US2068249A - Control apparatus - Google Patents

Description

Patented Jan. 19, 1937 PATENT OFFICE coN'rnoL APPARATUS Matson C. Terry, Detroit, Mich., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa.,

Pennsylvania a corporation o! Application October 3, 1932, Serial No. 636,087

8 Claims.

My invention relates to control apparatus, and particularly to control apparatus for effecting defrosting of the heat absorbing elements of me- Cil chanical refrigerators.

In mechanical refrigerators, especially of the domestic type, the accumulation of frost on the cooling unit has long been a problem because frost impairs the transfer of heat between the air ywithin the refrigerator and the cooling unit. Furthermore, an excessive accumulation of frost on the evaporator may interfere with the removal. of the vice trays located within the evaporator.

The usual way of accomplishing defrosting of the evaporator is to manually throw a switch to stopv the operation of the refrigerating unit` until Y the frost has melted oif the evaporator. Automatic devices have also been provided for periodically interrupting the supply of current to' the refrigerator so as to halt the `operation of Y the refrigerating unit temporarily.

All of the foregoingl schemes are objectionable in that the defrosting action may require consderable time, so much so that the frozen foods or icein the evaporator areapt to be' softened or melted and, furthermore, because the box temperature may be higher than is found desirable. In addition, the manually operated process is open to the objection that it requires considerable attention on the partof the user and to the objection that the user may for-get to restart the mechanism, and as a consequence, spoil the food in the refrigerator box.

Other automatic and semi-automatic defrosting schemes have been `provided wherein, for example, electric heaters are utilized to melt the frost on the evaporator but, all of such schemes entail such mechanical and electrical complication as to be undesirable.

With my invention, I eifect defrosting of the evaporator by periodically permitting relatively hot refrigerant condensate as well as the refrigerant vapor discharged by the compressorof the refrigerator unit to enter the evaporator; the heat of the condensed refrigerant coupled with thev amount of heat effected by the vapor circulated throughthe system, which vapor condenses in the evaporator, effectsaveryrapidmelting of the frost on the evaporator, the time in terval being so short that congealedV food articles housed within the evaporator are not melted and the temperature of the food compartment chamv,ber is not unduly raised.

7 At the outset of the defrosting cycle the circulated vapor obtains some of its heat from the stored heat of the motor, compressor, condenser, etc., and during the remainder of the cycle the circulated vapor obtains heat due to the motor inelciency and from the compressor friction.

It is an object of my invention, therefore, to provide an automatic or semi-automatic defrosting device for a mechanical refrigerator which shall be of less expensive construction and more reliable than the devices of this connection heretofore provided and which melts the frost on the evaporator with such rapidity as to avoid melting of the frozen food stuffs housed within the evaporator and to .prevent undue rise in the food compartment temperature because of the defrosting feature.

` These and other objects are eifected by my invention as will be apparent from'the following description and' claims taken in connection with the accompanying drawing, forming a part of this application, in which:

Fig. 1 is a diagrammatic view of a refrigerating system containing one embodiment of vmy defrosting device;

Fig. 2 is a diagrammatic view of a portion of a refrigerating system such as shown in Fig. 1 and illustrates a second embodiment of my invention;

Fig. 3 is a diagrammatic showing of a refrigerating apparatus containing another embodiment of my invention; and,

Fig. 4 is av diagrammatic view of the timing mechanism shown in Figs. l and 2.

Although I have shown myinvention as applied to a high side float controlled flooded compression system, it is obvious that my invention may be applied to any system having means for developing refrigerantvapor under pressure, a heat absorbing unit and areasin which the refrigerant per seis normally subject to` a relatively high pressure, and other areas where it is normally subject to a relatively low pressure.

Referring new to Figs. l and 4 for a detailed description of the first embodiment, of my invention, there is shown, diagrammatlcally, a con- Y Throughthe valve 1, liquid refrigerant rate and in a relatively small quantity, preferably to the bottom of an evaporator 8 through a conduit 9, wherein it is vaporized because of the low pressure maintained therein by the compressor I, and the heat present in a cooling compartment II in which the evaporator is disposed. The vapor is then drawn back to the compressor through a conduit I2. The vaporization -of refrigerant in the cooling unit 8 cools the food compartment II. The operation of vthe compressor is intermittent and is controlled by a 'thermostat I3 which operates contact means I4 in supply line I5, the action of the thermostat I3 being responsive to cooling unit temperatures in a manner well understood in the art.

For the sake of clearness, the condenser 4 and conduits 3 and 6 are hereinafter referred to as the high side of the system since a normally high pressure obtains therein, while the evaporator or heat absorbing unit 8 and conduits 9 and I2 are termed the low side of the system since normally a relatively low pressure obtains therein. The compressor I and the float valve 1 define the high and low pressure portions of the system.

In order to remove frost from the cooling unit 8 and to prevent substantial accumulation of refrigerant to flow to the cooling unit 8.

frost, the float controlled valve 1 is constructed in the following manner. A main casing I6 of any suitable material is provided, and a nonmagnetic cap I1 is disposed preferably on the top of the casing I6. A iioat ball I8 is contained in the casing I6 and is connected through suitable links and levers to the valve 1, which has a seat I9, in such a manner that when the oat I8 rises due to accumulation of liquid refrigerant in `the casing IB, the valve 'I is opened and allows liquid Attached to the upper portion of the float I8 is a magnetic plunger 2| which extends partly into the non-magnetic cap I1.

A coil 22 is disposed around the cap I1 in such a manner that, when the coil is energized, the plunger 2| is pulled upwardly thus raising the ioat I8, opening the valve 'I, and placing the high and low sides of the system in unrestricted communication with each other.

In order to accomplish automatic defrosting rapidly, the coil is connected through leads 23 to a switching and timing device 24, as fully illustrated in Fig. 4. The switching and timing device 24 is set to energize the coil 22 at predetermined times, at which times the valve 'I is opened and warm liquid refrigerant ows from the oat casing I6 and the condenser 4. As is hereinafter described, the valve 1 is kept open for a su'icient length of time to allow the condenser pressure to drop considerably, whereupon, if the compressor I is running, vaporous refrigerant pumped by the compressor will not be condensed but will be forced in the Vapor state directly to the cooling unit 8, preferably entering the bottom thereof to ensure complete circulation of the noncondensed refrigerant. Because of the low temperature of the cooling unit 8 and the refrigerator cabinet I I and also due to the increased pressure in the cooling unit 8 the refrigerant is at least partially condensed in the cooling unit thus giving up its latent heat of condensation to the cooling unit and also its sensible heat which has been obtained from the motor 2 and compressor I. Since the same amount of refrigerant is evaporated in the cooling unit as is condensed therein, the latent heats of evaporation and condensation balance so that the heat actually given up to the cooling unit is the sensible heat contained in the non-condensed refrigerant vapor which is delivered thereto.

condensed vapor delivered to 4the 4cooling unit 8 is condensed therein. However, as the temperature of the cooling unit rises some of the vapor does not condense in the cooling unit- 8 but, since it enters at the bottom of the cooling unit 8, bubbles through the liquid contained therein neither condensing nor evaporating and the vapor is thereafter drawn directly back to the compressor I. However, most `of the sensible heat of the vapor which bubbles through the liquid in the cooling unit 8 is given up to the cooling unit. The cooling unit 8 is therefore heated rapidly and frost is quickly melted. After a predetermined time the coil 22 is deenergized by the timing and switching device 24 whereupon the refrigerating apparatus is returned to its normal operation with the restricted connections 1, I9

dividing the system into high and low sides.

It will be noted that, if the compressor I is not operating when the coil 22 is energized, as soon as warm liquid refrigerant from the condenser 4 flows to the cooling unit 8, the thermostatic control |3 will operate to close contacts I4 and start the motor 2 which drives the compressor I. Positive delivery of non-condensed refrigerant to the cooling unit 8 is therefore assured. As shown in Fig. 1, the thermostatic element is generally, although not necessarily, placed in metallc contact with the evaporator 8.

Before explaining the specific operation of the timing and switching device 24, it is well to explain that the amount of frost accumulating on the cooling units of mechanical refrigerators in a given time depends largely on the humidity of the ambient atmosphere, the amount of moisture contained in the articles placed in the refrig= erator cabinet, the temperature ofthe cooling unit and the amount of air circulation in the,

food compartment and over the cooling unit.

Since all these factors are variable with there- The timing device, on the other hand, mus't.

maintain the connection between the high and low sides of the system in an unrestricted condition for a long enough time to allow non-condensed refrigerant to be forced to the low side,

and therefore a predetermined minimum setting i must be provided which varies with each type and size of refrigerator.

The timing device is therefore equipped with a minimum setting, preferably arranged at the factory, and an adjustable upper time limit de vice which may be adjusted by the user. Since the defrosting cycle slightly increases the overall current consumption, it is preferable to have the timing device set to initiate defrosting not more than once every twenty-four hours, and the upper time limit setting will, of course, vary with the frequency of defrosting'.

Turning now to a detailed description of my timing and switching device 24, numeral 25 designates small clock motor of conventional design, the movement of .which is reduced through a gear chain 26 and which finally rotates a wheel 21. A radial slot 28 is cut out of the wheel 21 and a projection member 29 slides in the slot.

A small screw 30 is provided on the member 29A At the beginning of. the defrosting cycle substantially all of the nonto hold it in the position desired in the slot 28. Disposed adjacent to the wheel 21 is a bell-crank lever 3l disposed movably on a trunnion 32 and extending in two directions therefrom. A contact 33 is disposed on an end 3|a of the bellcrank lever 3| and a second contact 34 is adapted to be engaged by the rst contact 33. A helical spring 35 anda stop 36 maintain the lever 3| in its operating position. The contacts 3'3 and 34 are connected to a coil (not shown) by leads positioned as shown in Figs. 1 and 2 which, when energized, starts the defrosting period and when deenergized stops the defrosting period.

The operation of the device is as follows: The projecting member 29 is rotated by the clock device 25 and once in every revolution, which is preferably not more than once a day, it contacts with end 3|bof the bell-crank lever 3|, thus turning the lever about the trunnion 32, overcoming the force of the helical spring 35 and closing the contacts 33 and 34. The projection 29 maintainsits engagement with the lever 3| for a period of time `above a certain minimum which is determined by the distance of the inner end of the slot 28 from the center of the wheel 21, the projection 29 being set in the slot 28. When the projection 29 is at its innermost position, the contacts are closed for the least period of time; as the projection 29 is moved outwardly in the slot 28, the period of time the contacts 33 and 34 engage increases since the projection 29 engages the end 3|b of the lever 3| for a longer time.

It is apparent that, by sliding the adjustable projection 29 in the slot 28, the time between closing and opening the contacts 33 and 34 and energizing and, deenergizing the coil (not shown) may be varied within certain limits, whereby more or less non-condensed refrigerant is delivered to the cooling unit 8 through a non-restricted connection between it and thecompressor I, whereby the frost on the cooling unit may be completely melted and the system may start in normal operation as soon as the frostv is all melted.

In the second embodiment of my invention, illustrated in Fig. 2 of the drawing, a float controlled valve 4| contained in a casing 42, is connected into the refrigerating system in the same manner as shown in Fig. 1, andoperates asl an ordinary high side float in a manner well known v in the art. A conduit 43 connects the bottom of the float valve casing42 and a. discharge conduit 44 therefrom, and is provided with a valve 45 and a co-operating Valve seat 46 therefor contained in a casing 41. The valve casing 41 has a non-magnetic tube 48 connected at its upper end. The conduit 43 is arranged to by-pass the float controlled valve 4| when the rvalve 45 is opened, whereby refrigerant ows unrestrictedly from the compressor to the cooling unit. As explained with respect to Fig. 1, the valve 45 is maintained in an open position by a timing and switching device 49 longenough to allow the compressor to force non-condensed refrigerant to the cooling unit, thereby rapidly heating the cooling unit and melting the frost thereon.

In order to open the by-pass valve 45, a magnetic plunger 5| is attached to the by-pass valve 45 and is disposed-within the non-magnetic tube 48. A coil 52 is disposed outside the magnetic tube and is energized at and for predeterminedintervals by the timing and switch device 49 which is preferably the counterpart of that shown in Fig. 4. When the c oil 52 is energized, the plunger 5I is pulled upwardly, thus opening the 'by-pass valve 63.

valve 45 and allowing liquid and then non-condensed refrigerant to ow unrestrictedly from the compressor to the cooling unit, the non-condensed refrigerant condensing therein and rapidly heating the cooling unit to melt the frost therefrom.

In Fig. 3, I have illustrated another embodiment of my invention which is semi-automatic in operation.` In other words, the defrosting cycle of the refrigerator must be initiated manually, but the refrigerator is returned tonormal operation automatically. It will be obvious `that in this embodiment of -my invention, an electric device may be used for automatically initiating the de- 'frosting cycle if desired. It will also be obvious that the'control system shown may be applied `directly to a oat valve as shown or it may be applied to a by-passing arrangement as shown in Fig. 2.

In this embodiment of my invention, a motor 56 energized through leads 51 drives a compressor 58, yboth the motor and compressor being pref`` erably contained in a hermetically sealed casing 5|), and pumps vaporous refrigerant to a condenser evaporates and absorbs heat from a food cham-y ber 65 before it is drawn back to the compressor 58. The motor 56 isoperated in response to evaporator temperature and is controlled by a thermostatic device 66 and a switch 61 in the motor electrical line 51 in a manner well known in the art, the compressor 58 therefore operating intermittently.

In order to accomplish defrosting, it is desired again to allow hot liquid and non-condensed refrigerant to flow unrestrictedly from the compressor 58 to the cooling unit 64. 'I'his is accomplished by providing the oat casing 6| with a sylphon bellows 68 therein, and so disposing the bellows that expansion thereof will open the valve 63 and allow refrigerant liquid and vapor to pass unrestrictedly therethrough..

In order to effect opening and closing valve, the bellows 68 is connected through a conduit 69 to a gas filled bulb 1|v disposed outside .the oat casing. 6I and which is surrounded by a heater coil 12. When heat is applied to the bulb 1| by the coil 12, the gas in the bulb expands, thus expanding the bellows 68 and opening the It is necessary to provide means for energizing the heating coil 12 and for maintaining the valve 63 open for a sufficient time to ensure that non-condensed refrigerant will be delivered directly from the compressor 58 to the cooling unit 64 and condense therein. This means comprises a push button 13 which vis maintained normally in the position shown by a spring 14, a. set of contacts 15 which are closed by pushing the button 13 inwardly to energize the electric heater 12 and a thermostatic latch comprising a hook 16 on the end of the push button 13 and a bimetal strip 11 which is placed adjacent to the heater coil.

When the push button 13 is operated, the heater 12A is energized by the closing of the contacts 15, the bimetal strip 11 holding the hook 16 and maintaining the contacts 15 closed.y The strip 11 bends l after a predetermined time due to the heat .emanating from the coil 12, and releases the hook 16, whereupon the spring 14 opens the contacts 15. As the gas in the bulb contracts thereafter,

of the the bellows 68 also contracts and returnsthe oat controlled valve 63 to its normal operation in the refrigerating cycle.

From the foregoing, it will be apparent that I have illustrated several embodiments of my invention for rapidly defrosting the cooling unit of a mechanical refrigerator at times predetermined either manually or automatically, which systems are based on the broad idea of temporarily using the cooling or vaporizing unit as a condenser, whereby the sensible heat of the refrigerant is transferred rapidly to the evaporator. By this means, frost is melted quickly off the cooling unit without melting ice or frozen desserts, and without allowing the refrigerator box temperature to rise to a point where spoilage is likely to occur. I have also provided a variable or adjustable defrosting device to meet various conditions, the adjustments being determined by the user of the device.

While I have shown my invention in several forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications, without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What I claim' is:

l. In a refrigerating system, the combination of a heat absorbing element normally subject to accumulation of frost thereon, a compressor for circulating refrigerant vapor, a condenser for normally supplying the refrigerant after condensation to the heat absorbing element to vaporize therein and cool the same, means for periodically supplying non-condensed refrigerant to the heat absorbing element and means for maintaining the compressor in operation for the time that non-condensed refrigerant is supplied to the heat absorbing element, whereby th-e heat of the vapor is absorbed by said heat absorbing elementto rapidly defrost' the same.

2. In a refrigerating system, the combination of an evaporator normally subject to the accumulation of frost thereon, a compressor for circulating refrigerant vapor, a motor for driving the compressor, a sealed casing for surrounding both the motor and compressor and containing refrigerant in heat conducting relation therewith, a condenser for normally liquefying the compressed refrigerant vapor, means for normally supplying the refrigerant vapor after condensation to the evaporator to vaporize therein and cool the same, and means for periodically supplying non-condensed refrigerant vapor containing sensible heat of the motor, compressor and compression to the evaporator, whereby the noncondensed vapor is condensed therein and -the heat of condensation and the sensible heat of the vapor is absorbed by the evaporator to rapidly defrost the same.

3. In a refrigerating system, the combination of an evaporator normally subject to the accumulation of frost thereon, a compressor for circulating refrigerant vapor, a motor for driving the compressor, a sealed casing for surrounding both the motor and compressor and Containing refrigerent in head conducting relation with the motor and compressor, a condenser for `normally liquefying the compressed refrigerant vapor, means for normally supplying the condensed refrigerant to the evaporator to vaporize therein and cool the same, and means for periodically supplying non-condensed refrigerant vapor, containing sensible heat absorbed from the motor and compressor and the heat of compression to the evaporatorhwhereby the non-condensed vapor is condensed therein and the heat of condensation and the sensible heat of the vapor are absorbed by the evaporator to rapidly defrost the same, and means for maintaining the compressor in operation while non-condensed refrigerant is being supplied to the evaporator.

4. In a refrigerating system, the combination of an evaporator normally subject tothe accumulation of frost thereon, a compressor forfcirculating refrigerant vapor, a condenser for normally liquefying the compressed refrigerant vapor, means including a valved conduit for normally supplying condensed refrigerant to the evaporator to vaporlze therein and cool the same, means providing a by-pass around the valved conduit, means for periodically directing noncondensed refrigerant vapor from the compressor to the evaporator through said by-pass, whereby the heat of the vapor is absorbed by said heat absorbing element to rapidly defrost the same and means for maintaining the compressor in operation while the last-mentioned means is inactive.

5. In a refrigerating system, the combination of a heat absorbing element normally subject to the accumulation of frost thereon, a compressor for supplying compressed refrigerant vapor, a condenser for liquefylng the compressed refrigerant vapor, means including a normally restricted ,connection for supplying the refrigerant after condensation to the heat vabsorbing element for vaporization therein to cool the same, and means for periodically supplying noncondensed refrigerant vapor from the compressor to the heat absorbing element to heat the same, said last means comprising a heater energized by manual means, a thermostatic latch adapted to be operated by heat, a thermostatic bulb adjacent to thev heater and said valve, said thermostatic bulb when heated by said heater adapted to provide a nonrestricted connection between the compressor and heat absorbing element, said thermostatic latch when heated adapted to return said connection t`o its normally restricted state a predetermined time after the action of the thermostatic bulb has opened the valve.

6. The method of rapidly defrosting the evaporator of a mechanical refrigerator in which a relatively high temperature refrigerant vapor is.

circulated in heat exchanging-relation with and by a hermetically sealed motor-compressor unit to a condenser for normally liquefying the refrigerant vapor in the condenser and wherein the condensed vapor is, in turn, normally supplied in a restricted manner to an evaporator to vaporize therein and cool the same, which consists in discharging first condensed refrigerant liquid and then uncondensed refrigerant vapor which both contain motor and compressor heat into the evaporator in an unrestricted manner while the compressor is running and at the same time removing refrigerant vapor from the evaporator, whereby the evaporator first absorbs sensible heat from the condensed refrigerant which partially balances the heat dissipated by the continuous vaporization of the refrigerant, secondly absorbs both the heat of condensation and the sensible heat of ythe non-condensed refrigerant vapor which is supplied'to the evaporator and is condensed therein, which heat of condensation alone balances the heat dissipated by the continuous vaporization of refrigerant and thirdly absoi-bs heat of condensation and sensible heat of some of the non-condensed vapor supplied to the evaporator, and only the sensible heat of other of the non-condensed vapor supplied to the evaporator, which heat of condensation and some of the sensible heat absorbed balances the heat dissipated by continuous vaporization in the evaporator, whereby the evaporator is rapidly defrosted.

7. In a refrigerating system, the combination of a unit for normally absorbing heat, means for periodically adding a predetermined minimum amount of heat to the unit, means for thereafter suddenly adding more heat to the unit at a substantially faster rate than the rate at which the minimum amount of heat is added, means for varying the total amount of heat added at the faster rate and means for rendering the heat adding means ineffective after predetermined amounts of heat have been added to the unit.

8. The method of rapidly defrosting an evaporator of a refrigerating system in which, normally, a compressor discharges compressed refrigerant vapor at a relatively high pressure to a condenser for liquefaction therein and wherein condensed refrigerant vapor is supplied through a restriction to the evaporator maintained at a relatively low pressure by 'the compressor for effecting vaporization of the liquid refrigerant therein, which consists in, rst, circulating condensed refrigerant fluid to the frosted evaporator without restriction, secondly, circulating refrigerant vapor to the frosted evaporator without restriction, and maintaining the circulation of refrigerant vapor during the defrosting period by operation of the compressor.

MATSON C. TERRY.

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