Brakes – Wheel – Transversely movable
Patent
1990-10-22
1993-02-09
Oberleitner, Robert J.
Brakes
Wheel
Transversely movable
188196BA, 192111A, F16D 6560
Patent
active
051847019
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to devices for the operation of drum brakes used for trucks or trailers and in particular with devices for the adjustment of the clearance between the brake lining and the drums.
In the adjustment device described in French Patent 2,277,274, a cam for adjusting the clearance of the brake shoes is driven by means of a shaft, lever and gear. The adjustment is effected by a helical gears driving the gear on the camshaft.
Devices for automatic clearance adjustment which attempt to progressively ratchet the cam at each operation of the brake are described in French Patent Nos. 2,389,042 and 2,224,676. In these devices, the brake shoes are kept against the drums for a certain length of time. This causes wear of the brake lining and an overheating of the drums, which can over a long period cause a blow-out of the tires.
French Patent Nos. 1,604,913 and 2,238,090 show ratcheting systems which insure, at each braking, a cancellation of the clearance, which may exist at rest between the brake lining and the drums, without thereby introducing a residual braking. However, this reduction of clearance does not permit the retrieving of the clearance, which is recommended in order to account especially for the successive expansions due to prolonged brakings. Also, these devices may produce certain wheel lock-ups, which are a detriment to the stability of the vehicle and to the life of the tires.
SUMMARY OF THE INVENTION
The present invention intends to remedy the disadvantages of the above-mentioned devices and provides a clearance adjustment device which permits a considerable reduction in the wear of brake linings and brakes and yet to keeps an optimum permanency of clearance between the linings and the drums.
A brake clearance adjuster includes a brake actuating camshaft; an intermediary ring in splined engagement with the camshaft, the ring having a plurality of teeth on its periphery, each tooth having an undercut wall; a hub having a brake operating lever attached thereto and a circular bore concentrically disposed about the camshaft, the bore having at least one radially extending rectangular receptacle around its circumference, each receptacle having a width in the circumferential direction of the bore; and a plurality of generally rectangular ratchets, each located in one of the receptacles and having a tapered tooth having an undercut wall adapted to mate with one of the undercut walls in the intermediary ring and having a width in the circumferential direction of the bore less than the width of the receptacles by an amount in proportion to a desired brake clearance, the hub being freely rotatable in one direction about the camshaft but engaging the camshaft to turn with the hub in the opposite direction when one of the ratchet teeth mates with one of the intermediary ring teeth.
The brake clearance adjuster may also include another hub having an adjusting lever attached thereto and a circular bore concentrically disposed about the camshaft adjacent to the first hub, the bore having a plurality of radially extending rectangular receptacles along its circumference; a plurality of generally rectangular ratchets, each located in the receptacles of said other hub and adapted to engage with one of the intermediate ring teeth; and an actuator connected between the operating lever and the adjusting lever, the actuator being adapted to alternately rotate the levers apart and together, thereby alternately ratcheting the hubs around the camshaft until a desired brake clearance is achieved.
Another embodiment of the invention also includes a pair of ratchet wheels attached coaxially with the bore to opposite sides of the hub; a manual adjustment lever having two parallel arms pivoted about the camshaft, each arm having a radial slot therein, the arms being joined at a point removed from the ratchet wheels; and a ratchet retained in the adjustment lever slots, manual movement of the manual adjustment lever ratcheting the hub around the camshaft.
Another additional embod
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Ballato Jose A.
Oberleitner Robert J.
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