US2137761A - Refrigerating apparatus - Google Patents

Description

Nov. 22, 1938. A. A. M CORMACK REFRIGERATING APPARATUS Filed Nov. 29, 1933 Patented Nov. 22, 1938 UNITED STATES PATENT OFFICE 2,137,761 BEFRIGEBATING APPARATUS Application November 29, 1933, Serial No. 700,160

1 Claim.

This invention relates to refrigerating apparatus and more particularly to motor-compressor units wherein means are provided for completely unloading the compressor during the starting operation. I

It is desirable in refrigerating apparatus, when utilizing a low starting torque motor, to provide some means for completely unloading the compressor during the starting operation. Various means and instrumentalities have been suggested for performing this function. Some of these devices have unloaded .the compressor at the time of starting and others during the idle period of the compressor but as far .as I am aware,

however, most of these devices are not simple in operation nor are they particularly economical. Particularly when such devices are to be used in a sealed motor-compressor unit it is advantageous to eliminate as many moving parts as pos- 20 sible. This will not only reduce the amount of trouble which would be encountered by a complicated device but would be more economical from the standpoint of construction.

My invention has for its object the provision 25 of an improved type of unloading device, simple in construction, easy to assemble and adapted to be actuated by the gas discharged directly from the compressor.

More specifically the object of my invention 3 contemplates the provision of an unloading device located entirely on the high pressure side of the refrigerating system and adapted to control communication between the high and low pressure sides of the compressor in response to 35 the pressure of the discharge from the compressor.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accom- 40 panying drawing, wherein a preferred form of the present invention is clearly shown.

In the drawing: I

Fig. 1 is a sectional view of a sealed motorcompressor unit together with the diagrammatic 45' elements of the component parts of a refrigerating system;

Fig. 2 is an enlarged fragmentary sectional view of the unloading mechanism;

Fig. 3 is a fragmentary view taken on line 3--3 50 of Fig. 2, and

Fig. 4 is a small top view of the compressor element taken on line 4-4 of Fig. 1.

Referring now to the drawing and more particularly to Fig.1, as a preferred embodiment 56 of my invention, I have shown, a sealed motor,-

compressor unit generally designated by l0, comprising an electric motor II which drives the compressor element l2. Gaseous refrigeran compressed by the compressor l2 passes to the condenser l3 where it is condensed to a liquid 5 arid stored in the receiver l4 until required for use according to the demand of the refrigerating system. Liquid refrigerant is delivered from the receiver l4 to a cooling coil l 5 through a refrigerant line l6 and is admitted to the cooling coil 1 I5 under the control of an expansion valve I] of any suitable type. The liquid refrigerant vaporized in the cooling coil by the absorption of heat therein is withdrawn therefrom through the suction line l8 bythe action of the com- 15 pressor l2 where it is again compressed and circulated according to the described cycle.

Means are provided for automatically controlling the operation of the motor compressor unit and in this modification this means is shown in the form of a snap acting electric switch 20 in ,terposed in the electric circuit 2| of the motor I l. The snap acting switch 20 has a motive power element, such as a sylphon bellows 22 which is responsive to the changes in pressure in the 25 thermostat bulb 23, so as to operate the switch to open and close the contacts thereof and thus interrupt the electric circuit 2| to the motor H of the motor-compressor unit. The thermostat bulb 23 is responsive to the temperature changes of the cooling coil l5 and thus responsive to the refrigeration demand thereof.

' Referring more particularly to the motor-compressor unit, there is provided a cylindrical metal casing 30 in which the component parts of the motor-compressor unit are located. The casing 30 is provided with a top horizontal wall 3| which supports the compressor element 12 and substantially closes that end of the casing. The bottom end of the casing 30 is sealed by means of a removable wall 32 secured and sealed in place by a gasket 33 and a suitable clamping ring 34. Bolts 35 extend through the clamping ring 34 and are threaded into bosses 36 provided on the casing 30 so as to retain the ring 34 and gasket 33 in place. An electric motor II is located in the space provided between the walls 3| and 32 of the casing 30 and is supported by means of bearings 31 and 38; said bearings being integral parts of the walls 3| and 32 respectively.

The motor shaft 39, of the electric'motor ll is positioned vertically within the casing 30 and the lower end thereof rests upon a substantially frictionless bearing 40 consisting of a hardened steel button semi-circular in shape. The upper end of the motor shaft is provided with an extension 4| which is eccentric to the motor shaft 38 and is adapted to operate the compressor element I2 upon rotation of the shaft 39. The compressor element I2 is enclosed within a chamber provided by a cap member 43 which is secured and sealed to the casing wall 3| by means of a gasket 44 and bolts 45. Bolts 45 extend through a flange 46 provided on the cap 43 and threaded into suitable threaded holes 41 in the casing 30.

The compressor element I2 consists of a circular shaped disc member 56 having a concentric flange 5| as an integral part thereof. The flange 5| operates in a groove 52 provided in the casing wall 3|. 1 The surface faces of the flange 5| and the bottom face of the disc member 50 are adapted to provide a moving seal on the surfaces of the groove 52 and the face 53 of the wall 3|. The cooperation of the groove 52 and the disc member 50 provides a space 55 wherein gaseous refrigerant may be compressed. The eccentric extension 4|, of the motor shaft 39, protrudes through the center of the disc member 50 and is adapted to impart a gyratory motion thereto. A ball bearing, bearing member 51 is provided between the eccentric 4| and the disc 50. The gyratory action of the compressor withdraws gaseous refrigerant from the evaporator I5 through the suction line I6, compresses same in the chamber 55 and discharges the compressed gas through the discharge valves 56 into the chamber 42. The suction inlet side I8 of the compressor is separated from the discharge side by a divider block 56.

As previously stated, the wall 3| of the casing 36 substantially closes that end of the casing. The only openings through the wall 3| are the bearing opening, through which the motor shaft 39 extends, thereby substantially closing same, and the openings for the unloading device, to be more fully explained. It will thus be seen from the drawing that the chamber 42 into which the compressed gases are discharged isisolated, and from which no gas can escape to the condenser of the refrigerating system, except by way of the passage 66, passage 64 and chamber 66.

In operation gaseous refrigerant is withdrawn from the evaporator through the conduit I6, chamber I9, and passage I6 whereby it enters the compressor I2 of the motor-compressor unit. The refrigerant gas is compressed by the compressor and discharged into the chamber 42, from which it may pass to the condenser I3 through passages 66, 64 and chamber 66.

Means are provided to unload the compressor when the same comes to a stop after a cycle of operation. To accomplish this function I provide a piston in the passage 64 which piston actuates a valve for controlling communication between the high pressure chamber 66 and the suction passage I6 of the compressor.

For example, my device more specifically is located in a recess 66 provided in the casing 36 of the motor-compressor unit.

This device consists of a piston 6| which has a hollow central portion 62. The side wall of the piston is provided with slots 63 so that gases may pass from the hollow portion of the piston through the side walls. This piston cooperates, in a sliding fit relation, with a vertically located hole 64 provided in the side wall of the casing 30. The hole 64 communicates with the chamber 42 by means of a drilled hole 65 and with the motor chamber 66 throughthe slots 63 of ,the piston 6|.

The chamber 42 thereby has an outlet through which the compressed gases may escape. The compressed refrigerant gases leave the motor chamber 66 through an opening 61 provided in the wall of the casing 30, thereby passing to the condenser I3 of the refrigerating system. The piston 6| moves vertically within the hole 64 and rests against a shoulder 65, provided in the hole 64, when in its upward limit of travel. A coiled spring 66 is located under the piston and is confined between the bottom of the piston 6| and the bottom wall of the recess 60. The compression of the spring 66 thereby tends to maintain the piston 6| against the shoulder 65. When the piston is in this position, at which time the motorcompressor unit is idle, the slots 63 are above the top wall of the recess so that gas cannot pass from chamber 42 to chamber 66. A boss 61 is secured to the top wall of the recess 60 and has a lever 68 pivoted thereto at 69. The lever 66 is provided with yokes III and 'II on opposite ends thereof. The yoke I0 is adapted to fit around the piston 6| and is pivotally secured thereto by a pin 12. The opposite end of the lever carrying the yoke II fits around a solid member I3 and is rigidly secured thereto. The solid member "I3 is provided with a hole therein in which a needle valve I5 is slidably mounted and is retained inan upward position by a coiled spring 16. The valve is spring mounted in this manner so that the piston of the unloading device may vary in its position during the running time of the compressor to a certain extent without causing the valve to lift off its seat in the passage 11. This needle valve is adapted to close a passage 11 which connects the chamber 66 with the suction inlet I8 of the compressor |2 so that gases from the high pressure side of the system may enter the suction side of compressor when the unloader operates to open the passage 11 and unload same.

Between the suction inlet I8 of the compressor and the suction line I6 of therefrigerating system a check valve 60 is provided within a capacity chamber I9. This check valve consists of a disc type valve 8| adapted to rest upon a seat 82 when there are no refrigerant gases passing therethrough and when the pressure in the suction side of the compressor is above that in the evaporator due to the action of the unloading device.

When the motor-compressor unit is idle the unloading device will assume a position as shown in the drawing wherein the piston 6| will be pushed upwardly against the shoulder of the hole 64 by the spring 66 wherein the slot 63 will be above the top face of the recess III. In this position the chamber 42 will have no communication with the chamber 66 with the exception of a bleeder hole 65 which will be hereinafter explained. The needle valve I5 will be withdrawn from its seat in the end of the passage 11 whereby the chamber 66 will be in open communication with the suction inlet I6 of compressor, thereby permitting high pressure gas from the chamber 66 to enter the suction side of the compressor so that the pressure in the suction side of the compressor will be the same as that existing in the chamber 66 and chamber 42 at the time of starting. Since both sides of the compressor are at the same pressure, the motor may start under an unloaded condition and a low torque motor may be used.

When the motor starts, in response to the closing of the electric switch 20, high pressure gaseous refrigerant from the chamber 66 will enter 'sition in the opening I1, thereby preventing high the chamber of the compressor and be discharged through the valves 56 into the chamber 42. It is to be remembered that chamber 42 has no outlet except through openings 65 and 64 and the piston 6|, hence a higher pressure will be built up therein than is present in chamber 66 and the condenser l3 of the refrigerating system. This increase in pressure in chamber 42 and its communicating openings exerts its force on the piston SI and will move the piston downwardly against the action of the retaining spring 56 to a position where the slots 63 will be open to the recess and hence to the motor chamber 66. While the piston is moving downwardly, the lever 68 is carrying the needle valve 15 upwardly to close oi! the passage 11. When the needle valve has thus closed ofl? the passage ll, high pressure refrigerant gas can no longer enter the suction passage ll of the compressor 12, at which time the compressor may then withdraw gaseous refrigerant irom the evaporator after it has reduced the pressure in the suction passage 18.

The pressure in the chamber 42 will be maintained above that in the motor chamber 58 as long as the motor-compressor unit is operating due to the fact that the compressed'gases cannot pass to the condenser 13 of the refrigerating system without passing through the restriction caused by the piston 6| and slot 63. The degree oi! restriction to create the pressure differential between the chambers 42 and 66 is determined by the tension of the spring 66, thereby any operating diflerential may be obtained by changing the spring or the amount of compression thereof. This pressure differential will be maintained between the chambers 42 and 66 as long as the compressor is in'operation due to the fact that a deflnite primary increase in pressure is needed to move the piston BI and when this point is reached a, balanced condition will result between the pressure exerted downwardly on the piston by the pressure of the gas and the pressure exerted upwardly thereon by the spring 56 so that the quantity of gas permitted to pass through the piston will equal the output from the compressor. As long as this difierential in pressure is maintained between the two chambers,

the needle valve II will be held in a seated poits starting period and t0 load the pressure gaseous refrigerant from entering the suction side of the compressor at any time during the operation of the compressor.

When the control switch 20 breaks the electric circuit to the motor of the motor-compressor unit in response to the cooling coil l5, the compressor will gradually come to a stop. At this time the pressures in chambers 42 and 56 are equalized by the escape of gases from the cham-| 10 ber 42 to the chamber 66 through the slots 63 and the bleeder hole 55 in the side wall of the piston 6!. The bleeder hole is provided so that an exact equalization of pressure may be accomplished between the chambers 42 and 66 whereby the piston 6| will move to its full upward position to fully open the unloading passage H. The compressor unit is now in position to make another start in an unloaded condition.

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, all coming within the scope of the claim which follows.

What is claimed is as follows:

A motor-compressor unit comprising 2. casing, a sealing dividing wall extending across the casing to divide the easing into two compartments, a compressor iocatedin one of said compartments, an electric motor in another of the compartments for driving the compressor, said 7 compressor having a discharge outlet discharging into its compartment, the dividing wall structure of said casing being provided with a restricted passage connecting said compartments through which fluid discharged by said compressor flows, said compartment containing the elec-- ated by the pressure diflerential between said compartments to unload the compressor during compressor during normal operation. 1

ALEX A. MOCORMACK.

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