Brakes – Wheel – Axially movable brake element or housing therefor
Reexamination Certificate
2002-06-26
2004-04-13
Butler, Douglas C. (Department: 3683)
Brakes
Wheel
Axially movable brake element or housing therefor
C188S072300, C188S072300, C188S20500R
Reexamination Certificate
active
06719105
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates in general to vehicle disc brake assemblies and in particular to an improved structure for a brake shoe retraction mechanism adapted for use in such a vehicle disc brake assembly.
Most vehicles are equipped with a brake system for retarding or stopping movement of the vehicle in a controlled manner. A typical brake system for an automobile or light truck includes a disc brake assembly for each of the front wheels and either a drum brake assembly or a disc brake assembly for each of the rear wheels. The brake assemblies are typically actuated by hydraulic or pneumatic pressure generated when an operator of the vehicle depresses a brake pedal. The structures of these drum brake assemblies and disc brake assemblies, as well as the actuators therefor are well known in the art.
A typical disc brake assembly is shown in prior art FIG.
18
and includes an anchor bracket
100
which is secured to a fixed, non-rotatable component of the vehicle. A pair of brake shoes
102
and
104
are supported on the anchor bracket for sliding movement relative thereto. The brake shoes have respective friction pads
102
A and
104
A which are disposed on opposite sides of a brake rotor
106
. The rotor, in turn, is connected to the wheel of the vehicle for rotation therewith. To effect braking action, the brake shoes are moved inwardly toward one another so as to frictionally engage the opposed sides of the brake rotor. Such frictional engagement causes retarding or stopping of the rotational movement of the brake rotor and, therefore, the wheel of the vehicle in a controlled manner.
To accomplish this, the disc brake assembly further includes a caliper assembly, indicated generally at
108
, for selectively moving the brake shoes into frictional engagement with the brake rotor. The caliper assembly typically includes guide pins or other components to slidably support a caliper housing
110
relative to the fixed anchor bracket. The caliper housing is generally C-shaped, having an inboard leg
110
A disposed adjacent the inboard brake shoe and an outboard leg
110
B disposed adjacent the outboard brake shoe. One or more hydraulically or pneumatically actuated brake pistons
112
are provided in respective cylindrical recesses
114
formed in the inboard leg of the caliper adjacent to the inboard brake shoe. When the brake pedal is depressed, the piston and the inboard leg of the caliper are urged apart from one another. Specifically, the piston is urged outwardly, while the outboard leg of the caliper is urged inwardly. As mentioned above, the piston is disposed adjacent to the inboard brake shoe and, therefore, urges it outwardly toward the inner side of the rotor. Because the caliper is slidably mounted on the pins of the anchor bracket, the outboard leg of the caliper (and, thus, the outboard brake shoe disposed adjacent thereto) are urged inwardly toward the outer side of the rotor. As result, the brake shoes frictionally engage the opposed sides of the rotor.
Frequently, an annular roll-back seal
116
is provided within the cylindrical recess in contact with the outer surface of the piston. The roll-back seal is conventional in the art and performs several functions. First, the roll-back seal provides a seal to define the extent of the cylindrical recess within which the piston is disposed. Second, the roll-back seal is designed to retract the piston inwardly away from the rotor by a predetermined distance from the fully engaged position when the brake pedal is released after being depressed. To accomplish this, the roll-back seal frictionally engages the outer surface of the piston, resiliently resisting movement thereof when the brake pedal is depressed. Thus, when the brake pedal is released by the operator of the vehicle, the resilience of the roll-back seal causes the piston to retract within the cylindrical recess and out of contact with the inboard brake shoe.
With repeated usage, the friction pads of the brake shoes wear and become increasingly thinner. When this occurs, the piston and the caliper must move greater distances relative to one another to effect the same braking action as when the friction pads were new. Despite this increased distance of movement of the piston in the outboard direction, it is desirable that the roll-back seal retract the piston only by the same predetermined distance away from the rotor in the inboard direction. Thus, known roll-back seals are designed to accommodate increased movement of the piston in the outboard direction when the brake pedal is depressed, but to retract the piston inwardly by approximately the same predetermined distance when the brake pedal is subsequently released.
Ideally, when the brake pedal is released, the brake shoes should also be spread apart from one another to prevent any incidental frictional engagement with the rotor. To accomplish this, it is known to provide the disc brake assembly with one or more retraction springs for moving the brake shoes apart from one another to prevent frictional engagement with the rotor when the brake pedal is released. For example, U.S. Pat. Nos. 4,364,455 to Oshima, 4,491,204 to Dirauf et al., U.S. Pat. No. 4,629,037 to Madzgalla et al., U.S. Pat. No. 4,658,938 to Thiel et al, U.S. Pat. No. 4,867,280 to Von Gruenberg et al., U.S. Pat. No. 4,940,119 to Kondo et al., U.S. Pat. No. 5,069,313 to Kato et al., U.S. Pat. No. 5,249,647 to Kobayashi et al., U.S. Pat. No. 5,251,727 to Loeffler et al., and U.S. Pat. No. 6,378,665 to McCormick et al. all disclose disc brake assemblies which include a retraction spring structure. It is desirable that such retraction springs exert an amount of force which is large enough to urge the brake shoes apart from one another to prevent engagement with the rotor, but small enough not to overcome the roll-back seal to move the piston deeper within the associated cylindrical recess formed in the inboard leg of the caliper.
SUMMARY OF THE INVENTION
This invention relates to an improved pad retraction spring adapted for use in a disc brake assembly. The disc brake assembly includes an anchor bracket adapted to be secured to a vehicle component, a brake caliper adapted to be secured to the anchor bracket, a pair of brake shoes carried by the disc brake assembly and adapted to be disposed on opposite axial sides of an associated brake rotor, and actuation means for selectively moving the brake shoes into frictional engagement with the rotor. The anchor bracket includes a pair of outwardly extending arms and at least one of the arms has an opening formed therethrough. The pad retraction spring is carried by the disc brake assembly and is operative to move the brake shoes from engagement with the rotor when the brake shoes are in a non-braking position. The pad retraction spring includes a central mounting portion and a pair of outermost spring arms. The central mounting portion extends through the opening of the arm and engages a portion of the anchor bracket to thereby secure and locate the pad retraction spring on the anchor bracket in a predetermined position. The outermost spring arms of the pad retraction spring engage a portion of the pair of brake shoes.
REFERENCES:
patent: 5251727 (1993-10-01), Loeffler et al.
patent: 5549181 (1996-08-01), Evans
patent: 6378665 (2002-04-01), McCormick et al.
Butler Douglas C.
Kelsey-Hayes Company
MacMillan, Sobanki & Todd, LLC
LandOfFree
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