US2572501A - Refrigerant control system - Google Patents

Description

Oct. 23, 1951 H. J. MATTESON 2,572,501

REFRIGERANT CONTROL SYSTEM F iled April 9', 1948 5 Sheets-Sheet 1 & 27' 24 3 mentor.

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REFRIGERANT CONTROL SYSTEM Filed April 9, 1948 3 Sheets-Sheet 2 suctrion um:

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REFRIGERANT CONTROL SYSTEM Filed April 9, 1948 H 3 Sheets-Sheet 3 sum-16H um: 9 9

SUCTION Ll HE "mvEHToR'; L01 MQTTESO/Y M I attorney Patented Oct. 23, 1951 UNITED STATES PATENT OFFICE 2,572,501 REFRIGERANT CONTROL SYSTEM Harold J. Matteson, Glendale, Callf., assignor to General Controls 00., Glendale, Calif., a corporation of California Application April 9, 1948, Serial No. 19,935

12 Claims.

This invention relates to refrigerating systems of the mechanical type, and wherein a conventional thermostatic expansion valve is employed for maintaining the cooling unit, during the oncycle of the system, in a nearly-flooded condition while allowing only dry refrigerant to pass to the compressor.

In such a system, the thermostatic means for controlling the operation of the expansion valve is usually in the form of a thermal bulb strapped to the suction line at the outlet of the cooling unit. When the arrangement is such that there is considerable heat-leakage at the bulb location, the possibility arises that, due to the effect of this heat-leakage upon the control of the expansion valve, refrigerant may be passed to the cooling unit during the off-cycle of the system. This may result in the flooding of the evaporator coil with relatively-warm refrigerant and consequent frost-back and erratic or inefilcient operation of the system at the beginning of its on-cycle.

Heat-leakage at the bulb location is especially troublesome in connection with low-temperature refrigeration systems such as those for ice-cream storage cabinets and domestic deep-freezers. The cooling chamber of such freezers is usually in the form of a tank having smooth sides so that it can be defrosted by scraping. Consequently the controls must be mounted at the outside, and it is common practice to provide a control compartment by cutting away a portion of the thick insulating material which surrounds the cooling unit. Because of space limitations, and the low temperatures involved, it is impracticable to provide sufllcient insulation to maintain this control compartment at a temperature near that of the cooling unit, so that the heatleakage is excessive.

It is an object of this invention to overcome the effect of heat-leakage at the bulb location, and I accomplish this object by providing means whereby refrigerant can be conducted, independently of the evaporator coil, in thermal-transfer relation to the bulb in an amount just sufficient to compensate for the efiect of the heat-leakage.

Another object of this invention is to combine, with the means recited in the preceding object, means for positively preventing overloading of the compressor at the beginning of the on-cycle.

For full understanding of the invention, and further appreciation of its objects and advantages, reference is to be had to the following detailed description and accompanying drawing, and to the appended claims.

In the drawing:

Figure 1 is a schematic view of a conventional refrigeration system, showing a cooling unit of the low-temperature type commonly employed for domestic freezers or the like; and

Figures 2 through '1 are views, mainly in elevation, of various individual arrangements and constructions of apparatus embodying features of this invention and whereby, in the control of a refrigerating system such as that shown in Fig. l, refrigerant can be conducted, independently of the evaporator coil, in thermal-transfer relation to the thermal bulb of an ordinary thermostatic expansion valve in an amount only suflicient to compensate for the effect of heat-leakage at the bulb location.

In Fig. 1, the numeral H generally indicates a cooling unit comprising a tank-like metallic structure 12, defining the freezing chamber, around which is the evaporator coil 13. At the sides and bottom of the cooling unit is thick insulating material l4, and at its top is an insulated cover l5. At one side of the unit the insulating material is cut away to provide a compartment I6 for accommodation of the control apparatus shown in the other figures of the drawing; the compartment conveniently being about 9 to 12 inches square and 4 inches deep, and having a door or cover II. The other apparatus shown in Fig. 1 is of the kind commonly employed in mechanical refrigerating systems and comprises an electrically-driven compressor l8, a condenser l9, and receiver 20; the numeral 2| indicating the suction line from the outlet of the coil, and numeral 22 the line leading to the inlet of the thermostatic valve.

The compressor is provided with the usual cycling switch responsive to coil and crankcase pressure and acting to initiate the on-cycle by starting the compressor when that pressure reaches a predetermined maximum due to rise of temperature of the cooling unit, and to stop the compressor and thereby initiate the 0dcycle when the coil pressure falls to a predetermined minimum; the cycling switch, indicated at in Fig. 1, being connected by a pipe 8| to suction line 2| and by wires 82 to the compressor motor in series with a source of A. C. indicated by the symbol. a single cooling unit, the compressor cycling switch may, alternatively, be of the thermostatic type responsive to corresponding variations of the temperature of the cooling unit.

The thermostatic expansion valve indicated in each of Figs. 2 through 7 by the numeral 23 may If the installation comprises but be of the conventional type which comprises valve means operatively connected to a diaphragm, one side of which is subjected to the pressure (acting in a direction to close'the valve means) at the outlet of the valve (and inlet of the evaporator coil), and whose other side is subjected to the pressure (acting in a direction to open the valve means) produced by a charge of refrigerant contained in a thermal bulb 24 connected to the valve by a capillary tube 25; a spring, whose force determines the super-heat setting of the valve, biasing the valve means toward closed position. A valve of this general character is disclosed in my Patent No. 2,327,542 issued August 24, 1943.

- In each of Figs.'2 through '7 the legend Suction Line indicates the portion of the outlet one of the coil ends 26, shown in Fig. 1, by which the same is connected to the suction line 2| of the same figure; the other or inlet end of the coil being the one designated by the legend "To ,Coil in Figs. 2 through 7. The showing of Fig. 1 is only schematic, and it is to be understood that the ends of the evaporator coil may be brought out in any convenient manner to suit the individual arrangements shown in the other figures.

The thermal bulbs 24 are shown attached to the suction line, in the usual manner, by apertured straps 21.

Referring ,now more particularly to Fig. 2, which illustrates the simplest embodiment of this invention, the numeral 28 indicates a tube which is connected at both of its ends to a pipe 29, .which pipe connects the outlet of the thermostatic expansion valve 23 to the inlet of the evaporator coil; holes being drilled in the pipe,

at points spaced longitudinall thereof, to receive the ends of the tube which are secured in place, as by brazing. with their extremities substantially flush with the drilled wall of the pipe. The tube 28 is bent to form a loop 30 in proximity to the thermal bulb 24, so that it is in good thermal-transfer relation thereto, and

-is held in place as by a wrapping of insulating tape (not shown).

In the operation of the refrigerating system. during the off-cycle the pressure is building-up in the evaporator coil whose circuit is closed at one end by the compressor check-valve, and at the other by the expansion valve 23. The expansion valve normally cannot open during the off-cycle since the fluid pressures-n opposite sides of its diaphragm, or equivalent partition, are then substantially balanced and the full force of the super-heat control spring is therefore effective to maintain the valve closed. However, in the event that the temperature at the thermal bulb should rise sufiiciently higher than that in the coil of the evaporator, opening of the expansion valve will be effected so that refrigerant is supplied to the coil with the result that the same may become fiooded with unevaporating refrigerant; considerable damage then ensuing at the beginning of the on-cycle due to frostback, etc, as is well known.

Such abnormal rise of temperature at the thermal bulb can commonly occur in connection with freezers of the type disclosed in Fig. 1 due to heat-leakage with respect to the control compartment l5. If, due to heat-leakage at the bulb location, the expansion valve should open during the off-cycle, the refrigerant upon entering the pipe 29 passes by gravity into the loop 30 so that the same is filled with the refrigerant which serves to so cool the bulb that the ex- 76 4 pansion valve recloses almost immediately; the amount of refrigerant which can pass to the evaporator coil before reclosing of the valve being insufiicient to establish an abnormal condition therein. If the heat-leakage is excessive, momentary opening and reclosing of the expansion valve may occur several times before the beginning of the on-cycle. V v

During the on-cycle of operation, the amount of refrigerant passing from the evaporator coil at the bulb location is usually sufiicient to off-set the eflect of heat-leakage; flow of refrigerant through the loop 30 being restricted by a pinched portion 3| of the tube so that its effect upon the system during the on-cycle is too small to interfere appreciably with the normal functioning of the expansion valve.

The control system shown in Fig. 3 differs from that of Fig. 2 only in such arrangement of the parts that the refrigerant is delivered, during the off-cycle, to the compensating loop 32 by velocity efiect rather than by gravity; the inlet end of the tube 33. which forms the loop, being extended within the pipe'34 and cut angularly to form a scoop, as indicated at 35, for facilitating entry of the refrigerant. This arrangement may be substituted for that of Fig. 2 if space limitations preclude suificient spacing-apart of the ends of the compensating tube to obtain the desired gravity-head in the arrangement of Fig. 2. The operation of the control system of Fig. 3 is substantially the same as was described in connection with the system of Fig. 2; the tube 33 likewise being pinched at 36 for the purpose described.

In the arrangement of Fig. 4 a needle valve 31 (corresponding in function to the pinched portions 3| and 36 of Figs. '2 and 3) is provided for adjusting the rate of maximum flow through the compensating tube 38. This valve comprises a threaded needle 39 mounted in a boss portion of a fitting 40 which is connected at one end to the outlet of the expansion valve 23 and is threaded at its other end for connection to the evaporator coil. The needle 39 cooperates with a seat around an opening in the fitting 40, with which opening the outlet end of the compensating tube 38 is connected; the other or inlet end of the tube being connected to the fitting 40 adjacent the expansion valve and provided with a scoop 4| for facilitating entry of the refrigerant. The operation of the control system of Fig. 4 will be apparent in the light of the foregoing descriptions of the systems of Figs. 2 and 3.

In the control system of Fig. 5 means is provided for preventing entry of refrigerant (except when its rate of flow is very low) to the compensating tube 42 surrounding the thermal bulb 24, so that during the on-cycle no refrigerant can normally enter the compensating tube. This means comprises a check-valve 43 mounted in a fitting or pipe 44 which is connected at one end to the outlet of the expansion valve 23 and threaded at its other end for connection to the evaporator coil. This check-valve comprises a hemispherial closure 45 which cooperates with a seat below it around an opening in the fitting 44, with which opening the inlet end of the compensating tube is connected; the other or outlet end of the tube being connected to the fitting adjacent the outlet end of the same. The closure 45 is biased toward open position by a spring 46 whose force is just sufficient to balance the weight of the closure and maintain it unseated when no, or only a very small amount.of, re-

frlgerant is passing through the fitting; a projection 41 from the cap 48 of the check-valve limiting the extent of opening of the closure.

Still referring to Fig. If the thermostatic expansion valve should open during the off-cycle due to heat-leakage at the thermal-bulb location, the liquid refrigerant, initially entering the fitting 44 at low rate, passes by gravity through the open check-valve into the reservoir formed by the compensating tube 42, thereby so cooling the thermal bulb that the expansion valve recloses. During the on-cycle of the system, the friction between the closure 45 and the refrigerant passing at relatively high rate through the fitting effects seating of the closure (as indicated in the figure); the pressure diiference between the ends of the compensating tube, due to a restriction 49 provided in the fitting, also contributing to maintain the closure seated when there is appreciable flow of refrigerant.

By the arrangement of Fig. 6 the same general result is accomplished as by that of Fig. 5, i. e., supply of refrigerant to the compensating tube or loop 50 if the thermostatic expansion valve should open during the off-cycle, and obstruction of the supply to the tube during the on-cycle; a pressure-operated valve 5| being substituted in Fig. 6 for the check-valve of Fig. 5. This pressure-operated valve comprises a casing connected to the outlet of the expansion valve and having a main outlet passage 52 through which the refrigerant can pass independently to the evaporator coil. Communicating with the passage 52 is another passage 53 whose outlet end is defined by means forming a seat for a circular closure 54 which is sealingly secured to one end of an expansible-contractible bellows 55 contained in a tubular extension 55 of the casing, the other or outer end of the bellows being simllarly secured to a plug 51 which is clamped in sealing engagement with the outer end of the extension by a threaded cap 58; the plug 51 and cap 58 being apertured so that the interior of the bellows is exposed to atmosphere. The closure 54 is biased toward closed position by a spring 59 compressed between it and the plug 51.

The pressure-operated valve 5| of Fig. 6 is so biased that it remains closed during the oncycle while the pressure in the evaporator coil (and in passages 52-53) is of a relatively low order, so that refrigerant can then pass only to the evaporator. However, when the pressure builds-up during the off-cycle, to a point approximately midway in the range of pressures occurring in the evaporator during that cycle, this relatively-high pressure acting on the closure 54 moves it out of engagement with its seat so that, in the event that the expansion valve 23 should open during the remainder of the off-cycle, refrigerant can then pass through a passage 50 to the interconnecting compensating-tube 50, the outlet end of which leads to a fitting 5| inserted in the evaporator supply pipe.

The control system of Fig. '7 achieves the same results as those achieved by the system of Fig. 6, and includes, in addition, means for positively preventing overloading of the compressor at the beginning of the on-cycle (due to rapid expansion of the refrigerant freshly supplied to the evaporator), which overloadingis otherwise apt to occur especially if the evaporator is relatively warm, as after defrosting. This overload protection (as well as heat-leakage compensation) is afforded by a pressure-operated three-way valve 52 which serves to direct refrigerant from the thermostatic expansion valve directly to the evaporator coil when the pressure condition therein is of relatively low order, or to direct the refrigerant only by way of the compensating tube 53 if the pressure rise to an abnormal degree.

The valve 52 of Fig. '7 comprises a casing connected to the outlet of the expansion valve and having an outlet passage 64 leading to the evaporator coil. Within the casing is a closure 55 which is cooperable with an upper seat 65 formed around an opening leading to the outlet 54, as well as with a lower seat formed by the top of a hollow member 51 mounted in an opening through the bottom of the casing, to which memher the inlet end of the compensating tube 53 is connected. Within a tubular extension 58 of the casing is an expansible-cantractible bellows 59 whose upper end is sealingly secured to an annular member 10 which is clamped in sealing engagement with the top of the extension by a cap H. The lower end of the bellows is sealingly secured to a disk 12 from the underside of which there projects a stem 13 engageable with the closure 55. Within bellows 69, and compressed between the cap H and disk 12 is a spring 14, which, through the stem 13, biases the closure 65 downwardly toward the position shown in the figure; a light spring 15, below the closure within the member 51, serving to cause the closure to follow the stem 13 when it moves upwardly under conditions to be described (the stem being unattached to the closure).

As shown in Fig. 7 the valve 62 is in its biased position, in which position it remains under lowpressure conditions of the evaporator coil and passage 54 such as normally exist during the on-cycle. With the closure 55 in the position shown, refrigerant can pass from the expansion valve through the inlet 15 of valve 62, and across the upper seat 55 of the same, into the outlet passage 54; passage of refrigerant to the compensating tube 53 being obstructed in this position of the closure.

In the event of abnormal rise of pressure in the passage 54, such as may occur at the beginning of the oncycle if the evaporator coil is relatively warm, the disk or bellows-head I2 is moved upwardly due to this rise of pressure so that the closure is brought into engagement with the upper seat 55, thereby interrupting direct passage of refrigerant to the evaporator coil; refrigerant then passing across the lower seat of the valve to the compensating tube, and thence to the outlet passage 54; the refrigerant in, or passing through, the tube adjacent the thermal bulb soon effecting closure of the expansion valve. The bellows 59 is sealed, but it is of relatively large capacity and contains air normally at atmospheric pressure which offers negligible resistance to the upward movement of the bellows-- head through the short distance necessary to ef-- fect seating of the closure.

The bias of valve 52 is so adjusted that the 010 sure 55 is actuated to its upper position when, the pressure acting on the bellows-head reaches a point about midway in the range of pressures. occurring in the evaporator during the off-cycle of the system, so that in the event that the expansion valve should open, due to heat-leakage at the thermal-bulb location, during the remainder of the off-cycle, the refrigerant passes. only to the compensating tube so that prompt. reclosing of the expansion valve is effected.

An unobvious advantage of this invention is.

7 that, due to the protection aflorded against the entry of refrigerant to the evaporator during the oil-cycle, it is possible to employ a lower superheat setting of the expansion valve, with resultant great r efliciency of operation of both the cooling and the condensing units.

The tube or loop through which the refrigerant is conducted in thermal-transfer relation to the thermal bulb is shown in each of Figs. 2 through 7 as being connected at both of its ends to the pipe or the like which interconnects the expansion valve and the evaporator coil; however, it is apparent that the operation of the compensator would be substantially the same if only the inlet end of the tube were connected to the pipe, and the outlet end of the tube connected to the suction line at the outlet of the evaporator.

The word coil, as employed in the claims, is.

intended to include any means constituting an equivalent passage for the refrigerant in the cooling unit.

The specific embodiments of my invention herein shown and described are obviously susceptible of modification without departing from the spirit of the invention, and I intend therefore to be limited only by the scope of the appended claims.

I claim as my invention:

1. In a refrigerating system: a cooling unit comprising a coil; means for passing refrigerant through said coil; a thermostatic expansion valve for controlling passage of said refrigerant, and comprising means responsive to the temperature at the outlet end of said coil for controlling the operation of the valve; means constituting a pipe connecting the outlet of said valve to the inlet of said coil; and means comprising a tube connected at both of its ends to said pipe for conducting refrigerant, passing into said pipe from said valve, in thermal-transfer relation to said temperature responsive means in an amount only suflicient to compensate for heat leakage thereadjacent.

2. The combination defined in claim 1, and wherein said tube is formed to provide a reservoir for liquid refrigerant.

3. The combination defined in claim 1 wherein said tube is formed to provide a reservoir for liquid refrigerant, and including means for restricting flow of refrigerant with respect to said reservoir.

4. The combination defined in claim 1, and wherein the arrangement is such that refrigerant can pass to said tube by gravity.

5. In a refrigeration system: a cooling unit comprising a coil; means for passing refrigerant through said coil; 9, thermostatic expansion valve for controlling passage of said refrigerant, and comprising means responsive to the temperature at the outlet end of said coil for controlling the operation of the valves; means constituting a pipe connecting the outlet of said valve to the inlet of said coil; and means for. conducting refrigerant in thermal-transfer relation to said temperature responsive means to compensate for heat leakage thereadjacent, comprising a tube connected at both of its ends to said pipe, and a check-valve controlling passage of refrigerant through said tube, said check-valve being biased to open position and adapted to close upon increase of refrigerant-flow through said pipe.

6. In a refrigeration system of the type which comprises means for passing refrigerant through the coil of a cooling unit, and means for effecting on-cycle and off-cycle operation of the system in accordance with the requirements of for controlling passage of said refrigerant, and comprising means responsive to the temperature at the outlet end of said coil for controlling the operation of the valve; means constituting a pipe connecting the outlet of said valve to the inlet of said coil; and means for conducting refrigerant in thermal-transfer relation to said temperature responsive means to compensate for heat leakage thereadjacent, comprising a tube connected to said pipe, and a pressure-operated valve controlling passage of refrigerant through said tube, said pressure-operated valve being biased to closed position and adapted to open with rise of pressure of the refrigerant in said pipe and coil resulting from off-cycle operation of the system. so as to permit refrigerant to, pass to said tube in the event that said thermostatic valve opens during the off-cycle.

'7. The combination defined in claim 6, and wherein said tube is connected at both of its ends to said pipe.

8. In a refrigeration system of the type which comprises means for passing refrigerant through the coil of a cooling unit, and means for effecting on-cycle and off-cycle operation of the system in accordance with the requirements of the cooling unit: a thermostatic expansion valve for controlling passage of said refrigerant, and comprising means responsive to the temperature at the outlet end of said coil for controlling the operation of the valve; means constituting a pipe connecting the outlet of said valve to the inlet of said coil; means for conducting refrigerant in thermal-transfer relation to said temperature responsive means, comprising a tube connected at one of its ends to said pipe; an additional valve, at the junction of said tube with said pipe, for directing the passage of refrigerant entering the pipe from said thermostatic expansion valve; and means for operating said additional valve in response to variations of the pressure condition in said coil, so that (l) unrestricted passage of wherein said additional valve includes means for obstructing passage of refrigerant through said tube when said pressure condition is of said relatively low order, as well as for then permitting the refrigerant to pass directly to the coil.

10. In a refrigeration system of the type which comprises means for passing refrigerant through the coil of a cooling unit, and means for effecting on-cycle and off-cycle operation of the system in accordance with the requirements of the cooling unit: a thermostatic expansion valve for controlling passage of said refrigerant, and comprising means responsive to the temperature at the outlet end of said coil for controlling the operation of the valve; means constituting a pipe connecting the outlet of said valve to the inlet of said coil; means for conducting refrigerant in thermal-transfer relation to said temperature responsive means, comprising a tube connected at both of its ends to said pipe; an additional valve for directing the passage of refrigerant entering said pipe from said thermostatic expansion valve;

the cooling unit: a thermostatic expansion valve 76 and means for opeating said additional valve in response to variations of the pressure condition in said coil, so that (1) the refigerant is directed'to said coil only by way of said tube when said pressure condition is of the high order existing toward the end of said oiI-cycle, as well as at the beginning of the on-cycle due to rapid expansion of the refrigerant, and (2) the refrigerant can pass directly through said pipe to the coil when said pressure condition is of relatively low order.

11. The combination defined in claim 10, and wherein said additional valve includes means for obstructing passage of refrigerant through said tube when said pressure condition is of said relatively low order, as well as for then permitting the refrigerant to pass directly to the coil.

12. In a refrigeration system of the type which comprises means for passing refrigerant through the coil of a cooling unit, and means for eil'ecting on-cycle and oil-cycle operation 0! the system in accordance with the requirements of the cooling unit: a thermostatic expansion valve for controlling e of said refrigerant. and comprising means responsive to the temperature at the outlet end of said coil for controlling the operation of the valve; means constituting a pipe connecting the outlet of said valve to the inlet of said coil; and means for conducting refrigerant in thermal-transfe relation to said temperature responsive means comprising a tube connected to said pipe, and an additional valve controlling passage of refrigerant through said tube and operated by the pressure of the refrigerant, said additional valve being biased to closed position and adapted to open with rise of pressure of the refrigerant in said pipe and coil. HAROLD J. MATTESON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,280,425 Sanders Apr 21, 1942 2,353,240 Huggins July 11, 1944

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