Seat valve

Details Seat valve Seat valve

1999-04-29

2001-05-29

Hepperle, Stephen M. (Department: 3753)

Fluid handling

Line condition change responsive valves

With separate connected fluid reactor surface

C137S554000, C137S557000

Reexamination Certificate

active

06237624

ABSTRACT:

The present invention relates to a seat valve.
Pressure regulating- or pressure-reducing valves according to DE-A-296 15 498 allow carrying out a sensitive pressure regulation independent from pressure fluctuations of the unregulated pressure, since the control piston adjusting the closure member in relation to the valve seat exclusively is displaced by the regulated pressure counter to the regulating force, which force is determining the value of the pressure being regulated. The regulating force can be generated e.g. by a regulating spring, the spring load of which can be varied in order to vary the regulated pressure, or by means of a proportional solenoid acting as a magnetic spring and generating the respective regulating force depending on the current supplied. Such seat valves are used in high-pressure hydraulic applications if in addition to the pressure regulation the requirement of a leakage-free function has to be fulfilled, since seat valves in comparison to valves containing sliding closure members are reliably leakage-proof in their blocking position. A surveillance of the regulated pressure as needed in different application cases could generally e.g. be realized by means of a pressure switch directly exposed to the regulated pressure, the switching point of which pressure switch then has to be adjusted to the respective selected value of the regulated pressure. Since, however, any near adjustment of the regulating force is changing the value of the regulated pressure, then also the pressure switch would have to be readjusted accordingly. As a consequence, there is demand for a leakage-proof pressure regulating valve having a structurally simple pressure-surveillance function which does not need a readjustment in case of a variation of the regulating force.
In a pneumatic pressure reducing valve as known from JP 61235154/63089908 the opening movement of the piston-like valve closure member in relation to its valve seat is controlled by a diaphragm on which in opening direction of the valve an adjustable regulating spring and counter to the regulating spring the regulated pressure is acting. Movements of the diaphragm are transmitted to the valve closure member by a rod being coupled with the valve closure member. The top end of said rod is cooperating with a relief aperture in the diaphragm as a relief valve which is opened by said diaphragm in case of an unintended increase of the regulated pressure in order to readjust the regulated pressure to the pressure value as determined by the regulating spring. The lower end of said rod is cooperating contactlessly with a switch (proximity detector switch). A signal is generated as soon as the valve closure member is contacting the valve seat. Said signal is confirming that the regulated pressure has reached the adjusted value.
Further prior art is contained in WO 87 011871 and DE-A-1 08 080.
DE-A-42 37 901 discloses a pressure-reducing valve having an integrated pressure switch. Said pressure reducing-valve contains a control piston directly carrying out the pressure regulating function like a slider piston. With a control piston without seat valve function in operation and in the closed position, particularly in case of high system pressures, leakage, e.g. into the return system, cannot be avoided, so that such pressure reducing valves cannot be used in application cases where a leakage-free blocking position of the valve is needed.
In a pilot controlled pressure reducing valve as known from DE-A-32 04 455 the pilot valve contains a piston slider causing leakage which. Only in case of an emergency situation (breakage of the spring, failure of the solenoid), said piston slider is acting like a seat valve element and then actuates an electric switch depending on its emergency sliding stroke.
It is an object of the invention to provide a seat valve of the kind as disclosed apt to allow in a structurally simple fashion a reliable pressure surveillance which is uniform within the adjustment range of the seat valve and does not need to be readjusted in case of a variation of the regulating force.
Said object can be achieved by the following described features of.
In said seat valve comprising the control piston which is actuated by the regulated pressure counter to the regulating force, for the pressure surveillance the fact is used that the position of the control piston is representing the regulated pressure exactly and independent from the adjusted regulating force, as soon as the respective adjusted value of the regulated pressure is reached so that the position detector actuated by the control piston provides constantly a precise information to the regulated pressure within the entire adjustment range. Depending on the prior adjustment of the switching point of the position detector, said information confirms whether the adjusted value of the regulated pressure has been reached, or has been exceeded, or has not been reached or whether the pressure has dropped below said value. A reliable, readjustment-free pressure surveillance is achieved in combination with the advantage of the leakage-proofness of the valve function. Said combination is very advantageous for many application cases for which the leakage-proofness and a simple and reliable pressure surveillance are needed. It is not necessary to interfere for the pressure surveillance in the working flow path or to survey the position of the valve closure member, but the interference for the pressure surveillance is carried out at an optimum location at the control piston itself. However, it ought to be assured that the regulated pressure downstream of the seat valve cannot be raised by external influences.
In a structurally simple fashion in one embodiment an electrical switch is actuated by means of the control piston which switch e.g. is informing that the regulated pressure has been reached. A microswitch has the advantage of a very small actuation stroke and a precise switching point which can be adjusted exactly to the value of the regulated pressure or a pressure value which constantly is proportional to the regulated pressure, respectively. The position detector also can be constituted by a proximity switch, a Reed-switch or a capacatively operating switch. The position detector simply is provided in or at the housing in a pressureless zone, i.e. outside of the flow path, so that no complicated sealing measures are needed and the position detector does not need to be designed pressure safe.
In a further embodiment a correct guiding of the control piston is achieved together with the advantage of a reference position at an end stop. The position or the stroke, respectively, of the control piston is transmitted by a mechanical coupling towards the position detector. The position detector could instead also be provided directly at the control piston.
Expediently the regulating force either is generated by at least one regulating spring or by a proportional solenoid. Instead a Piezo-element or a step motor could be used.
In order to avoid disturbing forces when transmitting the regulating force onto the control piston said control position can be actuated by the regulating force via a regulating force counter support disc simultaneously serving as a drive element of the mechanical coupling for the position detector. This is advantageous in terms of manufacturing, since among others the control piston does not need any modifications.
A compact structure can be achieved with a plunger actuating the position detector and being guided in its movement parallel to the movement of the control piston.
For the manufacturing it is useful to transmit, in both stroke directions and substantially without any lack, the movements of the control piston onto the plunger by means of the coupling element and the engagement part.
For easy manufacture the plunger can be guided simply in a housing bore leading towards the position detector. The adjustability of the position detector allows to precisely adjust the switching point.
In a further embodiment the position detector and the

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