Brakes – Wheel – Transversely movable
Patent
1993-10-12
1997-01-07
Ballato, Josie
Brakes
Wheel
Transversely movable
188332, F16D 6522
Patent
active
055907474
DESCRIPTION:
BRIEF SUMMARY
This 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. In this case, the mechanical control may constitute a parking brake or emergency brake.
In a known fashion, drum brakes usually comprise a support plate on which there are slideably mounted two shoes. Each shoe comprising a web and a rim whose face opposite the drum receives a friction lining capable of being brought into frictional engagement against the drum by a hydraulic actuation device the actuation device acts on a first end of the webs of the shoes. A strut of variable length determines the spacing of the shoes which are located in the vicinity of the hydraulic actuation device. A second end of the web of each shoe bears on a bearing component securely fastened to the support plate. A spring urges the shoes against the strut when the brake motor is not actuated.
In general, a mechanical actuation lever has a first end articulately located on the web of one of the shoes. The actuation lever has a slot at an intermediate point close to this articulation to interact with the strut of variable length and allow the shoes to be stressed away from each other under the action of a control cable fastened to a second end of the lever.
Such an arrangement of hydraulic and mechanical actuator is known in the art by the expression "with floating shoes". This is due to the absence of anchorage of the webs of the shoes on the bearing component securely fastened to the support plate. Such brakes require the mechanical actuator to provide a very large actuation force.
Other drum brake arrangements are known in the art by the expression "twin-booster". Such a turn booster does 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 have very mediocre stability and the wear of the friction linings is very unbalanced.
Document EP-A-O419,171 makes known a drum brake combining the two abovementioned arrangements, in which the brake is of floating shoe design when operated hydraulically, and of twin-booster design when operated mechanically. However, in this drum brake the mechanical-control device varies depending on the state of the drum brake.
The object of the present invention is therefore to produce a drum brake having the advantages of the two arrangements recalled hereinabove without exhibiting the drawbacks of this known system.
This object is achieved, according to the invention, with a mechanical actuation device acting between one of the shoes and a first end of a force transmission device mounted slideably on the other shoe, a second end of the force transmission device bearing on the strut of variable length, and the mechanical actuation device is arranged in the vicinity of the bearing component between the second ends of the webs of the shoes.
Other objects, features and advantages will emerge clearly from the description which follows of an embodiment of the invention given by way of nonlimiting example, with reference to the appended drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 represents a front view of a drum brake produced in accordance with the present invention;
FIG. 2 represents a force transmission device used in the drum brake of FIG. 1;
FIG. 3 represents a variant of the mechanical actuation device of FIG. 1; and
FIG. 4 represents another variant of the mechanical actuation device of FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
The drum brake represented in FIG. 1 comprises a support plate 10 consisting of an approximately plane disk. This plate 10 is provided so as to be rigidly fastened to a fixed part of the vehicle, such as an axle flange (not shown).
Two brake shoes 12 and 14 are supported in a sliding fashion by the disk of the support plate 10, by virtue of usual mechanisms (not shown). In a well-known fashion, each of the shoes 12 and 14 comprises an approximately pl
REFERENCES:
patent: 2077939 (1937-04-01), Brie
patent: 2161640 (1939-06-01), Schnell
patent: 2400043 (1946-05-01), Goepfrich
patent: 4336867 (1982-06-01), Woo
patent: 4678067 (1987-07-01), Thompson
patent: 5275260 (1994-01-01), Evans et al.
Mery Jean Claude
Pressaco Pierre
Ballato Josie
McCormick Jr. Leo H.
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