US2218944A - Refrigerating apparatus - Google Patents

Refrigerating apparatus Download PDF

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Publication number
US2218944A
US2218944A US172881A US17288137A US2218944A US 2218944 A US2218944 A US 2218944A US 172881 A US172881 A US 172881A US 17288137 A US17288137 A US 17288137A US 2218944 A US2218944 A US 2218944A
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US
United States
Prior art keywords
pressure
switch
motor
compressor
low
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US172881A
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English (en)
Inventor
Edward R Wolfert
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Westinghouse Electric Corp
Original Assignee
Westinghouse Electric Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Westinghouse Electric Corp filed Critical Westinghouse Electric Corp
Priority to US172881A priority Critical patent/US2218944A/en
Priority to FR845348D priority patent/FR845348A/fr
Priority to DE1938W0104497 priority patent/DE695391C/de
Priority to GB31951/38A priority patent/GB518055A/en
Priority to CH208233D priority patent/CH208233A/fr
Application granted granted Critical
Publication of US2218944A publication Critical patent/US2218944A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • A—HUMAN NECESSITIES
    • A22—BUTCHERING; MEAT TREATMENT; PROCESSING POULTRY OR FISH
    • A22B—SLAUGHTERING
    • A22B5/00—Accessories for use during or after slaughtering
    • A22B5/06—Slaughtering stands or spreaders for cattle
    • A—HUMAN NECESSITIES
    • A22—BUTCHERING; MEAT TREATMENT; PROCESSING POULTRY OR FISH
    • A22C—PROCESSING MEAT, POULTRY, OR FISH
    • A22C17/00—Other devices for processing meat or bones
    • A22C17/02—Apparatus for holding meat or bones while cutting
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B49/00—Arrangement or mounting of control or safety devices
    • F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
    • F25B49/025—Motor control arrangements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/19—Pressures
    • F25B2700/193—Pressures of the compressor
    • F25B2700/1931—Discharge pressures
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/19—Pressures
    • F25B2700/193—Pressures of the compressor
    • F25B2700/1933—Suction pressures
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/21—Temperatures
    • F25B2700/2104—Temperatures of an indoor room or compartment
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/21—Temperatures
    • F25B2700/2117—Temperatures of an evaporator

Definitions

  • Another object of the invention is to provide an improved refrigerating system of the compression type which may be operated without unloading during the starting operation.
  • a further object of the invention is to prevent the starting of a refrigerant compressor during periods when the pressure difierence between the gas inlet and the outlet thereof exceeds a predetermined value.
  • a still further object of the invention is to provide an improved protective device for a refrigerant compressor wherein operation of the latter is terminated in response to an excessive head pressure and to a relatively low section pressure, and wherein starting of the compressor is prevented when the difference between the head and suction pressures exceeds a predetermined value.
  • the single figure of the drawing is a diagrammatic view of a refrigerating system controlled in accordance with my invention.
  • a refrigerating system including an evaporator H) for abstracting heat from the media to be refrigerated, a compressor II and a condenser l2, the latter being cooled in any suitable manner such as, for example, by water.
  • the compressor ll may be directly driven by an electric motor l3 and is preferably of the enclosed type; the motor l3 being enclosed by a casing l4 secured to the compressor ll.
  • Refrigerant vaporized at relatively low pressure in the evaporator I0 is withdrawn through a conduit l5 by the compressor II and is compressed to a relatively high pressure and delivered to the condenser l2 through a conduit Hi.
  • the compressed vapor is cooled by a water cooled coil l1 and is condensed.
  • the cooling water enters the coil at l8 and is discharged at IS.
  • a valve 20 may be disposed in the water circuit for controlling the flow of cooling water and may be controlled in any well known manner. Preferably, the flow of cooling water is controlled in accordance with head or condens-' ing pressure.
  • the condenser 12 to the evaporator l0 through a conduit 2
  • the device 22 is a conventional thermostatic expansion valve and controls the flow of refrigerant to the evaporator ID in response to a predetermined value of the superheat in the vapor discharged from the evaporator III.
  • the refrigerating system disclosed may be employed for cooling any medium, but the evaporator which I have disclosed is employed for cooling a gas such as air and is provided with fins 23 for increasing its heat transfer surface.
  • a fan 24 may be used for effecting forced circulation of the air over the evaporator l0.
  • a device diagrammati cally shown at 25 which also functions in accordance with my invention, to prevent starting of the motor l3 at times when the pressure differential between the high and low pressure sides of the system exceeds a predetermined value. Starting of the motor and compressor is, therefore, effected only when the load is at or below a predetermined value. Accordingly, the system may be operated without an unloader and without providing a driving motor having a capacity greater than that necessary for running. A description of the control device 25 will now be given.
  • the device 25 includes a normally closed switch 26, that is actuated by either of a pair of pressure responsive bellows 21 and 28.
  • the bellows 21 is connected by a tube 29 to the pressure conduit l6 defining a portion of the high side of the system and the bellows 28 is connected by a tube .3l to the low side of the system and preferably to the suction conduit IS.
  • the switch 26 may include a pivoted arm 32 connected by a snap acting spring 33 to a pivoted switch arm 34, the latter carrying a movable contact 35 that engages a stationary contact 38 in the closed position of the switch.
  • a stop 31 limits movement of the switch arm 34 in opening direction.
  • the main pivoted arm 32 is biased in switch closing direction by a spring 38 and a stop 39 is provided for limiting movement of the arm 32 in this direction.
  • Upward movement of the main pivoted arm 32 is eiTected by a rod 4
  • a lost motion connection is provided between the rod 6
  • may move upwardly and downwardly without actuating the switch 26 but when the pressure is depressed to an abnormally low value, the rod 4
  • a second rod 45 includes a slot 46 within which a second projection 41 on the lever 32 is disposed.
  • the rod 45 is connected to a bell crank 48 that is actuated by the bellows 21.
  • the switch 26 is unaffected by movement of the bellows 21 due to the lost motion provided by the connection between the projection 41 and slot 46.
  • the projection 41 is engaged by the rod 45 and the switch is moved to its open position.
  • opening of the switch 26 due to abnormally high head pressure or low evaporator pressure stops operation of the compressor.
  • Adjustment of the pressures at which the bellows 21 and 28 operate the switch 26 may be provided by adjustable springs 5
  • a second switch 53 is provided in the device and is actuated conjointly by the bellows 21 and 28 and which is closed only when the difference in pressures between the high and low sides is below a predetermined value.
  • the switch includes relatively movable contacts 54 and 55, the first of which moves with movement of the bellows 21 and the second of which is actuated by the bellows 28.
  • the contact 54 is carried by a support 56 that may be secured to the bell crank 48 and movable therewith.
  • the contact 55 is carried by a spring 51 forming a part of the pivoted lever 58 that is actuated by the bellows 28 and bell crank 42.
  • One end 59 of the lever 58 is held in engagement with the bell crank 42 by means of a spring 6
  • the various elements that actuate the contacts 54 and 55 are so proportioned that the contacts are separated when the pressure differen- -tial between the high and low sides of the system exceeds a predetermined value, such as for example, 50 lbs.
  • a predetermined value such as for example, 50 lbs.
  • the contacts 54 and 55 engage.
  • 3 may be started only when'the contacts 54 and 55 of the switch 53 are engaged.
  • the switches 26 and 53 are connected in series in a control circuit including a conductor 53 energized from a suitable power source represented by line conductors Ll and L2.
  • a suitable power source represented by line conductors Ll and L2.
  • and L2 define a power source of relatively low potential.
  • the conductor 63 is connected to the operating coil 64 of a relay 65, the latter including a main switch 66 and a control switch 61 that is connected in parallel with the switch 53 by a conductor 68.
  • Energization of the coil 64 eiTects closing of the switches 66 and 61, and, conversely, deenergization of the same effects opening of the switches 66 and 61.
  • the switch 65 is connected in the motor circuit 1
  • Starting and stopping of the compressor motor l3 may be effected by a master switch 12 preferably thermostatically operated and conneeted in the control conductor 63.
  • the switch 12 When thermostatically actuated, the switch 12 may be operated in response to the temperature of the media being refrigerated or to the temperature of the evaporator l6 in a manner well understood in the art.
  • the master switch 12 is closed and opened in response to predetermined high and Operation As shown in the drawing, the master switch 12 is open, so that the compressor and motor
  • the switch 26 is closed as the head pressure and the evaporator pressure are respectively below and above the values at which this switch 26 is opened,
  • the switch 53 is closed which indicates that the pressure differential between the high and low sides of the system is below 50 lbs. Accordingly, the system is in condition for operation when called upon by the master switch 12.
  • the thermostatically operated master switch 12 When the temperature of the air being treated and circulated by the fan 24 has increased to predetermined value, the thermostatically operated master switch 12 is closed and thereby energizes the control circuit including the line con ductor L--
  • Operation of the compressor depresses the pressure and temperature of the refrigerant in the low side of the system including the evaporator 23 and the suction conduit l5.
  • the pressure in the high side of the .system is raised, which high side includes the pressure conduit I6, condenser l2 and the liquid supply conduit 2
  • Evaporation of refrigerant is effected in the evaporator 23 under control 01' the thermostatically operated expansion valve 22 so that the air translated by the fan 24 is depressed in temperature.
  • the reduction in pressure on the low side of the system contracts the bellows 28 so that the bell crank 42 is moved counter-clockwise and the lever 58 is moved clockwise by the bias of the spring 6 I.
  • the contact is therefore moved downwardly and away from contact 54. Opening of the switch 53 does not affect deenergizing of the control circuit as the latter is maintained closed by the switch 61.
  • Operation of the compressor H continues until the temperature of the media being cooled has been depressed to a predetermined value at which time the master switch 12 is opened for deenergizing the control circuit. Accordingly, the relay 65 opens its main switch 66 and control switch 61 so that operation of the compressor H and its driving motor l3 are terminated.
  • the contacts 54 and 55 are moved in closing direction and, when the pressure difi'erential between the high and low sides has been depressed to 50 lbs. the contacts 54 and 55 are engaged for conditioning the system for the starting operation.
  • the system may be operated without an unloading device and without providing a motor having a capacity substantially .above the capacity necessary for running operation.
  • the protection device 25 is constructed as a unit and employs the same pressure responsive elements for actuating both switch structures 26 and 53. I have shown the switch 26 actuated by both bellows 21 and 28 but it will be understood that these pressure responsive elements may operate switching means other than that shown at 26.
  • Refrigerating apparatus comprising a high pressure and a low pressure side, means for circulating refrigerant through the high and low pressure sides and means responsive to a predetermined high differential in pressure between the high and low pressure sides for rendering said circulating means incapable of being started, said diiferential pressure responsive means being inefiective to control the circulating means during active periods thereof.
  • Refrigerating apparatus comprising an evaporator, a condenser, means for circulating refrigerant through the evaporator and condenser, a motor for driving the circulating means and means responsive to a predetermined high difference in pressure between the condenser and evaporator for rendering the motor incapable of being started, said last-mentioned means being ineffective to terminate operation of themotor during operating periods thereof.
  • Refrigerating apparatus comprising a condenser and evaporator defining portions of the. high and low pressure sides of the apparatus respectively, a compressor for translating refrigerant through thehigh and low pressure sides, a motor for driving the compressor, a switch for controlling energizationof the motor, means redeenergization and the energization .of the motor respectively.”
  • Refrigerating apparatus comprising a condenser and evaporator defining. portions of the high and low pressure sides of the apparatus, respectively, a compressorffor translating refrigmotor for driving, the compressor a switch adapted to prevent energization ofnthe motor while it is'dee'nergized, means operable in response to. a predetermined maximum difference .70 erant through the high and low pressure sides, a
  • Refrigerating apparatus comprising a high pressure side and a low pressure side, means for translating refrigerant through the high and low pressure sides, means responsive. to predetermined high and low pressures in the high and low sides, respectively, for rendering the refrigerant translating means inactive and means effective during inactive periods of the translating means and responsive to a predetermined high difference in pressure between the high and low sides for preventing the starting of the translating means.
  • Refrigerating apparatus comprising high and low pressure sides, means for translating refrigerant through the high and low pressure sides, electrical means for actuating the refrigerant translating means, means responsive to predetermined high and low pressure in the high and low sides, respectively, for deenergizing the electricaI means and means responsive to a predetermined high difference in pressure between the high and low pressure sides for preventing energization of the electrical means during inactive periods thereof.
  • Refrigerating apparatus comprising high and low pressure sides, a compressor for translating refrigerant through the high and low pressure sides, a motor for driving said compressor, switching means for controlling energization of the motor, means responsive to predetermined high and low pressures of the high and low sides, respectively, for opening the switching means, a second switch controlling energization of the motor, means responsive to a predetermined high difference in pressure between the high and low sides for opening .said second switch, and means effective during operating periods of the motor for rendering said second switch incapable ofcontrolling energization of the motor.
  • an evaporator for compressing refrigerant vaporized in the evaporator at relatively low pressure, a condenser for liquefying the compressed refrigerant at relatively high pressure, a motor for driving the compressor, a switch for controlling energization of the motor and opened in response to predetermined high and low pressures of the compressed and vaporized refrigerant, respectively, a second switch connected in series with said first mentioned switch and opened in response to a predetermined high difference in pressure between the compressed and vaporized refrigerant, and a third switch connected in parallel with the second switch and closed during periods when the motor is energized.
  • an evaporator for compressing refrigerant vaporized in the evaporator at relatively low pressure, a condenser for liquefying the compressed refrigerant at relatively high pressure, a motor for driving the compressor, first and second pressure responsive elements responding, respectively, to the pressures of the compressed and vaporized refrigerant, switching means for controlling energization of the motor and actuated by either of said first and second elements to its open position in response to predetermined high and low pressures of the compressed and vaporized refrigerant, respectively, a second switch connected in series with said switching means and actuated conjointly by the pressure responsive elements to its open position in response to a predetermined high difference in pressure between the compressed and vaporized refrigerant and a third switch connected in parallel with the second switch and opened and closed during periods when the motor is deenergized and energized, respectively.
  • Refrigerating apparatus comprising an evaporator, a compressor for withdrawing relatively low pressure vapor from the evaporator and for compressing the same to a relatively high pressure, a condenser for liquefying the high pressure vapor, a motor for driving the compressor, a normally closed switch for controlling energization of the motor, an element responsive to the pressure of the compressed refrigerant and connected to said switch for opening the same in response to a predeterminedhigh pressure of the compressed refrigerant, a second element responsive to the pressure of the low pressure vapor and connected to said switch for opening the same in response toa predeterminedlow pressure of the low pressure vapor, a second switch connected in series with the first switch, and actuated conjointly by both of said pressure responsive elements, said second switch being open when the difference in pressures between the high and low pressure vapor exceeds a predetermined value, and a third switch connected in parallel with the second switch and opened and closed in response to deener'gization and energization of the motor respectively.
  • a motor compressor unit including a compressor for. translating fluid from a; region oflow pressure to a region of high pressure and an electric motor for driving the compressor.
  • a first switch for normally controlling energization of the motor
  • a second switch adapted to prevent energ'ization of the motor independently of the action of the first switch
  • means responsive to a high difference between the pressures in said high and low pressure regions for controlling said second switch to prevent energization of the motor
  • a motor compressor unit including a compressor for translating fluid from a region of low pressure to av region of high pressure and an electric motor for driving the compressor, first means for normally controlling the starting and stopping of the motor compressor unit, and second means operable in response to-a predetermined maximum diflerence between the pres-' sures in said high and lowpressure regions to prevent starting of the unit, independently of the action of said first means, but permitting starting in response to a lower diflerence in said pressures and permitting the unit to continue to operate, once it is started, to provide a pressure difference greater than said predetermined max imum pressure difference.
  • the method of controlling the operation of a motor compressor unit including a compressor operable to translate fluid from a region of low pressure toa region of high pressure and an electric motor for driving the compressor, which method comprises normally controlling energization of the motor in response toa load condition of the unit but delaying starting ofthe unit, when the unit is idle and the diflerence between the pressures in said high and low pressure regions is high, until said difference is reduced to a predetermined low value, continuing operation of the motor compressor unit, once it is started, independently of increase in said pressure difference above said predetermined'low value, and terminating operation of the unit in response to said load condition.
  • a motor compressor unit including a compressor for translating fluid from a region of low pressure to a region of high pressure and an electric motor for driving the compressor, first and second elements responsive to the pressures in said high and low-pressure regions, respectively, means controlled by one 01' said pressure-responsive elements and arranged to prevent operation of the unit when the pressure imposed on the associated pressure-responsive element reaches a predetermined value, and means actuated conjointly by both of said pressure-responsive elements for eil'ecting a control of the operation of the unit in response to the difference between the pressures imposed on said pressure-responsive elements.

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  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Food Science & Technology (AREA)
  • Wood Science & Technology (AREA)
  • Zoology (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Devices That Are Associated With Refrigeration Equipment (AREA)
  • Air Conditioning Control Device (AREA)
  • Control Of Positive-Displacement Pumps (AREA)
US172881A 1937-11-05 1937-11-05 Refrigerating apparatus Expired - Lifetime US2218944A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
US172881A US2218944A (en) 1937-11-05 1937-11-05 Refrigerating apparatus
FR845348D FR845348A (fr) 1937-11-05 1938-10-29 Appareils réfrigérateurs
DE1938W0104497 DE695391C (de) 1937-11-05 1938-11-03 Kompressionskaeltemaschine
GB31951/38A GB518055A (en) 1937-11-05 1938-11-04 Improvements in or relating to refrigerating apparatus
CH208233D CH208233A (fr) 1937-11-05 1938-11-04 Installation frigorifique.

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US172881A US2218944A (en) 1937-11-05 1937-11-05 Refrigerating apparatus

Publications (1)

Publication Number Publication Date
US2218944A true US2218944A (en) 1940-10-22

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ID=22629584

Family Applications (1)

Application Number Title Priority Date Filing Date
US172881A Expired - Lifetime US2218944A (en) 1937-11-05 1937-11-05 Refrigerating apparatus

Country Status (5)

Country Link
US (1) US2218944A (fr)
CH (1) CH208233A (fr)
DE (1) DE695391C (fr)
FR (1) FR845348A (fr)
GB (1) GB518055A (fr)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2521247A (en) * 1941-01-13 1950-09-05 Honeywell Regulator Co Control of refrigeration
US2998707A (en) * 1960-03-22 1961-09-05 Westinghouse Electric Corp Control apparatus and method for heat pumps
US3110160A (en) * 1963-01-03 1963-11-12 Trane Co Refrigeration system control
US3435628A (en) * 1967-05-02 1969-04-01 Penn Controls Pressure responsive safety control for motor driven compressor
US4220013A (en) * 1978-06-05 1980-09-02 Borg-Warner Corporation Pressure compensated control for air conditioning system or heat pump
US4221116A (en) * 1978-06-05 1980-09-09 Borg-Warner Corporation Temperature compensated control for air conditioning system or heat pump
US4311497A (en) * 1978-03-06 1982-01-19 Robertshaw Controls Company Method and apparatus for heat pump system protection
US20080310966A1 (en) * 2007-05-31 2008-12-18 Hitachi, Ltd. Scroll type booster

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1029013B (de) * 1956-02-17 1958-04-30 Carrier Corp Kuehlanlage
DE102021211728A1 (de) 2021-10-18 2023-04-20 Volkswagen Aktiengesellschaft Betrieb eines elektrischen Verdichters mit optimiertem Startstrom

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2521247A (en) * 1941-01-13 1950-09-05 Honeywell Regulator Co Control of refrigeration
US2998707A (en) * 1960-03-22 1961-09-05 Westinghouse Electric Corp Control apparatus and method for heat pumps
US3110160A (en) * 1963-01-03 1963-11-12 Trane Co Refrigeration system control
US3435628A (en) * 1967-05-02 1969-04-01 Penn Controls Pressure responsive safety control for motor driven compressor
US4311497A (en) * 1978-03-06 1982-01-19 Robertshaw Controls Company Method and apparatus for heat pump system protection
US4220013A (en) * 1978-06-05 1980-09-02 Borg-Warner Corporation Pressure compensated control for air conditioning system or heat pump
US4221116A (en) * 1978-06-05 1980-09-09 Borg-Warner Corporation Temperature compensated control for air conditioning system or heat pump
US20080310966A1 (en) * 2007-05-31 2008-12-18 Hitachi, Ltd. Scroll type booster
US8784067B2 (en) * 2007-05-31 2014-07-22 Hitachi, Ltd. Scroll type booster

Also Published As

Publication number Publication date
GB518055A (en) 1940-02-15
CH208233A (fr) 1940-01-15
DE695391C (de) 1940-08-23
FR845348A (fr) 1939-08-18

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