US2375319A

US2375319A - Control mechanism

Info

Publication number: US2375319A
Application number: US331683A
Authority: US
Inventors: Muffly Glenn
Original assignee: Individual
Current assignee: Individual
Priority date: 1940-04-26
Filing date: 1940-04-26
Publication date: 1945-05-08
Anticipated expiration: 1962-05-08

Description

May 8, 1945- G.V'MUFF| Y 'CONTROL MEcHANIsM Filed April 26, 1940 17 Zoff/g 2' y ATTO Ys Patented May 8, 1945 UNi'rED STATES PATENT" oFFicE 2,375,319 coN'raoL MEcHANIsM Glenn Many, springfield, ohio Application April 26, 1940, Serial No. 331,683

zo claims. (ci. szi) This invention relates to mechanical refrigeration and particularly to that type of system in which two or more evaporators are operated at diierent evaporating-pressures, as in a refrigerator which has a main food storage compartment maintained between temperature limits which are above the freezing point of water and another, separately insulated, compartment which is maintained between temperature limits which are below the freezing point of water.

Another of the objects of this invention is to provide a simpler and more effective means for controlling a refrigerating system of the multitemperature type. I'

Another object is toprovide a valve with a quick-acting, self-energizing effect for closing while fluid is flowing therethrough, but a static pressure eect for opening 'while the system is dle.

A further object is to utilize the bellows or diaphragm of a two temperature control valve for actuating a, switch.

and is responsive to a predetermined pressure for stopping such operation in either case.

Another object is to eliminatethe snap-action mechanism that has heretofore been employed 'in two temperature valves for controlling suc- 25. 1937, which has matured into Patent 'No.v 2,295,124; No. 237,629, filed October 29, 1938, and No. 324,466, led March 18, 1940, for disclosures of features related -to some of those of the present application. f Y

In the accompanying drawing which illus- `trates'suitable embodiments of'the present invention, and in which like numeralsreferA to like parts throughout the several different views,

Figure 1 shows the valve mechanisms in section, with diagrammatic representation of a, refrigerating system and cabinet.

Fig. 2 is a section on line 2 2l of Figure 1. Fig. 3 is an enlarged, fragmentary view taken from the left as viewed in Fig. l, showing the upper portion 0f' the high temperature evaporator, and part of the suction lines for both the evaporators', and illustrating the relation 'of the control bulb thereto.

Referring to AFigure l, it will be seen that the refrigerator cabinet I is provided with a door 2, f

enclosing the refrigerated space 5 and a separately insulated inner space the latter being closed by the insulated inner door l, having of the tank i0 containing the eutectic freezing solution ii. This solution is frozen by evaporator coil i2, which operates at a lower pressure than coil i5. The` coils i 2 and i5 are connected y in parallel, with vseparate suction -tubes Bt and tion lines in multi-temperature refrigerating,

systems.

y An additional object is to accomplish the `control of a two temperature .refrigerating system without the loss ofeiiciency due to the throttling of the higher pressure suction line and Awithout the loss that results from passing the vapor from the higher temperature evaporator through the lower 'temperature evaporator.

Still another object is to accomplish the above mentioned results without thenecessity of employing a compressor of the so-called multipleeffect type. y

Other objects will be apparent from the description which follows.

Reference is made to my issued U. S. Patents Nos. 2,145,773, 2,145,774, 2,145,775 and 2,145,777; to divisions of these patents still pending, and to my pending applications No. 144,698, filed May 46 to the valve assembly 63 of control assembly 62, from which the single suction tube leads to the inlet side of the motor-compressor lunit 2t. f

Compressed refrigerant vapor leaves the compressor through tube 2| and is condensed in condenser 22, from which liqueed refrigerant flows int-o receiver 23. A liq'uid tube 24 leads to the expansion valve 25, from which low pressure liquid ilows to whichever of evaporators i2 or I5 is active. 'I'he first pressure reduction on' the liquid occurs at valve 28 of the expansion valve and this liquid ows under reduced pressure through port 40 and tube 4| to the evaporator I 5,

from which suction tube 46 carries the vaporized refrigerant to the fitting 18 of valve $3.` The tting 18 is formed with` a valve seat 11, shown closed by valve 80. With the valve 80 in this position there is no flow through the tube 46 from the evaporator i5, 'but liquid refrigerant is free to flow upward from the expansion valve 25 after liftingv weighted check valve 49. Liquid passing this weighted check valve is thereby reduced in pressure by a fixed number of pounds per square inch as compared with the pressure existing in the chamber 38 of the expansion valve and at its outlet 48 to tube 4I, but since it must pass through the small diameter tube 58 it is not free to evaporate to any great extent before reaching the expansion coil I2. v

Evaporation in coil I2 is at a lower pressure and hence a lower temperature than in coil I5. The low temperature of coil I2 causes the freezing solution II to solidify and at the same time cools the compartment 6 to a lower temperature than compartment 5. For example, the compartment 5 may be heldat 40 degrees F. to 45 degrees F., while compartment 5 is cooled to 0 degrees F. to 10 degrees F. While the evaporator I2 is active the refrigerant vapor from it passes through tube 53, check valve 54, tube 56, tube 5'1 and tube 68 to the fitting |82 of valve .assembly 63,*where it lifts the check valve |86 and flows through passage 99 to tube 55, which leads back to the suction side of the compressorv of unit 28, thus completing its circuit.

After cooling the air in compartment 6 and freezing the bulk of the eutectic solution II, the evaporator coil I2 drops in temperature and along with it the tube 5'I falls in temperature. This cools the bulb 31 of expansion valve 25, reducing the vapor pressure in chamber 35, so that the valve 28 tends to close. Since this reduces the pressure in chamber 38 it also reduces the operating pressure of evaporator I`2 and the suction pressure in passage 99 of .the control valve assembly 53. Passage 98 is connected by means of port 89 with the interior of bellows 98, hence a reduction of evaporating temperature in the coil slightly, thus reducing the compression of'spring 86, but not yet lifting the valve 88 from its seat. Due to thelengthening of the spring 86 it will now be oiering less resistance to the lifting ofvalve 88, but in the other hand there will be a greater vapor pressure above valve 88 tending to hold it closed. The spring rate of spring'86, the area of the port of the valve 88, and the travel of. bellows 88 are so related that the reduction of downward push of spring 8B on valve 88 is substantially the same as the reduction of upward push resulting from the lower pressure diierence across the valve. Thus it is possible'to so design the valve assembly 63, to t a given vswitch assembly B5, that the valve 88 is lifted at substantially a given pressure in evaporator I5, regardless of the pressure in passage 98 and inside of the bellows.

The valve 88 may, however, be lifted by an increase of pressure within the evaporator coil I2 to a substantially predetermined point, regardless of the pressure condition in evaporator I5. This is true because the effective area of bellows 98 is many times that of valve 88. For instance, a

` pressure of 15 pounds within bellows 98 may ex- I2 is reflected as a lower pressure inside of bellows 98.

The head `88 of bellows 98 is urged downwardly by the push-rod H5 underinfluence of a spring (not shown) in the switch assembly 66, hence as the pressure within the bellows falls the head 88 approaches its lowermost point, where the shoulder 86 rests against the body 64, as seen in Figure 1. Before the rod H5 and bellows head 88 have reached this lowermost position, under the spring` urge applied lthroughvthe medium of rocker I-II, the switch -66 will have opened to stop operation of the unit 28. -The relationship of parts shown vin valve assembly 63 of Figure 1 is. therefore, as seen at the end of a running period of the unit 28.

During the., idle period the following changes occur in the order named, assuming that the space 5 requires further cooling before space 6. The rise of temperature in evaporator I5 causes an increase of pressure in tube 4E. lifting the valve 88 against the lower pressure above it and the l spring 86. It rwill be noted that this can occur while the1 bellows is still in the position shown; since the pin 82 in the upper stem of valve 88 is free to move a slight amount within the bayonet slots 84 which are formed in the part 88. A slight lifting of the valve v88 allows the higher pressure gas from tube 46 to enter the bellows by way of hole 88 and this pressure causes the bellows to expand enough to take up the clearance around pin 82 and lift the valve 88 still farther from its seat. V

The adjustment of switch 65 is such that it is closed by acertain pressure within bellows 98,

y and this pressure is preferably less than that atV .1() in excess pand -it to the point of making contact between the pin 82 and the bottom of the bayonet slots 84. This eliminates the spring from our calculations and the bellows head 88 begins to lift the valve 88 directly. The opening of valve 88 due to a pressure of 15 pounds in evaporator I2 allows the higher pressure from evaporator I5 to enterthe bellows. This pressure is always considerably of 15 pounds, even immediately after the unit 28 has stopped, hence the opening of valve 88 in response to a rise of freezer' temperature results in letting the higher pressure of evaporator I5 close the switch 65 and start the unit 28.

No matter which evaporator warmed up to its cutlin point first, the start will be on the warmer evaporator' I5, but in case the evaporator I5 does not require further cooling at the moment the valve assembly 63 will very soon cause the operation of the unit 28 to become effective on the evaporator I2, as follows:

A 'When the pressure within evaporator I5 has been pulledv down to the desired minimum (say 24 pounds, which is about 24 degrees F. with F- 12)` the bellows 98 will have collapsed under the push of rod H5 due to spring effect of switch 68 until valve 88 almost touches its seat 11. This produces a throttling eiect on the vapor flowing from tube 46 into the passage 89, with a resulting pressure drop in passage 99 and the interior of bellows 98. The pressure drop in the bellows causes it to collapse still further, allowing the valve 88 to more nearly close the outlet of tube 48. This makes the valve 88 self-actuating after a given degree of closing which is enough to start the throttling eiect.

After thegvalve 88 has been seated there will be vaporv begins to flow from the tube lim-lifting the which it is desired to restart cooling of the evaporator I5. hence as soon as valve 88 has been lifted from its seat 11 the bellows 88 is expanded beyond valve I86against the action of -the very light spring |88, The unit 28 is now operating on the freezer evaporator I2 at a suction pressure of about 15 or less,v pounds and will continue to do so until the resulting cooling of space 6 and freezing solution reduces the rate of vheat transfer to coil l2 and starts to frost the

extension tubes

53, 56 and 51. The cooling of tube 51 cools the bulbv 31, causing the expansion valve to reduce theinlet liquid pressure of coil I2 andconsequently the suction pressure in tube 60, passage 99 and bellows 90.

The bellows collapses further under this action until switch 66 cuts out, allowing the bellows head 88 to come to rest at the position shown in Figure l, with the shoulder 96 resting against the body 64|.

The switch 66 and the bellows 90 may be considered as a unit, forming an ordinary low-pressure control, such as has been used for many years in electric refrigeration, with a cut-in pressure of say 25 pounds and a cut-out pressure of 9 pounds. Although the switch would cut in under a rise of pressure to 25 pounds within the bellows, this can not occur until the valve 80 is opened. Valve 80 will open under any one of three conditions, namely;A the rise of freezer evaporator pressure to pounds, the rise of pressure in the warmer evaporator to 33 pounds (about 35 degrees F. with F-l2), or a combination of some rise of pressure in each evaporator. The opening of valve 80 results indirectly but immediately in closing the switch 66.

It should be borne in mind that the pressure conditions of opening valve 80 for starting are static, Whereas the pressure conditions of closing valve 80 'for the switch-over to the freezer are subject to the conditions of vapor flow. and the throttling elect before described. It is therefore entirely practicable to have the bellows expand to the cut-in position of switch 66 under a pressure-'of 25 pounds Vand yet collapse enough tostart the throttling eiect of valve v80 at 20 to 24 pounds and close valve 80 tightly before valve |06 is lifted by the l0 to 15 pounds pressure in tube 60. The exact point of starting the closing of'valve 80 under this throttling eiect may be adjusted by raising or lowering the seat 11 by changing the gasket 19 for a thinner one or a thicker one.

The valve 80 may be removed from. the valve assembly 63 after removal of the threaded part 10. For this purpose a tool provided with two or more prongs to engage the flutes 8| and a stop engaging the bottom end of the part 80 may be employed to lift the valve 80 and rotate it in a counterclockwise direction as, viewed from the bottom, so that the pin 82 is released from the bayonet slots 89, allowing the part 60 and .th spring 86 to be withdrawn. ,M

'The switch assembly 66 is not shownin detail, as it is assumed to be conventional in construction, including the necessary spring or springs.

arately from assembly 66 and-the two bolted to- .ffether by means of screws passing .through the bracket III, which supports them both. These screws may be threaded into or secured by means of nuts bearing against a pair of'e'ars 2 formed of moisture of condensation aroundthe bellows. 90. The working connection be'tweex the switch difference.

and the valve mechanism is provided by means of the push-rod ||5, the upper end of which bears against the screw H6, which is provided for adjustment of the valve parts.

The two suction tubes 46 and 60 are arranged in heat-transfer relationship with the liquid tube 24, as shown at the rear of cabinet in Figure 1 and by the sectional view, Figure 2. In a similar manner the bulb 31 of the expansion valve 25 lis clamped against the two tubes 43 and 51 so as to be responsive to the temperature of the colder one of these tubes, following the method disclosed in my issued U. S. Patent No. 2,145,777.

'Ihe rocker ||1 of switch 66 may be moved by hand byv use of the lever |20, which is attached thereto, thus allowing for manually starting or stopping the system and for shifting the operation from the freezer to the warmer evaporator or vice-versa. Y i l The electrical circuit is shown by wires numbered`68, 69, 12, 13, 14 and 15, including the relay switch. 1| which controls the starting circuit of the motor forming a part of unit 20. Wires 6,8 and I5 are connected to the line source of current. Wires 60 and 69 are connected v,by means of the switch 66, of which details are not shown, the circuitl being closed by an upward movement of arm |20 and opened by a downward movement ofit.

Y The bellows is soldered to its head 88 and to the body 60, the bellows cover 92 being for mechanical protection of the bellows.` Fittings 18 and |02 areV provided with gaskets 19 and IM, thus completing a gas-tight enclosure within-.the body 6d and bellows 90.

The tubular evaporator l5 lis provided with ns I6 for betterheat transfer to it from the air in space 5. These flns or additional brackets are employed to support the lcoil l5 in the position shown, adjacent to the lining of space 5. The tank.| 0 is suitably supported in space 6 andit in turn contains the coilvl 2 and the freezingsolution Il.

The expansion valve 25'is of novel construction in that it includes a pressure reducing valve t9, shown as a weighted check valve, and has two outlets. Also the bulb 31 is employed in a novel manner, causing the valve to be responsive irst to ya drop of temperatureof the tube 43 and then to a drop of temperature of the tube 51.

The weighted ralve ,69 is shown for the purpose of illustrating an expansion valve of the suredilerence across it.A The valve 49 might be of the diaphragmftype or merely a ,springclosed check valve having the desired relation-l ship between valve port area and springstrength to permit it to open under a desired pressure bining the two valves in a vsingle unit.

Arlotherfeatureis .the use of two diaphragms 32'` and 33, with'a dead air or' gas space between them. 'They act as one diaphragm, since the valve stem 29 is soldered to both of them, but the dead gas space serves as insulation between relationship between switch and Sucha valve-in any ofthese types is less expensive than a second expansion valvev would be,.a ndv I eect a further bsaving by com- I the cold liquid in chamber 30 and the warmer charge of volatile fluid in chamber 35. Both of the diaphragme `are sealed to the cap 3I, which is preferably made quite thin or of material with a low thermal conductivity such as stainless steel or a molded composition. The cap 3| issoldered or otherwise joined in a gas-tight manner to the body 21' of the .expansion valve. Stem 29 may be made in two parts for more ready removal of the valve 28 or to allow the valve a bit of free movement or "iioat so that it will seat more readily.

The check valve 54 is provided to prevent backflow of vapor into the evaporator I2 from the tube 51, which mightin some cases produce an undue cooling effect on the bulb 31, but in general the valve |06 serves the purpose of preventing back-flow into evaporator I2 from evaporator I5, hence the valve 54 may be dispensed with in most cases.

The switch 66, if a stock model, is provided with a stiffer spring urging the lever downward, in the closing direction, than would be used in the same switch when operated separately from the valve mechanism. Thus the rod I5 is always under compression. The switch spring must be strong enough to overcome the spring effect of the bellows and to compress the spring 86 of the valve mechanism. The bellows is made of suflicient diameter and any snap-over or toggle spring of the'switch mechanism suinciently weak to insure positive movement of the bellows head to substantially a given position for each pressure within the bellows, though these positions will be slightly different as between upward travel approaching the on position of the switch, and downward travel, approaching the off position of the switch.

While it is possible to design the spring 86 so that its spring rate matches the upward movement -of bellows head 88 to allow the valve 80 to be lifted by a given pressure in the tube 46 regardless of the pressure that exists in the passage 99 above the valve 80, it is preferred that the spring 86 have a slightly greater spring rate than this so that there is an over-compensation for the rise of pressure in the evaporator I2 and the passage S9.- This results in the valvel 86 lift- 'ing in response to a lesser pressure in the tube 46 when there is a' higher pressure in the evaporator l2. The effect is that the condensing unit starts in response to a lower pressure in the evaporator i5 when the evaporator I2 has more nearly approached its starting pressure and vice versa. This is desirable because when both evaporators are warming up rapidly it is advantageous `to hasten the starting of the condensing unit so that the evaporator I5 may be pulled down to close the valve 86 and start work on the evaporator I2 before the latter has had time to warm up too much.

Check valve 42 is located in the tube 4| for the purpose of retaining liquid refrigerant in the evaporator I5 during' idle periods. It is necessary that there be Vsome liquid in the evaporator I5 during idle periods of the motorrcompressor -unit 2l) so that the pressure in tube 46,will represent the/rising temperature of space 5 and evaporator I5. If this check valve were not employed the rising pressure in evaporator I5 would result in lifting the weighted check valve 49 and evaporating liquid from the evaporator I5 to condense in the evaporator I2, which would produce an undesirable heating of evaporator I2 and might re` duce the pressure in evaporator I5 by robbing it of liquid and thus fail to lift the valve 80 in response of a rise of temperature in the space I5. This check valve 42 is shown diagrammatically in Figure 1, but it is intended that it be made a part of the expansion valve assembly 25 as is the weighted check valve 49. The check valve 42 does noi-l require a weight or a spring.

An alternative method `of operation, which would result in each start of the motor compressor unit 20 being in response to a rise of temperature in space 5, is to provide for a slow leak at the valve 80. This may be produced by means of a nick in the. seat, 11 or by a very small groove 80' across the conical face of the valve 80. Using this slow leak it will be seen that vapor in the tube 46 will slowly leak through into the bellows 90 and cause it to expand until the valve 80 is lifted and thereafter the bellows 9|) will be directly responsive to a rise of pressure in the evaporator I5. When this slow leak method is employed the cut-in point of the switch 66 is set at a pressure representing the temperature of evaporator I5 at which it is desired to have the condensing unit start.

The above described method of starting the system does not provide for starting in response to a rise of temperature in the space 6 'and evaporator I2, but providing there is enough storage capacity in the tank I0 for freezing solution IIV it is possible to have enough hold-over eii'ect to insure satisfactory refrigeration of the space 6 during the longest idle period that Is possible under any ordinary temperature conditions.c If, however, it is desired to operate the refrigerator in a very cold room it is preferable to follow the method first described and provide for starting the motor compressor unit in response to a rise of temperature in either of the evaporators. This insures that the space 6 is held within temperature limits well below freezing even though the space 5 does not call for any refrigeration, as would be the case in a 40F room.

The unil; compartment 3 in the lower portion of cabinet I is preferably designed to contain the motor compressor unit 20 and optionally the condenser 22 and control assembly 62. The control assembly 62 may, if preferred, be located inside of the space 5 and the condenser 22 with its receiver 23 may be located on the rear wall of the cabinet.

The tubes 24, 46 and 60 are shown as running down the rear wall of the cabinet, but may be located within .the cabinet wall or inside of the space 5, either with or without separate insula- While theexpansion valve 25 is shown with a thermostatic bulb 31I contacting the uppermost tube 43 of evaporator I5 and tube 51, which is an extension of evaporator I2, it will be understood that the capillary-tube 36 of expansion valve 25 might itself be placed in contact with tubes 43 and 51. Another variation of design would be tov eliminate tube 36 and bulb 31 entirely, bringing the tubes 43 and 51 into thermal relationship with the chamber 35 of the expansion valve, which would accomplish the same result of making the expansion valve respond to the temperature of the colder one of these two tubes` In assembling the switch 66 to the valve mechanism 63 to form the control assembly 62 there will be a slight adjustment necesary to establish the correct relationship between these two units..

'I'his is provided for'by means of the screw IIS, which in eiect varies the length of the push-rod II5. The rod II is pointed at both ends and is a very free fit within the bore of screw IIB so as to allow for changes of angular position between the push rod and the rocker I Il as the latter moves upon its pivot I I8. It' is obvious that the spring 86 and springs or other parts of the switch 66 may be changed at will to`adapt the assembly for operation with other refrigerants or .at other temperature relationships.

After the valve 80 has closed and possibly while the compressor is still running on the freezer evaporator, the pressure in evaporator I5 will rise rather quickly to the temperature-pressure point (32 F.30 pounds) where defrosting occurs. Even with a short idle period we are therefore assured of a pressure at least 30 pounds in tube. by the time of the next start, assuming a defrosting cycle, which is desired, for evaporator I5. 1

Valve 80 preferably closes during the run at a suction pressure somewhere between 26 pounds and 20 pounds, hence there is a pressure difference of- 4 to 10 pounds available between the point of closing valve 80 and the setting at which switch 66 closes. It makes little difference just what this cut-in pressure is, because the start results from the opening of valve 80 in response to the warming up of one or both evaporators and whatever pressure there 'is in evaporator I5 then is ample to cause the switch to close.

As explained previously herein, the check valve 5t maybe eliminated, but it should be understood thatinstead of omitting the valve 54 it may be retained and the valve |66 omitted from assem- -bly 63, in which case valve 54 will serve the same purposeasvalve I06. s

For the purpose of unloading the motor-compressor unit 20 to reduce the motor load in starting, a further alternative may be employed as follows:

Expansion valve may be so charged with an amount of volatile fluid as to insure that there will be some liquid remaining in bulb 31 or chamber 35 during idle periods. This will cause the valve 28 to remain open during idle periods of unit 20 and drain the liquid refrigerant from receiver 23 into evaporator I2 or I5, or into both;` For such operation the evaporators will be designed to have a combined internal volume suiiicient to hold all of the liquid in the system, draining the condenser 22 and receiver 23 of liquid during idle periods. This reduces the discharge pressure against which the compressor is required to start, assuming that the total refrigerant charge in the system is established at a liquid volume which is less vthan. the combined internal volumes of evaporators I2 and I5, including any accumulator capacity that may .be added to one or both evaporators to allow for variations in liquid volume.

In case this unloading method is employed it will, beobvious that receiver 'Z3/accommodates the excess liquid refrigerant during running periods of the system and that during idle periods the evaporators I2 and l5 must have ample combined internal volume, including any liquid accumu-` lator capacity that may be added for this purpose,

- ting the groove 80', in case it' is desired to'make t to accommodate all of the liquid refrigerant in the system.

The .bulb si, or' that'portion of tube as ein-- cated in heat transfer relationship to the outlets of both evaporators, but it should be understood that this relationship may be more intimate with one suction tube than with the other, so that the desired degree of influence may be effective on the expansion valve 25 when either one of the evaporators is active. In general it will be the outlet of evaporator I5 which has the more intimate heat exchange relationship to the bulb 31 or tube 36, as the vapor leaving evaporator I5 will be at a higher temperature than that leaving evaporator I2, though tube 56 may be made ample to superheat theV gas from evaporator I2 to bring it up to the same temperature as gas leaving the evaporator vI5,in which case the heat exchange relationships maybe equal.

These heat transfer relationships are preferrably made adjustable, as disclosed in my issued U. S. Patent No. 2,145,777 in connection with bulb or bulbs.

The check valve t2 is intended to be made a part of the expansion valve 25 in a manner similar to the weighted check valve 49, though valve d2 is here shown separately for convenience in tracing the now of refrigerant.

The control assembly 62, to which this application is mainly directed, may -be used with other forms of refrigerant controls in place ofl the exl pansion valve 25, one alternative being the use of two conventional thermal expansion valves connected in parallel, one for each of the evaporators.

y While it is intended that the valve 80 have a substantially gas-tight tv with its seat 1l,- omitthe control respond to a rise of temperature in it will be obvious that an accidental leak at valve 86 can only result in earlier' starts which will cause shorter idle periods and correspondingly shorter running periods, as such a leak will not aect the cut-out point nor the pressure at which the valve closes to start operation of the colder evaporator. I'

The groove 80', if used, would preferrably be so small that the amount of vapor passing through it from the warmer evaporator I5 during operation of evaporator I2 would benegligible, thus a very minute portion of the cooling of evaporator I5 would .be at the lower efllciency of the colder evaporator I2. r

The adiustment of bulb 3l and its relationship with tubes 43 and 5l will be better understood by referenceto Fig. 3, which further illustrates an improvement over my previously disclosed method of making a control respond to temperature changes of two or more separate fluid ducts.

being in connection with the thermostatic expanl sion valve 25, but the adjusting means .seen in Fig. 3 would apply equally to a switch for control of a condensing unit, a heating device, a flow di` verting valve, etc.

In the refrigeration application here shown, it is se'en thatthe solid arrows of Fig. 3 indicate directions of now of refrigerant in the system the y v element.

seen in Fig. l. The bulb 31 is clamped against tubes 43 and 51, as shown in Fig. 1, and is adjustable along these two tubes to the position indicated by dotted lines. The bulb 31 may, therefore, have a 'full length contact with tube 43 and a shorter length of contact with tube 56 or vice versa. Also the bulb may be clamped in a midway position where it has full length con- This provides an adjustment whereby one expansion valve may serve two evaporators and operate as desired for each. The moving of bulb,

3'1 along the tubes has substantially the eiect of changing the weight of valve 49 or changing the size of its port, but the adjustment is made externally.

Considering Fig. 3 separately from Fig. 1 instead of as a detail of it, we may assume thatl it still shows a part of a refrigerating system, but the tubes 43 and 51 are arranged in counterflow relationship, as indicated by the dotted arrows. These tubes are still considered to be suction tubes leading from two separateevaporators.

It is now seen that an adjustment of bulb 31 longitudinally of the two tubes even within that Alength where the bulb has full length contact with both tubes will effect va change in adjust-A ment of the relative relationships of bulb 31 to the two evaporators served by suction tubes 43 and 1. It is a well known practice to adjust the bulb of an expansion valve or a thermostatic switch along a length of evaporator or' suction tube to vary the temperature of operation Aor length of running period of a system. The novelty of Fig. 3, used as last above described, is that it combines with my earlier disclosure of means for making a control device responsive to two separate uid ducts the improvement of means for balancing such adjustments externally of the refrigerant .ducts by movement of a single It is understood that the bulb 31 need not be an actual bulb and may be-merely an extension tube 36.

It will, of course, be obviousI and I wish to emphasize the fact that this application-is not limited'to the vexact 'structures and methods of control and operation-described herein, but vis in ended to serve as a disclosure of a representativ few of the many ways in which my invention m used.

Formal changes Vmay be made in the specinc embodiment of the invention described. without departing from the spirit or substance orA the broad invention, the scope of which is commensurate with the appended claims.

What is claimed is:

1. A valve for controlling fiuid refrigerant, means responsive to an increase of iluid pressure on the down-stream side of said valve for opening it, spring means acting in the direction of -closingsaid valve, and leakage means for allowing gradual flow past said valve when it is closed, said vleakage means being eEective in raising the pressure on the down-stream side of the valve and thus reducing the loading of said 'spring means. i

2. A refrigerating system including two evaporating units, a refrigerant condensing means and a control mechanism comprising a unitary control device that includes a control for said condensing means and a casing connected to the two evaporating units, said device being constructed and arranged to so regulate iiow of refrigerant vapor from said evaporating units that one vof the latter operates at a lower lo'w temperature limit than the other.

3. Avalve mechanism for controlling the now of a refrigerant in a refrigerating system, a plurality of heat absorbing devices and a heat dissipating device forming parts of said system, said mechanism including means responsive to a rise of temperature to a substantially predetermined limit in one of said heat absorbing devices for its actuation, said mechanism being also responsive to a rise of temperature to a higher predetermined limit in another of said heat absorbing devices, and means for starting operation of said heat dissipating device in response to either actuation of said mechanism.

4. Refrigerating mechanism comprising, in combination, a low ,pressure evaporator, a high pressure evaporator, means for connecting the outlets of said evaporators with a refrigerant condensing unit and including a pair of suction ports each connected to one of said outlets, an expansion device including a casing forming a low pressure chamber, said chamber having two outlets, one of said outlets of said chamber leading to said low pressure evaporator and the other to said high pressure evaporator, a pressure reducing device in said casing arranged to control the outlet from said chamber to said low pressure evaporator, and check valve means so constructed and arranged as to prevent refrigerant flow from said high pressure evaporator to said `low pressure evaporator.

5. In a refrigerating system, a pair of evapo' rators, suction tubes for said evaporators running substantially parallel to each other for a `portion of their lengths, a control device, and a temperature-affected member of said device arl ranged to contact both of said suction tubes'at ports each connected vto oneof said outlets, an

expansion device including a casing forming a low pressure chamber, said chamber having two out-lets, one, of said outlets of said chamber leading to said low pressure evaporator and the other to said high pressure evaporator, a pressure reducing device in said casing arranged to control the outlet from said chamber to said 'low pressure evaporator, check valve means so constructed an'd arranged as to prevent refrigerant flow from `Said high pressure evaporator to said low pressure evaporator, and means responsive to the temperature of tre refrigerant discharged from both of said evaporators for controlling the -elIect of said expansion device.

7. A refrigerating system including a condensing unit, a low pressure evaporator and a high pressure evaporator forming parts of said system, means for connecting the outlets of said evaporators with said condensing unit and including a pair of suction ports each connected to one of said outlets, a pressure reducing device including a casing forming an intermediate pressure chamber, said chamber having two outlets, one of said outlets leading to said low pressure evaporator and the other to said high pressure evaporator, a second pressure reducing device arranged to control the outlet from said chamber to said low pressurel evaporator, valve means so constructed and arranged as to prevent refrigerant flow from said high pressure evaporator to said low pressureevaporator, means responsive to the temperature of the refrigerant discharged from either of said evaporators for controlling the effect of said expansion device including a thermally affected member arranged in heat conducting relationship wi'th respect to the suction passages of both of said evaporators, and means for adjustably holding said member in heat coinducting relationship -with said suction passages.

8. A refrigerating system including an evaporator, a valve in said system downstream from said evaporator, a housing including a port controlled by said valve and passages connecting wth said port on opposite sides thereof, and

yieldable means acting in a direction tending to hold said valve closed, said valve being so constructed and arranged that uid pressure on one side of said port tends to hold it closed and uid pressure on the oppositeside tends to open it,

said `yieldable means being variably stressed prior to valve opening by changes of one of said pressures. l

9. A refrigerating system having .-a plurality of evaporators adapted to operate at diierent refrigerant pressures to cool separate chambers of a refrigerator to dilerent temperatures, a valve constituting a par-t of said control device, each of' said conduits including a section which' is substantially parallel with a corresponding section of the other of said conduits, the parallel section of each of said conduits being transversely aligned over a portion of fthe length of each t ereof, and said parallel section of each of said cgdirtsnp/rzojecting beyond an end of the parallel sect1 he other thereof, and means for adjustably holding said element in preselected relative heat transfer relationships with said parallel sections of said conduits so as to optionally provide equal heat transfer relationships between said element and said conduits, better heat transfer relationship with one of said conduits, or better heat transfer relationship with the other of said conduits.

11. A refrigerating system, a, valve for control of refrigerant flow, in said system, means urging said VVvalve toward its closed position, and means for opening said valve, said valve being also so constructed and arranged as to be operable in response to a' rise of uid pressure on its upstream side, said opening means being responsive to a rise of pressure on'the downstream side of'said valve to reduce the effect of said urging means, said opening means and said urging means being so constructed and arranged as to more than compensate for the-effect of downstream pressure rise tending to oppose the opening of said valve. f

12. Inv a refrigerating system, a suction conduit for refrigerant fluid, means interposed in said conduit and provided with a port therein, a valve arranged to close said port, and means for opening or, closing said valve in response to pressure changes in said system, said means being responsive to pressure changes on both the upstream and downstream sides of said valve but to lesser pressure changes on the downstream than on the upstream side, and being substantially independent of all iiuid pressure changes except those of said refrigerant iiuid.

13. A refrigerating system having a pair of evaporators operable at dierent pressures, a cabinet having separate zones cooled to different temperatures, one of said zones beingrcooled by .each of said evaporators, suction conduits leading from said evaporators, means interposed in one of said conduits and including a port therein, a valve -in said system arranged to open or close said port tojeect cyclic operation of said evaporators, and means in said system for opening and closing said valve in response solely to pressure changes inisaid conduits, the last said means being responsive to lesser pressure changes in one of said conduits than in the other.

14. In arefrigerating system having a suction conduit, means interposed in said conduit and providing a port therein, a valve arranged to close said port, and means for opening or closing said valve in response to pressure changes in said system, the last-mentioned means having a lost motion connection with said valve and being arranged to open the same in response to a pressure rise either upstream or downstream of said port, the last-mentioned means being arranged to initiate the opening of the valve in response to a. smaller increase in pressure downstream of the port than is needed upstream of the port to open the valve. y

15. In a refrigerating system having a suction conduit, means interposed in Ysaid conduit and providing a. port therein, a valve arranged to close said port, and means for opening or closing said valve in response to pressure changes .in the system, the last-mentioned means fbeing. ar-

ranged to open the valve in response to a pressur rise either upstream or downstream of said port and-being arranged to initiate `the opening of the valve in response to a smaller increase in pressure downstream of the port than is needed upstream of the port' to initiate opening of the valve, said last-named means including an expansible chamber element connected to the valve and substantially independent of all pressure changes except those downstream of the said port and in said conduit. l y

16. A refrigerating system including a conduit for the circulation of a volatile refrigerant iiuid,

an increase of pressure on the outlet side of said valve port for reducing the stressing of said spring means whereby to reduce the pressure dif# ference required to open said valve port.

17. A refrigerating system, a conduit for volatile refrigerant in said system, a valve port connecting sections of said conduit, a valve adapted to close said port and to be opened by a rise of iluid pressure on its upstream side, means forA closing said valve, and means urging said valve in the direction of opening m response to a rise of pressure on the downstream side of said valve, the whole being so constructed and ar. ranged that the valve will at times open in response to a lower fluid pressure diierence between its two sides than that under which it is normally held closed.

18. A refrigerating system,A a conduit for volatile refrigerant in said system, a valve port connecting sections of said conduit, a valve adapted to close said port and to be' opened by a rise of fluid pressure on its upstream side, means for closing'said valve, and means urging said valve in the direction of opening in response to a rise of pressure on the downstream side of said valve, the whole being so constructed and arranged that the valve will open in response to a relatively low lfluid pressure diilerence when there is a relatively high fluid pressure on the downstream side of said valve and to .a relatively high fluid pressure difference when there is a relatively low fluid pressure on the downstream side of said valve.

l said valve port, and means acting in response to 19. A refrigerating system, and a control mechanism therefor, said system including a high temperature evaporator and a low temperature evaporator, said mechanism including means for starting refrigeration upon attainment of a predetermined high pressure in the high temperature evaporator or a lower predetermined high pressure in the low temperature evaporator each independently of the other evaporator. said means being also responsive to the combined effects of the pressure of said evaporators when both are approaching their high temperature limits to initiate refrigeration in response to the combined eiects of the partial warming up of each of the said evaporators before either has reached its predetermined high pressure.

20. A refrigerating system, a plurality of evaporators connected in said system and operating within different ranges Vof pressure, said system having a. porttherein operatively connected with one 'of said evaporators, a valve controlling said port, and pressure responsive means for moving said valve to open said port,

said means operating solely in response to pressures of the refrigerant in said system to move said valve to open said port at one time in response to a pressure rise in one of said evaporators which operates under a relatively low pressure and at another time in response to a pressure rise in another of said evaporatorsv which operates under a relatively high pressure.

GLENN MUFFLY.