Valves and valve actuation – Fluid actuated or retarded – Dashpot or fluid controlled retarder or timer
Reexamination Certificate
1999-09-08
2001-03-20
Shaver, Kevin (Department: 3754)
Valves and valve actuation
Fluid actuated or retarded
Dashpot or fluid controlled retarder or timer
Reexamination Certificate
active
06202979
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a valve that influences flow through a fluid connection and includes a valve member that executes a motion in response to a pressure difference across the valve member and in which the distance between a valve seat and the valve member varies as a function of the pressure difference.
A basic problem with a valve of the type referred to above is that flow or switching noises occur. Quieting channels, which prevent a sudden pressure difference between inflow and outflow sides, have been introduced for damping valves.
In addition, it is known that in damping valves the switching operation is performed only when there is a reduction in pressure below a maximum pressure in the vibration damper, since otherwise switching noises are also noticeable. In this connection, steps have also been undertaken to limit the operating stroke of the valve member, so that no switching noises can occur.
BRIEF SUMMARY OF THE INVENTION
The object of the present invention is to provide a valve that produces the lowest possible shifting noises, has low internal friction, and executes a prescribed operating motion under all operating conditions.
According to the invention, this object is accomplished by damping the movement of the valve member relative to the valve seat. The damping prevents too rapid an opening motion of the valve, which on the one hand may produce flow noises of the flow medium or else switching noises because of the mass of the valve member.
In an advantageous embodiment, the damping means operates speed-dependently. Because of that, a direct dependence exists between the back pressure as an operating force and the countermeasure of the damping means, which likewise operates speed-dependently. Complicated electronics that could provide the same effect are not needed.
For this purpose the speed-dependent damping has a displacer, which is movable in a damping chamber filled with a pressure medium. The same medium that also flows through the valve serves as the pressure medium.
In addition, the damping means has at least one throttle cross section. A plurality of throttle cross sections may alternatively be used, so that a stroke-dependent damping effect becomes possible. In an additional advantageous arrangement, the damping chamber is defined by a cup-shaped housing in which the displacer is received.
The throttle cross section of the damping means is made relatively small. So that the slot between the displacer and the housing exerts no influence on the damping action, the displacer is sealed off from the damping chamber.
In an advantageous arrangement, the valve member is axially movable and is supported by a slide in its operating motion, the slide forming a structural unit with the displacer.
For simplicity of production, the damping chamber has a stepped inner contour, where a longitudinal section of the damping chamber represents a track for the displacer. Hence it is not necessary for the entire inner wall of the damping chamber to be produced with great accuracy.
As an additional measure for influencing the operating motion of the valve member, the damping chamber accommodates a catch arrangement, consisting of catch element and a countercatch element. The catch element is operatively associated with the valve member and defines at least one operating position of the valve member. The catch arrangement may include radially movable supports for a plurality of catch elements that engage in a countercatch element. For simple assembly, the catch elements are parts of a structural unit associated with the slide. In practice, the catch elements are provided on a tubular extension of the slide, the extension having axial slots that permit radial freedom of motion of the catch elements.
In order to define the closing position of the valve, the slide is preloaded by a locking spring arranged within the damping chamber.
To improve guidance of the valve member, the valve member comprises a valve slide which, within the fluid connection, together with a housing of the valve, forms a back-pressure region, the back-pressure region being sealed off by a seal that is radially movable within limits. In order to minimize the problem of friction in connection with the operating motion of the valve member, the seal is held in a groove, the seal being spaced apart from the groove bottom. There is only little preloading of the seal in the back-pressure region. The actual sealing action is produced by the preload of the back pressure.
In order to prevent back pressure upon a travel-in motion of the valve slide, the back-pressure region has a pressure-equalizing connection. To save installation space, the pressure-equalizing connection is arranged in the valve slide.
In addition, the pressure-equalizing space has an additional pressure-equalizing connection, which is controlled by a sealing unit that seals off the housing of the valve, where the housing separates two working spaces from one another and in operation of the valve is moved axially, while the sealing unit has a first outer sealing ring that is designed for low friction and an inner sealing ring that preloads the outer sealing ring radially and, as a function of its position within an annular groove in the housing, controls the additional pressure-equalizing connection.
The back-pressure region has an additional pressure-equalizing connection in the valve slide which, independently of other pressure-equalizing connections, connects the back-pressure region with a working space. Thus, a maximum of three pressure-equalizing connections is available, so that reliable valve slide motion is possible even in the event of malfunction of one of the pressure-equalizing connections.
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Mintgen Rolf
Rennecke Dirk
Wolfgang Rothe
Baker & Botts L.L.P.
Keasel Eric
Shaver Kevin
Stabilus GmbH
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