Pumps – Motor driven – Electric or magnetic motor
Patent
1997-12-17
1999-05-18
Freay, Charles G.
Pumps
Motor driven
Electric or magnetic motor
417360, 417418, 418 70, 418206, F04B17/00
Patent
active
059044730
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a vacuum pump having a pair of displacement rotors which rotate inside an axial-flow pump chamber and intermesh in particular in a helical manner. Each rotor is carried by one shaft and associated bearing, mounted on the pressure side, of which each shaft is connected to the armature of a motor arranged outside the housing forming the pump chamber.
This type of construction has the advantage that all members concerning the bearing arrangement and the drive of the rotors are arranged on the pressure side and gas emissions originating from them cannot pass so easily to the suction side of the pump. Expensive seals consequently become unnecessary. However, known pumps of this type (EP-A 472933=U.S. Pat. No. 5,197,861 and U.S. Pat. No. 5,354,179; EP-A 558921=U.S. Pat. Nos. 5,393,201; 5,295,798; 5,314,312; 5,329,216; JP-Abstract 2283890) have the disadvantage that the rotating parts are of difficult access and cannot easily be maintained because their assembly or dismantling presupposes that they, or a plurality of housing parts accommodating the bearing arrangement, are separated from one another. Since the rotating parts and their bearing arrangement are adjustment-sensitive, specially qualified personnel are required for this, who as a rule are only available to the manufacturer of the pump.
The invention avoids these disadvantages owing to the fact that each rotor, with the associated shaft and a stationary bearing body which can be fixed to the housing and accommodates the entire shaft bearing arrangement, forms a unit which is removable from the housing. The operationally sensitive bearing functions are concentrated in this construction unit. However, there may be applications in which a common bearing body can be provided for both rotors.
The housing forming the pump chamber is expediently defined on the pressure side by a base plate, in or to which the bearing body can be centred and/or fixed. This base plate may be connected in one piece to the pump-chamber housing. However, it is expediently a separate part. It may also be part of the motor housing, which as a rule is arranged on the base plate on the side remote from the pump-chamber housing.
As known from the prior art mentioned at the beginning, it is expedient if at least one rotor bearing is arranged inside the rotor in a space, open only towards the pressure side, on a tubular part, projecting into the rotor, of the bearing body. This ensures that the rotor shaft is subjected to only small bending stresses and that consequently the deformation-induced changes in the clearance of one rotor relative to the other as well as between the rotors and the housing can be kept small. This also permits favourable dimensioning of the rotor shaft, as a result of which the radial space requirement associated with the rotor internal bearing arrangement is partly compensated for.
It is known to provide the rotor shafts with interacting gear wheels which bring about the synchronization of the shafts or permit an emergency synchronization in addition to electronic synchronization. So that these gear wheels are not contaminated due to direct contact with the delivery medium and so that they can be lubricated if need be without the lubricant passing into the pump chamber, they are arranged according to the invention on the motor side of a flange plate, which for this purpose defines a space sealed off from the pump chamber and belongs to the construction unit removable with the rotor. Instead of the gear wheels, the synchronization means may also be pulse generator discs or the gear wheels serve simultaneously as pulse generator discs.
The flange plate is expediently sealed off from the pump chamber by the flange plate being sealed off from the base plate or the motor housing, while the base plate or the motor housing is sealed off from the pump-chamber housing. This enables the flange plate to be mounted and centred on the motor housing. The pump-chamber housing (or its shell and lid) can be removed for the maintenance of the pump chamber
REFERENCES:
patent: 4293290 (1981-10-01), Swanson
patent: 4621994 (1986-11-01), Ellis
patent: 4846641 (1989-07-01), Pieters et al.
patent: 5295798 (1994-03-01), Maruyama et al.
patent: 5314312 (1994-05-01), Ikemoto et al.
patent: 5329216 (1994-07-01), Hasegawa et al.
patent: 5354179 (1994-10-01), Maruyama et al.
patent: 5779453 (1998-07-01), Nagayama et al.
Dahmlos Christian
Rook Dietmar
Steffens Ralf
Freay Charles G.
Ratcliffe Paul L.
SIHI Industry Consult GmbH
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