US2319349A - Refrigeration apparatus - Google Patents

Description

y 1943 T. s. SAFFORD REFRIGERATION APPARATUS FiledOct. 9, 1936 3 Sheets-Sheet l control that the or with her ice for purpose Patented May 18, 1943 UNITED STATES PATENT OFFICE -REFRIG'ERATION APPARATUS Truman S. Safiord, Riverside, Conn. Application October 9, 1936, Serial No..104,840

'1 9. Claims.

This invention relates to a device fol-automatic defrosting of refrigerators, andmore particularly to such a device which is adapted to'control the refrigeration, e. g., by cutting off the supply of refrigerant, so 'that'frost which may have accumulated upon the refrigeratin surfaces maybe allowed to melt away, but which will-exercise such control only at'times when rapid refrigeration is ordinarily not required.

Since the introduction many years ago of artificial refrigeration, the accumulation of frost 'upon therefrigerating surfaces has presented one of the most annoying andever present problems. Numerous methods of defrosting by heating or dissolving the frosthave been suggested and to some extent have been used, but such methods have been manually contro-lled'and have been dependenttherefore upon the care and watchfulness of the operator. In domestic refrigerators the cooling unit is often hidden behind an enameled iron screen, and'the operator, often a domesticservant understanding little or nothing of the operation of the refrigerator, may allow the frost to collect for weeks or even'months before the defrosting is carried out.

It has alsobeen proposed to make defrosting automatic by widening the gap between the on and off temperatures'of-the thermostatic control. Thus the temperature at which the refrigeration is begun in' each cycleor in one of a series of cycles-may be sufficiently hig to ensure that the frost will bemelted before a new cycle or a new series thereof is-initiated. While this'sug- 'gestion mayovercome the objection to manual control will be operated too infrequently, it introduces a more serious objection from thepoint of view of the manufacturer'and user ofdomestiorefrigerators' that it'may at any time leave a hostess in the lurch with no ice cubes cream and frozen desserts melted. It is an object of the present invention to prowide-an automatic defrosting control, which will require no'attention, and will'ensure the tho-rougli and'frequent elimination of frost, with little "or no likelihood of failing to provide adequate refrigeration -at-times when it is needed purpose.

In the accompanying drawings for any I have shown, of illustration, a number of embodiments myinventionby which this object and other objects maybe accomplished.

Fig. l is a front elevation of a domestic refrigerator with the door removed to disclose the positionin or parts used. in-my invention;

.g. 'Z'is a detailed cross sectional viev taken on line scale;

Fig. 3 is a longitudinal vertical sectional view of a switch used in one embodiment ofinyinvention;

Fig. i is a vertical cross sectional view line 4-4 of Fig. 3;

Fig. 5 is a'view in side elevation of a detail which may replace a portion of the device illustrated in Fig. 2;

Fig. 6 is a sectional view be used in place of thatthat of .Fig. 2';

Figs. 7 to 9 inclusive'are circuit diagrams illustrating various embodiments of my invention;

Fig. 10 is a fragmentary view of a refrigerator box showing another modified form of my invention in position;

Fig. 11 is a fragmentary view in horizontal sec- 2-2 of Fig. 1 and shown onan enlarged taken on of a device which may illustrated in Fig.5 or

tion of the same embodiment as shown in Fig. 10;

Figs. 12 and 13 are detail views showing a part of the device of Figs. 10 and 11 in different positions of operation;

Fig. 14 is a detail View partly in section-showing the device for holding theswitch mechanism;

Fig. 15 is a fragmentary view similar to the right hand portion of Fig. 11 but showing the device after the predetermined delay and with the parts in position to permit defrosting;

Fig. 16 is a fragmentary view partly in vertical section of another embodiment of my invention;

Fig. 17 is a wiring diagram of the embodiment illustrated in Fig. 16;

Figure 18 is a diagrammatic illustration of another modification of. my invention;

Figure 19 is a detail of the controlling means as used in Figure 18; and

Figure 20 is a detail of a control switch.

In Fig. 1, I have shown adomestic refrigerator of common form having an insulating box 20, the door of which has been removed to disclose the interior, a cooling unit 21,- a central partition 22,

and shelves 23. A clock 24, advantageously an electric clock operated from the same alternating current power line as the refrigerator motor, may be associated with the refrigerator, and as will be morefully disclosed hereinafter, this clock may serve as one control in the defrosting device. It

is .not necessary,-however, that this clock, if used as a defrosting control should have a visible face,

erator in Fig. 1, and the purpose of this as well as its detailed construction will be set forth below.

I have said above that one purpose of this invention is to protect the hostess against failure of adequate refrigeration at critical times. My invention therefore contemplates the provision of devices which are responsive to, or may be correlated with, the uses to which the refrigerator is put.

Fig. 2 illustrates the control element of a device which is directly responsive to the use of the refrigerator. In this device, an operating rod 2'! is mounted in a hanger guide 28 secured to the box 23, and is preferably provided with a cushion buffer 29 on its outer end.

A link 33 is pivoted to the opposite end of the rod 21 and the opposite end of this link is pivotally connected to the crank 3|, which engages a switch 32 of the type having a fluent conductive material adapted to flow onto and away from spaced electrodes. This switch is pivotally supported in hangers 33; and, as shown, the leads to the electrodes 38 may serve as the supporting pivots, thus making contact with the members 33, which, therefore, may serve as binding posts to connect these in-leads into the circuit. Thus when the door is open the operating rod 21 is released and the fluent conductive switch is allowed to hang vertically from its pivot. When the door is closed it pushes the rod 21 and through the linkage 30-3! the switch is pushed upwardly to the position shown in Fig. 3. It is desirable to provide a spring on the rod 21 between the support 28 and the buffer 29 to assist in restoring the parts to the position shown in Fig. 2 whenever the door is opened.

The switch which I use for this purpose is advantageously one of special design as shown in Figs. 3 and 4. A body of fluent conductive material 35 is carried in a vessel 36, commonly a sealed glass tube, and the vessel is provided with a baffle 01' dam 31 between the end having the electrodes 38 and the opposite end. Near the bottom of this dam is a narrow orifice, so related to the volume of the fluent conductive material as to require a predetermined time for it to flow therethrough, and at the top of the dam is an open space sufliciently large to allow the entire body of fluent material to flow back over the dam substantially instantaneously when the vessel is tipped down. Preferably the dam is slanted as shown in the drawings to facilitate the return flow over the dam. The fluent material may be an electrolyte, especially in the case of alternating current and especially where it controls a o I relay circuit rather than the main motor circuit,

e. g., as shown in Figs. '7 and 9 of the drawings. The fluent material may also be a fine metallic sand or sprayed metal similar to shot but of very much finer grain.

The electrodes 38, in the preferred form of the invention are bent over so that they pass out through the walls of the vessel along the axis of tilting. The external parts of the electrode inlead wires may therefore serve as trunnions to carry the fluent conductor switch, and in order to provide electrical contact, these electrode wire trunnions are preferably mounted in hangers 33 connected into the circuit so that they serve also as binding posts for the electrodes 38. parts are insulated from the box 20 and should also be insulated from the rod 2! by an insulating link 30 or crank 3|.

In the use of the device just described, the opening of the door allows the rod 27 to move These outwardly and the fluent conductor switch to tilt downwardly to the position shown in Fig. 2. In this position, so much of the mass of fluent conductive material as has passed under the dam 3! falls down over it into the then lower end of the vessel 36. Upon the reclosing of the door the vessel 33 is again raised to the position shown in Fig. 3, whereupon the fluent conductive material is dammed behind the dam 31 and allowed to flow only very slowly through the orifice to the other end of the vessel, until it finally reaches the level of the electrodes 38 and closes the circuit between them. In this way a delay of any required duration may b interposed between the last opening of the refrigerator and the shutting dOWn for defrosting, and thus sufficient time may be allowed for freezing ice cubes, etc., or the time interval may be adjusted so that it will be greater than will occur at any time during a normal working day, and thus defrosting will occur normally during the small hours of the morning when it cannot interfere with the various uses of the refrigerator.

When the device just described is combined with a, clock or other chronometer device, e. g., as shown in Figs. 1 and '7, and the fluent conductive material is an electrolyte a third electrode 5| is advantageously provided. This electrode is arranged so that it just touches the stream of conductive material which flows under the dam 37 and along the trough d2, so that after the conductive material has made contact with the electrodes 38 and as the last of it flows along the trough 42, a contact will be established temporarily between the electrode 3% and the electrodes 33.

In Fig. '7, I have shown a wiring diagram of a circuit which may be used with the defrosting controls which have been thus far described. The clock 24 in this case is provided with a contact segment 45 and a rotating contact arm 45 which preferably makes one revolution each twenty four hours. Adjacent the beginning of the contact segment is a switch 41 normally held open but adapted to be temporarily closed by the action of the rotating arm 33 on the insulated portion of a bell crank lever which forms the switch 47. At or near the end of the segment 45 is another bell crank lever, also of insulating material, for operating a switch 48 normally held closed but opened temporarily by the arm it. By temporarily I do not of course intend to imply that there is any short time limit upon the operation of these switches, but their work is quickly done and if they are held longer it is merely a convenient way of operating.

A lead 49 connects the arm 3% with the main line conductor 56, and each of the switches 41 and 48 is connected to this lead 49 through a parallel circuit portion. The parallel circuit portion which includes switch 68 also includes thermostat switch 5| associated with the refrigerating unit and adapted to open when the temperature at the outer surface thereof rises above a temperature limit at which defrosting is complete. Switch 5! is adapted to close when the said surface is cooled to a temperature at which frost occurs thereon. The switches i? and 48 are also adapted to be connected to one of the electrodes 38, the former directly and the latter through the upper contact of the relay 53, and through the coil back to the main line conductor 5 1. The relay 53 controls the main refrigerator power circuit or the main refrigerator control circuit by means of the contacts 55.

agar-93,49

lThercontact-ssegment 45: is ;connected directly :to thethirdrelectrokieM Irof 'the;switch1 32.

.TInT. the. operationxofzuthis "device, the arm 46. is "rotated by the -tclock until it rstrikes .1 the aim Y of the :bell icra-nk rswitfch '4"! and thus closes the fi'circnitx'throughfsaid switch l1 :to the :electrodes 38tofithe- 'fluent:con'ductor switch 932. .If the re- :frigerator door is closed :and has been iclose'd ilong enough :to .iallo'w the 'fluent :con'ductor to .close the 'c-ircuit ebetween "the electrodes 38, the relayi5=3 is iener'gized at once and the 'main re- -frigerator5circuitis broken atz55. .Assuming that ftherecis frost'onv the refrigerating unit, its tem- ;'perature :will :be such ithat the thermostatic switch 551 'will be :rclose'd; and immediately upon the operation .of .thelrelay $53, the parallel 1eniergizing circuitiwillabe "closed through -the switch 48;.randithesswitchiilp 'lThusit'heirelay armature will the :heldup *even after the switch T41 is rdropp ed by? theriarm T46.

.Defrostin'gv is.. accor.fipiished by preventing further'ref'rigerationxby reason Oft'hecopening df the main circuit at: 55 penitence initiated, defrosting *will continue until one of 2 three things happens. iIn the firstzplace iri'gerator. If ithis :is done, it will :very .likely mean that thex'icea'trays:mayhave been 5 fresh I l'fil-led with -water or thatfl'a'eonsiderable quantity of .ivarrnzairi has ibeenra dmitted which :will call .forfrnorerapid refrigeration .to .restore tthe :de-

sireditemperature ionpreservationsof the .foods. Opening of the 'door will, as described above. break the relay circuit at 32,.and willtherefore allow fnorm-al 'operation of the refrigerator I once more. after the closixgroflthe fdoor therconductivematerial will agalI1 -.-contact with. the electrodes r38. At this time, however, thecircuit maybeopen at 47 Lby'reason iofthe arm v46 :having passed thefar-nr of the=.bell 'crank::switch 47, huttif the arm'f45 is still on the contact segmentfi the relay circuit willinevertheless "be closed through the segment fifi :and "the electrode 14 I :and 1 the: stream "of conductiveii-iquidfi flowing the: trough 42 if the massiof l conductivei'liquid :collected tin the end of .theituhetiifi i hasirisen tort-he level of the "electrodes-:38. "Once operated by'this temporary circuit, the relay :will the held thy" the closing of: thGTCllCLl'lt. thlfl1lgh2thBXSWltChBS43 and I 5!.

someone :may open the re- When i'the specified period has elapsed The second. event ovhich imay causetthe'relay 5,;

to drop itsarrnature aandmestore normal operation: 'ofthe refrigerator is nthe completion of '7 the defrosting. 'When the tempera tureoi the refrig- I eratin'g surfaces crises above the .freezing "point the 'thermo'static switchfii :opens and 'the2relay circuit isrbroken whereupon 'normalcoperation" is 'restore'd and 'continuesiuntil thetiappointec chour i is reached again.

'The third event is the end "of -the time allowed for defrosting. It may sometimes 'happen tliat -frozen *dessertsetc, -'or 'ice cubes "may melt f-a little at the'viery end-of the' defrosting period. since these may be needed early in the morning-or at theend of any other-period appeinted 'fordefrosting, it maybe desirabletorestorenormal operation even before the comple- --t-ion otdefrostingnnd beiorethe door-is opened. For this purpose the-switch 43 is provided. This switch-is opened by the passing of the arm-4,

aud t/henopened breaks the i'elay'circuit and oausest'he'dropping of the armature,

In Fig. 8 I have shown a' similar wiring diagram of a" circuit controlled by the-clock-alone. '"I-n "this case the defrosting begins at i the appoi-nted time and continues until-the end :of the 75 apparent ifrom "what has already cored Ito .ithe :shaft l t5.

.appointed time unlesssbefore then; theidefrosting is :completed. The toperation in this case .by means of the switches 41, 48 and '5twill be readily been said in connection with Fig. '7.

"Fig. '9;shows a similar circuit diagram of the case where the .circuit .control is entirely by means ofthe door-control, e. 'g.,;as illustrated in Figs. 2 to 5 inclusive, Inthis :case the openi-ngof the-"door :breaks the relay circuit at 32, :a nddtisronly after-the required delay that this circuit'canbere established. Duringzthe normal :day thefrefrigeratorwill beirequently opened, and the'delaynmay be chosen so that defrosting .willioccurtonlyat night, or the .delaymay be sufjficientso .as to. provide time to perform the refrigeration ordinarilyrequired after the refrigerator is opened, such as the rapid cooling of thQZbOX' and the'freezing of :water in ice trays.

' .lIn. ;Fi'gs. 5'an'd 6,-TI have shown .two alternative .=types of:'door controlwhich maybe used'instead "of thatfillustrated in Figs. 2; 3 and 4, e. g. in'the circuit shown'in Figurei 9. Theseare-shownpri- 'rniarilyito illustrate the widely varying mechanisms which may beused forthis purpose with- "out departing:fromthescope of my invention. 'ln thedevice toI":F-.ig. 5 the push rod-27 is connected to a gear rackTBD, which through a pinion and ratchet .notshown rotates the shaft 6| to wind :the1spring "b2 within the drum 63. Any *imown type'of'overwind protector may be provided'as for .examplea friction clutch adapted to slipiwhen the "spring is fully wound. The 'gearffidonthe;drum 63 'drives pinion 65 formiingzpart ioi a:suitab1e-clock"w0rk with escape- -ment cit-governor to determinethe required delay and at the end of such delay operates aswitch or other :defrosting control.

:therein :servesas the-delaying means and at the end :of the delay. allows 'operation of" the defrosting control. The spring .68 pushes the plunger-6'! *to'theleft when the door is opened and a spring 69 receives and stores up the force ofltherclosing of'the door. A flap valve 'H'pro- 'vi'desforirapidamovement of the plungerto the left 'delayedfmovement' in the: other 'direction. :flange 70 "may serve to operate the fdeirostingcontrol device.

When thisformfof :do'or control replaces that showntin Figs. 12, .3 sand 4, the closing .of the door pushes thelrod' 2'! so :Las to compress the 'The piston' 61 is then slowly driven 'downtheicylinder under infiuenceof the spring 'Sduntilthe point is reached'atwhich the flange "19: closes .orcoperatesthe: control switch "or other defrostingr'controlfdevice. As :soon as the door -istopened the-:pressurerxon"spring 69 is relieved ian'd the piston is promptly forced back under the-influence of the spring :68. Since the flap valve H is iopenedidnring'this return movement,

-the-piston returns'veryiquickly, and thedelay :begins aneW whenttheidooris: again-closed.

I In :Figs. .lOito 15 inclusive 1 have shown another'embodimenttof'myinvention. In this case 1 have tprovided1a switch "I 10 connected directly :into the motor circuit. This switch as best shown *infiFig. 114 is rotatably mounted on a rod H5 andat the other :endeneaees the collar l'l se- This springis under tension 'so that it .tends to hold the'switch H0 "member and its holder III in the position shown in Fig. 12, but permits it to be rotated to the position shown in Fig. 13.

From the bottom of one of the spring fingers I25 of the holder I I I a stud I24 projects laterally beyond the side of the switch III] and into the path of the member I23 connected to the hollow piston member I28 which will be more particularly described below.

A casing I20 in this embodiment of my invention illustrated in the drawings encloses the switch and air cylinder mechanism and only the rod I I5 and the plunger I22 project through this casing. A buffer block I35, preferably of soft rubber, is secured to the bottom of the casing, as shown in Figs. 12 and 13 to stop the rotation of the switch III and support it in the position shown in Fi 12. Y

The air cylinder delay mechanism comprises a fixed cylinder I33 secured within the casing I23. At the inner end of this cylinder I33 is a rent opening controlled by an adjustable valve plug I3I which is constructed to allow an inrush of air but to permit a very slow leakage of air outwardly from the cylinder.

Within the cylinder I33 is accurately fitted the hollow piston member I28 and against this presses the spiral spring I32. Within the hollow cylinder I28 is fitted the hollow push rod I21 with its open end inward and the spring I29 is fitted within both hollow members pressing against opposite ends thereof respectively. The cam I 23 is secured in the piston member I23 and has a portion extending into the open slot I33 of the push rod member I21 so as to limit its movement out from the hollow piston member I28.

The spring I32 is chosen just strong enough to push the piston I28 back to the beginning of its stroke when it is released from the pressure of the spring I29. The spring I29 is sufficiently strong to drive the piston I28 against the pressure of the spring I32 to the inner end of its stroke.

In the operation of this device when the door of the refrigerator box is being opened the push rod I21 isreleased and under pressure of the spring I29 immediately moves out from the holow piston I23 to the full extent permitted by the extension on the cam member I23 and its slot I33. At the same time the spring I32 pushes the piston I28 outwardly until the cam member I23 reaches the end of the slot in cylinder I33. This same movement draws air in through the valve I3I filling the space within the cylinder I33. The cam member thus is moved out from under the stud I24and the switch H0 is allowed to drop into the position shown in Fig. 12 in which the fluent conductive material falls over the contact member and closes the circuit of the motor. Thus normal operation of the motor will continue under control of the usual pressure and/or temperature control. When the door is closed it contacts the push rod I21 and drives it into the hollow piston I28 compressing the spring I23. The force of the spring I29 causes the piston I28 to move a short distance but this movement is limited by the air within the cylinder I33 which under compression resists the force of the spring I23. Very slowly this air is allowed to escapethrough the valve plug 931 until after the required delay the cam member I23 passes under the stud I24 lifting it along its .cam surface until it reaches the position shown in Figs. 13 and 14. In this position the switch is tilted so that the fluent conductive material falls away from the contacts and the motor circuit is broken beginning a defrosting period. This defrosting continues and the motor remains inoperative until one of two conditions occur. If the door is open the parts move again to the position shown in Fig. 11, and the switch is dropped to the position shown in Fig. 12. In this position, as already described, the motor becomes operative and refrigeration begins again. If, however, the door is not opened until defrosting is complete and the surface of the .cooling unit II4-rises above freezing temperature then the snap thermostat IIB snaps to a fiat position pulling the rod H5 toward the left, and pulling the stud I24 off of the cam member I23. When this occurs the switch III! drops again to the position shown in Fig. 12, notwithstanding the fact that the cam I23 is still in the position shown in Fig. 13. Thus refrigeration can begin again. When this occurs, of course, the thermostat H6 is cooled and snapped backto the position shown in the Figs. 10 and 11. In order that the cam member I23 may pass over the stud I24 when it is thus restored to the position shown in Figs. 11 and 15 the end I23 of the cam member is pivoted so that it may swing up but not down. Thus when the cam member'- I23 is retracted to the position shown in Fig. 11 it passes readily over the stud I24 but when moved again to the position shown in Fig. 15 it will engage the stud I24 and shift the switch as already described.

In this case, as in the cases already discussed above, the delay interposed by the air cylinder mechanism is advantageously such as to permit freezingof ice cubes or desserts placed in the trays of the refrigerating unit II4.

In Figs. 16 and 17, I have shown another embodiment of my invention similar in operation to that illustrated in Figs. 10-14. In this case-a cylinder I43 is supported in a bearing rail I4I on brackets I42 and I43. On the top of the cylinder is a gear rack I44 which meshes with a pinion I45 driving'an escapement or governor,

not shown, through a ratchet mechanism so that it can be quickly reversed but driven only at a constant slow speed in a forward direction.

Within the cylinder I43 is a spring I46 which bears against the end of the push rod I41 so that when the push rod is driven into the cylinder the spring I46 is compressed and energy stored therein. The outer end of the push rod I41 has a head I48 having one side positionedto engage the door when it is closed and its opposite side engages the spring I49 which, when the door is open moves the push rod -I41 and through'it the cylinder I40 to the left to the full extent of their permitted movement. I g

.In linewith the end of the cylinder- I;40 ;and at the end of its inward stroke is a switch mechanism I53. In the drawing this is.-shownenclosed in a casing, and of the working parts only the push rod I5! isshown extending from the casing. This push rod I5I is engaged by the end of the cylinder I40 as it approaches the end of its stroke and is pushed inwardly to open the switch and render the motor inoperative and thereby to initiate a defrosting period. As soon as the door is open, however, thecylinder I40 and the push rod I41 immediately move to the left to the full end of their permitted stroke. When the door is re-closed the push rod I41 is driven'to the right to the end of its stroke, while the cylinder I4!) is restrained by the escapement mechanism I65 and, therefore, the spring I46 is compressed and a delayperiod begun. As the escapement operates under the drive of the spring I46 the cylinder I40 moves slowly towards'the right until it again contacts the push rod II, opens the switch and initiates another defrosting period.

As shown in Fig. 17, which shows a modification of the embodiment shown in Figures to inclusive a thermostat I55 is provided responsive to the temperature of a surface to.be defrosted. This thermostat is shown as normally contacting with a spring contact I55 to close the circuit through the switch I59 to the motor. Thus when the switch is open the motor circuit is opened and a defrosting period begins. If, however, defrosting is completed before the door is reopened and the surface to which the thermostat is responsive rises above the temperature corresponding to complete defrosting, then the thermostat contacts with the second contact I56 and thereby closes a shunt across the switch I58 and begins the normal operation of the motor for renewed refrigeration. In this circuit the thermostat I 54 is shown as controlling the normal operation of the motor M, i. e., when the temperature is suificiently lowered by operation of the refrigerating mechanism the thermostat opens the circuit at the contact I55. It will be understood, however, that any of the usual controls may be included in the motor circuit and this thermostat IE4 serves only for initiating a renewed refrigerating cycle after completion of the defrosting.

In Figures l8, l9 and I have shown ann other embodiment of my invention. In this case the delay is determined by the operation of the refrigerating device. A rotary contact member 166 is driven through suitable reducing gears so that one rotation of the disc I88 represents a sufficient operation of the refrigerating device .to freeze ice cubes or a dessert in the trays of the cooling unit. In the present instance I have shown a worm wheel Edi driven from a worm iii-2 on the shaft of the motor I63 which operates the refrigerating device, not shown. The worm wheel I6I is in turn connected to a second worm I64 which drives the worm wheel 555 on the shaft- H35. At its opposite end the shaft I56 carries rotatably thereon the contact disc H vand between the worm wheel I85 and the disc hit is splined as shown at it? for reception of .a clutch 168 the hub of which engages the spline portion of the shaft and the face of which frictionally engages the disc I63. The clutch is pressed into engagement by the spring Ill] and is connected for disengagement by the push rod ill mounted in the brackets I12 and having. a

head I73 which engages some part on or connected to the door. Thus, whenever the door is open the clutch W8 is released by force of the spring I14 acting thrcughthe push rod Ill and the contact disc I60 is rotated to the beginning of its cycle by means of the spiral spring I15 which en ages its hub.

As shown inFigure 19, the disc Itii is made of conducting material with an insert I16 of insulating material. The brushes I71 and I78 connected into the motor circuit contact with the rim of this disc I66. Thus the motor continues to operate from the beginning of its cycle until the insulating insert comes under one of the brushes. When this occurs the motor circuit is broken and a defrosting cycle begins. In this ,case ,no means is shown for automatically ter operated by said minating the defrosting cycle and it will continue untilthe dooris next opened. It will be under? st d, oweve tha n, th s casea nth othe c e i ust ate nor a refrig r on ca .b a ai in i e crm tat a l lc a br hue ins th ou h. th w t h. l'ifi ract ras sh in Fi -i Bec u e o th d n .o ami e h n th insulating insert passes under one of the brushes, a is prefer bl in the dis athei t he the brushes I17 and I78 contact.withit should be mm rse in 1. or -a hc l o ct ains ar in -.Viher thi s o a t b a m r s it h a e use f x m e. as u t e e in e- "2 In th scas h me c y itch am unted-0 a ivo e h l I eh o lows th cont u o th d of e-c i I504 Throughout the predetermined cycle the switch is held in closed circuit position, but when the follower portion .of the holder reaches the indented portion of the disc Ififia the switch drops to an open circuit position and the defrosting period begins. 0f course, inthis instance the conductorsv terminate near the left hand, end ,of the switch shown in Figure,20 in extremities which. may be bridged by the mercury, the con.- ductors .being otherwise suitably insulated from the mercury within the mercury containing tube.

Although in theabove. I have described a preferred form of vmyinvention and several modifications thereof, it is to be understood that these are given only by way. of illustration of the numerousways in which the invention, may be embod I s d of sh t n cfi r frig ra i n e tirely fo pe i dt fr gerato -may erely. .be set dur n at pe iod t m tain a tempe ature slightly abovefreezing. Thus the closingof the refrigerator door mayset the control for rapid freezing, and at the end ,of a delaysuflicient to meet normal demands following upon ,the opening of the refrigerator,.the control may be shifted so. as togna-intain the, refrigerating surfaces at or slightly above the freezing point.

This application is a continuation in p rt of y prior o e ne l cat en. ..61 220 l J i 0, 19 Q What, I claim is:

e ro tin refr gera comprising an i sulating box having :a door, a refrigerating unit therein of the type adapted automatically to m nta he empe atm' -norm i t bo within predetermined limits, supplementary electricalmeans for controlling the supplyof refri r m t sa ef i eratineun t s as t permit me tin o fr ere r m. sa me comprising a relay, a chronometer device, a switch 7 chronometer device, ata predetermined timeto close momentarily the relay circuit, a .parallelcircuit portion around said chronometer operated switch including in series a contact closed by the armature of the relay,,a switch normally closed .but .opened by, said chro- ,.n m e i .a ,amr det ined. time -af-ter t e; c sms-and openine o the fi s a e ..cl r0- nometer ;,oper ated,switch, l and a thermostatic switch responsive to the temperature of. said. surfaceto. be defrosted and adapted .to. be;opened when the temperature of said'surface rises above the freezing vpoint, and means for delaying. the

operation of said relay until a substantial. time has elapsed after door.

the opening of the refrigerator 2. A defrosting refrigerator as defined in claim of the relay comprises a switch in the relay circuit, means for operating the switch having a substantial lost motion operation before it comes into effective-operating relation to said switch, means for regulating the speed of said lost motion operation, and means responsive to opening of the refrigerator door for resetting said switch operating means to the beginning of its lost motion.

3. A defrosting device for a refrigerator having an insulated box with a door and a refrigerating unit, which comprises means for controlling the operation of the refrigerating unit temporarily to permit melting of frost, means for operating said controlling means having a substantial lost motion operation before it comes into effective operating relation to said controlling means, means for regulating the speed of said lost motion operation, and means responsive to opening of the refrigerator door for resetting said operating means to the beginning of its lost motion.

4. A defrosting refrigerator as defined in claim 1 in which the means for delaying operation of the relay comprises a body of fluent material, a barrier having a narrow orifice, means for controlling a circuit responsive to flow of a substantial volume of said fluent material through said orifice and means for restoring said fluent material to the opposite side of said barrier when the door is opened.

5. A device for automatic defrosting of refrigerators which comprises means for temporarily interrupting refrigeration, means responsive to the opening of the refrigerator door to prevent interruption of refrigeration by the interrupting means during a substantial delay after the opening of said door, a chronometer device, and means associated with said chronometer device for limiting the operation of the interrupting means to a predetermined time when rapid refrigeration is normally not required.

6. A device as defined in claim 5 which includes means responsive to said second-mentioned means for operating said interrupting means at the end of the delay if the means associated with the chronometer device is set to permit such op eration, and means associated with the chronometer device for operating said interrupting means at'the predetermined time if the delaying means is set to permit such operation, each of said operating means being adapted to operate said interrupting means only momentarily, and means associated with said interrupting means for holding the interrupting means in operated position after said momentary operation has ceased.

'7. A device for automatic defrosting of refrigerators which comprises an electrical circuit adapted to control the refrigeration, a relay adapted to control said circuit so as temporarily to prevent further refrigeration, a chronometer device, a switch in the energizing circuit of said relay controlled'by said chronometer device so as to operate the relay at a predetermined time when rapid refrigeration is not required, a parallel portion of the relay circuit adapted to be closed by the relay armature so as to keep it energized once the relay has been operated, and a switch in said parallel circuit portion adapted to be opened at a given time when rapid refrigeration is likely to be required whereby to release said relay and restore normal control of refrigeration.

'8. A device as defined in claim '7 which further includes a thermostatically operated switch adapted to open said relay circuit when a temperature is reached at which defrosting is complete, and thereby to restore normal control ofrefrigeration.

9. A device for automatically defrosting refrigerators which comprises means for interrupting refrigeration, means for momentarily operating said interrupting means at atime when rapid refrigeration normally is not required, means for holding said interrupting means when thus operated, means responsive to completion of the desired defrosting for releasing said interrupting means so as topermit renewed refrigeration, and means for releasing the interrupting means at the end of an intended period ofdefrosting, whether or not the defrosting is complete.

10. A device for automatic defrosting of refrigerators which comprises an electrical circuit adapted to control the refrigeration, a relay adapted to open said control circuit temporarily to prevent further refrigeration, means in the energizing circuit of said relay adapted to close said relay circuit at times when rapid refrigeration is not required, and a thermostatic means responsive to the temperature of a refrigerating surface which is to be defrosted and adapted to open said circuit when the temperature of said surface rises above the freezing point,

11. The combination with an automatic refrigerator comprising a refrigerating device having a cold unit, a freezing container associated therewith, and an insulated box enclosing and cooled by the cold unit of means for temporarily interrupting operation of the refrigerating device during a period adapted to permit melting of frost accumulated on the cold unit, and means responsive to an operation necessary to the placing of liquid in said container in such position as to be frozen by the cold-unit, which means is adapted to delay the effect of said interrupting means during a normal freezing period following said operation. 7 r r 12. A device for automatic defrosting of refrig erators which comprises means for temporarily interrupting refrigeration, means for operating the interrupting means and adapted to be set in operation by manipulation of the refrigerator otherwise required for a use thereof in which continued refrigeration is desired, and means adapted for delaying the operation of said operating means whereby a substantial period intervenes between said manipulation and the final effective interruption of the refrigeration.

13. A device for defrosting refrigerators which comprises means for storing energy, said means being associated with the refrigerator so that its energy charge is renewed by a manipulation which is involved in a normal use of the refrigerator, means operated by said stored energy for temporarily interrupting normal refrigeration, and means for so controlling the release of the stored energy that said interrupting means will not be operated to the point of interrupting refrigeration until after a predetermined delay following said renewal of the energy charge.

14. The combination with an automatic refrigerator comprising a refrigerating device, a freezing container associated therewith, a thermostatic control for the refrigeration device, and an insulating box having a door thereon, of means for automatically initiating a defrosting period, means responsive to movement of the door and adapted to prevent initiating of the defrosting period by said first-named means during a period sufficient normally to freeze ice in said container.

15. The combination with an automatic refrigerator comprising a refrigerating device, a freezing container associated therewith, and an insulated box containing the cold unit of the refrigerating device and the freezing container, of means for temporarily interrupting operation of the refrigeration device during a period adapted to permit melting of frost accumulated on the refrigerating device and means responsive to use of the refrigerator involving the placing in said container of liquid to be frozen, adapted to delay the eifect of said interrupting means during a period following said use while such liquid is freezing.

16. An automatic defrosting mechanism for mechanical refrigerators including means operable at a predetermined interval after the closing of the refrigerator door to cut out the refrigerating unit, and means to cut in the refrigerating unit when defrosting is completed.

17. A control device for a refrigerator including means operative to modify normal operation of the refrigerator to permit melting of frost thereon, and appreciably later than when said means is placed in its initial operative condition, and means for intermittently placing said first means in its initial operative condition, whereby modified operation of the refrigerator is efiected only when a period between operation of said second means exceeds the time delay period of said first means.

18. In a refrigerator having a door, a control device including means operative to modify normal operation of the refrigerator to permit melting of frost thereon, and appreciably later than when said means is placed in its initial operative condition, and means for intermittently placing said first means in its initial operative condition each time said door is opened, whereby modified operation of the refrigerator is effected only when a period between door opening operations exceeds the time delay period of said first means.

19. The combination with an insulating box having an access opening, a closure therefor and refrigerating apparatus including an evaporator within the box, of means for suspending the operation of said apparatus to allow defrosting of said evaporator, and mechanism for delaying the operation of said suspending means for periods of time sufiicient to permit a normally required amount of refrigeration to be effected by said apparatus, said mechanism including means for starting a period of delay, said last-named means being actuated in response to a use of the box including at least one operation of the closure.

TRUE/IAN S. SAFFORD.

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