GB2153462A

GB2153462A - Drum brake

Info

Publication number: GB2153462A
Application number: GB08500215A
Authority: GB
Inventors: Herbert Schmidt
Original assignee: Alfred Teves GmbH
Current assignee: Continental Teves AG and Co oHG
Priority date: 1984-01-26
Filing date: 1985-01-04
Publication date: 1985-08-21
Also published as: FR2558909A1; DE3402530A1; BR8406353A; FR2558909B1; GB8500215D0; GB2153462B; DE3402530C2

Abstract

In a drum brake, the anchor plate (1) is formed from a comparatively thin-walled metal plate and the anchor seat (7) to support the ends (3', 4') of the two brake shoes (3, 4) is drawn from a plate metal blank in the shape of a trough and is coupled directly to web (25) of vehicle axle shank by means of a rivet or a bolt (16), the web (25) absorbing braking torque. The anchor seat (7) has two flaps (23, 24) to prevent the ends (3', 4') of the brake shoes (3, 4) from slipping off. At seat (7) two studs (17, 18) are shaped by stamping and engage in depressions (19, 20) in anchor plate (1). Bolt (16) shown has collar or neck (27) clasped by bottom portion (15) of seat (7). The brake incorporates an adjusting wedge (11). <IMAGE>

Description

SPECIFICATION Drum brake This invention is related to a drum brake with two brake shoes taking support at a brake carrier, with a wheel cylinder to actuate the brake shoes and with a stationaryanchorseatto support the free ends of the brake shoes.

A drum brake is known (U.S. Patent 4,337,851) in which instead of a circular disc-shaped anchor plate or support plate a two-web back element is provided which is stamped from a plate metal blank and which is bolted to two anchor seats drawn from metal plate, both ofwhich serve to jointly support the ends of the two brake shoes. Thetorque occurring during braking action is transmitted through the pair ofanchorseats to the two-web back elementwhich is, on its part, bolted to the axle shank. It is a disadvantage ofthis configuration of the brake thatthe back side ofthe brake is not protected from dust and dirt.In addition, the two-web back element has to be manufactured from very heavy-walled metal plate, as a result whereof both the weight of the brake and also the costs of manufacture are increased.

The present invention has for an object to create a drum brake whose weight is considerably reduced as against comparable known versions. Moreover,the costs of manufacture are to be lowerthan for conventional drum brakes of comparable performance owing to the use ofthin-walled material. Finally, mounting and unmounting ofthe drum brake are to be practicable with particular ease and by mechanical means.

According to the present invention there is provided a drum brake with two brake shoes taking support at a brake carrier, with a wheel cylinderto actuate said brake shoes and with a stationary anchor seat to supportthefree ends of said brake shoes, characterised in thatthe said anchor seat is trough shaped and is deep-drawn from one plate metal blank as a separate element, the bottom portion of said anchor seat being coupled in use ofthe brake on a vehicle, togetherwith the anchor orsupport plate, with a web of an axle shank ofthevehicle by means of a rivet or bolt.

The trough-shaped anchor seat is preferablyfurnished at the peripheral edge facing away from the anchor plate, with tongues orfiaps bent off outwardly which straddle the free ends ofthe brake shoes, as a result whereof it is safeguarded that the brake shoes do not shift in the direction ofthe flange portion ofthe brake drum.

In order to orderto preventtheanchorseatfromtwisting relative to the anchor plate, the bottom portion of the trough-shaped anchor seat is provided with studs extending in the direction ofthe web of the steering knuckle and engaging in depressions or recesses which are provided in the anchor plate.Advan tageousiy, the bolt passing through the bottom portion ofthe anchor seat is provided with a collar or a neckwhich is clasped with preload bysaidbottom portion sothatthe bolt is captively connected with the anchor seat An embodimentofthe invention will now be described, by way example, with reference to the accompanying drawings, in which: Figure 1 isthetop plan view of a drum brake; and Figure 2 is the longitudinal section through the anchor seat for the brake shoes of the drum brake according to Figure 1.

As shown in Figure 1,the drum brake is comprised of a brake carrier in the shape of an anchor plate 1 which bears a wheel cylinder 2. Two brake shoes 3 and 4 are urged against the wheel cylinder 2 and against an anchor seat7 by means of return springs Sand 6, respectively.

Atthe brake shoe 4, a parking brake lever8 is swivellingly pivoted with the aid of a pin 9 nearthe wheel cylinder 2. Whereas the wheel cylinder2 urges the two brake shoes 3 and 4 into braking position in the event of the supply of hydraulic brake fluid, the parking brake lever8 is coupled to an operating lever notshown in the drawing in orderto mechanically or manually operate the drum brake and bring the two brake shoes 3,4 into braking position. An intermediate member in the shape of a brake strut 10 extends from the parking brake lever 8 to the second brake shoe 3 so that both brake shoes 3,4 are pivoted about the anchor seat7 and are thereby expanded into braking position when the parking brake lever 8 is swivelled aboutthe pin 9 in clockwise direction as viewed in Figure 1.

Between the brake shoe 3 and the brake strut 10, there is arranged a self-lockinglydimensioned adjusting wedge 11 which is abutted againstthe brake shoe 3, that is to say, against a support plate 13 with its left conical face and against the end of the brake strut 10 with its right conical face. The brake strut 10, the adjusting wedge 11 and the brake shoe 4 are braced to one another by means of an abutment spring 12.

When the brake is not operated, the two brake shoes 3 and4are pulled toward each other by the action of return springs 5 and 6 and are brought in abutment againstthe ends ofthe strut arrangement,thetravel performed byte the brakebrakeshoesfromtheirabutment against the brake drum to their abutment against the brake strut 10 determining the clearance ofthe drum brake.

On hydraulic actuation ofthe brake, the brake shoes 3 and 4 move apart fro each other, the brake strut 10 moving along with the right brakeshoe4 because of the bracing together of the brake shoe 4, the adjusting wedge 11 and the brake strut 10 by means ofthe abutment spring 12, so thatthe parking brake lever8 travelling to the rightjointlywith the righthand brake shoe 4 lifts off from the end of the brake strut 10. In consequence of this relateve movement between the brake lever8 on one hand and the brake strut 10 on the other hand, a gap between the brake lever 8 and a hook-shaped extension ofthe brake strut 10 predeter- mining the rated clearance is reduced.As soon as the brake shoes 3 and 4 move away from each other a distance largerthan the rated clearance, the hookshaped extension comes in abutment, as a result whereof the brake strut 10 is forced to move with the parking brake lever8 against the force of the abutment spring 12. The bracing between the brake strut 10, the adjusting wedge 11 and the brake shoe 4 is then cancelled, so that the adjusting wedge 11 is pulled deeper into the gap betweenthe brake shoe and the brake strut 10 by the action ofthe adjusting spring 14, increasing the effective length ofthe strut arrange mentand so adjusting the clearance. Indeed, such an adjusting procedure is as a rule, caused by the wear of the linings.

The simplex brake illustrated in Figure 1 is provided with an anchor seat 7, to supportthe free ends ofthe brake shoes 3,4, which is drawn in one piece from a plate metal blank and which has the shape of a forwardly open trough. The bottom portion 15 of the trough-shaped anchorseat7 is bolted to the anchor plate 1 by means of a bolt 16. Atthe anchor seat 7, two studs 17,18 are shaped by stamping which engage in correspondingly shaped depressions 19,20 provided in the anchor plate 1,so thattwisting ofthe anchor seat 7 around the bolt 16 is excluded. In addition, at the two lateral portions 21,22 ofthe anchor seat 7 which face the ends of the brake shoes 3,4, there are provided flaps 23,24 bent off outwardly which prevent the ends of the brake shoes 3, 4from slipping off from the anchorseat7.

In Figure 2, a web 25 ofthe axle shank ofthe vehicle is indicated, said web 25 directly absorbing the torque which occurs during braking action, so that the anchor plate 1 is relievedfrom any braking forces. It is a vital advantage ofthe described anchorseat7which is directly coupled to the web 25 ofthe axle shank bythe bolt 16thatthe anchor plate 1 is allowed to be manufactured from comparatively thin-walled plate metal, since it is not required to absorb any appreciable forces. The bolt 16 is provided with a collar or neck 27 which is clasped with preload by the bottom portion 15.

Claims

1. A drum brake with two brake shoes (3,4) taking support at a brake carrier, with a wheel cylinder (2) to actuate said brake shoes (3,4) and with a stationary anchorseat (7) to supportthefree ends (3', 4') of said brake shoes (3,4), characterised in that the said anchor seat (7) istrough-shaped and is deep-drawn from one plate metal blank as a separate element, the bottom portion (15) ofsaid anchorseat p) being coupled in use of the brake on a vehicle, together with the anchor orsupport plate (1), with a web (25) of an axle shank of the vehicle by means of a rivet or a bolt (16).

2. A drum brake as claimed in claim 1, characterised in thatthe said trough-shaped anchor seat (7) is furnished at its peripheral edge (26) facing away from the said anchor plate (1), with tongues offlaps (23,24) bent off outwardly which straddle the free ends (3', 4') ofthe said brake shoes (3,4).

3. A drum brake as claimed in claim 1 orclaim 2, characterised in thatthe said bottom portion (15) of the said trough-shaped anchor seat (7) is furnished with studs (17,18) extending in the direction of said web (25) ofthe axle shank and engaging in depressions or recesses (19,20) which are provided in the said anchor plate (1).

4. A drum brake as claimed in any one ofthe preceding claims, characterised in that the said bolt (16) passing through the said bottom portion (15) of the said anchor-seat (7) is provided with a collar or a neck (27) which is clasped with preload by the said bottom portion (15).

5. Adrum brake substantially as herein described with referenceto and as illustrated in the accompanying drawings.