US2297370A - Refrigeration - Google Patents

Description

Sept. 29, 1942. A. D. slEDLE 2,297,370

IUEFRIGERA'IIONv Filed July 20, 1938 2 Sheets-Sheet 1 A l .Fo o 4 M4, 24 LL? l INVENTOR Arnold D. Siedle ATTORNEY Patented Sept. 29, 1942 REFRIGERATION Arnold D. Siedle, Canton, Ohio, assignor to The Hoover Company, North Canton, Ohio, a corporation of Ohio Application July 20, 1938, Serial N0. 220,191

33 Claims.

This invention relates to refrigerating apparatus and more particularly to a novel control mechanism for such apparatus.

Refrigerating mechanisms have been provided heretofore, which include means to defrost the evaporators of such system manually, by a manually set mechanism provided with an automatic release, or fully automatically. Previous systems of the straight manual type have the disadvantage that the operator may neglect to defrost the box indefinitely, or having discontinued operation of the refrigerating system for defrosting purposes, the operator may neglect to restore the mechanism to normal operation with the result that ice is not produced and foods stored in the refrigerator spoil. Those systems in which the ually and are restored to normal operation automatically at the end of the defrosting period"v avoid the objection that the system may not be restored to normal operation at the end of the defrosting period, but they do not avoid the difficulty that the operator may not trouble to defrost the refrigerator when necessary or desirable. The fully automatic defrosting systems have the serious disadvantage that they may come into an operation at an inopportune moment or at a time when defrosting is in fact unnecessary because the box is not in normal use. Attempts have been made to defrost the evaporator of refrigerating systems whenever the frost coat reached a predetermined depth. Prior devices of this nature operate by contact between a frost contacting thermostat or by a feeler element which contacts the frost; however, these devices are very inaccurate as the temperature, hardness and density of the frost coat is subject to considerable variation which produce different reactions at different times in the thermostat or feeler.

According to this invention there is provided a novel defrosting mechanism in which the defrosting period may be initiated either fully automatically or in response to a frosted condition of the evaporator and normal use of the box as evidenced by opening and closing the door thereof. Additionally, the present invention provides a means whereby the defrosting mechanism is automatically rendered inoperative when the cold control for the refrigerating system is actuated to the fast-freezing position in order to produce ice cubes rapidly or to refrigerate desserts.

It is a further object of the invention to provide a defrosting mechanism which will respond accurately and positively to a predetermined depth of frost deposition on the evaporator without being inuenced by the temperature, hardness, or densityrof said frost coat.

According to the invention there is provided a refrigerating control mechanism embodying a defrosting control which posi @ie/systenr the purpose of defrosting when the frost coat o the evaporator reaches a predetermined depth, which accomplishes this novel result by utilizing the positive and sure action of a photoelectric cell control, which is automatically rendered inoperative if the operator of the refrigerator desires to produce refrigeration at a rapid rate, and which is operative only during periods when the refrigerating compartment is in normal usage.

Other and further objects of the invention will become apparent as the description proceeds when taken in connection with the accompanying drawings in which:

Figure 1 is a diagrammatic representation of one type of refrigerating system to which my invention may be applied and illustrating the manner in which the control mechanisms are mounted upon the casing of an enclosed evaporator.

Figure 2 is a top plan view of a refrigerating cabinet including an evaporator and showing the various connections to the various elements of the control mechanism.

Figure 3 is a diagrammatic illustration of the complete control mechanism included in Figure 2.

Figure 4 is a diagrammatic representation of another form of the invention.

Figure 5 is a detail view of a part of the mechanism illustrated in Figure 4.

Referring now to the drawings, the invention will be described in detail. I have elected to illustrate my invention as the same is applied to a continuous three-fluid absorption refrigerating system of the type utilizing a valve to control the ow of gas to the boiler heater and an electrical motor to circulate the inert gas; however, it is to be understood that this form of refrigerating system has been selected for purposes of illustration only and that the invention may be applied equally well to other forms of refrigerating systems.

The refrigerating system illustrated in Figure 1 is of the continuous three-duid type and it includes a boiler B, an analyzer D, an air cooled rectifier R, a tubular air cooled condenser C, an evaporator E, a gas heat exchange H, an absorber A, a reservoir S, a liquid heat exchanger L and a circulating fan F which is driven by an electrical motor M. These elements are suitably connected by various conduits to form a plurality of gas and liquid circuits to which reference will be made hereinafter.

The refrigerating system just described will be charged with a suitable refrigerant, such as ammonia, a suitable absorbent, such as water, and a suitable inert pressure equalizing rnediurnI such as nitrogen.

Application of heat to the boiler generator refrigerant vapor from the strong solution therein contained which vapor then passes upwardly through the analyzer D in counterow relationship to strong solution flowing downwardly therethrough. Further refrigerant vapor is generated in the analyzer, the heat of vaporization being supplied by the heat of condensation of absorption solution vapor which is generated in the boiler. The refrigerant vapor is conveyed from the analyzer to the upper part of the condenser by a conduit Il which includes the air cooled rectifier R. The rectifier R causes condensation of any vapor of absorption solution which may pass through the analyzer D. In the condenser, the refrigerant vapor is converted to the liquid phase by heat exchange with cooling air. The liquid refrigerant formed in the condenser is drained therefrom through a conduit l2 into the upper portion of an evaporator E. The evaporator E may be of any desired type or formation and may include a finned box cooling section; as shown, it is of the tubular type and enclosed with a suitable casing. In the evaporator, the liquid refrigerant flows downwardly in counterflow relationship to pressure equalizing medium flowing upwardly through the evaporator into which the refrigerant liquid vapoiizes to produce refrigeration.

The weak solution formed in the boiler by the generation of refrigerant-l vapor is conveyed therefrom to the upper portion of the air cooled absorber A through a conduit I3, the liquid heat exchanger L, and a conduit I4. It is apparent that the upper portion of the absorber is at an elevation appreciably above the normal liquid level prevailing in the boiler-analyzer system, wherefore some means must be provided in order to elevate the liquid into the absorber. For this purpose, a small bleed-off conduit l5 is connected between the discharge conduit 20 of the circulating fan F and the conduit I4 below the liquid level normally prevailing therein, whereby the weak absorption solution is elevated through the conduit i4 by gas lift action. The absorption solution flows downwardly through the absorber in counterflow relationship with the pressure equalizing medium refrigerant vapor mixture formed in the evaporator. The refrigerant vapor content of this mixture is absorbed by the weak solution to form strong solution and the heat of absorption is rejected to the surrounding cooling air. The strong solution formed in the absorber is drained therefrom into the solution reservoir S through a conduit I6 from which the strong solution is returned to the upper portion of the analyzer through the conduit l1, the liquid heat exchanger L and the conduit I8.

The inert gas placed under pressure by the circulating fan F is conveyed therefrom to the bottom portion of the evaporator E through the conduit 20, the gas heat exchanger H, and a conduit 2|. The inert gas passes upwardly through the evaporator, picking up refrigerant vapor in the manner heretofore described, and is discharged from the top of the evaporator through a conduit 22 into the gas heat exchanger H from which the pressure equalizing medium relrigerant vapor mixture is led to the bottom portion of the absorber A by a conduit 23. The refrigerant vapor mixture then flows upwardly through the absorber in the manner heretofore described and is conducted to the suction inlet of the circulating fan F by a conduit 24.

A suitable drain conduit 25 is provided between the lower portion of the evaporator E and the strong solution return conduit l1.

In order to properly regulate the system just defined, it is necessary to exercise proper control over the circulating motor M and the gas burner G to control the refrigerating system in order thatl it may meet all demands made thereupon.

Referring now to Figures 1 to 3, the refrigerating control mechanism will be described in detail. The control mechanism includes an electrical switch 30 which is connected in the control circuit 3l of the electrical motor M and a gas valve 33 which is interposed in the gas supply conduit 34 for the gas burner G. A suitable bypass 35 is provided around the valve 33 in order to maintain a small pilot or igniting flame upon the burner G during periods when the control mechanism has caused closure of the valve 33. It will be understood that the burner will be provided With a suitable mechanism designed to prevent the supply of fuel thereto in the event of total extinguishment of the ame thereon.

The valve 33 and the switch 30 are connected together by a link 36 of such length that one is always closed when the other is open. The link 36 is actuated by a thermostatic control mechanism including pressure responsive bellows 33. The bellows 38 are slidably mounted in a guide 39 against which the enlarged rear plate 40 of the bellows is urged by a stiiT spring 4l which surrounds the connecting conduit 42 of the bellows and contacts a suitable fixed support 43. The free end of the bellows 38 engages an adjusting and actuating rod 44 which is urged against the bellows by the bias of an adjusting spring 45 engaging in a spring retaining cup 46 on the rod 44. The spring 45 also engages a nut 41 which has threaded engagement with an adjusting screw 48. The screw 48 abuts a fixed wall 49 and is provided with an actuating extension 50. A suitable snapacting mechanism 52 connects the actuating elements 44 and 36 for transmitting motion therebetween. The conduit 42 of the bellows is connected through a capillary tube 53 to a fluid retaining bulb 54 positioned to be responsive to temperature conditions in the evaporator, whereby changes in temperature of the evaporator are reilected by changing the pressure in the fluid contained in the bellows, capillary tube and bulb system with consequent expansion and contraction of the bellows. Expansion of the bellows 38, evidencing a demand for refrigeration, advances the rod 44 to the left as viewed in Figure 3, until the over center mechanism 52 has passed over center whereupon the connecting link 36 will be snapped from its extreme right position, illustrated, to the extreme left position with consequent closure of the switch 30 and opening of the valve 33. This action will energize the system which will then produce refrigeration until such time as the evaporator shall have reached the temperature for which the refrigerating control mechanism is set whereupon the bellows 38 will have contracted sufficiently to cause the above described sequence of events to occur in reverse order resulting in deenergization of the refrigerating system.

The temperature at which the pressure sensitive bellows 38 energizes and de-energizes the refrigerating system are determined by the compression of the spring 45 which is regulated from a suitable manually actuated knob 56 mounted on a suitable panel above the front portion of the evaporator. The knob 56 connects directly to the end of the actuating shaft 50 for the adjusting screw 48.

The control mechanism just dened is also provided with a defrosting device which will now be described. A latch bar 58 is pivotally mounted at 55 and has a slot and pin connection with the rod 44 as indicated at 51. The free end of the rod 58 extends through an elongated slot 59 in the armature 60 of a solenoid 6| A latch element 62 is carried by the latch bar 58 and is adapted to engage with a latch keeper 63 pivotally mounted in any suitable manner at 64 and urged in a clockwise direction about the pivot 64 by a torsion spring 65. The latch keeper 63 also includes an extending cam surface 66 which extends downwardly and in contact with the rear plate 40 of the bellows 38. The arrangement is such that locking engagement between the latch elements 62 and the latch keeper 63 will prevent normal expansion of the bellows. Under these conditions the evaporator will continue to rise in temperature until it has reached a value sufficient to insure that it has melted all frost therefrom, whereupon the pressure in the bellows will be sufficient to cause the same to expand in a direction opposite to its normal direction of expansion against the bias of the stiff spring 4|, whereupon movement of the plate 46 to the right, as viewed in Figure 3, will rock the latch keeper 63 about its pivot in a counter-clockwise direction by reason of the engagement between the plate 40 and the cam 66. Movement of the latch keeper 63 in a counter-clockwise direction releases the latching engagement between the elements 62 and 63 whereupon the control mechanism snaps back into its normal condition and normal cycling of the refrigerating apparatus is resumed.

The defrosting control mechanism operates by energizing the solenoid 6| which will then pull the armature 60 to the right, as viewed in Figure 3. This movement of the armature will also force the rod 44 and the latch bar 58 to the right, as viewed in Figure 3, a distance sufficient to cause the elements 62 and 63 to fall into latching engagement.

The control for the solenoid 6| will now be described. Electrical energy is supplied to the defrosting control mechanism from a suitable source of supply represented by the wires 10 and 1|. The wire 16 connects directly to the terminal 12 of a photoelectric cell relay 13 of a known type and to a wire 14 which connects directly to the solenoid 6|. The other terminal of the solenoid 6| is connected through a wire 15 to a contact strip 16 which is mounted to be contacted by a contact arm 11 rigidly carried by the regulating shaft 50. As indicated in Figure 3, the contact strip 16 extends over all positions of the control knob 56 except the fast-freezing position thereof; therefore, a circuit is made between the wires 15 and the wires 18 connected to the contact arm 11 in all positions of the control valve 56 except in the fast-freezing position thereof. The wires 18 connect directly to one terminal 19 of a relay control switch 80. The

other terminal 8| of the relay switch is connected to a switch 83 by a wire 82. The other terminal of the switch 83 connects directly to the line 1|.

Also connected to the line 1| is a switch 84 which is connected to an illuminating lamp 86 and the terminal 94 of the relay 13 by a wire 85. A wire 81 connects the other terminal of the lamp to the Wire 14 which connects directly to the line wire 10. The lamp 86 is mounted on a suitable support 89 which is mounted in any desired manner on the evaporator. The support 89 carries a small lens 90 which is positioned to direct the light from the lamp 86 across the back portion of the evaporator in the direction of a photoelectric cell 82 also suitably carried on the rear portion of the evaporator casing. This positioning of the lamp and photoelectric cell is illustrative only. Other arrangements may be used if desired.

The photoelectric cell is connected to the photoelectric cell relay mechanism 13 which will now be described briefly The terminal 12 of the relay control 13 is connected to the primary of a transformer 93 which also connects to the terminal 94y of the relay 13. A pair of wires 95 and 96 connect the photoelectric cell to the terminals 61 and 98, respectively, of the relay control 13. One terminal of the secondary of the transformer 93 is connected by a wire |60 to the actuating coil of the solenoid 99 of the relay switch 8U. The other terminal of the secondary of the transformer 93 is connected by a wire |0| to the anode |02 of a suitable thermionic tube |03. The cathode of the tube |03 is connected through a wire |04 to a variable resistance element |05 which connects through a wire |06 to the other terminal of the solenoid coil 66. A suitable condenser |01 is shunted across the coil 99. The grid of the thermionic tube |03 is connected by a wire |68 to the terminal 98 of the control box 13 and it is also connected to the anode |02 through a resistance element |89.

The switches 83 and 84 are mounted within the insulating wall of the refrigerating compartment ||0 and are provided with actuating plungers and ||2, respectively, which project through the panel defining the door opening ||3 of the refrigerating compartment H6. The arrangement is such that both switches are urged to open position by the door ||4 of the refrigerating compartment when the same is in closed position. When the door is opened, the switch 84 is first closed by reason of the fact that the plunger ||2 is appreciably shorter than the plunger Figure 2 illustrates the arrangement of the evaporator E in the refrigerating chamber ||0 and the positions of the various elements of the control mechanism thereon. As will be seen in Figure 2, the evaporator is positioned in the central portion of the compartment ||0 with the lamp 86 and the photoelectric cell 92 positioned. in opposite rear corners thereof. The photoelectric cell relay mechanism 13 is positioned in the top rear corner of the evaporator and with the box ||6 which houses the switching mechanism 16 and 11 positioned in the top center portion of the evaporator behind an upstanding decorative panel ||1 in front of which is mounted the regulating knob 56. It is also apparent from Figure 2 that the cabinet is provided with a rear flue ||8 which will normally house certain air cooled portions of the refrigerating system described in connection with Figure 1. As shown,

the gas heat exchanger H is partially embedded in a Window element |20 which extends into an opening |2| in the rear wall of the chamber ||0 and through which opening the evaporator is inserted in assembling the refrigerating apparatus 5 within the cabinet.

The above described form of the invention operates as follows: During the normal operation of the system, the bellows 38 will expand and contract in response to demand for refrigeration, energizing and de-energizing, respectively, the electrical motor M and the gas burner G to place the refrigerating system in operation and to discontinue operation thereof as the case may be. This operation maintains the refrigerating l5 chamber between the temperature limits corresponding to the limits for which knob 56 is set. As the refrigerating system operates, frost will accumulate on the exterior surface of the evaporator and will build out therefrom until the flost coat f eventually intersects the path of the light beam b traveling from the lamp 86 to the photoelectric cell S2. If the door ||4 is opened 'after the frost coat is built out suciently to intersect said light beam, the following operation will occur: As the door is opened, the switch 84 will be closed and will energize the lamp 86. Continued opening of the door permits the switch 83 to close, which then completes the circuit from the lines '1| through the switch 83, the relay 30 switch 80, the contact the contact strip 16, the wire 15, the solenoid 6|, the wire 14 to the other line wire 10, provided of course that the light beam is interrupted and the photoelectric cell relay has operated the switch 80 to closed 35 position. Under these conditions, the solenoid 6| attracts the armature 60 which pulls the latching rod 58 into latching engagement with the latch keeper 63 and thereby locks the bellows 38 against expansion in a direction to energize the 40 refrigerating system until the bellows have first expanded rearwardly, as viewed in Figure 3, in response to a defrosting temperature condition to release the engagement between the latch keeper 63 and the latch bar 58. If, however, the 45 frost coat has not built out suiiciently to interrupt the light beam directed from the lamp 86 toward the photoelectric cell 92, the relay Will not operate to close the switch 80 and the defrosting mechanism will not be energized. so

If the control mechanism should be set for the fast-freezing position, as it would be in the event of an abnormal and rapid demand for icc cubes or for dessert freezing purposes, the circuit for the defrosting actuating solenoid 6| will 55 be broken by reason of the disengagement between the contact arm and the contact strip 16 whereby the defrosting mechanism will not be in condition to be energized until the control knob 56 has been returned to some normal con- @n trolling position. This prevents inopportune operation of the defrosting mechanism.

Referring now to Figures 4 and 5, a modified form of the invention will be described. Certain portions of this mechanism are identical with 65 those previously described in connection with Figure 1 and are given the same reference characters primed.

In this form of the invention the current supply wires and 'l0' connect directly to the 70 primary of a transformer |50, the secondary of which continuously energizes the lamp 86. The line wire is connected directly to the motor M and to the solenoid |5| of a solenoid operated gas valve |52 by a pair of wires |53 and |54, 75

respectively. The other terminals of the motor M' and the solenoid |5| are connected by means of a pair of wires |55 and |56, respectively, to any suitable form of adjustable thermostatic control switch which will be housed in a suitable casing mounted on top of the evaporator and adapted to be regulated by the adjusting knob 56. The other terminal of the thermostatic switch is connected by means of a wire |58 to the terminal 8| of the photoelectric cell relay 'I3'. The relay 'I3' is identical with the relay 'I3 except that the switch which bridges the terminals 19 and 8| is normally closed and is moved to open circuit position by the relay mechanism when the light beam is interrupted. The terminal 8| is also connected by means of a wire |6| to a fastfreezing terminal |62 which is adapted to be contacted by a contact arm |63 when the knob 56' is positioned in the fast-freezing position. The contact arm |63 is connected by means of a wire |64 to the terminal 'I9' of the photoelectric cell relay box 13'. The terminal '|9 is also connected to the supply line 'l0' by means of a wire |65. The line wire is also connected to the terminal 94 of the defrosting relay box 13' by means of a wire |66.

This form of the invention is designed and intended to be utilized with a refrigerating system which is identical with that disclosed in connection with Figure 1, but it also may be utilized with any other form of refrigerating system.

In the operation of this form of the invention, the lamp 86' is continuously energized and principally for that reason a very small lamp is utilized. As long as the light beam flowing from the lamp 86' to the photoelectric cell 92 is uninterrupted, the relay switch bridging the terminals 'I9' and 8 will be in closed position thereby completing the circuit from the lines 1| through the motor M and solenoid |5|. the wire |56, the thermostatic switch in the casing |60, the wire |58 to the terminal 8|', through the relay switch to the terminal '19', and through the wire |65 to the line 'l0'. Therefore, the motor M and the solenoid |5| will be energized or deenergized by the thermostat-ic switch in accordance with demands for refrigeration and in accordance with the setting of the knob 56. If at any time the frost coat on the evaporator builds out far enough to intersect the light beam between the lamp 86 of the photoelectric cell 02', the relay mechanism 13 will operate to open the circuit across the terminal 19 and 8| thereby de-energizing the refrigerating system and permitting frost to melt therefrom.

However, should the housewife at any time desire to return the apparatus to operation for fast freezing or for rapid production of ice, she has only to move the knob 56' to the fast-freezing position which will then close the circuit through the contact |62 and |53 which will short circuit the now open relay switch bridging the contacts '19' and 8|' and will energize the circulating motor M' and the solenoid |5| to energize the refrigerating system regardless of the depth of frost coat on the evaporator.

In each form of the invention the apparatus has been illustrated as if the light beams b from the lamp to the photoelectric cell were interrupted by a nodule or cone f of frost building out from the back plate of the evaporator. This conveniently illustrates the operation of the light sensitive frost depth responsive mechanism; however, it is to be understood that frost is formed on substantially all surfaces of an evaporator casing of the type illustrated, but such a continuous frost coat will interrupt the light beams b just as eicaciously as the nodule f, illustrated. Preferably, the apparatus is arranged to respond to a very light frost coat in order that the refrigerating apparatus will operate at; substantially maximum eiciency at all times.

In each form of the invention the lamp and photoelectric cell have been shown at opposite rear corners of the evaporator casing, though other arrangements are contemplated within the scope of the invention. For example, the lamp and photoelectric cell might be positioned on opposite sides of an edge or corner of the evaporator casing in which event the light beam will be interrupted by the frost coat building up on the edge or corner of the evaporator casing. The invention is equally well adapted to operate in response to frost deposition on other evaporator elements such as a conduit or plate. With the form of the invention illustrated in Figures 1 to 3, the lamp may be the lamp usually provided to illuminate the interior of the refrigerator. If this structure is utilized, the photo-electric cell can be shielded as by a tube to receive light from the source only in a line passing close to some part of the apparatus which is subjectl to frost deposition whereby'reiected light will not prevent interruption of the light striking the photoelectric cell by the frost on the evaporator.

It is apparent from the above description that the present invention provides a refrigerating control mechanism in one form of which opening and closing of the door to the refrigerating compartment causes a photoelectric control mechanism to determine whether or not the evaporator is in need of defrosting, and, if such need exists, automatically to set the apparatus into defrosting operation which will continue until the evaporator has defrosted. This construction is highly advantageous because it prevents unnecessary defrosting of the apparatus, for example during periods when food-stuffs are to be preserved but are merely remaining in the box which is not opened and closed as in normal usage. Furthermore, a means is provided whereby the housewife can render the defrosting mechanism inoperative in order to produce quick freezing regardless of the depth of frost deposition on the evaporator. In a modified form of the invention, the defrosting mechanism is fully automatically operated and will defrost the evaporator when the depth of frost coat reaches a value sufficient to demand such operation. In this form of the invention also a means is provided whereby the housewife may produce refrigeration by turning the control dial to the quick freezing position regardless of the depth of frost coating on the evaporator.

Vhile I have illustrated and described but two embodiments oi the invention, it is to be understood that the invention is not to be limited thereto but thatvarious changes may be made in the arrangement, construction and proportions of the parts without departing from the spirit of the invention or the scope of the appended claims.

I claim:

l. Refrigerating apparatus comprising a cooling unit, means for supplying a cooling medium to said cooling unit, means for regulating said cooling medium supply means, and means including light sensitive means arranged to operat@ said regulating means to non-supplying condition when a predetermined depth of frost collects on said cooling unit.

2. Refrigerating apparatus comprising a cooling unit, means for normally maintaining said cooling unit between predetermined temperature limits, and means including light sensitive means constructed and arranged to render said cooling unit inoperative in response to a predetermined frost deposit thereon to defrost said cooling unit.

3. Refrigerating apparatus comprising a cabinet, a cooling unit in said cabinet, a movable door for said cabinet, means for supplying a cooling medium to said cooling unit, means to regulate the supply of cooling medium to said cooling unit, means including light sensitive means arranged to cause discontinuance of the supply of cooling medium to said cooling unit whenever frost accumulates on said evaporator to a predetermined depth, means operative by opening of said door for placing said light sensitive means in operation, and means for restoring said apparatus to normal condition after a defrosting operation.

4. Refrigerating apparatus comprising a cabinet, a cooling unit in said cabinet, a movable door for said cabinet, means for supplying a cooling medium to said cooling unit, means to regulate the supply of cooling medium to said cooling unit, means including light sensitive means arranged to cause discontinuance of the supply of cooling medium to said cooling unit whenever frost accumulates on said evaporator to a Dredetermined depth, means operative by opening of said door for placing said light sensitive means in operation, means for restoring said apparatus to normal condition after a defrosting operation, means responsive to the condition of said cooling unit for normally controlling the operation of said cooling medium supply means, and manually set means for rendering said light sensitive means inoperative.

5. Refrigerating apparatus comprising a cabinet, a cooling unit in said cabinet, a movable door Jfor said cabinet, means for supplying a cooling medium to said cooling unit, means to regulate the supply of cooling medium to said cooling unit, means including light sensitive means arranged to cause discontinuance of the supply of cooling medium to said cooling unit whenever frost accumulates on said evaporator to a predetermined depth, means operative by opening of said door for placing said light sensitive means in operation, means for restoring said apparatus to normal condition after a defrosting operation, means responsive to the condition of said cooling unit for normally controlling the operation of said cooling medium supply means, manually operable means for adjusting said condition responsive means, and means operated by said manually operable means for rendering said light sensitive means inoperative.

6. Reirigerating apparatus comprising a cooling unit, means for supplying a cooling medium to said cooling unit, energy supply control means for governing the operation of said cooling medium supply means responsive to the temperature of said cooling unit to maintain said cooling unit between predetermined temperature limits, a source of light arranged to direct a light beam across a portion of said cooling unit in position to be interrupted by frost forming thereon, a photoelectric cell positioned to be responsive to said light beam when not interrupted by a frost deposit on said cooling unit, and means under the control of said photoelectric cell for operating said energy supply control means to discontinue operation of said cooling medium supply means when said light beam is interrupted.

'7. Refrigerating apparatus comprising a cooling unit, means for supplying a cooling medium to said cooling unit, energy supply control means for governing the operation of said cooling medium supply means responsive to the temperature of said cooling unit to maintain said cooling unit between predetermined temperature limits, a source of light arranged to direct a light beam across a portion of said cooling unit in position to be interrupted by frost forming thereon, a photoelectric cell positioned to be responsive to said light beam when not interrupted by a frost deposit on said cooling unit, and means under the control of said photoelectric cell for operating said energy supply control means to discontinue operation of said cooling medium supply means when said light beam is interrupted, and means for regulating said energy supply control means to alter the temperature limits maintained by said cooling unit.

8. Refrigerating apparatus comprising a cooling unit, means for supplying a cooling medium to said cooling unit, energy supply control means for governing the operation of said cooling medium supply means responsive to the temperature of said cooling unit to maintain said cooling unit between predetermined temperature limits, a source of light arranged to direct a light beam across a portion of said cooling unit in position to be interrupted by frost forming thereon, a photoelectric cell positioned to be responsive to said light beam when not interrupted by a frost deposit on said cooling unit, and means under the control of said photoelectric cell for operating said energy supply control means to discontinue operation of said cooling medium supply means when said light beam is interrupted, means for regulating said energy supply control means to alter the temperature limits maintained by said cooling unit, and means operated by said temperature limit regulating means for rendering said light sensitive means inoperative.

9. Refrigerating apparatus comprising a cabinet, a door on said cabinet, a cooling unit in said cabinet, means for supplying a cooling medium to said cooling unit, energy supply control means for governing the operation of said cooling medium supply means responsive to the temperature of said cooling unit to maintain said cooling unit between predetermined temperature limits, a source of light arranged to direct alight beam across a portion of said cooling unit in position to be interrupted by frost forming thereon, a photoelectric cell positioned to be responsive to said light beam when not interrupted by a frost deposit on said cooling unit, means under the control of said photoelectric cell for operating said energy supply control means to discontinue operation of said cooling medium supply means when said light beam is interrupted, and means operative to energize said light source and said photoelectric cell when said door is opened.

10. Refrigerating apparatus comprising a cabinet, a door on said cabinet, a cooling unit in said cabinet, means for supplying a cooling medium to said cooling unit, energy supply control means for governing the operation of said cooling medium supply means responsive to the temperature of said cooling unit to maintain said cooling unit between predetermined temperature limits, a source of light arranged to direct a light beam across a portion of said cooling unit in position to be interrupted by frost forming thereon, a photoelectric cell positioned to be responsive to said light beam when not interrupted by a frost deposit on said cooling unit, means under the control of said photoelectric cell for operating said energy supply control means to discontinue operation of said cooling medium supply means when said light beam is interrupted, and means operative to energize said light source and said photoelectric cell when said door is opened, said light source being energized prior to said photoelectric cell.

11. Refrigerating control mechanism comprising means for governing an energy supply, thermostatic means for operating said governing means, means for regulating said thermostatic means having a plurality of regulating positions, defrosting means including a light sensitive frost depth responsive mechanism for operating said energy supply governing means to discontinue energy supply in response to a predetermined depth of frost deposit, and means operated by said regulating means in one position thereof for rendering said defrosting means inoperative.

12. Refrigerating control mechanism comprising a temperature responsive element, energy supply control means operated by said element, and defrosting means comprising means adapted to latch said energy supply control means in energy cut-ofi position, means for moving said energy supply control mechanism to latched position, frost depth responsive means for energizing said last mentioned means, and means operated by said element for releasing said latching means when said element responds to a defrosting temperature.

13. Refrigerating control mechanism comprising a temperature responsive element mounted rigidly at one end by the bias of a resilient element, an energy supply control mechanism, means transmitting controlling movement of the free end of said temperature responsive element induced b-y temperature changes to said energy I supply control means, means for varying the controlling temperature limits of said temperature responsive element, means for latching the free end of said temperature responsive element and Said energy Supply control mechanism in energy shut oil position, means for operating said latching mechanism to latched position, frost depth responsive means for operating said last-mentioned means, and means for releasing said latching mechanism operated by movement of said temperature responsive element against the bias of said resilient element in response to a defrosting temperature condition.

14. Refrigerating apparatus comprising a cooling unit, means for supplying a cooling medium to said cooling unit including a heater and a circulating pump, refrigeration demand responsive means for governing said heater and circulating pump to maintain said cooling unit between predetermined temperature limits, means for altering the temperature limits maintained by said demand responsive means including a fast-freezing controlling position, defrosting means including a light sensitive mechanism arranged to de-energize said heater and circulating pump in response to a predetermined depth of frost deposition on said cooling unit, and means operated by said temperature limit varying means when in fast-freezing position for rendering said light sensitive means inoperative.

l5. Refrigerating apparatus comprising a cooling unit, means for supplying a cooling medium to said cooling unit including a heater and a circulating pump, refrigeration demand responsive means for governing said heater and circulating pump to maintain said cooling unit between predetermined temperature limits, means for altering the temperature limits maintained by said demand responsive means including a fast-freezing controlling position, defrosting means including a normally open relay switch connected to de-energize said circulating pump and heater when closed, means including light sensitive means arranged to operate said relay switch to closed position when a predetermined depth of frost is formed on said cooling unit and a switch connected in series with said relay switch and arranged to be moved to open circuit position by said temperature limit varying means when the same is moved to fast-freezing position.

16. Refrigerating apparatus comprising a cooling unit, means for supplying a cooling medium to said cooling unit including a heater and a circulating pump, refrigeration demand responsive means for governing said heater and circulating pump to maintain said cooling unit between predetermined temperature limits, means for altering the temperature limits maintained by said demand responsive means including a fast-freezing controlling position, defrosting means including a normally closed relay switch connected to de-energize said circulating pump and heater when moved to open position, a thermionic relay in control of said relay switch, light sensitive means arranged to control said thermionic relay in response to variations in the depth of frost deposit on said cooling unit, and means operated by said temperature limit responsive means for short circuitng said relay switch when said temperature limit responsive means is moved to open circuit position.

17. In combination with a refrigerating system of the type utilizing a fuel burner to generate refrigerant vapor, an electrically driven circulating pump mechanism and an evaporator, a temperature responsive means for controlling the supply of fuel to said burner and the energization of said circulating pump to maintain said evaporator between predetermined temperature limits, manually operable means for altering said predetermined temperature limits, and means including a light sensitive control for discontinuing the fuel supply to said burner and the energization of said circulating pump in response to a predetermined depth of frost coat on said;

evaporator.

18. Refrigerating apparatus comprising a cooling element, means for supplying a cooling medium to said cooling element, means for regulating the flow of cooling medium to said cooling element in response to a condition of said cooling element, means for altering the conditions at which said condition responsive means operates said cooling medium supply means, means including light sensitive means operative to cause discontinuance of the supply of cooling medium to said cooling unit in response to a predetermined depth of frost deposit on said cooling unit, said altering means being operable in one position thereof to render said light sensitive means inoperative, said cooling unit being within a refrigerating compartment, a door in said compartment, and means operated by said door for energizing said light sensitive means when said door is in open position.

19. Refrigerating apparatus comprising a cooling element, means for supplying a Cooling medium to said cooling element, means for regulating the iiow of cooling medium to said cooling element in response to a condition of said cooling element, means for altering the conditions at which said condition responsive means operates said cooling medium supply means, means including a light sensitive control means operative to cause discontinuance of the supply of cooling medium to said cooling unit in response to a predetermined depth of frost deposit on said cooling unit, said altering means being operable in one position thereof to rende-r said light sensitive means inoperative, said cooling unit beng within a refrigerating compartment, a door inv said compartment, and means operated by said door for energizing said light sensitive means when said door is in open position, means for maintaining said refrigerant supply means in inoperative condition until the temperature of said cooling unit has risen to a value suflicie-nt to melt frost therefrom.

20. Refrigerating apparatus comprising a cooling unit, means for supplying a cooling medium to said cooling unit, a defrosting means arranged to prevent the supply of cooling medium to said cooling unit, and a light sensitive means in control of said defrosting means arranged to be actuated when a predetermined depth of frost collect-s on said cooling unit.

21. Refrigerating apparatus comprising a cooling unit, means for supplying a cooling medium to said cooling unit, a defrosting means arranged to prevent the supply of cooling medium to said cooling unit, a light sensitive means in control of said defrosting means arranged to be actuated when a predetermined depth of frost collects on said cooling unit, and means whereby said light sensitive means is periodically energized to govern said defrosting means in the event that such predetermined depth of frost has accumulated on said cooling unit.

22. Refrigerating apparatus comprising a cooling unit, means for supplying a cooling medium to said cooling unit, a defrosting means arranged to prevent the supply of cooling medium to seid cooling unit, a light sensitive means in control of said defrosting means arranged to be actuated when a predetermined depth of frost collects on said cooling unit, a door arranged to provide access to said cooling unit, and means operated by said door for governing the energization of said light sensitive means.

23. In a refrigerating mechanism, a cooling unit, a cooling medium supply means, electrical control means for said cooling medium supply means, means for producing non-thermal emissive energy said electrical control means embodying 4and governed by a no-n-thermal emissive energy responsive device so arranged with respect to said cooling unit that a change in the condition of the cooling unit will produce an alteration in the emissive energy received by said emissive energy responsive device from said emissive energy producing means to cause said emissive energy responsive device to govern said control means to control said cooling medium supply means.

24. Control mechanism comprising a movable element for controlling the supply of energy to a refrigerating apparatus, electrical actuating means for operating said movable element, a source of radiant energy and radiant energy responsive means in control of said electrical actuating means adapted to control the operation of said actuating means in response to variations in radiant energy received thereby.

25. In combination with the cooling unit of a refrigerating apparatus, means for controlling the operation of said cooling unit, means for actuating said control means, a source of radiant energy and a radiant energy responsive mechanism for governing the operation of said actuating means so related to said cooling unit that the radiant energy received by said radiant energy responsive mechanism is a function of a condition of said cooling unit whereby said controlling means controls said cooling unit in accordance with said condition thereof.

26. In combination with the cooling unit of a refrigerating apparatus, means for controlling the operation of said cooling unit, means for actuating said control means, an emissive energy responsive mechanism for governing the operation of said actuating means, a source of emissive energy arranged to subject said emissive energy responsive mechanism to energy emitted thereby, and said source of emissive energy, said emissive energy responsive mechanism and said cooling unit being so arranged With respect to each other that the emissive energy received by said emissive energy responsive mechanism is a function of a condition of said cooling unit whereby said cooling unit is controlled by a condition thereof.

27. In combination with the cooling unit of a refrigerating apparatus, means for controlling the operation of said cooling unit, means for actuating said control means, an emissive energy responsive mechanism for governing the operation of said actuating means, an intermittently operable source of emissive energy arranged to subject said emissive energy responsive means to energy emitted thereby, and said source of emissive energy, said emissive energy responsive mechanism and said cooling unit being so arranged with respect to each other that the emissive energy received by said emissive energy responsive mechanism is a function of a condition of said cooling unit whereby said cooling unit is controlled by a condition thereof.

28. In combination with a refrigerating device including a cooling unit, a control mechanism for controlling said cooling unit including an actuating element arranged to govern the functioning of said device, means for operating said actuating element, impulse responsive means arranged to control said operating means in response to impulses received thereby, impulse generating means, and said control mechanism being constructed and arranged to shield said impulse responsive means from impulses produced by said impulse generating means when said cooling unit is in a predetermined condition.

29. That method of controlling the operation of a refrigerating system of the type involving a cooling unit and a source of supply of cooling medium therefor which includes the steps of controlling the operation of the cooling medium supply means by an impulse responsive mechanism, subjecting the impulse responsive mechanism to the action of controlling impulses and shielding the impulse responsive mechanism from said impulses in response to a condition of the cooling unit to govern the operation thereof.

30. In combination with refrigeration apparatus having a control governing the operation thereof, said control including an energy transmitter, an energy receiver mechanically independent of said transmitter but operative in response to energy received therefrom, means responsive to a condition of said refrigeration apparatus for modifying the eiectiveness of said transmitter to control said receiver, and means responsive to the operation of said receiver to actuate said governing control for the refrigeration apparatus.

31. In combination with refrigeration apparatus having a control governing the operation thereof, a governing means including an energy transmitter and an energy receiver mechanically disassociated from one another, said energy receiver being operatively connected with said ccntrol to actuate the same as the result of variations in energy received from said transmitter, said refrigeration apparatus, said energy transmitter and said energy receiver being so constructed and arranged that variations in a condition of said refrigeration apparatus will produce variations in the energy received by said energy receiver whereby to control said apparatus.

32. Refrigerating apparatus comprising a cooling unit, means for supplying a cooling medium to said cooling unit, light sensitive meansa source of light for directing light upon said light sensitive means, control means arranged to regulate the operation of said cooling medium supply means When said light sensitive means responds to a variation in the light impinging thereupon, said apparatus being so constructed and arranged that the light impinging upon said light sensitive means is varied in accordance with a condition of said cooling unit.

33. Refrigerating apparatus comprising a cooling unit, means for supplying a cooling medium to said cooling unit, light sensitive means, a

lsource of light for directing light upon said light sensitive means, control means arranged to regulate the operation of said cooling medium supply means when said light sensitive means responds to a variation in the light impinging thereupon, said apparatus being so constructed and arranged that the light impinging upon said light sensitive means is varied in accordance with a condition of said cooling unit, a door arranged to provide access to said cooling unit, and means under the control of said door for governing the energization of said light sensitive control means.

ARNOLD D. SIEDLE.

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