GB2087493A - Brake spider with integral pivot posts - Google Patents

Abstract

A brake spider 12 for a brake assembly which is capable of being mounted on a heavy duty truck or trailer axle has integral pivot posts 50 to support dual web brake shoes 22. Each of the duel web brake shoes 22 has aligned open recesses 48 in adjacent ends 46 of the axially spaced webs 24 thereof. The brake spider 12 includes a central portion 14 having a hole 16 extending therethrough for receipt of the axle or spindle 18. A first end 38 of spider 12 supports a cam shaft 34 of a cam actuation means 30 and a second end 46 is axially offset from the first end 38 and includes two circumferentially spaced pairs of integrally formed pivot posts 50 each of which pair is associated with one of the dual web brake shoes. The posts 50 may be cast, may have wear resistant sleeves installed thereover, may be cylindrical or provided with a flat potion. <IMAGE>

Description

SPECIFICATION Brake spider with integral pivot posts Background of the Invention Field of the Invention This invention relates to a brake spider and, more specifically, to such a brake spider which includes integrally formed pivot posts for support of a pair of dual web brake shoes of a brake assembly.

Description of the PriorArt It is not uncommon in the heavy duty truck and trailer field to utilize drum brakes which employ a rotary cam actuation means. Typically, such brakes include a pair of brake shoes having adjacent ends pivotally mounted to a brake spider which is secured to the axle spindle and a rotatable actuating cam carried at the other end of the spider disposed between the other ends of the brake shoes. Rotary movement of the cam causes each of the brake shoes to move outwardly about its pivot or anchor pin to contact the inwardly facing friction surface of the drum brake.

For such heavy duty brake installations, it is common for the brake shoes to be of the dual web type. At one time, most dual web brake shoes included axially aligned, laterally extending bores through each of the webs at the end of the shoe to be pivotally mounted on the pair of anchor pins.

The brake shoes were mounted to the brake spider by aligning the web bores on opposite sides of a bore through a boss formed in the brake spider and inserting the anchor pin axially through the spider bore and coaxial brake shoes bores. The anchor pin might have been press fit to the boss or locked against rotation by a set screw or other means. Snap rings could be provided to the axially extending ends of the pin to prevent substantial axial displacement of the anchor pin relative to the brake spider. U.S. Patents 3,136,390; 3,314,507; 3,339,677 and 3,650,360 demonstrate brake assemblies of this type which utilize different means for securing the anchor pin in the brake spider.

Recent innovations in the brake shoe design for these heavy duty drum brakes have resulted in the dual web brake shoes being provided recesses at the end of each web which would eliminate some of the assembly problems required of the prior art designs mentioned hereinabove. U.S. Patents 4,157,747 and 4,206,834 demonstrate such brake assemblies. Although the inclusion of a recess at the ends of the web has simplified assembly, these brake assemblies have nevertheless continued to employ an anchor pin which is installed in a bore of the brake spider and requires additional means for its retention therein.

Although anchor pins have been installed in brake spiders in this manner for many years and have provided reliable support for dual web brake shoes, such installations are not without problems and include a number of assembly steps and assembly parts which might add to the overall expense of the brake assembly. In such heavy duty installations, the amount of force applied to the anchor pins requires that the joining of the pins to the brake spider be reliable and free of any relative movement therebetween. Undesired relative movement or rotation of the anchor pins could result in permanent damage to the brake spider requiring its replacement or repair. U.S. Patent 3,131,583 is directed to this problem in which the brake spider must be rebored to receive a new, larger anchor pin.

Although the security and integrity of the anchor pin remains a problem in the support of dual web brake shoes, there have been some efforts in the single web brake shoes to provide such secure and reliable support. U.S. Patents 2,372,322; 2,544,030 and 2,942,696 demonstrate such assemblies for single web brake shoes. However, no effort has heretofore been made to provide a heavy duty brake assembly with such rigid and reliable anchor pin configurations for the support of dual web brake shoes which are commonly required in such installations.

Summary of the Invention It is, therefore, an object of this invention to provide a brake spider including integral pivot posts for pivotally supporting dual web brake shoes found in brake installations utilized in heavy duty trucks and trailers.

It is another object to provide such a brake spider which is less expensive to provide and easier to assemble than the prior art brake spiders utilizing separate installed anchor pin configuration.

These and other objects of the invention are provided in a preferred embodiment thereof including a brake spider for a brake assembly which is capable of being mounted on a heavy duty truck or trailer axle for the support of a pair of dual web brake shoes and actuation means therefor. Each of the dual web brake shoes has aligned open recesses in adjacent ends of the axially spaced webs thereof. The brake spider includes a central portion having a hole extending therethrough for receipt of the axle to which the central portion is secured. The first end of the brake spider is capable of supporting the actuation means. The second end is axially offset from the first end and includes two circumferentially spaced pairs of integrally formed pivot posts, each of the pair being associated with one of the dual web brake shoes.The pivot posts of each pair are axially aligned and extend axially at opposite sides of the second end to be capable of receiving the open recesses thereabout for pivotally supporting the dual web brake shoe thereon.

Brief Description of the Drawings Figure 1 is a sectional, elevational view of a brake assembly including various features of the invention.

Figure 2 is a view as seen along 2-2 of Figure 1.

Figure 3 is a fragmentary view of an alternative embodiment of the invention.

Figure 4 is a view as seen along 4-4 of Figure 3.

Figure 5 is a fragmentary view of still another alternative of the embodiment of the inventions.

Detailed Description of the invention As seen in Figures 1 and 2, a drum brake assembly 10 includes a preferred brake spider 12 and is typical of the type of brake found in heavy duty trucks and trailer. The spider 1 2 includes a central portion 14 having an opening 16 therethrough and being mounted on an axle or spindle 18. The spindle 18 extends through the opening 1 6 as the central portion 14 is, in the preferred embodiment, welded to the spindle 18.

It is equally effective in some installations for the central portion 14 4 to be bolted to a flange provided on the spindle 18. A brake drum 20 is mounted to a wheel (not shown) which is rotatably mounted on the axle spindle 1 8 in a manner well known in the art.

The brake assembly 10 for such heavy'duty applications commonly utilizes a pair of brake shoes 22 which are dual web fabricated brake shoes, i.e., each brake shoe 22 includes a pair of axially spaced webs 24 secured to a table 26. The webs 24 are flat in a radial direction and curved in a longitudinal or circumferential direction. The brake shoe table 26 is curved in the circumferential direction and the webs 24 are welded in parallel relationship along the interior curved portion of the table 26. This provides a generally rigid assembly of component parts to which the friction lining pad 28 may be secured by rivets or by chemical bonding.

To selectively move the brake shoes 22 outwardly to produce frictional engagement with the interior of the brake drum 20, an actuation means 30 is provided. In the brake assembly 10, the actuation means 30 is in the form of rotary cam actuator which includes a cam 32 which is rigidly secured to a cam shaft 34. The cam shaft 34 can be rotated by means (not shown) which are well known in the brake art to cause the cam 32 to rotate outwardly displacing the brake shoes 22 for braking engagement with the interior of the drum 20. The brake shoes 22 in the preferred embodiment include rollers or cam followers 36 at the end 37 thereof adjacent the cam 32 to allow smooth application of the force generated by rotation of the cam 32 to each of the brake shoes 22.A first end 38 of the preferred spider 12 includes an opening 40 therethrough for support of the cam shaft 34 as the cam 32 extends from one end thereof in alignment with the brake shoes 22. The opening 40 may be provided any form of bushing or bearing (not shown) well known in the art to allow free rotation of the cam shaft 34 therein.

The other end 42 of the preferred spider 12 is axially offset from the first end 38 to be aligned with a region between the webs 24 of the brake shoes 22. Specifically, the end 42 of the spider 1 2 has a lower region thereof which includes two bosses 44 having outwardly facing surfaces which are a predetermined distance apart to be spaced between the parallel webs 24 of each brake shoe 22. In this manner, the bosses 44 properly receive the webs 24 on each side thereof to prevent undesired axial movement of the brake shoes 22 during and after assembly.

An end 46 of the brake shoe 22 is designed to be supported for pivotal movement in response to the outward movement of the end 37 of the brake shoe 22 as it is selectively moved by the cam 32.

The end 46 is provided aligned open recesses 48 in the adjacent ends 46 of each web 24. The end 42 of the brake spider 12 includes two circumferentially spaced pairs of integrally formed pivot posts 50 with each of the pair being associated with one of the dual web brake shoes 22. The pivot posts 50 of each pair are axially aligned and extend axially from the bosses 44 at opposite sides of the end 42 of the spider 12 to be capable of receiving the open recesses 48 thereabout for pivotally supporting the dual web brake shoes 22 thereon. The posts 50 being integrally formed in this manner eliminate a number of the parts required in brake spider designs mentioned hereinabove and the concern which heretofore existed regarding a lack of rigidity in the mounting of separate anchor pins in a spider.

In the preferred embodiment, it is expected that the posts 50 may be cast or otherwise formed of the same ductile material which is presently accepted for the manufacture of heavy duty spiders of the type described. However, an alternative design can be employed while still being within the scope of the invention if it is felt that further insurance is needed against undesirable wear in the region of the pivot posts.

As seen in Figures 3 and 4, a spider 52 is provided integral posts 54 in the same manner as generally described hereinabove but a sleeve 56 of steel or other wear resistant material has been installed over each of the posts 54 to receive the recess 48 thereabout. The sleeve 56 may be press fit on each post 54 and/or staked in position to insure against its accidental removal. Using a sleeve 56 in this manner will provide a serviceable element which can be removed and replaced during normal maintenance without interfering with the integrity of the basic post 54.

As seen in Figure 5, still another embodiment of the invention includes a brake spider 62 in which the posts 64 integrally formed therewith are not provided a circular cross section. Although the pivot posts 64 have a significant portion of their outer surface which is cylindrical, the main body is provided a flat portion as if a chordal section thereof had been removed. As a result, each of the brake shoe webs 66 can be provided an open recess 68 which extends greater than 1 80C about the exterior surface of the post 64. A brake shoe having this type of web can be installed about the posts 64 in one angular orientation and can then be rotated to the final assembly position. When properly positioned for brake operation, the recesses 68 will extend sufficiently around the posts 64 to be retained thereon during operation of the brake until the shoes are reoriented for their removal.

It should be clear to those skilled in the brake art that other types of brake spiders can be provided with integral pivot posts for support of dual web brake shoes and that any number of alterations may be made to the embodiments as described hereinabove without departing from the scope of the invention as claimed.

Claims (5)

1. A brake spider for a brake assembly which is capable of being mounted on a heavy duty truck or trailer axle for support of a pair of dual web brake shoes and actuation means therefor, each of said dual web brake shoes having aligned open recesses in adjacent ends of the axially spaced webs thereof, said brake spider comprising: a center portion including a hole extending therethrough and being secured to said axle which extends through said hole therein; a first end capable of supporting said actuation means; a second end axially offset from said first end and including two circumferentially spaced pairs of integrally formed pivot posts, each of said pair being associated with one of said dual web brake shoes; and said pivot posts of said each pair being axially aligned and extending axially at opposite sides of said second end to be capable of receiving said open recesses thereabout for pivotally supporting said dual web brake shoe thereon.

2. The brake spider as set forth in claim 1, wherein each of said pivot posts is cylindrical in shape.

3. The brake spider as set forth in claim 1, further including a sleeve means surrounding said pivot posts to provide a bearing surface thereon.

4. A brake spider substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

5. A brake assembly including a brake spider as in any one preceding claim.