Brakes – Wheel – Transversely movable
Patent
1987-06-29
1988-08-23
Kashnikow, Andres
Brakes
Wheel
Transversely movable
74110, F16D 6522
Patent
active
047654473
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a wedge brake activating device for drum brakes of vehicles having a housing which accepts an expanding wedge which can be activated in its longitudinal direction and which protrudes into a recess of the housing, in which two pressure tappets are located at both sides of the expanding wedge in transverse direction to the expanding wedge in the housing, and are axially aligned relative to each other, and activate the brake shoes by means of displacements caused by the expanding wedge between each of the two wedge surfaces and a slant surface of the adjacent push tappet which is parallel to the wedge surface. A cylindrical roller is frictionally connected, guided with its front surfaces on the side surfaces of a slot in the push tappet which forms the slant surfaces of the push tappet. Both rollers are guided in a roller cage which is arranged with longitudinal sliding motion on the expanding wedge and between the side surfaces of the slots. The roller cage is provided with two legs running parallel to the traverse direction, on which guide protrusions are arranged, bent on the inside at right angles, which run in opposite direction in pairs, and which guide the two rollers at diametrically opposite locations tangentially at their extreme outside ends at a distance which is smaller than the diameter of the rollers. An axial guide section is formed on the leg, between the guide protrusions of each protrusion pair, at the same level as the surfaces of the internal walls of the legs, and at the front surface of the roller adjacent to the wedge surface.
In the case of a known wedge brake activating device of this kind (DE-OS No. 32 15 904), the guide protrusions designated there as radial guide sections are arranged and designed in such a way that they closely "hug" the external edges of the rollers, i.e. the rounded circumferential edges between the cylindrical circumferential surfaces of the rollers and their plane front surfaces. This is done in order to guide both rollers axially at their external edges, and in order to prevent slant positioning in the roller cage.
However, by guiding at the external edges of the rollers, neither a satisfactory axial roller guidance nor a sufficient tangential guidance is achieved. In addition, a close fit over the rounded external roller edges is difficult to achieve in terms of manufacturing technology, since the mere metal displacement done within the framework of an additional metal shaping process (by pressing a V-shaped groove into the guide protrusions) does not necessarily provide a concave rounding cavity in the guide protrusions which corresponds exactly to the convex rounded edges of the rollers. The task is even more difficult in view of the fact that there must be a bent on at least one guide protrusion of each guide protrusion pair, in order to prevent the rollers from falling out, i.e. in order to make the distance of the external ends of the guide protrusions smaller than the diameter of the rollers.
While in the case of the known device the above mentioned axial guide sections are provided on the legs of the roller cage--providing axial guidance of the rollers on each side at three locations of their circumference--the axial guidance of the rollers is now "redundantly determined". This "redundant determination" has the consequence that for each roller the mutual distance of the two axial guidance sections and the distance of the interacting guidance protrusion pairs must be coordinated axactly with the length of the rollers, in order to achieve an axial guidance at three locations on each side of the rollers, which is difficult, however, in view of the unavoidable manufacturing tolerances. This coordination of the manufacturing tolerances is also difficult in view of the requirement that the distances between the guidance protrusions (which always form a pair) have to be coordinated with the roller diameter, and the concave rounded cavities on the guidance protrusions have to be coordinated with the external roller edge radius, and t
REFERENCES:
patent: 3326330 (1967-06-01), Holt et al.
patent: 4549442 (1985-10-01), Hans et al.
patent: 4558768 (1985-12-01), Brandenstein et al.
Kashnikow Andres
Le Mark T.
Rockwell-Golde GmbH
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