Pumps – Condition responsive control of pump drive motor – By control of electric or magnetic drive motor
Reexamination Certificate
1999-01-22
2001-04-17
Freay, Charles G. (Department: 3744)
Pumps
Condition responsive control of pump drive motor
By control of electric or magnetic drive motor
C417S221000, C417S326000
Reexamination Certificate
active
06217287
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is concerned with variable capacity compressors, vacuum or other pumps or machines, and particularly those reciprocating piston compressors used in refrigeration, air conditioning systems or heat pumps or the like, including machines such as scotch yoke compressors of U.S. Pat. No. 4,838,769, wherein it is desirable to vary the compressor output, i.e., compressor capacity modulation, in accordance with cooling load requirements. Such modulation allows large gains in efficiency while normally providing reduced sound, improved reliability, and improved creature comforts including one or more of reduced air noise, better de-humidification, warmer air in heat pump mode, or the like.
The efficiency gains resulting from a compressor with capacity modulation are beneficial in a variety of commercial applications. For example, most residential refrigerators currently utilize a single capacity compressor and cycle the compressor on and off to maintain a certain temperature within the cabinet of the refrigerator. During normal operation, the temperature of the refrigerator increases due to the warmer ambient air surrounding the refrigerator or when the refrigerator door is opened or a load of perishables having a temperature greater than that of the cabinet is introduced to the refrigerator. If the temperature exceeds a preset limit, the compressor is activated to cool the cabinet of the refrigerator. To account for the higher load conditions when the door is opened or perishables are introduced to the cabinet, the cooling capacity of the compressor is necessarily greater than the minimum required to maintain a particular temperature in the ambient conditions. With this design, the compressor undergoes multiple starts and stops to respond to varying load conditions. The high number of starts and stops will shorten the life of the compressor. Additionally, operating the compressor at full capacity during periods of minimal load is inefficient.
One approach to achieving modulation of a compressor has been to switch the stroke length, i.e., stroke, of one or more of the reciprocating pistons whereby the volumetric capacity of the cylinder is changed. In these compressors the reciprocating motion of the piston is effected by the orbiting of a crankpin, i.e., crankshaft eccentric, which is attached to the piston by a connecting rod means which has a bearing in which the eccentric is rotatably mounted.
A proposed mechanism in the published art for switching stroke is the use of a cam bushing mounted on the crankshaft eccentric, which bushing when rotated on the eccentric will shift the orbit axis of the connecting rod bearing radially and parallelly with respect to the crankshaft rotational axis and thus reduce or enlarge the rod bearing orbit radius. This, in turn, changes the piston stroke accordingly. In such cam action mechanism the piston at the reduced stroke does not attain full or primary stroke top-dead-center (TDC) positioning within the cylinder. This design diminishes compression and permits considerable reexpansion of the only partially compressed refrigerant. The efficiency of the compressor is thus markedly compromised.
Certain prior art cam mechanisms are shown and described in U.S. Pat. Nos. 4,479,419; 4,236,874; 4,494,447; 4,245,966; and 4,248,053, the disclosures of which with respect to general compressor construction and also with respect to particular structures of cylinder, piston, crankshaft, crankpin and throw shifting mechanisms are hereby incorporated herein by reference in their entirety. With respect to these patents the crankpin journal is comprised of an inner and one or more outer eccentrically configured journals, the inner journal being the outer face of the crankpin or eccentric, and the outer journal(s) being termed “eccentric cams or rings” in these patents. The outer journals are rotatably mounted or stacked on the inner journal. The bearing of the connecting rod is rotatably mounted on the outer face of the outermost journal. In these patents, all journal and bearing surfaces of the coupling structure or power transmission train of the shiftable throw piston, from the crankshaft to the connecting rod are conventionally circular.
Referring particularly to the U.S. Pat. No. 4,245,966 patent, a TDC position of the piston is said to be achieved thru the use of two eccentric rings which are provided with stops to orient the cams, in the hope of achieving the TDC position. This structure is very complex, expensive, and difficult to manufacture and to assemble, in a commercial sense. Further, as stated in this patent at col. 4 lines 32-38, the operability of these two eccentrics to attain TDC is essentially by chance and is just as likely to result in a piston-valve plate crash.
OBJECTS OF THE INVENTION
An object of the present invention is to provide an improved coupling structure for a crankpin throw shifting mechanism for a single or multi-cylinder compressor wherein the piston always achieves primary TDC position regardless of the degree of stroke change.
Another object is to provide improved commercial applications of single or multiple compressors that include the improved coupling structure. These and other objects will become apparent from the description and claims of the invention, presented below.
SUMMARY OF THE INVENTION
Accordingly, one aspect of the present invention is directed to a unique, simple and reliable coupling structure for functionally connecting a connecting rod bearing and a crankpin. This structure is adapted to change the primary stroke of a piston while always effecting primary top dead center positioning of said piston on its up-stroke regardless of the stroke change.
In accordance with another aspect of the present invention, as embodied and broadly described herein, the invention is directed to a two stage reciprocating compressor. The compressor includes a reversible motor for rotating in a forward and a reverse direction and a block with a single cylinder and associated single compression chamber and single piston. A mechanical system is provided between the motor and the single piston for driving the piston at a full stroke between a bottom position and a top dead center position when the motor is operated in the forward direction and for driving the piston at a reduced stroke between an intermediate position and the top dead center position when the motor is operated in the reverse direction. There is further provided a control for selectively operating said motor either in the forward direction at a first preselected, fixed speed or in the reverse direction at a second preselected, fixed speed.
According to another aspect, the invention is directed to a refrigerator appliance that includes a two-stage reciprocating compressor that has an electrical motor and a single cylinder with an associated single compression chamber and single piston. The compressor is operable at either at a first stage with a first capacity or at a second stage with a second, reduced capacity.
In another aspect, the invention is directed to a heating, ventilating, and air conditioning (“HVAC”) system for conditioning air within an enclosure. The HVAC system includes a two-stage reciprocating compressor that has an electrical motor and a single cylinder with an associated single compression chamber and single piston. The compressor is operable at either at a first stage with a first capacity or at a second stage with a second, reduced capacity.
In still another aspect, the invention is directed to a power system for a motordriven component of a heating and/or air conditioning system (“HVAC”). The power system includes an induction motor with a start and a run winding and a circuit for controlling the motor to rotate in a forward direction in a first stage and in a reverse direction in a second stage. The circuit design includes a first terminal for connection to line power, a second terminal for connecting to the line power, a capacitor, and a switching device that places the capacitor in series with
Hill Joe T.
Loprete Joseph F.
Monk David T.
Singletary Charles A.
Wagner Philip C.
Bristol Compressors, Inc.
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Freay Charles G.
Gartenberg Ehud
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