Self controlling magnetic valve

Details Self controlling magnetic valve Self controlling magnetic valve

1999-01-11

2001-05-22

Shaver, Kevin (Department: 3754)

Valves and valve actuation

Fluid actuated or retarded

Pilot or servo type motor

C251S030030

Reexamination Certificate

active

06234449

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention has to do with a magnetic valve, in particular a self-controlling magnetic valve, which is actuated by an electromagnetically controlled initial pilot valve for controlling fluids. The valve has a main valve member in the form of a differential piston and the means to suppress pressure surges when the main valve closes. It includes an overflow channel that has a limited flow-through cross section between both sides of the main valve member, and whose cross section increasingly lessens in the final phase of the closing motion.
It has been noticed that cavitation occurs when magnetic valves are closed abruptly, such as in magnetic valves that are used to control water flow in devices like dishwashers and washing machines, particularly those with servocontrol valve functions. This causes noises similar to hammer blows. Additionally, on the inlet side, an impact-like increase in pressure is noted. Efforts have been made to protect against these types of pressure surges by using elastic hoses as inlet and outlet lines. Recently, however, for safety reasons, the magnetic valves in question have been installed directly on the water faucet, and/or linked to the feeding system via lines that are as short as possible and relatively inelastic. For this reason, a proposal has already been made (European Patent No. 0,135,474) to create pressure equalization volumes operating by spring tension, on both the inlet and outlet sides. But such efforts to find a solution are expensive and costly. In addition, with own-medium-controlled magnetic valves, efforts have been made to lessen pressure surges on the inlet and outlet flow sides by giving the overflow channel of the servo valve mechanism a very small cross section, making it possible for the main valve to perform only a delayed closing. However, with this there is a danger that sedimentation and/or dirt particles carried by the controlled fluid will obstruct the channel, and the valve then will no longer be able to close.
Additionally, the German Patent Specification No. 976 465 describes an own-medium-controlled magnetic valve according to the generic name. It has an overflow channel that runs vertically through the main valve member, and its cross section is increasingly reduced during motion achieved by having a housing-stable conical pin project into the overflow channel. However, only a quite gradual cross section reduction of an overflow channel, which is relatively narrow even without this, can be achieved, so that the valve closes only after a time lag. Additionally, there is the danger that lime deposits will make the cross section relationships uncontrollable, and/or lead to abrasion of the overflow channel walls.
The French Patent Specification No. 1,514,837 offers a self-controlling magnetic valve, also generic, with a rubber elastic membrane that comes into contact on the one hand with the main valve seat, and on the other may be supported radially outside the main valve seat by a ring-shaped fold vis-a-vis the overpressure that acts on it from in the inlet side, under control of a ring-shaped member on a stiff plate surface of the main valve member. The ring-shaped member has, bilaterally, a collar of fine radial grooves, through which a pressure equalization is accomplished between the two sides of the main valve member. Although the flow-through cross section of the flow path so created, may be reduced toward the end of the closing motion with increasing contact pressure on the membrane, it cannot go toward zero, so that the closing still ends in with a relatively impact-type motion.
Additionally, the U.S. Pat. No. 2,870,986 offers a magnetic valve that in principle is similar, in which, with increasingly overpressure from the inflow side of the valve, an overflow channel in the main valve member is increasingly restricted in a way that is largely independent of the particular setting of the main valve member, so that the membrane is compressed into an annular groove of a plate-shaped support member. With the “reinforcement member” so created, the valve's flow rate should be stabilized in relation to the pressure that appears.
Here again, as in the other case, a danger exists that the flow-through cross section of the flow path in question can be reduced in the course of time by deposits.
SUMMARY OF THE INVENTION
Proceeding from this state of the art, the invention has the objective of creating a self-controlling magnetic valve.
This takes care to ensure that the closing process takes place while avoiding pressure surges on the inflow and outflow sides, while the valve moves rapidly and with a precision that remains the same over a lengthy period.
The overflow channel reduces in cross-sectional size by means of contact pressure of the main valve member on its valve seat. This reduction ensures that the overflow channel reduces in cross section only in the very last phase of the closing motion, but is reduced all the more emphatically. It should be noted that the valve's flow rate changes in the course of the closing motion with increasing gradients, so that the characteristics of the final phase of the closing motion are of decisive importance. The cross section reduction through the squeezing of the overflow channel that nonetheless depends on the input pressure of the fluid to be regulated, yields, in addition, a control process through which the closing rate of the valve in the critical end phase is largely independent of pressure. However, through mechanical effects of contact pressure by the main valve member on its valve seat, deposits are eliminated as soon as they occur.
In a particularly simple way, the choke channel can be configured in the elastic membrane of the main valve member that is customarily present in such valves. This is done in such a way that it can be squeezed together by contact of the membrane on the valve seat that goes with it. Additionally, measures can be taken to bypass the choke channel in question at the beginning of the closing process, and thus accelerate the closing process.
For a full understanding of the present invention, reference should now be made to the following detailed description of the preferred embodiments of the invention as illustrated in the accompanying drawings.


REFERENCES:
patent: 3593957 (1971-07-01), Dolter et al.
patent: 4387878 (1983-06-01), Zukausky
patent: 4534537 (1985-08-01), Zukausky
patent: 5599003 (1997-02-01), Seeman et al.
patent: 5732929 (1998-03-01), Luppino et al.
patent: 02113187 (1990-04-01), None

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