US3643459A

US3643459A - Timer-controlled refrigeration system

Info

Publication number: US3643459A
Application number: US23913A
Authority: US
Inventors: Alan A Matthies
Original assignee: Controls Company of America
Current assignee: Eaton Corp
Priority date: 1970-03-30
Filing date: 1970-03-30
Publication date: 1972-02-22
Anticipated expiration: 1989-02-22

Abstract

An expansion valve in a refrigeration system has an electrically energized operator assembly which controls the operative state of the valve on the basis of the electrical input to the operator assembly. The electrical input to the operator assembly is timer controlled and the system is taken through a preselected refrigeration cycle under control of the timer.

Description

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[54] TlMER-UDNTROLLEB 3,324,674 6/1967 Finnegan ..62/223 REFRHQERATHUN gYSTEM 2,095,834 10/1937 Rodman ..62/ I57 [72] Inventor: Alan A. Matthias, Milwaukee, Wis. Primary Examiner-Meyer Perlin Attorney-John W. Michael, Gerrit 1D. Foster, Bayard H. [73] Asslgnee' E232 Campmy M Ammw Melrose Michael, Paul R. Puerner, Joseph A. Gemignani, Andrew 0.

Riteris, Daniel Van Dyke and Spencer B. Michael [22] Filed: r. 30, 1970 57 r WSTRACT [21] Appl. No.: 23,9l3 1 An expansion valve in a refrigeration system has an electrically energized operator assembly which controls the opera- [52] US. Cl ..62/ 157, 62/223, 62/231 fi t t f th valv 011 the basis of the electrical input to the [51] lnLCl ..F25b41/04i operator a embly. The electrical input to the operator as- [58] Field of Search ..62/157, 158, 231, 222, 223 sembly is timer controlled and the system is taken through a preselected refrigeration cycle under control of the timer. [56] References Cited 8 Claims, 11 Drawing Figure UNITED STATES PATENTS I 3,537,272 11/1970 Hales ..62/l57 l 1 W J0 1% 71/\?O M /@e @z a Z fl APoe/rroe, z Z2 Canoe/wa e,

TIlMlEIlt-CONTRULLED lltlllll ttlGlElltA'llllON SYSTEM This invention relates to refrigeration systems and, more particularly, to such systems as include electrically energized expansion valves.

Expansion valves are generally controlled on the basis of a sensed system condition, for example pressure within the system, temperature, or sensing presence of liquid refrigerant in the system.

it has been observed that some refrigeration installations exhibit predictable operating characteristics. That is, the amount of heat loss and/or the requisite pull down to reach a particular operation level can be predicted and, correspondingly the refrigerant flow in the system necessary to fulfill these requirements can be predicted.

In accordance with this invention, this observation and electrically energized expansion valves are combined to achieve an effective and simplified refrigeration system which will provide efficient operation in these predictable environments.

Accordingly, among the genera] objects of this invention are to provide a simplified and effective refrigeration system the operation of which is controlled on the basis of the predictable characteristics of the installations.

For the achievement of these and other objects, a refrigeration system is provided with an electrically energized expan sion valve and the energization of the valve is controlled by a timer mechanism. The timer mechanism is programmed to modulate the valve to supply refrigerant in accordance with the predictable demand on the system. For example, in an environment where the system requires a prescribed pull down to achieve a holding temperature and the holding temperature can then be held by maintaining a relatively constant flow of refrigerant, the timer is programmed to meet these particular demands on the system. This type of arrangement provides, in a relatively simple manner, satisfactory refrigeration system operation.

Other objects and advantages will be pointed out in, or be apparent from, the specification and claims, as will be obvious modifications of the embodiment shown in the drawing, which is a generally schematic illustration of a system in accordance with this invention.

With particular reference to the drawing, a refrigeration system includes evaporator it), condenser 1l2, compressor M, expansion valve l6, and suitable conduit connecting these elements to form a closed refrigeration system. The system is generally conventional and hence will not be described in any further detail.

Expansion valve 16 includes body llli having an internal flow passage communicating with the system conduit. The in ternal flow passage includes inlet 20, outlet 22, and restricted orifice 2d between the inlet and outlet. A needle valve as is supported in a bore 23 and is free to move relative to orifice 24 for controlling the volume of refrigerant flow through the expansion valve to evaporator ill.

The expansion valve includes an electrically energized operator assembly contained in upper portion fill of the valve body. Structurally, the operator assembly includes a temperature sensitive member, a bimetal 32, connected to needle valve 26. An electric heater M is positioned in heat transfer relationship with the bimetal. The heater-bimetal arrangement is illustrated schematically and, for example, the heater may be wrapped on the bimetal. but electrically insulated from the bimetal while still being in heat transfer relationship therewith. The combination heater and bimetal are disposed in chamber as in valve body portion 36'. A suitable sealing arrangement (not shown) can be provided between the needle valve and the bore walls to isolate chamber 36 from refrigerant flow so that the operator assembly is not affected by the refrigerant.

With this type of electric expansion valve, the position of needle valve 26 relative to orifice 2-3 is determined by the condition or position of bimetal 32. Only a general description of the operator assembly is necessary to an understanding of the invention and for that reason it will not be described in detail. The bimetal will assume a normal position when cold, for example holding the needle valve closed on orifice 2d, but by energizing heater 341 can be made to bow and move needle valve 26 away from orifice 24 to open the expansion valve to flow. By varying the amount of current in heater 2 1 the operative state of the bimetal and correspondingly the position of the needle valve relative to the orifice can be varied precisely. it will be appreciated that the bimetal is mounted in chamber as in a suitable manner and used with a spring, if necessary, to bias the bimetal and valve toward or away from the cold position.

It has been proposed that valves of this type be controlled on the basis of some sensed condition within the refrigeration system, for example temperature, pressure, or the presence of refrigerant in a liquid state in the flowing refrigerant. An example of one type of such controls can be found in US. Pat. No. 3,478,534, of Alan A. lvlatthies assigned to the assignee of this application. in these types of prior control, it was generally assumed that the sensed condition was indicative of the load or demand on the system and hence was an accurate and reliable control parameter. For many applications these types of control are adequate but they do in some instances result in an undesirable hunt characteristic. The arrangement disclosed in the above-identified patent, however, does have the advantage of generally minimizing this hunt characteristic. The hunt characteristic is introduced into the control system where a sensed condition is being used as the control parame ter because of the necessity to sense the particular condition and then to translate that condition into an operable signal which can be used to vary the valve setting. This also requires continual sensing of the system condition to tell the valve when the necessary condition has been met. With these types of arrangements there is a tendency for the system to hover about the desired point by either overshooting or undershooting that point before it ultimately settles on the desired point, this is the hunt characteristic.

in many refrigeration applications it has been observed that in a particular environment the system will experience a pre dictable amount of heat loss when being held at a constant or desired temperature level (holding temperature); and, furthermore, that a predictable amount of heat energy must he removed by the system to bring the system down to the holding temperature. An example of such an application is a refrigerated storage room or cooler. The cooler must be brought down to a given holding temperature and the amount of heat to be removed can be readily predicted and calculated. Once at the holding temperature, the cooler will experience a predictable amount of heat loss in a given environment. The cooler may be periodically defrosted but the above pulldown and holding cycles will always be repeated. Other examples of applications of this type are refrigerated trucks or railroad cars, food display cases, and ice cube makers.

Having observed these predictable operating characteristics in certain types of refrigeration installations, it was further discovered that the input to the electrically energized operator for an expansion valve, such as valve to, can be controlled in a manner to meet the predictable system demand. The refrigeration system can thus be made to operate without control on the basis of any sensed internal or external system condition. With this end in mind, the input to heater M is controlled through a variable impedance 38 which is in turn controlled by a suitable timer W. In addition to the timer and impedance 38, the control circuit for heater 34 also includes the secondary 42 of a transformer M connected to a suitable AC input 416. By varying the position of slider id on impedance 50, the current in heater 341 can be varied.

The details of construction of timer it)? and its connection to slider 4i} are not necessary to a complete understanding of this invention and, accordingly, the timer and its connection have been shown in a generally schematic manner. As schematically illustrated, timer ill includes a screw 52 driven by a timer motor 5 2i. Screw 52 has a threaded engagement with slider td and, when the screw is rotated by timer motor 5d, slider db moves either to the right or the left relative to impedance 50 to thereby vary the value of the impedance in the control circuit for heater 34. Timer motor 54 is connected to a suitable timer input 56,

in a typical refrigeration installation and assuming a pulldown to a holding temperature and subsequent maintenance of the system in a condition to maintain that holding temperature, heater 34 is activated to bow bimetal 32 and open valve 16 to flow. Timer 40 can be programmed to position slider 48 so as to activate heater 34 sufficiently to open the valve the amount necessary to pulldown to the holding temperature in a particular given time. At this point it should be noted that in some installations the demand for cooling during the pulldown cycle may be decreased as the system approaches the holding temperature. In that type of installation the timer can be further programmed to modulate the valve toward a closed position in accordance with this decreasing demand as the system approaches the holding temperature. This is accomplished by moving slider 48 relative to impedance 50 to decrease the current in or input to heater 34 in accordance with the decrease in system demand. When the desired holding temperature is reached, the amount of heat loss which the installation will experience in a given ambient can be pre dicted and the timer programmed to set needle valve 26 at that position which will provide sufficient refrigerant flow to meet that heat loss. Again, the needle valve is positioned by locating slider 48 on impedance 50 at that point which establishes the energization of heater 34 necessary to provide the required holding position of needle valve 26 relative to orifice 24. It is also possible to program the timer to meet a varying demand during the holding cycle.

This arrangement provides effective system operation and with a simplified control arrangement. Furthermore, since the control does not depend on sensing a system condition, the control and system do not experience any hunt.

Although but one embodiment of the present invention has 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.

Iclaim:

l. A refrigeration system having a preselected refrigeration cycle and comprising in combination,

an evaporator,

an expansion valve controlling flow of refrigerant to said evaporator, said expansion valve including an electrically energized operator assembly controlling the operative state of said valve to thereby modulate said valve and vary refrigerant flow therethrough,

means defining an electrical control circuit connected to and controlling the operative state of said operator assembly,

and timer means connected in said control circuit and being the sole control for said operator assembly, said timer means controlling the electrical input to said operator assembly and being operative to produce manipulation of said expansion valve to achieve said preselected operational cycle so that said refrigeration system is operated through said preselected refrigeration cycle under the sole control of said timer means.

2. A refrigeration installation having a holding cycle during which said installation exhibits predictable heat loss and having a predictable pulldown cycle to arrive at said holding cycle, said system including an evaporator,

an expansion valve connected to and controlling fiow of refrigerant to said evaporator,

an operator assembly operative on the basis of an electrical input and connected to and controlling the operative state of said valve to modulate said valve and refrigerant flow therethrough,

means defining an electrical control circuit connected to said operator assembly and providing the electrical input thereto,

and timer means connected in said control circuit and being the sole control for said operator assembly, said timer means operative to control the electrical input to said operator assembly to manipulate said valve to provide said pulldown and holding cycles.

3. A refrigeration system having a preselected refrigeration cycle and comprising in combination,

an evaporator,

said operator assembly including a temperature responsive member and an electrical heater in heat transfer relation with said temperature responsive member,

said control circuit including variable circuit means in circuit with and operable upon adjustment thereof to vary the electrical input to said heater,

and timer means connected to and controlling said variable circuit means to control the electrical input to said operator assembly, said timer means operative to produce manipulation of said expansion valve to achieve said preselected operational cycle so that said refrigeration system is operated through said preselected refrigeration cycle under the control of said timer means.

4. A refrigeration system having a preselected refrigeration cycle and comprising in combination,

an evaporator,

and timer means connected in said control circuit and controlling the electrical input to said operator assembly, said timer means operative to produce manipulation of said expansion valve to achieve said preselected operational cycle so that said refrigeration system is operated through said preselected refrigeration cycle under the control of said timer means,

said timer means being operative to vary the input to said operator assembly during a pulldown portion of said cycle to modulate said valve to gradually reduce flow of refrigerant through said valve and to maintain a valve position for a holding portion of said cycle to maintain a preselected generally constant condition of said refrigerant system.

5. The system of claim 4 wherein said operator assembly includes a temperature responsive member and an electrical heater in heat transfer relation with said temperature responsive member,

said control circuit includes variable circuit means in circuit with and operable upon adjustment thereof to vary the electrical input to said heater,

and said timer means connected to and controlling said variable circuit means.

6. The system of claim 5 wherein said circuit means comprises a variable resistance.

7 A refrigeration installation having a holding cycle during which said installation exhibits predictable heat loss and having a predictable pulldown cycle to arrive at said holding cycle, said system including an evaporator,

an expansion valve connected to and controlling flow of refrigerant to said evaporator,

un 1A an operator assembly operative on the basis of an electrical input and connected to and controlling the operative state of said valve to modulate said valve and refrigerant flow therethrough,

and timer means connected in said control circuit and operative to control the electrical input to said operator assembly to manipulate said valve to provide said pulldown and holding cycles, said timer means modulating said valve to gradually reduce the refrigerant flow at a preselected rate during said pulldown cycle as said installation progresses through said pulldown cycle toward said

Claims

1. A refrigeration system having a preselected refrigeration cycle and comprising in combination, an evaporator, an expansion valve controlling flow of refrigerant to said evaporator, said expansion valve including an electrically eneRgized operator assembly controlling the operative state of said valve to thereby modulate said valve and vary refrigerant flow therethrough, means defining an electrical control circuit connected to and controlling the operative state of said operator assembly, and timer means connected in said control circuit and being the sole control for said operator assembly, said timer means controlling the electrical input to said operator assembly and being operative to produce manipulation of said expansion valve to achieve said preselected operational cycle so that said refrigeration system is operated through said preselected refrigeration cycle under the sole control of said timer means.

2. A refrigeration installation having a holding cycle during which said installation exhibits predictable heat loss and having a predictable pulldown cycle to arrive at said holding cycle, said system including an evaporator, an expansion valve connected to and controlling flow of refrigerant to said evaporator, an operator assembly operative on the basis of an electrical input and connected to and controlling the operative state of said valve to modulate said valve and refrigerant flow therethrough, means defining an electrical control circuit connected to said operator assembly and providing the electrical input thereto, and timer means connected in said control circuit and being the sole control for said operator assembly, said timer means operative to control the electrical input to said operator assembly to manipulate said valve to provide said pulldown and holding cycles.

3. A refrigeration system having a preselected refrigeration cycle and comprising in combination, an evaporator, an expansion valve controlling flow of refrigerant to said evaporator, said expansion valve including an electrically energized operator assembly controlling the operative state of said valve to thereby modulate said valve and vary refrigerant flow therethrough, said operator assembly including a temperature responsive member and an electrical heater in heat transfer relation with said temperature responsive member, means defining an electrical control circuit connected to and controlling the operative state of said operator assembly, said control circuit including variable circuit means in circuit with and operable upon adjustment thereof to vary the electrical input to said heater, and timer means connected to and controlling said variable circuit means to control the electrical input to said operator assembly, said timer means operative to produce manipulation of said expansion valve to achieve said preselected operational cycle so that said refrigeration system is operated through said preselected refrigeration cycle under the control of said timer means.

4. A refrigeration system having a preselected refrigeration cycle and comprising in combination, an evaporator, an expansion valve controlling flow of refrigerant to said evaporator, said expansion valve including an electrically energized operator assembly controlling the operative state of said valve to thereby modulate said valve and vary refrigerant flow therethrough, means defining an electrical control circuit connected to and controlling the operative state of said operator assembly, and timer means connected in said control circuit and controlling the electrical input to said operator assembly, said timer means operative to produce manipulation of said expansion valve to achieve said preselected operational cycle so that said refrigeration system is operated through said preselected refrigeration cycle under the control of said timer means, said timer means being operative to vary the input to said operator assembly during a pulldown portion of said cycle to modulate said valve to gradually reduce flow of refrigerant through said valve and to maintain a valve position for a holding portion of said cycle to maintain a preselected generally constant coNdition of said refrigerant system.

5. The system of claim 4 wherein said operator assembly includes a temperature responsive member and an electrical heater in heat transfer relation with said temperature responsive member, said control circuit includes variable circuit means in circuit with and operable upon adjustment thereof to vary the electrical input to said heater, and said timer means connected to and controlling said variable circuit means.

7. A refrigeration installation having a holding cycle during which said installation exhibits predictable heat loss and having a predictable pulldown cycle to arrive at said holding cycle, said system including an evaporator, an expansion valve connected to and controlling flow of refrigerant to said evaporator, an operator assembly operative on the basis of an electrical input and connected to and controlling the operative state of said valve to modulate said valve and refrigerant flow therethrough, means defining an electrical control circuit connected to said operator assembly and providing the electrical input thereto, and timer means connected in said control circuit and operative to control the electrical input to said operator assembly to manipulate said valve to provide said pulldown and holding cycles, said timer means modulating said valve to gradually reduce the refrigerant flow at a preselected rate during said pulldown cycle as said installation progresses through said pulldown cycle toward said holding cycle and maintaining, during said holding cycle, a relatively constant operative state of said valve and constant flow through said valve at a preselected rate corresponding to said heat loss.

8. The system of claim 7 wherein said operator assembly includes a temperature responsive member and an electrical heater in heat transfer relation with said temperature responsive member, said control circuit includes variable circuit means in circuit with and operable upon adjustment thereof to vary the electrical input to said heater, and said timer means connected to and controlling said variable circuit means.