Rotary expansible chamber devices – With mechanical sealing
Patent
1993-05-25
1994-08-16
Casaregola, Louis J.
Rotary expansible chamber devices
With mechanical sealing
384606, 384607, 384617, F01C 1900
Patent
active
053381670
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a dry-running vacuum pump with at least one vertically disposed shaft which is mounted in a top bearing plate by means of a lubricated rolling bearing situated in an open-topped pot-like component.
"Dry-running" vacuum pumps are pumps whose pump chambers contain no lubricant or sealants. Their advantage lies in the fact that they can produce vacuums completely free of hydrocarbons. However, it is impossible to dispense with the lubrication of the bearings of the shafts which bear the pistons rotating in the pump chambers. In dry-running pumps, therefore, it is necessary to assure an effective separation of the bearing chambers from the pump chambers.
A dry-running twin-shaft vacuum pump of the kind described above is disclosed in U.S. Pat. No. 290,662. To achieve separation of the upper bearing chambers from the adjacent pump chambers it is proposed to equip the upper ends of the shafts with an open-topped, pot-like component which traps bearing grease issuing from the bearings. The rolling bearings situated within the pot have a rotating outer ring which is held on the inner wall of the pot-like component. The stationary inner ring rests on a stump affixed to the housing and reaching into the pot-like component. In this system--in comparison with ordinary shaft bearings--there is a separate component between the shaft itself and the bearing ring rotating with the shaft, so that additional seams are present which can impair any correct shaft guidance.
The present invention is addressed to the problem of creating a vacuum pump of the kind described above, in which despite the presence of a pot-like component at the upper end of the shaft any interference with the shaft guidance described above will be avoided.
SUMMARY OF THE INVENTION
According to the invention this problem is solved by the fact that a pot-like component fastened to the housing and open at the bottom is associated with the open-topped pot-like component fastened to the upper shaft end below the rolling bearing, and its wall reaches into the open-topped pot-like component on the shaft, and the roller bearing's stationary ring on the housing is held on the inside of this wall. In this system the advantage is that the shaft--as in a conventional shaft bearing--is in direct contact with the co-rotating inner ring of the roiling bearing; in other words, no additional components or seams are present to impair the shaft guidance. Another advantage is that the result is a compact design, since both the inside and the outside of the pot-like component rotating with the shaft can be used for the formation of gap seals. Of the two gap seals situated coaxially one inside the other (not one following the other axially) in the subject matter of the invention, the inner one lies within the rotating pot-like component, so that any lubricant getting into this gap seal is trapped inside of the pot.
BRIEF DESCRIPTION OF THE DRAWINGS
Additional advantages and details of the invention are to be explained with the aid of the embodiments represented in FIGS. 1 and 2.
FIG. 1 shows a twin-shaft vacuum pump with upper shaft bearings according to the invention, and
FIG. 2 an enlarged section through a shaft bearing according to the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The pump shown in FIG. 1 is a three-stage vacuum pump 1 with two shafts 2 and 3 as well as three pairs of rotors 4-5, 6-7 and 8-9. The axial length of the rotors decreases from the suction end to the discharge end. The rotary pistons are of the claw type (Northey, cf., e.g., Eu-A-290,662) and rotate in the pump chambers 11, 12 and 13 which are formed by the plates 14 to 17 and the housing rings 18 to 20. The plates and housing rings form a housing.
The shafts 2 and 3 are vertically disposed. This is true also of the motor 22 disposed next to the pump housing. Below the bottom bearing plate 17 the shafts 2 and 3 are equipped with gears 23 and 24 of equal diameter, which serve for the synchronization of the motion of the rotor p
REFERENCES:
patent: 4940398 (1990-07-01), Berges et al.
patent: 4983107 (1991-01-01), Steffens et al.
patent: 5051007 (1991-09-01), Maddox et al.
Casaregola Louis J.
Freay Charles G.
Leybold Aktiengesellschaft
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