GB1602333A - Brakes for vehicles - Google Patents

Description

(54) BRAKES FOR VEHICLES (71) We, ROCKWELL INTERNATIONAL CORPORATION, a corporation of the State of Delaware, U.S.A., of 600 Grant Street, Pittsburgh 15219, Pennsylvania, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to wheel brakes for vehicles and is an improvement in or modification of the invention described and claimed in our co-pending patent application no. 12411/78 dated 30th March 1978 (Serial No 1600535). In a known construction of drum and shoe brake for the wheels of heavy vehicles there is provided a substantial support member within which two spaced apart cylindrical pivot pins are fitted. Bearing bushes may be fitted between the pins and the member. A brake shoe which is a fabrication comprising two webs and a bridge piece to which a friction lining is secured has aligned holes machined in one end of the webs through which a pivot pin fits. The pin is secured by a washer outboard of each web and a circlip which fits in a groove at either end of the pin. Thus, in this assembly there are two brake shoes extending in opposite directions from adjacently situated pivot pins. The other ends of the webs of the brake shoes bear against cam or wedge which, on operation spreads the shoes so that their friction linings engage a brake drum. The shoes are held against the cam by tension springs arranged between the opposed shoes and the whole assembly is located within the brake drum. There is a dust cover behind the shoes which fits closely to the open side of the drum. Access is difficult for removal of the circlip on that end of the pin which is adjacent the duct cover.

The assembly is subject to access of moisture which can cause corrosion between pivot pins and webs. Consequently removal of the brake shoes can be a difficult and time consuming operation. The object of the present invention is to provide an assembly which obviates the aforementioned difficulties and enables brake shoes to be removed and replaced readily and quickly while maintaining secure and reliable operation in use.

According to the invention there is provided a brake assembly including a support member, a brake shoe having parallel spaced webs which are provided at or adjacent one end with aligned part circular openings or recesses, and a pivot pin having reduced diameter neck portions towards each end between a medial large diameter portion which is received in a through bore of the support member and respective large diameter head portions at the ends of the pin whereby, with the pin assembled in the mounting, the shoe web recesses can be engaged with the neck portions of the pin on opposite sides of the support member by movement of the shoes in a direction transverse to the axis of the pin, the webs at said openings or recesses engaging the pin over only a part of the periphery of the pin and engagement of the pin by the respective webs locating and retaining the pin in the support member.

A preferred embodiment of the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a perspective view of part of a brake assembly, and Figure 2 is a drawing of a pivot pin used in said assembly.

Referring to Figure 1, the brake assembly comprises a mounting 1 having bores in which bearing bushes for pivot pins are fitted. One of said pins 15 and one of said bushes 16 only is shown in Figure 1. A brake shoe has parallel spaced webs 11 and 12 which each terminate with a semi-circular recess 13 which fits on a respective reduced diameter neck portion 14 on pin 15. The pair of brake shoes are retained in engagement with their respective pins 15 by springs as 17 between the webs of the opposed brake shoes. As will be seen the webs serve to locate the pins axially and to retain them.

Removal of the brake shoes is accomplished by removal of springs 17 whereupon the ends of the brake shoes can be lifted out of the recesses 14 at the ends of the pivot pins 15. The pivot pins can then be withdrawn.

With this construction any corrosion which occurs will not seriously impede removal of the brake shoes because their webs do not encompass the pins 15 and are engaged on only half of the periphery of the pins. The presence of a dust cover at the back of the assembly does not in any way impede the removal or replacement of the brake shoes or pins.

Referring now to Figure 2, this shows in detail the pivot pin 15 in which there is a reduced diameter neck portion 20 towards each end of the pin providing recesses for reception of the brake shoe webs and a medial large diameter portion 21 which fits in the bush 16 in the mounting 1. The full diameter head portions 22 at the ends of the pin assist in resisting any force tending to cause the brake shoe webs to splay apart.

The pin is retained in the bearing bush due to its stepped construction and the presence of the brake shoe webs on the reduced diameter portion, the brake shoes being held on the pins by the springs 17.

WHAT WE CLAIM IS: 1. A brake assembly including a support member, a brake shoe having parallel spaced webs which are provided at or adjacent one end with aligned part circular openings or recesses, and a pivot pin having reduced diameter neck portions towards each end between a medial large diameter portion which is received in a through bore of the support member and respective large diameter head portions at the ends of the pin whereby, with the pin assembled in the mounting, the shoe web recesses can be engaged with the neck portions of the pin on opposite sides of the support member by movement of the shoes in a direction transverse to the axis of the pin, the webs at said openings or recessed engaging the pin over only a part of the periphery of the pin and engagement of the pin by the respective webs locating and retaining the pin in the support member.

2. An assembly as in Claim 1 in which the periphery of the openings or recesses which engage the neck portions of the pin extend to half the circumference of a circle.

3. An assembly as in Claim 1 or 2 including a pair of said pivot pins each received in respective bores of the support member, and a pair of said brake shoes each having web recesses engaged with the neck portions of a respective pin.

4. An assembly as in Claim 3 including spring means connected between the shoes and acting to retain said web recesses in contact with the neck portions of the pins.

5. A brake assembly substantially as described herein with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. 15. The pivot pins can then be withdrawn. With this construction any corrosion which occurs will not seriously impede removal of the brake shoes because their webs do not encompass the pins 15 and are engaged on only half of the periphery of the pins. The presence of a dust cover at the back of the assembly does not in any way impede the removal or replacement of the brake shoes or pins. Referring now to Figure 2, this shows in detail the pivot pin 15 in which there is a reduced diameter neck portion 20 towards each end of the pin providing recesses for reception of the brake shoe webs and a medial large diameter portion 21 which fits in the bush 16 in the mounting 1. The full diameter head portions 22 at the ends of the pin assist in resisting any force tending to cause the brake shoe webs to splay apart. The pin is retained in the bearing bush due to its stepped construction and the presence of the brake shoe webs on the reduced diameter portion, the brake shoes being held on the pins by the springs 17. WHAT WE CLAIM IS:

1. A brake assembly including a support member, a brake shoe having parallel spaced webs which are provided at or adjacent one end with aligned part circular openings or recesses, and a pivot pin having reduced diameter neck portions towards each end between a medial large diameter portion which is received in a through bore of the support member and respective large diameter head portions at the ends of the pin whereby, with the pin assembled in the mounting, the shoe web recesses can be engaged with the neck portions of the pin on opposite sides of the support member by movement of the shoes in a direction transverse to the axis of the pin, the webs at said openings or recessed engaging the pin over only a part of the periphery of the pin and engagement of the pin by the respective webs locating and retaining the pin in the support member.

2. An assembly as in Claim 1 in which the periphery of the openings or recesses which engage the neck portions of the pin extend to half the circumference of a circle.

3. An assembly as in Claim 1 or 2 including a pair of said pivot pins each received in respective bores of the support member, and a pair of said brake shoes each having web recesses engaged with the neck portions of a respective pin.

4. An assembly as in Claim 3 including spring means connected between the shoes and acting to retain said web recesses in contact with the neck portions of the pins.

5. A brake assembly substantially as described herein with reference to the accompanying drawings.