US2291898A - Expansion valve - Google Patents

Description

EXPAN S ION VALVE Filed May 5, 1959 3 Sheets-Sheet 1 7 illi igail liififlumndl Ila Manllmesi (Ittomeg Patented Aug. 4, 1942 UNITED STATES 2,291,898 nxransren 'vALvE Gifford I1 Holmes, Minneapolis, assignor i to Minneapolis-Honeywell Regulator Company, 7 j/ l AT-ENT orrlct Minneapolis, Minn., a corporation of fieiaware Application May 5, 1939, Serial No. 271,983

18 Claims. (Cl. 62-8) This invention relates to expansion valves and more particularly to that type of valve known as-thermostatic expansion valves such as are commonly employed in refrigerating systems.

One of the objects of this invention is the provision of an improved thermostatic expansion valve of the type which controls the flow of refrigerant through the evaporator in a manner to'inaintain the refrigerant at the outlet of the evaporatoLwlmiantiallyconsta .t degree of superheat.

More specifically it is an object of this invention to provide a thermostatic expansion valve and operating means therefor whereby the valve will control the refrigerant through the evaporator in such a manner that, regardless of variations in temperature and pressure, the refrigerant at the evaporator outlet will be maintained at a' substantially constant degree of superheat, with means for adjusting the superheat setting of the valve without affecting the ability of the valve to maintain the refrigerant at a substantially constant degree of superheat as the temperature and pressure of the refrigerant vary, at the new superheat setting of the valve.

fication, claims and appended drawings wherein like reference characters represent like parts in the various views and wherein,

Figure 1 is a view of one form of expansion valve and operating mechanism therefor shown in a conventional refrigeration system,- with certain parts shown in cross section,

Figure 2 is a modification of the valve and operating mechanism therefor in Figure 1 shown in cross section,-

Figure 3 is a crosssectional view of a still further modification of the valve and operating mechanism of Figure 1, and

Figures 4 and 5 are views illustrating the temperature pressure curves of two well known refrigerants.

In the past, expansion valves for controlling the 55 flow of refrigerant through an evaporator comprised an operating bellows or diaphragm which responded to the temperature of the refrigerant within theevaporatorfor controlling'the position 5 of thevalve, the operatingbellows or diaphragm opening the valve upon an increase in'temperature or upon a decrease in pressure. The bellows or diaphragm also responded to the pressure on the suct ign sidepf the system, the pressure being taken at the inlet oftheevaporator but the valve did not properly respond to msuperheat of the refrigerant at the evaporator outlet because of the pressure drop existing within the evaporator, particularly on systems using a relatively large or multiple coil type of evaporator, the pressure drop being variable depending upon the load on the evaporator, so in order to make the valve properly respond to the superheat at the evaporator outlet a connection known as an equalizer connection was provided between the outlet of the evaporator and the operating bellows or diaphragm so that the bellows or diaphragm properly responded to the pressure at the evaporator outlet. This arrangement while satisfactorily 'controlling the valve according to the superheat at the'evaporator outlet, did not act to maintain the superheat at a fixed value as the temperature and pressure of the refrigerant leaving the evaporator varied, so that the efiective cooling area of the evaporator, or that portion thereof which was in a flooded condition would varyflastlre' temperature and pressure of the refrigerant leaving the evaporator varied.

Upon reference to Figure 4 it will be seen why such valves would not properly maintain the superheat of the refrigerant leaving the evaporator at a constantvalue. ,Curve A shows the pressure temperature curve for the refrigerant Freon or F-12. It will benoted that this curve 40 is not a straight line. Curves for all known rerange is about 3 lbs. per square inch. On the other hand, as the temperature of the refrigerant increases from 20 F. to 30 F. the pressure corresponding to this temperature increases from approximately 36 lbs. to 44 lbs. per square inch; or in other words, for this 10 rise in temperature the pressure increases by approximately 8 lbs. In the conventional thermostatic expansion valve a spring is employed which opposes the action of the power or operating bellows or diaphragm; or in other words, tends to close the valve agaih'st thep ning force exerted thereon due to a rise in armature. These springs generally exert a substantiamonstant force upon the valve and may be adjusted maintain a certain degree of superheat of the 1 refrigerant at a given value of temperature, for example: Assume that it is desired to maintain a superheat of the 55mm W .orator outlet when the suction pressure 1535' lbs. The temperature of the saturated refrigerant corresponding to this pressure will be approximately 18 F. as will be noted from curve A of Figure 4. If the refrigerant is to be maintained at a 10 superheat the temperature of the refrigerant should be 28 and the pressure corresponding to this Emperature wiilbe approximatelMii-lbsfifi'ccordingly the spring which.

3 o! Figure 5. In va ves ei3 ploying operating bellows or diaphragms.havingdiiferentsizedareas asshown in the Newton application hereinbe- 1 fore identified, if the force exerfiddiy the spring is increased, the superheat line in Figur e5\ wouldbe above the line D of Figure 4 but since the spring rate would be the same as before the superheat line would be parallel with the line D of Figure 5 and if this line were transposed onto Figure 4 it would illustrate that the valve, would notmaintain the superheat at a constant "value for varying pressures and temperatures. equal to the difference of the 35 lbs. suction prese a ou t t a t e superheat would y from sure and the 43 lbs. pressure which corresponds the s d v ue would in e as t e Sp to the pressure of the saturated'refrigerantsatihew was adjusted from the proper settin o whlai higher temperaturef'of in other words, a force modelled. H wev r 1 the n l uequaktvSlbs. As the temperature gradually loading of e Spring and e pr ng ate are decreases at the outlet of the evaporator the h p perly Va ied he valve will maintain the superheat will gradually increase as explained superheat v ,if superheatis d r alon below. Assume that the pressurev at the outlet the line F. This is one of the features of the of the evaporator drops to 20 lbs., the temperapresent invention. Thus, increasing h sp i ture of the saturated refrigerant at this pressure loading ld move the line Figure upwill be approximately -7 F. and if the spring d y pa a w t se a d increasing the continues to exert an 8 lb. closing force the pres- Spring rate ou d c e he inclination of the sure corresponding to the temperature of the line, so that by properly s e' e Spring e refrigerant 111 be approximately 2 and for 20 superheat, the inclination and position the temperature of saturated refrigerant correwould be changed to t of ne F. The remainsponding to 28 lbs. pressure is approximately 8 ing full n curves of Figure 4 illustrate the opposes the opening of the valve exerts a force F. Thus the superheat of the refrigerant leaving the evaporator at this lower pressure will so that while the evaporator is operetih'g et'a" lower temperature, the effective cooling surface thereof has decreased.

The curve B shows the constant 10 superheat r curve and the vertical distance W between the curves A and B shows the actual closing force that should be exerted on the valve at varying temperatures and pressures in order that the superand superheat curves, which curves also appear as straight lines in Figure 5, but these lines have increasing inclinations as the amount of superheat increases. Similar curves for the refrigerant ammonia are illustrated by dotted lines,

the saturated ammonia curve of Figure 4 coincidin'g with the line C of Figure 5. In this figheat existing at the outlet of the evaporator will K together in conventional ma er. The valve [3 at-all times be constant. This curve Bit willbe i 209F the flow of e ant through the evapnoted has a curvature somewhat similar to the islalv is Shown to mpr e a curve A but gradually diverging therefrom as the Casing comp se of a lower'sect on 20 and en temperature increases and if. the ourveAbetaken upper t on he section 20 includes an as the base line,'as shown by the line C of Figet p g 2 through which high P essur ure 5, and the curve B plotted from this line; as C f i eran flowsand the outlet openin II conshown by the line D of Figure 5, it will be seen trolled by the valve element 24. This valve elethat the line D is also a straight line. In order" ment may be Su ly Supported within the for the valve to operate along the line D of Figs s ti n 20 and is shown to be connected to ure 5 which is the constant 10 superheat line, one end of a lever 25 pivoted at 25 d having the areas of the bellows or diaphragm which the opposite end engaged by the compression responds to the temperature of the refrigerant Sp 21 w ich acts to as t e valve towards may be made slightly smaller than the area of closed position. The position of the lever 25 is the bellows or diaphragm responding to the prest olled by t e pl er 30 Suitably o ected sure, as disclosed in the application Serial No. to the bellows 3| mounted in the upper casing 192,818 filed by A. B. Newton on February 26. section 2|. Apartition 32 separates the two por- 1938. By choosing the proper relative sizes of tions of the casing and this partition has an the bellows or diaphragms responding to presopening 33 through which the plunger 30 ex sure and temperature and by choosing the proptends. there being a suitable sealing bellows 34 or spring to bias the valve towards closed posifor preventing escape of refrigerant into the upper portion 2| of the casing. A spring 35 opposes the expansion of the. bellows 3| and tends to permit closing of the valve under the influence of the spring 21. r

The bellows 3| is in communication by means of the capillary tube 38 with a bulb 39 located within the evaporator outlet, this bulb 39having an expansible portion in the form of a bellows 40 for a purpose to be described; The portion of the evaporator within which the bulb 39 is mounted has an enlarged portion 4| which forms a chamber for the diaphragm 42 which may be suitably clamped between the enlarged portion 4| and the cover member 43 by means of the bolts 44. The diaphragm 42 is sealed to the lower portion of the bellows 49' and this diaphragm is normally biased upwardly by means. of the compression spring 45 held betweeri'the spring retainer 46 fastenedto the lower portion of the diaphragm and the recessed adjusting screw 50 which is adjustably received by the cover member 43. g a r As the pressure of the refrigerant-leaving the evaporator increases, the diaphragm 42 will be forced downwardly against the force of the spring 45 and this movement of the diaphragm will cause an expansion of the bellows 40 forming the lower end of the bulb 39 which will have the effect of increasing the volume of this bulb. The bulb 39, tube 38, and bellows 3| may be provided with a suitable liquid fill which will have a substantially constant volume as long as the temting of the spring'45, that is,-a given loading and spring rate, the valve 24 will move in a manner to maintain a constant superheat at the outlet thereof. Thus with the parts adjusted as shown in'the drawings it"may be assumed that the valve is adjusted to maintain. a superheat of using the refrigerant F-12 so that the valve will'control the refrigerant. according to the curve B of Figure 4 or curve D of Figure 5.

The adjusting screw 50 is for the'purpose of adjusting the initial loading of thespring' and this screw may be providedwith a suitable pointer 54 which maycooperate with suitable indicia away from the diaphragm 42 without changing the force .of the spring 45 but by increasing or on the cover 43. d V screw 50 is an adjustingscrew 55 having suitable stop rnernbers 56 which serve. as abutment members for those coils of the spring which are located between the members and the diaphragm 42. By reason of the adjustment of the screw 55, the abutment members 55 move towards or ingly if it is desired to increase the superheat setting of the valve from 10? to 20, for example,

perature at the bulb 39 remains constant, so I that as the volume of the bulb 39 increases, the bellows 3| will collapse by an amount corresponding to the increase in volume of the bulb. This action of the bellows 3| will permit the valve 24 to move towards closed position under the influence of the spring 21, thereby reducing the flow of refrigerant into the evaporator and causing a reduction in pressure therein. On the other hand, if the pressure of the refrigerant should decrease at the evaporator outlet, diaphragm 42 will move upwardly, collapsing bellows 40 which reduces the volume of bulb 39, and bellows 3| will expand a corresponding amount, thus causing an opening movement of valve 24, which increases the flow of refrigerant into the evaporator. It will thus be seen that the fill in the bulb, tube, and bellows acts as a hydraulic transmission means to transmit movements of the diaphragm 42 into movements of the bellows 3|.

If now the temperature of the refrigerant leaving the evaporator should increase, there will be an expansion of the liquid fill in the bulb 39 which will cause an expansion of the bellows 3| and an opening. movement of the expansion valve. Conversely, upon a decrease in temperature of the refrigerant leaving the evaporator, the volume of the liquid within the bulb 39 decreases, whereupon the bellows 3| will collapse in accordance with this decrease in volume, and the valve 24 will move towards closed position under the influence of spring '21, thus reducing the flow of refrigerant to the evaporator. It should be noted that the area of the diaphragm 42 which responds to the pressure of the refrigerant leaving the evaporator is considerably larger than the area of the bellows 3.l which responds directly to the temperature of the refrigerant and also moves in accordance with the change in pressure by reason of the expansion or contraction of the bellows 40 and these relafive areas will be so chosen that for a given setthe adjusting screw 50 will be turned until the indicator 54 has moved to the proper. position wherein the loading of the spring 45 has been increased the proper amount. The adjusting screw 55 will also be adjusted until the indi-' cator has moved to the position corresponding to the adjustment of the member 50 whereupon the spring rate has been increased the proper amount and the valve is now properly adjusted to maintain the refrigerant leaving the evaporator at a constant degree of superheat, namely, 20 F. regardless of normal fluctuations in temperature and pressure. By adjusting the spring rate of the spring, the line D was tilted upwardly until it was parallel-with the line F.

and the change in the spring loading moved the line upwardly until it coincided with the line P, which line corresponds to the 20 constant'suprheat line E of Figure 4.

In the conventional type of expansion valve, employing a diaphragm responding to the superheat at the evaporator outlet, directly connected to the valve element, and having a spring opposing movement of the diaphragm in valve opening direction, the valve element will assume a predetermined position for each position of the diaphragm. In such an arrangement, if the spring rate of the spring were adjusted, the only effect upon the operation of the valve would be to change the operating differential thereof. A change in the loading of the spring would change the amount of superheat that would be maintained for a given pressure of the refrigerant at the evaporator outlet, since, again referring to Figure 5, the line D would be moved upwardly but since the line could not be made to coincide with the line F, the valve would not maintain the superheat constant for varying temperatures and pressures at the evaporator outlet.

In my arrangement, the diaphragm move in response to variations in pressurefof the refrigerant leavingthe evaporator outlet, but variations in temperature of the refrigerant at the Threadedly received by the position of. the diaphragm and the valve position by reason of the nature of the connections between the diaphragm and the valve element, and

this: isnan important feature of this invention which 'cofiti'ibutesto the new result which is obtained thereby. FOr' any position of the diaphragm, the valve position willdepend upon the temperatureofthe refrigerant leaving the evaporator. The positioii'of"the'diaphragm depends upon the-pressure of the refrigerantleavin the evaporator. diaphragm for any refrigerant pressure depends upon the spring loading and the spring rate which, if properly adjusted, will cause the valve to maintain any desired degree of superheat, and maintain the superheat substantially constant for varying outlet pressures and temperatures.

With this form of valve therefore it will be apparent that it may be set for different degrees of superheat by adjusting the loading and spring rate of the spring 45, and will maintain the superheat constant for varying degrees of pressure and temperature. By placing the diaphragm 42 at the valve outlet the necessity of using the usual equalizer connection is obviated and th only connection between the valve and the evaporator outlet which is required is the tube 38.. This arrangement is made possible since the pressure responsive diaphragm 42 does not act downwardly upon the valve but acts merely to adjust the volume of the bulb 99 which in turn varies the expansion of th operating bellows 3|. It should be understood that any suitable control means for the refrigerating apparatus may be provided. Referring to Figure 2, the valve and operating mechanism herein illustrated are formed as a unitary structure as distinguished from the apparatus shown in Figure 1 in which the bulb and pressure responsive diaphragm are formed as a unit separate from the expansion valve itself. In, this form of the invention the valve is shown to be made of a plurality of sections 10, H, 12, and 13. The section includes the inlet opening H and the outlet opening 15, the valve element 16 carried by the lever 11 and pivoted at "cooperating with the opening I5, the valve being biased towards closed position by means of the spring 19. Clamped between the sections II and 12 is a diaphragm 89, the sections II and 12 being suitably recessed asillustrated to permit movement of the diaphragm with respect to these sections and to form a pressure chamber Furthermore, the position of t e15 above the diaphragm. Connected to the dia- I phragm is the plunger 8| extending through the opening 82 in the section II, this plunger acting on the lever 11 so that as the diaphragm 80 moves downwardly the movement thereof is transmitted by the plunger 8| to the lever 11 to move'the valve element towards open position. The space within the section III is sealed from the diaphragm by means of the bellows 83 connected to the plunger 8|. The upper portion of the diaphragm communicates by means of the passageway 84 with the capillary tube 85 connected to a bulb 86 whichis subjected to the temperature of the refrigerant in the outlet of/ the evaporator, this bulb and tube being provided with a suitable fill which may be a volatile or liquid fill so'that as the temperatur or the refrigerant leaving the evaporator increases, ari

diaphragm 90, the under portion of which ,has'

connected thereto a bellows 9| sealed to the section 12, as illustrated. The space between the diaphragm 90 and the section 12 formed by recessing the upper portion of this section is placed in communication with the outlet of the evaporator by means of the port 94 and the tube 95. The tubes 85 and 95 may be concentrically arranged as illustratedso that the bulb 86 may be mounted within the evaporator outlet to more accurately respond to the temperature of the refrigerant leaving the evaporator as disclosed in the above"rrientioned Newton application. 'I'hediaphragms 80 and 99 are suitably connected together by a tension spring 96 so that if th diaphragm 9,9 is moved upwardly by reason of an increasein pressur at the evaporator outletthe tension of the spring 96 will be increased and will cause the diaphragm 80 to move in the same direction thuspermitting movement of the valve 11 towards closed position. The upward movement of the diaphragm 90 is opposed by means of a compression spring I00 with which cooperates adjusting screws l0! and I02 for adjusting the loading and spring rate of the spring as illustrated in Figure 1.

It will be noted that the area of the diaphragm 90 is larger than that of the diaphragm 80 which moves directly in accordance with the temperature of the refrigerant leaving the evaporator and while thebellows 9| reduces the effective area of the diaphragm 90 it reduces by the same amount the effective area of the diaphragm 80 and the areas of the two diaphragms will be so chosen that with the proper adjustments of the spring I00 the superheat of the refrigerant leaving the evaporator will be maintained at the desired value. The diaphragm 90, it should be noted, doesnot directly control the position of the valve 11. but when used with a volatile fill in the bulb 88, acts merely to adjust the tension of the spring 96 which exerts a closing force on the valve so that when the pressure of the refrigerant increases, the tension of this spring is increased and thediaphragm 80 will move upwardly thus in-, creasing the'closing force exerted on the valve by the spring 19. Similarly upon a decrease in pressure the downward movement of the diaphragm will reduce the force exerted by the spring 96 and the diaphragm 80 will move downwardly so that a smaller force must be exerted on the diaphragm 80 to open the valve. However, when a liquid fill is used in the bulb 86 and the chamber above the diaphragm 80, the spring 96 can be omitted without substantially affecting the proper operation of the valve 16 because a liquid will tend to remain at a constant volume without the assistance of a spring.

Refrigerant enters the opening Il3 in the upper I 4 section of the valve casing and passes through the opening I I2 and outwardly from the valve by wayof the opening Ill which is controlled by the valve element 16. The lower end of the bellows H is connected to a plate member II6 which moves with the bellows and which receives the compression spring I" having the adjustable abutment H8 threadedly received within the closure member I20 in the lower wall of the valve casing. The bellows III! is sealed to the lower wall of the casing by means of the sealing bellows I2I. Carried by the periphery of the plate member H6 are pins I22, only one of whichis illustrated, which bear against the free arms of the lever 11 which may be in the form of a yoke, and downward movement of the plate member by reason of an increase in pressure within the bellows III! will cause an upward or opening movement of the valve element 16 against the force of the closing spring 19.

Sealed to the upper wall of the partition I II is a bellows I25 having its upper end connected to the plate member I26 which is in turn sealed by means of the bellows I21 to the closure member I28. The interior of this bellows is in pressure responsive communication with the outlet of the evaporator by means'of the pipe 95 and-the passageway 94. The plate members H6 and I26 connected to the bellows H0 and I25, respectively, are connected 'to a tensionspring I35 which tends to maintain the bellows H0 and I25 in a collapsed condition. This spring passes through the opening H6 in the center of the partition III and a sealing bellows I31 seals the interior of the bellows I25 from this opening so that the bellows H0 and I25 are properly sealed from one another. a p

The plate member I26 is biased downwardly by means of the spring I06 having adjusting means IGI and I62 similar to that shown in Figure 2. The bellows I Ill and I25 will be kept in a warm condition at all times since they are surrounded by high pressure refrigerant entering the inlet H3 as is apparent from the drawings. The seal-off bellows I2! and I21 prevent the pressure of the high pressure refrigerant from efiecting' the operation of bellows H0 and I25, respectively. I The operation of this .valve is substantially the same as that of Figure 2 since an increase in pressure will cause expansion of the bellows I25 desired values of superheat of the refrigerant at the evaporator outlet will be maintained constant load conditions.

low that the force of the spring 19 in Figure 2 or the springs 19 and II I in Figure 3 is not overcome the valves will remain in closed positions. A certain amount of force is of course required to overcome springs 19 and Ill and the evaporator temperature may drop so low that the required force on diaphragm 80 or bellows I'IO may not be developed and the valves will remain closed.

7 This will normally happen only when the load thereon becomes very light. When this happens however the temperature of the refrigerant leaving the evaporator may drop below a certain value whereupon the valves will close entirely and will not open again until this temperature has risen above this value. Before this happens however the pressure within the evaporator will continue to drop so that the superheat at this time at the outlet of the evaporator will increase and the evaporator coil will gradually become more and more starved. The ratio of latent cooling to sensible cooling will thus increase by reason of the diminishing eflective coil area and the simultaneous reduction in pressure in the evaporator which is very desirable under light The spring II! in Figure 3 is made adjustable so that the temperature at which the-valve is closed regardless of the pressure may be adjusted according to the requirements of the system. It should of course be understood that the spring 19 of Figure 2 may, if desired, also be made adjustable for the same purpose.

It will accordingly be seen that .the valves of Figures 2 and 3, besides operating to maintain constant any desired degree of superheat over a normal operating range, also operate to prevent 'the flow of refrigerant to the evaporator whenever the temperature of the refrigerant at the outlet'thereof drops below a predetermined value. This is made possible by reason of the novel arrangement of the operating bellows or diaphragms, the one responding to the pressure of the refrigerant not being directly connected to the valve but merely acting upon a tension pressure.

regardless of normal fluctuations in temperature and pressure.

In both Figures 2 and 3, if the temperature of the refrigerant at the evaporator outlet' should become sufiiciently low, the diaphragm 80 or bellows III) will not exert sufiicient force to open the valve against the closing force exerted by the spring 19 in Figure 2, or the springs 1.9 and III in Figure 3, regardless of how low the pressure becomes. In other words, these springs 96 and I35 connecting the operating bellows or diaphragms may exert no force whateverbecause the pressure of the refrigerant has dropped so low, but if the temperature has also dropped so Having described some preferred forms of my invention it will be obvious that many m'odifications will become apparent to those skilled in the art and I therefore wish it to be understood that my invention is limited only by the scope of the appended claims.

I claim as my invention:

1. In a refrigeration system, an evaporator, valve means for controlling the flow of refrigerant through said evaporator, means responsive to a pressure corresponding to the temperature of the refrigerant at the evaporator outlet for adjusting the position of said valve means, means responsive to the pressure of the refrigerant at the outlet of the evaporator for modifying said first responsive means'in a manner to maintain the refrigerant leaving the evaporator.

at a substantially constant degree of superheat as the temperature and pressure of the refrigfor modifying the action of one of said last named means in a manner to cause the valve to maintain a different substantially constant degree of superheat of the refrigerant at the evaporator outlet for varying temperatures and pressures of the refrigerant at the outlet.

2. In a refrigeration system, an evaporator, valve means for controlling the flow of refrigerant through said evaporator, means responsive to the temperature of the refrigerant leaving the evaporator controlling the position of said valve means, means responsive to the pressure of the refrigerant on the suction side of the system for modifying the effect of the temperature responsive means, spring means cooperating with the pressure responsive means, means for adjusting the loading and spring rate of said spring means, to' cause the refrigerant at the evaporator outlet to be maintained at a substantially constant de gree of superheat which varies in accordance with the spring rate and loading on said spring means but which does not varyappreciably with normal changes of temperature or pressure of the refrigerant at the evaporator outlet.

3. In a refrigeration system, an evaporator, valve means for controlling the flow of refrigerant through said evaporator, means responsive to the temperature of the refrigerant leaving the evaporator controlling the position of said valve means, means responsive to the pressure of the refrigerant on thesuction side of the system for modifying the effect of the temperature responsive means, spring means cooperating with the pressure responsive means, means for adjusting the loading and spring rate of said spring means, to cause the refrigerant at the evaporator outletto be maintained at a sub- "erant leaving the evaporator vary, and means movement of said valve means upon a rise in pressure occasioned by a rise in temperature at said bulb, means responsive to the pressure of the refrigerant at the evaporator outlet for varying j the volume of said bulb to vary the effect of the a rator outlet.

6. In a refrigeration system, an evaporator, valve means for-controlling the fiow of refrigerant through the evaporator, pressure responsive means for controlling the position of said valve means, a fiuid filled expansible and contractible bulb responsive to the temperature of the refrigerant leaving the evaporator in communication with said pressure responsive means,

said pressure responsive means causing opening movement of said valve means upon a rise in pressure occasioned by a rise in temperature at said bulb, means responsive to the pressure of the refrigerant at the evaporator outlet for varying the volume of said bulb to vary the effect of the temperature of the refrigerant leaving the evaporator on the position of said valve means,

stantially constant degree of superheat which varies in accordance with the spring rate and loading on said spring means but which does not vary appreciably with normal changes of temperature or pressure of the refrigerant at the evaporator outlet, and means urging the valve in closing direction for preventing opening of the valve means whenever the temperature of the refrigerant at the evaporator outlet drops to a predetermined value irrespective of the pressure of the refrigerant at the evaporator outlet.

4. In a refrigeration system, an evaporator, valve means for controlling the flow of refrigerant through the evaporator, pressure responsive means for controlling the position of said valve means, a fluid filledexpansible and contractible bulb responsive to the temperature of the refrigerant leaving the evaporator in communication with said pressure responsive means,

pressure occasioned by a rise in temperature at said bulb, and means responsive to the pressure of the refrigerant at the evaporator outlet for varying the volume of said bulb to vary the effect of the temperature of the refrigerant leaving the evaporator on the position of said valve means.

5. In a refrigeration system, an evaporator, valve means for controlling the flow of refrigerant through the evaporator, pressure responsive means for controlling the position of said valve means, a fluid filled expansible and contractible bulb responsive to the temperature of the refrigerant leaving the-evaporator in communication with said pressure responsive means, said pressure responsivemeans causing opening and means controlling the change in volume of refrigerant at the evaporator outlet in a manner to maintain the superheat of the refrigerant leaving the evaporator at a substantially constant value regardless of normal variations in the pressure or temperature of the refrigerant at the evaporator outlet, said last named means including a spring and means for individually adjusting'both the loading and spring rate of said pring.

'7. In a refrigeration system, an evaporator, I

being located within the outletof the evaporator whereby it is subjected to the temperature of the refrigerant leaving the evaporator, said bulb being in communication with an expansible bellows, means responsive to the pressure in the outlet of the evaporator sealing said bellows and arranged to cause the expansion of said bellows upon a rise in pressure in the evaporator outlet, and biasing meansopposing movement of said last named pressure responsive means.

8. In a refrigeration system, an evaporator, valve means for controlling the flow of refrigerant through the evaporator, operating means for controlling the position of said valve means, said operating means including a first pressure responsive means operatively connected to said valve means, a second pressure responsive means, resilient means connecting said pressure responsive means and biasing the same towards one another, and means subjecting the adjacent portions of the pressure responsive means respectively to a, pressure corresponding tov the temperature of the refrigerant at the evaporator outlet and to the pressure on the suction side of valve means for controlling the flow of refrigerant through the evaporator, operating means for controlling the position of said valve means,

' of said spring means, and additional means for said operating means including a first pressure responsive means operatively connected to said valve means, a second pressure responsive means, resilient means connecting said pressure responsive means and biasing the same towards one another, means subjecting the adjacent portions of the pressure responsive means respectively to a pressure corresponding to the temperature of the refrigerant at the evaporator outlet and to the pressure on the suction side of the refrigeration system, additional springs means for biasing the second temperature responsive means towards the first pressure responsive means, and means for varying the loading and the spring rate of said springs means.

10. In a refrigeration system, an evaporator, valve means for controlling the flow of refrigerant through the evaporator, operating means for controlling the position of said valve means, said operating means including a pair of adjacent substantially parallelly arranged ,diaphragms, means sealing the adjacent faces of said diaphragms from one another, resilient means connecting said diaphragms and biasing the same towards one another, one of said diaphragms being connected to said valve means, means subjecting the inner face of said one diaphragm to a, pressure corresponding to the temperature of the refrigerant at the outlet of the evaporator, and means subjecting the inner face" of the other diaphragm to the pressure on the suction side of the refrigeration system.

11. In a refrigeration system, an evaporator, valve means for controlling the flow of refrig-' erant through the evaporator, operating means for controlling the position of said valve means,

evaporator, means urging the movable portion of said bellows in a valve closing direction, said means including a member movable in response to variations in pressure on the suction side of the refrigeration system and means comprising a tension spring connecting said member to the movable portion of said bellowsQ 12. In a refrigeration system, an evaporator, valve means for controlling'the flow of refrigerant through the evaporator, operating means for controlling the position of said valve means, said operating means including a bellows having a movable portion operatively connected to said valve, means subjecting the interior of said bellows to a pressure corresponding to the temperature of the refrigerant at the outlet of the adjusting the loading of said spring means.

13. In a refrigeration system, an evaporator, valve means for controlling the flow ofrefrigerant through the evaporator, means forming an expansible chamber having a pair of movable wall portions, tension means urging said wall portions towards one another, means operatively connecting one of said wall portions to the valve means, means subjecting the interior of said chamber to a pressure corresponding to the temperature of the refrigerant at the evaporator wall portions, tension means urging said wall portions towards one another, means operatively connecting one of said wall portions to the valve means, means subjecting the interior of said chamber to a pressure corresponding to the temperature of the refrigerant at the evaporator outlet, means urging said other wall portion in a direction to increase the tension of said tension means 'in response to an increase in pressure on the suction side of the refrigeration system, and adjustable spring means urging said second wall portion in a direction to decrease the tension of said tension means.

15. In a refrigeration system, an evaporator, valve means for controlling the flow of refrigerant through the evaporator, an operating member for said valve means, means responsive to the pressure of the refrigerant on the suction side of the refrigeration system, hydraulic force transmitting means for transmitting movements of said pressure responsive means to said valve means, said hydraulic force transmitting means including an expansible fluid, a portion of said expansible fluid being subjected to the temperature of the refrigerant leaving the evaporator whereby said valve means also moves in responseto variations in temperature of the refrigerant at the evaporator outlet. v

16. In a refrigerating system, an evaporator, valve means for controlling the flow ,of refrigerant through said evaporator, means responsive to the pressure and temperature of the refrigerant leaving the evaporator for controlling the valve to maintain the refrigerant leaving the evaporator at a substantially constant degree of superheat, said last means embodying means for compensating for variations in evaporator pressure so that the degree of superheat remains constant even though the evaporator pressure varies, means for adjusting the second mentioned means for varying the degree of superheat to be maintained by adjusting the responsiveness of said responsive means, said adjusting means embodying secondary adjusting means cooperating with said compensating means whereby variations in evaporator pressure are compensated for at the adjusted value of superheat so that degree of superheat may be maintained constant at selected values irrespective of evaporator pressure.

17. In a refrigerating system, an evaporator, valve means for controlling the flow of refrigerant through said evaporator, means responsive to the pressure and temperature of the refrig valve to maintain the refrigerant leaving the evaporator at a substantially constant degree of superheat, said last means embodying means for compensating for variations in evaporator pressure so that the degree of superheat remains constant even though the evaporator pressure varies, means for adjusting second mentioned means for varying the degree of superheat to be maintained by adjusting the responsiveness of said responsive means, said adjusting means emvalve means including a pressure chamber having a movable Wall portion, means communicating evaporator pressure to said chamber urging said wall portion in one direction, means forming a second pressure chamber having a movable wall portion, means producing a pressure in said last chamber corresponding to the temperature of refrigerant at the outlet of the evaporator, resilient means opposing movement of one of said wall portions, yieldable means interposed between said movable wall portions and a valve member connected to one of said wall portions adapted to assume a position depending on both wall portions, and said resilient means comprising a spring having manual means for adjusting both its loading and spring rate,the valve means being arranged to maintain a constant number of degrees of superheat at the outlet of the evaporator even though the evaporator pressure varies, the number of degrees of superheat depending on the adjustments of said manual means.

GIFFORD I. HOLMES.

Images