US2034620A - Refrigerator controller - Google Patents

Description

REFRIGERATOR C ONTROLLBR Filed March 5, 1932 2 Sheets-Sheet 1' jrql;

WITNESS INVENTOR A'ITORN EYS March 17, 1936. 1.. c. IRWIN 2,034,620

REFRIGERATOR CONTROLLER Filed March 5, 1932 2 Sheets-Sheet 2 W ITN ESS INVENTOR LAWRENCE /f?W//V ATTORN EYS Patented Mar. 17, 1936 UNITED v STATES PATENT OFFICE 12 Claims.

The present invention relates to automatic refrigerators of the gas and electrically operated types and has for its general object 'to provide an improved temperature controller by means of which the refrigerator can be set for defrosting and yet remain under the control of the temperature control mechanism whereby an excessive rise of the temperature in the refrigerator with consequent spoilage of food in the latter, is automatically prevented and, in the case of electrically dn'ven machines, an overload on the motor and danger of burning of the motor windings are likewise prevented.

During the normal operation of automatic refrigerators, particularly household refrigerators, a coating of ice gradually accumulates upon the evaporator or expansion coil and ultimately becomes so thick as to interfere with the mainte nance of the desired low temperature. The usual method of removing such ice coating, 1. e., of defrosting the refrigerator, is to cut oil the supply of gas or to stop the motor by shutting off the current, whereupon the temperature of u the refrigerant (ammonia, methyl chloride, sulfur dioxide, or other fluid) begins to rise. If, in the case of electrical refrigerators, the motor is kept inoperative for only such a length of time as is necessary to efiect the defrosting, it can be turned on again without danger of overloading the same, as the refrigerant will still be at a low temperature, and when the switch is thrown the motor will start without any diiilculty.

In many cases, however, the housewife or other attendant forgets to re-start the motor,

or to turn on the gasagain, at the end of the defrosting period, so that the temperature of the refrigerator, and hence of the refrigerant, continues to rise and may even reach room temperature. This increase in temperature is chjectionable because it not only permits the food to spoil, but, in electrical refrigerators, causes increase in .the vapor pressures on both sides of the compressor, so that when the current is again turned on, an excessive load is placed on the motor which is sometimes large enough to burn out the winding. Similarly, in the case e of gas refrigerators, an excessive load is placed on the boiler. The danger of burning out the motor is all the more imminent since, for reasons of economy, it is the practice to employ a motor of the lowest possible capacity for operating the compressor. Due to this fact it has become almost essential to introduce an overload cut out in combination with the temperature control of an electrically operated refrigerator, the purpose of the cut out being to break the electric circuit when the load on the motor is so great as to demand a current which would burn out the motor windings.

It is an object of the present invention to pro- 5 vide an improved temperature control mechanism whereby, when the refrigerator is set for defrosting, the control of the temperature of the refrigerator is maintained up to defrosting temperature and the temperature kept at such 10 point. The temperature. control mechanism thus remains operative even when the parts are set for defrosting and prevents rise of the tem perature beyond the defrosting point, and hence prevents spoilage of the food kept in the refrig- 5 erator even if the attendant should forget to reset the controller for a colder temperature. According to the invention, therefore, an improved temperature control mechanism for an automatic refrigerator is provided whereby the tem- 20 perature of the same may be adjusted and controlled throughout the whole range from the minimum temperature usually employed in refrigerators to the defrosting temperature. It is a further object of the invention to provide a 25 temperature control mechanism for refrigerators which is so constructed that adjustment thereof throughout the whole range of. control from the coldest to at least the defrosting temperature can be effected within a single revolu- 30 tion of a knob or pointer, which can therefore be made to cooperate with a dial having thereon the legends Colder and Defrost or their equivalents. Other objects of theinvention will become apparent from the following description 35 and the features of novelty will be set forth in the appended claims.

The accompanying drawings illustrate by way of example a control mechanism for electric refrigerators having my invention embodied there- 40 in. In said drawings,

Fig. 1 is a plan view, with the casings in section, of my improved temperature control mechanism;

Fig. 2 is a side view of the same; and 45 Fig. 3 is an end or face view showing the teml perature control knob and associated dial.

Fig. 4 is a conventional form of an electric refriegrator showing the control mechanism connected therewith.

In the mechanism illustrated, the temperature within an electrically operated refrigerator is maintained with the aid of a temperature-responsive switch mechanism which controls the circuit of the motor of the compressor and op- 56 crates to start the motor when the temperature in the refrigerator rises above a maximum, predetermined by the setting of the mechanism, and to disconnect the motor when the temperature reaches a predetermined minimum. Referring to Fig. 4, illustrating a conventional form of electric refrigerator, A designates an electric motor, which through a belt connection drives the pulley of a compressor B, which withdraws expanded refrigerant through suitable piping from an evaporator C located in the refrigerator cabinet E. The gaseous refrigerant is compressed by the compressor B and then passes through suitable pipes to a condenser D in which the refrigerant is liquefied. The action of the compressor forces the liquid refrigerant through suitable piping to the evaporator C, as is well understood in the art. This temperature-responsive mechanism may be of the type disclosed in the Frank J. Bast, Patent No. 1,905,788, the essential features of which are illustrated in Figs. 1 and 2 of .the drawings. It will, however, be understood that my invention is equally applicable to the control of the flow of gas to a gas-operated refrigerator, and may readily be embodied in a temperatureresponsive valve regulator, such as is described in the copending application of Frank J. Bast,

Serial No. 424,768.

As shown, the control mechanism includes a thermostatic bulb l0 containing an expansible fluid and adapted to be positioned at a suitable place in the refrigerator against the evaporator C, such bulb being connected with an expansible member, such as a capsular spring or bellows H disposed within a casing 2 attached in any suitable manner, as by screws l3, to the main casing M of the instrument. A rod l 5 is connected with I the bellows H to be moved thereby and projects into the interior ,of easing M where its pointed end passes through a tapered opening in the upper horizontal arm of a channel or U-shaped yoke 96 and engages one of a pair of plates l1, 88 arranged to operate as a toggle, the beveled sides of the end of the rod bearing against the walls of the opening so as to move the yoke as the bellowse'xpands. The two plates engage each other along a knife edge 89 and are provided with knife edges at their outer ends wherewith they engage resilient supports 20 mounted upon a base 2i bearing against knife edges 2|a and fixed to the casing 84 by adjustable screws 2lb. The plate I! is provided with an offset finger 22 which engages in an opening in support 20 and serves to limit the movement of the toggle I1, l8 in both directions.

The expansive movement of the bellows H is opposed bya spring 23 which actuates a rod 25 whose pointed end engages the side of the plate I! opposite that engaged by the rod l5. The rod 24 is in screw-threaded engagement with a plate 25 forming part of the yoke l6 and is provided with a nut 25' rigid therewith and by rotation of which the rod may be adjusted. The other end of spring 23 rests upon a plate 26 against which bears a screw 21 which is adjusted longitudinally by means of a nut 28, fixedto a rotatable knob or pointer 29 located outside of the casing and cooperating with a dial 30.

The yoke l 6 is supported at a distance from the rear wall of the casing M by means of a channelshaped bracket lBa fixed to the said rear wall, said bracket pivotally supporting between its forwardly extending arms a channel-shaped member I612. The yoke I6 is provided with lateral ears I60 and is pivotally associated'with the mem- 'erator is set for a colder temperature.

ber I6b by means of a pin id, and as the total movement of the yoke is only about one-eighth of an inch, the arc traversed by the pin Hid may be regarded as a straight line, the yoke being thus guided in a practically vertical movement.

To the shorter plate l8 of the toggle ll, I8 is attached a resilient arm 3| carrying a jumper 32 adapted to bridge a pair of terminals 33, 34 located in the circuit of the motor (not shown) of the refrigerator, as explained more in detail below. By rotation of the pointer 29 in a clockwise direction (Fig. 3) the tension of the spring 23 is decreased, and thereby the temperature at which the bellows I I causes the toggle I1, Hi to snap downwardly to close the terminals 33, 34 to start the motor is reduced; in other words, the refrig- Movement of the pointer in the opposite direction, on the other hand, increases the resistance of spring 23, and a higher temperature must be reached in the refrigerator before the switch arm 3| is thrown to close the terminals 33, 34.

In accordance with the present invention I make it unnecessary to open the switch 32, or any other switch in the circuit of the motor, in order to effect defrosting of the evaporator or expansion coil. I have found that the control range of the temperature control mechanism may be so enlarged and that the latter may be so constructed that the same may be set to a defrosting temperature so as automatically to bring the temperature in the refrigerator to such temperature. The temperature in the refrigerator is thus kept under constant control up to the defrosting temperature, and rise in temperature to the point where the food begins to spoil and where, upon starting of the motor, such a large current might surge therethrough as to endanger its windings, is prevented. In the preferred form of the invention, I so proportion the strength of the bellows H and spring 23, and the pitch of the screw 21 that, in spite of the increase in the control range, the whole range of temperature control from the minimum cold temperature to the defrosting temperature is traversed in the course of a single revolution, or slightly less than a single revolution, of the pointer 29. It is thus possible to have the pointer 29 coact with a dial upon which are marked the words Colder,

to indicate the position of the pointer for minimum or sub-normal temperatures in the refrige erator, ,Normal for medium cold temperatures, at both of which, as is well understood, ice or frost accumulates on the evaporator, and Defrost for temperatures sufflciently high to cause the deposit of ice or frost to melt away, and yet not so high as to cause the food to spoil or to overtax the motor when the latter is started. It will be understood that these legends may be replaced by other and equivalent legends. I have found that if the parts are made as follows, the temperature control mechanism can be set to any temperature within the desired range of control in less than 360 of movement of the pointer 29: The screw 27 may be constructed as a triple thread screw of inch pitch, i. e. one revolution of the screw produces a longitudinal movement of inch. 'It will be understood that as a stop is normally provided for the pointer, the latter moves through less than 360, say about 300. The spring may be made of 0.108 inch diameter 0.95% carbon steel wire with an elastic limit of about 160,000 lbs. per square inch. The spring is composed of six coils of 3?; inch diameter, 1% inch free length and a compression movement of inch with a dead load of 17 lbs. The bellows material may be of bronze of 0.006 inch wall thickness, 11 convolutions, 1% inch outside diameter, and with an effective area of 0.6 square inch. The amount of movement of this bellows required to cause snapping or throwing of the switch arm 3| is about); inch. 2 lbs. are required to corn press it 5inch and 2 lbs. internal pressure to expand it 3! inch. The snap mechanism is adjusted to require a pressure of- 4 lbs. to snap it in either direction. The fluid employed in the thermostatic bulb i0 and bellows Ii is methyl chloride which has a vapor pressure of 9 lbs. at 9 F. and 36 lbs. at 48 F.

The above dimensions apply for a temperature control range from 9 to 48 F. If it is desired to change the range to from 9 to 38 F., it is necessary only to change the spring. In such case the spring is made of the same steel as above but is 0.095 inch in diameter, the spring being again composed of six coils of 1% inch diameter, is 1% inches in length, and has a compression movement of A inch with a dead weight of 11 lbs. In both instances the difference in temperature required to snap the mechanism from an On" to an Off position is about 8 F. either p at the low or high temperature setting.

The parts are, in general, so constructed-that when the knob 29 is turned to the extreme right, i. e. its coldest position, the temperature of the refrigerator ,will be maintained between and F., at which time the temperature in the expansion or refrigerating coil is much lower, probably between 10 and 20 When the control is set to a normal position, the temperature in the food chamber will be between 40 and F.; and when it is set to defrosting position, the temperature will be between 45 and F. In

the latter case the temperature inthe evaporator will be slightly above 32 R, which will permit defrosting while at the same time the temperature inth food chamber is kept from rising so high as cause the foodie-spoil.

Suitable stop mechanism is preferably provided so as to prevent-the knob 20 from being turned past the desired limits of movement. In the form of the dnvention illustrated, the central innor portion} of the knob 29 is hollowed out, as indicated at 35, and is provided with a projecting lug 36 which is adapted to engage a stop 31 located on the casing 14 and extending into the path of movement of the lug.

In the case of a control mechanismfor a gasoperated refrigerator, such as the mechanism shown in the patent to Bast, No. 1,801,300, issued April 21, 1931, a complete traversal of the temperature range from the coldest to the defrosting temperature within about 300 of movement of the pointer of the adjusting screw may be obtained by constructing the parts as follows: The flexible walled expansible casing (28) is made of 0.022 inch thickness spring tempered phosphor bronze of 2% inch diameter. The movement of this casing by internal vapor pressure is approximately 0.001 inch per degree, F. The adjusting screw (34) is left-handed and of pitch. The

fluid in the expansible casing is propane, which has a vapor pressure of 27 lbs. at 9 F. and 76 lbs. at 48 F.

As will be seen from the above, I have provided an arrangement wherein the control devices of the refrigerator may be set for defrosting without permanently disconnecting the motor from the source of power, orthe burner (in a gas refrigerator) from the gas supply, while at the same time the temperature of the refrigerator remains under the control of the temperature control mechanism, so that the danger of the temperature rising to the point at which the food begins to spoil is averted. The refrigerator can thus be set for defrosting whereby it attains a temperature sufliciently high to melt away the deposit of ice or frost on the evaporator while at the same time the rise of the temperature to too high a value is rendered impossible by the tem perature control mechanism, so that even if the housewife or other attendant should forget to restore the setting to a lower temperature, the food still will not be spoiled. It will also be clear that the vapor pressure of the refrigerant is kept low and prevented from rising to the point at which, upon setting the refrigerating system into operation, the latter is subjected to an excessive load."

With my improved mechanism, therefore, the

controller may be set for quick freezing, normal and defrosting temperature ranges, the motor at each of such ranges being cut in when the upper limit of such range is reached, and being cut out when the temperature. has fallen to the lower limit of such range, an average refrigerating tem= perature being maintained which is abnormally cold, normal, or is high enough to efiect defrost= ing. In each position of the knob, the motor or equivalent mechanism will thusbe alternatingly switched on and off, the apparatus continuing to directions, so that upon further rotation of the I member 29 in a counter-clockwise direction (Fig. 3) the controller may be set for higher and higher temperatures up to the maximum controlled de frosting temperature.

While in'the preferred formof the invention the pointer 29 is directly connected with the screw 21 so that the latter accomplishes the same angular movement as the pointer, it is within the scope of the present invention to arrange a speed reduction gearing between the pointer and screw such that the latter is displaced angularly to a greater extent than the pointer. If desired, the pointer may be replaced by a. slidable rack which meshes with a pinion associated with the screw. Other variations from the specific form of the invention ilustrated may be resorted to within the scope of the appended claims without departing from the spirit of the invention.

It will be obvious that the bellows II can be arranged to be responsive directly to the pressure at any part of the refrigerant circuit, and I wish it to be understood that where in the claims I speak of a temperature-responsive mechanism, such expression embraces also mechanism responsive to the pressure at a selected place.

I claim: I 1

1. In a refrigerating system, the combination of a cabinet, an evaporator for absorbing heat from the cabinet, an intermittently operated refrigerating machine for circulating refrigerant through the evaporator and a mechanism adjustable to a series of positions for efiecting continuous cycling of the machine at progressively increasing mean evaporator temperatures, the maximum mean temperature obtained by continuous cycling being effective to remove frost from the evaporator which has accumulated thereon at the lower mean evaporator temperatures.

2. In a refrigerating apparatus for preserving food-stuffs, the combination of a refrigerator cabinet, a cooling unit in the cabinet for absorbing heat therefrom, a refrigerating mechanism for circulating a refrigerant through the cooling it, and a control mechanism for the refrigera ing mechanism including means to effect cycling of the mechanism to maintain the cooling unit at relatively lowrefrigerating temperatures, whereupon frost i ncidentally accumulates on the cooling unit, and also including means to effect continuous cycling of the mechanism to maintain a relatively higher refrigerating temperature in the cooling unit sufiicient to remove or to retard the accumulation of frost on the cooling unit, said latter temperature being sumciently low to preserve food-stuffs.

3. In a refrigerating apparatus for preserving food-stuffs, the combination of a refrigerator cabinet, a cooling unit in the cabinet for absorbing heat therefrom, a refrigerating mechanism for circulating a refrigerant through the cooling unit, and a controlmechanism for the refrigerating mechanism including means to effect cycling of the mechanism to maintain the cooling unit at relatively low refrigerating temperatures, whereupon frost incidentally accumulates on the cooling unit, and also including means to efiect continuous cycling of the mechanism to maintain a relatively higher refrigerating temperature in the cooling unit suficient to remove or to retard the accumulation of frost on the cooling unit, said latter temperature being sufficiently low for preserving food-stuffs and common means manually operable for obtaining either condition of operation of the refrigerating mechanism.

4. In a refrigerating apparatus for preserving food-stuffs, the combination of a refrigerator cabinet, a cooling unit in the cabinet for absorbing heat therefrom, a refrigerating mechanism for circulating a refrigerant through the cooling unit, and a control mechanism adjustable to a plurality of positions for cycling the mechanism to maintain the cooling unit at varying relatively low mean refrigerating temperatures, whereupon frost accumulates on the cooling unit, said control mechanism also having at least one additional position of adjustment to effect continuous cycling of the mechanism to maintain a relatively high mean refrigerating temperature in the cooling unit sufficient to remove or retard the accumulation of frost on the cooling unit, said latter temperature being sufficiently low for preserving food-stuffs.

5. In a refrigerating apparatus for preserving food-stuffs, the combination of a refrigerator cabinet, a cooling unit in the cabinet for absorbing heat therefrom, a refrigerating mechanism for circulating a refrigerant through the cooling unit, a control mechanism adjustable to a plurality of positions for cycling the mechanism to maintain the cooling unit at varying relatively low mean refrigerating temperatures, whereupon frost accumulates on the cooling unit, said control mechanism also having at least one additional position of adjustment to effect continuous cycling of the mechanism to maintain a relatively high mean refrigerating temperature in the cooling unit sufficient to remove or retard the accumulation of frost on the cooling unit, said latter temperature being sumciently low for preservingfood-stuifs, and manually adjustable means included in the control mechanism for obtaining either the relatively high or the relatively low refrigerating temperatures in the cooling unit.

6. The method of operating a refrigerator for preserving food-stuffs, which refrigerator has a cooling unit in its cabinet maintained at a refrigerating temperature by a cyclically operated refrigerating machine, which method comprises normally cycling the refrigerating machine to maintain a relatively low, refrigerating temperature in the cooling unit and incidentally accumulating frost on the cooling unit and continuously cycling the machine periodically to maintain a relatively higher refrigerating temperature in the cooling unit, which latter temperature is sufiiciently high to effect defrosting of the evaporator and sufliciently low for preserving food-stuffs.

7. In a refrigerating apparatus, in combination, an indicator having several temperature values indicated thereon, said temperature values representing normal, sub-normal and defrosting conditions, a single manually-operated member movable at will with respect to said indicator to adjust said member with respect to one of said indications carried by the indicator, a continuously cyclically operating refrigerating system, including an evaporator, means for circulating refrigerant through the evaporator, and a control member, said control member being adapted to expand or contract under temperature changes in the refrigerator, a switch having connection with said circulating means, said switch having connection with said control member and being adapted to cause actuation of said circulating means through expansion movement of said control member, pressure-exerting means acting upon said control member to resist expansion thereof and normally tending to collapse the control member, a movable connection between said manually-operated means and said pressure-exerting means to change the tension of said pressure-exerting means in predetermined relation as the manual operating means is moved with respect to said indicator indications, the movement of said manually-operated means to normal and sub-normal positions increasing the tension on said pressure-exerting means to establish temperatures at which frost accumulates on the evaporator, and the movement of said manually-operated means to the defrosting position decreas- 4 ing the tension on said pressure-exerting means to establish temperatures at which frost melts on said evaporator.

8. In a refrigerating apparatus having an evaporator and means for circulating refrigerant through the evaporator, a switch, a thermo-responsive element, mean's under the control of said element for opening and closing the switch to produce operation of the switch at selected temperature ranges, including settings for normal, sub-normal and defrosting temperatures, modifying means for modifying the operation of the switch-operating means to selectively produce a predetermined lower or higher switch-operating temperature than the predetermined normal temperature, readily accessible means connected with said modifying means for operating said modifying means, indications, associated with said readily accessible means, signifying normal, sub-normal and defrosting positions of said modifying means, said readily accessible means being selectively adjustable to an indication corresponding to the selected temperature range, said readily accessible means, upon such an adjustment, controlling the modifying means and said switch to produce the temperature range indicated by the adjusted readily accessible means, said readily accessible means being in fixed adjustable relation to said indications and provided with a surface for hand-manipulation of said modifying means to a predetermined position, said thermoresponsive element being arranged to effect continuous cycling of the refrigerator during each of the several selective operations, viz. normal, sub-normal and defrosting, and during the de frosting operation to maintain a temperature condition within the refrigerator below that at which food spoils.

9. In a refrigerating apparatus, in combination an indicator having several temperature values indicated thereon, said temperature values representing normal, sub-normal and defrosting conditions, a single manually-operated member movable at will with respect to said indicator to adjust said member with respect to one of said indications carried by the indicator, a continuously cyclically-operating refrigerating system, including an evaporator, means for circulating refrigerant through the evaporator, and a control member, said control member being adapted to expand orcontract under-temperature changes in the refrigerator, said control member including an expansible and contractible metallic chamber, containing a temperature-sensitive fluid, a switch having connection with said circulating means, said switch having connection with said control member and being adapted to cause actuation of said circulating means through expansion movement of said control member, pressure-exerting means acting upon said control member to resist expansion thereof and normally tending to collapse the control member, a movable connection between said manually-operated means and said pressure-exerting means to change the tension of said pressure-exerting means in predetermined relation as the manual operating means is moved with respect to said indicator indications, the movement of said manually-operated means to normal and sub-normal positions increasing the tension on said pressureexerting means to establish temperatures at which frost accumulates on the evaporator, and

the movement of said manually-operated means to the defrosting position decreasing the tension on said pressure-exerting means to establish temperatures at which frost melts on said evap orator.

10. In a refrigerating apparatus as set forth in claim 9, in which the pressure-exerting means comprises a spring, a connection between said spring and said manually-operated means, said control member, spring, and connection being axially aligned.

11. In a refrigerating apparatus as set forth in claim 9, in which the pressure-exerting means comprises a spring, a connection between said spring and said manually-operated means, said control member, spring, and connection being axially aligned, said switch including a contactcarrying member pivoted at one side of the common axis, its free end extending to a point beyond the common axis, said free end being subject to the conjoint influence of said control member and spring.

12. In a refrigerating system, the combination of a cabinet, an evaporator for absorbing heat from the interior of the cabinet, means connected to said evaporator for withdrawing heat from said evaporator, a control device including an expansible device and compression means opposing the movement of said expansible device, means for varying the effective force of said compression means, including a manipulating member movable to a plurality of selected positions, said control device in all of the selected positions of said manipulating member being operative to continuously cycle the first named means by starting and stopping the first named means between high and low temperature limits and in at least one of the selected positions of the manipulating member being operative to continuously cycle the first named means by starting the first named means at a temperature above the melting point of frost, and in at least one of the selected positions of the manipulating member being operative to start the first named means at a temperature below the melting point of frost, means preventing the movement of said manipulating device substantially above or below the selected positions, and means whereby said compression means may be varied independently of said manipulating device.

LAWRENCE C. IRWIN.

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