US3246840A - Temperature responsive bimetal actuated valve - Google Patents

Description

Apnl 19, 1966 A. A. MATTHIES 3,246,840

TEMPERATURE RESPONSIVE BIMETAL ACTUATED VALVE Filed May 28, 1965 EvAPoRATog C0MPRSSOR x, I :c m 20 m 20 20 0 2 c a 2 g E E 5 O. 8 8 I o l l 70 2o '10 '20 5o 70 EVAP. PR. EV P. PR. EVAP. PR.

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INVENTOR. ALAN H- Mmnues ATTORNEY United States Patent 3,246,840 TEMPERATURE RESPONSIVE BIMETAL ACTUATED VALVE Alan A. Matthies, Milwaukee, Wis., assignor to Controls Company of America, Melrosc Park, 111., a corporation of 'Delaware "FiledMay 28, 1963, Ser. No. 283,877

9' Claims. (Cl. 236-91) This invention relates to improved expansion valves for use in refrigeration systems.

An object of this invention is to provide an expansion valve having improved operating characteristics.

A further object of this invention is to eliminate pressure sensitive diaphragms, charged bulbs, and capillary tubing from expansion valves;

Another object is to. provide an expansion valve which can operate atvirtually any'systempressure. without'ad- Verse effect on its life. ALfurther object ofthe invention is to provide an expansion valve which does not lose control to external ambient conditions.

- Other objects and advantages will be pointed out in, or be'apparent from, the specification and claims, as will obvious. modifications of the various embodiments'shown in the drawings, in which:

FIG. 1 is a vertical section through the valve with the refrigeration system shown schematically;v and FIGS. 2, 3 and 4 are various exemplary superheat temperature-evaporator pressure curves which may be obtained with variations on the present construction.

Inlet 10 leading from the. receiver 11 passes through the housing wall. 12 to terminate in the central portion of sleeve 14- in which the balanced valve 16 is slidably mountedr Thus, the inlet pressure acts against the upper and. lower ends. of the balancedvalve, so as to have no effect on its operation. The valve is shown in the position it occupies when it has just cut off flow through the orifices or'slots 18 in the lower portion of the sleeve. Spring 19 is compressed betweenthehousing wall and the upper end of thevalve to bias the valve to follow the motion of the valve operator 20. When. the valve 16 moves downwardly from its illustrated position, refrigerant will flow through the orifices 18 into chamber22 and through outlet 24 to the system evaporator 25. Flow from the evaporator comes back through fitting 26 into the lower chamber 28 and out throughfitting 30 which leads to the inlet of com pressor.31.

Chambers22 and 28 areseparated by the partition wall- 32 threadably mounted inside the housing 12. Gland nut 34 is mounted in the central portion of partition 32 with its upper end projecting above the upper surface of the partition as illustrated. A bimetal stack 36 is mounted between the upper end of the gland nut and the underside of flange 38 on the top of valve operator 20 which passes through the gland nut.

The bimetal stack 36 consists of a plurality of predished bimetallic discs with their low expansion sides adjacent and their high expansion sides adjacent so that the stack tends to increase in thickness (or produce an increasing force) with an increase in temperature. Another bimetal stack 40 ismounted between the bottom of the gland 34 and nut 42 threaded on the lower end of the. valve operator 20. A third stack 44 rests on the top wall of the partition 32 and is designed, when operative, to increase in dimensional thickness to the point where it will actdirectly against the bimetal stack 36 and add its force to that of stack 36.

It will now be. appreciated that stacks 36 and 44 in valve and for this discussion, we'might assume that the so many variations in operating characteristics, it is bestto understand the various principles involved by considermg some of the possibilities separately before the total structure and its possible variations are considered. Therefore, this discussion will first be directed towards operation of this type of valve'as a thermostatic expansion bimetal stack'44 is removed, leaving only stacks 36 and 40. Let us further. assume that these two stacks are identical in all respects andeach will tend to increase its thickness as the temperature surrounding it. increases. Under such circumstances, it will be apparent that the outlet stack 40 will. have to be warmer than the inlet stack 36 for it to move the valve operator 20 in the valve opening direction. Since the refrigerant is always at its saturation temperature at the coil inlet and remains atthat temperature throughout the coil until the last drop is boiled ofif, any increase in temperature at the evaporator outlet represents a refrigerant superheat condition (neglecting coil pressure drop). Any increase in evaporator load will increase the superheat or, put another way, the temperature at stack 40 which will result in an opening movement of the valve to pass more refrigerant to meet these increases in load and re-establish system balance.

As mentioned above, the valve is shown in the just closed position. Any desired superheat condition can be obtained by turning the valve partition wall in or out (up or down). In the illustrated position, there would be an approximate Zero degrees openingsuperheat setting. If the wall is turned in, the relative temperature rise of the outlet stack 40 with respect to inlet stack 36 necessary. to open the valve will increase and, therefore, the superheat setting will be elevated. Whatever the setting, the superheat setting will remain constant without regard for operating pressure of the evaporator, as shown by the line A in the temperature-pressure curve of FIG. 2. It should be appreciated that changing the relative strength of the two stacks can be used to adjust the superheat curve of- FIG. 2. Thus, if the outlet stack 40 is made more active (thicker or more powerful) than the inlet stack 36, the curve can be made to slope downwardly, as illustrated by curve B in FIG. 2. The converse of this is true also, that is, if. the inlet stack is more powerful than the outlet stack an upward slope such as curve C may be obtained. One point should be noted here with respect. to the foregoing description where it was said that any increase in temperature at the coil outlet represents a refrigerant superheat condition (neglecting coil pressure drop). Actually, there is always somecoil pressure drop and it is of interest to'note that the present construction can compensate for this quite readily. Thus, it will be noted that the valve operator shaft 20 is subjected to a pressure drop which will be equivalent to the evaporator pressure drop. This tends to feed more refrigerant to the coil which, in turn, tends to compensate for the increase in superheat which would normally result from coil pressure drop, The diameter of the operator shaft 20 can be selected to create a desired differential force such thatthe resultant defiection and valve opening compensate exactly for the pressuredrop of the coil. Therefore, evaporator pressure drop is easily compensated without additional parts or cost and becomes virtually an inherent characteristic of the present expansion valve. This, therefore, overcomes a particularly troublesome problem 0 the prior art in a most satisfactory way. j

The foregoing description of this valve operating as a thermostatic expansion valve eliminated stack'44. It'is interesting to note that this same basic construction can be made to operate as an automatic expansion valve (a constant pressure valve) by the further elimination of the outlet stack 40. This would necessitate, of course, sealing the lower end of the gland nut 34 to prevent leakage down past the operator stem 20 and, in effect, the partition 32 can be considered the outside of the valve body. Under these conditions, there is only stack 36 left in operation and with this stack calibrated to control at any desired temperature it is obvious that any increase in evaporator temperature will result in heating the stack to decrease the refrigerant how to bring about a decrease in evaporator temperature. Therefore, the control will maintain a constant evaporator pressure by sensing and modulating in response to the corresponding saturation temperature of the evaporator. While not shown on FIG. 2, this can be considered a vertical line on the chart.

The just described automatic expansion valve operation can be combined with thermostatic valve characteristics by using the construction shown in FIG. 1 except that stack 44 will still be removed and the operating characteristic of the outlet stack 40 will be modified so that it becomes slack (the over-all stack dimension becomes less than the dimension between the bottom of gland nut 34 and the retaining nut 42) at some predetermined low temperature with the result that it becomes functionless, since it is no longer able to balance out the inlet stack 36. At this predetermined temperature, the valve is controlled exclusively by the inlet stack so that the action is identical to that just described with respect to the automatic expansion valve operation per so. This gives a very unique characteristic in that the thermostatic expansion valve can be provided with a low temperature limit at which conversion takes place from thermostatic to automatic expansion valve operation. The curve obtainable with such an arrangement is shown in FIG. 3.

At this point in the description we can consider the active function of stack 44 which has been eliminated from consideration in the previous operational characteristics. This stack is designed to be slack at temperatures below a predetermined high temperature limit or 'knock oil temperature as it is known in the trade. On reaching this predetermined high temperature, the stack will have increased in dimension to the point where it starts acting against the-underside of stack 36 to add its force to that of stack 36 which greatly increases the amount of bimetallic material subject to evaporator inlet conditions. The temperature at which this transition will take place can be calibrated by adjusting the projecting length of gland nut 34. The longer the projection, the higher the knockoff temperature When"the knock-off point is reached, the valve closing action with increasing evaporator temperature is much faster than when only stack 36 was operative. This has the net effect of sharply increasing the evaporator superheat (by starving the coil) and, therefore, limits the maximum temperature the evaporator can reach, regardless of load. This high temperature limit characteristic is important since it prevents overloading the compressor by limiting the flow of refrigerant to a safe maximum. By way of illustrating the versatility of the present control, this could still be combined with the automatic expansion valve (AXV) characteristic to result in an operational curve such as shown in FIG. 4. If the AXV characteristic was not desired, the vertical portion of this curve could be eliminated so that the straight line horizontal constant superheat thermostatic valve operation would obtain throughout the pressure range. It is of interest to note that both ends of the FIG. 4 curve can be made to move in the opposite direction with some modification to the present construction. Thus, the modified curvewould havethe flow pressure (flow temperature) curve ris'e-vertically rather than-drop vertically while the high pre'ssu'r'eslope would become downward instead of upward. This is all done by moving stack 44 to chamber 28 to be slack below a predetermined high temperature and go solid (and become operational) at the predetermined'high temperature and having'the inlet stack 36 go slack when the evaporator temperature decreased to some predetermined level. This is not particularly significant from the standpoint of common refrigeration control practice, but is interesting insofar as it illustrates the extreme versatility of this construction and concept.

In the foregoing description, stacks 36 and 40 operate directly between a solid abutment and the valve operating shaft 20. If desired, a spring can be interposed between each although this still results in a constant superheat, assuming the stacks are equal and the springs are equal. This does permit modifying the curve, however, by keeping constant stacks and merely changing the spring rates applied between each stack and the valve operating shaft. Still another approach would be to interpose a spring between one stack only and the shaft. With these variations, the curves can be made adjustable without changing the size of the stack. A further design variation would be to have a stack comparable to stack 44 but so designed as to contract, rather than expand, with increasing temperature and thereby permit removing such a stack.

conditions, it may be desirable to employ auxiliary stacks comparable to 44 on both sides of the partition and these could be either expanding or contracting with'increasing temperature or could be a combination. Thus, all of these ways of approaching any design problem will permit adjusting the curve to meet the requirements far better than anything heretofore proposed in this industry. Indeed, it is possible to provide a series of auxiliary stacks on one side or the other so as to become progressively effective or to be progressively removed from operation.

Although various embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

. I claim:

1. A valve comprising, a housing having a partition tween the chambers, a bimetal sensor in each chamber and connected to the operator to regulate the valve to maintain a desired temperature dilferential between the chambers, the size of the operator and the characteristics;

of the bimetal sensors being selected to influence valve motion to maintain desired temperature and pressure differentials between the chambers.

2. A valve comprising, a housing, a partition in the housing dividing the housing into first and second chambers, a valve operator passing through the partition, a bimetal stack in each chamber seated against the partition and connected to the operator, an inlet to and an outlet from each chamber, a valve in the first chamber for regulating flow from the inlet to the outlet, a third bimetal stack in one of the chambers engageable with the valve operator only in a portion of the operational temperature range of the valve to thereby modify the valve operation in said portion.

3. A valve comprising, a housing, a partition in the housing dividing the housing into first and second chambers, a valve operator passing through the partition, a bimetal stack in each chamber seated against the partition and connected to the operator, an inlet to and an outlet from each chamber, a valve in the first chamber for regulating flow from the inlet to the outlet, said partition being adjustably movable in the housing whereby the partition and the bimetal stacks seated thereagainst may be moved as a unit to adjust the temperature differential between the chambers necessary to open the valve.

4. A valve according to claim 3 in which the operator is subjected to the pressure difierential between the chambers and modifies the valve movement in accordance therewith.

5. A valve according to claim 4 in which the valve is of the balanced type unaffected by inlet pressure.

6. A valve comprising, a housing having first and second chambers, an inlet and an outlet for ecah chamber, a valve in the first chamber, a valve actuator, a bimetallic sensor in each chamber operatively engaging the actuator at all times whereby the movement of the actuator is determined by both sensors, and another sensor in one of the chambers having a lost motion connection to the operator whereby said another sensor affects movement of the actuator only in a portion of the temperature range.

7. A valve comprising, a housing, a partition dividing the housing in-to first and second chambers, an inlet and an outlet for each chamber, a boss threaded into the partition, a valve operator passing through the boss and partition, a stack of bimetals in each chamber, each stack seating on the boss and engaging the operator, a valve operated by the operator, and a third bimetal stack in one chamber having a lost motion connection with the other bimetal stack in that chamber and fitting between said other stack and the partition whereby the boss may be threadably adjusted relative to the partition to adjust the temperature at which the third stack becomes operative.

8. A valve according to claim 7 in which the partition is threaded into the housing to permit adjustment of the bimetal stacks relative to the valve.

9. A valve comprising, a housing divided into two chambers each having an inlet and an outlet, valve means in one chamber for regulating fiow therethrough, bimetal sensor means in each chamber, actuator means interconnecting the sensor means whereby the forces are opposed, said actuator means being connected to the valve means whereby the valve means is actuated in accordance with the net force and motion of the sensor means, and means for adjusting the actuator means and both sensor means as a unit relative to the valve means whereby the operating temperature diiTerential of the valve may be adjusted.

References Cited by the Examiner UNITED STATES PATENTS 990,772 4/1911 Pollard 62-212 1,219,515 3/1917 Whittelsey 23693 X 2,159,819 5/1939 Snediker 23612 2,651,467 9/1953 Troy 236-12 2,700,716 6/1955 Grooms 23691 2,964,243 12/ 1960 Jorgensen 23659 3,090,559 5/1963 Bayer 23612 3,169,704 2/1965 Domm et al 23659 OTHER REFERENCES Publication: Principles of Industrial Process Control, by Eckman, pp. 88-91, published by John Wiley, New York, 1945.

ALDEN D. STEWART, Primary Examiner.

MEYER PERLIN, WILLIAM F. ODEA, Examiners.

Claims (1)

1. A VALVE COMPRISING, A HOUSING HAVING A PARTITION THEREIN DIVIDING THE HOUSING INTO FIRST AND SECOND CHAMBERS, AN INLET TO AND AN OUTLET FROM EACH CHAMBER, A BALANCED VALVE IN THE FIRST CHAMBER REGULATING FLOW THERETHROUGH UNAFFECTED BY INLET OR OUTLET PRESSURES, A VALVE OPERATOR PASSING THROUGH THE PARTITION AND CONNECTED TO THE VALVE WHILE BEING SUBJECTED TO THE PRESSURE DIFFERENTIAL BETWEEN THE CHAMBERS, A BIMETAL SENSOR IN EACH CHAMBER AND CONNECTED TO THE OPERATOR TO REGULATE THE VALVE TO MAINTAIN A DESIRED TEMPERATURE DIFFERENTIAL BETWEEN THE CHAMBERS, THE SIZE OF THE OPERATOR AND THE CHARACTERISTICS OF THE BIMETAL SENSORS BEING SELECTED IN INFLUENCE VALVE MOTION TO MAINTAIN DESIRED TEMPERATURE AND PRESSURE DIFFERENTIALS BETWEEN THE CHAMBERS.

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