Pumps – With condition responsive pumped fluid control – Pressure responsive relief or bypass valve
Reexamination Certificate
1998-06-12
2001-02-20
Thorpe, Timothy S. (Department: 3746)
Pumps
With condition responsive pumped fluid control
Pressure responsive relief or bypass valve
C417S440000
Reexamination Certificate
active
06190138
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a valve which opens upon reverse rotation of a scroll compressor to communicate gas downstream of a check valve to a location upstream of the check valve.
Scroll compressors are quite efficient, and thus are becoming more and more widely utilized in refrigerant compression applications. In general, a scroll compressor consists of a orbiting scroll having a base with a generally spiral wrap extending from the base, and a non-orbiting scroll having a base and a wrap extending from its base. The wraps of the orbiting and non-orbiting scrolls interfit to define gas pockets. As the orbiting scroll orbits relative to the non-orbiting scroll, the size of the pocket changes and an entrapped gas is compressed. Scroll compressors are designed to have the orbiting scroll orbit in one direction relative the non-orbiting scroll.
To this end, a motor for driving the orbiting scroll is connected to the orbiting scroll through a mechanical connection which changes the rotation of a motor into orbiting movement of the orbiting scroll. Frequently, the motor is provided with a three phase power supply.
If the three phase power supply is miswired, the motor may run in reverse. If the motor runs in reverse, the orbiting scroll orbits in the reverse direction relative to the non-orbiting scroll. The fluid is no longer compressed, and the systems may heat to undesirable temperatures. In addition, unwanted noise occurs.
This problem is typically encountered with a miswired three phase power supply. However, the problem can also occur with a single phase power supply where there is an intermittent shutdown. An entrapped gas can begin to drive the orbiting scroll in the wrong direction, and when the motor is again started, reverse rotation may continue.
One other concern with scroll compressors is that in some instances, the pressure differential or pressure ratio will become undesirably high. When this occurs, the discharge pressure will become correspondingly high. The prior art has addressed this problem by including separate pressure relief valves, or sensors which sense the results of the high pressure ratio or pressure differential and control the compressor accordingly. The requirement of adding in these additional valves or sensors is undesirably expensive.
It is the object of this invention to address the problem of reverse rotation, and provide a valve which reduces any harmful effects from reverse rotation.
SUMMARY OF THE INVENTION
In a disclosed embodiment of this invention, a valve is normally closed during forward rotation of the motor. Upon reverse rotation, the valve opens and communicates a chamber downstream of a check valve to another chamber upstream of the check valve. By communicating these chambers, the harmful effects of the reverse rotation will be greatly reduced.
In one embodiment, the valve is positioned in a separator plate, and includes a valve with discharge pressure from a chamber slightly upstream of the check valve on one face biasing it to a closed position. Suction pressure is exposed to an opposed face. During normal operation, discharge pressure greatly exceeds suction pressure and biases the valve to a closed position.
However, upon reverse rotation, the discharge pressure upstream of the check valve becomes low compared to the suction pressure. The suction pressure is thus able to move the valve to an open position. The pressure downstream of the check valve is thus able to move upstream of the check valve. This thus reduces the noise and heat generated during reverse rotation.
In a second embodiment, a valve assembly is mounted between a separator plate and an intermediate compression chamber in the scroll pump unit. The valve assembly has a first valve member normally spring biased to a closed position closing a tap to a chamber downstream of a check valve. The first valve also “sees” suction pressure on a top surface of the valve, and an intermediate pressure beneath the valve. A spring biases the valve to the closed position. A second valve moves within the first valve and is held at a closed position within the first valve because intermediate pressure exceeds the suction pressure during normal operation. Thus, during normal operation, the valve assembly is maintained closed and there is no communication between the chamber downstream of the check valve and the intermediate pressure chamber.
However, during reverse rotation, the pressure downstream of the check valve approximates the suction pressure. Both pressures exceed intermediate pressure. The first valve is driven against the spring force to an open position. This allows fluid from the downstream chamber to move through an opening in the first valve and drive the second valve to an open position. The pressure downstream of the check valve now moves through the valve assembly and communicates into the intermediate chamber. This reduces any harmful effects from reverse rotation.
At the same time, once the first check valve is open, the pressure within a chamber that had previously been communicated to the suction pressure drops to the low intermediate pressure level. A third valve, which controls a tap to suction pressure, quickly closes. In this way, upon the occurrence of a reverse rotation, the system pressure downstream of this check valve is quickly communicated into the intermediate pressure chamber, thus reducing any noise or overheating due to the reverse rotation.
This second embodiment also opens to communicate the pressure downstream to the suction chamber when there is a pressure ratio or pressure differential that is too high. Under these circumstances the discharge pressure is high and exceeds the spring and pressure forces holding the valve closed. Thus, the valve opens to relieve the high pressure. This valve operates to balance the intermediate pressure against the discharge pressure and the suction pressure, and should the discharge pressure increase to such an extent that it is indicative of an undesirably high pressure ratio or pressure differential, then the valve will move to an open position, and the discharge pressure chamber is communicated back to a suction pressure chamber. A third valve solely provides this function. The third value and the same feature of the second value, eliminates the need for pressure relief valves, or thermal relief valves, as may typically be incorporated into current production scroll compressors.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.
REFERENCES:
patent: 4840545 (1989-06-01), Moilanen
patent: 5088905 (1992-02-01), Beagle
patent: 5169294 (1992-12-01), Barito
patent: 5362210 (1994-11-01), Richardson, Jr.
patent: 5591014 (1997-01-01), Wallis et al.
patent: 5807081 (1998-09-01), Schutte et al.
patent: 5947701 (1999-09-01), Hugenroth
Barito Thomas R.
Hugenroth Jason J.
Stead Charles A.
Carlson & Gaskey & Olds
Scroll Technologies
Thorpe Timothy S.
Torrente David J.
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