GB2456340A

GB2456340A - An adjustable elastomeric torsion bush

Info

Publication number: GB2456340A
Application number: GB0800546A
Authority: GB
Inventors: Malcolm Tomlinson
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-01-14
Filing date: 2008-01-14
Publication date: 2009-07-15
Also published as: GB0800546D0

Abstract

An adjustable elastomeric torsion bush comprises an outer containment ring 1 with two sets of three symmetrically opposed recesses 2; two inner mouldings 3, each of which includes three recesses 4 which correspond to recesses 2 in the outer containment ring 1; three frustum plugs 5 which are located in the space defined between recesses 2, 4. Each inner moulding 3, is also aligned with and joined to the other by three sets of serrations 6 once the clamping bolt 7 has been tightened. An angular adjustment washer 8, is located between the torque arm 9 and the inner moulding 3 such that the arm 9 is set relative to the base containment ring 1 via the engagement of moulding indentations 3b with the appropriate washer pips 8b, and the engagement of the washer pips 8a with the torque arm indentations 9a when tightening the clamping bolt 7, after the introduction of the frustum plugs 5.

Description

Adjustable elastomeric torsion bush.

This invention relates to a non bonded, self assembly, repeatably adjustable torsion bush.

A conventional elastomeric bush has a metallic outer casing and central tube separated by an elastomer which is chemically bonded to both.

When used as a torsion spring, one element (say the outer casing) is rigidly fixed or anchored, and the other element (central tube) is rigidly attached to (typically) an arm which applies the torsional loading.

The moulding I bonding / curing process is costly as the metallic elements must have a bonding agent applied prior to loading into a mould into which the elastomer is introduced. Further, to anchor the bush and transmIt torque to the torsion arm requires specific design; and adjustment is often via matching a serrated tube end or by physically keying the tube ends, via e.g. by clamping star washers between the tube end and a lever I arm.

The serrated end method means that adjustment is coarsely incremental and may require further fine adjustment or precise anchoring of the outer casing.

The star washer method does not lend itself to repeated adjustment as the tube ends Will suffer damage and, subsequently, not accept even pristine star washers.

Although successfully used for heavy duty and continuously loaded applications this type of mounting does not lend itself to the application for which this subject invention relates. Specifically it is proposed for use as the suspension element in a deployable stabilizer for bicycles as proposed in patent GB 2406082 A. The subject proposal can be basically described as similar to a pair of taper roller bearings with the minor PCD's (pitch circle diameters) abutting each other, but with the potential to provide lOcation, transmit torque, and deflect under torque.

Specifically, it consists of an outer ring which is formed into 2 opposed sets of (say 3) equispaced concave, tapered recesses; and 2 inner mouldings each with recesses that oppose those in the outer ring. The inboard contacting faces of these mouldings key into each other when fully assembled such that both transmit any applied torque.

The springing is achieved by introducing frustrum shaped elastomer plugs into each of the 6 voids formed as the mouldings are axially introduced at opposite ends of the outer ring. Profiling the recesses and altering the rubber hardness will enable the torsion characteristics to be tailored.

The elastomer frustrum may have judicious rounding on the base to improve contact with the compressing flange on the moulding and thereby resist axial distortion.

The fine, and repeatable adjustment is achieved by interposing a hexagonal washer between the torque arm and an inner moulding outboard face. This washer has a number of pips on PCDs which may differ in diameter on each face. These pips locate in a matching sets of indentations on an inner moulding and on the torque arm.

The total number of pips on each face must differ by one from the opposite face to facilitate a differential increment. e.g. 9 and 10 such that: By loosening the clamping load the hexagonal washer can be rotated to its adjacent position on the moulding i.e. 119 of a turn or 4Odeg. and the torque arm can be rotated in the opposite direction i.e. 1/10 of a turn or 36 degrees. The relative angular movement is therefore 40-36=4 deg. The clamping load is then reapplied.

The invention will now be described solely by way of example with reference to the accompanying drawings in which: Fig. I shows a fully assembled bush.

Fig. 2 shows recess profiles and their effect on torsion characteristics.

Fig. 3 shows a schematic of a bicycle and highlights the application.

In fig.1, the outer containment ring 1, comprises two sets of three symmetrically opposed recesses 2. Each of the two inner mouldings 3, has three corresponding recesses 4, which are aligned with recesses 2, when the elastomer frustrum plugs 5, are introduced. Each inner moulding 3, is also aligned with, and effectively joined to the other by three sets of serrations 6, when the clamping bolt 7, is tightened.

An angular adjustment washer 8, is introduced between the torque arm 9, and the inner moulding 3, such that the ann 9, is set relative to the base containment ring 1, by engaging the moulding indentations 3b, with the appropriate washer pips 8b, and locating the washer pips'8a, into the torque arm indentations 9a, then tightening the clamping bolt 7, having first introduced the frustrum plugs 5.

To facilitate sub assembly prior to final installation, the number of pipsi8b, locating in the moulding indentations 3b, should be a multiple of, and symmetrical about, the number of recesses 4, whence orientation of the adjustment washer 8, relative to the base containment ring 1, can be predetermined by moulding a series of identifying marks 10, to the middle edge of (say) 3 non adjacent hexagonal faces e.g. 1,11,111.

Then, by presenting a selected one of these marks 10, close to, or ajudgeable distance away from a known or marked position on the containment ring 1, the washer.pips 8b will then settle into their closest moulding indentations 3b, whence the adjustment washer 8, will be correctly set relative to the containment ring 1. Similarly, the torque arm 9, can then be approximated to it's desired position and presented to the washer 8, whence the torque arm indentations 9a, will also settle onto the washer pips 8a, in the desired positipn, before tightening the clamping bolt 7.

This is practicable since the operator need only judge positions to +1-40 deg. and +/-36 deg. respectively.

Claims

Claims. 3 I. An elastomeric torsion bush wherein the torsion resistance is achieved by compressing a number of frustrum shaped elastomeric elements.

2. A bush as in claim I, wherein the elastomerjc elements are inclined similar to the rollers in a pair of opposed taper roller bearings but with the elements constrained in chambers such that rotation of the inner with respect to the outer is opposed through compressing the elastomer.

3. A bush as in claim 2, wherein all the elements can be manually assembled.

4. A bush as in claim 2, wherein the outer ring and inner mouldings have (say 6) recesses which, when assembled, oppose each other and compress and constrain elastomeric frustra.

5. A bush as in claim 4, wherein the inner mouldings key into each other when abutted thereby providing alignment and sharing torsion loads.

6. A bush as in claim 5, wherein torque arm positions can be positively and repeatedly adjusted by means of a washer with a multiplicity of equispaced pips on either side, the numbers on each side differing by one such that engagement with corresponding indentations in their mating parts can produce a differential increment.

7. A bush as in claim 2, wherein the profile of the chambers effects the torsion characteristics.

8. A bush as in 7, wherein the form of the chambers can limit maximum torque loadings and allow resetting after tripping out.

AMENDED CLAIMS HAVE BEEN FILED AS FOLLOWS:-Claims.

I.An elastomeric torsion bush wherein the torsion resistance is achieved by radial compression of frustrum shaped elastomeric elements.
2. A bush as in claim 1, wherein the elastomeric elements are inclined similar to the rollers in a pair of opposed taper roller bearings but with the elements constrained in inner and outer chambers such that rotation of the inner with respect to the outer is opposed through compressing the elastomeric elements.
3. A bush as in claim 2, wherein the outer ring and inner mouldings have recesses which, when assembled, oppose each other and compress and constrain elastomeric frustra.
4. A bush as in claim 3, wherein the inner mouldings key into each other when abutted thereby providing alignment and sharing torsion loads.
5. A bush assembly as in claim 4, wherein the inner mouldings key into each other when abutted to produce a minor angular misalignment between inner and outer moulding recesses to produce a torsional preload when fully assembled.
6. A bush as in claims 2 to5 wherein torque arm positions can be positively and repeatedly adjusted by means of a washer with a multiplicity of equispaced pips on either side, the numbers on each side differing by one such that engagement with corresponding indentations in their mating parts can produce a differential increment.
7. A bush as in claims 2 to 5, wherein the profile of the chambers affects the torsion characteristics.
8. A bush as in claims 2 to 5, wherein the form of the chambers can limit maximum torque loading and allow resetting after tripping out.
9. A bush assembly as in claims 2 to 5, wherein the inner mouldings flange diameters may be increased and a peripheral inboard rim added parallel to the mount axis and proximat to a modified perimeter of the outer ring thereby providing a dust seal. I...
10. A bush system as in claims 1-9 wherein a keyed spacer between the inner mouldings will increase the distance between opposing frustra sets to provide a robust pivot axis . :
II. A bush assembly as in claims 1-7 wherein by increasing the cone angle of the frustra axes a constrained yet universal isolation mounting results. S..

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12. A bush assembly as in claim 11 wherein the frustra size and/or hardness may differ in opposing sets thereby producing different axial characteristics in opposite directions.

IS S S. * SS