GB1600535A - Brake assembly anchor pin - Google Patents

Description

(54) BRAKE ASSEMBLY ANCHOR PIN (71) We, ROCKWELL INTERNATIONAL CORPORATION, a corporation of the State of Delaware, U.S.A., having a place of business at 600 Grant Street, Pittsburgh, Pennsylvania, U.S.A., 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.

The present invention is directed to certain improvements in vehicle brake mechanisms and, more specifically, to an anchor pin for a vehicle brake assembly of the kind described in our copending British patent application No 1 580 963 dated3lstMarch 1977.

The invention is particularly useful in a rotary cam actuated brake assembly which includes a pair of brake shoes having adjacent ends pivotally mounted to a support and a rotatable actuating cam disposed between the other ends of the brake shoes. Rotary movement of the cam causes each of the brake shoes to pivot outwardly about its pivot or anchor pin to contact the inwardly facing friction surface of the brake drum. This type of brake assembly is used for heavy duty brake applications which may employ a dual or a single web brake shoe. The brake shoes may be cast or fabricated. The brake shoes may also carry a roller type cam follower on the ends adjacent the actuating cam. The opposite adjacent ends of the brake shoes may be mounted for pivoting movement about a single anchor pin as disclosed in United States Patent No. 3 398 814 or each shoe may be pivotally mounted for movement about one of a pair of spaced anchor pins as disclosed in United States Patent No. 3 114437.

In one known construction duel web brake shoes for brake assemblies employing a pair of spaced anchor pins are provided with axially aligned, laterally extending bores in each of the webs at the end of the shoe to be pivotally mounted to the support. The brake shoes are mounted to the assembly by aligning the web bores on opposite sides of a bore through a boss formed on the brake support or spider and inserting a pin axially through the spider bore and the coaxial brake shoe bores.The pin, generally referred to as an anchor pin, may be press fit to the boss or locked against rotation by a set screw or other means. Snap rings may be provided to the axially extending ends of the pin to prevent substantial axial displacement of the anchor pin relative to the support. The foregoing arrangement fixes the brake shoe against substantial movement relative to the support except for the desired pivoting movement about the anchor pin. In this type of brake assembly the anchor pin must be withdrawn from the spider bore when it becomes necessary to remove the brake shoes for the purpose of replacing or relining the same.

The object of the invention is to provide a brake assembly, and in particular a brake shoe anchor pin therefor, which can be readily assembled and dis-assembled, is strong and reliable in use, and of simple and inexpensive construction.

According to a first aspect of the invention there is provided the combination of a brake shoe and an anchor pin for a vehicle brake assembly, said shoe having a pair of spaced webs defining open ended laterally aligned recesses at one end portion of the shoe remote from an opposite end portion on which actuating mechanism of the assembly acts in use, and the anchor pin being an elongate body having axially spaced cylindrical bearing areas dimensioned to radially, slidably receive said recesses and a pair of locating surfaces facing in axially opposite directions and extending radially outwardly of the pin axis at axially spaced locations thereon to prevent substantial axial movement of the anchor pin in relation to the shoe when engaged by the recesses, said anchor pin being operatively located in a support structure of the assembly with the brake shoe pivoting on the pin under the action of the actuating mechanism.

According to a further aspect of the invention there is provided a vehicle brake assembly comprising a pair of brake shoes each having a pair of spaced webs defusing open ended laterally aligned recesses at one end portion of the respective shoe, actuating mechanism acting on the opposite end portions of the shoes, anchor means with which said recessed one end portions are engaged for pivotal movement of the shoes under the action of the actuating mechanism, and a support formation locating saidmechanism and said anchor means; the anchor means comprising at least one anchor pin having axially spaced cylindrical bearing areas dimensioned to radially, slidably receive said recesses and a pair of locating surfaces facing in axially opposite directions and extending radially outwards of the pin axis at axially spaced locations thereon to prevent substantial axial movement of the anchor pin in relation to the shoe or shoes whose recesses are engaged therewith, said pin being received in a bore of the support formation.

Preferred embodiments of the invention are now more particularly described with reference to the accompanying drawings, wherein: Figure 1 is a side elevation, partly in section, of a brake assembly; Figure 2 is a fragmentary view showing a modified form of brake assembly; Figure 3 is a bottom view of the embodimment of Figure 2; Figure 4 is a fragmentary view, partly in section, showing in detail one construction for pivotally mounting the brake shoes of Figure 1; Figure 5 is a perspective view showing the anchor pin of Figure 4; Figure 6 is a view similar to Figure 3 but showing a means of pivotally mounting the brake shoes of Figure 1 to a different type of support; and Figure 7 is a perspective view showing the anchor pin of Figure 6.

With reference to Figure 1 of the drawings, there is shown a cam actuated brake assembly of the kind described in our serial co-pending application 1 580 963 generally designated by the numeral 10. The brake assembly 10 is supported by a spider 11 rigid with a vehicle axle housing 12. The brake assembly 10 includes a pair of brake shoes 14 each of which is pivot ally mounted at one end to a respective anchor pin 60 carried by the spider 11. The anchor pins 60 are each carried in a cylindrical bore 16 provided through bosses 18. Anchor pins 60 and their method of location wiU be described in greater detail below with reference to Figures 4 and 5. The bosses 18 are formed as depending integral parts of the spider 11 and are axially offset from the upper portion of the spider 11.

The offset permits the bosses 18 to be located between the dual webs of the brake shoes 14.

A cam 19 is mounted for rotary 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 roller type cam follower 22. The cam is non-rotatably secured to a cam shaft 20 mounted to the spider for rotary movement in a bearing 21.

The cam shaft is rotated by means not shown to rock the cam 19 in a clockwise direction through an arc in the range of 100 to 300. The cam 19 provides an outwardly directed force to the rollers 22 and the brake shoes which causes the brake shoes to pivot about the anchor pins 60. This movement forces the friction lining pads 24 into contact with the inwardly facing friction surface 26 of a brake drum 25 secured by conventional means 23 to a wheel 27 rotatably mounted by hub 29 to a spindle at the outer end of axle housing 12. When the brakes are released the brake shoes 14 and the friction lining pads 24 are withdrawn from contact with the brake drum surface 26 by a return spring 28 secured at its opposite ends to the brake shoe webs.

The brake shoes 14 are dual web fabricated brake shoes. 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 circumferential direction. The brake shoe table 32 is curved in the circumferenctial direction and the webs 31 are welded in parallel relation along the interior curved portion of the table. This provides a genreally rigid assembly of component parts to which the friction lining pads 24 may be secured by rivets or by chemical bonding.

Each of the brake shoe webs 31 is provided with an open recess 34 shaped and disposed as described in our serial co-pending application no 1 580 963 to resist displacement of the shoe away from the anchor pin during operation of the brakes, while permitting dis-assembly of the shoe down the pin in an direction radial to the latter when the down is removed for maintenance. servicing, or replacement of the shoes when worn.

Although the recesses 34 may be of the same thickness as the brake shoe webs 31, it is preferred to provide a greater surface area for bearing against the anchor pin 60. The area of the arcuate bearing surface 35 may be increased by providing a shoulder 40 around the recess 34.

This may be accommodated by welding a Ushaped element to the surface of the web 31.

During assembly the anchor pins 60 are fitted to the bores 16 of the spider bosses 18.

The brake shoes 31 are mounted to the spider by sliding the recesses 34 in a generally radially direction over cylindrical ends of the anchor pins 60 extending from the opposite sides of the spider bosses 18. The webs 31 of each brake shoe may be through punched with laterally aligned holes 41.A pin 42 is inserted through the laterally alignedholes 41 of each brake shoe 14 and the opposite ends of a retention spring 44 are hooked around each respective pin 42.

The retention spring 44 helps spring 28 urge the arcuate bearing surfaces 35 provided at the recessed ends of the brake shoes 14 into contact with the anchor pins 60.

The remaining components of the brake assembly 10 as shown by Figure 1 and the brake drum 25 are added in conventional manner.

Figures 2 and 3 show a modification of of the above arrangement where a pair of brake shoes 51 having open ended recesses 52 are pivotally mounted to a single anchor pin here described 54 functioning in the same way as another pins 60 of Figure 1. In this embodi ment the brake shoe tables 55 are provided with friction lining material 56 and the recessed end of one of the webs 58 of each brake shoe is axially offset to seat on the pin 54 internally adjacent the recessed end of the web 59 of the other brake shoe.

Figures 4 and 5 show in detail an anchor pin 60 used for mounting the dual web brake shoe 14 to the support boss 18 shown in Figure 1.

Anchor pin 54 of Figures 2 and 3 has the same form. Figure 4 shows how each anchor pin 60 is inserted in a bushing 61 seated in the cylindri cal bore 16 of spider boss 18.

The anchor pin 60, as best shown by Figure 5 is an elongate member having a stepped cy lindrical surface comprised of a cylindrical bear ing surface 62 and 64 at each end and at cylind rical mounting surface 65 extending a substan tial axial distance between the bearing surfaces 62 and 64. The surfaces 62,64 are of the same diameter and are smaller than the mounting sur face 65. The surfaces 62, 64 are also separated from the mounting surface by a pair of oppo sitely facing radially extending surfaces 66 and 68.

The diameter and length of the mounting surface 65 provide a snug fit in the bushing 61 with the oppositely facing radial surfaces 66 and 68 flush with the external surfaces of the spider boss 18. The recessed ends 34 of the dual web brake shoe are radially slidably engaged or seated on the cylindrical bearing surfaces 62 and 64. As the return spring 28 and/or the retention spring is applied to the brake shoes, the cam follower ends of the brake shoes are biased toward the rotary cam and the open ended recesses are firmly seated on the bearing surfaces 62 and 64. The width D of the recesses 34 is not as large as the diameter of the mount ing surface 65. The portion of the brake shoe webs surrounding the recesses 34 thus serve as abutments which are contacted by the radially extending surfaces 66, 68 of the anchor pin and prevent substantial axial movement of the anchor pin 60 relative to the brake shoe webs 31 and thereby prevent the anchor pin 60 from being axially displaced from the bore 16.

Figures 6 and 7 show a further arrangement for mounting a dual web brake shoe with each web having an open ended recess to a brake assembly support. In Figure 6 the brake support or spider is formed to provide a pair of axially spaced depending bossed 71 and 72 with a cy lindrical bore 73, 74 or a pair of axially aligned cylindrical bores 73,74 extending through said bosses.

The anchor pin 70, as best shown by Figure 7, is an elongate member having a stepped cy lindrical surface comprised of a cylindrical mounting surface 76 and 77 at each end and a cylindrical bearing surface 78 extending a substantial axial distance between the mounting surfaces 76 and 77. The mounting surfaces 76, 77 are of the same diameter and are larger than the bearing surface 78. The bearing surface 78 is separated from the mounting surfaces 76, 77 by a pair of oppositely facing radially extending surfaces 79 and 80.

The diameter and length of the mounting surfaces 76 and 77 provide a snug fit in the bores 73, 74 of the axially spaced bosses 71, 72 with the radial surfaces 79 and 80 flush with the internal surfaces of the bosses 71, 72. The recessed ends 34 of a dual web brake shoe are radially, slidably engaged or seated on axially spaced bearing areas of the bearing surface 78.

The return and/or retaining springs are applied to bias the brake shoes toward the rotary cam and firmly seat the recesses 34 on the anchor pin 70. As in the embodiment of Figures 4 and 5, the width D of the recesses 34 is not as large as the diameter of the cylindrical mounting surfaces 76, 77 and the webs surrounding the recesses 34 serve as abutments contacted by the radially extending surfaces 79, 80 of the anchor pin. The brake shoe webs 31 and anchor pin surfaces 79, 80 thus interact to prevent substantial axial movement of the anchor pin 70 relative to the brake shoe webs and thereby prevent the anchor pin 70 from being axially displaced from the spaced bores 73, 74.

The anchor pins 54, 60 and 70 both comprise an elongate pin having stepped cylindrical bearing areas for receiving the open ended recesses of a dual web brake shoe and a pair of oppositely facing surfaces extending radially outward at axially spaced locations to prevent the anchor pin from substantial movement relative to the brake shoe webs and, more importantly, to prevent the anchor pin from being axially displaced from the brake support bore.

As such, the anchor pins do not require other means such as snap rings or pressure plates to secure the pins against accidental displacement from the brake support bore.

As used with the open ended dual web brake shoes described in conjunction with Figure 1, the smaller diameter bearing surfaces of the anchor pins 54, 60 and 70 enable provision of a stronger web portion to hook around the anchor pin. This is beneficial due to the high stresses encountered as the anchor pin holds the hooked end of the brake shoe web against displacement under dynamic braking conditions.

Increased web end strength is provided by the smaller diameter cylindrical bearing surfaces while the larger diameter cylindrical mounting surfaces of the anchor pins permit the open ended, dual web brake shoes to be used with brake support plates having large diameter anchor pin bores. The anchor pins of the pre sent invention may thus be used with the open ended, dual web brake shoes as replacement parts for brake assemblies already in service and as components for new brake assemblies without changing the tooling for manufacturing the brake support plates.

Claims (11)

WHAT WE CLAIM IS:

1. The combination of a brake shoe and an anchor pin for a vehicle brake assembly, said shoe having a pair of spaced webs defining open ended laterally aligned recesses at one end portion of the shoe remote from an opposite end portion on which an actuating mechanism of the assembly acts in use, and the anchor pin being an elongate body having axially spaced bylindrical bearing areas dimensioned to radially, slidably receive said recesses and a pair of locating surfaces facing in axially opposite directions and extending radially outwardly of the pin axis at axially spaced locations thereon to prevent substantial axial movement of the anchor pin in relation to the shoe when engaged by the recesses, said anchor pin being operatively located in a support structure of the assembly with the brake shoe pivoting on the pin under the action of the actuating mechanism.

2. The combination as defined by Claim 1 wherein said axially spaced cylindrical bearing areas consist of a cylindrical bearing surface at each end of said anchor pin each bounded at its axially inner end by a radially extending locating surface of said anchor pin.

3. The combination as defined by Claim 2 wherein the pin has a cylindrical mounting surface of greater diameter than said bearing surfaces extending a substantial axial distance between said radially extending locating surfaces, said mounting surface being received between the webs and being located in a bore of the support formation in use.

4. The combination as defined by Claim 1 wherein said axially spaced cylindrical bearing areas are respectibe parts of a cylindrical bearing surface intermediate the ends of said anchor pin, said bearing surface being bounded at each of its axially outer ends by a radially extending locating surface of said anchor pin.

5. The combination as defined by Claim 4 wherein the pin has a pair of cylindrical mounting surfaces at each end thereof of greater diameter than the cylindrical bearing surface and terminating at the radially extending locating surfaces, said mounting surfaces having the webs received between them and being located in bores of the support formation in use.

6. The combination of a breake shoe and anchor pin for a vehicle brake assembly substantially as hereinbefore described with reference to and as shown in Figures 1,4 and 5; Figures 2 and 3; or Figures 6 and 7 of the accompanying drawings.

7. A vehicle brake assembly comprising a pair of brake shoes each having a pair of spaced webs defining open ended laterally aligned recesses at one end portion of the respective shoe, actuating mechanism acting on the opposite end portions of the shoes, anchor means with which said recessed one end portions are engaged for pivotal movement of the shoes under the action of the actuating mechanism, and a support formation locating said mechanism and said anchor means; the anchor means comprising at least one anchor pin having axially spaced cylindrical bearing areas dimensioned to radially, slidably receive said recesses and a pair of locating surfaces facing in axially opposite directions and extending radially outwards of the pin axis at axially spaced locations thereon to prevent substantial axial movement of the anchor pin in relation to the shoe or shoes whose recesses are engaged therewith, said pin being received in a bore of the support formation.

8. An assembly as defined in Claim 7 wherein the anchor means comprises a single said anchor pin with the recesses of both brake shoes engaged with the cylindrical bearing areas thereof.

9. An assembly as defined in Claim 7 wherein the anchor means comprises a pair of said anchor pins each received in respective bores of the support formation and each having the recesses of a respective one of the brake shoes engeged with the cylindrical bearing areas thereof.

10. The brake assembly defined by Claim 7, 8 or 9 wherein the actuating mechanism includes a rotary cam actuator disposed between said opposite end portions of said brake shoes remote from the anchor means.

11. A brake assembly as hereinbefore described with reference to and as shown in Figures 1, 4 and 5; Figures 2 and 3; or Figures 6 and 7 of the accompanying drawings.