US2666299A - Refrigerator defrosting control - Google Patents

Description

Jan. 19, 1954 M. s. SUTTON 2,666,299

REFRIGERATOR DEFROSTING CONTROL 6 Filed April 8, 1950 L2 K l 5a INVENTOR. MYER SUTTON WMCM'KL ATTORNEYS Patented Jan. 19, 1954 J Y :11? 1 Lv f:

EEEQIGEEMAQRDEFROSTINQGQMEQE' v M Sutton Bfinneapolis; Min-m, assignor to 1110- It"; S. Thermo Control. 00., Minneapolis, MinngatcorporaitimofiVI-innesotm 1? To fr s h d f us r ite li tomaxr to e m dim i i rans er h uree. ne v e u' rw "n i awe-me m et-the aoeumo lated frost laye the'prior art re} t3 1w e r tin i wmarr o; 2 9 any" oneoifseyer Stash, a'h'ot gas from th cIo'secf' refrigerating system, irk'stanees electrieai 5e" w h v through aresietahee'heatr'tha"is: eonta *with or atijj' ent the''ol'cf; dififu fil ieatiofie, howe'v 7 th' throngh'a cement 061115110 tfie 'flowof the" media" v tibr'i bf the" How 'ezshtrer devic by a" system whici'r genera y device "which is 'cafiafiie a eontroi'devioefora'preetermi after "which the How oritrolj' device is n'ra operative to terminate theiefroting opei tijqn.

'1 The handicap of thisjririof art arrahgernent has been that the laye'r 6f frost aeoum'ulated on the e'oid' diffuser viziild r ar y fdpth tiepending on th moistuie content Ethe oo-mifig into dontat the eold drfiuser whi r gmresul't from rariat iom the m oisttxrecontent q maria-1 s maintaindw hin'a storage space wh ihathe cold diffu I is situated. the timing 'meohanisms: useithe: prior} art were not efiectiveto adjust defto'sting yer-fed in acnortfance with the variation 01 the thickness of the frost layer.

timing, heretofore mvrdmwe of adiustableiicharaeter; leach adiutment deej intrequently thepperator would notheable-to gage the eer tii'oriorart ii aude t is mz' timer was either inadequee to ,prqriqe tor While it is trueflthatmost I This latter condition: is t the mlq fete iemere i of mrt; 01" eirseth f ir in iod; wesirermiiirdi to xtmdif-QI p i d of: wh ch; wa great r than ,was. 8-9: tuallyneoessarytq completely; remove; the; frost. n w i h mu txtr mely-harem, be fi i r y' when: he 9m difiuser is used in conjunction-with, a st age space in which perighabl'e products-snob a gse= cause if the celeb qifiu er i rie teqa -fter the mitt hae been removed and evenfor; a moderate l e gth ofitime; it will heat thestorage spape-to the ex= tent of thawihg-- or-e verr partial-h thawing the perishable prodirets -wh ighwil depreciate the natnral fiavor and the keeping-qualities of. such products even though; the temperature may still be;- in the; range-immediately below the freezin temperature: of water: ge ene tests have established that severely frozen; foods whieh are normaltrsmaintained at temperatures o f;0 or l'owerare damagect in their taste, keeping qnali ties: and: possibly -i n---.their vitamin eontent if during "storage the temperature of *;thap1;od uets Rut-permitted: to rise tos -asmueh as zfi fip the important feature in regulating the defrosti-ng of: cold diffusersaby. the-nee or a treating medium is; tcrterminate the flow heating metfi um to'ethedifiusezsimmediately after frosthas heenremovect so that the diffuserwill not raqiate heairto misethe temperature of the'surroundfing space;r i v invention disclosed inathis application is a modifieatiom ofi the disclosure shown in the co- Dfit g} .apnlication-otFreder-iek M;Jones,-Ser; No. 158,053, nows-xUnitem' states Patent No. $509,939,- gmmed Mayrfifi, 19.551, .whichds assigneqto the present assignea. i

the resent. disclosure amore or 1%s- -eon'- ventional timing device through the medium oi a monlertarilr.elosee:switch,,1mttates theop a- 21. f 2 32W fiOiltrolgdevicei also sets up a ho ng: oircuit, maintains the-flow onerativet-conditionltoflbring A- normally.=closed switch v v ing the defrosting operation substantially-immee diately after the removal of the accumulated frost and without regard to the length of time required for the defrosting operation to occur.

Another object is to provide a simple electrical control system for supervising the operation of a defrosting control device, which regulates the flow of an energy transferring medium to a cold diffuser, in which the control device is made operative by the momentary closure of a normally open switch, and is terminated by the opening of a normally closed switch whose action is responsive to the temperature of the diffuser.

A further object is to provide a control system for a defrosting control device which includes a control circuit that is energized by a first switch in the circuit which establishes a holding circuit that is broken by the opening of a normally closed switch in the circuit which is responsive to a rise of temperature adjacent the cold diffuser when the frost accumulation has been removed from the latter by the application of heat.

Other and further objects may become ap parent from the following description and claims, and in the appended drawings in which:

Fig. 1 is a schematic showing of one form of refrigeration system with which the present invention is adapted for use in controlling the defrosting of a cold diffuser; and,

Fig. 2 is a schematic diagram of a control system forming the present invention.

Referring now to the drawings and particularly to Fig. 1, is shown one form of refrigeration system to which the present, invention applies. Reference numeral I indicates a conventional compressor which is driven by a prime mover I2. The prime mover i2 may be either an electric motor or an internal combustion engine, and its operation is independent of other portions of the system. While not shown, the prime mover 12 will generally be operated by control means which respond to a condition within an enclosed space whose temperature is to be con trolled and, therefore, the prime mover will operate intermittently to maintain a substantially constant condition.

Extending from the high pressure side or compressor I0 is a conduit [4 which is joined to the upper end of a condenser !6. At its lower end condenser I6 is joined by a conduit l8 which extends to one side of a refrigerant receiver 20. Extending from the other side of receiver 26 is a conduit 22 which is joined to the lower end of an evaporator 24. Mounted in conduit 22 is a conventional expansion valve 25 whose operation is controlled by a thermostatic bulb 28. Extending from the upper end of evaporator 24 is a conduit 38 which at its other end is joined to a manifold 32 on the low pressure side of compressor I0.

Extending from a. T 34 in conduit i4 is a conduit 36 which at its other end is joined to a T 88 connected in the evaporator 24. Mounted in conduit 36 is a flow control device or valve 48 whose operation is controlled by a motorizing mechanism 42, hereinafter disclosed as a solenoid operator.

A control box indicated at 44 contains the necessary mechanism for operating the motorizmg portion 42 of valve 40 through a pair of conductors 46. 48. A thermostatic bulb 58, having a connected tube which extends to the control box 44, is supported on fins 52 which are secured to the outer surface of the evaporator 24 so that in effect bulb 50 is in thermal contact wit ap orator 24. Q

Referring now to Fig. 2 is schematically shown the control circuit, the major portion of which is normally contained within the control box 44. shown in Fig. 1, together with valve 48 and its motorizing portion 42. A timing device indicated at 54 has connected thereto a rotating switch member 56 which is adapted on rotation to engage a stationary contact member 58. The parts just described may take any one of a number of forms wherein after the passage of a predetermined period of time the movable switch 56 is suitably brought into engagement with the fixed contact 58. and it should be understood that the movable switch 56 may be adjustably positioned with respect to the timing mechanism 54 so as to engage the fixed contact 58 at regular predetermined intervals and there may, if necessary, be one or more of the movable members 56 which will engage thefixed contact 58 at predetermined intervals even though these intervals be less than twelve or twenty-four hours in which the normal clock mechanism will make a complete rotation. As here shown, the timing device is actuated by a motor 68.

Reference characters L1 and L2 are lineconductors extending from a conventional source of power, not shown. A conductor 62 extends from conductor L2 to the moving switch contact 56. A conductor 64 extends from conductor L2 to one side of motor 60 and conductor 66 extends from the other side of motor 60 to conductor L1 to provide for the operation of the electric motor 60.

A conductor 68 extends from the fixed contact 58 through a junction 10 to a contact 12. A conductor 14 extends from a contact 16 to the line conductor L2. A conductor 18 extends from junction 10 to a movable switch blade which supports a contact 82 that is adapted to normally engage a fixed contact v84. A conductor 85 extends from stationary contact 84 through an induction coil 88 of a relay indicated at 90. From the other end of the induction coil 88 a conductor 92 extends to the line conductor L1. Relay es carries an armature controlled switch 94 which when the induction coil 88 is energized engages the contacts 12, 16. Extending from a junction 96 on conductor 86 is a conductor 45 which connects to an induction coil I00 heretofore designated as the motorizing portion 42 of the valve 40, shown in Fig. 1. A conductor 48 extends from the other side of the induction coil let to the line conductor L1.

The movable switch 80 is connected to a bracket I04. On one side of the switch 80 is a coil spring I06 which is adapted to resiliently hold contact 82 in engagement with contact 84. A bellows I08 is mounted on the other side of switch 80 and is connected through tube 5! to the thermostatic bulb 50, being the same which is shown in Fig. 1. While switch 86 is here shown as being actuated by an independent fluid thermostat, the switch may be composed of a bimetallic element contained within a cartridgelike casing.

The operation of the refrigeration system shown in Fig. 1 is conventional but for a further understanding, the evaporator 24, which may be regarded as a cold difiuser, would normally be situated within an enclosed space whose temperature is to be controlled. The prime mover 12 will, through control means not shown, be responsive to the condition within the enclosed space in which the cold diffuser is mounted and such control means will periodically call for the capacity. which liquid is ti ereducedpress retina sen. .Th ,,.vap zed frefrrg rat an, 1 through the 'c'dn'duit 30 t6 the header 32 the low pressure sideof the compressor. on entering the compressor the vapors are compressed ei eWainw htc een;Meaga denser T6 from whence the condenser vapors will return to the receiver 20'.

Tdeffect defrosting of the.evaporatorxbrucold diffuser 24, valveAiLisiopehed its motorizing mechanism 42 .to permithotga'sesfrom the pres ure side .of the refrigerant systemhto fiow nor-n.1, 34 through .therconduit v36 arid-T038 into evaporator, In practice, the prime mover .l 2 iivill. be operating duringthe defrostingwperation because thewevaporator WiILvery likely-be coated with a suflicient layer of frost so as to insulate the diffuser from the enclosed space to such an extent that the refrigerating needs of the enclosed space will require operation of the prime mover.

Referring now to Fig. 2, the moving contact 56 will be adjustably mounted with respect tothe timing device 54 so as to bring about a defrosting operation after a predetermined period of time from the last defrosting operation. Assuming now that the movable switch 56 has engaged contact 58, a circuit will be established which may be traced as follows. From the conductor L2 through conductor 62, switch 56, contact 58, conductor 68 to junction 10, thence through conductor 18 to switch 80, and thence through the closed contacts 82, 84 and the conductor 86 to the junction 96, thence through the induction coil 88 and conductor 92 to the line conductor L1. Current will also flow from junction 96 through the conductor 46 and induction coil I into conductor 48 to the line conductor L1. This will complete a circuit to cause simultaneous closing of the relay 90 and opening of the motorizing portion 42 of the valve 40. When relay 99 is energized, the armature connected switch 94 engages the contacts 76, 12 to establish a holding circuit which may be traced as follows. From the line conductor L2 through conductor ?4 to contact 16, thence through switch 94 to the contact 12, and thence through conductor 68 to junction 10. From junction 19 current will flow through the conductor 18, switch 80, contacts 82, 84, conductor 86 to and through the induction coils 88 and I90 and thence to the line conductor L1 through conductors 92 and 48. The last named circuit is a holding circuit because the movable switch 56 will only make a momentary brushing engagement with the stationary contact 58 and as the timing device 54 continues its operation the circuit will be broken through the switch 56, 58 so that the holding circuit through relay 90 maintains the motorizing device 42 of valve 40 in operative condition. While the diffuser 24 is coated with frost, the thermostatic illin. will refle tarqld con iti niana th lf ill deflate .hprersrrwh -t e f s I di userfla brmeitme.t amt t iv res q d ari in temii atufe Qftl fi tfiiscir w ich i "toc a ion y ne as tha is n er n the f e h e T1 8 I i 's"i ..te ii er mr of the di u r j "systeiji within the thermostat to; .Tefi en r nsiemc therbefiows its a aint rri lttic. reth -pswitenh ade MupWardly {to break engagement between the normall closed ,I'IIHQSQ, :ccn acts. ar th que the ind ct n ck aandthisi eq .;b .e..tc.- ha 1min circuit establi hed s can n-.55... thr u h .hpldine i; when, inciu e g ie relay 9.0. 1TYII1S,at er. sti wciimno manr o cur by re on dfeugagemmfi.Qfmntacts. .56., 5.8,.ther'e. is mile" r rimmed; r mancin thev th rm static d vi e. W li igidit esrcndto ar segiritmperatir medimi r in br ak the def ting cirti ti a heavy coating p rost has been e tab ished. on tIie-d tuser.ihe ermostatic I str c win i t r'e's'nq ic t scheme of conditions a d: all Of the frost has. been removed mm the rfa egf'tiieplifiusr, .4 t 1? t ss lqft f rese l ti fi reside Y 1. Siii circuit for-continuing the .qbfi jfid lfifia new; cen 1....c vi e wherema field? op switch is momenta iiy closed and wherein the holding circuit which operates the control device is broken by a normally closed thermostatic switch which is also in the circuit. By this simple arrangement variations in the thickness of the layer of frost on the diffuser will have no effect and need not be compensated for by adjustment of the timing means. The circuit will always be broken as soon as a slight rise in temperature occurs at the diffuser, which will follow removal of the frosted layer. Under these circumstances the diffuser will not radiate damaging heat into the enclosed space since the normal refrigerant fluid circuit will again be established as soon as the flow control device is closed and the diffuser will again be rapidly cooled by evaporation of refrigerant fluid.

My invention is defined in the terms of the appended claims.

I claim:

1. A system for controlling the operation of a defrosting control device, comprising a first circuit including a motor operatively connected to the control device and which when energized activates the control device to initiate defrosting of a cold diffuser, a source of power, a normally closed switch in the circuit between the source of power and the motor, a normally open switch in the circuit between the source of power and said first named switch, said second named switch which when closed being effective to energize said motor, a relay solenoid in said circuit which is energized simultaneously with the motor and concurrently closes a pair of relay contacts, and a second circuit including the source of power, said relay contacts, said first named switch, the relay solenoid and said motor, said second circuit being effective to maintain'energization of the motor independent of the second named switch, said first named switch on opening being effective to de-energize either of said circuits.

2. A system for controlling the operation of a defrosting control device, comprising a first circuit including a motor operatively connected to the control device and which when energized activates the control device to initiate defrosting of a cold diffuser, a source of power, a normally closed switch in the circuit'between the source of power and the motor, a normally open switch in the circuit between the source of power and the first named switch, said second named switch which when closed being effective to energize said motor, a relay solenoid in said circuit which is energized simultaneously with the motor and concurrently closes a pair of relay contacts, a second circuit including the source of power, contacts of said relay, said first named switch, said relay solenoid and said motor, said second circuit being effective to maintain energization of the motor independent of the second named switch, and temperature responsive means operatively connected to said first named switch being efiective to open said switch and tie-energize either of said. circuits to terminate operation of the control device.

3. A system for controlling the operation of a defrosting control device, comprising a first circuit including a motor operatively connected to the control device and which when energized activates the control device to initiate defrosting of a cold difiuser, a source of power, a normally closed switch in the circuit between the source of power and the motor, a normally open switch in the circuit between the source of power and said first named switch, said second named switch which when closed being effective to energize said 8 motor, timing means operativel'y associated with said second named switch being efiective to moinentarily close the second named switch and thereafter move the same to an open position, a relay solenoid in said circuit which is energized simultaneously with the motor and concurrently closes a pair of relay contacts, a second circuit including the source of power, said relay contacts, said first named switch, the relay solenoid and said motor, said second circuit being effective to maintain energization of the motor after the timing means has again opened the second named switch, and temperature responsive means operatively connected to said first named switch being effective to open said switch to ole-energize either of said circuits in response to a change of temperature.

MYER S. SUTTON.

References Cited in the file or this patent UNITED STATES PATENTS,

Number Name Date 1,913,433 Doble, Jr. June 13, 1933 2,081,479 Fink May 25, 1937 2,313,390 Newton Mar. 9, 1943 2,333,432 Lum Nov. 2, 1943 2,451,682 Lund- Oct. 19, 1948 2,525,560 Pabst Oct. 10, 1950 2,551,163 Rickert et a1 May 1, 1951

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