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Publication numberUS2260682 A
Publication typeGrant
Publication dateOct 28, 1941
Filing dateNov 24, 1939
Priority dateNov 24, 1939
Publication numberUS 2260682 A, US 2260682A, US-A-2260682, US2260682 A, US2260682A
InventorsRobson Hector Harris
Original AssigneeUnited Fruit Co
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Automatic expansion valve
US 2260682 A
Abstract  available in
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Claims  available in
Description  (OCR text may contain errors)

Oct. 28, 1941. H. H. ROBSON AUTOMATIC EXPANSION VALVE 1939 2 Sheets-Sheet 1 Filed Nov. 24

M a u i 5 Tm k WA Q ATTORNEY 1941a H. H. ROBSON AUTOMATIC EXPANSION VALVE Filed Nov. 24, 1939 2 Sheets-Sheet 2 NW un mm Q wfi ah h QM! WM N w mm, mm I II II "I ll pr f IT IN n u w- .cm NV I +Ill| II WW I [I]! V I I f I! I INVENTOR 519: mvk k M ATT Patented Oct. 28, 1941 2,260,682 7 AUTOMATIC EXPANSION VALVE Hector Harris Robson, Scarsdale, N. Y., assignor to United Fruit Company, Boston, Mass., a corporation of New Jersey I Application November 24, 1939, Serial No. 305,812 I Claims.

This invention relates to expansion valves for use in refrigerating systems and its object is to provide an improved automatic control for the valve which insures admission to the evaporator of precisely the right amount of refrigerant for optimum refrigeration under varying conditions of temperature and pressure within the evapora-- tor. Thus, it is well known that in most systems maximum efiiciency is attained by maintaining a slight amount of superheat at or adjacent the evaporator outlet or the compressor inlet and by my invention I am able so to regulate automatically the size of the valve opening as to admit that amount of refrigerant which will maintain such superheat to within a fraction of a degree F., for any normal range of pressure and temperature fluctuations within the evaporator or for any change in the capacity of the system. My system furthermore achieves that precision of regulation even with refrigerants such as carbon dioxide which have comparatively low critical temperatures and therefore which may be presented to the expansion valve in the form of a gas or a liquid or a mixture of both depending upon varying working conditions within the condenser.

In the drawings:

Fig. 1 is a diagrammatic view of apparatus embodying my invention;

Fig. 2 is a side elevation view, partly in section, and Fig. 3 is an end elevation view; of y a motorized valve which I preferably employ.

In Fig. 1 the numeral 2 represents a compressor of usual construction for withdrawing refrigerant from the evaporator coil 4, through suction header 6 and pipe 8 and for forcing compressed refrigerant through pipe ID to a condenser coil l2, whose turns are suitably cooled by an external medium. From the condenser l2 the condensed refrigerant passes through pipe 14 to an expansion valve l6 Where the fluid is expanded as it passes through outlet I8 and thence to the evaporator coil 4. Except as hereinafter indicated, all of the above described apparatus is of conventional construction and operation.

The expansion valve 16 is shown enlarged in Figs. 2 and 3. It includes an inlet port 20 and an outlet port 22 to which the pipes l4 and I8 respectively are connected. Communication between the two ports is regulated by valve 24 having a stem 32 screw threaded at 26 to mate with a corresponding screw thread 28 in the frame 30, so that rotation of the valve stem 32 in one or the other direction moves valve 24 toward or away from its seat 36. I have shown the seat sharp edged asis preferred for precision in regulation of the amount of refrigerant passed from the condenser into the evaporator. To open and close the valve, its stem carries fixedto it a pinion 38 meshing with gear 40 which, in turn, meshes with pinion 42 on a countershaft 44 of motor 46. Speed reduction gears, not shown, within the motor casing connect the armature shaft of the motor with the shaft 44 so that when the motor is connected to a suitable source of power, shaft 44 rotates very slowly, such as at two revolutions per hour. With shaft 44 rotating that slowly there need be no substantial reduction in gears 42, 40 and 38. The pitch of threads 26 and 28 is low and as a, resultof the slow rotation of the stem, the valve moves very slowly toward its open or closed positionswhen motor 46 is operated. j

The motor 46 is reversible and in the embodiment shown I employ a direct current circuit leading to the three binding posts 50, 52 and 54. With one direct current lead closed to the post 52, the motor will rotate in a direction to close the valve if the other direct current lead is closed to post 56 and will be rotated in a direction to open the valve if that other lead is closed to p st 54.

The direct current power source is indicated by leads 60 and 62 (Fig. 1). When switch 64 is closed lead 60 is connected through variable resistance 66 (adapted to regulate the speed of the motor in an obvious manner) to the central binding post 52. Lead 62 is connected through line 68 to contact lever 10 adapted to close circuit selectively to lines I2, 14 and I6. The switches and 82 are limit switches to be described that are normally closed and, accordingly, when switch 10 completes circuit to line 12 the valve will open very slowly. When switch 10 is closed to line 16 the valve will rotate very slowly toward its closed position. When switch 10 contacts neither line 12 nor 16, but closes circuit to line 14, the opening and closing of the valve is automatically effected in the following manner, re-- sponsive to fluctuations in relative conditions of pressure and temperature within the suction header 6. Y

indicates a small tube communicating at one end with the suction header 6 and its other end with a pressure responsive instrument 92 having an element 94 which moves to the right,

as viewed in Fig. 1 when the pressure in the header 6 increases and to the left when it decreases. Within the suction header 6 is a temperature responsive instrument such as a there mometer 96, connected by tube 98 with a temperature responsive instrument I having an element I04 pivoted at I03 and moved to the right when the temperature in the header 6 rises and to the left when it falls. Also mounted on pivot I03 of the temperature responsive instrument I00 is a lever I02 connected by link I to element 94. Lever I02 is freely mounted on the pivot I03 and by the link connection I05 is moved to the right or left upon a corresponding movement of the pressure indicating element 94 when the pressure in the header increases or decreases respectively,

Element I04 carries contact I06 adapted to close an electric circuit with contact I08 carried by the lever I 02 when the relative positions of elements 94 and I 04 are such that the contacts abut each other. Element I04 also carries contact IIO adapted to close circuit with contact II2 fixed to lever I02 when the relative positions 'of the elements make those contacts abut each other. Element I04 is connected to the line I4.

Element I04 and lever I02 are electrically insulated from each other. The line I6 is connected to terminal I08 and line I2 is connected to terminal II 2.

With the device constructed as above described, it will be apparent that if switch I0 isclosed to line I4, thereby energizing temperature indicating element I04, a relative movement either of pressure indicating element 94 or temperature indicating element I 04 such that contact is made from IIO to contact I I2, circuit will be completed through line I2 to terminal 54 of motor 46, thus rotating the valve stem in a direction to open the valve. On the other hand, if the relative positions of pressure indicating element 94 and temperature indicating element I04 are such that contact is made from I06 to I08, circuit will be completed to terminal 50 of motor 46 moving the valve toward closed position. The limit switches 80 and 82 are provided to insure automatically against such continued actuation of motor 46 as would force the valve 24 beyond its extreme open or closed positions. As will be seen from Fig. 2, the pinion 38 not only rotates in either direction but moves to the right or to the left as the valve is opened or closed and the gear 40 is elongated to accommodate such movement. The pinion 38 carries a pin having a portion Ia projecting rearwardly and a portion I20b projecting in front of the pinion. The gear rotates clockwise to close the valve during which the pinion advances toward the frame member I22. portion I20a as the valve nears its closed position is the rotatably mounted lever I24, to which is secured switch arm 80 spring pressed at I against the terminals 80a and 80b. Thus, the circuit is automatically opened in the lead to binding post before the valve is injured. Similarly, the pin portion I20b engages the lever I25 spring pressed at I28 against terminals 82a and 82b to open circuit to the binding post 54 as the valve-arrives at its extreme open position. Limit switches of this character are well known and need not be further described.

By suitably constructing lever I02 and spacing its contacts from the corresponding contacts on temperature indicating element I04 I can effect automatic movement of the valve toward its open or closed position upon substantially any desired predetermined relative conditions of temperature and pressure at whatever point the pressure and temperature are taken, in this in- Projecting into the path of pin 1 stance at the outlet header 6. In practice, I have found that maximum efficiency of the system is attained by maintaining the refrigerant which reaches the suction header 6 at between 1 F. and 2 F. superheat since thereby I insure maximum refrigerating effect within the evaporator, optimum conditions of heat interchange between evaporator 4 and the medium to be cooled which surrounds it and maximum eificiency of the compressor. To obtain this 1 F. limit variation of control I so space the contacts I08 and H2 from their corresponding contacts I06 and H0 that a relative movement equivalent to 1 F. between element I04 and lever I 02 commencing with either circuit being made will cause that circuit to be broken and the other to be made. I then adjust the position of lever I02 with reference to temperature indicating element I04 so that that 1 F. variation conforms to the range between 1 F. and 2 F. superheat for Whatever pressure is registered by the element 64. Specifically, if carbon dioxide is employed as the refrigerant and a temperature of 33 F. is assumed to be the saturation temperature for a pressure of 500 lbs. per square inch, I so position the parts in an obvious manner that relative to a pressure reading of that value on meter 92 contact is made across terminals I06 and I08 to operate the valve toward its closed position when a temperature of 34 F. is reached, and contact is made between points H0 and M2 to operate the valve toward its open position when a temperature of 35 F. is reached. Obviously, this same relationship will be maintained for the corresponding superheat temperatures when the pressure varies from 500 lbs. per square inch.

It will be observed that after a change has been made in the position of valve I6, the effect of that change on the refrigerant in the coil is not felt by the temperature and pressure responsive apparatus until the refrigerant reaches the suction header 6. It is partly to guard against the possibility of over regulation under those conditions that I provide for extremely slow movement of the valve by the motor 46 and in practice I have found that over regulation is entirely obviated thereby. i

It will thus be apparent that the apparatus above described so automatically effects opening and closing of the valve I6 that the size of valve opening is varied to meet precisely the loaddemand on the evaporatorfor all changes in pressure and temperature within it. My system insures maintenance of that size valve opening which will produce a predeterminedsuperheat under any changes in capacity of the system, whether resulting from differences in refrigerating load imposed by the medium to be cooled which surrounds the evaporator or from changes in the speed of the compressor. Unlike prior automatic expansion valves which are operated. by the pressure difference between a thermostatic pressure on one side of a movable diaphragm and an actual pressure on the other side, my apparatus insures the necessary variations in size of the valve opening for the same amount of superheat at different pressures'and temperatures Within the evaporator and thus is particularly effective to maintain maximum efficiency when the capacity of the system is in any way varied. Further-more, my system effects this sensitivity of controleven with gases, which like carbon dioxide have low criticaltemperatures' and thereby may in commercial operation be presented to the expansion valve either as a liquid or as, a gas, or

-ing from the principle of my invention. Thus,

although my invention .fills a need which has not heretofore been supplied for automatic expansion valve regulation for use with carbon dioxide refrigerant, its use is, of course, not limited thereto. Nor are the specific temperatures above recited in any way essential as others may be required under different conditions of operation. Although the temperature and pressure connections are preferably located within the suction header, this is not essential as they can be located elsewhere. I prefer,'however,to dispose both connections in the same .part of the system. 'The direct current motor described as my preferred source of power for moving the valve may, of course, be replaced by any motivator whether electric, pneumatic, hydraulic or mechanical, as is desired. It is contemplated that the contacts I08 and H2 be adjustably mounted on the lever I02 so that the spacing between them, representing the latitude of relative positions of lever I02 and member I04 throughout which neither circuit is closed to the valve'motor, may-be varied at will and that the length of connecting link I05 may be made adjustable. All such adjustable constructions are within the scope of my invention, although it is obviously unnecessary to illustrate them in detail in the drawings.

I claim:

1. A refrigerating system adapted to operate at a substantially constant superheat throughout a range of temperatures in the system, comprising a compressor, condenser and evaporator connected in circuit, an expansion valve admitting refrigerant to the evaporator, and means for operating the valve to maintain said superheat, said means comprising an element moved by changes in pressure in the system, a second element moved by changes in temperature in the system and independently of the movement of the first element, and means responsive to a predetermined relative positioning of said elements to move the valve toward its open position and responsive to a second predetermined relative positioning of said elements to move the valve toward its closed position.

2. A refrigerating system adapted to operate at a substantially constant superheat throughout a range of temperatures in the system, comprising a compressor, condenser and evaporator connected in circuit, an expansion valve admitting refrigerant to the evaporator, and means for operating the valve to maintain said superheat, said means comprising an element moved by changes in pressure in the system, a second element moved by changes in temperature in the system and independently of the movement of the first element, means responsive to a predetermined relative positioning of said elements to move the valve toward its open position and means responsive to a second predetermined relative positioning of said elements to move the valve toward its closed position, the said elements having a third predetermined relative positioning intermediate said first and. second relative positionings, corresponding to the desired superheat, at which the valve remains stationary.

3. A refrigerating .system comprising a compressor, condenser and evaporator connected in circuit, an expansion valve admitting refrigerant to the evaporator, and means for operating the valve to maintain in the system a predetermined range of superheat, said means comprising an element .moved by changes in pressure in the system, a second element moved by changes in temperature in the system and. independently of the movement of the first element, means responsive to a predetermined relative positioning of said elements to move the valve toward its open position and means responsive to a second predetermined relative positioning of said elements to move the valve toward its closed position, the said elements having a predetermined range of'relative positionings intermediate said first and second relative positionings, corresponding to a range of superheat, at which the size of the aperture remains unchanged, and means for changing saidrange of relative positionings to vary the range of superheat.

4. A refrigerating system adapted to operate at a substantially constant superheat throughout a range of temperatures in the system, comprising a compressor, condenser and evaporator connected in circuit, an expansion valve admitting refrigerant to the evaporator, and means for operating the valve to maintain said superheat, said means comprising an element moved by changes in pressure in thesystem, a second element moved by changes in temperature in the system and independently of the movement of the first element, one of said elements having two members movable with the rest of the element as a unit and disposed in spaced relation relative to each other, the other of said elements constituting a single member movable through the space separating said spaced members and adapted to engage said members at opposite limits of its said movement, means for moving the valve toward its open position when said single member engages one of said spaced members and means for moving the valve toward its closed position when said single member engages the other of said spaced members, said valve remaining stationary when said single member is not in engagement with either of said spaced members.

5. A refrigerating system adapted to operate at a substantially constant superheat throughout a range of temperatures in the system, comprising a compressor, condenser and evaporator connected in circuit, an expansion valve having an aperture through which refrigerant is admitted to the evaporator, and means for operating the valve to maintain said superheat, said means comprising an element moved by changes in pressure at a predetermined point in the system, a second element moved by changes in temperature at substantially the same predetermined point in the system and independently of the movement of the first element, power operated means for varying the size of said aperture by moving the valve selectively toward its open or closed positions, means responsive to one predetermined relative positioning of said elements to actuate the power operated means for moving the valve toward its open position and means responsive to a second predetermined relative positioning of said elements to actuate the power operated means for moving the valve toward its closed position, the said power operated means being adapted, when actuated, to move the valve so slowly that the effect of a slight change in aperture size is felt at said predetermined point before any substantial change in aperture size is made.

6. A refrigerating system adapted to operate at a substantially constant superheat through-I out a range of temperatures in the system, comprising a compressor, condenser and evaporator connected in circuit, an expansion valve admitting refrigerant to the evaporator, and means for operating the valve to maintain said superheat, said means comprising an element moved through predetermined distance increments in response to predetermined changes in temperature at a given location within the system, a second element moved through the same increments in response to the same predetermined changes in saturation temperature corresponding to changes in pressure at said location and independently of the movement of said first element, means responsive to a predetermined relative positioning of said elements to move the valve toward closed position to prevent decrease below said superheat, and means responsive to a second predetermined relative positioning of said elements to move the valve toward open position to prevent increase above said superheat.

7. In a superheat control for an expansion valve, the combination of means for power operating said valve, independently movable pressure and temperature responsive elements controlling said valve operating means, means for subjecting the said elements respectively to pressure and temperature conditions prevailing at substantially the same point in a system to cause said operating means to move the valve toward open position at the upper limit of a predetermined range of superheat and toward closed position at the lower limit of said range.

8. In a superheat control for an expansion valve, the combination of an electric motor driving the valve and having one circuit for moving the valve toward open position and a second circuit for moving the valve toward closed position, a switch in said valve opening circuit, a switch in said valve closing circuit, independently movable pressure and temperature responsive elements controlling said switches, means for subjecting the said elements respectively to pressure and temperature conditions prevailing at substantially the same point in a system to close said switch in said valve opening circuit at the upper limit of a predetermined range of superheat and to close said switch in said valve closing circuit at the lower limit of said range.

9. In a superheat control for an expansion valve, the combination of an element adapted to be moved through predetermined space increments in accordance with predetermined changes in temperature within a system, a second element adapted to be moved through the same predetermined space increments by the same predetermined changes in saturation temperature corresponding to changes in pressure within the system, means for moving the valve toward open position when said elements are disposed in a predetermined relative position, and means for moving the valve toward closed position when said elements are disposed in a second predetermined relative position.

10. In a superheat control for an expansion valve, the combination which includes a pair of members engageable to move the valve toward open position at the upper limit of a superheat range, a pair of members engageable to move the valve toward closed position at the lower limit of said range and apparatus for maintaining said range fixed for different pressures and temperatures at a predetermined location within a system comprising means for moving one member of each pair through predetermined distance increments in response to predetermined changes in temperature at said location and means for moving the other member of each pair through the same increments in response to the same changes in saturation temperature corresponding to changes in pressure at said location and independently of the movement of the first mentioned member in each pair.

HECTOR HARRIS ROBSON.

Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4333317 *Aug 4, 1980Jun 8, 1982General Electric CompanySuperheat controller
US4461156 *Nov 30, 1981Jul 24, 1984Morton WeintraubSystem for conditioning an area
US4571951 *Dec 14, 1984Feb 25, 1986Vilter Manufacturing CorporationElectronic control for expansion valve in refrigeration system
US7143595Jan 6, 2005Dec 5, 2006Sanyo Electric Co., Ltd.Supercritical refrigerant cycle system
US20050150240 *Jan 6, 2005Jul 14, 2005Sanyo Electric Co., Ltd.Supercritical refrigerant cycle system
EP0138094A2 *Sep 20, 1984Apr 24, 1985Asea Brown Boveri AktiengesellschaftRefrigerator
EP0147357A2 *Dec 14, 1984Jul 3, 1985Carrier CorporationRefrigeration system and incrementally adjustable electronic expansion valve
EP1369648A2 *May 21, 2003Dec 10, 2003Sanyo Electric Co., Ltd.Supercritical refrigerant cycle system
Classifications
U.S. Classification62/212
International ClassificationF25B41/06, F25B9/00
Cooperative ClassificationF25B2309/061, F25B41/062, F25B2341/0653, Y02B30/72, F25B9/008
European ClassificationF25B41/06B