JPS6157501B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to improvements in vehicle brake mechanisms, and more particularly to brake shoes for vehicle brake assemblies.

The present invention is particularly directed to a brake assembly having a pair of brake pieces having adjacent ends pivotally connected to a support and a rotatable actuating cam disposed between the other ends of the brake pieces. Useful for brake assemblies. As the cam rotates, each brake shoe pivots outward about its pivot or anchoring pin into engagement with an inwardly facing friction surface of the brake drum. This type of brake assembly is used for heavy duty brakes using dual or single web brake shoes. The brake shoe can be manufactured by casting or other methods. The brake piece still carries a roller-type cam follower at its end adjacent the actuating cam. Opposite adjacent ends of the brake shoes can be pivotally connected to a single anchoring pin as described in U.S. Pat.
It can be pivotally mounted to one of a pair of spaced apart anchoring pins as described in US Pat. No. 3,114,437.

A dual brake shoe for a brake assembly with a pair of spaced apart anchoring pins has an axially aligned, laterally extending hole in each web at its end and is pivoted to said support. It is becoming possible to wear it. The brake shoe is assembled by aligning the web hole with the opposite side of the boss hole formed on the brake spider and inserting an axial pin into the spider hole and the coaxial brake shoe hole. It will be mounted. The pin, commonly referred to as an anchoring pin, is press-fitted into the boss and has a snap spring at its axially extending end;
The brake piece is configured to prevent movement of the brake piece in the axial direction with respect to the pin. This arrangement is such that the brake piece is prevented from axial movement relative to the support except for pivoting as required about the anchoring pin.

With such an arrangement, several problems arise when it becomes necessary to remove the brake shoe in order to replace it or replace the lining. Although the brake assembly is partially enclosed to protect the components from road dust and harsh weather conditions, these components are exposed to moisture and temperature changes and become subject to corrosion. The pin is often captured by a spider hole and/or a brake shoe. Therefore, if it is desired to disassemble the brake mechanism, this becomes difficult as the pin must be removed from its relatively tight fit in the spider hole. To remove the brake shoe in such a case, the anchoring pin is punched out of the assembly, which, depending on its hardness, may deform the spider or destroy the spider boss carrying the anchoring pin. reach. If the spider is severely damaged, the spider on the axle housing must be replaced, or the entire axle assembly must be replaced.

Such problems are less likely to occur in brake assemblies of the type in which the brake shoe is mounted for pivoting about a single anchor pin. In an assembly of the type described, each adjacent end of the brake leaf web is recessed to form an arcuate bearing surface (an arc of less than 180 degrees), which bearing surface is moved radially relative to the anchoring pin. This causes the pins to rest on opposite sides of the pin. By forming an open end recess in the end of the brake tab, the brake tab can be attached to or removed from the pin without moving the anchoring pin relative to the spider. Although this arrangement facilitates installation and removal, the brake piece is not securely attached to the anchoring pin and is automatically actuated.
That is, when the brake assembly is actuated, the cam causes the brake shoe to pivot about the anchoring pin, bringing the friction lining pad into contact with the brake drum, thereby damaging the brake drum and the wheels attached to the drum. prevent rotation. The frictional force between the brake drum and the lining attached to the brake shoe tends to draw the lining into tighter contact with the brake drum, thereby increasing the frictional force. The effect of this frictional force on the lining depends on the direction of rotation of the brake drum.

The frictional force between the drum and the lining attached to one of the brake shoes has the same direction as the force applied by the cam actuator and complements the brake actuation force. The frictional force between the drum and the lining attached to the other brake shoe has a direction opposite to the force exerted by the rotatable cam actuator. Frictional forces around the brake shoe tend to move the brake shoe away from the anchoring pin and toward the cam at the other end of the brake. However, since there is no clearance to move towards the other end of the brake shoe, the brake drum and brake shoe become strained and the recessed end of the brake shoe moves away from the anchoring pin. This automatic actuation of the brake shoe causes the lining on the brake shoe to wear out faster than necessary. This movement still generates undesirable noise.

The brake shoe according to the invention has at least one web, one end of which is formed with a recess for sliding engagement with a cylindrical pin mounted on a support on the axle of the vehicle. It's getting old. The recess has an arcuate bearing surface adapted to engage a complementary arcuate surface of said pin, a portion of said complementary arcuate surface being in contact with an end of said arcuate bearing surface and said brake lug. The open end of the brake tab is adapted to prevent it from moving away from the pin in response to circumferential forces that would tend to move the brake tab toward the other end of the web. The end of said arcuate bearing surface preferably comprises a hook portion of the brake leaf web, said hook portion being shaped to engage a portion of said complementary arcuate surface. In a preferred embodiment, the recessed end of the brake shoe web comprises an inner arcuate bearing surface and a mouth portion formed by an integral part of the brake shoe web at the opposite end of the arcuate bearing surface. It has a slot. The slot is positioned to engage one end of the arcuate bearing surface with the portion of the complementary arcuate surface when the brake is actuated.

Next, embodiments of the present invention will be described with reference to the accompanying drawings.

The cam actuated brake assembly is designated in its entirety by 10 in the figures. The brake assembly 10 is supported by a spider 11 which is integral with the axle housing 12 of the vehicle. Brake assembly 10 further includes a pair of brake shoes 14, each pivotally connected at one end to an anchoring pin 15 carried by spider 11. Each anchoring pin 15 is carried within a cylindrical hole 16 formed in a boss 18. 1st
Boss 18 as shown in FIGS.
are formed as integrally suspended parts on both left and right sides of the lower part of the spider 11, and
1. This bias allows the boss 18 to be located between the double webs of the brake shoe 14.

The cam 19 is rotatably mounted between the anchoring pin 15 and the adjacent end of the opposite brake piece 14.
Each brake piece 14 has a roller-type cam follower member 22 . This cam is fixed to a camshaft 20 mounted on a spider so that it can rotate within a bearing 21. The camshaft is rotated clockwise within a range of 10-30 degrees by a suitable device (not shown). This cam exerts an outward force on the roller 22 and the brake shoe 14, which pivots about the anchoring pin 15. This movement brings the friction backing pad 24 into contact with the inwardly facing friction surface 26 of the brake drum 25. The brake drum is mounted by conventional means to a wheel rotatably mounted on a spindle at the outer end of the axle housing 12. When the brake is released, the brake shoe 14 and friction backing pad 24 are pulled away from the brake drum surface 26 by a return spring 28. The return spring is attached at its opposite ends to the brake shoe web.

The brake shoe 14 is a brake shoe with a reversible web. That is, each brake shoe has a pair of axially spaced webs 31, which are mounted on a table 32. The web 31 is flat in the radial direction and curved in the longitudinal or circumferential direction. The brake shoe table 32 is circumferentially curved and the webs 31 are welded in parallel relationship along the inwardly curved portion of the table. This provides a rigid assembly of parts to which the friction backing pad 24 is attached by riveting or chemical bonding methods.

Each brake leaf web 31 has an open recess 34 at its end opposite the cam follower 22. This recess 34 is in the form of a slot, which slot has an inner arcuate bearing surface 35 and a mouth formed by integral brake lug parts 36, 38, said brake lug parts having an arcuate bearing surface. Extending tangentially outwardly from opposite ends of surface 35. The bearing surface 35 is a semicircular bearing surface, and the cylindrical end 1 of the anchoring pin 15
It is adapted to engage the complementary arcuate surface 17 of No. 3. The bearing surface 35 consists of an upper part 37 and a lower part 39. The recess 34 is cut out obliquely so that the upper part 37 and lower part 39 of the bearing surface 35 lie on either side of a radial plane passing through the center of the anchoring pin 15 and the axis of rotation of the wheel carried by the axle housing 12. In the complementary arcuate surface 17
arranged to engage with. The plane represented by line A in FIG.
and through the longitudinal center of the axle housing 12, which is coaxial with the axis of rotation of the brake drum 25 and the wheel on which the brake drum is mounted.

The outer end of the lower part 39 of the arcuate bearing surface 35 shown on the left in FIGS. It is disposed so as to come into contact with a portion of the surface 17. If the brake assembly is actuated while the wheel and brake drum 25 are rotating clockwise as represented by the arrows in FIG. A circumferential force is generated that moves both brake pieces 14 clockwise. Brake drum 25 and brake piece 1 shown on the right side of FIG.
The circumferential force exerted between the friction lining 24 and the friction lining 24 attached to the cam 4 moves the brake lug towards its anchoring pin, thus reducing the brake actuation force applied by the cam 19. Complement. The circumferential force acting between the brake drum 25 and the friction lining 24 attached to the brake shoe 14 shown on the left in FIG. Yes, if the brake shoe is not restrained,
The circumferential force moves the brake shoe clockwise away from the anchoring pin 15 toward the other end, ie, toward the cam follower end of the brake shoe. Brake piece 14
The beveled recess 34 prevents such movement. A portion of the complementary arcuate surface 17 of the pin 15 contacts the lower portion 39 of the inner arcuate bearing surface 35 on the right side of the plane represented by line A, causing the brake shoe to separate from the anchoring pin. to prevent

The width D of the mouth portion of the recess 34 and the diameter of the inner arcuate bearing surface 35 are such that the brake piece is
The anchoring pin 15 is selected to slidably engage the end of the anchoring pin 15 projecting from the anchoring pin 8 . This arrangement facilitates disassembly and assembly, and since the lower part 39 of the recess 34 is hooked around a part of the anchoring pin 15 on the side remote from the main bearing part, the brake lug can be easily disassembled and assembled. This will prevent it from operating automatically.

For ease of manufacture and assembly it is preferred to use a semi-circular inner arcuate bearing surface 35, with the bearing surface of the recess 34 having a diameter of 180 mm from end to end.
It is made to be smaller than the arc of degrees. Preferably, the recess 34 or notched end of the brake shoe 14 is cut at an angle of approximately 5-30 degrees with respect to the plane represented by line A in FIG. If the inner arcuate bearing surface is 180 degrees, then 5-30 degrees of the arcuate bearing surface 35 is defined as the lower portion on the right or far side of the plane represented by line A in FIG. 39.

The recess 34 can be of the same thickness as the brake leaf web 31, but preferably provides a large surface area for the bearing for the anchoring pin 15. The area of the arcuate bearing surface 35 can be increased by forming a shoulder 40 around the recess 34.

When assembling, it is desirable that the anchoring pin 15 is press-fitted into the hole 16 of the spider boss 18. Brake tabs 14 are mounted to the spider by sliding radially within recesses 34 over the cylindrical ends 13 of anchoring pins 15 extending from opposite sides of spider bosses 18. The web 31 of each brake shoe is drilled with laterally aligned holes 41. A pin 42 is inserted through a laterally aligned hole 41 in each brake lug 14 and the opposing end of a retaining spring 44 is hooked around each corresponding pin 42. This retaining spring 44 has a spring 28
The arcuate bearing surface 35 formed on the recessed end of the brake piece 14 springs into contact with the anchoring pin 15.

A pair of snap springs 45 seated in grooves 46 adjacent opposite ends of the anchoring pins 15 prevent axial movement of the brake leaf web 31 relative to each anchoring pin 15.

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

The brake shoe of the present invention thus facilitates assembly and disassembly due to the anchoring pin recess and its specific location relative to the spider-supported anchoring pin, and also because of the open-ended anchoring pin recess. This can prevent automatic activation as in conventional brake assemblies that use brake shoes that have a built-in position.

It is to be understood that various modifications may be made to the invention without departing from the scope of the claims.

[Brief explanation of the drawing]

FIG. 1 is a side view, partially in section, of a brake assembly according to the present invention. FIG. 2 is a partial cross-sectional view taken along line 2--2 of FIG. FIG. 3 is a cutaway view showing the brake shoe and brake spider portions of the brake assembly shown in FIG. 1; In the figure, 10 is a brake assembly, 11 is a spider, 12 is an axle housing, 13 is a cylindrical end, 14 is a brake piece, 15 is an anchoring pin, 16 is a cylindrical hole, 17 is an arcuate surface, 18 is a boss, 19 is a cam, 20 is a camshaft, 21 is a bearing, 22 is a cam driven member, 24 is a pad, 25 is a brake drum, 2
6 is a friction surface, 28 is a return spring, 31 is a web, 3
2 is a table, 34 is a recess, 35 is a bearing surface, 3
6 and 38 are brake piece parts, 37 is an upper part, 3
9 is a lower part, 41 is a hole, 42 is a pin, 44 is a retaining spring, 45 is a snap ring, and 46 is a groove.

Claims (1)

[Claims] 1 a brake drum, a pair of brake pieces having adjacent ends pivotally connected to a support, and a pair of brake pieces disposed between the other ends of the brake pieces and pivoted so as to bring the brake pieces into frictional contact with the brake drum; In a brake shoe of a brake assembly of the type including an actuating device thereby producing a circumferential force complementary to the force actuating one brake shoe and opposite to the force actuating the other brake shoe, A cylindrical bearing of an anchoring pin, said brake piece comprising at least one continuous rigid web having a recess with an open end at one end, said recess being mounted on a support on the axle of the vehicle. an inner arcuate surface having a width that engages the bearing surface of the pin, and an inner arcuate surface that is in bearing contact with the bearing surface of the pin; A brake piece of a brake assembly, characterized in that end portions of the arcuate surfaces disposed on both sides and far from the plane extend beyond the plane within an angular range of 30 degrees. .