Fluid handling – Line condition change responsive valves – Bi-directional flow valves
Reexamination Certificate
1999-02-12
2001-02-06
Hepperle, Stephen M. (Department: 3753)
Fluid handling
Line condition change responsive valves
Bi-directional flow valves
C188S299100, C188S322140
Reexamination Certificate
active
06182687
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a pressure-dependent valve for use with a vibration damper having a piston rod axially movably arranged in a fluid-filled cylindrical tube, the pressure-dependent valve being activated by an adjustment device that is pressurized via a pressure connection opening.
2. Description of the Related Art
A prior art pressure-dependent valve for an adjustable vibration damper is disclosed in German reference DE 44 01 393 C1. The adjustable vibration damper includes a piston rod axially movably mounted in a cylindrical tube filled with damping fluid. The cylindrical tube has a connection to the pressure-dependent valve, which is activated by a pressurized adjustment device. The adjustment device has an axially movable valve body that is activated by a pressure transducer, which is float-mounted in a pressure space and supported by at least one spring. The spring that prestresses the pressure transducer determines the steepness of an opening force characteristic curve of the valve in the case of given valve cross-sections. It is disadvantageous in that the prior art uses cup springs which are subject to significant fluctuations with respect to their spring force. The slightest deviations in the dimensions of the cup springs have considerable influence on valve behavior.
Furthermore, the ability to set an operating point at any location on the opening force characteristic curve of the valve is a desired characteristic. However, this is not possible with the prior art valves shown by the reference DE 44 01 393 C1.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a pressure-dependent valve in such a way that it is possible to set a valve opening force characteristic curve and to set an operating point of the valve at any desired point on the force characteristic curve.
According to the invention, this object is met by a pressure-dependent valve having an adjustment device including a valve body and a valve surface that are movable relative to each other for determining a valve cross section. The valve body is connected to a float-mounted pressure transducer and either the valve body or the valve surface is movable relative to the current position of the pressure transducer by the adjustment device. The essential advantage compared with the prior art is that the valve passage cross-section is adjustable independently of the position and prestress of the pressure transducer. In the prior art, a closed stress chain always existed from the pressure transducer to the valve surface. Therefore, in the prior art, increased prestress of the pressure transducer was always associated with a closed valve in the prior art device. When cup springs are used to prestress the transducer, there is frequently a need to readjust the spring prestress force. With the adjustment device of the present invention, the requirement that the valve be closed to increase the spring prestress force of the pressure transducer and the valve passage cross-section is eliminated, so that, at a specific prestress force of the pressure transducer on the valve body, either an open or a closed valve passage cross-section is possible.
With respect to the valve performance characteristics, the adjustment of the spring prestress of the pressure transducer in the present invention permits the production of different force characteristic curves having different slopes, i.e., different force gradients. After the force characteristic curve is set, the adjustment device is used to set an operating point on the force characteristic curves at which, for example, the valve opens.
In one embodiment, the valve body is axially adjustable relative to the pressure transducer by the adjustment device. Alternatively, the valve surface can be adjustable relative to the pressure transducer by the adjustment device. One criterion in deciding for or against one of the two variants may be whether and with what mechanism the valve is adjusted, whereby the component to be adjusted should be as easily accessible as possible.
The adjustment device should, if possible, perform two functions. First, the described movement of the valve body or the valve surface must be ensured. Secondly, holding forces, which counteract operating forces in the valve, must be absorbed. Therefore, in one embodiment, the adjustment device may comprise a threaded joint which may, for example, at least indirectly connect the pressure transducer to the valve body.
In another embodiment, the pressure transducer has a blind hold threaded opening to partially accommodate the valve body. The blind hole threaded opening is part of the adjustment device. This solution is especially suitable when the valve body, for setting purposes, is accessible from the direction of the valve surface. In this embodiment, it is not necessary to seal the valve body relative to the pressure transducer because no passage opening for the valve body exists.
In yet a further embodiment, the pressure transducer has an opening through which an extension of the valve body runs to the side of the pressure transducer facing away from the valve body. In this embodiment, the adjustment device which movably holds the valve body relative to the pressure transducer is arranged between the extension and the pressure transducer. The valve body is thus radially guided especially well. Furthermore, the rear side of the valve body is generally easier to reach when the valve body is pressurized during the setting process, for example, by a pressure medium, and a certain tightness of the measurement device relative to the valve is required. The setting process is especially simple when the extension is arranged centrally relative to the pressure connection opening in a lid of the pressure-dependent valve, so that the extension is accessible through the pressure connection opening.
In all embodiments, it is desirable for the valve part movable by the adjustment device to have at least one tool surface.
However, an embodiment may also be realized in which the valve surface comprises a screw socket inside a pot-shaped piece. The screw socket may be turned as required to change the position of the valve surface.
Even when the threaded joint of the adjustment device comprises an attachment thread, the axial thread clearance must be taken into account because the valve passage cross-sections are quire small and the small axial thread clearance therefore influences the valve passage cross-section. For this reason, the threaded joint has a thread clearance compensation means. Thread clearance compensation may be implemented, for example, by the movable valve part being rolled or welded to a stationary part. However, because the entire valve is very small in structure, such work steps, under some circumstances, may damage the valve.
In a preferred embodiment, the thread clearance compensation means may comprise a prestress spring acting on the valve part movable relative to the pressure transducer so that the same threaded flank sides always lie atop one another. The prestress spring presents a flank change as a result of fluctuating pressures on the valve body due to the thread clearance.
For further precision setting of the valve, the pressure transducer is held bilaterally by spring elements on support surfaces, at least one of which is axially adjustable. As a result, the prestress of the spring elements acting on the pressure transducer is adjustable. Depending on the prestress, it is possible for the resulting spring forces of the springs acting on the pressure transducer to act in the opening or in the closing direction. In addition, an equilibrium of forces can be established. This has proved especially advantageous when flat spring disks are used as the spring element instead of cup springs. The screening influence that exists in the case of cup springs is eliminated.
To permit a simple setting operation, the axially movable support surface comprises a support ring movably mounted in the pressure space. For economical but
Forster Andreas
Kuhnel Joachim
Cohen & Pontani, Lieberman & Pavane
Hepperle Stephen M.
Mannesmann Sachs AG
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