Pumps – With condition responsive pumped fluid control – Expansible chamber pump distributor operation modified
Patent
1991-03-25
1993-03-02
Bertsch, Richard A.
Pumps
With condition responsive pumped fluid control
Expansible chamber pump distributor operation modified
417298, F04B 4904, F04B 4906
Patent
active
051904462
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a method for electrically controlling the actuation of a reciprocating fluid (i.e. gas or liquid) pump, preferably a pump with static pumping chambers and more preferably a multi-piston fluid pump. The invention also extends to an electrically selectable hydraulic poppet valve for employment in the method.
Reciprocating multi-chamber fluid pumps are well known and generally comprise a plurality of static pumping chambers each equipped with a poppet valve to control inlet of fluid into the chamber (on an inlet stroke) for subsequent pressurisation therein on a discharge stroke. Common embodiments of reciprocating multi-chamber pump have a plurality of piston-in-cylinder modules disposed about an annular lobed cam, eccentric or swash plate, carried by a drive shaft. As the drive shaft is rotated to cause rotation of the lobed cam or eccentric, the piston-in-cylinder modules are sequentially operated to cause hydraulic fluid to be pumped from a low-pressure inlet manifold through the poppet valve in each module to a high-pressure delivery manifold. By enabling or disabling one or more of the pumping chambers (or modules), variable stepped changes in the displacement of the pump can be achieved.
One previously proposed method of disabling a piston-in-cylinder module is to hold open mechanically the inlet valve to the cylinder of the module so that the fluid drawn into the cylinder on the inlet stroke is pumped back into the low-pressure inlet manifold throughout the delivery stroke rather than to the high-pressure delivery side of the pump. In this way, for example, a pump having "n" cylinders and means to independently enable or disable each of the piston and cylinder modules, could offer "n" stepped levels of displacement. It will be appreciated that with such an arrangement, the variations in displacement are fixed depending simply on the number of piston and cylinder modules which are utilised at any one time.
Such previously proposed mechanical arrangements have significant disadvantages in that they have proved to be relatively slow and noisy in operation as well as being limited in the degree of displacement variation which can be achieved.
One aim of the present invention is to obviate or mitigate the aforesaid disadvantages. A further aim is to provide a method for the real time control of the displacement of a multi-chamber reciprocating fluid pump having individually electrically controllable poppet valves serving as inlet valves to at least some of the pumping chambers.
SUMMARY OF THE INVENTION
According to one aspect of the present invention a method of controlling the displacement of a reciprocating fluid pump having a plurality of pumping chambers each of which has an inlet valve with a valve member movable to an open limit condition to admit low pressure fluid to the chamber on an inlet stroke of the pump, and movable to a closed limit condition to prevent fluid again flowing past the valve member and to be ejected at high pressure from the chamber on a discharge stroke of the pump, and electromagnetic means to control the movement of the valve members between limit conditions, is characterised in that each valve member is a poppet valve and in that the electromagnetic mens comprises a solenoid coil fixedly mounted in a casing of the valve and a magnet on the valve member, coacting with the coil to move the valve into at least one of its limit conditions on electrical energisation of the coil.
Preferably each pumping chamber is a piston-in-cylinder module and the permanent magnet is annular and surrounds a stem of the poppet valve.
Conveniently, electrical energisation of the solenoid coil is controlled by a microprocessor unit in response to at least one of output pressure of fluid and output displacement volume of fluid leaving the pump. Energisation of the solenoid coil can be used to move the valve member to its closed limit condition, de-energisation allowing the valve member to move under the influence of fluid flow-induced forces
REFERENCES:
patent: 2431769 (1947-12-01), Parker
patent: 2785638 (1957-03-01), Moller
patent: 3529806 (1967-09-01), Kozel
patent: 4241714 (1980-12-01), Knape et al.
patent: 4825904 (1989-05-01), Grau et al.
Rampen William H. S.
Salter Stephen H.
Basichas Alfred
Bertsch Richard A.
The University Court of the University of Edinburgh
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