Suction-throttled pump

Pumps – Three or more cylinders arranged in parallel – radial – or... – Radial cylinders

Reexamination Certificate

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Details

C417S295000, C417S441000

Reexamination Certificate

active

06213729

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to a suction-throttled pump comprising at least one displacement body for the delivery of a medium in accordance with the preamble of claim
1
.
Suction-throttled pumps are known. They are used in motor vehicles, for example, and operated at varying speeds. The flow of medium required by the pump consumer is limited. At high pump speeds, the delivery rate of the medium would be too high. Therefore, a throttle valve, also referred to as a suction control valve, is provided in the suction region of the pump, i.e. between the pump and a reservoir or tank, and limits the quantity of medium sucked in. If pumps of this type are used in connection with a liquid medium, for example hydraulic oil, the static pressure in the suction region of the pump can drop below atmospheric pressure, with the result that foam forms. The dynamic properties of the pump are permanently impaired by the foam-containing oil. Furthermore, a pump displacer, which delivers the medium, is not uniformly filled on account of the foam, resulting in a non-uniform delivery rate. Moreover, the operating noises of the pump increase considerably.
SUMMARY OF THE INVENTION
Therefore, the object of the invention is to provide a suction-throttled pump of the aforesaid type which does not have these disadvantages.
A suction-throttled pump with features including at least one displacement body movable in a working chamber for delivery of a fluid medium, a suction chamber, an inflow channel between the delivery chamber and the suction chamber, and a suction control valve for the inflow channel is proposed in order to achieve this object. The pump is characterized in that the suction control valve co-operates directly with an inflow channel opening into a working chamber of a displacement body and extending between a suction chamber and this working chamber. The suction control valve is arranged at the end of the inflow channel facing the suction chamber so that there is only a minimal volume of oil in which the static pressure can drop below atmospheric pressure. Even if foam forms here, the foam quantities are so small that in practice they no longer have a detrimental effect on the dynamic properties, the pumping behavior or the noise generation of the pump.
A preferred embodiment of the pump comprises a plurality of valve bodies each having an inflow channel opening into the suction chamber. The suction control valve is characterized by a valve body associated with all the inflow channels. This produces a very simple pump design with optimum operating behavior.
A further embodiment of the pump is characterized in that the suction control valve is adjustable, consequently, the working rate of the pump is easily controllable.
Another embodiment of the pump comprises a cylinder block in which the displacement body or bodies are arranged. The cylinder block is characterized by a groove having an annular surface into which the inflow channel or channels open. The valve body of the suction control valve co-operates with this annular surface. This produces a very simple, but effective design which is inexpensive to manufacture and is distinguished by the fact that no more than a very small quantity of foam-containing oil is produced.
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.


REFERENCES:
patent: 1694329 (1928-12-01), Le Bus
patent: 2546583 (1951-03-01), Born
patent: 3151569 (1964-10-01), Muller
patent: 3418937 (1968-12-01), Cardillo et al.
patent: 3434428 (1969-03-01), Liles
patent: 3790307 (1974-02-01), Aldinger
patent: 4065229 (1977-12-01), Black
patent: 4094617 (1978-06-01), Shibuya
patent: 4490971 (1985-01-01), Hedelin
patent: 4643639 (1987-02-01), Caine
patent: 5156531 (1992-10-01), Schmid et al.
patent: 5167493 (1992-12-01), Kobari
patent: 5277553 (1994-01-01), Stolpp
patent: 5873706 (1999-02-01), Kawabata
patent: 8614289 (1987-11-01), None
patent: 2207955 (1989-02-01), None
patent: 9102156 (1991-02-01), None

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