Fluid handling – Line condition change responsive valves – With separate connected fluid reactor surface
Patent
1988-07-12
1990-04-10
Hepperle, Stephen M.
Fluid handling
Line condition change responsive valves
With separate connected fluid reactor surface
251 50, F16K 3114, F16K 3138
Patent
active
049151266
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for changing the pressure in pneumatic or hydraulic systems, and more specifically, although not exclusively, for changing the pressure in compressed-air diaphragm pumps of the kind set forth in the pre-characterizing clause of claim 1. The invention also relates to an arrangement for carrying out the aforesaid method and being of the kind set forth in the precharacterizing clause of the independent apparatus claim.
The invention is particularly intended to provide a method and an arrangement which will overcome the drawbacks which occur when a medium under pressure, or pressurized medium, is supplied abruptly to a machine or like apparatus with which full pressure is not to be applied immediately. When the inlet valve for delivering such flowing pressurized media is opened, the sudden rise in pressure can result in a shock impact capable of damaging the machine and the equipment peripheral thereto. In hydraulic systems this shock impart is referred to as water hammer and in pneumatic systems as compressed-air shock. The invention, however, is not restricted to the protection of a downstream machine, but can also be applied when emptying or ventilating a pressurized system.
With regard to pneumatic systems reference is made to avoiding ventilating the system too rapidly.
Pneumatic systems can be divided into a number of categories, in which particular distinction is made between static and dynamic systems. The static systems comprise, inter alia, various cylinder arrangements, whereas the dynamic systems comprise air consuming machines, such as rotating or reciprocating machines, for example compressed-air diaphragm pumps. In the case of the static pneumatic systems, valves are commercially available which function satisfactorily, insofar as a pre-determined pressure is initially built-up in the system and the inlet valve is opened fully when the pistons of respective piston-cylinder devices or like devices occupy their dead-centre positions. This avoids jerkiness and impacts in the system.
These known valves, however, do not function satisfactorily in air consuming machines, such as pumps for instance, in which it is not possible to create a pressure build-up before full pressure working conditions are permitted, since the machine will begin to operate as soon as the air under pressure passes through the inlet delivery valve and enters the machine. This applies particularly to compressed-air diaphragm pumps. Such pumps have a variable capacity and will work smoothly from a zero capacity to a 100% capacity in dependence on the volume of air delivered thereto and on the air pressure. Consequently, if an attempt is made to build-up pressure slowly in the pump, the pump will merely operate at a slow pace, without any increase in pressure.
In addition to a closing valve, the delivery pipe, or inlet pipe, of an air consuming machine will often incorporate a pressure regulator for lowering the pressure off the mains to a desired low working pressure, or secondary pressure, and for maintaining this secondary pressure at a constant level. One known pressure regulator of this kind incorporates a delivery channel in which there is embodied a seat valve having a valve spindle which is connected to a diaphragm. A chamber on one side of the diaphragm communicates, via a hole, with the outlet side of the regulator. The other side of the diaphragm is spring biased. The bias asserted by the spring is adjusted by means of a setting knob or wheel, and therewith also the pressure desired on the outlet side of the regulator. A valve of this kind, however, can only be used to create a constant maximum pressure and cannot be used for supplying air to the machine while slowly increasing the supply of pressure.
EP 0126291 describes and illustrates a spring-biassed double-acting piston. Both sides of the piston are connected to the inlet through control valves. Furthermore, the chambers defined on respective sides of the piston can be ventilated to atmosphere through pipelines which incorp
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patent: 4549571 (1985-10-01), Kelly
Burns Robert E.
Dominator Maskin AB
Hepperle Stephen M.
Lobato Emmanuel J.
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