US2038176A - Compressor unit - Google Patents

Description

COMPRES SOR UNIT April 21, 1936. l H. B. HULL Original Filed June 30, 1950 Patented Apr. 21, 1936 COMPRESSOR UNIT Harry B. Hull, Dayton, Ohio, assignor, by mesne assignments, to General Motors Corporation, corporation of Delaware Application June 30, 1930, Serial No. 465,022 Renewed January 6, 1934 8 Claims. (Cl. 23029) This invention relates to compressor units, and more particularly to motor-compressor units for use in refrigerating apparatus of this type.

. In refrigerating apparatus of the compression type, it is customary to provide a compressor having its discharge side connected to a condenser and its inlet side connected to an evaporator, the discharge side of the condenser being-in turn connected to the inlet side of the evaporator. Refrigeration is produced by evaporating a liquid refrigerant under reduced pressure in the evaporator, the -vapors being compressed into, and condensed in a condenser under a considerably high pressure.

In order to maintain the evaporator, or the refrigerator which generally houses the evaporator, at a substantially constant temperature, it is customary to operate the compressor intermittently. .That is to say, it is customary to start the compressor when the temperature within the evaporator increases to a. predetermined high limit and to stop the compressor when the temperature falls to a predetermined low limit. Since the discharge side of .the compressor is under condenser pressure and the inlet side of the compressor is under evaporator pressure, obviously the compressor must start under a heavy load,

and consequently a motor having a high starting torque must be used, unless some means are provided whereby the motor and compressor are. first permitted to attain predetermined speed before the'load is applied thereto.

It is to such apparatus that my invention relates, having for one of its objects means for loading and unloading the, compressor, whereby the compressor will be loaded only when it is driven at a predetermined high speed by its motor, and whereby the compressor will be unloaded when its speed is reduced below a predetermined minimum. More particularly it is an object of this invention, to provide an unloading device dependent for its operation on the presence of lubricating oil within the compressor lubricating system.

A further object of this invention is to provide, in refrigerating apparatus, a bypass extending between the high and low sides of said apparatus, and to provide means in said bypass for closing the said bypass 'to thereby load said compressor when the latter is driven at a predetermined high speed by its motor or other driving means. More particularly to provide an oil pump having its inlet in communication with the oil in the lubrieating system of the compressor, and having its discharge side arranged to deliver, oil to close a valve in said bypass when the oil pump, and consequently the compressor, is driven at a predetermined speed by its motor.

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

In the drawing:

The figure is a diagrammatical view of a refrigerating system of the compression type, having incorporated therein a motor-compressor unit shown partly in section and partly in elevation. v

In order to illustrate my invention, I have shown a refrigerating system of the compression type, having incorporated therein a motor-compressor unit embodying the features of my invention. For instance, I have shown a compressor, generally indicated by the reference character "I, connected on its discharge side to the condenser ll, through a conduit ii, a liquid receiver l3, and an evaporator ll. Refrigerant may flow through the parts in the order named. That is, refrigerant is compressed in the compressor l0,

discharged through the conduit l2 into the condenser II, where it is liquefied and finally collected in liquid form in the liquid receiver I 3. From the liquid receiver l3, the refrigerant, in liquid form, passes through the conduit l5 to the evaporator l4. Herein the liquid refrigerant evaporates to produce a cooling effect, the vapors passing from the evaporator I, through the conduit I6 to the crankcase of. the compressor, as more fully set forth hereinafter. The motor i 8 is connected to drive the compressor l0, and in order to maintain the temperature within the evaporator substantially constant, I provide means for starting and stopping the motor, and consequently the compressor, in response to predetermined high and low pressure conditions within the evaporator. To this end, a switch 20 is provided in the motor circuit 2 I, the switch 20 being operated by a bellows 22, which bellows is in open communication through a conduit 23 with the suction conduit it. Thus the motor and compressor are controlled in response to predetermined high and low pressure conditions within the evaporator. In view of the fact that the pressure conditions within the evaporator vary directly with the temperature conditions therein, the motor-compressor unit is in reality responsive to the temperature conditions within .30, to which is secured by means of the bolts 3| a casting 32, forming a lower crankcase portion 33 and an upper cylinder portion 34. Within the cylinder 34 is mounted to reciprocate a piston 35, which piston is connected by means of a wrist pin 36 to the pitman 31, the pitman 31 being in turn secured to, and enveloping the eccentric 38 secured on the drive shaft 39 and formed integrally with a counterbalance weight 40. The drive shaft 39 is journalled in the opposite aligned bearings M, 42, formed in the wall of the casting 32. This shaft 39 extends outwardly through the casting 32, as at 44, and has secured thereto a flywheel pulley 46, over which pulley, a belt, driven in the usual way by the motor I3, is adapted to pass. A seal, or stuffing box, of any known type, is, of course, used to seal the shaft to prevent the escape of fluid into or out of the casing at the point when the shaft 39 passes through the casting 32. The upper portion of the casting 32 is provided with a cutaway portion 48, within which cutaway portion fits a valve plate 50, the valve plate being provided with a passage 5|, controlled by a valve reed 52, which valve reed 52 is normally held closed by a light leaf spring 54 secured to the valve plate 50 by the screw 55. Above the valve plate a cylinder head 60 provided with a chamber 6I forming a high pressure chamber, is secured to the casting 32 by means of the bolts 62, and between the cylinder head and the casting 32 is provided a confined lead gasket 66. The inlet to the compressor is provided through the crankcase, and to this end an opening 68 is provided in the wall of the casting 32 whereby the'refrigerant from the evaporator may pass into the crankcase 33 of the compressor. An inlet valve 69, herein shown as of the disc valve type, is provided in the head of the piston.

Thus, as the compressor operates, refrigerant in vapor or gaseous form, is drawn through conduit I6 into the crankcase 33 of the compressor. On the downstroke of the piston 35, refrigerant passes from the crankcase through the inlet valve 69 to fill the cylinder 34. On the upstroke of the piston, the refrigerant is compressed until the pressure of the refrigerant within the cylinder 34 exceeds the pressure of the refrigerant within the chamber 6| plus the slight pressure of spring 54, whereupon the compressed refrigerant is forced past the valve 54 into the high pressure line. This cycle is constantly repeated.

Means are provided for lubricating the compressor, and in this modification this means is shown as including a body of oil in the crankcase and an oil pump having its inlet side below the level of oil in the crankcase and its discharge side connected to various ducts leading to the bearings and wearing surfaces of the compressor. For instance, an oil pump I00, herein shown as of the eccentric type, is provided on the end of the drive shaft 39 of the compressor. A conduit I02 communicates at one end with the inlet passage I03 to the oil pump I00 and at its other end communicates through a strainer I04 with the body of oil in the crankcase of the compressor. A passage I06 in the drive shaft communicates with the chamber I08 into which chamber the oil pump discharges, and lateral passages I01, in communication with the passage I06 in the drive shaft 39, are provided for conveying lubricant to the bearings 4|, 42 of the drive shaft 39. A passage IIO, provided in the pitman rod 31, is in communication at one end with the passage I06 in the drive shaft 39, and at its other end is in communication with a passage III extending through the wrist pin 36. Lateral passages II2 are also provided in the wrist pin 36 for conveying lubricant from the passage II I to the sides of the wrist pin 36. Thus the various parts of the compressor are lubricated by a forced feed lubricating system, the lubricant being withdrawn from the crankcase 33 of the compressor and forced by the oil pump I00 through the various enumerated passages to the wearing sur faces of the compressor.

In order to provide means whereby the compressor may attain its normal running speed before its load is applied thereto, and to provide means whereby the compressor will be unloaded should its speed be reduced below a predetermined minimum, I have disclosed means operating in conjunction with the lubricating system for equalizing the pressure on both sides of the compressor piston, and for maintaining said equalized pressure condition until the compressor is driven at a predetermined or normal running speed. For instance, in the walls of the casting 32 I have provided a. passage I20 having its upper end communicating through a passage I2I with the interior of the cylinder 34, just below the valve plate 50, and having its lower end in communication with the crankcase 33 of the com--' pressor. At its upper end, the passage I 20 is provided with a valve seat I22, and a valve I 24, the stem of which extends downwardly through the passage I20 into a pocket I26 in a piston I28, which piston slides within a cylinder I30 formed integral with the casting 32. Within the pocket I26, 9, spring I34 has its lower end bearing against the piston I28 and its upper end secured to the bottom of the valve stem. A passage I38 has one end in communication with the cylinder I30 and its other end in communication with the chamber I08 whereby oil discharged by the oil pump I00 may pass to the cylinder I30 beneath piston I28 to force the valve I24 against its seat I22. An oil pressure relief p'ort I40 is provided in the walls of the cylinder I30 whereby excess oil pressure may be vented to the crankcase.

In operation, assume the compressor is idle and the valve I 24 is open. As the compressor starts, during the first few reciprocations of the piston 35, the refrigerant gas will pass from the cylinder 34 through the passages I2I and I22, past the open valve I24 back to the crankcase, the compressor thereby running unloaded. As the motor speeds up, the oil pump I00 speeds up, gradually producing suflicient oil pressure to push up the piston I28 to close valve I24. The compressorthen becomes loaded.

Should the speed of the motor or compressor be reduced, the oil pressure will be insufllcient to hold piston I28 in its upper position. Consequently, the piston falls and the valve I24 opens, thereby allowing the compressor to run idle. Also, when the compressor stops, the oil within the cylinder I30 immediately escapes through the various bearings to the crankcase, thereby allowing the piston I 28 to drop and permitting the spring I34 to open the valve I24, to unload the compressor.

Thus I have disclosed a compressor having incorporated therein a loading and unloading device depending for its operation upon the presence of lubricating oil within the compressor lubricating system. Should the quantity of lubricant become diminished below a safe margin, due to any cause whatever, the oil pressure generated by the oil pump will be insufficient to close the inlet valve and consequently the valve I22 will open, allowing the compressor to run idle. This idle running of the compressor will indicate to the operator that something is wrong with the compressor. Further, I have disclosed an unloading device operating in conjunction with a compressor whereby during the starting of the compressor the load applied thereto will be zero, the compressor not even having to overcome the slight pressure exerted by the outlet valve in the valve plate. In addition, I have disclosed apparatus which not only actuates the loading and unloading device of the compressor but also forces the lubricant to the various bearings of the apparatus.

Whilethe 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 claims which follow.

What is claimed is as follows:

1. In a motor-compressor unit, a compressor and a motor for driving said compressor, said compressor including a cylinder, a piston in said cylinder, an inlet valve in the head of the said piston, a valve plate at the upper end of said cylinder, said valve plate including a discharge valve, and said compressor including means for unloading said compressor whereby its normal running speed may be attained before it becomes loaded, said last named means including a bypass communicating with the upper end of said cylinder below said valve plate and with the crankcase of the compressor.

2. In.a motor-compressor unit,. a compressor and a motor for driving said compressor, said compressor including a cylinder, a piston in said cylinder, an inlet valve in the head of the said piston, a valve plate at the upper end of said cylinder, said valve plate including a discharge valve, and said compressor including means for permitting said compressor to attain its normal running speed before it becomes loaded, said last named means including a by-pass communicating with the upper end of said cylinder below said valve plate and with the crankcase of i the compressor, and means 'in said by-pass for closing said by-pass when the compressor is driven at a predetermined high speed by said motor. a

3. In a motor compressor unit, a compressor and a motor for driving said compressor, said compressor including a cylinder, a piston in said cylinder, an inlet valveln the head of the said piston, a valve plate at the upper end of said cylinder, said valve plate including a discharge valve, and said compressor including means for permitting said compressor to attain its normal running speed before it becomes loaded, said last named means including a by-pass communicating with the upper end of said cylinder below said valve plate and with the crankcase of the compressor, and an oilpump and a pressureoperated valve in said by-pass responsive to the pressure from said oil pump for closing said by- I pass.

piston, a valve plate at the upper end of said cylinder, said valve plate including a discharge valve,.and said compressor including means for permitting said compressor to attain its normal running. speed before it becomes loaded, said last named means including a by-pass communicating with the upper end of said cylinder below said valve plate and with the crankcase of the compressor, and an oil pump and a pressureoperated valve in said by-pass responsive to the pressure from said oil pump for closing said bypass, said oil pump being located at the end of said crankshaft.

5. In a motor compressor unit, a compressor and a motor for driving said compressor, said compressor having a low pressure side and a high pressure side, a cylinder, a piston in said cylinder, an inlet valve for said cylinder, a valve plateat the upper end of said cylinder, said valve plate including a discharge valve, and said compressor including means for permitting said v compressor to attain its normal running speed inder, a'valve plate at the upper end of said cylinder, said valve plate including a discharge valve, and said compressor including means for unloading said compressor whereby its normal running speed may be attained before it becomes loaded, said last named means including a bypass communicating with the upper end of said cylinder below said valve plate and with the low pressure side of the compressor.

.7. In a motor compressor unit, a compressor and a motor for driving said compressor, said compressor having a low pressure side and a high pressure side, a cylinder, a piston in said cylinder, an inlet valve for said cylinder, an outlet valve for said cylinder, said compressor including means for permitting said compressor to attain its normal running speed before it becomes loaded, said last named means including a by-pass in unrestricted communication with said cylinder interiorly of said outlet valve and communicatvolume of said compressor space, an outlet portfor said space, said compressor including means for permitting said compressor to attain its nor mal running speed before it becomes loaded, said last named means including a by-pass in communication with said space interiorly of said out-, let port and communicating with the low pressure side of said compressor.

HARRY B. HULL.

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