Power parking failsafe disc brake
First Claim
1. A power parking, failsafe disc brake for an automotive vehicle comprising, in combination:
- a rotatable disc having friction faces on opposite sides thereof, a pair of friction pads engaging respective friction faces, and a caliper housing operably connected to each of said friction pads for urging the same into braking engagement with said disc when the brake is actuated, said caliper housing having a pair of axially aligned cylinder bores provided therein;
a first piston slidably disposed within one of said cylinder bores and having an end portion bearing against the adjacent friction pad;
a second piston slidably disposed within the other cylinder bore;
clearance adjusting means having a screw thread connection to said second piston and a frictional clutch connection with said first piston, and including a spring acting to extend said adjusting means;
compression spring means bearing against one side of said second piston in the direction to apply the brakes;
means for introducing fluid pressure into said cylinders, said first piston being actuated by said fluid pressure to operate the brakes for normal service operation and said second piston being urged by fluid pressure in the direction to compress said spring means;
a solenoid-operated locking detent that seats in a cavity in said second piston, the solenoid having a coil that is continuously energized while the system is in normal operation, thereby holding the locking detent down into engagement with said second piston; and
said solenoid having its coil connected to a normally closed switch that is opened whenever a failure occurs in the normal service hydraulic brake system, whereby the solenoid is de-energized to release said second piston and allow said compression spring means to apply the brakes automatically responsive to failure of the service brakes.
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Accused Products
Abstract
A disc brake comprising a caliper housing having axially aligned first and second cylinder bores; a first piston slidable within the first bore and bearing against one of the friction pads; and a second piston slidable within the second bore and having an internally threaded tubular opening into which a clearance adjuster is screwed. The threads of the adjuster are power transmission threads with a helix angle of about 15 degrees, and there is end-wise clearance between the threads sufficient to allow the first piston to move between its retracted and brakes-applied positions. At the end of the adjuster is a head having a conical clutch facing that engages a corresponding conical seat in the bottom of the first piston, so as to exert a powerful rotational clutch action. A spring urges the adjuster toward the bottom of the first piston, and causes the adjuster to unscrew and extent itself whenever there is any clearance between the clutch facing and seat. The second piston has a plurality of belleville springs bearing against its back side, and when hydraulic pressure is admitted to the two cylinders, the first piston applies the brakes, and the second piston compresses the springs and is then locked in place by a solenoid-operated detent. The solenoid can be de-energized to allow disengagement of the detent and release of the second piston so that the compressed springs can urge the piston in the direction to apply the brakes. The solenoid may be actuated by means of a manually controlled switch, or by operation of a switch in the differential pressure valve due to a failure to one of the hydraulic pressure lines. A second solenoid may be provided to effect partial application of the brakes on a long, downhill grade.
40 Citations
7 Claims
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1. A power parking, failsafe disc brake for an automotive vehicle comprising, in combination:
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a rotatable disc having friction faces on opposite sides thereof, a pair of friction pads engaging respective friction faces, and a caliper housing operably connected to each of said friction pads for urging the same into braking engagement with said disc when the brake is actuated, said caliper housing having a pair of axially aligned cylinder bores provided therein; a first piston slidably disposed within one of said cylinder bores and having an end portion bearing against the adjacent friction pad; a second piston slidably disposed within the other cylinder bore; clearance adjusting means having a screw thread connection to said second piston and a frictional clutch connection with said first piston, and including a spring acting to extend said adjusting means; compression spring means bearing against one side of said second piston in the direction to apply the brakes; means for introducing fluid pressure into said cylinders, said first piston being actuated by said fluid pressure to operate the brakes for normal service operation and said second piston being urged by fluid pressure in the direction to compress said spring means; a solenoid-operated locking detent that seats in a cavity in said second piston, the solenoid having a coil that is continuously energized while the system is in normal operation, thereby holding the locking detent down into engagement with said second piston; and
said solenoid having its coil connected to a normally closed switch that is opened whenever a failure occurs in the normal service hydraulic brake system, whereby the solenoid is de-energized to release said second piston and allow said compression spring means to apply the brakes automatically responsive to failure of the service brakes. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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Specification