AU604240B2

AU604240B2 - Brake cam shaft attachment apparatus

Info

Publication number: AU604240B2
Application number: AU73113/87A
Authority: AU
Inventors: Gordon Joseph Taylor
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-05-15
Filing date: 1987-05-15
Publication date: 1990-12-13
Anticipated expiration: 2007-05-15
Also published as: AU7311387A

Description

4.

Rn 4 2 4 0

IA

pl2d r C31 GNTEILTE OF U:.T The Pt-nt Act 19E2-1-6 40 a 0 0 Maaie icnt Gordon Joseph Taylor Aca of 18-Seng Street, Graceville, 4075, Queensland, Australia

DO~

a0 ,a ACtu-a2. T-:Ventcr. Gordon Joseph Taylor

A,

0

A

44 Addrefor G. R. CULLEN COMPANY Pa=tent a-nd T-re M-ark AttOrn-eyS Medcihars Bui- 1 l-"t*a- 821 Ann Sre B R 7 S 7 Z QLD. 4001.

A u st 0 AA -C'CLM:N O T-B IVN:O ETTLD 0 0 404 O 4 BRAKE CAM SHAFT ATTACHMENT APPARATUS The folcw'mc stazerr=:n a f_1_ descr~rtor C ~nve~t~n mcluding2 t-he hest metnoc of cerfor-nC it knc; t o u s -2- SThe invention relates to an assembly for attaching a brake cam shaft to a slack adjuster.

Vehicle brakes in relation to which the present invention may be used usually comprise a brake drum, two opposed brake shoes either pivotally secured at one end to each other or to a brake spider and a cam shaft having a cam member or element at one end and a spline coupling at the other end. The cam element is operative to engage brake rollers secured to the other ends of the shoes and these 10 other ends are normally biassed towards each other and o 00 against the cam element whereby upon rotation of the cam o*ae shaft the rollers are caused to ride over the cam element to c on c o 0o thereby expand the shoes and bring them into contact with o o 0 the brake drum to effect a braking action. In vehicles and in particular in heavy vehicles the cam shaft is rotated by o 0 a slack adjuster which is mounted relative to the splined 0 00o So o end of the shaft and itself has a complementary splined 0 aperture. Pivotal movement is achieved by securing the distal end of the slack adjuster to a piston rod of an air 20 chdmber via a clevis member. Pressurization of the air o oo 00 0 .000 chamber causes the piston rod to extend from the chamber and 0 this piston rod is coupled to the clevis member. This extension or stroke of the piston rod pivots the slack adjuster and in turn rotates the cam shaft. The purpose of slack adjusters is well known. Such slack adjusters are designed and used to remove any slack from the brake caused by wear of the brake shoes.

I MI MW -3- Traditionally, the splined end of the cam shaft was formed with a groove for receiving a circlip. The circlip receiving groove was located adjacent the end of the shaft at which the spline was formed. The shaft was assembled and positioned relative to the slack adjuster by engaging the spline of the shaft with the internal spline of the slack adjuster. Upon engagement and proper positioning of the cam elements of the shaft the circlip was then positioned relative to the shaft. The circlip served only to inhibit 1 O longitudinal movement of the shaft in one direction, that o a 0 is, away from the cam elements. Relative movement of the o o shaft and slack adjuster was otherwise possible in the o 0 o longitudinal direction whilst the splines were in 0 engagement. The extent of the movement depended upon play between the clevis member and the distal end of the slack adjuster as well as on any clearance between these two 0o 00 splines. If the freedom of movement of the cam shaft was o 00 excessive then this led to undue wear of the spline and in 0o some instances damage to the vehicle brake and possibly to the axles about which the brake drums were mounted. In addition, this circlip type connection tended to damage the 0a side plate of the slack adjuster.

It is an object of the present invention to provide a brake cam shaft attachment assembly which at least minimises some of the disadvantages referred to above.

According to one aspect of the invention there is provided a brake cam shaft attachment assembly for attaching 4 a brake cam shaft relative to a slack adjuster, the slack adjuster having an opening therethrough with a spline formed therein, said assembly including the cam shaft having cam elements at one end thereof and a threaded attachment portion at the other end thereof, a spline on said shaft adjacent said attachment portion, a circlip locatable about and to the shaft at a location spaced from the one end, said circlip limiting the extent to which the splined end of the shaft projects into the splined aperture of the slack adjuster, a o,0 washer locatable about the other end and a threaded fastening I means securable to said attachment portion at the other end whereby, when said shaft is secured relative to the slack adjuster, the shaft is locked fast to the slack adjuster to prevent relative longitudinal movement with the latter located on the shaft and between said circlip and said washer or eno\ with the washer clamped against., -se face of the spline of the slack adjuster by said fastening means.

The attachment portion provided at the other end of Sthe shaft may be of a diameter less than the diameter of the shaft.

The circlip may be locatable in a circlip receiving groove formed on the shaft adjacent to

-L)

o y 4 0 ios A -NU I rp~ IIC 1 and spaced from the other end of the shaft.

Where a circlip is employed it is preferable that a spacer be positioned between the circlip and the slack adjuster. This ensures that the circlip does not engage upon a side face of the adjuster which may lead to damage of either the adjuster of the circlip. It is usual for the shaft to be journalled for pivotal movement about one or more bearings or bushes positioned along the length of the shaft between its ends. Preferably a second spacer is employed between the circlip and an adjacent bearing or bush. This ensures that the bearing or bush does not contact the oi o circlip. In one embodiment the or each spacer may comprise a 00 washer.

SThe fastening means which secures the attachment portion of the shaft relative to the slack adjuster may be in jI the form of a fixing member which may be secured relative

I'

i '<y r' -6to the attachment portion to clamp the slack adjuster between it and the securing member. In one embodiment the fixing member comprises a threaded fastener. Preferably the threaded fastener is a locking fastener to ensure that once attached to the attachment portion it cannot readily be undone or dislodged by vibration or the like. Preferably the locking fastener comprises either a lock nut or a nut together with a spring washer. Preferably the fastening ij means also includes a washer against which the lock nut or So D nut may locate when the assembly is put together.

A particular preferred embodiment is illustrated in a S the drawing which shows an exploded perspective view of an assembly according to the invention.

oI The assembly 10 includes a cam shaft 11. Shaft 11 S 15 has cam members 12 and 13 integrally formed at one end thereof. Cam members 12 and 13 cooperate with brake shoe .4.

i rollers and ensure that the shoes are biassed apart upon K rotation of the shaft 11. The other end of the shaft is formed with a reduced diameter threaded attachment portion 14. Adjacent portion 14 the shaft is provided with a spline The shaft 11 has zones 16 and 17 which may be i! journalled relative to bearings or bushes (not shown) to mount the shaft 11 for rotation. Spacer washer 18 ensures that the bearing or bush which locates about shaft portion 17 does not engage or interfer with circlip 19. Circlip 19 is received within circlip groove 20 and this groove locates the circlip at a point spaced from the end of the shaft at IU--*U I' -7- ;-which the threaded attachment portion 14 is located. A further spacer washer 21 is located on the opposite side of circlip 19 to that at which spacer washer 18 is located.

The slack adjuster 25 may be coupled to an air chamber (not shown) via a clevis member (not shown). The clevis member may be secured to a select one of apertures 26, 27 and 28 which are located at the free end of the slack adjuster. The slack adjuster 15 has a through bore formed with a spline 29. The spline 29 has end faces 30 only one 10 of which is visible in the exploded view of the drawings. A sQ t circumferential raised portion 31 extends around each end 050010 S face 30 of the spline of the slack adjuster. The face of gate the slack adjuster (not visible) is constructed in a similar 0 S fashion. Spacer washer 21 locates against spline face 30 on the adjacent side of the slack adjuster whereas washer 32 locates within raised portion 31 and against face 30 of the side of the slack adjuster 25 visible in the drawing. Lock nut 33 has an integrally formed locking ring 34.

0 00+ To assemble the arrangement shown in the drawing spline 15 is brought into engagement with spline 29 and in S this way threaded attachment portion 14 projects through the opening in the slack adjuster. Spacer washer 18 locates around the shaft 11 and cannot move towards the end of the shaft having the threaded portion 14 because circlip 19 locates in groove 20. Circlip 19 cannot contact the spline face 30 on the other side of the slack adjuster because the spacer washer 21 is interposed. Once portion 14 projects -8through the opening in the slack adjuster washer 32 is positioned over portion 14 and the lock nut 33 is threaded onto portion 14 until washer 32 is pressed against face Thus, with the lock nut 33 tightened in the manner described above the slack adjuster 25 is securely held between circlip 19 and washer 32 with spacer washer 20 interposed between it and the circlip. In this way the shaft 11 is securely locked relative to the slack adjuster and cannot move longitudinally in either direction.

The assembly of the invention relative longitudinal movement between the cam shaft and the slack adjuster is o eliminated and damage or wear between the splines which may Sbe caused by longitudinal relative movement between the S 1 shaft and the slack adjuster does not occur.

S 4 c ij 4 2 CC C< I CC

Claims

1. A brake cam shaft attachment assembly for attaching a brake cam shaft relative to a slack adjuster, the slack adjuster having an opening therethrough with a spline formed therein, said assembly including the cam shaft having cam elements at one end thereof and a threaded attachment portion at the other end thereof, a spline on said shaft adjacent said attachment portion, a circlip locatable about and to the shaft at a location spaced from the one end, said circlip limiting the extent to which the splined end of the shaft projects into the splined aperture of the slack adjuster, a washer locatable about the other end and a threaded fastening means securable to said attachment portion at the other end 0 4 whereby, when said shaft is secured relative to the slack adjuster, the shaft is locked fast to the slack adjuster to prevent relative longitudinal movement with the latter t"'r located on the shaft and between said circlip and said washer with the washer clamped against ia si.d- face of the spline of the slack adjuster by said fastening means.

2. The attachment assembly of claim 1, wherein the Sfastening means comprises a screw threaded fastener engageable with the attachment portion.

3. The attachment assembly of claim 1 or 2, including a spacer locatable on the shaft and between the circlip and the slack adjuster.

4. The attachment assembly of any one of claims 1 to rV t Y' C r n LF- ~~p 3, wherein said shaft is journalled for rotation relative to one or more bearings or bushes and the assembly includes a further spacer locatable on the shaft between the bearing or bush and the circlip.

The attachment assembly of any of of claims 1 to 4, wherein said fastening means comprises a lock nut.

6. A brake cam shaft attachment assembly substantially as herein described with reference to the drawing. DATED this twenty-sixth day of July 1990. GORDON JOSEPH TAYLOR ~Da «By His Patent Attorneys CULLEN CO C C t .j i ^X 1 'r