Brakes – Wheel – Axially movable brake element or housing therefor
Reexamination Certificate
1999-11-24
2001-06-26
Oberleitner, Robert J. (Department: 3613)
Brakes
Wheel
Axially movable brake element or housing therefor
C188S203000, C188S1960BA, C091S173000, C267S136000
Reexamination Certificate
active
06250435
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is directed to an actuation device for machine elements exhibiting wear-induced play, especially for brakes in rail vehicles, with a piston-cylinder unit which generates an actuation force and which has a piston rod which cooperates with a readjusting device which compensates for play caused by wear.
2. Description of the Related Art
In the present application, machine elements exhibiting wear-induced play are considered to be machine elements such as clutches or brakes. Machine elements of this type are used particularly for transmitting driving and braking forces in rail vehicles. To interrupt and close the flow of force, facings are used which withstand high thermal stresses on the one hand and enable a favorable progression of the force flow on the other hand. These facings are exposed to wear which causes a gradually increasing play. Readjusting devices are known for compensating this wear-induced play.
For example, a prior art actuation device is disclosed by European reference EP 0 174 690 having an adjusting nut/spindle assembly as a readjusting device for brakes. This prior art readjusting device is based on a control sleeve under a spring force. A first clutch operated by the spring force prevents an adjusting nut from rotating and causing a longitudinal adjustment of the piston spindle by a rotating movement. After traversing a predetermined play path, the first clutch is released by the displacement of the piston rod beyond a determined path, so that the adjustment of the play path can be increased corresponding to the wear that has occurred on the facing. Another forward feed movement of the piston results in the engagement of a second clutch, whereupon the adjustment of the adjusting nut on the spindle is stopped. This known complicated mechanism for engaging and disengaging the adjusting nut is costly to manufacture because of both a large number of parts and a long and intricate assembly procedure. The structural component parts, especially the clutch, which are highly stressed mechanically through friction have a strong tendency to wear.
Another prior art readjusting device is disclosed in German reference DE-OS 22 01 082, in which the above-mentioned type of readjusting mechanism is used for rail vehicle brakes in connection with a piston-cylinder unit for brake actuation.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a simple to operate, low-wear readjustment actuation device, especially for brakes in rail vehicles, for readjustment of play caused by wear.
This object is met according to the invention by an actuation device for operating a machine element exhibiting wear induced play, comprising an actuating piston-cylinder unit operative for generating an actuation force and having an actuating piston rod, a readjusting device comprising a hydraulic pressure space and a hydraulic readjusting piston-cylinder unit having an adjusting piston for communicating the actuation force of the actuating piston-cylinder unit to the machine element to be actuated, the adjusting piston being extendable for compensating for the wear-induced play, a sensor element operatively connected for detecting an amount of wear-induced play, and a valve element connected between the hydraulic pressure space and the readjusting piston-cylinder unit for admitting hydraulic medium into the readjusting piston-cylinder unit from the hydraulic pressure space via an operating pressure of the actuating piston-cylinder unit when the valve is open for extending said adjusting piston, the valve operatively connected to the sensor element for opening when the amount of wear-induced play exceeds a threshold limit.
The invention includes the technical teaching that for compensating for wear-induced play the readjusting device comprises of a hydraulic piston-cylinder unit which carries out the wear-induced play readjustment through the extension of an adjusting piston. To actuate the adjusting piston, a sensor element detects the wear-induced play. When a threshold wear-induced play is reached, the sensor element opens a valve which admits hydraulic fluid to the readjusting piston-cylinder unit by utilizing the operating pressure of the piston-cylinder unit which generates the actuation force, thereby extending the adjusting piston.
Accordingly, the compensation of wear-induced play is performed according to the invention by a series connection of two piston-cylinder units. The first piston-cylinder unit generates the actuation force—for example, for the brake—and the second piston-cylinder unit generates the readjusting movement which compensates for the wear-induced play. Aside from a minimal expenditure on structural component parts and a compact structural form, the advantage of this arrangement consists in that friction-induced wear of the actuation device itself is minimized. The piston-cylinder unit of the readjusting device is operated hydraulically to form a rigid, incompressible system by the fluid column which is enclosed in this way. However, the piston-cylinder unit generating actuation force may be operated hydraulically or pneumatically. In the specific case when the actuation device is used for brakes in rail vehicles, the piston-cylinder unit generating actuation force is operated pneumatically. The two piston-cylinder units are advantageously separated by a pressure medium converter. The pressure medium converter preferably comprises a dish-like housing with an open side closed by a diaphragm to form a hydraulic pressure chamber. The side of the diaphragm remote of the hydraulic pressure chamber adjoins a pneumatic pressure chamber of the piston-cylinder unit which generates an actuation force.
The sensor element which detects the wear play may be constructed in two preferred embodiment forms. First, the sensor element may be a mechanical stop which cooperates with the valve by way of an actuating tappet. Second, the sensor element may also be constructed as an electric pressure sensor which cooperates with an electromagnetic valve via an electronic unit.
The piston-cylinder unit generating actuation force is preferably constructed as a single-acting, spring-reset pressure medium cylinder. A spring which assists the readjustment is arranged inside of the hydraulic piston-cylinder unit.
To aid in space-saving for the arrangement, the pneumatic pressure chamber and the hydraulic pressure chamber are both arranged in the interior of a hollow piston of the piston-cylinder unit generating actuation force. The pneumatic pressure chamber communicates with a cylinder space of the piston-cylinder unit generating actuation force.
For resetting the readjusting device—for example, to restore brake facings—a manually actuated return-flow valve may be provided, so that the hydraulic fluid located in the cylinder space can be returned to the hydraulic pressure chamber.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention.
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patent: 4088205 (1978-05-01), Frania et al.
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patent: 4635762 (1987-01-01), Nilsson et al.
patent: 4802559 (1989-02-01), Fourie et al.
Dellmann Torsten
Heymer Arne
Kemner Axel
Neumann Harald
Cohen & Pontani, Lieberman & Pavane
Mannesmann AG
Oberleitner Robert J.
Sy Mariano
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