Title: Automatic slack adjuster for vehicle brakes

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1. An automatic slack adjuster for a vehicle brake system of the type comprising a braking member and a cam shaft operatively connected thereto for rotation about its axis of rotation by said member to oscillate a cam member; said slack adjuster comprising a first gear mounted in said braking member and nonrotatably mounted on said cam shaft to form an angularly adjustable connection between said braking member and said cam shaft; a gear shaft in said braking member and carrying a second gear engaging with said first gear for angular adjustment thereof; means frictionally engaging said gear shaft; an actuator mounted on said gear shaft and rotatable relative thereto; a one-way clutch operatively connecting said actuator and said gear shaft upon rotation of the actuation in a first direction; spring means encompassing said gear shaft and acting to place a predetermined torque on said actuator; said gear shaft, second gear, friction means, actuator, one-way clutch and spring means positioned in concentric relationship; and means for rotating said actuator in a second direction in response to movement of said braking member in a brake applying direction with said spring means effective to rotate said actuator in the first direction in response to movement of said braking member in a brake releasing direction.

2. An automatic slack adjuster as set forth in claim 1, in which said actuator rotating means comprises a link connecting said actuator with a power transmitting means.

3. An automatic slack adjuster as set forth in claim 2, in which said link has a slotted opening at one end providing limited lost motion in both directions of movement of said actuator.

4. An automatic slack adjuster as set forth in claim 1, in which said spring means comprises a pretorqued spring engaging said actuator.

5. An automatic slack adjuster as set forth in claim 1, in which said friction means includes a spring-loaded seal element surrounding said gear shaft.

6. An automatic slack adjuster as set forth in claim 1, including limit stop means acting to retain the actuator in a pretorqued position and limit rotation of the actuator in said first direction.

7. An automatic slack adjuster as set forth in claim 6, in which said limit stop means includes a stop member in said braking member and cooperating with a stop surface formed on said actuator.

8. An automatic slack adjuster as set forth in claim 1, wherein said actuator has a cylindrical hub telescopingly received on a reduced portion of the gear shaft, and said one-way clutch comprises a helical spring clutch encompassing and adapted to engage the actuator hub and the adjacent portion of the gear shaft.

9. An automatic slack adjuster for a vehicle brake system of the type comprising a rotatably mounted braking lever and a cam shaft operatively connected thereto for rotation about the axis of rotation of said lever to oscillate a cam member, said slack adjuster comprising a worm gear mounted in said lever and non-rotatably mounted on said shaft to form an angularly adjustable connection between said braking lever and said cam shaft, a worm shaft in said lever and carrying a worm engaging with said worm gear for angular adjustment thereof, an actuator mounted on said worm shaft and rotatable relative thereto, a one-way clutch connecting said actuator and said worm shaft and acting to drive said worm shaft upon rotation of the actuator in a first direction, spring means encompassing said worm shaft and tending to rotate said actuator in said first direction, said worm shaft, worm, actuator, one-way clutch and spring means positioned in concentric relationship, and means for rotating said actuator in a second direction in response to angular movement of said brake applying lever in the braking direction with said spring means effective to rotate said actuator in said first direction in response to movement of said braking member in a brake releasing direction.

10. An automatic slack adjuster as set forth in claim 9, in which said actuator rotating means comprises a link connecting said actuator with a power transmitting means.

11. An automatic slack adjuster as set forth in claim 10, in which said link has an elongated slot, the length of said slot providing for lost motion of the link relative to said actuator corresponding to the running clearance of the brake shoes relative to the brake drum of the vehicle brake system.

12. An automatic slack adjuster as set forth in claim 9, in which said spring means comprises a pretorqued spring engaging said actuator.

13. An automatic slack adjuster as set forth in claim 9, including friction means in said lever engaging said worm shaft.

14. An automatic slack adjuster as set forth in claim 13, in which said friction means includes a spring-loaded seal element surrounding said worm shaft.

15. An automatic slack adjuster as set forth in claim 12, including limit stop means acting to retain the actuator in a pretorqued condition.

16. An automatic slack adjuster as set forth in claim 15, wherein said limit stop means includes a stop member mounted in said lever and projecting towards said actuator, and a stop surface formed on said actuator and cooperating with said stop member to limit rotation of the actuator in said first direction.

17. An automatic slack adjuster as set forth in claim 9, wherein said actuator has a cylindrical hub and said worm shaft has a reduced diameter portion telescopingly receiving said actuator hub thereon, the external diameters of said worm shaft and said hub being substantially equal, and said one-way clutch encompassing said worm shaft and said hub.

18. An automatic slack adjuster as set forth in claim 17, wherein said one-way clutch comprises a helical spring clutch engaging said worm shaft and actuator hub, said spring clutch being wound so as to engage said shaft and hub when said actuator is rotated in said first direction.

19. An automatic slack adjuster as set forth in claim 17, wherein said spring means comprises a torsion spring encompassing said one-way clutch, one end of said spring engaging said lever and the opposite end engaging said actuator to place a predetermined torque on the actuator.

20. An automatic slack adjuster as set forth in claim 19, in which said one-way clutch comprises a helical spring engaging adjacent surfaces of said worm shaft and actuator and wound so as to grip said surfaces on rotation of said actuator in said first direction.

21. An automatic slack adjuster as set forth in claim 9, wherein said lever is connected to a power transmitting means so as to be operable thereby for rotation of the lever about its axis of rotation, and linkage means interconnecting said brake operating means with said actuator.

22. An automatic slack adjuster as set forth in claim 21, in which said linkage means comprises an elongated link, said actuator having a laterally extending arm, said link being pivotally connected at one end to said actuator arm and at the opposite end to said power transmitting means.

23. An automatic slack adjuster as set forth in claim 22, wherein said actuator arm has a pivot pin adjacent the outer end thereof, and said link has an elongated slot adjacent said opposite end receiving said pivot pin.

24. An automatic slack adjuster as set forth in claim 23, in which said elongated slot provides limited lost motion in both directions of movement of said link.

25. An automatic slack adjuster as set forth in claim 9, including a limit stop member mounted in said lever and projecting towards said actuator, said actuator having an arcuate recess formed therein and defining a stop surface cooperating with said stop member to limit the extent of rotation of said actuator in said first direction, said worm shaft having a reduced diameter portion, said actuator having a cylindrical hub telescoping over the reduced diameter portion of the worm shaft, the external diameters of the worm shaft and the hub being substantially equal, said one-way clutch comprising a helical spring engaging the adjacent external surfaces of the worm shaft and actuator hub and wound so as to grip said surfaces upon rotation of said actuator in said first direction, said spring means comprising a torsion spring encompassing said one-way clutch with the opposite spring ends anchored in said lever and said actuator so as to place a predetermined torque on the actuator, said actuator having a laterally extending arm, power transmitting means connected to said lever, and an elongated link pivotally connected at one end to said power transmitting means and pivotally connected at the opposite end to said actuating arm, said link having an elongated slot adjacent said opposite end and receiving a pivot pin forming the pivotal connection with said actuating arm to provide a predetermined lost motion corresponding to the normal running clearance between the brake shoes and the brake drum of the vehicle brake system.

Other info:

Inventors: Zeidler, Reinhold Carl (Birmingham, MI, US)

Application Number: 609769
Filing Date: 1975-09-02
Publication_date: 1976-12-14
Assignee: Borg-Warner Corporation (Chicago, IL)
Primary Class(es): 188/79.55 188/196BA
Other Classes:
US Patent Ref:

2920724	Jan, 1960	Margetic et al.	188/79.
3351163	Nov, 1967	Sander et al.	188/79.
3901357	Aug, 1975	Reitz et al.	188/79.

Other Refs:
Primary Examiner: Reger, Duane A.
Assistant Examiner:
Attorney: Geppert; James A.