Pumps – Successive stages – Parallel stages to or from single stage
Reexamination Certificate
1998-09-16
2001-03-06
Kamen, Noah P. (Department: 3747)
Pumps
Successive stages
Parallel stages to or from single stage
C418S009000, C418S196000
Reexamination Certificate
active
06196810
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multistage vacuum pump assembly.
2. Description of the Prior Art
JP 07(1995)-305689 shows a conventional multistage vacuum pump assembly. Each pump stage is a single pump which comprises a housing which comprises an inlet, an outlet, a pump room and a rotor unit rotatably located in the pump room. Rotation of the rotor unit causes a fluid to be moved from the inlet to the outlet. For example, air in the inlet is sucked to the outlet. Plural pump stages are fluidically connected to each other in series via at least one tube. An inlet of the pump assembly at the upstream end of the series is connected to a room to be evacuated and an outlet of the pump at the downstream end of the series is connected to the atmosphere.
Since the pump stages are connected in series and all have the same performance characteristics, the total vacuum performance of the multistage vacuum pump assembly can be increased only by increasing the rate of rotation of the rotor unit of the pump stages. However the maximum rate of rotation is limited, and an expected total vacuum performance might not be achievable. Even if the expected performance can be achieved by operating the rotor units at high speeds, the life of the multistage vacuum pump assembly might be shortened due to the high speed operation.
SUMMARY OF THE INVENTION
It is an object of the invention to achieve a high vacuum performance expected of a multistage vacuum pump assembly with no shortening of its lifetime.
In order to achieve the object, a multistage pump assembly comprises a plurality of pumping stages connected in series, with the first of the pumping stages being connected to a room or chamber to be evacuated and the last in the series being connected to ambient pressure, characterized in that at least the first of the pumping stages comprises two or more pumps connected in parallel. The evacuation flow through each of the pumps arranged in parallel is reduced according to the invention, so that they do not have to rotate at such high rates of rotation. As a result, the multistage vacuum pump assembly of the invention has a high and sufficient vacuum capacity without shortening the lifetime of the pump.
Preferably, each of the two or more pumps connected in parallel has the same evacuation flow. That is, the size or dimension of the different pumps used in the various pump stages can be identical, and the multistage vacuum pump assembly is easily assembled and is compact.
Furthermore, each of the pumps connected in parallel to form the first pump stage is interconnected to be driven at the same rate of rotation. Therefore, the load of the driving source, such as an electric motor, can be small, so that the consumption of electricity is also small.
Preferably the number of pumps in parallel in any given pumping stage decreases generally from the first to the last of the pumping stages.
REFERENCES:
patent: 2812715 (1957-11-01), Redding et al.
patent: 3089638 (1963-05-01), Rose
patent: 4859158 (1989-08-01), Weinbrecht
patent: 5288217 (1994-02-01), Contiero
patent: 0723080 A1 (1996-07-01), None
patent: 1102967 (1968-02-01), None
Naito Yoshihiro
Taniguchi Hiroya
Aisin Seiki Kabushiki Kaisha
Gimie Mahmoud M
Kamen Noah P.
Reed Smith Hazel & Thomas LLP
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