CA1150164A - Roller retainer for brake assembly - Google Patents

Abstract

ROLLER RETAINER FOR BRAKE ASSEMBLY
Abstract of the Disclosure A roller retainer for a cam actuated vehicle brake assembly comprising a member preferably formed from spring wire to provide two substantially parallel legs with a tang at the end of each leg and a manual grip intermediate the legs, The tangs are seated in apertures provided to a dual web brake shoe and a portion of the member inter-mediate the manual grip and the tanged ends extends only partially around the roller so the manual grip and the tanged ends are disposed on the same side of a reference plane parallel to the legs and passing through the axis of the roller. This enables the retainer to be rotated about the apertures thereby allowing the roller to be safely removed from the brake shoe while the shoe remains in the assembly without the use of any tools.

Description

~'` ~- 1 -: Roller retainer for brake assembly Backaround of the Invention Field of the Invention ; ~ The present invention is directed to an improvement ~: in a vehicle brake mechanism and more specif;cally to a roller retainer for a cam actuated brake assembly.
:~ The invention is particularly useful in a brake assembly of the type disclosed in U.S. Patent No.
:~ 4,206,834 issued on June 10, 1980. That brake assembly includes a paîr o~ brake shoe~ having adjacent ends ~: 10 pivotally mounted to a support and a rotatable actuating cam disposed between the other ends of the brake shoes.
: A roller-type cam follower is provided between each of : those other ends of the brake shoes and the actuating cam. The roller-typ~ cam followers are seated in open-ended recesses provided to the brake shoes. Rotary :~ movement of the actuating cam is applied to the roller-~: type cam followers which cause their respective brake ; shoes to pivot outwardIy about their pivot or anchor pins to contact the inwardly facing friction surface of a brake drum.
The roller-type cam followers are comprised of a ~ stepped cylindrical steel pin having a center portion j which bears against the actuating cam and smaller dia-meter end portions which serve as trunnions seated in the open ended recess provided to the spaced webs of a dual .!i, ~ ' , ' ', ' ' ' ' ' ' ' ' , ' . .

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- la -,~ web brake shoe. Under normal conditions, the roller-type ~. cam follower is trapped between the open ended recesses s provided to the dual web brake shoe and the bearing sur-face of the actuating cam and held in that arrangement by the brake -/

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-2-return spring. However, the brake assembly is comprised of a number of different parts and it is also advantageous to maintain the cam followers in the recesses provided to the brake shoes during assembly and disassembly of the brake 5 mechanism for repair purposes. This limits the number of parts the mechanic has to be concerned with at any given time and the attendant possibility of dropping and losing the relatively small c~m-follower rollers.
It has also become known that means for retaining 10 a roller between the actuating cam and the open recesses provided to the ends of the brake shoe is also beneficial under conditions where the brake assembly is not maintained '~ in adjustment particularly during extremely cold weather.
Under such conditions, rollers have become displaced from 15 their position in the open-ended recesses of the brake shoe webs which of course adversely affects operation o~ the brake assembly.
It is also desirable for assembly and maintenance pur-~ poses if the roller retaining means allow the cam-follower '~ 20 roilers to be appLied and removed withouttheuse of anytools.
Descri~tion o~ the Prior Art U.S. Patent No, 3,114,437 discloses one method of ` retaining a roller-type cam follower in open-ended recesses provided to brake shoes, In t~at patent the mouth of the 25 open-ended recesses is formed to retain the ends of the ~, rollers and a tool such as a screw driver may be required } to remove the rollers from the brake shoes.
s A spring has also been employed to retain a roller in i its brake shoe during transfer andassembly. The prior art ;~ 30 spring retainedthe roller satisfactorily but the roller could not be withdrawn from the brake assembly without risk o~ in-jury to the mechanic's hand. The dis-tance required for the retainer spring to clear other componentsof thebrake assembly ;
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~ 3 is such that a screwdriver or other tool was often used as a pry bar to expand the return spring.
_ mmarY of the Invention According to the invention there is provided in a rotary cam actuated vehicle brake assembly including a pair of brake shoes with each brake shoe having a pair of spaced parallel webs, a rotary cam between adjacent ends of said brake shoes, and a roller type cam follower between said cam and said adjacent end of at least one of said brake shoes, said cam follower having a pair of trunnions seated in open recesses provided at the ends of said one brake shoe web, the improvement comprising:
~; a roller retainer member secured to said one brake shoe and having two substantially parallel legs, a manual grip intermediate said legs and located on one side of a reference plane defined by said legs and a portion of said member intermediate at least one of said legs and said manual grip on the other side oE said reference plane formed to extend only partly around the circumference of a roller trunnion surface.
In its pre~erred forms, the present invention is a roller retainer for a vehicle brake assembly comprising a member Pormed to provide two substantially parallel legs ; with a tang formed at the end of each leg, a manual grip formed in the member intermediate the legs and at least one portion of the member intermediate the tangs and the grip formed to extend in one direction circumferentially around part of a roller with the legs of the member ex-tending tangentially away from the roller in the other circumferential direction. The roller retainer is pre-- ferably formed from a length of spring wire and is used in combination with a brake shoe having a dual web structure in which the webs are formed with similar and laterally aligned open end recesses and an aperture adjacent each recess. The tangs formed at the ends of each leg of the retainer are seated in one of the apertures and a portion .
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of each leg intermediate the manual grip and the tang extends partially around one of the roller trunnions and returns around that same portion of the roller trunnion ;` so the manual grip and the tangs are disposed on the same ~; 5 side of a reference plane parallel to the legs and passing through the axis of the roller. This arrangement enables the retainer to be rotated about the apertures thereby allowing the roller to be safely removed from the brake shoe while the shoe remains in the assembly without the use of any tools.
The invention and the advantages offered thereby will ~; become apparent from the following detailed description of ~;~ the embodiment shown by the accompanying drawings.
Brief Description of the Drawings .`;:
~ 15 In the drawings wherein like reference numerals refer ;i, to like parts:
,; ~ Figure 1 is a side elevation, partly in section, of a brake assembly according to the present invention;
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Figure 2 is an enlarged view o~ a portion of Figure 1 showing the roller retainer of the present invention;
Figure 3 is a section on line 3-3 of Figure 2;
Figure 4 is a view similar to Figure 2 but showing a 5 prior art roller retainer;
Figure 5 is a plan view of tlle roller re~ainer of the present invention;
Figure 6 i~ a side elevatlon of the roller retainer of the present inven~ion; and Figure 7 is a end elevation o~ the roller retainer of the present invention.
: Description o~f the Invention ~' With reference to the drawings there is shown a cam actuated brake assembly generally designated by the numeral 15 10. The brake assembly 10 is supported b~ a spider 11 ri~id with a vehicle axle housing 12. The brake assembly 10 includes a pair of brake shoes 14 each of which is pivotally mounted by a recess 16 at one end to an anchor pin 15 carried by the spider 11. A cam 19 is ~ounted or rotary 20 movement between the adjacent ends of the brake shoes 14 opposite from the anchor pins 15. The brake shoes 14 are each provided with a ro}ler type cam follower 20. The cam is nonrotatably secured to a cam shaft mounted to the - spider for rotary movement by conventional means to rock 25 the cam 19 in a clockwise direction through an arc ln the range of about 10 to 30 degrees, The cam 19 provides an outwardly direc~ed force to:the rollers 20 and the brake :: shoes 14 which cause the brake shoes to pivot about the -: anchor pins 15. This movement orces friction lining pads : 30 24 carried by the brake shoes 14 into contact with the inwardly facing friction surface 26 of a brake drum 25 secured by conventional means to a wheel rotatably mounted to a spindle at the outer end of axle housing 12. I~hen the brakes are released the brake shoes 14 and the friction 35 lining pads 24 are withdrawn fro~ contact with the brake drum surface 26 by a return spring 28 secured at its opposite ends to the brake shoe webs.
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The brake shoes 14 are dual web fabricated brakeshoes.
That is, each brake shoe includes a pair of axially spaced webs 31 secured to a table 32. The webs 31 are flat in a radial direction and curved in a longitudinal or circum-ferential direction. The brake shoe table 32 is~curvedin the circumferential direction and the webs 31 are welded in parallel relation along the interior curved portion of the table. This provides a generally rigid assembly of component parts to which the friction lining pads 24 may be secured by rivets or by chemical bonding.
Each of th~ brake ~ho~ webs 31 is provided with an open recess 34 opposite the cam follower 20 and an aperture 36 adjacent thereto. The recess 34 is in the form of a slot which includes an inner arcuate bearing surface or lS journal 35 and a mouth formed by integral brake shoe por-tions. The recesses are identical and laterally aligned.
! The bearing surfaces 35 are semi-circular bearing suraces and are adapted to engage a complementary arcuate surface of the generall~ cylindrical end portion 22 of the ca~
~` 20 follower roller. As best shown b~ Figures 2 and 3 each cam roller ollower 22 is comprised of a cylindrical roller surface 21 located intermediate the brake shoe webs 31 and ~ supported by coaxial reduced diameter cylindrical shaft i sections or trunnions 22 seated in the arcuate journal sur~ace 35.
Each roller type cam follower 20 is retained in its respective recess 34 by a roller retainer 40. As best shown in Figures 5-7 the roller retainer 40 is preferably formed from a continuous length of steel spring wire. The stock wire is cut to a length of about twelve inches and formed to provide a "U" shaped manual grip 41 and two sub-stantially parallel legs 42 and 44 and a tang 46, 48 at the end of each respective leg 42, 44. The roller retainer legs ' 42,44 are each respectively bent in a "U" shape or hairpin type bend and arcuately formed at 50 and 52 to e~tend ` circumferentially around a portion of a cam follower roller ~; trunnion 22 and to return partly around that same circum-feren~ial portion with each tang 46, 4~ seated in an aperture ;. 36.

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' With reference to Figures 5-7, the intermediate por-, tions 50, 52 of the legs 42, 44 are tangentially curved at ,~ x to project in one direction away from a reference plane `; m defined by the manual grip 41, rather sharply bent in ,~ 5 the form of a hairpin bend to return in the direction of ~'; the reference plane m and tangentially curved at y to again project away from the same side of the reference plane m. The intermediate portions 50, 52 of the legs ~ 42, 44 are preferably accurately formed between x and y '`~ 10 to fit snugly and partly around and to resiliently embrace ~ the trunnions 22 of a roller cam follower 20.
!~ " The roller retainer 40 is formed as described above so the manual grip 41 and the tangs 46, 48 formed at the ends of the legs 42 and 46 are both disposed in the brake ~- lS assembly on the same side of a reference plane n, see Figure 2, parallel to the legs 42, 44 and passing through ~ ~ the axis of the roller type cam follower 20.
!','~ '; Figures 2 and 6 also show the manual grip 41 located on one side of a plane passing through the legs 42, 44 and ~, 20 the arcuately formed intermediate portions,50, S,2 of the }};;~ roller retainer 40 on the other side of that plane. This is accomplished by forming the intermediate portions 50, c'' 52 of each leg 42, 44 to extend circumferentially in s one direction, i.e. clockwise as shown in Figs. 2 and 6, 25 partly around the trunnion 22 of a cam follower and to return with the legs 42, 44 extending tangentially away ~! from the trunnion in the other circum~erential direction~
,;;, The roller retainer 40 with the tangs 46, 48 secured in the apertures 36 secures the trunnions 22 against the 30 journal surfaces 35. The manual grip 41 is formed long ~ and wide enough so as not to interfere with rotary move-,~ ment of the cam 19 and is used to withdraw the roller ~' retainer 40 when the brake assembly 10 is dismantled for ,, servicing.
~' 35 When the brake assembly 10 is to be dismantled the drum 25 is withdrawn and one of the brake shoes (preferably :. .. ~ .
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, ~ 7 -the lower shoe) 1~ is manually rotated about its anchor pin lS to expand the return spring 28. The manual grip 41 of the retainer 40 is then rotated radially outwardly about the apertures 36 to free the roller type cam fol-lower without traversing the reference plane n. Thecam follower is then withdrawn from that brake shoe.
The other brake shoe 14 is then manually rotated about its anchor pin. The manual grip of the roller retainer associated with that brake shoe is rotated to free the cam follower which is then removed. The brake shoe re-turn spring 23 is free of tension with the roller type cam followers removed and the spring 28 may be manually withdrawn. One brake shoe, preferably the lower shoe, is then rotated approximately 180 to relieve the tension on and thereby permit removal of the anchor end retaininy springs 17. The brake shoes can then be manually with-drawn from the anchor pins and new or relined brake shoes -~ substituted therefor. Except for removal of the brake drum the brake assembly can be dismantled manually with-out the use of any tools and without substantial risk of injury to the mechanic.
Figure 4 illustrates a prior art roller retainer 60 used to secure a cam follower 20 in a recess formed at the end of a brake shoe web 31. The prior art retainer 60 is comprised of a "U" shaped manual grip 61 and a pair of legs with a tang formed at each end of each leg. One leg 62 and its tang 66 are depicted in Figure 4. The other leg and tang are similar but disposed on the opposite side of the cam follower 20. The legs are formed to curve partly around the trunnions 22 of the cam follower with the manual grip 61 disposed radially interiorly of the cam follower 20 and the tangs disposed radially outwardly of the cam follower 20. This poses a serious problem while attempting to dismantle the brake assembly since the manual grip 61 has to be rotated about the apertures 36 to free the cam follower 20. This requires the brake : ,~

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~' - 7a -shoe 14 to be moved a substantial distance away from the x cam 19 to permit the manual grip 61 to clear the cam 19 and such movement creates a large tensile force on the .~ return spring 28. The force is of such a magnitude as to ~ 5 present a substantial risk of injury to the fingers of a x~ mechanic attempting to rotate the manual grip 61 between ~,~ the cam follower 20 and the cam 19.
The roller retainer 40 as previously described and claimed hereafter does not present such a risk since the :
manual grip 41 and the tangs 46, 48 are disposed on the same side of the reference plane n and the arcuately .:~ curved lntermediate portions 50, 52 can be easily with-drawn with far less tensile stress on the return spring 28 and without '~
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having to manually move the retainer between the cam follow-er and the cam. The roller retainer of the present inven-tion thus provides for ease of assembly and dlsassembly while avoiding the risk of personal injury attendant the S use of the Figure 4 type of prior art roller retainer.
The invention may also be embodied in other specific forms without departing from the spirit or essential char-acteristics thereof. The roller retainer may be formed from a synthetic material, stamped from a thin steel pla~e or fabricated as a combination of separate elements. The foregoing description is therefore to be considered as illustrative and not restrictive, the scope of the invention being defined by the appended claims, and all changes which come within the meaning and range of equivalency of the claims are ~herefore intended to be embraced thereby.
- ~hat is claimed and desired to be secured by letters `~ patent is:

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Claims (8)

Claims:

1. In a rotary cam actuated vehicle brake assembly including a pair of brake shoes with each brake shoe having a pair of spaced parallel webs, a rotary cam between adjacent ends of said brake shoes, and a roller type cam follower between said cam and said adjacent end of at least one of said brake shoes, said cam fol-lower having a pair of trunnions seated in open recesses provided at the ends of said one brake shoe web, the improvement comprising:
a roller retainer member secured to said one brake shoe and having two substantially parallel legs, a manual grip intermediate said legs and located on one side of a reference plane defined by said legs and a portion of said member intermediate at least one of said legs and said manual grip on the other side of said reference plane formed to extend only partly around the circumference of a roller trunnion surface.

2. The roller retainer member defined by claim 1 wherein said portion of said member intermediate said leg and said manual grip is formed to resiliently embrace said part of said roller trunnion surface.

3. The roller retainer member defined by claim 2 wherein said portion of said member is formed from a resilient material.

4. The roller retainer member defined by claim 2 wherein said portion of said member is formed from spring wire.

5. The roller retainer defined by claim 1 wherein said member is formed from a continuous length of spring wire and a portion of said member intermediate each leg and said manual grip on said other side of said reference plane is formed to extend only partly around and resil-iently embrace the circumference of a roller trunnion surface.

6. In combination, a brake shoe having a dual web struc-ture, said webs being formed with similar and laterally aligned open end recesses and an aperture adjacent each of said recesses, a cam follower having a roller intermediate the webs and trunnions supported in said recesses and a roller retainer comprised of a manual grip and a pair of spring legs extending therefrom, each leg having an end formed as a tang seated in one of said apertures and a portion of said retainer intermediate said manual grip and each leg formed to extend partially around one of said roller trunnions and to return around that same portion of said roller trunnion whereby said manual grip and said legs are disposed on the same side of a reference plane parallel to said legs and passing through the axis of said roller and said manual grip can be rotated about said apertures to free said cam follower without travers-ing said reference plane.

7. the combination defined by claim 6, wherein said roller retainer is formed from a continuous length of spring wire.

8. The combination defined by claim 6, wherein said roller retainer is formed from a continuous length of spring wire and said manual grip is comprised of a "U"
shaped portion of said wire.