US2319310A - Refrigeration system - Google Patents

Description

Patented May 18, 1943 REFRIGERATION SYSTEM Herbert D. Euwer, St. Louis, Mo., assignorto f American Car and Foundry Company, New York, N. Y., a corporation of New Jersey Application February 27, 1939, Serial No. 258,622

10 Claims.

This invention relates to refrigerating systems in general and in particular to such systems adapted for use on vehicles, Whether of the road or rail type. In certain types of vehicles it is highly advantageous to use a refrigeration equipment having a continuously runningprime mover of any suitable type, such as an internal combustion engine. Due to the fact that refrigeration demands on the equipment are intermittent, it has been necessary in the past to provide heavy and expensive couplings, either` of the electrical or centrifugal clutch type, in order that the compressor may be disconnected and will work only during such times as refrigeration is required, while the prime mover may run continuously. It is an object, therefore, of the present invention to provide a refrigeration system in which the heavy and expensive couplings between the prime mover and the compressor may be eliminated.

A further object of the invention is the provision of a refrigeration system in Which the prime mover and compressor may run continuously, While the compressor will accomplish useful work only at intermittent intervals `and then only upon demand.

A still further object 0f the invention is the provision of a refrigeration system having a continuously running prime mover and a compressor in which the compressor may be loaded and i unloaded automatically in accordance with predetermined pressure conditions existing Within the system.

A yet further object of the invention is the provision of a refrigeration system having a condenser, the cooling capacity of which may be automatically kincreased upon and in accordance with an increase of pressure in the system beyond a predetermined value.

These and other objects of the invention will be apparent to persons skilled in the art from a study of the following description and accompanying drawings, in which Figure 1 is a perspective view of the maior portion of the system;

Fig. 2 is a perspective view of the remaining portion of the system and when taken together with Figure 1 discloses substantially the entire refrigerating system, and

Fig; 3 is a schematic wiring diagram disclosing the electrical connections for the system.

-Referring now to the drawings in detail, it will be seen that the system alone has been illustrated without any particular reference to its position or location in the vehicle, but as is cus- VC connected to a prime mover E, which is also connected-to a drive generator G. 'Ihe usual engine radiator R is provided for dissipating the heat generated by the internal combustion engine, While condenser H is connected in the y system for dissipating the heat extracted from the vehicle by the cooling and Ventilating unit V (see Fig. 2) located in the vehicle. In the present instance the engine has been illustrated as of the internal combustion type but it is obvious that any prime mover of a different type might be utilized without in any Way affecting l the operation of the system. The engine illustrated is of the automotive type having cylinder block 2 in which are reciprocally mounted pistons connected to the crank shaft, which is in turn connected to shaft 4 upon which are mounted a plurality of pulleys 6 and 8. In order to cool the engine and dissipate the heat therefrom conventional connections 9 are made between the engine cylinder block and the radiator R previously referred to. The pulleys 6 receive belts l0 which transmit the power from the engineto pulleys l l mounted on compressor crank shaft l2. The compressor crank shaft carries any suitable number of pistons reciprocating in cylinder block I4 and provided with the necessary `and customary valves by means of which gaseous refrigerant may be compressed to a suflicient degree that when cooled by the condenser it will become liquid. The pulley 8 mounted on the engine crank shaft is connected by means of belt I5 t0 pulley I6 mounted on the end of an armature shaft of the generator G. The engine generator Yand compressor are provided with suitable,

frame and base arrangements B by means of which they may be mounted upon a supporting structure preferably forming a rigid part of the vehicle.

Gaseous refrigerant after being compressed in the compressor may escape from the cylinder block through connection I 8 to high pressure outlet pipe I9 which is connected through a discharge cutoff valve 20 located intermediate the compressor andan oilseparator 22. The oil separator, which is of an approved type, is provided adjacent its bottom portion with an oil drain connection 23 connected by means of piping 24 to an oil iioat 26, Which is in turn connected by piping 2l Vstrainer' 5i). The

to a connection 28 on the compressor crank case. Through this piping and oil float oil separated from the gaseous refrigerant in the separator is collected in the oil float chamber and after it has reached a certain height is discharged back to the compressor crank case. The gaseous refrigerant after passing through the oil separator and giving up its oil passes out of the separator through connection 30 and pipe 32 to the condenser coil structure for dissipation of the heat of compression and to be sufliciently cooled to condense into a liquid. The pipe 32 has interposed therein intermediate the oil separator and condenser a check valve 33 which is so positioned as to prevent return flow of refrigerant from the condenser to the oil separator while permitting unrestricted flow of the refrigerant from the denser. After the gaseous refrigerant has been condensed to a liquid in the coils of the condenser Hsuch liquid is drained off through piping 34 into a liquid receiver 35. The liquid receiver is provided witha sealed in glass inspection opening 31 in order that the refrigerant liquid level may be determined and it is. also provided with a purge valve 38 by means of which liquid refrigerant may be withdrawnfrom the system prior tomaking repairs to the system. Liquid from the receiver is withdrawn through pipe 39 to the evaporator coils (not shown)Y located in the cooling and ventilating unit V. The pipe 39,has interposed thereinra pair of manual valves ,45 and 4l located on either side of a strainer 42, whichstrainer will prevent any foreign matter from reaching the evaporator coils. In case the strainer becomes clogged closing the valves 40 and 4l will permit the removal of the strainer .from the system without necessity for .removing the .refrigerant `therefrom. rThe fluid flowing in pipe 39 to the evaporator coils can only. reach such vcoils after passing normally open refrigerant control valve FV, preferably located in the pipe adjacent the evaporator coils andquite close to the expansion valves lll..` These expansion valves are of any approved Vtype, but preferably of .the type which will insure maximum efdciency lin the expansion of the refrigerant from the liquid tothe gaseous state, thus providing maximum efciency for the evaporator coils. After thegaseous refrigerant in the evaporator coils has absorbed heat from the vehicle air circulated ,throughv the cooling unit, such gaseous refrigerant may return directlyto thecompressor through ,pipinglidY The gaseous Vrefrigerant flowing .fromthe evaporator coils to thecompressor must pass through connection 4l, check valve 38, manual control valve 45 and suction c line check valve 48 permitsuninterrupted flow of refrigerant from the evaporator coils to the compressor, but will prevent return flow of refrigerant from the4 compressor to the evaporator coils. The suction line or return pipe 45 is connected to the `compressor by connector 52 and is also provided with an additional connector 53 joined by pipe 54 to a gauge manifold 55. The. pipe 54 is connected to the manifold through manual valve 5B,.permitting entrance of refrigerant into the manifold in order that the pressure in the suction line maybe indicated on low pressure gauge LP and also permitting the charging of the system through charging connection 53.

In order that the compressorrnay be made to assume or be relieved of load pipe 6i) is joined to the suction line connector 52 and extends from such connector to a T 6l. From this T pipe B2 leads directly to asecond T 63-and this pipehas interposed therein a manual cutoff valve 64. The

separator to the con- Ts El and B3 are joined together by means of piping 6B in which is interposed cut-off valves 61 and an electrically controlled by-pass valve SV. The pipe 69 connects the T E3 with the connector 30 adjacent the oil separator, thus it will be seen that the portion of the pipe between the by-pass valve SV and the oil separator is a high pressure line, while the portion of thepiping between the by-pass valve and the compressor is normally subjected to low pressures. The manual control valve 64 and pipe 52 is provided merely to permit manual by-passing of refrigerant around the electrically controlled by-pass valve SV, but normally the valve 54 will be closed and control of refrigerant ow given over to the automatic valve SV.

For certaincontrol purposes pipe 10 is connectedrinto the head of the compressor and extends directly to the gauge manifold through manual valve l2, thereby permitting reading of the pressure in the cylinder head vby' observation of high pressure gauge HP. The pipe ".10 is provided ywith two c"0nnec'tors"`l3 and"'l'4. "The connector 'I3 is joinedI by pipe 15 to a Water'regulatingvalve 11,"which 'valve will control 'ow of Water' to the condenser Ac'oils'as lwillA later -be described.. The connector 1`4'is'joined'by`pi'pe"18 to a high and low'pes'sur 'switch 80 lwhich i's in turn co'nr'nec'tedby` pipe 82 `to the connector 4l in the vrow pressure or suction line' intermediate the check v'alv'el' and the evaporator coils.' Y''lie high and lowpressure switch is of any approved type but in `general consistsv of a' diaphragm 'subjected on opposite'si'des' to' 'different4 pressures 'and movable under'variati'on' in pressures to 'complete contacts in an'ele'ctric' circuit.

y.Ihe kcooling capacity ofthe 'condenser mayl be increased by permitting water to `flowA ther'ever and to' this end water'storage'tanls'kl' are Aprovided, which tanks mayv'be'l'led't'hrou'gh piping 8'5, with lthe tvvoY tanks interconnected by means ofpipe 55.. AOlnefof the tanks is provided with an outlet toI which vis connected 'a'pi'pe'8l joined to cutoff valve'lll'and strainer 89` which is interposed between the 'cutoff' va'lve'fan'd Ythe water regulator valvey )'lfpreviously r'efe'rred'to. Normally the cutoff valve "8 8'. fis' `open. 'and' 'water may fl'ow'from `the sto'rage'tanksthrough the strainerl and 'under certain conditions o f opjerationjpasttne regulator I1A into pincet" located above' the condenser and adapted .to allow flow `of wat-er vover the condensing 'surfaces'of'condenser H. Moist air lpassing over the evaporator cous wi11, of course," be condensed in the ventila'ting and.'coolingjuniti and 'such vc'o'r'i'densed moisture' isidrai'ned "from thev lunit' through drain 'pipe4 92v andVV trap '53, with the 'discharge being .made 'either outside of the vehicle ori if desired into thewater storageta'nlsll. In the" previous descriptioninwhich reference washad'to vvarious pipesfvalves' etc., 'of oer'tain'typesit is intendedr that such terms .bein'terpr'eted"broadly Y and ythat piping ras referred ltomeanv by' lany type of connection permittingflowf'andcontrol` of gaseous or liquid refrigerant, while the' 'term fvalve's`will'refer to' any typ'e"'of"'m'echanism"for control of'uid flow.

Referring now to Figure, 3,@ whichjd'isc'loses thel electrical connection' of''the"various'parts4 of the system, it will .bei seen that 'a storage battery 94 has been'provided'preferablyhavingfits lpositive'side grour'ided' and connected4 to ground Wire se.. :die negative eine efv the batteri' is con- `nected,through vsupply `linesSlt to various' parts of the systemand to equipment panel 91. In

order to control starting of the engine an approved type of starting box 98 is provided. This box is formed with contacts 99 adapted to be bridged by contacter and complete a circuit from supply line 96 through the eld winding |0| of starting motor SM which is connected to the ground line 95. The starting box is provided with contactor closing coil |02 connected to the ground line and through circuit breaker |03 to a pair of starting switches |04 'adapted to bridge contacts |05, thus completing the circuit through the coil |02 from the supply line 96 to the ground line. Asrsoon as the coil |02 has been energized by closing of the starting switches contactor |00 bridges contacts 99 supplying cur- -rent to the starting motor and toa coil |06 which operates a choke valve (not shown) on the engine. In completing the circuit to the starting motor and choke operating coil a holding circuit is completed through holding coil |08 which will 'assist coil |02 in holding the vcontactor |00 in contact bridging condition. As soon as the engine has started, it will immediately come up to idling speed causing the generator G to develop full voltage which will be impressed through connection H0 upon kick-out coil ||2 located in the starting box. Energization of this kickout coil will cause release of the contactor |00, thus opening the circuit, through the starting motor and holding coil |08 and causing the starting motor and choke control coil to cease operation. The generator G is of the shunt type having field winding |4 connected to the ground line and to the equipment panel 91 upon which is mounted the customary voltage and current control, by means of which the excitation of the generator is controlled and the amount of current supplied to the storage battery is limited. The controls in the equipment or control panel are so set that when the engine is running either idle or at full speed the generator will develop full voltage for operation of auxiliary equipment and for charging the storage battery.. In order to circulate air from the vehicle spaceV through the evaporator coils a blower motor BM of the series type having field coil ||6 is connected to the ground wire an-d toa contact ||8 located adjacent a contact i9 joined to the supply line 96 and which contacts are adapted to be bridged by a contactor |20. The con-tactor |20 is controlled by coil |22 connected by wire |23 to the ground line and by wire |24 to the negative side of the generator. In this manner 'as soon as the -generator has reached its full voltage output contactor |20 will close completing the circuit and causing the blower motor to operate, thus the blower motor will operate at all times that the prime mover is functioning. Shunt wire |28 is connected to the supply side of the blower motor circuit and to a contact |30 of vehicle thermostat |32 adapted to close when the vehicle temperature is lowered to a predetermined value, thus completing a circuit through the refrigerant control valve FV and closing the same to stop o'w of refrigerant to the evaporator coils. The high and low pressure switch 80 previously referred to is provided with contacts |40, one of which is connected to the ground line, while the other is connected to a coil |42 joined to the shunt supply line |28. Upon closing of contacts |40, due to pressure changes in the pressure switch, a circuit will be completed from supply |20 through coil |42 and contacts to the ground line, thus energizing the coil and causing contactors |44 to bridge the contacts |46 and |41. Bridging of the contacts |46 and |41 will complete a circuit from the supply line |28 to the ground line through the by-pass valve SV and idling control arrangement mounted on the engine adjacent, the carburetor. -Energization of the valve SV and the engine idling control will cause opening of the valve SV permitting iiow of refrigerant between pipes 69 an-d 60, while at the same time causing the engineto return to idling speed. The engine idling control mechanism is so arranged that when no current is iiowing through the coil |50, then the engine throttle will be wide open and the engine operating at full speed. However, as soon as the coil is energized for any reason due to operation of the pressure switch condition, the engine throttle will be promptly moved to an idling position. Ignition current to the engine is provided :by magneto MA by circuits (not shown) and the engine may be stopped when desired by m-oving the starting switches |04 vfrom the starting position to a stopping position in which they bridge contacts causing the magneto to be grounded.

The operation of the system is as follows and assuming the system to be in a shut down condition: Movement of the switches |04 into position to bridge contacts |05 will energize coil |02 moving contactor |00 into position to bridge contacts 99, causing the starting motor to crank the yengine and at the same time hold the choke. in position to supply a rich mixture to the cylinders. As soon as the engine has started to run it will immediately reach at least idling speed causingV the generator to develop full voltage with the result that kick-out coil H2 will trip contactor |00 breaking the circuit to the starting motor and choke control. The engine is now operating at least at idling speed causing the generator to develop rfull voltage which will be supplied through the connections to coil |22 causing contacter |20 to bridge contacts H8 and ||9 and causing blower motor BM to start operation. Operation of the blower motor will cause air to be moved through the evaporator coils in the cooling and Ventilating unit V and this blower motor will operate at all times that the engine is operating at such speed as to cause the gen'- erator to develop full voltage. After long periods of shut down the pressure relation existing between pipes 'I8 and 02 may and usually will be such as to cause the contacts |40 to be opened, therefore, preventing any completion of a circuit to the by-pass valve SV or engine idling control mechanism. The engine, therefore, will immediately upon starting come up to full speed and willcontinue at such full speed until such time as the compressor has pumped suflicient refrigerant to reduce the pressure in the suction line 46 to approximately ten pounds per square inch or any similar predetermined Value. Lowering of the suction pressure will cause the high and low pressure switch to function closing contacts |40, energizing coil |42 and completing through contactors |44 circuits to the by-pass valve SV and engine idling control |48. Energization of the idling control will immediately bring the engine to idling speed, while energization of bypass valve SV will permit refrigerant pumped by the compressor at the idling speed of the engine to circulate through pipes I9, oil separator 22, pipe 69, valve SV, pipe 66 and 60 on the suction side of the compressor'. The engine compressor and blower motor will continue to function with the engine lat'idling speed until such time as the temperature lv'vithin 'the"vehiclereaches a point Warmerthanis desired.

As soon as thevehicle temperatureriseslabeve thedesired level thermostat I32`Will op'enbre'aking the circuit to the refrigerant control valve FV and permitting thel same to 'open-Opening of the refrigerant valveFV w'ill'allbW liquidrefrigerantto floW from the iliquid receiver 36 through pipes 39 andexpansionvalves -44- tothe evaporator coilscausing the coils to be chilled. Chilling of the coils together "Withmovementof the vehicle air thereover by the blower yinotorwill cause the refrigerantl to' pick up the heat lunits from the vehicle air and thisheatedrefrigerant, which is noW in a gaseous state, will floW- from the evaporator coils intosuction line 46 and into the compressor where it Will be compressedy and fed through the high pressureline`-|9 to'l the oil separator and by Wayof pipe' 32 to the condenser H and back to the liquid receiverY in a liquid form. Shortly after the thermostat |32 opens causing refrigerant to be suppliedvto the evaporatorfcoils, the -pressure -Within the suctionline 46 will rise and through `pipe 82 connected to the'highand loW pressure 'switch Will causesuch switch to move breaking contacts |40. Breaking of Y the contacts'vvill,I of course, deen'ergize'coil |42 breaking the circuit to lay-pass valve`SV and engine throttling control |48. Breakage 'of these "circuits will cause theby-pass to closepreventing any further flowof refrigerant thro-ugh the bypass circuits vvhilel at the- Sametime causing the engine to be speeded-up to its 'full speed. With the engine operating at its full speed' 'the compressor will maintain a relatively low suction pressure and Will transfer vthe heated gaseousfrefrigerant from the low pressure'suction lineto the high pressure line for extraction of the heat units in the condenser and return of the refrigerant to the liquid receiver.

As soon as the vehicle temperaturelasv been lowered to the desired degree thermostat|32 will close completing a circuit through control valve `FV and stopping the flow ofliquid 'refrigerant to the expansion valves `44,`buty the f closingof the thermostat will not immediately affect the loperation of the remainder of thesystemfsince the'engine and compressor vwill contin-ue'to operate at full speed until such-time as the suction line pressure in 'pipes 46'fandi82has been reduced to a sumciently Alovv -point as to cause operation of the lhigh and loW pressureswitchm with the result that the contacts'A IMT close', opening the by-pas's and bringing the engine toidljing speed in a manner-as has been-previouslyV described. In case there is 4liquid refrigerant in the line between theexpansion lvalve `andthe control valve FV or in the'evaporatorcoils, such refrigerant will absorb heat andexpand causing the suction line pressure to rise, but' as soon as this'pressure rises contactsv |40 open and the engine speeds up and immediately 4reduces the suction line pressure to th'e`desired loW' level, thus it will be seen that the arrangement is such as to maintain under normal conditions a'deii'nite relation of pressures betweenthehigh andlovv pressure sides of thel evaporator coils. Attention is here directed to thev fact that the check two 'pressure sides existing,l a lowpressuresde i`"ei'it'ending' from' the expansion valves to the' pistonv of the compressorand a higlr pressure side :extendingfrom S the piston of the lcompressor land includingI lthe'fliquid receiver, .condenserV and .oil separator. `vWhenthe system is `operating with the by-pass valve open there lare threepressure areasvexistinggthe' rst of which is a high pressure area. extending from 4the check valve y3f! to the-control valve FV and. including the bulk of thefrefrigerant positioned inthe condenser and receiver. The second of Vthese areas isone of intermediate pressureand may be considered 4the Joy-pass 'circuit and extends from check valve y33 Vto check Valve '-48 and includes therein the compressor, oil separator and by-pass valve SV Which is openpermitting the'pressureson either siderof the compressor piston to be substantially equal, thus unloading the compressor. Thethird of these areas is alow pressure area and extends from'the closed refrigerantcontrol valve FV to the'lcheck valve 48 .and including therein the evaporator coils.

` Under certain conditions of operation it will be found that thelcondenser, which is normally of sufficient capacity to extract the heat units absorbed in the evaporator coils, can no longer function efficiently to condense the gas. supplied to it and under this condition abnormal head pressures will; exist in the condenser compressor. Under 'these conditions of abnormal head pressures the water regulator valve 'll through its connections? 2 and' 16 will open, permitting Water to floWfrom the storage tanks -over the condenser and wetting the cooling surfaces thereof.

Wetting of thecooling surfaces will dueto the evaporative cooling increaseA materially the rate at which heat units may be extracted from the ygaseous refrigerant, thus increasing the condensing capacity of the condenser. In case the Water storage tanks should on a long run be emptied or even neglected and not filled, a condition may arise in which it is impossible to hold down the head pressures-but in case such a condition arises the excessive pressure-Will cause the pressure'svvitch 88 to close the contacts un f loading the compressor and returning the engine to idling speed until such time asthe head pressures have been reduced by condensation in the condenser. Thus it'v'vill be seen thatbypro vision of the high and 10W pressure switch operating'on a differential of pressures in the high and low pressure sides ofthe system any damage to the parts cannot occur, nor can any particularly unbalanced condition of pressures exist as long asthe engine is running and as soon as the engine starts running any unbalanced conditions that might exist are promptly corrected. The use of the high and low pressure switch connected as it is to control the by-pass valve will, together with the check valves, prevent i any excessive pressure ever existing in the evaporator coils `which Were not designed to Withstand'pressure and would be damaged if subjected to an excessive pressure.

eration system anol its operation it will be seen that the compressor has been' more or less directly coupled to the prime mover, permitting the elimination of any clutches or other expensive connections and that the compressor will run at all ti-mes that the prime mover is running. Provisionv of the ley-pass valve permits the compressor tov run idle at such times it is not needed for coolingpurposes or to maintain the proper pressurerelations in the system. By permitting the compressor to run idle when notneede'd an extremely eiiicient operation of the system is attained. The provision of the pressure switch connected into the system in the manner described insures the maintenance of safe pressures in the various component parts of the system and this switch will at the same time permit of increasing the coolingcapacity of the condenser by controlling the Water flow over the condensing surfaces.

While the refrigerating system has been described more or less in detail, it is obvious that various modifications and rearrangements of parts are possible while accomplishing substantially the same results as described. It is, therefore, my intention to utilize all Such modifications and rearrangements of parts as will fall within the scope of my invention and as dened by the following claims.

What is claimed is:

1. In a refrigeration system, the combination of a continuously lrunning prime mover, acompressor connected to said prime mover for operation substantially in unison therewith, a refrigerant circuit connected to said compressor and including a condenser and an evaporator, a by-pass Valve for loading and unloading said compressor, and pressure responsive'means connected to said by-pass valve and operating to control the by-pass valve to provide for loading and unloading of the compressor in'accordance with pressure conditions in said circuit, said pressure responsive means also operating to increase or decrease the speed of the prime mover substantially in unison with the loading or unloading of the compressor.

2. In a refrigeration systenrthe combination of a prime mover, a compressor connected to said prime mover for operation substantially in unison therewith, a. refrigerant circuit containing refrigerant and connected to said compressor and comprising a high pressure side and a low pressure side established by saidV compressor, said high pressure side including a condenser a'nd said low pressure side including an evaporator, a by-pass circuit connecting said high and low pressure sides of the refrigerant circuit and including a by-pass valve for loading and unloading said compressor, and a pressure responsive means connected to said low pressure side and to said high pressure side and operating solely in response to a predetermined differential of pressures in Said sides to control said by-pass valve and by-pass circuit to load and unload the compressor, said pressure responsive means also operating to increase or decrease the speed of the prime mover substantially in unison with the loading or unloading of the compressor.

3. In a refrigeration system, the combination of a prime mover, a compressor connected to said prime mover for operation substantially in unison therewith, a refrigerant circuit containing refrigerant and connected to said compressor and comprising a high pressure side and a low pressure side established by said compressor, said high pressure side including a condenser and said low pressure side including an evaporator, a

by-pass circuit connecting portions of said high and low pressure sides of the refrigerant circuit adjacent the compressor and including a by-pass valve for loading and unloading said compressor, pressure responsive means connected to said low pressure side and to said high pressure side and operating in response to a predetermined differential of pressures in said sides to control said by-pass valve to establish the by-pass circuit and unload the compressor, said pressure Aresponsive means also operating to increase or decrease the speed of the prime mover substantially in unison with the loading or unloading of the compressor, and means preventing the interchange of refrigerant between the by-pass circuit and those portions of said high and low pressure sides which include the condenser and evaporator respectively when the by-pass circuit is established.

4. In a refrigeration system, the combination of a prime mover, a compressor connected to said prime mover for operation substantially in unison therewith, a, refrigerant circuit containing refrigerant and connected to said compressor and comprising a high pressure side and a low pressure side established by said compressor, said high pressure side including a condenser and said low pressure side including an evaporator, a by-pass circuit connecting portions of said high and low pressure sides of the refrigerant circuit adjacent the compressor and including a by-pass valve for loading and unloading said compressor, pressure responsive means connected vto said low pressure side and to said high pressure side and operating in response to a predetermined diiferential of pressures in said sides to control said by-pass valve to load and unload the compressor, said pressure responsive means also operating to increase or decrease the speed of the prime mover substantially in unison with the loading or unloading of the compressor, and automatically operating means preventing the interchange of refrigerant between the by-pass circuit and those portions of said high and low pressure sides which include the condenser and evaporator respectively when the by-pass valve is open and the compressor unloaded.

5. In a refrigeration system, the combination of a continuously running prime mover, a conipressor connected to said prime mover for operation thereby, refrigerant and connected to said compressor, said compressor operating to maintain a high pressure side and a low pressure side in thevcircuit, said high pressure side including a condenser and a refrigerant control valve and said low 'pressure side including an evaporator, a by-pass circuit connecting said high and low pressure sides of the refrigerant circuit and including a bypass Valve for loading and unloading said compressor, a thermostat responsive to temperature changes caused by said evaporator and operating to control said .refrigerant control valve'and the flow of refrigerant to -the evaporator, and pressure responsive means connected to said refrigerant circuit and operating to control the bypass valve to load and unload the'compressor, said pressure responsive means operating irrespective ofthe thermostat to maintain a substantially constantV relation between said high and low pressure sides, said pressure responsive means also operating to increase or decreasejthe speed of the prime mover substantially in unison with the loading or unloading of the compressor.

6. In a refrigeration system, the combination of 'a continuously running prime mover, a compressor connected to said prime mover for operation thereby, a refrigerant circuit charged With refrigerant and connected to said compressor, said compressor operating to maintain a high pressure side and a low pressure side in the circuit, said high pressure side including a condenser and a refrigerant control valve and said low pressure side including an evaporator, a bya refrigerant circuit charged with pass'- circuit connecting said` high and low'pressure sides of the refrigerant circuitand. including a luy-pass valve for loading and unloading said'rcompressor,- a thermostat responsive to temperature changes' caused by said evaporator and operating to control said refrigerant control valve andthe flow of refrigerant to the evaporator', and: pressure responsive means connected to said 'refrigerant circuit and operating to control the by-pass valve to load and unload the compressor, said pressure responsive means .operating independently of the thermostat to 4limit the pressure'in the high pressure side to a safe value and tov increase or decrease the speed of thek primemover Substantially in unison with .the loading and unloading 'of the compressor.:

'7. 1n a refrigeration system', the combination of 'a continuously running prime mover,.a compressor connected to said `prime mover forfoper'- ation thereby, a refrigerant circuit charged With refrigerant' and connected .to vsaid compressor, said compressor' operating tot fmaintain "a thigh pressure side and a low` pressure `side Ainxthe circuit, said high-.pressure side including` atcone denser and a vrefrigerant'control valve and said low-pressure side including an evaporatona bypass circuit connecting saldi high and'loW pressure sides of the refrigerantcircuit and including` a `by-pass valve for loading and unloading said compressor, a thermostat responsive to temperature'changes caused` by said evaporator and operating to control said refrigerant control valveand' the flow of refrigerant to the evaporator, and pressure responsive means connected to said refrigerant circuitV and operating to" control the by-pass. valve to load and unload'the compressorv and to substantially 'simultaneously therewith. increase or. decrease thev speed of the prime. mover,4 said pressure responsive 'means operating. independently ofthe .thermostat to limitthe pressure. in the'. high pressure side to a safe value, and additional pressure .responsive meansconnected to the high pressure side and operating to reduce the'pressure in the high pressure side as' value.y

8. Inza refrigeration system, the-combination of acontinuously running prime mover, a compressor connected to said primev mover for operation thereby, a refrigerant circuit charged With refrigerant and'connected' to said compressor, said compressor operating vto maintain a high pressure side and a `lovv pressure side in the circuit, said high pressure side including a condenser anda refrigerant control Valve and said low pressure side including anevaporator, a bypass circuit connecting said high and low pressure sides of the refrigerant. circuit and including a by-pass Valve for loading and unloading said compressor, a thermostat responsive to temperature changes caused by said 'evaporator and operating to control said refrigerant control valve and the flow-of refrigerant to the evaporator, and pressure responsive means connected to said refrigerant circuit vand operating to control the by-pass valve to load and unload Vthe compressor and'to substantially simultaneously therewith initV approachesthe limiting safe Cal the system.v

creasexor decrease thespeed ofthe prime mover, said pressure responsive means operating indee pendently of the thermostat to limitthe pressure in the high pressure side toa safe value, `and ad ditional pressure responsive meansconnected to the high pressure side and operating to :reduce the pressure inthe high pressure side as it approaches the limiting safe value, said additional pressure responsive means increasing the` cooling effectzof the condenser by causing Water to flow thereover'.

9. In a refrigeration system, the-combination of Tan evaporator, a condenser, a prime mover, a compressor connected to said prime-mover for operation substantially in unison therewitlna refrigerant circuitY containing refrigerant and connected to said compressor andvcomprising a high pressure side and a low pressure sidetestablished by said compressor, said high pressure side extending from the compressorto the evaporator and .including the condenser and said loW'pressure vside extending from the compressorto'and including said evaporator, a by-pass: circuit'including the compressor and portionsV of said high and low pressure sides -of the refrigerant circuit adjacent the compressor and also.A including a by-pass' valve for controlling the oy-passcircuit thereby loading or unloading the compressor, pressure responsive means connectedto said low pressure side adjacent the evaporatorl and to said high pressure -side adjacent the compressonsaid pressure responsive means operating in response to' a predetermined.differential of pressures vin said sides toY control the operationof saidbypass valve, and independent means insaid high and `low. pressure sides preventing lthe interchange, ofl refrigerant between theby-pass circuit andthe 'condenser or evaporator .when the by-passcircuitis established, the means in said highpressure sidebeing located between the condenserand the connection. of ,the lpressure resp'onsivemeans to the high pressure side whereby said pressure responsive 4means iszsubjectat all times tothe pressure'existing in the high pressure side' adjacent the compressor.

10. In arefrigeration system, the combination of an evaporator-,a condenser, a'primemover; a compressorv lconnected tol said primemover for operationsubstantially in; unisonxtherevvith, a refrigerant .circuit containing Irefrigerant and connected to said compressor and comprising a high pressure side anda low pressure lside established by said compressor, said high pressure side extending from the compressor to the. evaporator and including the condenser, and said low pressure side extending from the compressor to and including-said evaporator, and means vfor establishing under predetermined conditions angintermediate pressure `circuitV includingfthe compressor and portions of the high and low pressure sides adjacent thereto, said means including a by-pass valve for connecting saidhigh and loW pressure sides and check valves for isolating said intermediate pressure circuit. from the remainder'of the high and low pressure sidesY of HERBERT D. EUWERz

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