US1922092A

US1922092A - Compressor unit

Info

Publication number: US1922092A
Application number: US476974A
Authority: US
Inventors: Harry B Hull
Original assignee: Frigidaire Corp
Current assignee: Frigidaire Corp
Priority date: 1930-08-30
Filing date: 1930-08-30
Publication date: 1933-08-15
Anticipated expiration: 1950-08-15

Description

A. (15, IQBSQ H @l HULL lggg COMPRESSOR UNIT Filed Aug.. 30, 1.930

#www ,MMM y @5V AWQRNEYS Patented ug. l5, i933 ETE STAT S aire Corpora-tion, Dayt of Delaware on, hio, a Corporation applicati@ august 3o, rese. sensi no. traen 5 Claims.

This invention relates to refrigerating apparatus of the compression type, 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 evaporat-or. 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 asubstantially 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.

Motors having high starting torquesare expensive and for this reason it is desirable to avoid their'use as far as possible. Furthermore, the amount of current drawn during starting is much greater than the amount of current drawn after an electric motor has attained its rated speed; hence it is desirable to reduce the time required to bring the driving motor up to its proper speed.

It is to the above described 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 desired high speed by its motor, and whereby the compressor will be unloaded when its speed is reduced below a certain minimum. More particularly it is an object of this invention, to provide an unloading device dependent for its operation upon the varying pressures of the refrigerant present Within a certain portion of the refrigerating system.

A further object of this invention is to provide, in a refrigerating system, a by-pass extend- Cil (Cl. Zitti- 29) ing between the high and low sides of said apparatus, and to provide means operated by varying pressures in a portion of the system for closing the said by-pass to thereby load said compressor when the latter is driven at a predetermined high speed by its motor or other driving means.

More particularly, it is an object of this invention to provide a gas pump having its discharge side arranged to deliver gas in a closed circuit to close a valve in said by-pass when the gas pump, and consequently the compressor which is connected to it, is driven at a predetermined high speed by the compressor.

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

In the drawing:

Fig. 1 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; and

Fig. 2 is a cross-sectional view on the line 2-2 of Fig. 1.

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 10, connected on its discharge side through a conduit 12 to the condenser 1l, a liquid receiver 13, and an evaporator 14. Refrigerant flows through the parts in the order named. That is, refrigerant is compressed in the compressor 10, discharged through the conduit 12 into the, condenser 11, where it is liquefied and finally collected in liquid form in the liquid receiver 13. From the liquid receiver 13, the refrigerant, in liquid form, passes through the conduit 15 to the evaporator 14. Herein the liquid refrigerant evaporates to produce a cooling effect, the vapors passing fromthe evaporator 14, through the conduit 16 to the crankcase of the compressor, as more fully set forth hereinafter.

The motor 18 is connected to drive the compressor 10, 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 21, the switch 20 being operated by a bellows 22, which bellows is in open communication through a conduit 23 with the suction conduit 16. 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 the evaporator, or to the conditions within the refrigerator which generally houses the evaporator.

The evaporator 14 may be of any desired type. For instance, it may be of the float controlled flooded type similar to that disclosed in the patent to Osborn No. 1,556,708 patented October 13, 1925.

Referring in detail to the motor-compressor unit, I have shown this unit as including a bottom plate 30, to which is secured by means of the bolts 31, 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 a wrist pin 36 to the pitman 37, the pitman 37 being in turn secured to, and enveloping the eccentric 38 integrally connected with the drive shaft 39. The drive shaft 39, to which is secured the counterbalancing weight 40 which is cast integral with the eccentric 38, is journalled in the opposite aligned bearings 41, 42, formed inthe wall of the casting 32. This shaft 39 eX- tends 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 18, 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 uid into or out of the casing at the point where 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 ts a valve plate 50, the valve plate being provided with a passage 51, 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 by the screw 55. Above the valve plate a cylinder head 60, provided with a chamber 61 forming a high pressure chamber, is secured to the casting 32 by 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 16 into the crankcase 33 of the compressor. On the down-stroke of the piston 35, refrigerant passes from the crankcase through the inlet valve 69 to f'lll the cylinder 34. On the up-stroke 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 61 plus the slight pressure 0f 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, pump 100 is provided on the end of the drive shaft 39 of the compressor.

The pump 100 is of the eccentric type and has an oscillating ring 130 which moves around within a groove 131 in the casting 32 and which has its inner surface contacting at one point on the inner surface of the groove 131 and which has its outer surface contacting with the outer surface of the groove at a point 180 from the rst point of contact. The drive shaft 39 at one end has an eccentric portion 132 upon which is mounted a hub 133 which carries the ring 130. The eccentric portion 132 causes the ring to move about in the groove 131 so that the points of contact in the above mentioned relation are maintained but which circle the groove in the direction of rotation of the compressor and at the same speed. The ring 130 is split at one side to receive the dividing plate 134 which spans and blocks the groove at the one point. The dividing plate has cylindrical walls so that it may be free to oscillate in cooperation with the ring 130.

A conduit 102 communicates at one end with the inlet passage 103 to the inner portion of the pump 100 and at its other end communicates through a strainer 104 with the body of oil in the crankcase of the compressor. Oil is drawn into the pump between the inner sides of the ring 130 and the groove 131 from the passage 103 adjacent the dividing plate 134. The oil is forced around the groove by the movement of the ring to the outlet passage 135 which connects to the passage 106 in the drive shaft 39. Lateral passages 107, in communication with the passage 106 in the drive shaft 39, are provided for conveying lubricant to the bearings 41, 42 of the drive shaft 39. A passage 110, provided in the pitman rod 37, is in communication at one end with the passage 106 in the drive shaft 39, and at its other end is in communication with a passage 111 extending through the wrist pin 36. Lateral passages 112 are also provided in the wrist pin 36 for conveying lubricant from the passage 111 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 100 through the various enumerated passages to the Wearing surfaces 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 certain minimum, I have disclosed means for equalizing the pressure on both sides of the compressor piston, and for maintaining said equalized pressure condition until the compressor has an opportunity to reach its predetermined or normal running speed. For instance, in the walls of the casting 32, I have provided a passage 120 communicating through a passage 121 with the interior of the cylinder 34, just below the valve plate 50, and having its lower end extending down to the plug 127 at the top of the bellows chamber 128. A passage 125 connects the lower end of the passage 120 with the crankcase 33 of the compressor.

CII

At its upper end, the passage is provided with a valve seat 122, and a valve 124, the stem of which extends downwardly through the passage 120 and has its lower end connected to the bottom of a bellows 126. The stem of the valve 124 is preferably square in cross-section so as to slide within a square hole in the screw plug 127 to which the upper end of the bellows 126 is fastened with a fluid-tight seal. The bellows tends to keep its natural shape and in this position it holds the valve 124 open.

Gaseous refrigerant to operate the bellows 126 is drawn from the crankcase of the compressor through a passage 137 into the outer portion of the pump 100 and between the outer sides of the ring 130 and the groove 131 where the gaseous refrigerant is forced around the groove 131 and discharged through the passage 138 which leads to the bellows chamber 128. Thus the gaseous refrigerant present in the system is forced into the bellows chamber 128 to provide varying pressures therein to operate the bellows 126.

rlhe bellows chamber is sealed by a screw plug 139 which is provided with a spring loaded relief valve 140 which opens when a predetermined pressure is reached in the bellows chamber 128 so that the bellows 126 will not be subjected to excessive pressure. A vent 142 is provided in the screw plug 139 for allowing the escape of a small amount of gas from the bellows chamber. The vent 142 is made considerably smaller than the passage 138.

The valve 124, together with its stem, the bellows 126 and the screw plug 127 is inserted into position from the bottom of the crankcase through the drilled aperture 141 and this assembly may be screwed into place by a socket wrench engaging the square boss at the lower end of the bellows 126, after which the screw plug 139 may be inserted to close the bellows chamber 128.

In operation, assume the compressor is idle and the valve 124 is open since the bellows, being under no pressure because of the vent 142, assume their natural shape when the compressor is idle. As the compressor starts, during the first few reciprocations of the piston 35 the refrigerant gas to be compressed will pass from the cylinder 34 through the passages 121, 122, past the open valve 124 and back to the crankcase through the passages 120 and 125, the compressor thereby running unloaded. Upon the start of the compressor the outer portion of the pump 100 begins to pump small amounts of gaseous refrigerant from the crankcase into the bellows chamber 128. When the compressor and pump operate slowly no pressure is built up in the bellows chamber 128 because the gaseous refrigerant passes out through the vent 142 as fast as it is pumped. As the motor and compressor speed up, the pump 100 speeds up so that the outer portion of the pump pumps a greater quantity of gaseous refrigerant into the bellows chamber 128 than can escape through the vent 142 and thus gradually produces suicient gaseous pressure in the bellows chamber to compress the bellows and thereby closes the valve 124 while the inner portion of the pump forces oil through Athe bearings of the compressor. When the valve 124 is closed no more refrigerant can pass through the bypass so that the compressor becomes loaded and begins to compress the gaseous refrigerant and force it past the valve reed 52. The check valve 143 prevents refrigerant from flowing from the crankcase back into the suction line 16.

If the pressure in the bellows chamber should rise above a predetermined limit, the springloaded relief valve 140 will open and reduce the pressure below the predetermined limit so as to avoid the possibility of injuring the bellows by excessive pressure.

When the compressor' stops, or its speed reduced to such an extent that the gaseous refrigerant pumped into the bellows chamber 128 is insufficient to overcome the loss of gaseous refrigerant through the Vent 142, the pressure in the bellows chamber will gradually drop and allow the bellows 126 to assume its natural position and open the valve 124, unloading the compresser.

The operation of the valve 124, and therefore the unloading device, it will be seen, is dependent upon the varying pressures vof gaseous refrigerant within the bellows chamber 128. Thus when the pressure within the bellows chamber 128 is increased, because of the increase in speed of the pump 100 and consequently the compressor, the valve 124 will be closed and the compressor loaded. When the pressure within the bellows chamber 128 is reduced, because of the decrease in speed of the pump 100 and consequently the compressor, the valve 124 will be opened and the compressor unloaded.

By properly adjusting the size of the vent 142 to the size of the gas pump, that is by adjusting the capacity of the outlet from the chamber to the capacity of the supply means, (the gas pump) the speed of the compressor at which the compressor is loaded and unloaded may be adjusted. It will be seen that with a large vent 142, the pressure of gaseous refrigerant required to close the valve 124 will be reached after a longer unloaded period of the compressor and at a higher speed of the compressor than with a smaller vent 142. It will be also seen that with a larger vent 142, the

speed at which the pressure in the bellows chamber is reduced to such an extent that the valve 124 opens and unloads the compressor will also be higher than with a smaller vent.

Thus I have disclosed a refrigerant compressor having incorporated therein a loading and unloading device depending for its operation upon the pressure of the gaseous refrigerant present in the refrigerating system. By havingthe compressor unloaded at its start, the motor and compressor will quickly come up to speed with little effort involved on the part of the motor, thus enabling one to use a motor having a low starting torque to drive the compressor.

By the term compressible fluids as used in the claims is meant uids which can be compressed to an appreciable degree and the term as used here is meant to exclude fluids which are practically incompressible such as water and oil.

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 claims which follow.

What is claimed is as follows:

l. In combination, a compressor, means supplying a compressible uid to said compressor, means receiving compressible fluid from said compressor, means for driving said compressor, means for unloading said compressor, and additional means for pumping said compressible iiuid for rendering said unloading means inoperative.

2. In combination a closed circuit having a compressible fluid therein and including a compressor, means for driving said compressor, means for unloading said compressor, and additional tion of the compressor for compressing said compressible iiuid, and a device actuated by said compressible uid for rendering said unloading inoperative.

3. In combination, a compressor for compressing and forwarding a compressible medium through a closed circuit, means for unloading said compressor, and means including an additional pump compressing said compressible medium for loading said compressor.

4. In combination, a compressor for compressing and forwarding a compressible medium through a closed circuit, means for unloading said compressor, and means including an additional pump having one portion for pumping lubricant and another portion for pumping compressible medium for rendering said unloading means inoperative.

means including a pump responsive to the opera.-

5. In combination, acompressor having a compression chamber, a closed circuit containing a compressible medium, means for operatively connecting the compressor and circuit including suction and discharge means for the compressor, means for intermittently operating the compressor, and means for reducing the starting torque of the compressor including a by-pass for conducting compressible medium from the compression chamber to the suction means of the compressor, means for controlling the ow of compressible medium through said by-pass, and means including a bellows and pump for pumping compressible medium to the bellows for closing said controlling means after the compressor is started.

HARRY B. HULL.