Valves and valve actuation – Fluid actuated or retarded – Piston type expansible chamber reciprocating valve actuator
Patent
1996-08-27
1998-05-26
Lee, Kevin
Valves and valve actuation
Fluid actuated or retarded
Piston type expansible chamber reciprocating valve actuator
251 14, 251 60, F16K 31143
Patent
active
057554242
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a valve which includes a piston whose upper surface is normally acted upon intermittently by a medium, for instance air, for the purpose of controlling vertical movement of the piston, wherein the piston is connected by connecting means to a needle valve which can coact with a valve seating and which communicates with the inlet of a liquid supply line which delivers liquid to the needle valve via a high-pressure pump, wherein the liquid leaves the needle valve through a nozzle orifice and wherein means are provided for blocking said orifice.
A valve of this kind is normally referred to as a high-pressure valve and is used for so-called water-jet cutting of materials, for instance, wherein a liquid, normally water, is delivered from a reservoir to a high-pressure pump which builds-up a liquid pressure of 3,000-4,000 bars, whereafter the highly pressurized liquid is released to a delivery line whose outlet end discharges into a valve of the aforedescribed kind. This high-pressure jet is released through a nozzle for the purpose of performing cutting work. As before mentioned, a processor-controlled medium is caused to act upon the upper surface of the piston in a predetermined manner, and the needle valve moves in accordance with the piston movement. A high pressure on the upper side of the piston will bring the needle valve into sealing abutment with a valve seat, whereas the pressure acting on the needle valve will cause the needle to leave the valve seat when the pressure on the piston is reduced.
High-pressure working processes of this kind require continuous system maintenance, among other things. It is necessary to undertake different servicing procedures while the system is in operation. A usual procedure in the maintenance routine involves the replacement of worn nozzles. In other instances, it may be necessary to exchange a nozzle in order to carry out a different kind of work.
In cases such as these it is, of course, extremely important from a safety aspect that the valve is unable to release the pressure that prevails in the valve. It is therefore necessary to know for certain that the needle valve is in full sealing abutment with its valve seat.
In this regard, there are safety regulations which state that the valve shall be blocked against unintentional opening of the valve. It is known to protect such systems against unintentional opening of the valve with the aid of a mechanical liquid flow closure device fitted to the delivery line extending from the high pressure pump. This closure device is thus fitted outside the valve arrangement. In view of the fact that a water-jet cutting system will typically include from four to ten valves, it will be apparent that system; expensive; and that
Despite the safety precautions taken in such systems, the workmen involved still remain uneasy as to whether or not the pressure that has already been built-up in the valve and which remains latent even when the aforesaid mechanical closure device has been activated will be caused to be discharged through the nozzle as a result of some other technical fault. One possible fault in this regard is a short breakdown in electrical supply or a short drop in voltage, causing the medium acting on the upper side of the piston, via a pump or compressor, to decrease abruptly and instantaneously, thereby enabling the needle valve to be activated in a valve opening direction and therewith subject workmen and personnel to the effect of the high-pressure liquid and the consequences that follow. The high-pressure pump should not be stopped, for different reasons.
The present invention has evolved against this background, and the object of the invention is to provide means which will fully prevent unintentional release of the high pressure prevailing in the valve.
DESCRIPTION OF THE BACKGROUND ART
Water-jet cutting under the aforementioned high pressures is a relatively young technique. The inventor of the inventive valve has had long experience in this technique, but has been unable to find a
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patent: 4617992 (1986-10-01), Abel
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patent: 4898210 (1990-02-01), Nitta
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