Brakes – Wheel – Axially movable brake element or housing therefor
Patent
1994-09-20
1996-07-23
Oberleitner, Robert J.
Brakes
Wheel
Axially movable brake element or housing therefor
188 111, 188 7338, F16D 5522, F16D 6600
Patent
active
055381030
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention is concerned with a floating caliper disc brake wherein the brake shoes, in the brake releasing direction, are preloaded by means of expander springs to support the adjustment of a brake clearance between the brake shoe and the brake disc after applying the brake.
BACKGROUND OF THE INVENTION
A disc brake of the afore-described type is taught, for example, by DE-OS 29 31 071. In the state-of-the-art disc brake, a wire spring bent in S-type manner is located in the center of the brake. The ends of the wire spring are in abutment with the back plates of the brake shoes, thereby preloading the brake shoes in the brake releasing direction. One end of the wire spring is secured to a piston-sided brake shoe. The wire spring, hence, is "floatingly" arranged rather than secured to a stationary point of fixation.
With an increasing wear of the friction pads, the floating caliper will displace along with the outer brake shoe disposed opposite the actuator while the piston-sided brake shoe in abutment with the actuator will displace relative to the floating frame and to, the expander spring, by an amount corresponding to the aggregate of the two worn friction pad strengths. In view of the non-symmetrical arrangement of floating caliper-type disc brakes relative to the displacement paths of the brake shoes, a "floating" expander spring does not always ensure, after braking, a uniform distribution of the brake clearance among the two brake shoes.
Moreover, electrical indicators for displaying the pad wear of the brake pads are known in the art. Such indicators comprise, for example, an electrical contact provided on the brake pad, which with a pad increasingly worn, is closed or discontinued. However, an indicator of this type is suitable only to warn against worn-out brake pads rather than to continuously display the pad strength. Other means suitable for a continuous display make use, for example, of the displacement of the brake caliper vis-a-vis the brake carrier firmly anchored to the steering knuckle of the vehicle, which grows with an increasing pad wear. For this purpose, usually, a variable electrical resistor having a displaceable slider is used. The disadvantage involved with the latter means resides in the relatively complex design thereof causing rather high manufacturing costs.
It is the object of the invention to provide a floating caliper disc brake having uniform distribution of the brake clearance among the brake shoes.
Another object of the invention is to provide a low-cost electrical pad wear indicator.
SUMMARY OF THE INVENTION
An expander spring is attached on a stationary point of the disc brake to a carrier arm of the brake carrier. Respectively two spring struts extend from the point of attachment symmetrically disposed above the outer rim of the brake disc into the brake, where they are in abutment with the back plates of the brake shoes, preloading the same in the brake releasing direction. In view of their stationary fixation, the expander spring is not displaced in whole if, with an increasing friction pad wear, the floating caliper and, relative thereto, the piston-sided brake shoe are displaced in opposite axial directions. It is only the spring struts of the expander spring that are axially displaced symmetrically with respect to one another. The arrangement according to the invention insures a uniform distribution of the brake clearance among the two brake shoes.
Preferred embodiments of the invention are particularly advantageous in view of their simple, low-cost and functional designs.
In a preferred embodiment means is provided for protecting correspondingly designed expander springs for use in a disc brake according to the invention.
A further embodiment includes the use of a strain gauge for permitting a continuous display of the pad wear involving extremely low manufacturing efforts. With an increasing pad wear, the brake pads displace via-a-vis the brake carrier to which the expander spring is clamped, with the spring struts being defle
REFERENCES:
patent: 4410069 (1983-10-01), Schreiunen et al.
patent: 4415068 (1983-11-01), Gumkowski et al.
patent: 4491204 (1985-01-01), Dirauf et al.
patent: 4527664 (1985-07-01), Le Marchaud
patent: 4546298 (1985-10-01), Wickham et al.
patent: 5069313 (1991-12-01), Kato et al.
Rueckert Helmut
Teitge Hilmar
Weidenweber Michael
ITT Automotive Europe GmbH
Lewis J. Gordon
Oberleitner Robert J.
Schwartz Chris
Twomey Thomas N.
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