Brakes – Wheel – Axially movable brake element or housing therefor
Patent
1993-05-06
1996-01-30
Oberleitner, Robert J.
Brakes
Wheel
Axially movable brake element or housing therefor
188 726, F16D 5508
Patent
active
054874521
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a clamping device consisting of two substantially parallel plates of which one at least may be driven in rotational movement about an axis perpendicular to its surface, a plurality of guide cavities hollowed out in at least one of these plates at a distance from the axis and a plurality of corresponding balls inserted into the cavities and gripped between the two plates, each guide cavity forming a cam and providing a bearing surface rising monotonically, covering a non-nil angle of the rotational movement, from a portion of maximum depth to the surface of the plate.
Devices of this type are well known in the prior art and are used, for example, as shown in U.S. Pat. No. 3,638,763 for the clamping operation of hand brakes in motor vehicles.
A problem usually arising in these devices is how to obtain the highest possible clamping force for a relative rotation of the plates corresponding to the shortest possible displacement of the balls in the guide cavities, the load needed to obtain this rotation being limited to the lowest possible value.
To this end, it is known, for example from European Patent Application No. 0,209,271 how to intervene on the shape of the guide cavities and in particular how to decrease the slope of these cavities from their zone of maximum depth to the vicinity of the surface of the plate in which they are hollowed out.
However, besides the fact that the known devices may induce relatively important production problems, due to the optionally sophisticated shapes they adopt none of them totally optimizes the ratio between the travel and the operational load of the clamping device and the force generated by the latter.
The invention is based on the exposure of this fact, and proposes to lead to this optimation.
To this end, the device according to the invention is substantially characterized in that the portion of maximum depth of the guide cavity forms a housing for the corresponding ball, which holds it in a single determined position, and in that this cavity consists, in a portion of lesser depth, of a ramp which intercepts the housing in a plurality of points of intersection in the direct vicinity of which, on the one hand, the ball forms a first slope tangent with the housing, and in the vicinity of which points, on the other hand, the ramp has a second slope which is substantially shallower than the first slope, said points of intersection thus being situated on a slope discontinuity.
Thus, and contrary to known devices in which the variation of slope of the guide cavity intervenes only at a distance from the zone of maximum depth and/or only occurs in a continuous and gradual way from this zone, the device according to the invention enables all mechanical clearances to be adjusted from the beginning of its operation and results in a clamping force which is substantially greater than that allowed by known devices, for the same input force and the same travel.
Further characteristics and advantages of the invention will become clearly apparent from the description given below, by way of example and with no limitation being implied, with reference to the appended drawings, in which:
FIG. 1 is an exploded perspective view of a revolving plate clamping device;
FIG. 2 is a schematic cross-sectional view of a revolving plate, of the corresponding ball, and of a guide cavity having a known contour, in which the ball is housed, the cross section being cut through the longitudinal axis of the cavity;
FIG. 3 superposes onto the contents of FIG. 2 the contour of a guide cavity according to the invention so as to explain the differences between the latter and the prior art.
FIG. 4 is an enlarged and schematic cross-sectional view of a revolving plate, the corresponding ball and a guide cavity according to a first embodiment of the invention, the cross section being cut through the longitudinal axis of the ball; and
FIG. 5 is a view similar to the one in FIG. 4, but relates to a second embodiment of the invention.
FIG. 1 is a schematic representation of a revo
REFERENCES:
patent: 3701400 (1972-10-01), Burnett et al.
patent: 4422600 (1983-12-01), Preston
patent: 4550810 (1985-11-01), Price et al.
patent: 4944372 (1990-07-01), Taig
Mery Jean Claude
Moinard Patrice
Thioux Alain
Bendix Europe Services Techniques
McCormick Jr. Leo H.
Oberleitner Robert J.
Palguta Larry J.
Rutherford Kevin D.
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