in the elastomeric elements.

7 A suspension pivot according to the preceding claim 2, where the elastomeric elements are bonded to both the 'fixed' and 'moving' parts of the pivot and arranged so as to provide a spring force (self-centring) to the pivot by virtue of torsional elasticity in the elastomeric elements.