US2240374A - Expansion valve - Google Patents

Description

April 29, 1941.

A. B. NEWTON EXPANS ION VALVE Filed Aug. 8, 1938 Lu (1 E T 937 2 Sheets-Sheet 1 Abvixx B-Nevvlon Jnumtor C(itomg April 29, 1941. A. a. NEWTON 2,240,374

EXPANSION VALVE Filed Aug. 8, 1938 2 Sheets-Sheet 2 Fig. 3

Alwin B. Newlon 3nnentor attorney Patented Apr. 29, 1941 EXPANSION VALVE Alwin B. Newton, Minneapolis, Minn, assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application August 8, 1938, Serial No. 223,601

7 Claims.

This invention relates to expansion valves for use in refrigeration systems and more particular- 1y in thermostatic expansion valves of the diaphragm type.

One of the objects of this invention is the provision of a diaphragm type expansion valve of simple but rugged construction and which is so designed that it may maintain a constant value of superheat at the outlet of the evaporator of the refrigeration system.

Another object of the invention is the provision of a diaphragm type thermostatic expansion valve wherein the diaphragms are so constructed that fiexure thereof during operation of the valve does not affect the characteristics of the valve.

Another object of the invention is the provision of a thermostatic expansion valve of the type above described wherein the diaphragms may be constructed of rubber or like material and are so arranged that they are not subject to deterioration or rupture through long periods of use.

Other objects and advantages of the invention may become apparent to those skilled in the art upon reference to the specification, claims and accompanying drawings wherein like reference characters represent like parts in the various views; and wherein Figure 1 is a view in cross section of one form of expansion valve embodying my invention and operatively connected in a refrigeration system..

Figure 2 is a cross section of another form of expansion valve embodying my invention,

Figure 3 is a cross sectional view of a still further modification of expansion valve embodying my invention, and a I Figure 4 is a cross sectional view of a modification of a detail of the valve illustrated in Figure 3.

Referring more particularly to Figure 1, an expansion valve generally indicated by the reference character I is shown operatively connected toa refrigeration system, this system being of conventional form and including a compressor ll having its high pressure side connected by means of a pipe l2 with a condenser l3 emptying into a receiver 14, the outlet of the receiver being connected by a pipe l5 to the inlet is of the expansion valve. The outlet ll of the expansion valve communicates with the inlet of the evaporator l8 and the outlet of the evaporator communicates by means of pipe HI with the inlet of compressor H. The operation of the system is well understood by those skilled in the art and further descriptionthereof is believed tobe unnecessary.

The expansion valve l0 comprises casingmembers 22 and 23 which form valve chamber 24 and the operating chamber 25. The sections 22 and 23 are suitably connected together in any well known manner, there being sealing means 26 for preventing the escape of refrigerant from the interior of the chambers and the chambers 24 and 25 communicate with one another by means of a passageway formed in the inner wall 3i of the casing section 23. Pivoted within a recess 33 of the wall of the casing section 22 is a lever 35 carrying a valve element 36 which cooperates with a seat 31 which may be removable as'illustrated and a spring 38 seated in a recess 39 in the wall of casing section 22 abuts against the arm 40 of the lever 35 and biases the valve element 36 into seating engagement with the valve seat 31.

Refrigerant enters the valve chamber at I6 and the spaces 24 and 25 will be filled with comparatively warm refrigerant and the valve element 33 controls the expansion and flow of this refrigerant into the evaporator l8 as will be understood.

The operation of the lever 35 is controlled by a pair of diaphragms 42 and 43 which are rigidly connected together at their central portions by means of an apertured rod 44. The diaphragm 43 is rigidly held between a shoulder 46 in the ingvmeans 58 positioned between the plate and g with a capillary tube 66 which terminates in a casing section to prevent escape of refrigerant therefrom.

The space below'the diaphragm 43 communicates with the outlet of the evaporator by means of a pipe 60 connected at one end to the wall 48, its other end being flared and held by means of a nut 52 in engagement with the member 63 which may be threaded into the outlet of the evaporator or otherwise suitably secured thereto. It should now be apparent that the pressure with in the space below the diaphragm 43 will be the same as the pressure at the outlet or the suction side ofthe evaporator Hi.

The passageway in the rod 44 communicates.

at its upper end with the space formed between the diaphragm 42 and the upper plate 51 and the lower end of this passageway communicates bulb 61 located within the outlet of the evaporator. This tube, bulb, and the space above the diaphragm 62 may be provided with a suitable volatile fill which may be the same substance as the refrigerant used in the system and therefore the pressure in the space above the diaphragm M will be the same as the pressure corresponding to the temperature of the refrigerant leaving the evaporator it. The diaphragm 43 will tend to move upwardly as the pressure in the outlet of the evaporator increases and thus move the rod 36 and a pin ill carried thereby upwardly in re I sponse to an increase in pressure. The pin it limits the movement of the valve 38 toward its closed position under the influence of the biasing spring 39 since the extremity of the lever 35 is held against this pin. Accordingly as the pin moves downwardly the valve element 36 will move towards open position against the force of the spring 38. As the temperature of the refrigerant leaving-the outlet of the evaporator increases the pressure in the space above the diaphragm M will increase and move this diaphragm downwardly which will tend to open the valve 36. It will therefore be seen that the position of the pin it and consequently of the valve 3% will depend both upon the pressure of the refrigerant at the outlet of the evaporator and also upon the temperature of the refrigerant, or in other words, upon the superheat of the refrigerant at the evaporator outlet.

It is a characteristic of all known refrigerants that as the temperature of the refrigerant increases the pressure corresponding to the temperature increases at a greater rate so that the pressure exerted upon the diaphragm 42 tending to open the valve will not vary in a straight line relationship with the temperature. The result of this is that if the effective areas of the diaphragms are equal the superheat existing at the evaporator outlet will vary in accordance with variations in temperature of the refrigerant at the evaporator outlet. As the superheat at the outlet increases the effective cooling area of the evaporator decreases and. it is desirable to use as much of the evaporator at all times as is possible for cooling in order that the system may operate'at maximum efiiciency. In order to do this the'superheat at the outlet of the evaporator should be kept substantially constant at all times and one way of accomplishing this is by making the efiective area of the diaphragm 62 which is exposed to the pressure corresponding to the temperature at the evaporator outlet less than the efiective area of the other diaphragm by an amount which is suificient to compensate for the deviation of the temperature pressure curve of the refrigerant from a straight line relationship.

This is accomplished by the provision of a sealing bellows it-which is suitably connected to the upper portion of the rod M, the lower end of this sealing bellows being suitably secured to a cup-shaped member 36 which is in turn secured to the upper plate member This sealing bellows thus serves the purpose of permitting movement of the rod id with the diaphragms 3 2 and i3 while preventing escape of refrigerant from the upper chamber or preventing entrance of air into this chamber around the rod and at the same time it reduces the area of the diaphragm 62 since the pressure within this upper chamber above the diaphragm will act upwardly on the bellows l5 and thusdecrease the eiiective area of the diaphragm' 52 by an amount which is equal to the area of the bellows i5.

is an adjusting nut 18 against which bears a compression spring 19, the lower end of this spring bearing against the plate 8t! which is rigid with the top plate 51 of the casing 23. This spring tends to urge the rod M upwardly and the valve towards closed position and thus opposes the opening action. of the diaphragm 42. By properly adjusting this spring 19 in accordance with the size of the bellows 15 the superheat which is maintained at the outlet of the evaporator will be maintained substantially constant. If it is desired to vary the amount of superheat that is maintained this may be done by suitable adjus'tment of the nut 78 although this adjustment will have the eflfect of causing variations in superheat at the evaporator outlet as the pressure and temperature varies therein, although the amount of this deviation will be slight for a small adjustment of the spring '79.

It will now be understood that as the pressure of the refrigerant leaving the evaporator rises the diaphragm 43 tends to move upwardly and the valve moves towards closed position but as the temperature of the refrigerant leaving the evaporator increases the diaphragm 42 will move downwardly causing'an opening movement to be imparted to the valve thus permitting flow of more refrigerant into the evaporator l8 and in this manner the valve is properly positioned to maintain the desired degree of superheat at the outlet of the evaporator.

Referring now to Figure 2, an expansion valve is illustrated which operates in the same manner as the valve of Figure 1 but having a somewhat diflerent construction. In this form of the invention the valve casing 22 is shown as being positioned below the casing 23.

The valve 90 is vertically movable and includes a stemfli slidable within .a. boss 92 projecting downwardly from the top wall 93 of the casing '22. A spring 94 positioned between the wall 93 and the valve element 90 urges this valve into closed position. Positioned at each side of the valve are levers 95 which may be fulcnuned about knife edges 96, these levers having their inner ends positioned below the circular flange 9! of the valve 90 and their outer ends being connected to rods 98 which extend through openings 99 in the wall 93 and having their upper ends abutting the operating structure "II. The biasing spring 95 besides urging thevalve towards closed'position also urges the outer portions of the levers95 upwardly so that the upper endsfofthe rods 98 are held in engagement with the underside of the structure I01. Sealing bellows I03 suitably secured to the rods 98 and having their other ends secured to the wall Threaded to the upper extremity of the rod i5 93 of the casing 22 prevent the flow of refrigerant into the interior of the casing 23.

The operating structure for the valve comprises a pair of rubber diaphragms or diephragms of similar material 1105 and me which are suitably held against a piston member'illl by means of the plates Hi8 and I99 which are in threaded engagement with 'extensionsof the piston it? and serve to clamp the diaphragms be- 23, the ring shaped member H2, and the extension ill of the top wall II6 are provided to permit flexing of the diaphragms I05 and I06.

The piston I01 and its threaded extensions are provided with a passageway I25 which communicates with the space formed between the plate I09 and the top wall H6 and the lower end of this passageway is connected to the capillary tube I21 having its other end connectedwith a bulb mounted in the outlet of the evaporator as in Figure 1. The pipe I30 connects the outlet of the evaporator with the space below the plate I09 in the same manner as in Figure 1.

The end of the upper projecting portion I34 of the piston I01 terminates in the threaded portion I35 which carries an adjusting nut 18 to vary the tension of the compression spring 19 having its lower portion resting upon a plate 80 as in Figure 1. Sealing bellows 15 connected to the rod I34 and having its lower end connected to the cup-shaped member 16 acts in the same way as in Figure, 1 to decrease the efiective area of the upper portion of the assembly II and at the same time seals the rod I34 while at the same time permitting movement thereof.

Shoulders I40 and I provided in the vertical walls of the casing 23 and in the upper member II6 limit the movement of the piston I01 and therefore the amount of flexing of the diaphragms I05 and I06. While ordinarily, during the operation of this valve, there will be very slight movement of the structure IOI, these shoulders prevent any extensive movement thereon should this occur through any abnormal circumstances.

In operation this valve will function in the manner similar to that of Figure 1, the structure IOI moving downwardly as the pressure above the plate I08 increases by reason of an increase in temperature of the refrigerant at the evaporator outlet, this movement causing the inner ends of the levers 95 to move upwardly thus opening the valve 90. As the pressure of the refrigerant at the evaporator outlet in- ,creases the pressure below the plate I09 will increase and urge the assembly I0l upwardly whereupon the valve 90 will move towards closed position under the influence of the biasing spring 94. The provisionof the sealing bel-= lows 15 insures the maintenance of a constant degree of superheat at the evaporator outlet as in Figure 1.

The space in the casing section 22 must be sealed in the, casing 23 in this figure to prevent the pressure of the entering refrigerant from acting upwardly on the operating assembly H. This sealing of the two chambers was not necessary in Figure 1 since the entering refrigerant acts equally but in opposite directions upon the diaphragms 42 and 43 and thus would have no effect upon the operation of the valve 36. One advantage of using rubber-like diaphragms in place of metallic diaphragms as in Figure 1 is that the metal diaphragms exert an increasing force opposingthe flexure thereof as the diaphragms become flexed to a greater degree but upon an increase in temperature of the refrigerant at the evaporator outlet the diaphragm 43 moves upwardly. The extremity of the lever is positioned above the movable abutment 10 and the position of the valve 36 and the spring 38 is shown reversed from that of Figure 1. Accordingly as the lever 35 moves upwardly in response to an increase in temperature of refrigerant at the outlet of the evaporator the valve 35 moves towards open position. The pipe 60 which connects with the-outlet of the evaporator is connected to a pipe I50 which in turn communicates with the passageway through the member I5I which connects the diaphragms 42 and 43 together, this passageway opening into the space above the diaphragm 42 so that as the pressure of the refrigerant at the outlet of the evaporator increases the diaphragm 42 will be urged downwardly thus permitting movement of the valve 36 towards closed position under the influence of the biasing spring 38;

The rod I5I which connects and separates the diaphragms 42 and 43 does not extend outwardly from the top wall I51 of the casing but terminates within the space between thediaphragm 42 and the top wall I51. Threaded within the top wall I51 is an adjusting screw I58 which is sealed by means of a suitable packing gland I59 in the top wall I51. A compression spring I65 is connected between the cup-shaped members I66 and I61 held against the opposing ends of the screw I58 and the member I51, respectively. This spring I tends to move the connecting member I5I downin the case of the diaphragms of Figure 2 this a wardly or in a position to permit the closing of the valve 36 and in this manner opposes the opening movement of the diaphragm 43 which is exposed to a pressure corresponding to the pressure of the refrigerant at the outlet of theevaporator. The adjustment of .the spring I65 is readily effected by turning the adjusting screw I58 as is readily apparent and a cover member I10 screw threaded over the projecting portion ill of the-plate I51 serves to protect the upper end of the screw I58 and to prevent unauthorized tampering therewith. l

In this form of the invention the spring I 65 is housed entirely within the valve structure and there is no member projecting outwardly from the casing which is constantly moved as the valve changes position. The arrangement of Figures 1 and 2 however has the advantage that movement of the expansion valve is readily ascertained by watching the movement of .the adjusting nut 18 and also in these first two figures the use of the sealing bellows provides for the maintenance of a constant degree of superheat.

A modification of the structure shown in Figure 3 is illustrated in Figure 4 wherein the upper end of member l5l projects through the top wall I51 of the casing and screw threaded to the exterior of the plate I51. is'a cup-shaped adjusting member 80 forming an abutment for a compression spring I8I having its lower end seated on the spring retainer 102 fitted on the end of the member I51. The member 151 will move with the diaphragm assembly but, the upward movement of this member which corresponds to the opening of the expansion valve is opposed by the spring I8! and the force of this spring is readily adjusted by the member I 90. The adjusting member I may be concealed and protected by meansv of the cover I screw threaded to the wall I 51 as illustrated. Asuitable packing gland I81 is provided for sealing the rod I5I and the plate I51 together.

It will be. readily apparent that this adjusting means may be substituted for the adjusting means of Figure 3 if it is desired to have the compression spring I65 of Figure 3 outside of the casing as in Figure 4, the operation of the valve being in no way affected by this modification.

Having described the preferred forms of my invention many modifications may become apparent to those skilled in the art and I. 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 including an evaporator, means for controlling the flow of refrigerant into the evaporator, said means comprising a valve body divided by an apertured wall into a valve chamber and an operating chamber, saidvalve chamber having an inlet and an outlet through which refrigerant flows on the way to the evaporator, a valve member in said valve chamber for controlling the flow of refrigerant from the inlet to. the outlet, a diaphragm structure including a pair of diaphragms in said operating chamber spaced from the top and bottom thereof and spaced from one another, means clamping the edges of said diaphragms to the wall of said operating chamber and means rigidly connecting the central portions of said diaphragms together, said connecting means having a passageway therethrough, means extending through the aperture in said wall operatively connecting said diaphragm structure to said valve member, a pair of pressure communicating means connected to a wall of said operating chamber opposite one of said diaphragms, one of said pressure communicating means opening into the space opposite said one diaphragm, the other of said pressure communicating means being connected through the passageway in said rigid connecting means to the space opposite said other diaphragm, means connecting one of said pressure communicating means to the outlet of the evaporator, and means connecting the other of said pressure communieating means to a bulb exposed to the temperature of the refrigerant leaving the evaporator, said bulb having a volatile fill.

2. In a refrigerating system including an evaporator, means for controlling the flow of refrigerant to the evaporator, said means comprising a valve body separated by an apertured wall into a valve' chamber and an operating chamber, said valve chamber including an inlet and an outlet, a valve member in said valve chamber for controlling the flow of refrigerant from the inlet to the outlet, an operating arm for controlling the position of said valve member and extending through the aperture in said wall, a member in said operating chamber movable in response to variations in superheat at the evaporator outlet, said member comprising a pair of parallelly arranged diaphragms having their adjacent sides rigidly connected together at their centers and having their edges rigidly secured to the walls of the chamber, means providing an operative connection between said member and said operating arm, means exposing the other side of one of said diaphragms to.a pressure corresponding to the temperature of the refrigerant at the evaporator outlet, means exposing the other side of said other diaphragm to the pressure on the suction side of the refrigeration system, means biasing said valve towards closed'position, said means being located on the exterior of said casing, and means for varying the biasing effect of the biasing means.

3. In a refrigerating system including an evaporator, means for controlling the flow of refrigerant to the evaporator, said means comprising a valve body separated. by an apertured wall into a valve chamber and an operating chamber, said valve chamber including an inlet and an outlet, a valve member in said valve chamber for controlling the flow of refrigerant from the inlet to the outlet, an operating arm for controlling the position of said valve member and extending through the aperture in said wall, a member in said operating chamber movable in response to variations in superheat at the evaporator outlet, said member comprising a pair of parallelly arranged diaphragms having their adjacent sides rigidly connected together at their centers and having their edges rigidly secured to the walls 1 of the chamber, means providing an operative connection between said member and said operating arm, means exposing the other side of one of said diaphragms to a pressure corresponding to the temperature of the refrigerant at the evaporator outlet, means exposing the other side of said other diaphragm to the pressure on the suction side of the refrigeration system, means biasing said valve towards closed position, and means rendering the effective operating area of the diaphragm exposed to the pressure corresponding to the temperature of the refrigerant at the outlet of the evaporator less than the effective operating area of the other diaphragm by an amount suiiicient to insure the maintenance of a substantially constant degree of superheat at the evaporator outlet.

4. In a refrigerating system including an evaporator, means for controlling the flow of refrigerant to the evaporator, said means comprising a valve body separated by an apertured wall into a valve chamber and an operating chamber, said valve chamber including an inlet and an outlet, a valve member in said valve chamber for controlling the fiow of refrigerant from the inlet to the outlet, an operating arm for controlling the position of said valve member and extending through the aperture in said wall, a member in said operating chamber movable in response to variations in superheat at the evaporator outlet, said member comprising a pair of parallelly arranged diaphragms having their edges rigidly secured to the walls of the chamber and means forming a rigid connection between the centers of the diaphragms, means providing an operative connection between said member and said operating arm, means exposing the other side of one of said diaphragms to a pressure correspondiing to the temperature of the refrigerant at the evaporator outlet, and means exposing the other side of said other diaphragm to the pressure on the suction side of the refrigeration system, said last named means including the means forming the connection between said diaphragms.

5. In a refrigeration system including an evaporator and valve means for controlling the flow of refrigerant to the evaporator, said valve means comprising a valve member and a cooperating valve seat, means for controlling the position of the valve member with respect to said seat comone side of said diaphragm assembly to the pres-' sure on the suction side of the refrigeration sysphragm assembly to the pressure corresponding to the temperature of the refrigerant at the evaporator outlet, means biasing said valve member towards closed position, and means rendering the efl'ective operating area of said other side of said diaphragm assembly less than the effective operating area of said one side of said diaphragm assembly by an amount sufiicient to insure the maintenance of a substantially uniform degree of snperheat at the evaporator outlet.

6. In a refrigeration system, including a compressor and an evaporator, valve means for controlling the flow oi. reirigerant into the evaporator, said means comprising a casing divided into a valve chamber and an operating chamber, said valve chamber including an inlet and an outlet. a valve member in said valve chamber controlling the flow of refrigerant from the inlet to the outlet, the operating chamber having a piston slidable therein, means sealing said piston to the sides of said operating chamber, means operatively connecting said piston and said valve membenmeans exposing one side of said piston to the pressure on the suction side of the refrigeration system, and means subjecting the other 7. In a refrigeration system including an evaporator and valve means for controlling the flow of relrigerant to the evaporator, said valve means comprising a valve member and a cooperating valve seat, means for controlling the position of the valve member with respect to said seat comprising a diaphragm assembly including a pair of diaphragm members of rubber-like material parallelly arranged and rigidly connected together, a chamber housing said diaphragm members with the members suitably secured to the walls of said chamber, means connecting said diaphragm members with said valve member, means exposing one side of said diaphragm assembly to the pressure on the suction side of the refrigeration system, means exposing the other side of said diaphragm assembly to the pressure corresponding to the temperature of the refrigerant at the evaporator outlet, means limiting movement 0! the diaphragm members in either direction to prevent rupture thereof, means biasing said valve membertowards closed position, and means reducing the effective operating area, of said other side of said diaphragm assembly by an amount sumcient to insure the maintenance of a substantially uniform degree of superheat at the evaporator outlet,

' ALWIN B. NEWTON.

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