Pumps – With condition responsive pumped fluid control – Pressure responsive relief or bypass valve
Reexamination Certificate
2001-03-26
2002-10-08
Freay, Charles G. (Department: 3746)
Pumps
With condition responsive pumped fluid control
Pressure responsive relief or bypass valve
C417S201000, C417S418000, C418S201200, C251S063000
Reexamination Certificate
active
06461119
ABSTRACT:
The present invention relates toga variable capacity helical screw compressor for compressing a gaseous medium, usually air. This variation in capacity is achieved with a number of lift valves, normally four lift valves, which cause part of partially compressed air to be returned to the inlet.
One such compressor is known from U.S. Pat. No. 5,556,271A. The lift valve taught by this publication includes an arched valve area which in one end position of the valve forms part of the cylindrical rotor housing of the compressor and which in its other end position is spaced from the opening in the rotor housing with which it co-acts so that partially compressed air is able to leave the working chamber of the compressor and return to the inlet. This arched valve area means that said valve element may not be rotated about its axis. This problem has been solved, by providing the valve housing with a rod of square section which can move in a corresponding square or rectangular opening in the valve element on the opposite side of the valve area
Despite this, it is highly probable that the valve element will be able to rotate about its axis after having been in use over a period of time, and therewith interfere with and cause damage to the rotor.
An object of the present invention is to avoid the problem associated with rotation of the valve element about its axis.
Another object is to provide a helical screw compressor that includes a valve element which has a valve area that enables the valve element to be rotated without damaging the rotor.
These objects are achieved with a helical screw compressor that is characterised by an elastic device disposed between the second side of the valve head and the cap of the valve housing, and is further characterised in that the first and the second compression chambers are one and the same compression chamber.
Preferred embodiments will be evident from the dependent Claims.
REFERENCES:
patent: 1974225 (1934-09-01), Varley
patent: 2459709 (1949-01-01), Lysholm
patent: 4304258 (1981-12-01), Mitchell
patent: 4453900 (1984-06-01), Schibbye et al.
patent: 4498849 (1985-02-01), Schibbye et al.
patent: 5556271 (1996-09-01), Zuercher et al.
Belena John F
Freay Charles G.
Frishauf Holtz Goodman & Chick P.C.
Svenska Rotor Maskiner AB
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