Pumps – Successive stages
Patent
1991-05-17
1992-11-24
Bertsch, Richard A.
Pumps
Successive stages
417 2, 417 45, F04B 4906, F04B 3714, F04B 4106
Patent
active
051658640
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a vacuum pump unit.
A vacuum pump unit is normally made up of a primary pump sub-assembly and a secondary pump sub-assembly, with the chamber to be evacuated being connected to the suction of the secondary pump sub-assembly.
It is known that the speed of rotation of the motor driving the secondary pump sub-assembly is servo-controlled to the pressure of the chamber to be evacuated, using a gauge to measure the pressure drop. Once the set pressure has been reached, this makes it possible to reduce the speed of the secondary pump and thus reduce wear.
However, vacuum pressure gauges are not very accurate.
The principle of the invention is to act not on the secondary pump sub-assembly but on the primary pump sub-assembly, and above all not to use a vacuum gauge, but to make direct use of the electric current drawn by the drive motor for the secondary pump sub-assembly or else for the primary pump sub-assembly when it is being alone.
Using this idea and depending on the various combinations used, the invention takes on three related forms.
In a first form, the invention provides a vacuum pump unit including a primary pump sub-assembly rotated by an electric motor, the unit being characterised in that it includes an electronic control circuit for controlling the speed of rotation of the motor as a function of the motor current.
In a second form, the invention provides a vacuum pump unit including a secondary pump sub-assembly rotated by an electric motor M2 and applying suction to a chamber to be evacuated, and a primary pump sub-assembly rotated by an electric motor M1 and whose suction is connected to the output of the secondary pump sub-assembly, the unit being characterised in that it includes an electronic control circuit for controlling the speed of rotation of the electric motor M1 as a function of the current drawn by the electric motor M2.
In a third form, the invention provides a vacuum pump unit including a primary pump sub-assembly and a secondary pump sub-assembly rotated by an electric motor M2 and applying suction to a chamber to be evacuated, the unit being characterised in that said primary pump sub-assembly comprises a high flow-rate first pump sub-assembly, rotated by an electric motor M'1 and a low flow-rate second pump sub-assembly rotated by an electric motor M"1 and whose suction is connected to the outlet of the secondary pump sub-assembly and in that an electronic control circuit stops the electric motor M'1 when the current drawn by the motor M2 falls below a pre-determined value.
According to another characteristic, said electronic control circuit additionally controls the speed of rotation of the electric motor M"1 as a function of the current drawn by the motor M2.
The system is simpler, more accurate and cheaper than using a vacuum gauge. Use is made of the current drawn by the drive motor of the secondary pump sub-assembly or else of the primary pump sub-assembly, if being used alone, knowing that said current is a function of the pressure in the chamber to be evacuated.
The invention is now described with reference to the accompanying drawings in which:
FIG. 1 is a diagram showing a vacuum pump unit of the invention including only a primary pump sub-assembly;
FIG. 2 is a diagram showing a vacuum pump unit of the invention and including both a secondary pump sub-assembly and a primary pump sub-assembly; and
FIG. 3 is a diagram showing a vacuum pump unit of the invention in which the primary pump sub-assembly is itself subdivided into two sub-assemblies .
Turning to FIG. 1, a vacuum chamber 1 is shown connected to a primary pump sub-assembly 2, which may include one or more pumps. The primary pump sub-assembly 2 includes its own drive motor(s) M1. A potential V1 is applied to the drive motor(s) M1 by means of a control circuit 3 which receives both an input voltage V from a power supply 4 and a signal representative of the current I1 drawn by the motor M1 as determined by a current measuring circuit 5. The control circuit 3 delivers an output voltag
REFERENCES:
patent: 2936107 (1960-05-01), Blackburn
patent: 4225288 (1980-09-01), Mugele et al.
patent: 4596514 (1986-06-01), Matsumoto et al.
patent: 4655688 (1987-04-01), Bohn et al.
patent: 4699570 (1987-10-01), Bohn
Burger Heinz-Dieter
Handke Klaus
Saulgeot Claude
Alcatel Cit
Bertsch Richard A.
Scheuermann David W.
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