US 2130093 A
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3 Sheets-Sheet l C. F. KETTERING REFRIGERATING APPARATUS Flled March 28, 1936 55555 nonno onunn Sept E3, H93.
2130 9 D 13 1938 c. F. KETTERING 0 3 REFRGERTING APPARATUS Filed March 28, 1936 3 Sheets-Sheet 2 INVENTOR.
Sep E3 1938 c. F. KETTERING REFRIGERATING APPARATUS Filed March 28, 19256 3 Sheets-Sheet 3 INV ENTOR.
ATTORNEYS Patented Sept. 13, 1938 i mi i. .i
2,130,093 REFRIGERATING APPARATUS Charles F. Kettering, Dayton, Ohio, assigner to General Motors Corporation, Dayton, Ohio, a corporation of Delaware Application March 28, 1936, Serial N0. 71,498
This invention relates to refrigerating apparatus and more particularly to refrigerant air conditioning means and control means therefor.
'Ihis application is a continuation in part of application Serial No. 583,878, led December 30,
Heretofore, air conditioning means have been largely controlledv by the temperature ofthe air. However, in many ways and for many purposes 0 such a control has been found deficient.' For example, for many industrial processes it is required that not only the temperature but also the humidity be kept constant. For air conditioning for comfort purposes it is desirable that the temperature vary to a certain extent according to variations in outside temperature and it is further desirable to provide a lower relative humidity at high temperatures and a higher relative hu-v midity at low temperatures. n
It is an object' of my invention to provide means for starting and stopping a refrigerant air conditioning system according to' predetermined limits of humidity, either with or without a correlated temperature control.
Heretofore humidity control means havebeen very delicate, and/expensive and yet not always sumciently sensitive. It is another object of my invention to provide a humidity control means for a refrigerant air conditioning system which is reliable, durable and inexpensive.
It is another object of my invention to provide an extremely sensitive controlling device wherein little power is required to initiate and govern its operation and in which relatively heavy electric current can be controlled by the use of a simple reliable and novel relay apparatus.
Another object of my invention is to provide an improved electrical humidity control mechanism for refrigerant air conditioning apparatus employing a Wheatstone bridge circuit and wet and dry bulb resistance thermometers in theA arms of the bridge circuit.
Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of the Fig. 4 is a diagrammatic view of an air conditioning apparatus of the compression type together with another form ofimproved humidity control apparatus;
Fig. 5 is a plan view of a form of my improved 5 portable refrigerant dehumidifying air conditioning apparatus including the humidity control apparatus of Fig.. 4; and
Fig. 6 is an elevational view of the apparatus shown in Fig. 5. m
Briefly, in Figs. 1 to 3 inclusive, there is shown a refrigerant air conditioning system of the compression type in which the liquefying apparatus' is located outside of the room and the evaporating means as well as the humidity control means'- 5 is located within the room. The humidity control means includes a. humidity responsive paper strip for actuating a switch means which in turn operates a motor relay which in turn controls the starting and stopping of the motor-compressor unit according to humidity conditions within the room. In Fig. 4 a somewhat similar air conditioning system is shown wherein the vcontrol employs a Wheatstone bridge circuit having a 'wet and a dry bulb thermometer in two arms 25 .pressor unit, condenser and evaporator which is 35 placed within the room merely to remove the moisture therefrom without cooling the room.
Referring to the drawings and more particu-` larly to Fig. 1, there is disclosed a refrigerant dehumidifying apparatus comprising a cabinet 20 40 located within a. room 2| to be cooled and dehumidied. Within the cabinet there is provided a refrigerant evaporating means 22 over the surfaces of which the air in the room is circulated by means of a centrifugal fan 23 located in the 45 lower portion of the cabinet 2U. The centrifugal fan 23 draws air from the-interior of the room and circulates the air over the surfaces of the evaporator 22 after which the air is discharged through a grilled opening 24 in the top of the 50 cabinet 20. 'I'he refrigerant evaporating means 22 is supplied with liquid refrigerant by the refrigerant liquefying apparatus which draws refrigerant vapor from the evaporating means through the suction conduit 26, compresses the vapor and forwards the compressor vapor to a condenser 21 where the vapor is liqueed and collected in a receiver 23. From the receiver 28 the liquid refrigerant is forwarded through a supply conduit 29 under.the control of a suitable expansion valve 39 to the evaporating means 22.
The compressor 25 is driven by an electric motor 35 which is supplied with electric energy through the electric. conductors 35 and 3l. In order to control the operation of the dehumidifying apparatus, and, in particular, the operation of the electric motor 35, I provide a control member 33, preferably of the sealed mercury type, which when tiltedvin one direction closes the circuit to the electric motor and which when tilted in the opposite direction opens the electric circuit. The tilting of the mercury tube control member 39 is controlled by a small high resistance electric clock winding motor 39 whose operation is controlled by a humidity responsive means 40. This humidity responsive means 40 is necessarily located in the room 2|, the humidity of which it is desired to control and is preferably located at some point which will indicate the average humidity condition of the room.
This humidity responsive means comprises a base upon which a long paper strip 4| is coiled. 'Ihis paper strip is connected to a pin 42 mounted in the base at one end and to a lever 43 at its opposite end. 'I'his lever 43 preferably extends downwardly from its pivot so that the paper strip when it changes ,its length in accordance with changes in humidity is not required to overcome the force of gravity in order to operate the lever. 'Ihe lever is provided at its lower end with a switch contact 44 which cooperates with a stationary contact 45 mounted upon the base. Contacts and 45 are connected in series with the electric motor 39 in the electric circuit 46 which is connected in parallel with the electric motor 35. f
Referring now more particularly to Figs. 2 and 4 3 for the detailsof the control member 33, and
its actuating means, there is shown a generally rectangular base l provided with a removable cover 5| having a plurality of windows 52 in its lower portion for disclosing the position of the mercury tube contact member 3l. Mounted upon the base 59 beneath the cover 5| is the small high resistance electric clock winding mo- -tor 33. The resistance of the clock is suillcient to prevent injury to the winding'even when the motor is stalled for long periods of`time. The electric clock winding motor 39 is supplied with electric energy through the electric conductors 52 and 53 which form a part of the electric circuit 45. 'I'he electric motor 33 is mounted upon Dedestals 54 which support the motor but hold it spaced from the base. The motor shaft 55 extends froml the motor toward the base and has its end extending into va'bearing within the base The portion ofthe motor shaft 55 between the motor proper and the base is provided with a pinion 53 which meshes with a gear 51 carrying a pinion 53 which in turn meshes with a sector gear or rack 59 which is mounted upon a shaft 3l,A which is mounted at one end in the base Il and at the opposite end in the frame member 3|. Supported upon the sector gear Il is a clip 52 having four prongs which engage the mercury tube contact member 33. The mercury tube contains a globule of mercury 53 and a pair of contacts 54 which are in series with the electrical conductor 33. The base is provided with a stream of air over the evaporator |25.
stop pins 55 and 55 which engage the sector gear and limits its rotation in either direction. y When the contacts 44 and 45 are in open position and no electric energy is supplied to the high resistance electric motor 39, the spring 51 urges the sector gear 59 in a counterclockwise direction and holds it against the stop pin 55. When the contacts 44 and 45 close, the clock winding motor 39 is energized to cause the sector gear to be moved in a clockwise direction to a position against the stop 55 against the tension of the spring 51. This completes the circuit through the electric motor 35 and causes the refrigerant liquefying apparatus to operate. 'I'he electric motor 99 remains energized so long as the contacts 44 and 45 remain closed and continues to hold the sector gear 59 against its stop pin 86 to hold the mercury tube control member in its extreme clockwise position so that the globule of mercury 59 will bridge the gap between the set of contacts 54. thus completing the electric circuit.
When the room 2| has been suillciently dehumidified, the contacts 44 and 45 will separate, causing the clock winding motor 39 to de-energize. This will permit the spring 5l to return the sector gear 59 to its initial position against the stop pin 55. In returning the sector gear to its'initial position, the train of gears and the motor is rotated. It is therefore necessary that the clock winding motor and the train of gears l evaporator |25. 'I'he refrigerant evaporates un der reduced pressure in the evaporator |25 and is returned to the .compressor through the return conduit |25. The compressor |20 is driven by a suitable electric motor |21 through pulley and belt means |29. The evaporator |25 is preferably positioned within the room to be conditioned or in communicationwith'the room or place to be conditioned.
The refrigerant liquefying apparatus, comprising a compressor, a motor for driving the compressor, and a condenser may be placed in the room to be conditioned or it may be placed outside of the room to be conditioned and connected to the evaporator through the supply and re-` turn conduits |23 and |25. For the purpose of increasing the amount of air passing over the heat transfer .surfaces of the evaporator |25 a fan |33 driven by an electric lmotor |3| provided within a duct |32 is employed for blowing 'I'he evaporator |25 cools the air, and if desired will dehumidify the air by cooling the air below its dew point, causing moisture to collect upon the evaporator |25 and to run down the surfaces of the evaporator |25 and collect in the catch pan |33, from which the condensed moisture will pass through a conduit |34 to a cup |35, which is kept supplied with water thereby, and from which point'the excess is conducted to drain through the conduit |35.
An improved electrical control apparatus is provided for controlling the operation of this air conditioning apparatus. This control apparatus is applicable to any form of apparatus which. changes the amount of humidity in air or any other gas.' In this electrical control apparatus there is provided a Wheatstone bridge circuit generally designated by the reference character it@ having a dry electrical resistance thermometer |41, preferably non-inductively Wound, in one of the arms of the bridge circuit, a Wet resistance thermometer |42 in another arm of the bridge circuit, and adjustable resistances 143 and E45 in the other Aarms of the bridge circuit. The wet resistance thermometer |42 as well as the adjustable resistances |43 and |44 are also preferably non-inductively wound so that alternating current, if desired, may be used for energiaing the Wheatstone bridge circuit. The bridge circuit is supplied with electric current by the electric conductors |48 and |49 which are connected to both ends of the bridge circuit, the conductor G48 being connected between the wet and dry resistance thermometers |42 and |4| while the conductor |49 is connected between the adjustable resistances |43 and |44. 'I'hese elec-- tric conductors H48 and |49 may be supplied with direct current or with alternating current' of a suitable voltage. If desired, alternating current supplied from a transformer connected to the main circuit or any suitable source of alternating current may be used for supplying the current necessary for the use of the Wheatstone bridge circuit.
The Wet resistance thermometer |42 is provided with a stockinet |45 covering its surface and a. wich |46 which dips into the water within the cup it. and supplies moisture to the stockinet- |45. Both the wet resistance thermometer |42 and the dry resistance thermometer |4| are placed within the duct means |32 so that the air which is drawn through the duct by the fan |30 is drawn over the surfaces of these two thermometers before it is blown over the surfaces of the evaparator |25. The dry resistance thermometer |4| will therefore be responsive to the dry bulbn thermometer temperature of the air in the place to be conditioned and the wet resistance thermometer |42, by reason of the evaporation of moisture in the stockinet caused by the air passing thereover, will be responsive to the wet bulb temperature of theair in the room or place conditioned. A normally .closed relay |41 is connected to the sides of the Wheatstone bridge circuit between the dry resistance ther' mometer 64I and the adjustable resistance |43 on one side and between the wet resistance thermometer |42 and the adjustable resistance |44 on the other side.
It is often desirable to operate the apparatus so as to maintain the proper relative humidity at dierent temperatures. This desired relative humidity will depend upon the particular-purpose for which the air is to be conditioned; For
and dry resistance thermometers may be made of substantially the same kind of wire and the resistances |43 and |44 are adjusted to be substantially equal. With the bridge circuit arranged in such a manner when the humidity reaches approximately 100%, the temperature of the dry resistance thermometer |4I and the wet resistance thermometer |42 will be substantially the same since very little evaporation will take place from the stockinet. Under these conditions the current owing through the relay |41 will be at a minimum and the relay contacts will be permitted to move to closed circuit position.
If it is desired to maintain a certain Wet bulb depression of temperature throughout theA range of temperatures the resistances |43 and |44 may be adjusted to make the current ilowing through the relay |41 at a minimum permitting the relay to close when the minimum wet bulb depression has been reached.- Under these conditions the resistance |44 will be adjusted to have a lower value than the resistance |43. From the table compiled below it will be seen that a constant Wet bulb depression does not give a constant relative humidity.
Percent relative humzdzty v F. de- 10 F. de- 15 F. de- D' B' temperature pression pression pression Percent Percent Percent If it is desired to have a constant relative humidity the dry resistance thermometer |4| and the wet resistance thermometer|42 are made of different materials so that the electrical resistance of the resistance thermometer |42 increases more rapidly with increase in temperature than with electrical resistance of the dry resistance thermometer |4|. For example, suchan eiect can be, obtained by using copper wire in' the wet resistance thermometer |42 and German silver wire in the dry resistance thermometer |4I, since the resistance of copper per ohm per degree centigrade at 20 centigrade increases .0041 ohm while under the same conditions the resistance of German silver increases only .00036 ohm. This method can also be employed to obtain a lower relativeA humidity at higher temperature and a higher relative humidity at lower temperatures by properly selecting the materials usedV This condition of relative i in the thermometers. humidity is much more desirable for personal comfort. Ii desired, however, instead of using such a means to compensate for variations in temperature,the relay |41 may be adjusted or provided with a temperature compensating bulb for varying the operation of the relay according to the temperature.
The relay |41 is employed to open and close the relay circuit comprising the conductor |5I,
` the secondary winding |52 of the transformer |53. the relay coil |54 and thev electric conductor |55. The relay, generally designated by the reference character |65, as well as the transformer |53V are all situated within an enclosed switch housing |56. The opening and closing of the relay circuit by the relay |41 causes the relay |55 to open and close the main supply circuit of the apparatus comprising the electrical conductors |51 and |58. The fan motor |3| and the compressor motor |21 are supplied with electric current through the electric conductors |51 and |58 from the power lines. The electric conductor |58 is connected to the relay switch |59, operated by the relay coil |54 and the relay |65, which switch connects at suitable times the electric conductorY |58 with the electric motor |21 through the electric conductor |60 as wellas the electric fan motor |3| through the electric conductor |6|. The electric conductor |62 completes the electric circuit of the fan motor I3|. The transformer |53 is provided with a primary winding |63 which is supplied with current from the electric conductor |58. When the relay |41 is closed, the relay |65 closes causing the electric motors |21 and |3| to drive a compressor |20 and fan |30 respectively thus causing thel air conditioning apparatus to operate. When the relay |41 opens, the relay |65 will open and stop the' operation of the apparatus. In this way the air conditioning apparatus will be intermittently operated to maintain the desired humidity.
' In damp places and in drying rooms it is usually desired to dehumidify the air without any reference to the temperature of the air. Indeed, in many cases it is desirable that the temperature of the air be increased. For this purpose I have provided a unitary portable air conditionv ingapparatus controlled by my improved electrical humidity control apparatus for effectively dehumidifying the air within the place desired. Referring to Figs. 5 and 6 I have shown a portable dehumidifying apparatus mounted on a platform |10 including an air-cooled compressor |1| mounted thereon for compressing the refrigerant and for forwarding the compressed refrigerant through the conduit |12 to an aircooled fin-type condenser |13 where the refrigerant is lcondensed and forwarded through/the conduit |14 to a receiver |15 where this liquefied refrigerant is collected. From the receiver |15 the liquid refrigerant is forwarded through the supply conduit |16 to an expansion valve |11 which controls the ilow of liquid refrigerant to the finned evaporator |18 which is situated directly aside of the condenser |13. The condenser and evaporator |13 and |18 are provided with a hood over the top portion. The refrigerant in the evaporator evaporates under reduced pressure and is returned to the compressor through the return conduit |19. All of the above mentioned apparatus is mounted on the platform 10. An electric motor |80, also supported on the platform, is provided for driving the compressor through pulley and belt means |8|.
'I'he motor |80 and the compressor |1| are both provided with means for drawing air first through the evaporator and then through the condenser |18 and then over the motor 80 and the compressor |1|. For this purpose the motor pulley adjacent the condenser |13 is provided with fan |88 and the combined pulley and flywheel of the compressor |1| is provided with fan blades |84 for drawing air first through the evaporator |18, then through the condenser |13, and finally directing the air over the motor |80 and the compressor |1|. below its dew point in the evaporator which removes moisture from the air, and then the air passes directly into the condenser |13 which transmits the e'xcess heat of the compressed refrigerant to the air thus condensing the refrig- ,v erant and warming the air, and iinally the air is discharged over the motor and compressor which In this way the air is first ccoledI air. By warming the air with the condenser,
compressor and motor the relative humidity is greatly reduced. The system operates highly eiiciently since the condenser |13 is cooled by the relative cold air coming from the evaporator |18.
The apparatus is preferably controlled by the improved electrical control apparatus shown in Fig. 4 and has the Wheatstone bridge circuit including the Wet and dry resistance thermometers and the relay provided within an enclosure |86 having louvers therein for allowing the air to pass over the wet and dry resistance thermometers on its way to the evaporator |18. This enclosure containing the bridge circuit is preferably placed in the path of the air moving to the evaporator |18. It, however, may be placed in any portion of the room desired, but preferably it should be placed where it will be responsive 4to the true relative humidity of the room. 'I'he primary relay as Well as the transformer for the secondary relaycircuit are enclosed in the box |81. 'I'he electric current for the motor |80 is supplied through the electric conductors |88 and |88. 'Ihe electric current is supplied to the Wheatstone bridge control circuit through the conductors |80 and |9|. The electric conductors |92 and |98 connect the primary relay housed within the box |81 and the secondary relay which is housed within the enclosure |86. 'Ihe electric conductors |94 and |95 conduct electric current from the box |81 to the electric motor |80.
With this type of dehumidifying apparatus the I maximum drying eiect is obtained, as well as the maximum eiiiciency. This is accomplished byv vreason of the fact that" the air cooled by the evaporator is employed for cooling the condenser, the compressor and the electric motor which raise the temperature of the air without' increasing its vhumidity content. 'I'he moisture condensed by the evaporator |18 is collected in a catch pan |96 from which it is removed by means of a drain pipe or other convenient means. My improved control apparatus so controls its operation of the electric motor 80 so as to prevent the humidity from rising above the permissible maximum.
1. An air conditioning apparatus for conditioning air including a refrigerant evaporating means lmeans, and humidity responsive lcontrol means for starting and stopping the operation of the liquefying means according to humidity conditions of the air to be conditioned.
2. An air conditioning apparatus for condition- `ing air includinga refrigerant evaporating means and means for circulating the air to be conditioned into heat exchange relation with said evaporating means, a refrigerant liquefying means for supplying liquid refrigerant to and for withdrawing evaporated refrigerant from the evaporating means, and humidity responsive controllmeans for starting and stopping the operation of the liquefying means according to humidity conditions of the air to be conditioned.
3. An air conditioning apparatus for conditioningl air including a refrigerant evaporating means indirect heat exchange relation with the air to be conditioned, a refrigerant liquefying means for supplying liquid refrigerant to and for withdrawing evaporated refrigerant from the evaporating evaporating means for supplying liquid refrigerant to and for withdrawing evaporated refrigerant from the evaporating means, said compressing and condensing means being isolated from the air within the enclosure, and humidity responsive means responsive to predetermined high humidity conditions to start the compressing means and responsive to predetermined low humidity conditions to stop the compressing means.
5. An air conditioning system for conditioning air comprising a refrigerant evaporating means in direct thermal exchange relation with the air to be conditioned, a refrigerant liquefying and circulating means for withdrawing vaporized refrigerant from and for supplying liqueed refrigerant to said evaporating means, and humidity responsive means for controlling the circulation of the refrigerant. v
6. An air conditioning system for conditioning air comprising a refrigerant evaporating means in direct thermal exchange relation with the air to be conditioned, a refrigerant liquefying and circulating means for withdrawing vaporized refrigerant from and for supplying liquefied refrigerant to said evaporating means, and humidity responsive means for starting and stopping the circulation of the refrigerant by said liquefying 'and circulating means.
7. An air conditioning apparatus for conditioning air for an enclosure including a refrigerant evaporating means, a refrigerant liquefying means for supplying liquid refrigerant to and for withdrawing evaporated refrigerant from the evaporating means,` and humidity responsive control means for controlling the operation of the liquefying meansin accordance with humidity conditions of air in said enclosure.
8. The combination with a building having a rooml and an air conditioning apparatus therein, said air conditioning apparatus embracing a refrigerating system and a fan for circulating air therethrough, means for electrically operating said refrigerating system and said fan, a relay switch for controlling said means, a transformer for operating said relay switch and a device responsive to a psychrometric function of air arranged in said building for controlling the flow of current through said transformer.
CHARLES F. KETTERING.