AU614141B2

AU614141B2 - Brake shaft bushes

Info

Publication number: AU614141B2
Application number: AU35257/89A
Authority: AU
Inventors: Edgar Malcolm Stubbersfield
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-07-01
Filing date: 1988-07-01
Publication date: 1991-08-22
Anticipated expiration: 2009-05-29
Also published as: AU3525789A

Description

614141 Ihis document contains .na Samendrmeni s ailow J und I i Szction 83 by the Supervising Examiner un Sand is correct icr printing j COMMONWEALTH OF AUSTRALIA Patents Act 1952 0o 0 0 0 00 00 0 a 0 a0 0 0 0 0 0 t 00 ea ao 0 0 0 0 00 0 0 C 0 00 0 oo 0 0 00 Name of Applicants Address of Applicants Actual Inventor Address for Service EDGAR MALCOLM STUBBERSFIELD BERYL GRACE STUBBERSFIELD Old College Road, GATTON. QLD. 4343

AUSTRALIA.

EDGAR MALCOLM STUBBERSFIELD GRANT ADAMS COMPANY, Patent Trade Mark Attorneys, 333 Adelaide Street, BRISBANE. QUEENSLAND. 4000

AUSTRALIA.

COMPLETE SPECIFICATION FOR THE INVENTION ENTITLED: "BRAKE SHAFT BUSHES" The following statement is a full description of the invention including the best method of performing it known to us.

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2 Title: "BRAKE SHAFT BUSHES" BACKGROUND OF THE INVENTION Field of the Invention THIS INVENTION relates to brake shaft bushes.

Prior Art Semi-trailer and large truck brakes are operated by an cam which is activated by an air cylinder, each brake cam shaft being supported at its ends by nylon bushes. While the bush at the activating end of the cam shaft can be easily replaced, the bush behind the cam itself can only be replaced by removing the wheels from the axle. On a triaxle trailer, where there are six sets of wheels to be 00 0o 0 oo 15 Where the trailers operate off highway, the 0o life of the nylon shaft bushes is drastically reduced as they cannot be lubricated otherwise dust combines with %a 0 the grease to form an effecting grinding paste. The bushes may wear out as frequently as every three months and must be replaced. As the bushes wear, the cams drop relative to the brake backing plate, causing the bottom 0 0 o0, brake shoe to rub and wear. Therefore, the brake 00linings have to be replaced more frequently than should 00 be necessary, and wear also occurs on the cam shafts and 0.0 0 the bush housing.

SUMMARY OF THE INVENTION 0000 It is an object of the present invention to 00 0 oo 0o provide a bush assembly for the brake cam shafts which 0 o 0 o0 have reduced wear.

It is a preferred object to provide a seal assembly which enables the bushes to be greased for longer life.

It is a further preferred object to provide a bush assembly which can be easily replaced when required and which can be fitted to a standard bush housing

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during ordinary servicing or as original equipment.

Other preferred objects of the present invention will become apparent from the following description.

In one aspect, the present invention resides in a bush and seal assembly for rotatably supporting a brake cam shaft in a bush housing on a vehicle axle assembly, the bush and seal assembly including: a pair of outer bush bodies to be inserted 10 into the housing from each side; 0 0 a bush member supported in the outer bush ooo bodies adapted to bear against and support the brake cam 0 shaft; o 0° a respective dust seal housing attached to 0 0o°0 15 each outer bush body and of greater diameter than the 0 0 outer bush body and connected to the outer bush body by an annular web engageable with a respective end face of the bush housing; o0oo0 a dust seal in each seal housing having at least one lip engageable with the brake cam shaft so arranged that when grease is pumped into the bush Soo housing to lubricate the bush member, excess grease can escape under the lip or lips of the seal but dust is prevented from entering the bush housing; and wherein o 25 the bush and seal assembly is retained in the bush housing by a circlip engaged in a circumferential groove in the brake cam shaft.

Preferably, the bush and seal assembly is provided for the cam end of each brake cam shaft.

However, the bush and seal assembly can also be provided for the activating end of each brake cam shaft.

Preferably, the bush member is formed of reinforced plastics material, eg. glass reinforced nylon.

The bush body and bush member may be formed as an integral component.

pp\i i. 4 In a second aspect, the present invention resides in a brake cam shaft bush, for rotatably supporting a brake cam shaft, including: an outer bush body to be inserted in a bush housing on a vehicle axle assembly; a bush member supported in the ou'cer bush body to bear against and support the brake cam shaft; a seal housing at one end of the outer bush body and of greater diameter than the outer bush body; 10 seal means in the seal housing, the seal o means having at least one lip engageable with the brake o 00 000 0 cam shaft to enable excess grease in the bush housing to 0 'o escape under the lip or lips but to prevent dust o0 entering the bush housing; and 004 0 15 an annular web interconnecting the seal 0 o housing and the outer bush body engageable with an end face of the bush housing to locate the outer bush body in the bush housing; wherein: 0000.o. the bush is retained in the bush housing by 0#0: 20 a circlip engaged in a circumferential groove in the brake cam shaft.

BRIEF DESCRIPTION OF THE DRAWINGS To enable the invention to be fully understood, a number of preferred embodiments will now o o 25 be described with reference to the accompanying 0 0 0 drawings, in which: 0 0 100 FIGS 1 to 3 show sectional side views of alternative assemblies supporting a brake cam shaft in a conventional bush housing fitted to a vehicle axle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG 1, the brake cam shaft 10 is of conventional type with a cylindrical shaft body 11 having an cam 12 which engages the brake shoe rollers (not shown). The bush housing 13 is provided on r i the standard anchor bracket (not shown) mounted at one end of the axle assembly.

A small hole 14 is provided in the housing 13 to receive a grease nipple (not shown) which engages grease to be pumped into the interior of the housing when fitted with the bush assembly 15 of the present invention.

Each bush has an outer body 16 inserted into the housing 13 with an outer enlarged dust seal housing 0Q 10 17 which forms an abutment to engage the adjacent end 00 000 face of the bush housing 13. The inner end of each 0 oO body 16 is provided with an inturned flange 18, 0 0o o o0 supported by an annular web 19, to engage an annular 0 00recess 20 at the inner end of a glass-reinforced nylon bush member 21. A similar inturned flange 21a is provided on an annular web 22 to engage the annular recess 20 at the outer end of the bush member 21. As ooO0 shown, the annular web 22 is fixed to the annular web 23 interconnecting the outer bush body 16 and the dust seal 0 S 20 housing 17, that annular web 23 abutting end face of the 0 O0 bush housing 13.

0000 001 A dust seal 24 of resilient elastomeric 0 00 o 1 material, is fitted in each dust seal housing 17 and has o an outwardly tapered inner face 25 with a lip 26 which 0300 bears and seals against the cylindrical shaft body 11.

A circlip 27, received in a circumferential groove 28 in the shaft body 11, retains the bearing and seal assembly 15 in the bush housing 13.

In use, the brake cam shaft 10 and conventional nylon bushes are removed.

The hole 14 is drilled in the bush housing and fitted with a grease nipple as hereinbefore described.

Each bush assembly is then inserted into the housing from a respective end, with the annular webs 23 abutting the adjacent end faces of the bush housing 13.

4. N1 6 The brake cam shaft is refitted and the circlip 27 is installed to retain the bush assembly in the housing 13.

Grease is pumped into the housing to lubricate the bush members 21. Excess grease escapes under the lips 26 of the seals 24 to displace any dust adjacent the seals. The lips 26 on the seals 24 re-engage the cam shaft body 11 to prevent the ingress of dust into the bush assembly 10 In a modified embodiment of the invention, the 00 0 9seal 15 may be replaced with a double-lip seal to provide improved sealing engagement between the seal and 0.00. the brake cam shaft.

mebes With regular greasing to lubricate the bush 0 0 1 memersthe bush assembly should last many times the life of the conventional nylon bushes.

Referring to FIG. 2, the arrangement of the '00 bush assemblies 15A is generally as for FIG. 1 except 00 the ends of the bush members 21A are plain and the webs 0 00 20 19A, 22A simply bear against the end f aces of the bush 0 members.

004. Referring to FIG. 3, the bush assemblies a0 00 0 have the bush body and bush member moulded integrally in 0 0 0 a single component from glass -reinforced nylon. Each 00,10 25 dust seal 24B has a metal or stiff-plastic housing received in a dust housing 17B and has three lips 26B which bear on the cam shaf t 11. The operation of the bush assemblies 15B are as hereinbefore described with ref erenace to FIGS. 1 and 2.

The present invention provides a simple, yet highly effective replacement assembly for the existing nylon bushes.

Various changes and modifications may be made to the embodiments described without departing from the scope of the present invention as defined in the appended claims.

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Claims

1. A bush and seal assembly for rotatably supporting a brake cam shaft in a bush housing on a vehicle axle assembly, the bush and seal assembly including: a pair of outer bush bodies to be inserted into the housing from each side; a bush member supported in the outer bush bodies adapted to bear against and support the brake cam 10 shaft; a respective dust seal housing attached to each outer bush body and of greater diameter than the outer bush body and connected to the outer bush body by an annular web engageable with a respective end face of 15 the bush housing; a dust seal in each seal housing having at least one lip engageable with the brake cam shaft so arranged that when grease is pumped into the bush housing to lubricate the bush members, excess grease can 20 escape under the lip or lips of the seal but dust is prevented from entering the bush housing; and wherein the bush and seal assembly is retained in the bush housing by a circlip engaged in a circumferential groove in the brake cam shaft. 25

2. An assembly as claimed in Claim 1 wherein: the bush member is formed of reinforced plastics material.

3. An assembly as claimed in Claim 2 wherein: the plastics material is glass reinforced nylon.

4. An assembly as claimed in Claim 2 wherein: the bush body and the bush member are formed as an integral component.

A brake shaft bush for rotatably supporting a brake cam shaft, including: an outer bush body to be inserted in a bush X\ housing on a vehicle axle assembly; v: I 8 a bush member supported in the outer bush body to bear against and support the brake cam shaft; a seal housing at one end of the outer bush body and of greater diameter than the outer bush body; seal means in the seal housing, the seal means having at least one lip engageable with the brake cam shaft to enable excess grease in the bush housing to escape under the lip of lips but to prevent dust entering the bush housing; and an annular web interconnecting the seal °oo housing and the outer bush body engageable with an end 0 00 o face of the bush housing to locate the outer bush body o"00 in the bush housing; wherein: 0 00 o0 o the bush is retained in the bush housing by o00 0 0oo0 15 a circlip engaged in a circumferential groove in the O O 0 brake cam shaft.

6. A bush and seal assembly for rotatably supporting a brake cam shaft in a bush housing on a .00ooo vehicle axle assembly substantially as hereinbefore o Q o. 20 described with reference to FIG 1; or FIG 2; or FIG 3; oo a of the accompanying drawings. o

7. A brake cam shaft bush substantially as 0000 hereinbefore described with reference to FIG 1; or FIG 2; or FIG 3; of the accompanying drawings. 0O0 0 o 25 DATED this thirteenth day of June 1991. 0ooooo 0 o EDGAR MALCOLM STUBBERSFIELD and BERYL GRACE STUBBERSFIELD By their Patent Attorneys GRANT ADAMS COMPANY. 0. o