Rotary expansible chamber devices – Heat exchange or non-working fluid lubricating or sealing – With pump for non-working fluid
Patent
1998-01-14
2000-02-01
Denion, Thomas
Rotary expansible chamber devices
Heat exchange or non-working fluid lubricating or sealing
With pump for non-working fluid
418 93, 418 98, 418269, F01C 2104
Patent
active
060195851
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention concerns an oil-sealed vane-type rotary vacuum pump with the characteristics of patent claim 1.
A vacuum pump with the characteristics of patent claim 1 is known from DD-A-256540. Laid open in this publication is a single-stage vane-type rotary vacuum pump, the rotor of which is suspended at both its ends by means of a journal bearing. The two journals as well as the related bearing sections are equipped with bores which are so formed and arranged that they act like cocks which control the entry and discharge of an excess oil flow passing through the space between the vanes. The arrangement, or the way in which the bores are assigned, is so selected that the oil enters the space between the vanes via the first journal when the space has attained its greatest volume. During this phase, and also during the subsequent phase during which the volume of the intermediate space reduces, the discharge of oil in the direction of the oil sump is blocked. Thus an increased oil pressure builds up in the space between the vanes, so that oil may enter into the suction chamber through slots which are present between the vanes and the slots in the vanes and in the area of the face sides of the rotor so that said suction chamber is supplied with the necessary sealing and lubricating oil. Shortly before the space between the vanes attains its smallest volume, the oil discharge ahead of the second journal is opened. Owing to the pumping action of the space between the vanes, the excess oil is ejected and is returned to the oil sump.
SUMMARY OF THE INVENTION
This solution according to the state-of-the-art has the disadvantage, that the way in which the oil is supplied into the suction chamber is not defined since it is effected via slots which are subject to manufacturing tolerances and which are subject to wear. Moreover, the known solution requires the presence of journals on both sides of the rotor. In the case of a cantilevered rotor, this state-of-the-art solution can not be implemented. Finally, ever so often high oil pressures will build up briefly in the space between the vanes, which give rise to considerable noise (oil slap).
It is the task of the present invention to design a vane-type rotary vacuum pump of the aforementioned kind, in which noises due to oil slap are mostly avoided.
According to the present invention this task is solved through the characteristic features of patent claim 1. In a vacuum pump designed according to the present invention, oil passes into space between the vanes when the space increases in volume. Moreover, the link linking the space between the vanes and the suction chamber is permanently open. Thus an increased oil pressure can not build up. During the phase of decreasing volume of the space between the vanes, no oil is admitted so that the pumping effect of the space between the vanes can not have an influence on the oil flow. Oil slap will not occur. The quantity of oil which enters into the space between the vanes is adjustable through the size of the bores in the casing and the bearing section, the openings of which oppose each other briefly during each turn of the rotor. The size of the bores may be selected in a simple manner so that only exactly that quantity of oil is admitted into the space between the vanes, and thus into the suction chamber, which will be sufficient to meet the vacuum engineering requirements of the pump, while at the same time taking into account the requirements of the application, for example. It is important that the oil entering the suction chamber be unpressurerized. From there it passes via the discharge of the pump back to the oil sump. Finally, only one bearing journal suffices to control the oil flow in the space between the vanes, so that the present invention may also be utilised in vacuum pumps having a cantilevered rotor.
A further reduction in the noises which occur during operation can be obtained by supplying into the space between the vanes a mixture of oil and air. This mixture may be produced
REFERENCES:
patent: 4276005 (1981-06-01), Bassan
patent: 4844702 (1989-07-01), Ceccherini et al.
patent: 5236313 (1993-08-01), Kim
Abelen Thomas
Muller Peter
Denion Thomas
Leybold Vakuum GmbH
Trieu Thai-Ba
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