Disc brake

• US 4,454,933 A
• Filed: 04/27/1981
• Issued: 06/19/1984
• Est. Priority Date: 04/27/1981
• Status: Expired due to Fees

• Current Assignee: Kelsey-Hayes Co. (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Original Assignee: Kelsey Hayes Company
• Inventors: Buckley, James A., Hunnicutt, Harry A.
• Primary Examiner(s): HALVOSA, GEORGE
• Application Number:
  US06/258,067
• Time in Patent Office: 1,149 Days
• Field of Search: 188/71.8, 188/71.9, 188/72.7, 188/196 D, 188/106 F, 192/111 A
• US Class Current: 188/71.9
• CPC Class Codes: F16D 2125/36 Helical cams, Ball-rotating ramps
• CPC Class Codes: F16D 55/224 with a common actuating member for the braking members
• CPC Class Codes: F16D 65/567 for mounting on a disc brake

Abstract

A disc brake having an improved automatic adjustment mechanism is disclosed. The preferred brake includes a rotary actuating assembly for axially translating a push rod which abuttingly urges a pair of friction element assemblies into engagement with a rotatable disc. A nonrotatable element of the actuating assembly threadably engages the push rod, such that when the push rod is rotated, it is axially advanced to decrease the friction element clearance. A clutch mechanism circumscribes the push rod and communicates, by way of a lost motion connection, with a rotatable element of the actuating assembly to effect rotation of the push rod after a predetermined rotation of the rotatable element. Thus, clearance adjustments are made in response to predetermined wear of the friction elements, thereby maintaining brake clearance within predetermined limits.

Claims

1. A mechanically-actuated disc brake, including a rotor, rotatable about an axis, having a pair of friction surfaces, one on each side thereof, friction element means in juxtaposed relation with each of said rotor friction surfaces, a housing having a bore extending axially therethrough, brake-applying means within said bore for urging said friction element means into engagement with said rotor friction surfaces, said brake-applying means including a cam assembly in juxtaposed relation with said bore, said cam assembly including a rotatable and a nonrotatable cam member defining a gap therebetween, a push rod communicating with said friction element means, said push rod having a threaded portion thereof coaxially positioned within, and circumscribed by, said cam assembly, said nonrotatable cam member threadably engaging said threaded portion of said push rod, whereby upon normal brake actuating rotation of said rotatable cam member, the combination of said nonrotatable cam member and said push rod axially translates in a forward brake-applying direction urging said push rod into direct engagement with said friction element means thereby effecting frictional engagement of said friction element means with said rotor friction surface, means for biasing the combination of said nonrotatable cam member and said push rod in a rearward brake-releasing direction upon counter rotation of said rotatable cam member, adjusting means for rotating said push rod relative to said nonrotatable cam member, thereby forwardly advancing said push rod with respect to said nonrotatable cam member, said adjusting means including clutch means for rotating said push rod with respect to said nonrotatable cam member in response to rotation of said rotatable cam member, said clutch means including a one-way spring clutch frictionally circumscribing said push rod and including at least one external tang projecting radially outward and engaging an axially-extending slot in said rotatable cam member, the circumferential width of said axially-extending slot in said rotatable cam member being greater than the circumferential width of said external tang whereby said one-way spring clutch slips and rotates with respect to said push rod after a predetermined rotation of said rotatable cam member in a first rotary direction and drivingly rotates said push rod relative to said nonrotatable cam member in response to counter-rotation of said rotatable cam member in a second rotary direction, thereby indexing said push rod in said forward axial direction to maintain the clearance between said friction elements and said rotor, a one-way spring brake having a portion extending into said gap circumscribingly and threadingly engaging a threaded portion of said push rod extending into said gap, whereby said one-way spring brake frictionally engages threads in said gap, one end of said one-way spring brake being rotationally fixed to said nonrotatable cam member, thereby allowing said push rod to rotate in said second rotary direction so as to forwardly index said push rod and frictionally resisting rotation of said push rod in said first rotary direction.

2. The mechanically-actuated disc brake according to claim 1, further comprising an annular bushing juxtaposed within said rotatable cam member and circumscribing said push rod, whereby said push rod is maintained in coaxial alignment within said rotatable cam member.

3. The mechanically-actuated disc brake according to claim 2, wherein said rotatable cam member includes a rearwardly-protruding shaft having a hollow axial passageway therethrough and wherein said adjusting means includes means for manually rotating said push rod with respect to said nonrotatable cam member, whereby said push rod is selectively advanced in said forward direction, or retracted in said rearward direction, relative to said nonrotatable cam member, said manual means including torque-transmitting means on an end of said push rod, whereby a torque tool may be inserted through said axial passageway in said shaft to engage said torque-transmitting means and rotate said push rod with respect to said nonrotatable cam member, thereby selectively advancing or retracting said push rod.