US2988263A - Refrigerating apparatus - Google Patents

Description

June 13, 1961 T. H. FOGT REFRIGERATINGAPPARATUS Filed Oct. 23, 1957 INVENTOR.

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Patented June 13, 1961 2,983,263 REFRIGERATING APPARATUS Thomas H. Eogt, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich., acorpqration of Delaware Filed Oct. 23, 1 957, Ser. No. 691,857

1 Claim. (Cl. 230-24) This invent on pertai s to re ig r t n pp us nd sp ially to mo orcompre s r units or r ig ratin systems.

In the normal cyclical operation of motor-compressor units in refrigerating systems, the peak load usually occurs a short time after the beginning of each cycle. The loa normally diminishes during the remainder of the cycle. The peak load is higher as the evaporator temperature rises and will be abnormally high when the system is first started after a prolonged shut-down, especially if the environment temperature is also abnormally high. If the motor is designed for the maximum peak load, it will be much larger and more expensive than if it were merely large enough for the normal load.

It is an object of this invention to provide a compressor arrangement which will never impose more than the normal load on the motor.

It is another object of this invention to provide a compressor arrangement which will prevent the occurrence of abnormal peak loads.

It is still another object of the invention to so control the gas drawn into the compressor that the discharge pressure will never be excessive.

These and other objects are attained in the form shown in the drawings in which a plunger exposed on opposite sides to the discharge pressure and the suction inlet pressure acts to limit the opening of the suction valve as the discharge pressure increases above a predetermined level.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of the present invention is clearly shown.

In the drawings:

FIGURE 1 is a view of a motor-compressor unit, partly in vertical section, embodying one form of my invention, together with the remaining elements of a refrigerating system diagrammatically shown; and

FIGURE 2 is an enlarged sectional view of the peak load limiting arrangement.

Referring now to the drawings, there is shown a sealed motor-compressor unit 20 for withdrawing evaporated refrigerant from the evaporator 22 through the suction conduit 24 and for discharging the compressed refrigerant through the compressor outlet and the discharge conduit 26 to the condenser 28. A refrigerant flow control device 30 such as a restrictor or expansion valve restricts and controls the flow of refrigerant from the condenser 28 into the evaporator 22, so as to maintain a sufficiently low pressure in the evaporator to evaporate the refrigerant at the temperature desired while a sufliciently high pressure is attained in the condenser to condense the refrigerant.

Within the sealed unit 20, there is shown a bearing frame 32 mounted upon three coil springs 34 and provid ed with a central bearing 36. This central bearing 36 contains the drive shaft 38 having the motor rotor 40 fixed to its upper end. At the lower end of the shaft 38 is another bearing 42 and between bearing portion 42 and the bearing portion 36 is an eccentric 44. The .eccentric 44 operates the ring-shaped impeller 46 within the cylinder 48. The cylinder 48 is provided with a spring pressed divider block maintained in engagement with the periphery of the impeller 46, as is customary in this type of compressor. (For an example, see Patent 2,420,442, issued May 13, 1947.) The cylinder 46 is held tightly between the bottom plate 50 which receives the bearing 42 and the bottom of the bearing support 82 which completes the enclosure of the compression space. The bearing support 32 is provided with a suction inlet 52 and an inlet screen 54. The impeller 46 discharges through a discharge outlet valve (not shown) into the interior of the sealed unit 20. The sealed unit 20 contains a supply of lubricant which covers the bottom portion of the cylinder 48 so that lubricant is drawn upwardly by the oil grooves 56 to the bearing surfaces.

The suction conduit 24 connects to an L-s haped suction inlet passage 58 in the plate 50 provided at its upper end with a conical seat receiving a large check valve of a suitable plastic such as polyamide resin. This valve 60 contains an opening 62 tightly receiving the stem of a T- shaped steel face '64. This valve 6% lifts to discharge through the passage 66 in the cylinder 48 connecting with a cavity 68 in the bearing frame 32 leading to the suction inlet 52, as shown in FIG. 1. A circular recess containing the ring-shaped gasket 84 is provided around the check valve 60 between the bottom plate 50 and the cylinder 48 to prevent leakage.

The motor-compressor unit thus far described would be subject to the peak loads during starting periods after a prolonged shutdown. According to my invention, to prevent these peak loads, I provide a limiter or stop pin in the form of a conically pointed plunger 70 which is slida-bly mounted in the wall portion 72 of the passage 66. This plunger 70 is mounted at such an angle that in its lowermost position it will substantially restrict the upward opening movement of the check valve 60. The plunger is exposed to the discharge pressure within the sealed unit 20 on its upper outer end portion and to the suction pressure in the passage 66 on its inner lower end portion. To regulate the position of this plunger 70, it is provided with an enlarged head 74 at its upper outer end which is enclosed Within a retainer 76 having an upper in-turned flange 78 smaller than the head 74 to provide a stop capable of limiting the upward out-ward movement of the plunger 70. The cage 76 is fixed in a counter-sunk aperture to the cylinder 48. It contains a compression-type coil spring 80 surrounding the plunger 76 and hearing at its lower end against the counter-sunk portion of the wall portion 72 and at its upper end against the head 74 so as to provide an upward outward force to balance the normal discharge pressure within the unit 20, which represents the condition for the normal load.

With this arrangement, whenever the discharge pressure rises above normal, the abnormal differential in pressure on the ends of the plunger 70 will force it inwardly and downwardly so that its conical point 82 will move toward the valve 60 and limit its opening. The steel face 64 protects the remainder of the valve 60 from direct contact with the point 82. Thereby, the amount of fluid discharged by the compressor within the unit 20 will be reduced sufliciently that the normal discharge pressure will not be exceeded. This will throttle the gas flowing into the compressor so that the load upon the motor will not be increased even though the evaporator temperature is much higher than normal. The compressor will merely operate a longer time to reduce the evaporator temperature and pressure to normal. By this simple, inexpensive device a much smaller motor can be used since the peak loads are eliminated. This substantially reduces the motor cost, which is one of the most expensive parts of the refrigerating system. This device may be applied to many ditferent types of sealed 3 unit compressors such, for example, as shown in Patent 2,420,442 issued May 13, 1947, as well as to other types of compressors.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, as may come within the scope of the claim which follows.

What is claimed is as follows:

A compressor for pumping gas having an inlet and an outlet and an outlet chamber, a wall dividing said inlet from said outlet chamber, a suction valve for preventing reverse flow through said inlet, a movable stop pin slidably mounted in said wall and movable variable amounts into the path of the opening movement of said valve, said stop pin being exposed on opposite ends to said outlet and inlet pressures providing a force varying with the difference in pressures for causing slidable movement thereof, spring means acting upon said pin for counteracting the preponderant force of the outlet pressure thereon and to vary the position of the pin in accordance with the difierence between the outlet and inlet pressures, said suction valve being movable upon a first axis, said stop pin being slidably mounted for movement upon a second axis transverse to and substantially intersecting the first axis, said path of movement of said stop pin being at an obtuse angle relative to the first axis so that the stop pin engages the suction valve to variably deterrnine the extent of opening movement of said suction valve when the suction valve is in its open position.

References Cited in the file of this patent UNITED STATES PATENTS 765,026 Mason July 12, 1904 1,663,647 Brush Mar. 27, 1928 1,984,171 Baker Dec. 11, 1934 2,034,153 Ploeger Mar. 17, 1936 2,059,760 Teahen Nov. 3, 1936 2,155,384 Carr Apr. 25, 1939 2,295,833 Deschamps Sept. 15, 1942 2,353,347 McCormack July 11, 1944 2,366,188 Gibson Jan. 2, 1945 2,414,878 Hughey Jan. 28, 1947 2,420,442 Rataiczak May 13, 1947 2,641,278 Eplett June 9, 1953 2,641,405 LeValley June 9, 1953 2,691,388 Livers Oct. 12, 1954 2,722,395 Boyce Nov. 1, 1955 2,830,756 Cooper Apr. 15, 1958 2,845,029 Gratzmuller July 29, 1958 FOREIGN PATENTS 34,750 Germany Mar. 11, 1886

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