Pumps – With condition responsive pumped fluid control – Bypass or relief valve part carried by or carries...
Patent
1996-01-29
1999-02-16
Thorpe, Timothy
Pumps
With condition responsive pumped fluid control
Bypass or relief valve part carried by or carries...
417281, 418 87, 13711806, F04C 2702, F04C 2908
Patent
active
058713387
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention pertains to a vacuum pump with a closable line through which gas ballast can be fed into the pump chamber of the pump.
In the case of vacuum pumps with an inner compression, there is the danger that sucked in vapours might condense in the pump chamber. No condensation will occur as long as the sucked in vapours are compressed by no more than their saturation vapour pressure. If, for example, water vapour is compressed to a higher pressure than this, the vapours condense in the pump and emulsify with the pump's oil. Thus the lubricating properties of the pump's oil reduce very rapidly so that there is the danger of rotor seizure. By admitting gas, preferably air--gas ballast--into the pump chamber of the pump, sucked in gases may be practically diluted thereby increasing the saturation vapour pressure, so that damaging condensations may not occur. It is known to equip the gas ballast facility with a manually operated valve, so that the gas ballast feed may be blocked off when it is not required.
From DE-A-702 480 vacuum pumps with gas ballast facilities are generally known. The rotary vane vacuum pump presented in drawing FIG. 1 of this document has a gas ballast facility where the quantity of the applied.sup.1) gas depends on the intake pressure. At a high intake pressure the valve is open; with reducing intake pressure the gas ballast feed is also reduced. In the case of a failure of a vacuum pump of this kind--for example, by a failure of the drive--the recipient is vented more or less rapidly via the gas ballast feed. instead of . . . zugefuhrte . . . . The latter has been assumed for the translation.
It is known to prevent the recipient from being vented by means of an intake valve which is controlled according to the operating conditions. However, these solutions are involved and are out of the question for cheaper vacuum pump designs. A further possibility to prevent venting of the recipient, is, to ensure that the pump chamber of the pump is hermetically sealed in the case of a pump failure. A solution for this is known from the older application DE-A-42 08 194. In this solution, the oil supply to the pump chamber is blocked in the case of a pump failure, in order to avoid contaminating the recipient with oil vapours. However, functioning of this solution requires that a gas ballast facility not be present, or that it be closed manually prior to the pump failure. Known, so-called hermetically sealed vacuum pumps to date do not offer any protection of the vacuum with the gas ballast switched on.
SUMMARY OF THE INVENTION
It is the task of the present invention to create a vacuum pump of the aforementioned kind, where the danger of venting the recipient via the gas ballast feed does not exist in the case of a pump failure.
This task is solved through the present invention by the characteristic features of the patent claims.
Because the control valve for the gas ballast feed operates depending on the operating conditions and closes in the case of a pump failure, any venting of the recipient via the gas ballast feed can no longer take place. In vacuum pumps with an oil pump, the operation of which depends on the operating conditions, the control valve is preferably actuated by the oil pressure. The oil pressure is a simple and reliable indicator for the operating mode of the vacuum pump. Otherwise hermetically sealed pumps do not require an intake valve for protecting the vacuum.
Further advantages and details of the present invention shall be explained by referring to the design examples presented in drawing FIGS. 1 to 4.
BRIEF DESCRIPTION OF THE DRAWINGS
Drawing FIG. 1 shows a vacuum pump with a gas ballast feed valve according to the present invention.
Drawing FIG. 2 enlarges the gas ballast feed valve shown in drawing FIG. 1.
Drawing FIGS. 3 and 4 show further design implementations for a gas ballast feed valve.
DESCRIPTION OF THE DRAWINGS
The rotary vane vacuum pump 1 presented in drawing FIG. 1 substantially comprises assemblies housing 2, rotor 3
REFERENCES:
patent: 2637947 (1953-05-01), Parks
patent: 3707339 (1972-12-01), Budgen
patent: 4844702 (1989-07-01), Ceccherini et al.
patent: 5066202 (1991-11-01), Berges et al.
patent: 5236313 (1993-08-01), Kim
Abelen Thomas
Arndt Lutz
Muller Peter
Leybold Aktiengesellschaft
Thorpe Timothy
Tyler Cheryl J.
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