Brakes – Wheel – Transversely movable
Patent
1986-05-13
1987-11-17
Kashniow, Andres
Brakes
Wheel
Transversely movable
188196BA, 188 795R, F16D 5152
Patent
active
047067837
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an automatic adjusting device for a brake, especially a motor vehicle brake with which a strut is connected in parallel with a brake actuator and has an effective length which depends on the relative positions of two strut members adjustable with respect to each other and one of them having an adjustable portion which tends to extend the strut, by this portion, upon actuation of the brake and cooperates with at least one intermediate member arranged at least partly between a web plate and a piston to transmit the brake actuating force independently of the strut and being movable at least in part as long as the brake actuating force does not exceed a predeterminable amount.
In a known adjuster of this kind (DE-OS No. 32 44 872) a pivotable, disc-like strut member has a knurled portion which is disposed eccentrically with respect to the pivot axis and movable transversely of the longitudinal direction of the strut. In released condition of the brake the knurled portion engages a knurled portion which is formed at the second strut member. By an arm the disc-like strut member engages in a recess in the web plate. Upon actuation of the brake the two strut members move apart and the disc-like strut member is pivotable by the arm such that, upon release of the brake, a part of the knurled portion more remote from the pivot axis enters into contact with the knurled portion of the second strut member. Hereby the length of the strut is increased for automatic compensation of clearance resulting from wear of the friction lining of the brake shoes.
Another known adjusting device of this kind (DE-OS No. 30 19 223) comprises a strut whose adjustable portion comprises a threaded bolt. The length of the strut is variable by a pinion connected with the threaded bolt when the pinion is rotated by a pivotably supported adjusting member engaging the same. Moreover, the length of the strut is variable in length by means of a built-in bimetal strip. Hereby the adjusting device balances undue clearance between the friction lining and a brake drum caused by wear of the friction lining of the brake shoes, whereas any clearance caused by expansion of the brake drum due to the heat development during braking does not lead to any change in length of the strut and thus to excessive adjustment.
Likewise known is an automatic adjuster (DE-OS No. 30 19 214) with which the adjusting member can be disengaged by means of a bimetal strip so that clearance due to thermal expansion of the brake drum does not lead to a change in length of the strut.
The clearance to be compensated is a clearance to ease the brake corresponding to the difference between the brake drum diameter and the diameter of the brake shoes with the brake in inactive and unheated condition.
The diameter of the brake shoes can be determined by an axial line extending vertically to the connecting line of the hydraulic actuator with the center of the brake drum. The clearance to ease the brake results in a loss distance which may be increased still further by thermal expansion of the brake drum at high temperatures and by the elastic deformation due to high brake actuating forces. This proportion is of influence especially in brakes of weight-saving light structure.
Likewise known are brakes with which an additional loss distance is passed upon actuation of the brake so as to prevent pivoting of the adjusting lever in response to the value of the brake actuating force. To fulfill this function, this loss distance is required only with cold brakes; with the known embodiments it remains unchanged also with the brake already heated.
In general, the loss distance is of less importance in an unheated brake than in a highly heated brake because in this event the hydraulic actuator must be subjected to higher pressure in order to compensate a reduction of the frictional value of a friction lining caused by the heating. If the loss distance is too great, the volume of brake fluid supplied by a main cylinder no longer may be sufficient to build up the required
REFERENCES:
patent: 2264454 (1941-12-01), Para
patent: 2292017 (1942-08-01), Smith
patent: 4502573 (1985-03-01), Carre
Holz Dietrich
Rath Heinrich-Bernhard
Kashniow Andres
Lucas Industries Public Limited Company
Oberleitner Robert J.
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