US2060589A - Refrigeration - Google Patents

Description

Nov. 10, 1936. c. A. OTTO 2,060,589

. REFRIGERATION Filed Oct. 2, 1935 2 Sheets-Sheet 1 =31! CTION PRES SU'KE.

KEGU LATXNG VALVE,

INSIDE THERMOsTAT SUCTION 5W! TCH EVAFOKATOR MAGN ET I C STARTEK:

OUTS

3m entor attorneys C. A. OTTO REFRIGERAT ION Nov. 10, 1936.

3nventor W Q H @ll 4 Gm u 7 g 3 2 i E 9 x F 3 2 2 m M 3 i Ur l m w Al Q Q .T P Q mm mw a x:

Gttornegs Patented Nov. 10, 1936 PATENT OFFICE 2.0 0.589 REFRIGERATION Carl A. Otto, Milwaukee, Wis., assignor to Johnson Service Company, Milwaukee, Wis., a corporation of Wisconsin Application October 2, 1935, Serial No. 43,267.

8Claims. (01. 6 2-8) This invention relates to refrigeration and particularly to air conditioning under summer conditions by the use of direct expansion coolers forming part of the refrigerating circuit.

In pending application Serial No. 35,539, filed August 9, 1935, I describe and claim a device of this character in which an expansion valve of the automatic type is controlled in response to superheat of the refrigerant leaving the evaporator, evaporator pressure, and a temperature condition created by the operation of the evaporator. The temperature condition discussed in that prior application is the differential between an indoor temperature and outdoor temperature.

Certain refrigerative circuits are operated at constant suction pressure and in such case the evaporator pressure would disappear as a regulatory factor. The purpose of the present invention is to disclose a modified embodiment of my prior invention in which the evaporator is operated at constant pressure and in which the expansion valve is regulated solely by thermostatic means; that is to say in response to superheat of the refrigerant and in response to a temperature condition created by the operation of the evaporator.

Broadly considered it is not essential that the expansion valve used in such a system be indifferent to evaporator pressure for the fact that evaporator pressure is constant makes it possible to introduce a constant balancing force with theresult that the valve is properly balanced under operating conditions whether it be indifferent to evaporator pressure or not. However, better results are secured with a valve which actually is indiiferent to evaporator pressure, because as a matter of practice it is not practicable to maintain evaporator pressure absolutely constant. For the purposes of this case a valve indifferent to pressure will be regarded as a special instance of a valve which is in effect balanced under constant suction pressure conditions.

The expansion valve herein disclosed includes three thermostatic controls, one of which responds to superheat, one of which responds to an indoor temperature, and another of which responds to an outdoor temperature and exercises a modifying control. Certain of these thermostatic controls may take effect individually and under certain circumstances they may take control collectively, this for the reason that the regulatory effect is permissive in one direction so that under certain conditions one or another control may exert exclusive efiect. Means are provided to adjust the superheat control by means of a loading spring, and means are provided to adjust the relation of the outdoor to the indoor control.

While I have referred to outdoor temperature, it is important to state that this outdoor temperature may be dry bulb temperature, wet bulb temperature, effective temperature (a combination of wet bulb and dry bulb temperatures) or a temperature developed by radiation. Thermostatic elements which will respond to each of these temperatures are well known and their specific construction is not a feature of the present invention.

4 A simple embodiment of the invention will now be described with reference to the accompanying drawings, in which,-'

Fi 1 is a diagram of the conditioning circuit.

Fig. 2 is an axial section through the expansion Valve- 20 Fig. 3 is a conventional representation of a wet bulb thermostatic unit which may be used out of doors.

Fig. 4 is a conventional representation of an effective temperature thermostatic unit which may be used out of doors.

Fig. 5 is a conventionalrepresentation of a thermostatic unit responsive to radiant heat.

Referring first to Fig. 2, the body of the expansion valve comprises an annular member "I having a chamber 8 from which a discharge passage 9 leads. Inlet passage ll communicates through a radial arm l2 which projects into the chamber 8 and is provided with a downwardly facing valve seat ill at the center of the chamber This seat controls flow entering throughthe passage II and discharging into the chamber 8. Housing 1 is mounted on a hollow casing I4 which encloses the lever mechanism and serves as a support for the thermostatic motors hereinafter described.

Interposed between the housing 1 and the casing I4 is the marginal flange of a cup-shaped member l5 which'serves as a sealing gasket and also as a support for the corrugated metallic 5 bellows IS. The lower end of the bellows is sealed to the member l5 and the upper or movable end is sealed to a head I! which is in thrust relation with a bifurcated yoke l8. This yoke carries a needle valve I!) which coacts with the valve seat I3 and controls the supply of liquid refrigerant to the chamber 8. The upper side of the housing I is closed by a cap 2|. This seats on the marginal flange of a cup-shaped member 22, which, like the member l5, serves partly as a sealing gasket.

The member 22 supports corrugated metallic bellows 23, whose free or movable end is sealed to a head 24. The head 24 is in thrust relation with the upper end of the yoke l8 already described.

A coiled compression spring 25 is housed within the cap 2| and reacts in downward thrust upon the head 24. Since the two bellows are of equal diameters the valve I9 is indifferent to pressure within chamber 8. The yoke I 6 is preferably rigidly attached to the heads I! and 24. Acting upward in thrust against the head I1 is a slotted rod 26 which is guided to move vertically in the direction of its axis by means of guideways 21 formed in the. casing [4. It responds at times to the individual and at times to the combined effects of several thermostatic motors. The action is modified by an adjustable spring. One thermostatic motor responds to superheat of refrigerant leaving the evaporator and exerts a valve opening effect on rising temperature. Another control is effected by two opposed thermostatic motors, one of which responds to indoor temperature and exercises a valve-opening effeet on rising temperature, and the other of which responds to outdoor temperature and exerts a valve closing effect upon rising temperature. The force relation between the last two motors when they act conjointly is subject to modification by a shifting fulcrum.

The superheat control motor comprises a base 30 which is adjustably mounted on a portion of casing M by a nut 28 which is threaded on the casing l4 and swiveled on the base 30. Rotation of the nut therefore shifts the base 30 vertically. Mounted on the base 30 is a metallic bellows 29 having a closed head 3| which reacts in doWn- .develops increasing pressure on rising temperature. This thermostat might take many forms, but in Fig. 1 it is indicated as a bulb 35 containing an expansible liquid which responds appropriately to rising temperature. In Fig. 1 bulb 35 is shown clamped against the suction line leading from the evaporator.

A coil compression spring 36 reacts against a flange 31 on rod 32 and is sustained by an adjustable spring seat 38 which is threaded in a portion of the casing l4. By turning the spring seat 38 the stress on the loading spring 36 may be adjusted.

Pirmed to rod 32 is a lever 39 which is fulcrumed at 4| and is in thrust engagement with a pin 42 passing through the slotted portion of rod 26. Lever 39 extends through the slot in the rod, as clearly indicated in the drawings. In this way a one-way thrust connection between the lever 39 and the rod 26 is afforded, so that the effect of the superheat control on the expansion valve is permissive in an opening direction but positive in a closing direction.

Control is normally exercised on the rod 26 by a lever 43 which is fulcrumed at 44 in casing l4 and reacts upward against the pin 45 extending through the slot in the rod 26. The lever extends through the slot in the rod and is in oneway thrust engagement with pin 45, so that the modifying control is permissive in a valve opening and positive in a valve closing direction. The lever 43 is operated primarily by the indoor motor, generally indicated at 46. The outdoor motor, generally indicated at 41, introduces a moditying effect on the action of the indoor motor 46.-

The structure of these motors, including the adjusting means, is identical with that already described with reference to parts 28-33 inclusive, and this detailed description need not be repeated. The only structural difference is that motor 46 includes a coil compression spring 48 which resists downward motion of the motor element, as will be apparent from an inspection of the drawings.

The working space of motor 46 is connected by a tube 49 with the indoor thermostat 5|. Thermostat 5| may be of any type which will develop a rising fluid pressure in the tube 49, and motor 46, in response to rising temperature. An ordinary thermostatic bulb is indicated in the drawings, but in some cases the use of a pneumatic relay thermostat of the progressive relay type would be preferred particularly if the length of the tube 49 be considerable. Thermostats of this type are well known in the art, and a-suitable one is illustrated in Patent to Otto, No. 1,500,260, July 8, 1924.

The bellows of motor 46 reacts downward through a push rod 52 upon lever 43. The outdoor motor 4'! is connected by a tube 53 with the outdoor thermostat 54, which may be of any type developing in the tube 53 and motor 41 a pressure which rises in response to rising tem-.

perature. In the drawings a thermostatic bulb is indicated but a pneumatic relay thermostat of the type already mentioned would be preferable where the line 53 has considerable length. The particular form of the thermostats to be used to develop the necessary pressure in the thermostatic motors is not a feature of the invention and is largely a matter ofchoice.

The bellows of motor 4'! reacts through a push rod 55 upon a short lever 56 pivoted at 5'! in the casing l4. swiveled in the lever 56 and extending longitudinally thereof is a threaded rod 56. This rod may be turned by a knurled adjusting head 59 and carries threaded upon it a fulcrum block 6| which has a knife edge engaging the lever 43 in one-way thrust and which has a bifurcated lower portion 62 which straddles the lever 56 and holds the block against rotation. By turning the knurled head 59 the fulcrum block 6| is traversed in the direction of the length of the lever 56 and by changing the ful- Fig. 3, or into an effective temperature thermo-- stat by giving it a partial wet envelope 64, as indicated in Fig. 4. It can be caused to respond to radiant heat by enclosing it in a black copper hollow sphere 65, as indicated in Fig. 5, and the interchangeable use of these different types of thermostatic units is contemplated.

In Fig. 1 the expansion valve of the type described is shown inserted in an air conditioning system of the direct expansion constant suction pressure type.

tioned room or space enclosed as indicated. A recirculation duct 68 leads recirculated air to .the intake of the conditioner, while the louvers 69, which may be manually or otherwise adjusted.

In this figure 66 is the housing ,of the conditioner and 6'! represents the condioutdoor temperature.

admit fresh air. The air entering through the recirculation duct and the louvers mixes and passes in contact with the evaporator H from which it passes to the total volume fan 12 and thence to the conditioned space 61. Any preferred air circuit may be used and the use of washing sprays is possible but not a feature of the invention and consequently not illustrated. The same applies to preheaters, reheaters and other equipment familiar in the art and not entering into the claimed invention.

Leading from the evaporator II is the suction line 13 to which the thermostatic bulb 35 is attached. This line leads through a suction pressure regulating valve 14 and a suction pressure switch to a compressor 16 driven by a motor 11. The suction pressure regulating valve I4 is merely a diaphragm operated pressure reducing valve which maintains the pressure in the evaporator 'Il constant within relatively close limits. Valves of this type are too well known to require detailed description.

The suction pressure switch 15 is used to prevent the compressor 16 from operating at too low suction pressure and its function is to operate through a magnetic starter 18 to reduce the speed of the motor 11 and the compressor 16 at times when the suction pressure regulating valve 14 is so nearly closed that the compressor would operate at an unduly low suction pressure if maintained at full speed. This scheme of regulating suction pressure by a suction pressure reg- 'ulating valve while the speed of the compressor is varied to prevent ineflicient operation is one of various systems used in the refrigerating art pansion valve and pipe 84 connected thereto to the evaporator H.

Since the suction pressure is substantially constant, it is unnecessary and in fact impracticable to cause the expansion valve to respond to suction pressure. Thus it is possible and desirable to avail of the free-operating characteristics of a balanced valve, particularly a valve indifferent to pressure.

The operation of the device can now be outlined. The existence of superheat at the bulb 35 will develop pressure in motor 30 and permit the valve l9 to open wide. It will open wide as the system is started up. After the system has been in operation the thermostat 5| will take control through motor 46 and this control may or may not be modified by thermostat 54 through motor 41, depending on the differential between the control point of thermostat 5| and outside temperature.

The purpose of the difierential control is to limit the depression of indoor temperature below The limit so placed may be varied by: adjusting fulcrum 6i.

During normal operation the thermostat 35 does not control, but it may assume control if the thermostat 5| makes an abnormal demand forrefrigeration, as it does in starting up the system, and as it may do under certain abnormal conditions in the refrigerated space producing an excessive heat load. The thermostat 35 may temporarily assume control if the thermostat 54 functions to produce a marked change in the controlling action of thermostat 5|.

Thus the controls by superheat and by space temperature are alternative in effect, and the selection between the two is automatically made on the basis of selecting that control which indicates the lower demand for refrigerant. Thus the coil is never overloaded with refrigerant and all danger of wrecking the compressor is avoided.

While a particular embodiment of the invention has been described in detail, the invention is broader than any particular means for carrying it out. Hence the disclosure is intended to be illustrative rather than limiting, the scope of the invention being defined solely by the claims.

What is claimed is,-

1. The method of controlling the refrigerative effect of a space-cooling evaporator, which comprises, withdrawing refrigerant vapor from the evaporator and varying the rate of withdrawal to maintain a constant suction pressure; admitting liquid refrigerant to the evaporator and controlling the rate of admission in response alternatively to the temperature of discharging refrigerant vapor and to the space temperature created by the evaporator; and selecting between such alternative temperature controls on the basis of the lower demand for refrigerant.

2. The method of controlling the refrigerative effect of a space-cooling evaporator, which comprises, withdrawing refrigerant vapor from the evaporator and varying the rate of withdrawal to maintain a constant suction pressure; admitting liquid refrigerant to the evaporator and controlling the rate of admission in response alternatively to the temperature of discharging refrigerant vapor and to the space temperature created by the evaporator; selecting between such alternative temperature controls on the basis of the lower demand for refrigerant; and modifying the second-named control in accordance with an external temperature which affects heat leakage to said cooled space.

3. In a refrigerating system, the combination of a source of liquid refrigerant; a space cooling evaporator; means for maintaining a substantially constant suction pressure in said evaporator; an expansion valve controlling the supply of liquid refrigerant to said evaporator; and at least two thermostatic controlling means for said valve, one of which responds to the temperature of refrigerant leaving said evaporator and another to the 'space temperature created by said evaporator, said controlling means being so arranged that either may move said valve in a closing direction unaffected by the other.

4. In a refrigerating system, the combination of a source of liquid refrigerant; a space cooling evaporator; means for maintaining a substan-' tially constant suction pressure in said evaporator; an expansion valve substantially indifferent to pressure in-the evaporator and controlling the supply of liquid refrigerant to said evaporator; and at least two thermostatic controlling means for said valve, one of which responds to the temperature of refrigerant leaving said evaporator and another to the space temperature created by said evaporator, said controlling means being so arranged that either may move said valve in a closing direction unaffected by the other. K

5. In a refrigerating system, the combination of a source ofliquid. refrigerant; a space cooling evaporator; means for maintaining a substantially constant suction pressure in said evaporator; an expansion valve controlling the supply of liquid refrigerant to said evaporator; and three thermostatic controlling means for said valve, one of which responds to the temperature of refrigerant leaving the evaporator, another to the space temperature created by the operation of said evaporator, and the third to a temperature external to the space and affecting heat leakage thereto, the parts being so arranged that the first controlling means may move said valve in a closing direction unaffected by the second and third, and the second and third by their combined effect may move the valve in a closing direction unaffected by the first.

6. In a refrigerating system, the combination of a source of liquid refrigerant; a space cooling evaporator; means for maintaining a substantially constant suction pressure in said evaporator; an expansion valve substantially indifferent to pressure in the evaporator and controlling the supply of liquid refrigerant to said evaporator; and three thermostatic controlling means for said valve, one of'which responds to the temperature of refrigerant leaving the evaporator, another to the space temperature created by the operation of said evaporator, and the third to a temperature external to the space and affecting heat leakage thereto, the parts being so arranged that the first controlling means may move said valve in a closing direction unaffected by the second and third, and the second and third by their combined effect may move the valve in a closing direction unaffected by the '7. In a refrigerating system, the combination of an evaporator; an expansion valve for supplying refrigerant to said evaporator, said valve being substantially indifferent to evaporator pressure; means biasing said valve in an opention on rising temperature, said differential thermostat exercising a permissive control on said valve in an opening direction and a positive control in a closing direction.

8. In a refrigerating system, the combination of an evaporator; an expansion valve for supplying refrigerant to said evaporator, said valve being substantially indifferent to evaporator pressure; means biasing said valve in an opening direction; means for maintaining a substantially constant suction pressure in said evaporator; thermostatic means subject to the discharge temperature of the evaporator and exercising a permissive control on said expansion valve in an opening direction upon rise of discharge temperature; differential thermostatic means comprising two thermostatic devices, one subject to the temperature of the space refrigerated by the evaporator and the other subject to an outdoor temperature, in operation the two thermostats being opposed to each other, the indoor thermostat functioning in a valve opening direction on rising temperature, said differential thermostat exercising a permissive control onsaid valve in an opening direction and a positive control in a closing direction; and adjustable means for modifying the leverage relation between the indoor and outdoor thermostatic means.

CARL A. O'I'IO.

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