Brakes – Wheel – Transversely movable
Patent
1995-03-15
1996-09-10
Oberleitner, Robert J.
Brakes
Wheel
Transversely movable
74532, 188106F, F16D 5150
Patent
active
055536913
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to mechanically actuated drum brakes, this mechanical control constituting an auxiliary means for actuating the drum brake which already possesses a main brake motor, for example hydraulic, the mechanical control constituting a parking brake or emergency brake.
BACKGROUND OF THE INVENTION
More precisely, the invention relates to a drum brake comprising a support plate, first and second shoes slidably mounted on the support plate and each one comprising a web and a rim, each rim having, opposite the drum, a face bearing a friction lining; a hydraulic actuation device, capable of acting on a first end of the web of each shoe to press its friction lining against the drum; a first spacer of variable length arranged between the shoes in the vicinity of the first end of their respective webs, to determine the separation of these shoes; a bearing component secured to the support plate and capable of acting as a bearing face for the second end of the web of each shoe; and a mechanical actuation device.
SUMMARY OF THE INVENTION
In general, this mechanical actuation device comprises a lever articulated at one of its ends to the web of one of the shoes and comprising, at an intermediate point close to this articulation, a slot provided so as to interact with the spacer of variable length and allow the shoes to be stressed away from each other under the action of a control cable fastened to the other end of the lever.
Such an arrangement of hydraulic and mechanical actuators, known in the art by the expression "with floating shoes" due to the absence of anchorage of the webs of the shoes on the bearing component securely fastened to the support plate, requires the mechanical actuator to make use of a very large actuation force.
Other drum brake arrangements are known, for example from the document FR-A-2 536 142, and known in the art by the expression "twin-booster", which do not have a bearing component between the ends of the webs of the shoes which are then articulated to one another. Such brakes have very high efficiency, but very mediocre stability during hydraulic actuation, and lead to very unbalanced wear in the friction linings.
The object of the present invention is therefore to produce a drum brake having the advantages of the two arrangements recalled hereinabove without exhibiting their drawbacks.
To this end, the invention proposes producing a drum brake of floating shoe design when it is actuated hydraulically, and of twin-booster design when it is actuated mechanically.
This object is achieved, according to the invention, with a mechanical actuation device which comprises a first actuating lever, a second force-distributing lever, and a second spacer which is arranged between the shoes in the vicinity of the second end of their respective webs, the first lever having a first end capable of receiving an actuation force, and a second end which is opposite the first and via which this lever can press, under the effect of the actuation force, against the first shoe to force it toward the drum, the second lever having first and second ends bearing on the respective ends of the first and second spacers which are located on the first shoe side, and the first and second levers being articulated on one another at an articulation point which is intermediate between their respective ends.
Preferably, a slight clearance exists, at rest, between the second ends of the webs of the shoes and the bearing component, and the first and second levers are arranged on either side of the web of the first shoe.
Other objects, features and advantages will emerge clearly from the description which follows of an embodiment of the invention given by way of non-limiting example, with reference to the appended drawings.
BRIEF DESCRIPTION OF THE INVENTION
FIG. 1 represents a front view of a drum brake produced in accordance with the present invention;
FIG. 2 represents a sectional view along the line II--II of FIG. 1;
FIG. 3 represents a perspective view of a mechanical actuation lever used in
REFERENCES:
patent: 2775315 (1956-12-01), Maruhn et al.
patent: 3708044 (1973-01-01), Torri et al.
patent: 3757908 (1973-09-01), Fisher
patent: 4678067 (1987-07-01), Thompson
patent: 5484042 (1996-01-01), Wang
Mery Jean Claude
Pressaco Pierre
AlliedSignal Europe Services Techniques
McCormick Jr. Leo H.
Oberleitner Robert J.
Schwartz Chris
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