Refrigeration Fan Control System

Abstract

A control for a refrigeration system including a compressor, a condensor, an evaporator and an electrically energized fan for passing air in heat exchange relation with respect to the compressor, the control including a light source, fan control means responsive to the light source for varying the operating speed of the fan, and means for varying the magnitude of light transmitted to the fan control means from the light source in response to the refrigerant pressure in the refrigeration system.

Parent Case Text

RELATED APPLICATIONS

This is a continuation-in-part application of Ser. No. 349,023, filed Apr. 9, 1973.

Description

BACKGROUND OF THE INVENTION

In refrigeration systems employing a refrigerant compressor, it is desirable to obtain the maximum desired operating head pressure of the compressor as soon as possible after the system is energized and to maintain this head pressure throughout the freezing cycle. In air cooled condensing units, especially under low ambient temperature operating conditions, it is possible that the desired head pressure may never be obtained unless some provision is made to control the condensor fan speed. As will be appreciated by those skilled in the art, the head pressure in such refrigeration systems is directly proportional to the refrigerant discharge temperature, and accordingly, it has been proposed to utilize a pressure switch which delays energization of the condenser fan until the proper compressor head pressure is obtained; however, this results in erratic operation of the fan from full "on" to "off" and further results in large fluctuations in the head pressure. Additionally, such pressure switches result in the condenser fan operating at full r.p.m. when such full operating speed is not required. Alternatively, it has been proposed to utilize an electronic phase control device for operating the compressor fan. Such controls obtain the desired fan speed by an external variable resistor. In some such systems, a thermister is used to vary the resistance to the phase control, although this approach has been found to be objectionable due to the slow response to changes in compressor head pressure due to the insufficient conductance of temperature changes to the thermister. This results in high peaks in the compressor head pressure at the initiation of a freezing cycle, with an additional disadvantage being that the thermister senses high ambient temperatures which cause the condenser fan to operate too fast on start-ups.

Another approach to obtaining maximum operating head pressure of refrigerator compressors is to use a pressure bellows to operate a potentiometer that gives improved control of the fan through the phase control. Disadvantages of the use of such bellows reside in the fact that they frequently involve cumbersome and costly operating mechanisms that require critical adjustments due to the short travel of the pressure bellows operating the associated potentiometers.

In accordance with the principles of the present invention, a new and improved fan control is provided which overcomes the various objectionable characteristics of similar type devices heretofore proposed in the prior art. The fan control of the present invention utilizes a light source that may be in the form of a small neon lamp and which is cooperative with a photoelectric cell located in the electrical circuitry of the condenser fan motor. The cell operates to provide a variable resistance which increases or decreases with the amount of light supplied by the neon lamp that is transmitted to the cell. For example, when a maximum amount of light is transmitted to the cell, the resistance provided thereby may be quite low, for example, in the order of 600-1,000 ohms, whereas when the magnitude of the light is predeterminately decreased, the resistance provided by the cell may be in the order of 100,000 ohms. The method of varying the magnitude of the light transmitted from the neon lamp to the photoelectric cell, and thus changing the resistance through the cell in relation to the discharge pressure of the refrigerator compressor, is accomplished by interposing a light masking element between the light source and the photoelectric cell. More particularly, the light masking element is mounted on the shaft of a Bourdon tube that is connected to the discharge end of the compressor, with the result that as the pressure increases, the light masking element is moved in a predetermined manner so as to expose a greater amount of light from the light source to the photoelectric cell, and vice versa. The photoelectric cell is used in conjunction with an electronic phase control for regulating the fan speed, with the phase control operating in a conventional manner in rapidly switching "off" and "on" the AC current supplied to the fan motor by cutting off a fraction of the AC cycle. As will hereinafter be described in detail, it is desirable that the head pressure of the refrigeration system be in the order of 150 psi. Accordingly, under low ambient temperature operating conditions, the fan control maintains the fan motor deenergized until the head pressure has increased to approximately 100 psi. At this point, the fan will operate at a very slow speed and the operating speed will gradually increase as the head pressure increases. At approximately 150 psi, the control operates the fan at full r.p.m. and this operating condition will continue until the head pressure begins to drop, at which time the fan speed will decrease accordingly.

SUMMARY OF THE INVENTION

This invention relates generally to refrigeration systems, and more particularly, to a new and improved control for operating the condensor fan in a manner so as to obtain predetermined head pressure in the compressor.

It is accordingly a general object of the present invention to provide a new and improved fan control for refrigeration condensers.

It is a more particular object of the present invention to provide a new and improved fan control of the above-described character which includes a light source and a photoelectric element for varying the resistance supplied to the fan motor, and which further includes means for selectively controlling the magnitude of the light transmitted from the light source to the photoelectric cell in accordance with the discharge pressure of the compressor.

It is another object of the present invention to provide a new and improved fan control of the above-described type wherein the means for varying the magnitude of the light supplied to the photoelectric cell comprises a light masking element which is cooperable with a pressure responsive Bourdon tube.

It is still another object of the present invention to provide a new and improved fan control for use in refrigeration systems of the type which can be used in ice making equipment.

It is yet another object of the present invention to provide a new and improved fan control of the above-described type which is of a relatively simple construction, is economical to manufacture and which will have a long and effective operational life.

Other objects and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of the fan control of the present invention as shown in operative association with a typical refrigeration system;

FIG. 2 is a side elevational view of a portion of the fan control embodying the principles of the present invention;

FIG. 3 is an elevated perspective view of the fan control shown in FIG. 2;

FIG. 4 is an enlarged transverse cross-sectional view taken substantially along the line 4--4 of FIG. 2;

FIG. 5 ia an enlarged fragmentary view of a modified construction of the fan control of the present invention;

FIG. 6 is an enlarged transverse cross-sectional view of the portion of the fan control shown in FIG. 5; and

FIG. 7 is a front elevational view of the light masking element incorporated in the modified fan control shown in FIGS. 5 and 6.

DESCRIPTION OF A PREFERRED EMBODIMENT

Referring in detail now to the drawings and in particular to FIG. 1 thereof, a refrigeration system 10 is representatively illustrated as comprising a conventional compressor 12, condensor 14 and evaporator 16. As is customary in the art, the condenser 14 is provided with a cooling fan, generally designated by the numeral 18, which functions to selectively pass cooling air thereover during operation thereof. The fan 18 is shown as comprising an electrically energized motor 20, the operation of which is controlled by a fan control, generally designated by the numeral 22 and constructed in accordance with the principles of the present invention. Generally speaking, the fan control 22 is connected to the refrigeration system by means of a conduit 24 which is communicable with the discharge side of the compressor 12, and by means of electrical conductors 26, 28 which supply electrical energy to the fan motor 20. As will hereinafter be described in detail, the discharge pressure of the compressor 12 increases with the ambient temperature of the refrigeration system 10, and when the system 10 is operating under low ambient temperature conditions, such as below 70.degree.F., the discharge pressure of the compressor 12 is too low for efficient operation. The proper compressor head pressure is particularly important when the refrigeration system 10 is operatively associated with ice making machines, especially where the refrigerant gases are utilized to heat the defrost water that is employed during the harvest cycle of an ice making machine. Normally, in such ice making machines, a head pressure of approximately 150 psi is desirable. In high ambient temperature conditions, the pressure may increase in excess of 200 psi; however, in low ambients, the fan control 22 of the present invention will function to delay operation of the fan 18 until the head pressure has increased to approximately 100 psi. At this point, the fan 18 will operate at a very slow r.p.m. and gradually increase in speed as the head pressure of the compressor increases. At approximately 150 psi, the fan control 22 operates the fan at full r.p.m. and the fan 18 will continue to so operate until such time as the head pressure of the compressor 12 begins to decrease, at which time the fan speed will decrease proportionately to reduce the head pressure.

Referring now in detail to the construction of the fan control 22 of the present invention, as best seen in FIGS. 2-4, the fan control 22 is contained or enclosed within a generally rectangular-shaped housing 30, one side 32 of which is depicted in the drawings. The interior of the housing 32 is preferably of a dark color to avoid any light reflections, as will hereinafter be appreciated. The side 32 of the housing 30 is provided with a pair of mounting flanges 34 and 36 on the opposite ends thereof which are secured to the side 32 by means of suitable screws, bolts or the like 38. The flanges 34, 36 are adapted to cooperate with the remaining portion of the housing 30 (not shown) in operatively securing the side 32 thereto, as will be appreciated by those skilled in the art. The mounting flange 46 is formed with an aperture 40 within which a suitable grommet or the like 42 is provided, whereby to permit suitable electrical conductors to pass from the exterior of the housing 30 to the interior thereof, as is well known in the art. Generally speaking, the interior of the housing 30 contains a pressure sensing assembly 44, a phase control 46 and electrical terminal block 48, all of which components will hereinafter be described in detail.

Referring now in detail to the construction and operation of the pressure sensing assembly 44, the assembly 44 comprises a Bourdon tube, generally designated by the numeral 50, which is of a conventional, generally C-shaped configuration and is fabricated of a flattened metal tube which is closed at the outer end thereof. It is well known in the art, at such time as the pressure within the tube 50 increases, the same tends to move toward a straightened configuration and thereby provides a mechanical movement at the outer end thereof. The Bourdon tube 50 is operatively mounted within a suitable manifold block 52 which is communicable via a suitable fluid fitting 53 with the conduit 24 that communicates with the discharge side of the compressor 12, as previously mentioned. The end of the Bourdon tube opposite that which is secured to the manifold block 52 is connected via a suitable mechanical linkages 54 with a segmental gear 56 which is meshingly engaged with external teeth formed on a rotatable shaft 58. The mechanical linkages 54 and gear segment 56 operate such that upon an increase in pressure within the Bourdon tube 50 due to an increase in pressure on the discharge side of the compressor 12, the shaft 58 will be caused to rotate, for purposes to be hereinafter described. As shown in FIG. 4, the outer end of the shaft 58 is journal supported by suitable bearing means 60 operatively secured within a support plate or the like 62 attached to the inner side of the manifold block 52.

Disposed interiorly of the Bourdon tube 50 is a light source, generally designated by the numeral 64. The light source 64 perferably is in the form of a neon light 66 and is operatively mounted within a suitable support bracket 68 attached by suitable screws, bolts or the like 70 to the side 32 of the housing 30. The neon light 66 is connected via suitable electrical conductors 72, 74 with terminals 76 and 78 of the aforementioned terminal block 48, with suitable resistor means (not shown), such as a 1200 ohm resistor or the like, being provided in the electrical circuit to the neon light 66 so that the same may operate on a 115 volt source of electrical energy.

The light source 64 is cooperable with a light sensitive photoelectric device, herein referred to as a photoelectric cell and generally designated by the numeral 82. The photoelectric cell 82 may be of any one of a number of different types of constructions and may consist, for example, of a photoconductive detector, a phototube, a photovoltaic cell, a phototransistor or various other devices well known in the art which functions to change the resistance in an electrical circuit in accordance with the magnitude of exposure or degree of light transmitted thereto. Preferably the photoelectric cell 82 embodied in the present invention consists of a cadmium sulphide cell of a construction well known in the art. Due to the sensitivity of the photoelectric cell 82, it is preferable to maintain the interior of the housing 30 shielded from exterior light sources, as previously mentioned. The photoelectric cell 82 is operatively supported in a suitable carrier element, generally designated by the numeral 84, which is located adjacent and above the end of the shaft 58 which is rotatable by the Bourdon tube 50. The carrier element 84 is threadably mounted on a generally externally threaded shaft or screw element 86 which is in turn journal supported within a suitable internal bore formed in a mounting block 88 that is operatively secured to the side 32 of the housing 30. The upper end of the shaft 86 is formed with a screwdriver receiving slot 90 by which the shaft 86 may be rotated, with the result that the carrier element 84 and photoelectric cell 82 mounted thereon will move toward and away from the axis of the shaft 58 and hence toward and away from a position generally in aligned confronting relation with respect to the light source 64. Thus, the control 22 may be adjusted in accordance with the desired head pressure in the associated refrigeration system. One side of the carrier element 84 is formed with an elongated slot 92 which is adapted to be slidably engaged with an elongated guide member 94 having an upper, generally loop-shaped portion 96 that is adapted to be secured to the side 32 by means of a suitable screw, bolt or the like 98. As will be appreciated by those skilled in the art, the interengagement of the slot 92 with the guide member 94 prevents rotation of the element 84 and photoelectric cell 82 upon upward and downward movement thereof upon rotational adjustment of the shaft 86. The photoelectric cell 82 is mounted on the carrier 84 such that the light sensitive side thereof faces the light source 64, and the cell 82 is connected to the electric circuitry of the fan control 22 of the present invention by means of a pair of electrical conductors 100 and 102 which are respectively connected to terminals 104 and 106 of the terminal block 48.

In accordance with the present invention, interposed between the photoelectric cell 82 and the light source 64 is a light masking element, generally designated by the numeral 108. The element 108 consists of a generally disc-shaped member which may be fabricated of a light impervious material, such as metal or the like. The masking element 108 is formed with a central opening 110 which is provided with a suitable mounting hub or the like 112 adapted to operatively secure the element 108 on the end of the shaft 58. With this arrangement, upon rotation of the shaft 58 due to a pressure change within the Bourdon tube 50, the masking element 108 will rotate about the axis of the shaft 58. The radial dimension of the masking element 108 is such that the element is adapted to interrupt or block the transmission of light from the light source 64 to the photoelectric cell 82; however, the element 108 is formed with a control aperture, generally designated by the numeral 114, which is of a preselected configuration such that when the element 108 is selectively rotationally positioned, a predetermined magnitude of light will be transmitted from the light source 64 through the aperture 114 to the photoelectric cell 82. The shape or configuration of the control aperture 114 is such that when the internal pressure within the Bourdon tube 50 is relatively low, for example, in the order of approximately 150 psi, the aperture 114 is in complete registry with the line of light transmission from the light source 64 to the photoelectric cell 82. In this condition, the maximum amount of light is transmitted to the photoelectric cell 82 which results in a minimum or zero resistance being interjected thereby into the fan control circuit. As the pressure within the Bourdon tube 50 decreases, for example, to approximately 125 psi, resulting in a predetermined amount of rotation of the element 108, the configuration of the control aperture 114 therein is such that approximately 25 percent of the light transmission from the light source 64 to the photoelectric cell 82 is blocked. Similarly, when the pressure within the Bourdon tube 50 drops still further, for example, to approximately 70 psi, the shape of the control aperture 114 is such that approximately one-half the light from the light source 64 to the photoelectric cell 82 is blocked. Finally, the control aperture 114 is such that when the pressure within the Bourdon tube 50 drops to some predetermined minimum level, approaching zero psi, the aperture 114 will be moved entirely out of registry with the photoelectric cell 82 and light source 64, with the result that the masking element 108 entirely blocks the transmission of light therebetween. It will be noted that the present invention is not intended to be limited to the specific construction of the masking element 108 hereinbefore described, since the element 108 may assume various other shapes and may be fabricated of various other materials. For example, the element 108 could consist of an ellipsoid-shaped member, the outer periphery of which is shaped so as to provide the desired interruption of light transmission from the light source 64 to the photoelectric cell 82. Additionally, the masking element 108 could be fabricated of a transparent material which has a portion thereof gradually shaded or colored, as shown in FIGS. 5-7 and hereafter described in detail. It will also be noted that the particular configuration and location of the various components of the fan control 22 of the present invention are not necessarily limited to the arrangement shown in the drawing and that such components could be mounted on a conventional printed circuit board having the various electrical conductors described herein printed thereon, as will be appreciated by those skilled in the art. Additionally, it will be seen that various means other than the adjustable shaft 86 may be provided for varying the magnitude of light transmitted to the cell 82 for a given desired head pressure. For example, instead of having the photoelectric cell 82 be movable by means of the aforedescribed shaft 86, it would be possible to have the masking element 108 adjustably mounted upon the shaft 58, whereby the element 108 could be selectively rotatably positioned upon the shaft 58 in accordance with the desired pressure of the compressor 12.

The fan motor 20 of the fan 18 consists of a typical AC motor, the speed of which is controlled by conventional control devices, such as controlled rectifiers or triacs, etc. As is well known in the art, the firing angle at which the control devices are caused to conduct may be controlled by the input circuit to the gate electrode of the control devices, thus varying the amount of energy fed to the fan motor 20. The phase control 36 and resistance profided by the cell 82 generally functions to control the input circuit of such a control device. More particularly, the phase control 36 is shown as being housed in a suitable enclosure or housing 118 which is secured to the side 32 of the housing 30 by means of suitable screws, bolts or the like 120. The phase control may consist of any suitable known motor speed control which generally functions to rapidly switch "off" and "on" the AC supply to the fan motor 20 by cutting off a fraction of the AC cycle. This, of course, is accomplished by controlling the phase angle of the AC wave at which the triac or other control rectifier is triggered. A suitable phase control is marketed by Omnetics Incorporated of Syracuse, N.Y., and is marketed under the trade name Omnephase. Suitable AC phase control models sold under the Omnephase trade name are models 602A and 1002A and typically have an input voltage characteristic of 120 volts, an off state voltage of 200 volts, a forward voltage drop of 1.80 volts, an on state current of 6-10 amps, a peak surge on-state current of 100-200, and a peak off-state current of 2 milliamperes. It will be appreciated, of course, that various alternative AC phase controls may be utilized without departing from the scope of the present invention and that the aforesaid typical phase control devices are described merely by way of example. The phase control 46 is communicable with the electrical circuitry of the fan control 22 of the present invention by conductors 122, 124 and 126 which are connected to terminals 106, 104 and 76, respectively, of the terminal block 48. It will be noted that the electrical conductors 26 and 28, hereinabove described, are connected to the terminals 78 and 104, respectively, of the terminal block 48, while the terminals 76 and 78 are connected via conductors 128 and 130, respectively, to a suitable source of electrical energy, which, for example, may consist of the electrical energy supplied to the compressor 12.

Assuming that the photoelectric cell 82 is properly positioned with respect to the light source 64 and that the light masking element 108 is properly rotationally positioned upon the shaft 58 so as to achieve the desired rotation thereof for a given desirable range of pressure changes occurring within the Bourdon tube 50 and originating at the discharge side of the compressor 12, the operation of the fan control 22 of the present invention is such that when a minimum pressure condition exists within the compressor 12, the masking element 108 is rotationally positioned so as to prevent the transmission of light from the light source 64 to the photoelectric cell 82. Accordingly, the maximum amount of electrical resistance is introduced into the electrical circuit of the fan motor 20. Depending upon the particular type of photoelectric cell 82 which is utilized, this resistance may be in the order of 100,000 ohms or greater. As the pressure at the discharge end of the compressor 12 increases, the masking element 108 will be rotated, thereby causing a greater amount of light to be transmitted from the light source 64 to the photoelectric cell 82. For example, when the pressure in the Bourdon tube 50 reaches approximately 75 psi, approximately one-half of the light produced by the light source 64 will be transmitted to the photoelectric cell 82, and as the pressure increases further to approximately 125 psi, approximately 75 percent of the light source 64 will be transmitted to the photoelectric cell 82. The percent of light transmitted to the cell 82 will continue to increase with increased pressure in the Bourdon tube 50 until such time as the pressure therewithin is in the order of 150 psi, at which time virtually the entire amount of light produced by the light source 64 will be transmitted to the photoelectric cell 82. When the maximum amount of light is received by the photoelectric cell 82, the resistance introduced thereby is at a relatively low level, for example, in the order of 600 ohms or less, with the result that the fan motor 20 is operating at virtually full r.p.m., thereby resulting in the maximum amount of air being passed over the compressor 12.

As previously mentioned, the fan control 22 of the present invention will find particularly useful application in low ambient temperature operating conditions, particularly where the refrigeration system 10 is utilized in an ice making machine or the like wherein the defrost water is heated by the discharge gases of the refrigeration system. It will be appreciated, of course, that the principles of the present invention will find wide and varied application other than ice making equipment, where a small, compact, easily adjustable fan control is to be employed.

FIGS. 5-7 depict a modified embodiment of the aforementioned light masking element which is hereinafter designated by the numeral 200. The element 200 is adapted to be located in the same general location as the aforedescribed element 108 and like the element 108, is of a generally annular disc-shaped configuration. Preferably the element 200 is fabricated of a transparent acrylic plastic material approximately 0.030 inch in thickness. The element 200 is formed with a central axial opening 202 through which an adjustment shaft 204 partially extends. The shaft 204 is shown as generally comprising a generally cylindrical rearwardly extending section 206 which projects through the opening 202 in the element 200. Additionally, the shaft 204 includes an integral pointer section 208 consisting of an alignment pointer 210 which is disposed adjacent the outer surface of the masking element 200. The shaft 204 also comprises a manually engageable or handle portion 212 which is formed integrally of the sections 208 and 206 and like the sections 208, 206 is preferably fabricated of a molded plastic material such as Lexan. The shaft 204 is preferably of a dark, i.e., non-light transmitting, color such as black.

The rearward end of the cylindrical section 206 of the shaft 204 is formed with a central blind bore 214 which is adapted to nestingly receive the outer end of the shaft 58, whereby the shaft 204 is drivingly connected to the Bourdon tube 50, with the result that rotation of the shaft 58 due to a pressure change within the tube 50 will result in concomitant rotation of the shaft 204 and element 200. It will be appreciated, of course, that the shaft 204 may be connected in other ways to the Bourdon tube 50 without departing from the scope of the present invention.

The light masking element 200 is adapted to be rotatable with the shaft 204, yet is rotatable relative thereto when the shaft 204 is held stationary and a suitable rotative force is applied to the element 200. Toward this end, a suitable Tinnerman type washer 216 or the like is secured to the rearward side of the element 200, with the resilient spring fingers 218 of the washer 216 frictionally engaging the outer periphery of the cylindrical section 206. With this arrangement, the element 200 is not freely rotatable upon the shaft 204, yet when the shaft 204 is held stationary by manually grasping the portion 212 thereof, a rotative force applied to the element 200 will result in rotation thereof relative to the shaft 204 so that a predetermined rotational relationship between the element 200 and shaft 204 may be achieved.

In accordance with the present invention, the element 200 is preferably fabricated of a transparent material with certain arcuate sectors thereof shaded, colored or otherwise provided with means for limiting the transmission of light from the light source 64 to the photoelectric cell 82. More particularly and as best seen in FIG. 7, the element 200 is divided into three generally arcuate sectors 220, 222 and 224. The sector 220 is approximately 120 arcuate degrees plus or minus five degrees and is suitably colored or otherwise obscured so as to permit 0 percent of the light produced by the light source 64 from being transmitted to the photoelectric cell 82 when the masking element 200 is properly rotationally positioned such that the sector 220 is interposed therebetween. The arcuate sector 222 is approximately 230 arcuate degrees and is adapted to permit 100 percent of the light produced by the light source 64 to be transmitted to the photoelectric cell 82. In other words, the sector 222 is preferably entirely transparent. The sector 224 on the other hand is approximately 10 arcuate degrees and is intended to be gradually uniformly shaded or colored from one radial edge thereof to the opposite radial edge thereof, with the shading or coloring gradually increasing from zero amount of shading at the radial edge thereof adjacent the sector 222 to a maximum of a total amount of shading at the radial edge thereof adjacent the sector 220. This, of course, results in a gradually decreasing amount of light being transmitted from the light source 64 to the cell 82 as the masking element 200 is rotated from a position wherein the sector 222 thereof is interposed between the source 64 and a cell 82 to a position wherein the sector 200 is interposed therebetween.

Operation of the light masking element 200 is essentially the same as the masking element 108 in controlling the transmission of light from the source 64 to the photoelectric cell 82 in accordance with the pressure changes occurring within the Bourdon tube 50. The element 200 is rotatably positioned upon the shaft 204 such that when a minimum pressure condition exists within the compressor 12, the sector 220 of the element 200 is interposed between the light source 64 and cell 82. As the pressure at the discharge end of the compressor 12 increases, the masking element 200 will be rotated such that the graduated sector 224 thereof moves into position between the light source 64 and a cell 82, thereby causing a predetermined amount of light to be transmitted to the photoelectric cell 82. The percentage of light transmitted to the cell 82 will continue to increase with increased pressure within the Bourdon tube 50 until the pressure therewithin reaches a predetermined magnitude, at which time the masking element 200 will be rotated via the shafts 58 and 204 to a position wherein the transparent sector 222 of the element 200 is in registry with the direction of light travel from the light source 64 to the cell 82. As previously mentioned, when the maximum amount of light is thus received by the cell 82, the resistance introduced thereby into the electrical circuit of the fan motor 20 is at a minimum level, resulting in the fan motor 20 operating at full r.p.m. In the event it is desired to adjust the operating speed of the fan motor in accordance with a predetermined compressor pressure, the light masking element 200 may be selectively rotatably adjusted upon the shaft 204 by conveniently manually grasping the portion 212 with one hand and rotating the element 200 with the other hand. Suitable means such as indicia 226 may be provided on the face of the element 200 for selective alignment with the pointer 210 for achieving predetermined operating characteristics of the fan control of the present invention, as will be appreciated by those skilled in the art.

While it will be apparent that the preferred embodiments herein illustrated are well calculated to fulfill the objects stated above, it will be appreciated that the present invention is susceptible to modification, variation and change without departing from the scope of the invention.

Claims

I claim:

1. A control for a refrigeration system including a compressor, a condensor, an evaporator and an electrically energized fan for passing air in heat exchange relation to the condenser,

a light source,

light responsive means for performing an operation in the system, and

means for controlling the magnitude of light transmitted from said source to said light responsive means, said last mentioned means being at least partially interposed between said light source and said light responsive means and having one portion thereof adapted to permit the transmission of substantially the entire magnitude of light produced by said light source to said light responsive means, and another portion thereof adapted to limit the transmission of light produced by said light source to said light responsive means.

2. The invention as set forth in claim 1 which includes a Bourdon tube operable in response to the refrigerant pressure in the compressor portion of said refrigeration system, which includes a photoelectric cell, wherein said means for controlling the magnitude of light transmitted from said light source comprises a light masking element movable in response to operation of said Bourdon tube.

3. The invention as set forth in claim 2 wherein said masking element is rotatable about a predetermined axis in response to operation of said Bourdon tube to control the magnitude of light transmitted from said light source to said photoelectric cell.

4. The invention as set forth in claim 3 which includes an electronic phase control, and wherein said photoelectric cell is cooperable with said phase control to control the firing angle at which the phase control supplies electrical energy to the cooling fan.

5. The invention as set forth in claim 1, wherein said control comprises a housing having a low light reflective interior, which includes a Bourdon tube and conduit means communicating said tube with the discharge side of the refrigeration compressor, wherein said light source is located adjacent said Bourdon tube, which includes a generally circular shaped light masking element mounted for rotation about an axis arrangement generally coaxial of said Bourdon tube, which includes mechanical linkage means operatively connecting said Bourdon tube with said shaft, whereupon a change in pressure in said Bourdon tube results in rotation of said shaft, which includes a photoelectric cell disposed on the opposite side of said masking element from said light source, which further includes means on said masking element for varying the magnitude of the light transmitted to said photoelectric cell in response to changes in the rotational position of said masking element, and whereupon said refrigeration fan includes an AC motor whose speed is controlled by a control device, the firing angle of which is varied by the resistance of the input circuit of the gate electrode of the control device, and wherein said photoelectric cell is operable to change the resistance in said input circuit and thereby vary the amount of energy supplied from a suitable source thereof to said fan motor.

6. The invention as set forth in claim 1, wherein said last mentioned means comprises a partially transparent member interposed between said light source and said light responsive means for selectively controlling the transmission of light therebetween.

7. The invention as set forth in claim 6 wherein said masking element is mounted on a rotatable shaft, and which includes mechanical linkage means actuable in response to operation of said Bourdon tube to rotate said shaft and said masking element thereon.

8. The invention as set forth in claim 7 which includes adjustment means for selectively varying the amount of light received by said photoelectric cell from said light source for a given pressure condition in said refrigeration system.

9. The invention as set forth in claim 6, wherein said member is generally disc-shaped and is rotatably mounted interjacent said light source and said light responsive means.

10. The invention as set forth in claim 9, wherein said member is rotatably mounted upon a shaft arranged generally parallel to the direction of light travel from said light source to said light responsive means, and wherein said shaft is rotatable in response to a preselected operating condition in said refrigeration system.

11. The invention as set forth in claim 9, wherein an arcuate sector of approximately 120.degree. of said disc-shaped member prevents the transmission of light from said light source to said light responsive means.

12. The invention as set forth in claim 9, wherein an arcuate sector of between 150.degree. - 250.degree. of said disc-shaped member permits complete transmission of light from said light source to said light responsive means.

13. The invention as set forth in claim 9 wherein an arcuate sector of between 5.degree. - 15.degree. of said disc-shaped member permits a substantially uniformly graduated increase in the transmission of light from said source to said light responsive means from 0 percent to 100 percent.

14. The invention as set forth in claim 9, wherein said disc-shaped member comprises three arcuate sectors, wherein one of said sectors is approximately 120.degree. and is operable to block 100 percent of the light transmitted from said light source to said light responsive means, wherein another of said sectors is approximately 230.degree. and is adapted to permit 100 percent of the light produced by said light source to be transmitted to said light responsive means, and wherein the other of said sectors is approximately 10.degree. and is uniformly graduated to permit from 0%-100% of the light produced by said light source to be transmitted to said light responsive means.

15. The invention as set forth in claim 9, wherein said shaft comprises a generally cylindrical section having said disc-shaped member rotatably carried thereon, wherein said shaft includes a manually engageable portion and a pointer section adapted to be selectively aligned with indicia on said disc-shaped member in order to provide for preselected rotatable positioning of said member on said shaft.

16. The invention as set forth in claim 10, wherein said disc-shaped member is rotatable relative to said shaft.

17. The invention as set forth in claim 16, which includes indicia and alignment means for selectively rotatably adjusting said disc-shaped member.

18. The invention as set forth in claim 17, wherein said indicia means is on said member and wherein said alignment means includes a manually engageable means adapted to manually resist rotation of said shaft and to permit rotation of said disc member relative thereto.