US2290426A

US2290426A - Air conditioning system

Info

Publication number: US2290426A
Application number: US154027A
Authority: US
Inventors: John E Haines
Original assignee: Honeywell Inc
Current assignee: Honeywell Inc
Priority date: 1937-07-16
Filing date: 1937-07-16
Publication date: 1942-07-21
Anticipated expiration: 1959-07-21

Description

Jul 21, 1942. E, MINES 2,290,426-

AIR CONDITIONING'SYSTEM Filed July 16, 1937 2 Sheets-Sheet'i Inventor John EHaz'rzes July 21, 1942. t J 5 HAINES 2,290,426

' ,AIR CONDITIONING SYSTEM Filed Ju1y 16, 1937 2 Sheets-Sheet 2 Inventor John E. .Haivzas I 11/ (6 s aw Patented July 21, 1942 AIR CONDITIONING SYSTEM John E. Haines, Chicago, Ill., assignor to Minneapolis-Honeywe'il Regulator Company, Minneapolis, Minn., a corporation of Delaware Application July 16, 1937, Serial No. 154,027

17 Claims.

This invention relates generally toair conditioning systems and is more particularly concerned with air conditioning systems of the type utilizing a compression refrigeration system wherein the compressor is driven by meansof an internal combustion engine.

The primary object of my invention is to provide a dependable control arrangement which is especially adapted for systems of this type, such control arrangement acting automatically to-control the operation of the system in a manner to maintain proper temperature and humidity conditions within the conditioned space.

A.more specific object of my invention is the provision of a novel air conditioning control system which automatically and graduatingly adjusts the speed or output of the internal combustion engine in accordance with the total requirements for refrigeration of the air conditioning system, and which simultaneously varies the action of the air conditioning system as between sensible heat cooling and dehumidification in a manner to maintain both the temperature and humidity conditions of the air within the space at desired values.

A further object of my invention is to provide a system which obtains the results above mentioned and which also acts automatically to start the internal combustion engine upon a demand for air conditioning; and which automatically places the engine out of operation when the demand for refrigeration ceases, or whenever such demand for refrigeration becomes so small as to require operation of the engine at too low an output.

While my invention is more concerned with air conditioning systems of the type utilizing internal combustion engine drive, certain features of the invention are applicable to air conditioning systems in general. Other and more specific objects of my invention will appear from the following detailed description and from the appended claims.

For a full disclosure of my invention, reference is made to the following detailed description and to the accompanying drawings, in which Figure 1 is a diagrammatic illustration of an air conditioning system embodying one form of my invention; and in which Figure 2 illustrates diagrammatically an air' conditioning system having a modified control arrangement.

Referring to Figure 1, reference character I inair inlet duct 2 which leads from a space to be conditioned 3, and. to a fresh air inlet duct 4 which leads from outside the building. The fresh air inlet 4 is provided with suitable dampers 5 for controlling the admittance of fresh air into the conditioning chamber I. The outlet of the conditioning chamber is connected toa fan 6,

this fan, inturn, being connected to a discharge duct 1, which discharges conditioned air into space 3. Fan 6 is shown as being driven by an electric motor 8 which is connected through a suitable switch to line wires 9 and I0.

Located within the conditioning chamber I is a direct expansion cooling coil II, this cooling coil forming a part of a compression refrigeration system, which includes a compressor l2, a condenser l3, and an expansion valve M. The discharge of the compressor I2 is connected by a discharge conduit. IE to the inlet of the condenser, and the outlet of the condenser is connected to a liquid line l6 which leads to the expansion valve [4. The operation of compression refrigeration systems of this type is well known in the art and hence no detailed description of such operation is necessary. However, it may be stated that operation of the compressor l2 causes chilling of the cooling coil II, and the temperature of the cooling coil I I will vary in accordance with the compressor speed and also in accordance with the temperature of the air contacting said cooling coil. 1

Interposed inthe liquid line I6 is a solenoid refrigerant valve l1 for stopping the flow of refrigerant into the cooling coil at times. The solenoid valve 11 may be of any suitable form and is herein illustrated as being of the type Y which opens when energized and which closes dicates generally an air .conditioning chamber,

when deenergized. The solenoid valve 11 is controlled by abalancing type of relay generally indicated as l8 and this relay is, in turn, controlled by a return air temperature controller l9 and an outdoor temperature responsive thermostat 20.

The balancing relay It! comprises a U-shaped armature which is pivoted at 2|, this armature having legs 22 and 23 which cooperate with coils 24 and 25, respectively. The pivoted armature carries through a suitable insulating connection a switch arm 26 which cooperates with a contact 21. By this arrangement, energization of the coil 24 tends to cause clockwise rotation of the armature, this tending to cause switch arm 26 to disengage contact 21. The coil 25 on the other hand tends to cause a counter-clockwise rotation of the armature, thus tending to engage switch arm 26 with contact 21. It will be apparent that ,more highly than coil 24, the switch arm 26 will engage contact 21.

The retmn air temperature controller I! may be of any suitable form and as illustrated comprises a bellows 28 which is suitably fixed at its lower end and which cooperates with the actuating arm 29 of a bell-crank lever having a control arm 30, this control arm cooperating with a control resistance 3| to form a control potentiometer. The bellows 28 is connected by a capillary tube 32 to a control bulb 33 which is located in the return air duct 2. The bellows, tube and bulb contain a suitable volatile fluid whereby the vapor pressure within bellows 26 varies with the temperature surrounding the central bulb 33. Hence, as the return air temperature rises, the vapor pressure of the volatile fill will increase to cause an expansion of the bellows 26 which rotates the actuating arm 23 in a counter-clockwise direction against the action of a spring 34, this causing travel of the control arm 30 to the left across control resistance 3|. Upon a decrease in return air temperature, the pressure within bellows 26 will decrease, this permitting movement of the control arm 36 to the right across resistance 3| under the action of spring 34.

The outdoor temperature responsive controller 23 may be formed in exactly the same manner as the controller l3, and in this case the control bulb 35 is located in the fresh air duct 4. troller 2|! is provided with a control arm 36 and a control resistance 31 which together form a control potentiometer.

Reference character 33 indicates a step-down transformer, the primary of which may be connected in parallel with the fan motor 6. The relay coils 24 and 26 are connected across the secondary 39 by wires 46, 4t, 42, and 43. Also connected across the transformer secondary are the resistances 3| and 31 of the controllers l3 and 20, respectively. These resistances are connected across said transformer secondary by means of

wires

40, 44, 45, 46, 41, and 43, protective resistances 48 and 43 being interposed in the

wires

41 and 44 for preventing excessive current from flowing when the

control arms

36 or 36 reach an extreme position. Connected to wire 42 which joins the upper ends of relay coils 24 and 25- is a wire 50 which leads to the control arm 30 of the return air controller IS. The control arm 30 is also connected by a wire 5| to the control arm 36 of the controller 20, a rheostat 52 being interposed in said wire.

By the wiring arrangement just described, the control arm 30 divides the control resistance 3| into one portion which is in parallel with relay coil 24 and into another portion which is in parallel with the relay coil 25. For instance, the portion of resistance 3| to the left-of the control arm 30 is connected in parallel with relay coil 24 as follows left end of resistance 3|, wire 45, wire 44, wire 4|, relay coil 24, wire 42, and wire 5 6 to control arm 30. In a similar manner, the control The con- The control arm 3|! of controller I9 is shown as engaging the extreme right-hand end of control resistance 3|, this causing the entire control resistance 3| to be connected in parallel with relay coil 24 while substantially short-circuiting the relay coil 25. Hence, more current will flow through relay coil 24 than through coil 25, this causing clockwise rotationof the armature to the position shown in which switch arm 26 is disengaged from contact 21. As the return air temperature increases, the control arm 3|] will be shifted to the left across control resistance 3|, thus decreasing the portion of resistance 3| which is in parallel with relay coil 24 and increasing the portion of said resistance which is in parallel with relay coil 25. This will cause the current flow in relay coil 24 to decrease and the current fiowin relay coil 25 to increase. When the travel of control arm 30 to the left across control resistance 3| is sufflcient to'cause a greater current flow in relay coil 25 than occurs in relay coil 24, the switch arm 26 will engage contact 21, this opening the solenoid valve H by a circuit as follows: transformer secondary 39, wire 40, wire 53, contact 21, switch arm 26, wire 54, solenoid valve |1, wire 55 and wire 43 back to the transformersecondary. Therefore, when the space temperature increases to a predetermined value, the solenoid valve l1 will be opened, this permitting flow I of refrigerant to the cooling coil I.

It will be noted that the action of the controller 20 upon relay I6 is opposite to that of the return air temperature controller. In other words, upon an increase in outside air temperature, the controller 20 tends to cause the current flow in relay coil 25 to be decreased and that in relay coil 24 to be increased. Due,to this effect,

I it will be apparent that the control arm 30 must arm 36 divides the resistance 31, the left half of said resistance being connected in parallel with relay coil 25 and the right half of said resistance being connected in parallel with relay coil 24.

a As the current flow through relay coils 24 and 25 will vary as the resistance in parallel with such move further to the left across resistance 3| in order to cause relay coil 25 to be energized more highly than relay coil 24., this requiring a higher return air temperature. The outside temperature responsive thermostat 20, therefore, acts, in effect, to adjust the temperature at which the return air temperature controller causes opening of the solenoid valve. It will be noted that rheostat 6| is interposed between the control arm 36 of the controller 20 and the relay l8. 13yv adjusting this rheostat, the effect of controller 20 upon relay l6 may be varied. In this manner, the desired effect of the outside temperature controller upon the control point of the return air temperature controller l9 may be secured. This rheostat may be adjusted for instance so that for each 3 F. rise in outside temperature, the inside temperature maintained by controller l9 will be raised 1 F., thereby maintaining a variable differential between inside and outside temperature as ordinarily desired.

The compressor 2 is driven by means of an internal combustion engine 60, this engine being provided with the usual intake manifold 6|, exhaust manifold 62, starting motor 63, generator 64 and fly-wheel 65. The fly-wheel 65 contains a suitable clutchmechanism as well known in the art and is connected to a drive shaft 66 carrving a pulley 61 over which run belts 68 for rostarted, it is desirable that the compressor be disconnected therefrom and for this purpose a outwardly, this causing the bell-crank lever I2 to be positioned for disengaging the clutching mechanism. When the engine is at rest, the pressure within the intake manifold 6| will be equal to atmospheric, this permitting the piston I to be moved by spring I8 for disengaging the clutch. When the engine 60 is started, however, a sub-atmospheric pressure will be developed within the intake manifold, this causing movement of piston to the left for rotating bell-crank lever 12 in a direction for engaging the clutch. The clutching mechanism just described, therefore, acts automatically to unload the engine while it is being started and to connect the compressor thereto after the engine is started.

The speed of the engine 60 is controlled by means of a throttle valve 80 located in the fuel supply pipe 80a for the intake manifold. Throttle valve 80 is automatically positioned by means of a proportioning motor generally indicated as 8I, this motor being controlled by means of a low-side or suction pressure controller 82 and by a space relative humidity controller 83.

Referring now to the proportioning motor 8I, this motor may be of the type shown in Patent 2,028,110 issuedto Daniel G; Taylor on January 14, 1936. Reference character 84 indicates an operating shait having mounted thereon a lever arm 840. which is connected to the throttle valve 80 by suitable linkage. The operating shaft 84 is driven through a gear train 85 by a reversible electric motor means comprising armatures 86 and 81 which cooperate with field coils 88 and 89. It will be understood that armature 86 and field coil 88 form a motor for drivmg the shaft 84 in one direction while armature 8! and field coil 89 comprise a motor for driving the shaft 84 in the opposite direction.

The energization of controlled by means of a balancing relay 90, this relay comprising a U-shaped armature which is pivoted at 9I and having legs 92 and 93 which cooperate with relay coils 94 and 95, respectively. Armature 9I carries by a suitable insulating member a, switch arm 96 which cooperates with contacts 91 coils, 94 and 95 are equally energized, the switch arm 96 will be disengaged from both contacts 91 and 98. If relay coil 94 becomes more highly the field coils as and as is and 98, respectively. When relay its lower end and which cooperates with the actuating arm I03 which actuates a control arm I04 and a corrector arm I05. The control arm I04 cooperates with a control resistance I06 to form a control potentiometer, and corrector arm I05 cooperates with a center tapped corrector resistance I 01. The bellows I02 is connected to the suction line of the refrigeration system by a tube a I08. When the suction or low-side pressure of energized than coil 95, the switch arm 96 will engage contact 91 as shown. When, however, relay (3011'95 becomes more highly energized than c011 94, the switch arm 98 will engage'contact 98. The relative 'energization of relay coils 94 and 95 is controlled tiometer 99 which comprises a balancing arm I00 which is mounted upon the operating shaft 84,

. this balancing arm cooperating with a resistby means of controllers 82. and 83 and also by means of a balancing potenthe refrigeration system increases, the bellows I02 will expand against the action of a spring I09, this causing movement of arms I04 and I05 in a counter-clockwise direction across their respec-.

tive resistances. Upon a decrease in suction pressure, the opposite action will take place, namely, the bellows I02 will contract thus permitting opposite rotation of arms I04 and I 05 under the action of spring I09.

The space relative humiditycontroller 83 comprises a bell-crank lever IIO having a control arm I II which cooperates with a resistance II2 to form a control potentiometer. The actuating arm H3 is connected to a humidity responsive device I I4 which comprises a plurality of strands of hair or other moisture responsive material,

these strands being secured by upper and lower clamping members I I5 and I I6, the upper clamping member II5 being secured to control arm II3 while the lower clamping member is fixedly supported. For urging the actuating arm I I3 upwardly is a spring I II, this spring acting to maintain the strands taut. Upon a decrease in humidity, the strands will decrease in length, this causing rotation of the control arm III towards the left across resistance II2 against the'action of spring I I 'I. When the humidity increases, however, the strands will increase in length, this permitting the spring II 1 to shift control arm I II towards the right across resistance I I2.

Reference character I indicates a step-down transformer, the primary of which may be connected to any suitable source of power. The relay coils 94 and 95 are; serially connected across the secondary I2I by means of Wires I22, I23, I24, I25, and I26. The control resistance I 06 is also connected across the transformer secondary, the connections including wires I22, I23, I21, I28, I28a, I29 and I26. The balancing resistance IOI is connected in parallel with control resistance I06 across the transformer secondary by means of wires I and I3I. The control resistance II2 of the humidity controller is also connected in parallel with the control resistance I06,by means of wires I32 and I33. To the wire I25 which joins the upper ends of relay coils 94 and 95 is attached a wire I34, this Wire, in turn, being connected by a wire I connected to corrector ary along with the relay coils 94 and 95 which are connected across such secondary in series either of the control arms or the balancing arm acrossits resistance will therefore affect the current flow in relay coils 94 and 95.

With the parts in the position shown, the humidity is at an intermediate value as indicated by the control arm I I I engaging the center of resistance H2. The suction pressure is somewhat low as indicated by the control arm I04 assuming a position to the right of the center of control resistance I09. This will cause movement of the proportioning motor shaft 94 to fully close the throttle valve 99, the balancing arm I at this time engaging the extreme right end of balancing resistance IOI. If the suction pressure should increase, the control arm I04 will be shifted to the left across resistance I09, this decreasing the portion of said resistance which is in parallel with relay coil 94 and increasing the portion of said resistance which is in parallel with relay coil 95. This will decrease the current fiow through coil 94 and increase the flow through coil 95, which will result in switch arm 99 engaging contact 98. The engagement of switch arm 96 with contact 98 will energize the motor field 99 by a circuit as follows: transformer secondary I2I, wire I22, wire I40, motor field 99, wire I4I, limit switch I42, wire I43, contact 99, switch arm 99, wire I44 and'wire I29 to secondary I2I. Energization of motor field 99 will cause rotation of the shaft 94 in a counter-clockwise direction, thus moving the throttle valve 90 towards open position. At the same time, the balancing arm I00 will move to the left across balancing resistance "II, this reducing the portion of said resistancein parallel with relay coil 95 and increasing the portion of said resistance in parallel with relay coil 94. This will result in decreasing the current flow in relay coil 95 and increasing the current flow in relay coil 94, this tending to balance out the initial unbalancing efiect of the relay of the controller 92. when the rotation of shaft 94 is such that the balancing potentiometenrebalances the current fiows in relay coils 94 and 95, the switch arm 99 will disengage contact 99 thereby causing the motor to .stop with the throttle valve in this new position. An increase in suction pressure will, therefore, cause the proportioning motor to move the throttle valve towards open position. It will be apparent that the movement of the proportioning motor 99 will be proportionalto the movement of control arm I04 upon resistance I09, and hence the degree of opening of the throttle valve will be in proportion to the increase in suction pressure. Upon a fall in suction pressure, it will be apparent that the opposite action will take place, namely, the balancing relay 90 will be unbalanced in a direction to cause energization of motor field 99 for moving the throttle valve 90 towards closed position, this causing the balancing potentiometer to rebalance the relay for causing the throttle valve to be held in this further closed position.

It should be noted that interposed between the balancing arm I00 and the junction of the relay coils 94 and 95 is a rheostat I45. The purpose of this rheostat is to decrease the effect of the balancing potentiometer upon the energization of relay coils 94 and 95. This rheostat acts to diminish the fiow of current through the balancing arm I00 and, therefore, requires a greater movement of balancing arm I00 on resistance IM to cause a given variation in current flows through relay coils 94 and 95 than would occur if said rheostat were not 'present. By properly adjusting this rheostat, the suction pressure controller 92 may be caused upon slight movement to cause such an unbalancing action on relay coils 94 and 95 as to require movement of the balancing arm through its entire range to rebalance. The action of the rheostat I45, therefore, is to increase the sensitivity of the suction pressure controller 92 thereby causing the operating range of such controller to be less than its total range.

' increasing the portion of said resistance which is in parallel with relay coil 95. This will cause a decrease in current flow in relay coil 94 and an increase in current flow in relay coil 95, this acting to cause energization of motor field 99 for driving the throttle valve 99 towards open position. As the throttle valve is moved towards open position, the balancing potentiometer will gradually rebalance the relay 9I| thus causing the deenergization of motor field 99 for stopping the motor with the throttle valve in a further open position. Conversely, upon a decrease in relative humidity, the opposite action will take place, namely, the proportioning motor will be energized to cause movementof the throttle valve 9.9 to a further closed position.

If the relative humidity increases, the humidity controller 93, in the manner described, will cause further opening of the throttle valve 90. This will result in increasing the engine speed and hence causing the suction pressure to decrease. This falling in suction pressure will act upon the controllerv 92 to cause it to slow down the engine. When the fall in suction-pressure is such that controller 92 closes throttle valve sufliciently to prevent further fall in pressure, the suction pressure will be maintained constant in this new value. An increase in relative humidity, therefore, acts, in effect, to cause adjustment of the suction pressure controller 92 to maintain a lower suction pressure within the refrigeration system. A decrease in relative humidity will have the opposite efiect, namely, to cause the closing of the throttle valve thereby causing increase in sue-.- tion pressure in the refrigeration system. It will be noted that interposed in the wire I99 which connects the control armIII of the humidity controller to the balancing relay is a rheostat I49. The purpose of this rheostatis to control the effect of the controller 93 upon the balancing relay 90 and .to thereby determine the effect of controller 99 upon the control point of the sue- I tion pressure controller 92. Byproperly adjusting this rheostat, any desired change in suction pressure for a given change in humidity may be obtained.

In accordance with my invention, the speed of the engine is not only modulated but the engine clockwise direction, thus biasing the mercury switch I53 to closed position. The switching member is so mounted upon the operating shaft 84 as to cause tilting of mercury switch I53 to open position whenever the throttle valve is moved to a predetermined minimum position. When the throttle valve is opened sufliciently to permit efiicient operation of the engine, however, the switching member I50 will permit spring I54 to cause tilting of mercury, switch I53 to closed position. One terminalof mercury switch I53.is connected by a wire I55 to a storage battery I55, one terminal of said storage battery being grounded as at I51. The other terminal of mercury switch I53 is connected to a wire I58, this wire being connected by a wire I59 to an ignition coil I60 for the engine. The wire I58 also leads to a starting'relay I6I. This startingrelay may be of any suitable form, and if desired may be of the type shown and described in the Loehr et a1. Patent No. 1,773,913, dated August 26, 1930. i

This type of starting relay is adapted to energize I the starting motor whenever the control circuit of said. relay is energized and for this purpose the starting relay I6I is connected to the storage battery and'to the starting motor 63 by means of wires I62 and I63. This starting relay is also adapted to deenergize the starting motor when the engine starts and to prevent e e on Of the starting motor so long as the engine is in operation as evidenced by operation of the generator. For this purpose, the starting relay is connected to the generator 64 by means of wires I64 and I65. Reference character I66 indicates a suitable generator cutout. From the foregoing, it will be apparent that when mercury. switch I53 closes, the ignition circuit for the engine will be closed, and simultaneously the starting motor will be placed into operation for causing starting of the engine. It also shouldbe apparent that when the throttle valve 80 is closed to such an extent that mercury switch I53 opens, the ignition circuit for the engine will be broken, thereby causing the engine to stop.

It should be noted that mercury switch I53 is shown as being of the bent type having a wide difierential of operation: This wide difierential is necessary for preventing short-cycling of the ployed. v

Operation of Figure 1 With the parts in the position shown, the space or return air temperature is below the. setting' of the controller I9 as determined by the outside temperature controller 20. The relay I9 has, therefore, assumed a position in which switch arm 26 has disengaged contact 21, this causing closing of the solenoid valve I'I. Due to no refrigerant passing into cooling coil II, the suction pressure of the refrigeration system has decreased suiliciently to cause closing of the throttle valve, this also causing opening of the mercury switch I53 for placing the engine out of operation. 1. f

If now should the return air temperature rise above the control point of the return air temperature controller I9, the relay I8 will cause opening of solenoid valve IT. This will permit flowoi refrigerant into cooling coil II. The retrigerant will evaporate in said cooling coil thereby causing the pressure within the cooling coil and suction line to increase. As the suction pressure increases, the controller 82 will cause movement of the proportioning motor in a direction to open the throttle valve 80. When the throttle valve 80 is opened sufficiently to permit proper operation of the engine, the mercury switch I53 will close, this causing starting of the engine in the manner just described. After the engine has started, the automatic clutching mechanism will engage to cause operation of the compressor I2. In this manner, when the temperature of the space being conditioned rises above the control point of controller I9, the system will automatically be placed into operation.

When the system is in operation, the speed of the compressor will be varied in accordance with both temperature and humidity conditions. Thus,'iI the temperature of the air being conditioned increases, a greater amount of refrigerant will be evaporated within cooling coil I I, this causing the suction pressure to increase. In response to this increase in suction pressure, the controller 82 will act to increase the engine speed. Similarly, upon a fall in the temperature of the air passing over the cooling coil, less refrigerant will be evaporated therein, this causing the suction pressure to decrease which, in turn, results in slowing down of the engine. The suction presthe dehumidifying effect of the cooling coil.

Conversely, upon a decrease in humidity, the controller 83 will cause a higher coil temperature to be maintained, thus reducing the dehumidifying effect of the coil. In this manner, the humidifying efiect of the cooling coil is varied in a man-.

ner to maintain the space relative humidity within predetermined limits.

From the foregoing it will be' seen that the speed of the engine is varied in accordance with both the temperature and humidity conditions of the space being conditioned in a. manner to maintain both the temperature and the humidity of the space being conditioned within predetermined values. It should also be apparent that whenever the temperature and humidity conditions are such that the load on the system is too light to Justify operation of the engine, the control mechanism will automatically place the engine out of operation. It should further be apparent that if-the temperature falls below the control point of controller I9, the refrigerant valve I! will be closed, this stopping the flow of refrigerant into cooling coil II which, in turn, results in the suction pressure controller 82 perating to place the engine out of operation.

Figure 2 mechanism and the automatic starting mecha-- nism are identical to those illustrated in Figure 1, and hence these features are not described here in detail. Corresponding parts in both figures are provided with the same reference characters.

In this figure, the throttle valve instead of being controlled in accordance with the suction pressure of the refrigeration system, is controlled conJointly by means of a return air temperature controller 200, a space relative humidity controller 20I and an outside temperature responsive controller 202. The humidity controller 20I and the outside temperature responsive controller 202 are formed similarly to the corresponding ,controllers illustrated in Figure 1, hence a detailed description of these controllers is unnecessary. The return air temperature controller 200 may be of any suitable form and is shown as comprising a bellows 268 which is fixedly secured at its lower end and which actuates an actuating arm 204 which carries a control arm 205 and a corrector arm 206, thecontrol arm 205 cooperating with aresistance 201 to form a control potentiometer and the corrector arm 206 cooperating with a centered tapped corrector resistance 208. The bellows 208 is connected by means of a capillary tube 209 to a bulb 2I0 which is located in the return air duct 2. The bellows, tube and bulb contain a suitable volatile fill and hence upon an increase in return air temperature, the arms 205 and 206 will be rotated in a counterclockwise direction across their, respective resistances. Upon a decrease in return air temperature, these arms will be rotated in the opposite direction under the action of a spring 2I I.

As in the case of Figure 1, the throttle valve 80 is positioned by means of a proportioning motor 8I, this proportioning motor being identical in construction to that illustrated in Figure l and including a relay 90. Relay 90 is identical in construction to the corresponding relay of Figure 1 and includes a pair of relay coils 94 and 95 cooperating with a pivoted U-shaped armature carrying a switch arm 96 adapted for engagement with contacts 91 and 98.

Reference character I20 indicates a suitable stepdown transformer having a secondary I2I. As in Figure 1, the relay coils 94 and 95 are serially connected across the terminals of secondary I2I by means of wires I22, I23, I24, I25 and I26. Also connected to the wire I22 is a wire 2l2, this wire, in turn, being connected to wire 2I8 which is connected to 'the left-hand end of control resistance 201 by wire 2, to the right-hand end of resistance 81 of controller 202 by a wire 2I5, to the left-hand end of resistance II2 of the humidity controller 20I by a wire 2 I6, and to the left-hand end of balancing resistance IN by a wire 2I1. Also connected to the wire I26 leading from the transformer secondary I22 is a wire 2I8 which, in turn, is connected to wire 2I9 which is attached to a wire 220 which leads to the righthand end of the balancing resistance IN. The wire 220 is also connected to the right-hand end of control resistance 201 by a wire 22I, to the left-hand end of control resistance 81 by wire 222 and to the right-hand end of control resistance II2 by a wire 223'. By the wiring arrangement just described, it will be apparent that each of the control resistances and the balancing resistance are connected in parallel across the terminals of the transformer along with the relay coils 94 and 95 which are connected across said transformer in series. A. flow of current will, therefore, take place through the relay coils and through each ofthe resista ces.

Attached to the wire I25 /hich joins the upper ends of the relay coils 94 and 95 is a wire 224 which, in turn, is attached to a wire 225 which is connected at one end to the balancing arm I00 and at its other end to the control arm III of the humidity controller, rheostats I45 and I46 being interposed as shown. The wire 225 is also connected to the corrector resistance 208 as shown, and is connected to the control arm 36 of the outdoor temperature responsive controller 202 by means of a wire 226, a rheostat 221 being interposed in said wire. By this wiring arrangement, it will be noted that each of the control arms and the balancing arm is connected to the junction of relay coils 94 and 95. This has the eifect of causing each of the control arms and the balancing arm todivide its respective resist-' ance into one portion which is in parallel with relay coil 94 and another portion which is in parallel with relay coil 95. Movement of either of the control arms or the balancing arm, therefore, varies the resistance which is in parallel with relay coils 94 and 95, thereby varying the relative current flows in said relay coils.

With the parts in the position shown, each of the control arms is engaging the mid-portion of its respective resistance. For this position of the of said resistance which is in parallel with relay' coil 95 and increasing the portion of said resistance which is in parallel with relay coil 94. This will cause an increase in current flow in relay coil 94 and a decrease in currentfiow in relay coil 95, thus causing switch arm 96 to engage contact 91. Engagement of switch arm 96 with contact 91 will energize the motor field 88 by a circuit as follows: from transformer secondary I2I, wire I22, wire 2I2, wire 2I3, wire 230, switch arm 96, contact 91, wire 23I, limit switch 2, wire 242, motor field 88 and wire 2I8 to secondary I26. Energizatlon of motor field 88 will cause rotation of shaft 84 in a clockwise direction, this causing movement of the throttle valve towards open position. Simultaneously with the opening movement of the throttle valve, the balancing arm I00 will balancing resistance I0 I, this decreasing the portion of said resistance which is in parallel with relay coil 94 and increasing the portion of said resistance which is in parallel with relay coil 95. This will cause an increase in current fiow in relay coil 94 and a decrease in current flow in relay coil 95, thereby tending to balance out the initial unbalancing action of the controller 200. When the throttle valve is opened to'such an extent that the balancing potentiometer balances out the initial unbalancing action of controller 200, the relay coils 94 and 95 will again become equally energized, this causing disengagement of switch arm 96 from contact 91 to thereby stop the motor or throttle valve in this new position.

Upon a decrease in return air temperature, the opposite action will take place, namely, the controller 200 will cause the relay coil 95 to become more highly energized than relay coil 94, this, in turn, causing engagement of switch arm 96 with contact 98 which energizes the motor field 89 for causing movement of the throttle valve towards closed position. It will be apparent that be shifted to the right along during the closing movement of the valve, the balancing potentiometer will tend to rebalance the relay, and eventually will cause stopping of the motor with the throttle valve in a further closed position. The controller 200, therefore, acts to cause opening of the throttle valve upon an increase in return air temperature and to cause closing of. the throttle valve upon a decrease in return air temperature. Thus, if the return air temperature increases, more fuel will be supplied to the engine, this causing said engine to operate at a higher speed which causes the temperature of the cooling coil I I to be reduced thereby increasing the cooling effect of the system to counteract the rise in temperature. Similarly, upon a fall in temperature, less fuel will be supplied to the engine thereby reducing the cooling effect of the system to prevent further fall in space temperature.

It will be noted that rheostat I45 is interposed between the balancing arm I and the junction of relay coils 94 and 95. This rheostat acts to desensitize the balancing potentiometer in a manner to increase the sensitivity of the return air temperature controller 200. Due to rheostat I45 decreasing the current flow through the scribed. This will cause the cooling effect of the coil II to be increased which eventually will result in lowering the temperature within the conditioned space 9. In response'to this lowering in temperature, the return air temperature controller will begin slowing down the engine speed and when the return air temperature has fallen to such a point that controller 200 has slowed down the engine sufficiently. to prevent further fall in temperature, the space temper- An increase in relative humidity, therefore, acts to cause a lower temperature to be maintained within the conditioned space. Upon falling relative humidity, the opposite action will take place, namely, the humidity controller 20I will cause slowing down of the engine which eventually will result in the space temperature increasing. In

response to this increase in space temperature,

the controller 200 will begin increasing the en gine speed, and when the increase in temperature is such that controller 200 causes operation of the engine at a sufficient speed for preventing further increase, the space temperature will be balancing arm I00, it will be apparent that a larger movement of said arm across the resistance will be required in order to cause a given effect upon the

coils

94 and 95 than would be necessary were said rheostat not present. Thus, a relatively small movement of the control arm 205 across the control resistance 201 may cause such an unbalancing effect upon the relay coils 94' and 95 that a movement of the control arm I00 along its complete range of travel is required for rebalancing. By properly adjusting the rheostat I45, a temperature change, for instance 2 ,F., of the return air may cause movement of the throttle valve from one extreme position to the other even thoughthe total range of the return air temperature controller 200 may be as high as 8 or 10 F. In other words, the function of the rheostat I45 is to make the operating range of controller 200 less than its total range.

held constant at this point.

From the foregoing, it will be apparent that the humidity controller acts to adjust the control point of the return air temperature controller 200. In other words, the humidity controller 20I acts to shift the location of the operating range of the controller 200 within its total range in a manner to cause a higher temperature to be maintained in the space as the humidity falls, and a lower'temperature to be maintained as the humidity increases. It will be noted that rheostat I46 is interposed between the control arm I II of the humidity controller and the junction of the relay coils 94 and 95. This rheostat permits the effect of controller 20I upon the energization of

coils

94 and 95 to be varied, and thereby provides for adjusting the effect of the humidity controller 20I upon the control point of the return air temperature con- Assuming the return air temperature remains constant, if the space relative humidity should increase, the control arm I II will be shiftd to the left across control resistance H2, this causing an increase in current flow in relay coil 94 and a decrease in current flow in relay coil 95. This will result in switch arm 96 engaging contact 91 for energizing motor field 88, this causing rotation of shaft 84 in a direction to open the throttle valve 80. Simultaneously, with this opening movement the balancing potentiometer will tend to counteract the initial unbalancing action of the humidity controller. When the throttle valve 80 has been opened a degree corresponding to the movement of control arm III across resistance II2, the relay 90 will become rebalanced, thus causing the motor .to stop with the valve in this further opened position. An increase in relative humidity, therefore, acts upon the proportioning motor 9| in a manner to cause opening of throttle valve 80. Upon a decrease in humidity, the opposite action will take place, namely, the throttle valve will be moved towards closed position.

It will be apparent that by this arrangement the humidity controller 20I will vary the temperature maintained by the controller 200. For instance, when the relative humidity. increases, the engine speed will be increased as just detroller 200. By properly adjusting rheostat I46, the humidity controller may be made to vary the temperature maintained upon a variation in humidity which is just suflicient for compensating for the effect on human comfort of the change in humidity. The temperature controller 200 and the humidity controller 20I, therefore, cooperate to maintain a constant comfort or effective temperature within the conditioned space.

Assuming the temperature and humidity remain constant, if the outside temperature should increase, the control arm 36 of the temperature controller 202 will be shifted to the left'across resistance 31, this decreasingthe portion of said resistance which is in parallel with relay coil 94 and increasing the portion of said resistance which is in parallel with relay coil 95. This will increase the current flow in coil 95 and decrease the current flow in coil 94, thereby causing engagement of switch arm 96 with contact 90 to energize motor field 89, this causing rotation of shaft 84 in a direction to close the throttle valve 80. An increase in outside temperature will, therefore,.act to cause the throttle valveto be moved towards closed position. This will cause slowing down of the engine and hence cause the cooling effect of the coil II to be reduced. Due to the increase in cooling load caused by the increase in outside temperature, and to the reduction in cooling effect of coil II, the space temperature will begin to rise. In response to this rise in temperature, the return air temperature controller 200 will begin causing the engine speed to be increased and when the space temperature has risen. to such a point that the engine speed is incrased just suflicient- 1y to prevent further temperature increase, the space temperature will be held constant at this new value. An increase in outside temperature, therefore, acts upon the controller 200 in a manner to cause said controller to maintain an increased value of temperature within the conditioned space. The rheostat 221 which is interposed between the control arm 36 and the balancing relay 90 provides for adjustment of the efiect of controller 202 upon the control point of the return air temperature controller 200. By properly adjusting this rheostat, any desired effect may be obtained. For instance, the return air temperaturecontroller may be made to raise its control point 1 F. for each 3 F. rise in outside temperature.

From the foregoing, it should be apparent that the controllers 200, 2!" and 202 conjointly control the position of the throttle valve 80 in a manner to maintain a constant effective temperature for any given value of outdoor temperature and that the effective temperature maintained within the conditioned space will be varied as the outdoor temperature varies. It will be apparent that the operation of the starting mechanism is the same as described in detail in connection with Figure 1. Therefore, whenever the three controller cause the throttle valve to be closed to suchan extent as to indicate that the engine is-operating at too low a speed, the mercury switch I53 will open,v thus placing the engine out of operation. Conversely, when the three controllers cause the throttle valve to be opened to such an extent asto indicate that satisfactory operation of the engine will result, the mercury switch I53 will be closed, this causing the engine to be placed into operation.

In this embodiment of the invention, a wide diiferential type of switch I53 as in Figure 1 is illustrated. It will be understood that any suitable form of switch and switch actuating mechanism may be employed, and if desired, in this embodiment, a switch having a small difierential of operation will be utilized.

While I have shown and described two embodiments of my invention, it will be: apparent that many changes which are within the scope of my invention will be obvious to those skilled in the art. I, therefore, desire to be limited only by the I scope of the appended claims and the prior art.

, I claim as my invention:

1. In an air conditioning system, in combination, an evaporator, means for passing air to be conditioned in heat exchange relationship with said evaporator and to a space to be conditioned,

a compressor for supplying refrigerant to said evaporator and for reducing the pressure in said evaporator, a controller for-varying the output of said compressor, control means responsive to a condition which is a measure of the temperaof said responsive devices being arranged to adjust said condition responsive means.

2. In an air conditioning system, in combination, an evaporator, means for passing air to be conditioned in heat exchange relationship with said evaporator and to a 'spaceto be conditioned, a compressor for supplying refrigerant to said evaporator and for reducing the pressure in said evaporator, a controller ior varying the output of said compressor, means responsive to a condition whichis a measure of the temperature of said evaporator for actuating said controller for varying the compressor output in a manner to increase said output upon an increase in said evaporator temperature and to decrease said output upon a decrease in said evaporator temperature, valve means for controlling the flow of refrigerant into said evaporator, means responsive to the humidity of the air in said space for adjusting said condition responsive means in a manner to cause decrease in evaporator temperature upon an increase in humidity within said space, and means responsive to the temperature of the air in said space for controlling said valve means.

3. In an air conditioning system, in combination, a heat exchange device through which air is adapted to be passed for a conditioning action, means for supplying heat exchange fluid to said heat exchange device including a compressor,

an internal combustion engine for driving said compressor, a, controller for varying the output of said internal combustion engine, space temperature responsive means for adjusting said controller to vary the engine output in accordance with space temperature to maintain said space temperature constant, means responsive to outside temperature for adjusting said space temperature responsive means, and means actuated when the engine output is reduced to a predetermined low value for placing said engine out of operation.

4. In an air conditioning system, in combination, a heat exchange device through which air ture of said evaporator tor actuating said controller for varying the compressor output in a manner to increase said output upon an increase in said evaporator temperature and to decrease said output upon a decrease in said evaporator temperature, valve means for controlling the flow of refrigerant into said evaporator, a temperature responsive device, and a humidity responsive device, one of said responsive devices being ar ranged to control said valve means, and the other is adapted to be passed for a conditioning action, means for supplying heat exchange fluid to said heat exchange device including a compressor, an internal combustion engine for driving said com.- pressor, a controller for varying the output of said'internal combustion engine, space temperature responsivet means for adjusting said controller to vary the engine output in accordance with space temperature to maintain said space temperature constant, means responsive to humidity for adjusting said space temperature responsive means, and means actuated when the engine output is reduced to a predetermined low value for placing said engine out of operation.

5. In an air conditioning system, in combination, an evaporator in heat exchange relationship with air of a space to be conditioned, a

compressor connected to said evaporator for supplying refrigerant thereto and for withdrawing refrigerant therefrom, an internal combustion engine for driving said compressor, a controller sponse to an increase in space humidity, means indicative of a change in the load on said evaporator for also exerting a controlling influence on said motor means, and stopping and starting means for said internal combustion engine, said stopping and starting means being arranged to cause stopping of said engine when said controller is positioned to demand an engine output below a predetermined minimum value, and to cause starting of said engine when the controller is positioned to demand an engine output above a predetermined value.

6. In an air conditioning system, in combination, a heat exchange device through which air is adapted to be passed for a conditioning action,

' said heat exchange device being of constant ef- Y fective heat exchange area, means for supplying tle valve for controlling the'speed of said internal combustion engine, control means influenced by the pressure in the evaporator for controlling said throttle valve in a manner to increase the output of the engine upon increase in said pressure, a valve for controlling the flow of refrigerant into said evaporator, a device influenced by the heat content of the space for controlling said valve in a manner to close said.

valve when said space does not require refrigeration while opening said valve when the space requires refrigeration, and a device actuated with said throttle valve for starting and stopping said engine.

8. In an air conditioning system, in combination, an evaporator over which airis passed for conditioning the air in a space, a variable capacity compressorconnected to said evaporator for withdrawing refrigerant therefrom, said compressor having an output controller, means influenced by the pressure in the evaporator for controlling said output controller in a manner tending to maintain the evaporator pressure constant, a valve for controlling the flow of refrigerant into said evaporator, temperature responsive means responsive to space temperature, humidity responsive means responsive to space humidity, one of said responsive means adjusting said pressure influenced means and the other of said responsive means controlling said valve, and a device actuated by said output controller for placing said compressor out of operation when the output is reduced to a predetermined value.

9. In an air conditioning system, in combination, an evaporator over which air is passed for conditioning the air in a space, a variable capacity compressor connected to said evaporator for withdrawing refrigerant therefrom, said compressor having an outputcontroller, meansinfluenced by the pressure in the evaporator for controlling said output cohtroller in a manner tending to maintain the evaporator pressure constant, means responsive to the humidity in the space for adjusting said pressure influenced means for thereby varying the temperature of the evaporator in accordance with changes in humidity, a valve for controlling the flow of refrigerant into said evaporator, a thermostat responsive to the temperature in the space for controlling said valve, and a device actuated by said output controller for placing said compressor out of operation when the compressor output is reduced to a predetermined value.

10. In an air conditioning system, in combination, an evaporator, means for passing air to be conditioned in heat exchange relationship with said evaporator and to a space to be conditioned, a compressor for supplying refrigerant to said evaporator and for reducing the pressure in said evaporator, an internal combustion engine for driving said compressor, a controller for varying the output of said internal combustion engine, motor means for positioning said controller, c'ontrol means responsive to a condition which is a measure of evaporator temperature for controlling said motor means, and means responsive to the humidity of the air for adjusting said control means for thereby varying the evaporator temperature in accordance with changes in humidity.

11. In an air conditioning system, in, combination, an evaporator, means for passing air to be conditioned in heat exchange relationship with said evaporator and to a space to be conditioned, a compressor for supplying refrigerant to said evaporator-and for reducing the pressure in said evaporator, an internal combustion engine-for driving said compressor, a controller forvarying the output of said internal combustion engine, motor means for positioning said controller, control means responsive to a condition which a measure of evaporator temperature for controlling said motor means, means responsive to th humidity of the air for adjusting said control means for thereby varying the evaporator temperature in accordance with changes in huj midity, and means actuated when the output of the internal combustion engine is reduced to a predetermined low value for placing said engine out of operation.

12. In an air conditioning system, in combination, a heat exchange device through which air is adapted to be passed for a conditioning action, means for supplying heat exchange fluid to said heat exchange device including a compressor, an internal combustion engine for driving said compressor, a controller for varying the output of said internal combustion engine, electrical means for starting said engine and for ad: lusting said controller, a control device including a movable member in control of said electrical means, space temperature responsive means'for moving said movable member in a manner to control said electrical means to start said engine on a first rise in space temperature and to increase the engine output on further ris in space temperature to maintain said space at desired values, and means responsive to outsid temperature for adjustingsaid space temperature responsive means.

13. In an air conditioning system, in combination, a cooling device through which air is adapted to be passed for a conditioning action, means for supplying cooling fluid to said cooling device comprising a compressor, an internal combustion engine for driving said compressor, a controller for varying the output. of said internal combustion engine, motor means for positioning said controller, control means responsive to a condition which is a measure of the temperature of said cooling device for controlling said motor means, and means responsive to the humidity of the air for adjusting said control means for thereby varying the action of said cooling device in accordance with changes in humidity.

14. In an air conditioning system, in combination, a cooling device through which air is adapted to be passed for a conditioning action, means for supplying cooling fluid to said cooling device comprising a compressor, an internal combustion engine for driving said compressor, a controller for varying the output of said internal combustion engine, motor means for positioning said controller, control means responsive to variations in the load on said cooling device for controlling said motor means, means responsive to the humidity Of the air for adjusting said control means for thereby varying th action of said cooling device in accordance with changes in humidity, and means actuated when the output of the internal combustion engine is reduced to a predetermined low value for placing said engine out of operation.

15. In an air conditioning system, in combination, a cooling device through which air is adapted to be passed for a conditioning action, means for supplying cooling fluid to said cooling devic comprising a compressor, an internal combustion engine for driving said compressor, a controller for varying the output of said internal combustion engine, motor means for positioning said controller, control means responsive to variations in the load on said cooling device for controlling said motor means, means responsive to the humidity of the air for adjusting said control means for thereby varying the action of said cooling device in accordance with changes in humidity, and means actuated when said controller is positioned to demand an engine output in excess of a predetermined low value for causing starting of the engine in the event that the engine is not in operation.

16. In an air conditioning system, in combination, a cooling device through which air is adapted to be passed for a conditioning action, means for supplying cooling fluid to said cooling device comprising a compressor, an internal combustion engine for driving said compressor, a controller for varying the output of said internal combustion engine, motor means for positioning said controller, control means responsive to variations in the load on said cooling device for controlling said motor means, means responsive to the humidity of the air for adjusting said control means for thereby varying the action of said cooling device in accordance with changes in humidity, and means actuated with said controller for stopping and starting said internal combustion engine, said last named means being arranged to stop the engine when the controller is positioned to demand an engine output below a predetermined low value and to start the engine when said controller is positioned to demand an engine output in excess of a predetermined low value.

17. In a refrigeration system, in combination, an evaporator for changing the heat content of a space, variable capacity compressor means con-c nected to th evaporator, an output controller for varying the output of the compressor means, control means influenced by the pressure in the evaporator for controlling the output controller in a manner to increas the output of the compressor means upon increase in pressure, a first device influenced by a condition of th air in said space which is affected by the temperature of the evaporator for adjusting said control means to thereby vary the temperature of the evaporator upon change in said condition, valve means {or controlling the flow of refrigerant into the evaporator, and a second device influenced by the heat content of said space for controlling said valve means.

JOHN E. HAINES.