Rotary expansible chamber devices – Multistage – Interengaging rotary members
Patent
1993-09-01
1994-10-18
Bertsch, Richard A.
Rotary expansible chamber devices
Multistage
Interengaging rotary members
418 15, 137597, F01C 130
Patent
active
053562755
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a system for supplying inert gas to a multi-stage dry-running vacuum pump with systems for distributing the inert gas to the stages of the pump.
"Dry-running" vacuum pumps are pumps whose chambers contain no lubricant and/or sealing material. Typical pumps of this kind are multi-stage pumps and have rotary pistons of the claw type (Northey profile). Their advantage lies in the fact that they can produce vacuums completely free of hydrocarbons, so that they are used especially for the evacuation of vacuum chambers in which semiconductor processes (etching, coating or other vacuum treatment or manufacturing processes) are performed.
EP-A 365,695 (to which U.S. Pat. No. 5,046,934 corresponds) discloses a multi-stage dry-running vacuum pump of the kind herein concerned. It is provided with an inert gas supply which consists of a nitrogen source, conduit systems leading into the pump chambers, and a valve. In this previously known pump it cannot be determined whether the inert gas supply is functioning properly while the pump is operating. The object of the present invention is therefore to create a system of the kind referred to above, which can be checked during operation. The feeding of inert gas to the pump is intended, among other purposes, to prevent solid particles entering the pump or forming in the pump while the gases are being compressed from depositing themselves on the rotor or on the walls of the pumping chambers. Depending on the nature of the semiconductor process the inert gas requirement will differ not only in regard to the amount needed but also in regard to the point, i.e., the stage, at which the inert gas is needed. It must also be considered that the feeding of inert gas while the pump is running adversely affects the pump's output.
The present invention is therefore addressed to the additional task of creating a system of the kind referred to above by means of which not only can the inert gas feed be monitored, but also the nature of its distribution and its rates of flow can be influenced.
SUMMARY OF THE INVENTION
Due to the independence of the inert gas supply and to its modular construction, it is possible in a simple manner to provide not only for the distribution of the nitrogen supply but also for many different control functions. The most widely different parameters, for example the pressure, the rate of flow to the individual stages, etc., can be controlled in relation to the process. By the replacement or rotation of components it becomes possible to make changes in the control criteria, the rates of flow etc., for the purpose of adaptation to different processes.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic section through a four-stage vacuum pump showing the inert gas source, partially cut away.
FIG. 2 shows an embodiment of the connection of the tubing in the system according to the invention, and
FIG. 3 shows an inert gas supply system differing from that in FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The embodiment represented in FIG. 1 is a four-stage vacuum pump 1 with two shafts 2 and 3 plus four rotor pairs 4 and 5. The rotary pistons are of the claw type and rotate in the pump chambers 6. The latter are formed by the side plates 7 and 8, the middle plates 9 and 10 and the housing rings 11 to 14.
Below the bottom side plate 8 are the shafts 2 and 3 with gears 16 and 17 of equal diameter, which serve for the synchronization of the movements of the rotor pairs 4 and 5. Additional driving means (motor, drive clutch etc. ) are not shown.
The bottom bearing plate 8 is of bipartite construction. It includes the lower plate 21 in which, as also in the upper bearing plate 7, the shafts 2 and 3 are supported on rolling bearings 22. Between the shafts 2 and 3 and the upper plate 23 labyrinth seals 24 are provided.
The inlet of the pump in the upper bearing plate 7 is marked 25, and the discharge of the pump in plate 23 is marked 26.
To be able to feed inert gas to the pump chambers 4 and addi
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Bahnen Rudolf
Brenner Lothar
Bertsch Richard A.
Freay Charles G.
Leybold Aktiengesellschaft
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