Rotary expansible chamber devices – Working member has planetary or planetating movement – Helical working member – e.g. – scroll
Reexamination Certificate
1996-05-07
2001-07-24
Freay, Charles G. (Department: 3746)
Rotary expansible chamber devices
Working member has planetary or planetating movement
Helical working member, e.g., scroll
C418S057000
Reexamination Certificate
active
06264445
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to scroll machines, and more particularly to the elimination of reverse rotation problems in scroll compressors such as those used to compress refrigerant in refrigerating, air-conditioning and heat pump systems.
SUMMARY OF THE INVENTION
Scroll machines are becoming more and more popular for use as compressors in both refrigeration as well as air conditioning and heat pump applications due primarily to their capability for extremely efficient operation. Generally, these machines incorporate a pair of intermeshed spiral wraps, one of which is caused to orbit relative to the other so as to define one or more moving chambers which progressively decrease in size as they travel from an outer suction port toward a center discharge port. An electric motor is provided which operates to drive the orbiting scroll member via a suitable drive shaft.
Because scroll compressors depend upon a seal created between opposed flank surfaces of the wraps to define successive chambers for compression, suction and discharge valves are generally not required. However, when such compressors are shut down, either intentionally as a result of the demand being satisfied, or unintentionally as a result of power interruption, there is a strong tendency for the pressurized chambers and/or backflow of compressed gas from the discharge chamber to effect a reverse orbital movement of the orbiting scroll member and associated drive shaft. This reverse movement often generates objectionable noise or rumble and possible damage. Further, in machines employing a single phase drive motor, it is possible for the compressor to begin running in the reverse direction should a momentary power failure be experienced. This reverse operation may result in overheating of the compressor and/or other damage to the apparatus. Additionally, in some situations, such as a blocked condenser fan, it is possible for the discharge pressure to increase sufficiently to stall the drive motor and effect a reverse rotation thereof. As the orbiting scroll orbits in the reverse direction, the discharge pressure will decrease to a point where the motor again is able to overcome this pressure head and orbit the scroll member in the “forward” direction. However, the discharge pressure will now increase to a point where the cycle is repeated. Such cycling may also result in damage to the compressor and/or associated apparatus.
A primary object of the present invention resides, in one embodiment, in the provision of a very simple and unique unloader cam which can be easily assembled into a conventional gas compressor of the scroll type without significant modification of the overall compressor design, and which functions at compressor shut-down to quickly stop and unload the orbiting scroll and to hold it in check so that the discharge gas can balance with the suction gas, thereby preventing discharge gas from driving the compressor in the reverse direction (other than the very small amount necessary for the functioning of the unloader cam), which in turn eliminates the normal shut-down noise associated with such reverse rotation.
A further object concerns the provision of such an unloader cam which can accommodate without damage extended powered reversal of the compressor, which can occur when a miswired three-phase motor is the power source.
Another object of the present invention resides, in an alternative embodiment, in the provision of an even simpler and unique shaft stop which can also be easily assembled in a conventional scroll compressor without significant modification of the overall compressor design, and which also functions at compressor shut-down to quickly stop the shaft and hold it in check (without unloading the orbiting scroll), thereby preventing reverse rotation and the attendant shut-down noise associated therewith.
Yet another object resides in the provision of such a shaft stop which will prevent powered reversal of the compressor when powered by a miswired three-phase motor. Related objects reside in the provision of such devices, which do not otherwise alter the operation of the compressor, which do not increase starting torque or in any way reduce efficiency, which are easily lubricated with the existing lubrication system, and which are inexpensive to fabricate and assemble.
Both of the primary embodiments of the present invention achieve the desired results utilizing a very simple device which is rotationally driven by the compressor running gear and which under the proper conditions frictionally engages a fixed wall of the bearing housing to physically prevent reverse rotation of the crankshaft and hence reverse orbital movement of the orbiting scroll member. In the first embodiment the device is an unloader cam which is journaled on the outside diameter of the orbiting scroll drive hub, and in the second embodiment the device is a shaft stop journaled on the upper end of the crankshaft.
There are also two further embodiments disclosed which facilitate starting with low-starting-torque motors.
These and other features of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings.
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patent: 4415318 (1983-11-01), Butterworth et al.
patent: 4522574 (1985-06-01), Arai et al.
patent: 4867282 (1989-09-01), Hartley
patent: 4877382 (1989-10-01), Caillat et al.
patent: 5102316 (1992-04-01), Caillat et al.
patent: 5108274 (1992-04-01), Kakuda et al.
patent: 5129798 (1992-07-01), Crum et al.
patent: 5156539 (1992-10-01), Anderson et al.
patent: 5346376 (1994-09-01), Bookbinder et al.
patent: 5496157 (1996-03-01), Shoulders et al.
Anderson Gary J.
Beck Norman G.
Tucker Richard S.
Copeland Corporation
Freay Charles G.
Harness & Dickey & Pierce P.L.C.
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