Fluid handling – Systems – Supply and exhaust
Reexamination Certificate
2002-08-06
2004-03-30
Michalsky, Gerald A. (Department: 3753)
Fluid handling
Systems
Supply and exhaust
C137S596160
Reexamination Certificate
active
06712091
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a control device.
BACKGROUND INFORMATION
U.S. Pat. No. 3,714,868 describes a control device that operates on the closed-center principle.
It is an object of the present invention to provide a control device configured to operate on the open-center principle and which substantially avoids leakages. The control device may be constructed in a simple manner, may operate reliably and may be produced without a high outlay in manufacturing terms.
SUMMARY
The above and other beneficial objects of the present invention are achieved by providing a control device as described herein.
In accordance with the present invention, quantity-independent functioning may be ensured. The control device according to the present invention may be used for various applications and may easily be adapted to changed requirements. It may be used, for example, for a hydraulic control motor, e.g., when the activation of the latter functions on the open-center principle.
Example embodiments of the present invention are described herein. However, the present invention is not restricted to the feature combinations described herein but include further appropriate possibilities for the combination of features.
The present invention may allow a modular construction of the, e.g., electrohydraulic control device, so that a large number of parts may be used many times, which may provide considerable advantages with regard to the outlay in terms of manufacturing and assembly terms. By virtue of the simple construction, standard seals may be used, which do not place stringent requirements on the components in terms of tolerances and surface quality. In addition, the use of special materials may be dispensed with, which may be advantageous with regard to heat treatment and surface treatment. At the same time, high flexibility for various applications is preserved. Particularly reliable functioning may be ensured in that no moveable parts are mounted one in the other. When the control device according to the present invention is used for a hydraulic control motor, the latter may be activated on the open-center or closed-center principle.
A control device according to the present invention for a hydraulic control motor has at least one valve which is controlled actively by an actuating force and which has a first piston with stepped diameters, which is mounted axially moveably in a housing and is loaded by a spring and which forms a first pressure space with an, e.g., disk-shaped element having a throttle point. Furthermore, such a control device has at least one passive valve which is operatively connected to the actively controlled valve and which has a second piston with stepped diameters, which is mounted axially moveably in the housing and is loaded by a spring and which forms with the housing a second pressure space. These two pressure spaces are operatively connected via a line, so that the actively controlled valve co-controls the passive valve. The actively controlled valve has an adjustable throttle point which may be regulated actively by a throttle needle. The actuating force which regulates the throttle point may be applied mechanically, electrically, electromagnetically, hydraulically, pneumatically, etc. The pistons have special sealing elements which, in addition to performing their sealing function, also have bearing properties. They may be produced from resistant and low-wear materials, such as, for example, Teflon. Integrated in the piston of the actively controlled valve is at least one bore which serves for the feed of pressure medium into a pressure space which is connected to the passive valve by a line.
An exemplary embodiment of the present invention is described below, in principle, with reference to the FIGURE.
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Werner Goetz: “Hydraulik In Theorie Und Praxis”, Schulung, Stuttgart: Bosch GmbH, DE, 1995, pp. 239-243.
Michalsky Gerald A.
ZF Lenksysteme GmbH
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