Push rod slack adjuster

• US 4,399,894 A
• Filed: 08/18/1981
• Issued: 08/23/1983
• Est. Priority Date: 02/14/1979
• Status: Expired due to Term

• Current Assignee: Truck Components Incorporated (Accuride Corporation)
• Original Assignee: Kelsey-Hayes Co. (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Inventors: Tribe, Leonard T.
• Primary Examiner(s): Butler, Douglas C.
• Assistant Examiner(s): Diefendorf, R. R.
• Application Number:
  US06/293,781
• Time in Patent Office: 735 Days
• Field of Search: 188/71.9, 188/72.8, 188/196 D, 188/196 BA, 192/111 A
• US Class Current: 188/71.9
• CPC Class Codes: F16D 2055/007 Pins holding the braking members
• 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 slack adjuster for axially moved push rods is provided. An axially extending rotating actuating shaft turns a helical, driving cam member that in turn axially displaces a non-rotating driven cam member. The driving and driven helical cam members are located in a housing with the actuating shaft extending out of one end thereof and a threaded push rod extending out of the other end of the housing. A helical return spring is positioned between the driven cam and the inner wall of the housing to bias the cam members together. The push rod is held against rotation internally of the housing by a flange whose periphery is frictionally engaged by the return spring. A nut is threaded onto the rod and engaged by the driven cam member to transmit axial force to the push rod; and relative extension of the push rod from the cam members is accomplished by a one way spring brake acting on the nut and a disc clutch drive between the driving cam and nut. Lost motion is provided to prevent rotation of the nut on the rod during normal push rod clearance, and rotation of the nut on the push rod occurs when excessive push rod clearance occurs.

Claims

1. In a mechanically-actuated disc brake, including a rotor, rotatable about an axis, having a friction surface thereon, friction element means for frictionally engaging said rotor friction surface, a drive assembly including a rotatable helical cam member and an actuating member coaxially positioned within, and rotationally interlocked with, said rotatable cam member, an annular nonrotatable cam member in communication with said drive assembly, whereby upon rotation of said drive assembly, said nonrotatable cam member axially translates in a forward brake-applying direction, a push rod communicating with said friction element means, said push rod coaxially positioned within, and circumscribed by, said rotatable and nonrotatable cam members, an annular nut circumscribing and threadably engaging said push rod, said annular nut having a shank portion, coaxially positioned within said rotatable and nonrotatable cam members, and a radially-projecting flange communicating with said nonrotatable cam member, whereby said nonrotatable cam member urges the combination of said annular nut and push rod in said forward brake-applying direction in response to rotation of said drive assembly, thereby urging said friction element means into engagement with said rotor friction surface, means for biasing the combination of said annular nut and push rod in a rearward brake-releasing direction upon counter-rotation of said drive assembly, the improvement comprising adjusting means for rotating the annular nut relative to said push rod, thereby forwardly advancing said push rod with respect to said annular nut, said adjusting means including plate clutch means circumscribing, and projecting radially from, said annular nut and driven by said drive assembly, lost motion means, whereby said push rod is forwardly advanced with respect to said annular nut after a predetermined rotation of said drive assembly, and one-way brake means for frictionally resisting rearward retraction of said push rod with respect to said annular nut.

2. The improvement according to claim 1, wherein said plate clutch means comprises an annular inner clutch plate frictionally engaged on each side thereof by an annular outer clutch plate, said inner and outer clutch plates radially extending between said annular nut and said actuating member, means for maintaining said outer clutch plates in frictional engagement with said inner clutch plate, and wherein said lost motion means comprises at least one external tang projecting radially outward from each of said outer clutch plates and engaging an axial slot in said actuating member, and at least one internal tang projecting radially inward from said inner clutch plate and engaging an axial slot in said annular nut, the circumferential width of said axial slot in said annular nut being greater than the circumferential width of said internal tang, whereby said annular nut is rotated with respect to said push rod after a predetermined rotation of said drive assembly.

3. The improvement according to claim 1, wherein said plate clutch means comprises an annular inner clutch plate frictionally engaged on each side thereof by an annular outer clutch plate, said inner and outer clutch plates radially extending between said annular nut and said actuating member, means for maintaining said outer clutch plates in frictional engagement with said inner clutch plate, and wherein said lost motion means comprises at least one internal tang projecting radially inward from each of said outer clutch plates and engaging an axial slot in said annular nut, and at least one external tang projecting radially outward from said inner clutch plate and engaging an axial slot in said actuating member, the circumferential width of said axial slot in said actuating member being greater than the circumferential width of said external tang, whereby said annular nut is rotated with respect to said push rod after a predetermined rotation of said drive assembly.

4. The improvement according to claim 1, wherein said plate clutch means comprises an annular inner clutch plate frictionally engaged on each side thereof by an annular outer clutch plate, said inner and outer clutch plates radially extending between said annular nut and said rotatable cam member, means for maintaining said outer clutch plates in frictional engagement with said inner clutch plate, and wherein said lost motion means comprises at least one internal tang projecting radially inward from each of said outer clutch plates and engaging an axial slot in said nut, and at least one external tang projecting radially outward from said inner clutch plate, said external tang engaging an axial slot in said rotatable cam member, the circumferential width of said axial slot in said rotatable cam member being greater than the circumferential width of said external tang, whereby said annular nut is rotated with respect to said push rod after a predetermined rotation of said drive assembly.

5. The improvement according to claim 1, wherein said plate clutch means comprises an annular inner clutch plate frictionally engaged on each side thereof by an annular outer clutch plate, said inner and outer clutch plates radially extending between said annular nut and said actuating member, at least one external tang projecting radially outward from each of said outer clutch plates and engaging an axial slot in said actuating member, at least one internal tang projecting radially inward from said inner clutch plate and engaging an axial slot in said annular nut, means for maintaining said outer clutch plates in frictional engagement with said inner clutch plate, and wherein said one-way brake means comprises a helical spring brake circumscribing at least part of the shank portion of said annular nut, and wherein said lost motion comprises a radial projection on one end of said helical spring brake, said projection engaging an axial slot in said nonrotatable cam member, the circumferential width of said axial slot in said nonrotatable cam member being greater than the circumferential width of said projection, whereby said push rod is forwardly advanced with respect to said annular nut after a predetermined rotation of said drive assembly.

6. In 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 caliper having a pair of legs straddling said friction element means, one of said legs 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 helical cam assembly in juxtaposed relation with said bore, said helical cam assembly including a rotatable and a nonrotatable cam member, whereby upon rotation of said rotatable cam member, said nonrotatable cam member axially translates in a forward brake-applying direction, a push rod, communicating with said friction element means, having a portion thereof coaxially positioned within, and circumscribed by, said helical cam assembly, an annular nut circumscribing and threadably engaging said push rod, said annular nut having a shank portion, coaxially positioned within said helical cam assembly, and a radially-projecting flange communicating with said nonrotatable cam member, whereby said nonrotatable cam member urges the combination of said annular nut and push rod in said forward brake-applying direction in response to rotation of said rotatable cam member, thereby effecting frictional engagement of said friction element means with said rotor friction surface, means for biasing the combination of said annular nut and push rod in a rearward brake-releasing direction upon counter-rotation of said rotatable cam member, the improvement comprising adjusting means for rotating said annular nut relative to said push rod, thereby forwardly advancing said push rod with respect to said annular nut, said adjusting means including a cylindrical brake actuating member coaxially positioned within said helical cam assembly, circumscribing said annular nut, and rotationally interlocked with said rotatable cam member whereby rotation of said actuating member effects rotation of said rotatable cam member, plate clutch drive means transversely positioned between said cylindrical actuating member and said annular nut, said clutch drive means including lost motion means, whereby said push rod is forwardly advanced with respect to said annular nut in response to a predetermined rotation of said cylindrical actuating member.

7. 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 caliper having a pair of legs straddling said friction element means, one of said legs 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 helical cam assembly in juxtaposed relation with said bore, said helical cam assembly including a rotatable and a nonrotatable cam member, whereby upon rotation of said rotatable cam member, said nonrotatable cam member axially translates in a forward brake-applying direction, a push rod communicating with said friction element means, having a portion thereof coaxially positioned within, and circumscribed by, said helical cam assembly, an annular nut circumscribing and threadably engaging said push rod, said annular nut having a shank portion, coaxially positioned within said helical cam assembly, and a radially-projecting flange communicating with said nonrotatable cam member, whereby said nonrotatable cam member urges the combination of said annular nut and push rod in said forward brake-applying direction in response to rotation of said rotatable cam member, thereby effecting frictional engagement of said friction element means with said rotor friction surface, means for biasing the combination of said annular nut and push rod in a rearward brake-releasing direction, upon counter-rotation of said rotatable cam member, adjusting means for rotating said annular nut relative to said push rod thereby forwardly advancing said push rod with respect to said nut, said adjusting means including a cylindrical brake actuating member coaxially positioned within said helical cam assembly and circumscribing said annular nut, and rotationally interlocked with said rotatable cam member whereby rotation of said actuating member effects rotation of said rotatable cam member, plate clutch means for rotating said annular nut with respect to said push rod in response to rotation of said cylindrical actuating member, said plate clutch means including an annular inner clutch plate frictionally engaged on each side thereof by an annular outer clutch plate, said inner and outer clutch plates circumscribing said annular nut, each of said outer clutch plates including at least one external tang projecting radially outward and engaging an axial slot in said cylindrical actuating member, said inner clutch plate including at least one internal tang projecting radially inward and engaging an axial slot in said annular nut, the circumferential width of said axial slot in said annular nut being greater than the circumferential width of said internal tang whereby said annular nut is rotated with respect to said push rod after a predetermined rotation of said cylindrical actuating member, clutch biasing means for maintaining said outer clutch plates in frictional engagement with said inner clutch plate, a one-way spring brake helically circumscribing said shank portion of said nut and in frictional engagement therewith, one end of said one-way spring brake being rotationally fixed to said nonrotatable cam member, thereby allowing said annular nut to rotate so as to forwardly advance said push rod and frictionally resisting counter-rotation of said annular nut.

8. The mechanically-actuated disc brake according to claim 7, wherein said cylindrical actuating member includes a rearwardly-protruding shaft, having a hollow axial passageway therethrough communicating with the inside of said cylindrical actuating member and wherein said adjusting means includes means for manually rotating said push rod with respect to said annular nut, whereby said push rod is selectively advanced in said forward direction, or retracted in said rearward direction, relative to said annular nut, said manual means including an annular ring coaxially fixed within said cylindrical actuating member, said annular ring having internal teeth thereon, an abutment member having one-way ratchet teeth and torque-transmitting means thereon, said abutment member being coaxially fixed to 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 annular nut thereby selectively advancing or retracting said push rod, said one-way ratchet teeth being oriented such that said push rod may be manually retracted until said one-way ratchet teeth engage said internal teeth on said annular ring.

9. The mechanically-actuated disc brake according to claim 7, further comprising a washer rotationally fixed to said push rod and having an outer portion frictionally engaging said nonrotatable cam member so as to frictionally resist rotation of said push rod with respect to said nonrotatable cam member.

10. 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 caliper having a pair of legs straddling said friction element means, one of said legs 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 helical cam assembly in juxtaposed relation with said bore, said helical cam assembly including a rotatable and a nonrotatable cam member, whereby upon rotation of said rotatable cam member, said nonrotatable cam member axially translates in a forward brake-applying direction, a push rod communicating with said friction element means, having a portion thereof coaxially positioned within, and circumscribed by, said helical cam assembly, an annular nut circumscribing and threadably engaging said push rod, said annular nut having a shank portion, coaxially positioned within said helical cam assembly, and a radially-projecting flange communicating with said nonrotatable cam member, whereby said nonrotatable cam member urges the combination of said annular nut and push rod in said forward brake-applying direction in response to rotation of said rotatable cam member, thereby effecting frictional engagement of said friction element means with said rotor friction surface, means for biasing the combination of said annular nut and push rod in a rearward brake-releasing direction, upon counter-rotation of said rotatable cam member, adjusting means for rotating said annular nut relative to said push rod thereby forwardly advancing said push rod with respect to said nut, said adjusting means including a cylindrical brake actuating member coaxially positioned within said helical cam assembly, circumscribing said annular nut, and rotationally interlocked with said rotatable cam member whereby rotation of said actuating member effects rotation of said rotatable cam member, plate clutch means for rotating said annular nut with respect to said push rod in response to rotation of said cylindrical brake actuating member, said plate clutch means including an annular inner clutch plate frictionally engaged on each side thereof by an annular outer clutch plate, said inner and outer clutch plates circumscribing said annular nut, each of said outer clutch plates including at least one internal tang projecting radially inward and engaging an axial slot in said annular nut, said inner clutch plate including at least one external tang projecting radially outward and engaging an axial slot in said cylindrical actuating member, the circumferential width of said axial slot in said cylindrical actuating member being greater than the circumferential width of said external tang whereby said annular nut is rotated with respect to said push rod after a predetermined rotation of said cylindrical actuating member, clutch biasing means for maintaining said outer clutch plates in frictional engagement with said inner clutch plate, a one-way spring brake helically circumscribing said shank portion of said nut and in frictional engagement therewith, one end of said one-way spring brake being rotationally fixed to said nonrotatable cam member, thereby allowing said annular nut to rotate so as to forwardly advance said push rod and frictionally resisting counter-rotation of said annular nut.

11. The mechanically-actuated disc brake according to claim 10, wherein said cylindrical actuating member includes a rearwardly-protruding shaft, having a hollow axial passageway therethrough communicating with the inside of said cylindrical actuating member and wherein said adjusting means includes means for manually rotating said push rod with respect to said annular nut, whereby said push rod is selectively advanced in said forward direction, or retracted in said rearward direction, relative to said annular nut, said manual means including an annular ring coaxially fixed within said cylindrical actuating member, said annular ring having internal teeth thereon, an abutment member having one-way ratchet teeth and torque-transmitting means thereon, said abutment member being coaxially fixed to 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 annular nut thereby selectively advancing or retracting said push rod, said one-way ratchet teeth being oriented such that said push rod may be manually retracted until said one-way ratchet teeth engge said internal teeth on said annular ring.

12. The mechanically-actuated disc brake according to claim 10, further comprising a washer rotationally fixed to said push rod and having an outer portion frictionally engaging said nonrotatable cam member so as to frictionally resist rotation of said push rod with respect to said nonrotatable cam member.

13. 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 caliper having a pair of legs straddling said friction element means, one of said legs 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 helical cam assembly in juxtaposed relation with said bore, said helical cam assembly including a rotatable and a nonrotatable cam member, whereby upon rotation of said rotatable cam member, said nonrotatable cam member axially translates in a forward brake-applying direction, a push rod communicating with said friction element means, having a portion thereof coaxially positioned within, and circumscribed by, said helical cam assembly, an annular nut circumscribing and threadably engaging said push rod, said annular nut having a shank portion, coaxially positioned within said helical cam assembly, and a radially-projecting flange communicating with said nonrotatable cam member, whereby said nonrotatable cam member urges the combination of said annular nut and push rod in said forward brake-applying direction in response to rotation of said rotatable cam member, thereby effecting frictional engagement of said friction element means with said rotor friction surface, means for biasing the combination of said annular nut and push rod in a rearward brake-releasing direction upon counter-rotation of said rotatable cam member, adjusting means for rotating said annular nut relative to said push rod thereby forwardly advancing said push rod with respect to said nut, said adjusting means including a cylindrical brake actuating member coaxially positioned within said helical cam assembly, circumscribing said annular nut, and rotationally interlocked with said rotatable cam member whereby rotation of said actuating member effects rotation of said rotatable cam member, plate clutch means for rotating said annular nut with respect to said push rod in response to rotation of said cylindrical actuating member, said plate clutch means including an annular inner clutch plate frictionally engaged on each side thereof by an annular outer clutch plate, said inner and outer clutch plates circumscribing said annular nut, each of said outer clutch plates including at least one external tang projecting radially outward engaging an axial slot in said cylindrical actuating member, said inner clutch plate including at least one internal tang projecting radially inward and engaging an axial slot in said annular nut, clutch biasing means for maintaining said outer clutch plates in frictional engagement with said inner clutch plate, a one-way spring brake helically circumscribing said shank portion of said nut and in frictional engagement therewith, one end of said one-way spring brake having a radial projection thereon, said projection engaging an axial slot in said nonrotatable cam member, the circumferential width of said axial slot in said nonrotatable cam member being greater than the circumferential width of said projection, whereby said push rod is forwardly advanced with respect to said annular nut after a predetermined rotation of said cylindrical actuating member, thereby allowing said annular nut to rotate so as to forwardly advance said push rod and frictionally resisting counter-rotation of said annular nut.

14. The mechanically-actuated disc brake according to claim 13, wherein said cylindrical actuating member includes a rearwardly-protruding shaft, having a hollow axial passageway therethrough communicating with the inside of said cylindrical actuating member and wherein said adjusting means includes means for manually rotating said push rod with respect to said annular nut, whereby said push rod is selectively advanced in said forward direction, or retracted in said rearward direction, relative to said annular nut, said manual means including an annular ring coaxially fixed within said cylindrical actuating member, said annular ring have internal teeth thereon, an abutment member having one-way ratchet teeth and torque-transmitting means thereon, said abutment member being coaxially fixed to said push rod, whereby a torque tool may be inserted through said axial passageway in said shaft to engage said torque-tramsmitting means and rotate said push rod with respect to said annular nut thereby selectively advancing or retracting said push rod, said one-way ratchet teeth being oriented such that said push rod may be manually retracted until said one-way ratchet teeth engage said internal teeth on said annular ring.

15. The mechanically-actuated disc brake according to claim 13, further comprising a washer rotationally fixed to said push rod and having an outer portion frictionally engaging said nonrotatable cam member so as to frictionally resist rotation of said push rod with respect to said nonrotatable cam member.

16. In 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 caliper having a pair of legs straddling said friction element means, one of said legs 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 helical cam assembly in juxtaposed relation with said bore, said helical cam assembly including a rotatable and a nonrotatable cam member, whereby upon rotation of said rotatable cam member, said nonrotatable cam member axially translates in a forward brake-applying direction, a push rod, communicating with said friction element means, having a portion thereof coaxially positioned within, and circumscribed by, said helical cam assembly, an annular nut circumscribing and threadably engaging said push rod, said annular nut having a shank portion, coaxially positioned within said helical cam assembly, and a radially-projecting flange communicating with said nonrotatable cam member, whereby said nonrotatable cam member urges the combination of said annular nut and push rod in said forward brake-applying direction in response to rotation of said rotatable cam member, thereby effecting frictional engagement of said friction element means with said rotor friction surface, and means for biasing the combination of said annular nut and push rod in a rearward brake-releasing direction upon counter-rotation of said rotatable cam member, the improvement comprising adjusting means for rotating said annular nut relative to said push rod, thereby forwardly advancing said push rod with respect to said annular nut, said adjusting means including a brake actuating member rotationally interlocked with said rotatable cam member whereby rotation of said brake actuating member effects rotation of said rotatable cam member, plate clutch drive means transversely positioned between said rotatable cam member and said annular nut, said clutch drive means including lost motion means, whereby said push rod is forwardly advanced with respect to said annular nut in response to a predetermined rotation of said brake actuating member.

17. 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 caliper having a pair of legs straddling said friction element means, one of said legs 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 helical cam assembly in juxtaposed relation with said bore, said helical cam assembly including a rotatable and a nonrotatable cam member, whereby upon rotation of said rotatable cam member, said nonrotatable cam member axially translates in a forward brake-applying direction, a push rod communicating with said friction element means, having a portion thereof coaxially positioned within, and circumscribed by, said helical cam assembly, an annular nut circumscribing and threadably engaging said push rod, said annular nut having a shank portion, coaxially positioned within said helical cam assembly, and a radially-projecting flange communicating with said nonrotatable cam member, whereby said nonrotatable cam member urges the combination of said annular nut and push rod in said forward brake-applying direction in response to rotation of said rotatable cam member, thereby effecting frictional engagement of said friction element means with said rotor friction surface, means for biasing the combination of said annular nut and push rod in a rearward brake-releasing direction, upon counter-rotation of said rotatable cam member, adjusting means for rotating said annular nut relative to said push rod thereby forwardly advancing said push rod with respect to said nut, said adjusting means including a brake actuating member rotationally interlocked with said rotatable cam member whereby rotation of said brake actuating member effects rotation of said rotatable cam member, plate clutch means for rotating said annular nut with respect to said push rod in response to rotation of said rotatable cam member, said plate clutch means including an annular inner clutch plate frictionally engaged on each side thereof by an annular outer clutch plate, said inner and outer clutch plates circumscribing said annular nut, each of said outer clutch plates including at least one internal tang projecting radially inward and engaging an axial slot in said annular nut, said inner clutch plate including at least one external tang projecting radially outward and engaging an axial slot in said rotatable cam member, the circumferential width of said axial slot in said rotatable cam member being greater than the circumferential width of said external tang whereby said annular nut is rotated with respect to said push rod after a predetermined rotation of said brake actuating member, clutch biasing means for maintaining said outer clutch plates in frictional engagement with said inner clutch plate, a one-way spring brake helically circumscribing said shank portion of said nut and in frictional engagement therewith, one end of said one-way spring brake being rotationally fixed to said nonrotatable cam member, thereby allowing said annular nut to rotate so as to forwardly advance said push rod and frictionally resisting counter-rotation of said annular nut.

18. The mechanically-actuated disc brake according to claim 17, wherein said brake actuating member includes a rearwardly-protruding shaft, having a hollow axial passageway therethrough communicating with the inside of said brake actuating member and wherein said adjusting means includes means for manually rotating said push rod with respect to said annular nut, whereby said push rod is selectively advanced in said forward direction, or retracted in said rearward direction, relative to said annular nut, said manual means including an annular ring coaxially fixed within said brake actuating member, said annular ring having internal teeth thereon, an abutment member having one-way ratchet teeth and torque-transmitting means thereon, said abutment member being coaxially fixed to 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 annular nut thereby selectively advancing or retracting said push rod, said one-way ratchet teeth being oriented such that said push rod may be manually retracted until said one-way ratchet teeth engage said internal teeth on said annular ring.

19. The mechanically-actuated disc brake according to claim 17, further comprising a washer rotationally fixed to said push rod and having an outer portion frictionally engaging said nonrotatable cam member so as to frictionally resist rotation of said push rod with respect to said nonrotatable cam member.