Radial piston pump

Details Radial piston pump Radial piston pump

1998-03-16

2000-02-29

Jeffery, John A.

Pumps

Three or more cylinders arranged in parallel, radial, or...

Radial cylinders

417216, 417270, 417273, 417521, 417523, 417540, 91481, 91490, 91492, 91493, 91497, 92 121, 92121, 418 37, 418138, 418144, 418186, F04B 104

Patent

active

060301856

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention relates to a pump including at least two pump pistons with an associated working chamber each, the working chambers being connected to suction lines by way of suction valve devices and to a joint pressure line by way of pressure valve devices.
German patent application No. 35 10 633, for example, discloses a pump of this type. This publication shows a piston pump having several cylinder-and-piston assemblies, one of which is intended to provide the suction lines of the other cylinder-and-piston assemblies with pressurized fluid. The suction valve devices of the individual cylinder-and-piston assemblies include preloaded non-return valves which will not open until a minimum pressure prevails in the suction line. In the absence of this minimum pressure, the piston cannot aspirate pressure fluid and remains in its inactive position, i.e., it does not abut on the eccentric driving it.
A disadvantage of the prior art piston pump is that it requires a pilot pressure on the suction side, to what end at least one further cylinder-and-piston assembly is required. The maximum volume flow of the pump is limited by the rate of delivery of the cylinder-and-piston assembly.
An object of the present invention is to provide a pump which is in a position to supply a great volume flow and to temporarily deactivate one or more of its cylinder-and-piston assemblies, in response to requirements.


SUMMARY OF THE INVENTION

This object is achieved, according to the present invention, in that at least two of the suction valve devices open in dependence on the pressure in the pressure line. Therefore, no pilot pressure is required in the suction lines, i.e., none of the pistons has to be employed as a backing pump, and the volume flow is not limited by the delivery rate of a backing pump. Opening of the suction valve device corresponds to the neutral position of the associated piston, i.e., a smaller volume flow and a lower power consumption of the pump. As long as the consumer has a high volume requirement, the pressure in the pressure line is low, and the suction valve device remains closed during the pressure stroke. When the pressure in the pressure line exceeds a defined switching pressure, the suction valve device will open also during the pressure stroke, and the pressure fluid can be returned almost unpressurized from the working chamber into the suction line. Only friction losses will occur, the power consumption of the pump is low. The arrangement of the present invention can be used especially favorably in radial piston pumps having pistons which are coupled to the eccentric and, therefore, cannot remain immovable in an inactive position as is possible in the pump known from prior art.
Favorably, the suction valve device is opened by compulsory control. This opening can be effected by an electromagnetically operable valve, for example, which is actuated by appropriate pressure-sensing and controlling devices. Favorably, it is also possible to perform the mentioned compulsory control hydraulically. To this end, an actuating member may be provided which can be acted upon by the pressure in the pressure line, on the one hand, and can act on a closure member of the suction valve device in the opening direction, on the other hand.
According to the present invention, a closure member of this type is coupled to a control piston which is connected to the pressure line, on the one hand, and to the suction line, on the other hand. In this case, the suction line acts as a damping chamber to smoothen pressure pulsations which occur in the pressure line.
When several suction valve devices are opened in response to the pressure in the pressure line, and the switching pressure values have a different magnitude, the associated pump pistons can be deactivated one after the other. To this effect, the switching pressures are graded, for example, equidistantly or in any other grading which is conformed to the volume flow requirement or the pressure requirement of the consumer. This permit

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