Radial piston pump

Details Radial piston pump Radial piston pump

1992-07-06

1994-03-22

Bertsch, Richard A.

Pumps

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

Radial cylinders

417462, 91491, 92 72, F07B 104

Patent

active

052957977

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

This invention is concerned with a suction-restricted piston pump, in particular, a radial piston pump. Piston pumps are frequently actuated by varying speed drive units, such as internal combustion engines. However, the required flow rate, frequently, is available at a low drive speed, and does not increase with a rising drive speed.
To adapt the supply characteristic to this requirement, DE-AS 20 61 960 describes a radial piston pump having cylinders radially disposed in a housing approximately lying within a plane, and spring-loaded pistons actuated by an eccentric, wherein the pumped fluid is drawn in through grooves disposed circumferentially of the eccentric. The fluid is pumped through hollow pistons and through at least one check valve in the housing. The pistons are configured as throttles in that a restriction plate is respectively provided between a shoulder in the eccentric-sided end of the pistons and the restoring springs. This configuration insures that, with a rising speed, an increasing resistance is created on the pump fluid on the suction side so that the volumetric delivery, after the pump reaches a predetermined speed, no longer rises linearly with speed but rather reaches a maximum value which is almost independent of further pump speed increases.
Hydraulic oils are only slightly compressible. The pressures developing during movement of the piston can, therefore, become very high, resulting in overloading of the pump, or causing the pump to be stalled.
To overcome this problem, control slots have been provided both on the intake side and on the pressure side, which extend over a major area along the direction of movement of the piston bore to thereby steady both the suction and the pumping operation. Pumps of this type, generally, are satisfactory in operation.
However, substantial problems will arise once it is attempted to have such pumps provided with control slots employed in suction-restricted operations. As long as the operation is still in a low speed range, the cylinders are completely filled with pressure fluid, as in pumps with no suction-restricted operation, and hence, a pump of this type operates as a pump with no suction restriction. However, once a critical speed is exceeded, the respective pumping chambers, during the suction process, no longer are completely filled with hydraulic fluid so that a very low pressure or vacuum prevails within the pressure chamber upon commencement of the compression operation of the piston. If a vacuum forming pumping chamber of this type has access to the pressure of the pressure-sided control slot under the output pressure of the pump, the pumping chamber is abruptly filled with pressure fluid which, in the continued rotary movement of the pumping chamber, is compressed in the usual manner and prior to reaching the end of the pressure-sided control slot, is again forced out by the piston.
The operations described hereinbefore result in substantial noise, which is very disadvantageous, especially so if the working environment of the pump is quiet. This applies, for example, to modern automotive vehicles increasing levels of noise suppression. Incidentally, the movement of the pressure fluid from the pressure channel, through the pressure-sided control slot, into the pumping chamber and back involves a substantial loss in output, thereby unnecessarily loading the drive unit of the pump.
The afore-described operations, in analogy, also apply, in modified form, to the suction side so that also in this respect measures will have to be taken to insure a noise reduction and to reduce losses in output. However, in this respect, it will have to be noted that the vacuum in the pumping chamber developing on the suction side can be more easily controlled than the incompressible hydraulic fluid on the pressure side. It is, therefore, quite possible, by reducing the length of the suction-sided slot, to attain a throttling effect, thus foregoing the provision of a separate throttle, thereby insuring an enhanced output and

REFERENCES:
patent: 2371078 (1945-03-01), Summers
patent: 2529309 (1950-11-01), Purcell
patent: 3961558 (1976-06-01), Dokukin et al.
patent: 4605359 (1986-08-01), Suzuki et al.
patent: 5049039 (1991-09-01), Knoth et al.

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