Pumps – With condition responsive pumped fluid control – Pressure responsive relief or bypass valve
Patent
1994-12-21
1996-09-24
Thorpe, Timothy S.
Pumps
With condition responsive pumped fluid control
Pressure responsive relief or bypass valve
417189, 417 76, F04B 4900
Patent
active
055585035
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/EP93/00958 filed Apr. 20, 1993.
BACKGROUND OF THE INVENTION
The invention relates to a high-pressure cleaning device comprising a high-pressure pump which pumps cleaning liquid out of a suction line into a pressure line leading to a discharge device, a bypass line leading from the pressure line to the suction line, a valve body closing the outlet opening between pressure line and bypass line, an actuating element for the valve body which is movable against the valve body contrary to the action of a spring into a position displacing the valve body into the open position, and an operating cylinder which is divided into two chambers by a piston sealingly displaceable in the cylinder and coupled to the actuating element, one of these chambers being arranged between the outlet opening and the bypass line and the other of these chambers communicating with the pressure line via a control line.
A high-pressure cleaning device of this type is known, for example, from DE-PS 31 24 944. With the control described therein it is possible to open the bypass line such that with a decrease in the cross section of the pressure line some of the liquid conveyed by the high-pressure pump is supplied to the suction side of the pump via the bypass line so that the amount of liquid which exits from the pressure line when this has a reduced outlet cross section is diminished. When the pressure line is closed, the bypass line is completely opened. In order, for this purpose, to be able to open the actuating element contrary to the action of the retaining spring, the pressure in the pressure line and in the control line branching of this line must rise to such an extent that it is above the pressure which occurs during normal operation. Only then can the force of the return spring be overcome and this force cannot be selected to be any less since, otherwise, the bypass line would be opened during normal operation in an undesired manner. A complete release of the bypass line therefore presupposes a pressure in the pressure line which is higher than during normal operation. Such an increase in pressure will put an exceptionally heavy strain on the electromotor of the high-pressure pump, i.e. it is necessary to dimension the electromotor such that it is also suitable for this overpressure operation. This means that the motors are required to be larger and more powerful than would be necessary as such for normal, continuous operation.
SUMMARY OF THE INVENTION
The object of the invention is to improve a high-pressure cleaning device of the generic type such that a comparable functioning can be achieved, whereby the component parts can be dimensioned such that they can already be utilized up to their capacity limits during normal operation.
This object is accomplished in accordance with the invention, for a high-pressure cleaning device of the type described at the outset, in that the control line exits from the pressure line in the region of a cross-sectional constriction thereof.
With this measure it is possible for the pressure in the chamber of the operating cylinder connected to the control line to be below the normal operating pressure in the pressure line during normal operation since a lower static pressure results in the region of the cross-sectional constriction due to the increased flow velocity caused by the constriction and the reduced value of the pressure is transferred via the control line to the chamber connected to it. When the liquid discharge is interrupted, for example when the pressure line is closed, there is no drop in pressure in the region of the cross-sectional constriction, and this increase in the pressure in the chamber connected to the control line leads to a displacement of the actuating element and to an opening of the outlet opening so that, as a result, the liquid conveyed by the pump can circulate via the bypass line.
The essential point in this respect is that the pressure which is necessary to open the outlet opening of the bypass line does not exceed the pressur
REFERENCES:
patent: 2707021 (1955-04-01), Harris
patent: 2721520 (1955-10-01), Termont
patent: 3473480 (1969-10-01), Kollmai
patent: 3754841 (1973-08-01), Grabb et al.
patent: 3882930 (1975-05-01), Schexnayder
patent: 4182354 (1980-01-01), Bergstedt
Eisenmann Wilhelm
Weller Matthias
Alfred Karcher GmbH & Co.
Hoppin Ralph F.
Kim Ted
Lipsitz Barry R.
Thorpe Timothy S.
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