Pumps – Motor driven – Electric or magnetic motor
Reexamination Certificate
2002-07-31
2004-03-16
Freay, Charles G. (Department: 3746)
Pumps
Motor driven
Electric or magnetic motor
C417S423110, C415S090000, C415S174500, C277S400000, C277S401000
Reexamination Certificate
active
06705844
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a dynamic seal between a rotating part and a stationary part where at least one of the parts is provided with projections which protrude into the seal gap.
In particular in the instance of vacuum pumps there frequently exists the requirement of having to seal shafts which penetrate a separating wall between two chambers at different pressures. Commonly, labyrinth seals are employed to this end, as is also known from U.S. Pat. No. 3,399,827, for example.
In the instances of seals for gaps extending approximately radially it is known (c.f. U.S. Pat. No. 5,165,872, gap seal
43
in
FIG. 5
) to employ purge gases (nitrogen, argon or alike) to protect, for example, a bearing/motor chamber against the ingress of detrimental gases. The purge gas is admitted into the bearing/motor chamber and passes through the seal for the gap into the pump chamber so that it is ensured that gases can not pass from the pump chamber into the motor chamber.
SUMMARY OF THE INVENTION
It is the task of the present invention to create an effective dynamic seal for gaps extending approximately radially between a rotating and a stationary component. This task is solved through the characterizing features of the patent claims.
Through the employment of projections designed by way of engaging rows of blades, not only can the desired sealing effect be improved; moreover, there exists the possibility of assigning to the seal pumping properties beneficial to the application in each instance. If, for example, a chamber is to be protected against the ingress of gases, the rows of blades, respectively the angle of incidence for the blades forming the rows of blades, may be so selected that the seal provides a pumping action in a direction opposed to the direction of the flow of the detrimental gases.
Still further advantages of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiments.
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Wood, et al., “Performance of Centrifugal Shaft Seals For High-Temperature, High-Pressure Liquids”, Machine Design, Jan. 30, 1964, p. 129-136.
Fay Sharpe Fagan Minnich & McKee LLP
Freay Charles G.
Leybold Vakuum GmbH
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