AU601413B2 - Ice bin level sensor - Google Patents

Ice bin level sensor Download PDF

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Publication number
AU601413B2
AU601413B2 AU70918/87A AU7091887A AU601413B2 AU 601413 B2 AU601413 B2 AU 601413B2 AU 70918/87 A AU70918/87 A AU 70918/87A AU 7091887 A AU7091887 A AU 7091887A AU 601413 B2 AU601413 B2 AU 601413B2
Authority
AU
Australia
Prior art keywords
ice
signal
electrical circuit
operational amplifier
light
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
AU70918/87A
Other versions
AU7091887A (en
Inventor
Leroy Lind
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Scotsman Group LLC
Original Assignee
King Seeley Thermos Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by King Seeley Thermos Co filed Critical King Seeley Thermos Co
Publication of AU7091887A publication Critical patent/AU7091887A/en
Application granted granted Critical
Publication of AU601413B2 publication Critical patent/AU601413B2/en
Assigned to SCOTSMAN GROUP, INC. reassignment SCOTSMAN GROUP, INC. Alteration of Name(s) in Register under S187 Assignors: KING-SEELEY THERMOS CO.
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25CPRODUCING, WORKING OR HANDLING ICE
    • F25C5/00Working or handling ice
    • F25C5/18Storing ice
    • F25C5/182Ice bins therefor
    • F25C5/187Ice bins therefor with ice level sensing means
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01FMEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F23/00Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
    • G01F23/22Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
    • G01F23/28Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring the variations of parameters of electromagnetic or acoustic waves applied directly to the liquid or fluent solid material
    • G01F23/284Electromagnetic waves
    • G01F23/292Light, e.g. infrared or ultraviolet
    • G01F23/2921Light, e.g. infrared or ultraviolet for discrete levels
    • GPHYSICS
    • G05CONTROLLING; REGULATING
    • G05DSYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
    • G05D9/00Level control, e.g. controlling quantity of material stored in vessel
    • G05D9/12Level control, e.g. controlling quantity of material stored in vessel characterised by the use of electric means

Description

ii C O M M O N W E A-L T H OF A U-S T R A L I A.
PATENT ACT 1952 COMPLETE SPECIFICATION (Original) FOR OFFICE USE 601413 Class Int. Class Application Number: Lodged: 7oql/9191 Complete Specification Lodged: Accepted: Published: Priority: Related Art: I is d oc I1n t co0nt1.a is the jarEJ ndnien s made under L &'trn 49 and is correct for [printing.
I
I'-
Name of Applicant: Address of Applicant: KING-SEELEY THOMOS CO., QUEEN PRODUCTS DIVISION, 2700 Sanders Road, Prospect Hill, Illinois, United States of America LeRoy LIND Actual Inventor(s): Address for Service: DAVIES COLLISON, Patent Attorneys, 1 Little Collins Street, Melbourne, 3000.- Complete Specification for the invention entitled: 'ICE BIN LEVEL SENSOR" The following statement is a full description of thi.; invention, including the best method of performing it known to us -1- N1 td la 1 ICE BIN LEVEL SENSOR 2 3 Background of the Invention 4 This invention relates to an electrical circuit and particularly to one that functions to detect the amount of 6 ice accumulated in the ice bin of a refrigeration apparatus 7 having an automatic ice making function.
8 Many modern freezers used in industrial and residential 9 applications include automatic ice making systems which deposit ice cubes into an ice bin for storage. A means for 11 controlling the output of these types of ice making systems 12 is needed to enable ice being consumed to be replenished and 13 to prevent the mechanism from overproducing. Many existing 14 designs for such controls employ means for weighing the ice 15 bin or employ paddle-type sensors which detect the height of 16 the accumulated pile of ice cubes. Although these devices 17 generally perform satisfactorily, it is desirable to provide 18 an improved ice bin level sensor which controls an ice 19 making machine and operates without moving parts and it is an object of the present invention to provide such a sensor.
21 According to the present invention, there is provided 22 an electrical circuit for use in a refrigeration device 23 having an ice making device, an ice bin for receiving ice 24 produced by said ice making device, said electrical circuit controlling said ice making device to cause said device to 26 produce ice when the accumulated ice in said bin is below a 27 predetermined level, said circuit comprising: Iii 28 a light source, 29 a light sensitive element spaced from said light source such that when said ice is above said predetermined level, 31 the light path between said light source and said light 32 sensitive element is interrupted, said light sensitive 33 element producing a current proportional to the level of 34 light it receives, current-to-voltage convertor means which receives a 36 current signal from said light sensitive element and 3 -\37 converts said signal to a voltage signal, 38 9007O3,kxspe.008,king.1,1 lb 1 2 3 4 6 7 8 9 11 12 13 14 16 17 18 19 21 22 23 S 24 26 27 28 29 31 32 33 34 36 37 S38 peak detector means for detecting the peaks of said voltage signal from said current-to-voltage means, threshold detector means for passing the signal from said peak detector means only if said signal exceeds a predetermined threshold, and time delay means which provides an output which controls said ice making apparatus only after the signal from said threshold detector means exists for at least a first predetermined time duration, such that when said ice is below said predetermined level for said first predetermined time duration, said time delay means activates said ice making apparatus, said time delay means further maintaining said output until said signal from said threshold detector does not exist for a second predetermined time duration, such that when said ice is above said predetermined level for said second predetermined time period, said time delay means deactivates said ice making apparatus.
In accordance with embodiments of the present invention, an ice bin sensor circuit is provided which enables the detection of the quantity of ice in an ice bin using a beam of infrared light which is interrupted when the ice bin is filled to capacity. The circuit automatically controls the ice making apparatus to maintain a desired quantity of available ice cubes. Although light interrupter circuits are well known, the circuit according to this invention is efficiently designed for its intended function and employs readily available and inexpensive components.
In order to prevent improper operation due to transient interruptions of the light beam, the circuit includes a time delay function. The circuit further includes means for preventing improper operation caused by ambient light, and includes a mechanism for rapid testing of the circuit during production or 900703.kxlspe.008.king. 1.2 h.
in-the-field malfunction diagnosis.
Additional benefits and advantages of the present invention will becc ne apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiment, and the appended claims, taken in conjunction with the acompanying drawings.
Brief Description of the Drawing s Figure 1 is a pictorial view showing a representative autamatic ice making device; Figure 2 is a block diagram of the various functional subparts of the circuit according to this invention; and Figure 3 is a detailed schematic drawing of the circuit according to this invention.
Detailed Description of the Invention With particular reference to Figure 1, refrigeration apparatus is shown which includes an automatic ice maker device having a discharge port 14. In order for refrigeration apparatus 10 to operate automatically, it is necessary to provide some means for controlling the output of the ice making device such that it will provide ice when desired, but will not overfill ice bin 16. In iccordance with this invention, such control is provided by an infrared N transmitter 18 and an infrared sensitive photo detector 20 which are mounted to opposing walls within ice bin 16. When the accumulated pile of ice cubes is below the line of sight 12 between transmitter 18 and photo detector 20, the ice device is actuated to produce ice cubes. This action proceeds until the infrared light beam is interrupted, at which time the ice making function is caused to cease. Transmitter 18 and photo detector 20 are controlled by ice bin sensor circuit 22. The components making up ice bin sensor circuit 22 are described in detail below.
Figure 2 is a block diagram of the various functional subparts of circuit 22, whereas Figure 3 is a detailed schematic diagram of the circuit showing each of the individual comnpnents. Ice bin sensor circuit 22 is comprised of three primary circuits: power supply 24, mR transmitter driver circuit 26, and detector circuit 28, each of which are preferably mounted to a single PC board 34.
As shown in Figure 3, power supply 24 includes step-down power transf ormer 30 which is connected to several pins on terminal strip 32 fitmounted to PC board 34. Power fromn step>-down transformer 30 is conducted to full wave bridge rectifier 36 where it is cornverted to a DC voltage having an average value of slightly greater than 12 volts. Filter capacitors 37 and 38 are used to decrease the ripple of the rectified signal. Additional filtering and voltage co~ntrol is provided through use of IC voltage regulator 40. Diode 41 is provided to inhibit negative going spikes which may be generated by circuits connected to power supply 24.
IR driver circuit 26 emplorys a well-known "555" timer 42 which, to e h r i h ad i i na aponents, is us d in circuit 26 as a oscillator 44 which operates driver transistor 54. Tiumer 42 functions by monitoring the level of charge of external timing capacitor 46. The output of timer 42 is high when capacitor 46 is charging which occurs by current flow through resistor 48. Diode 50 is provided such that the criarciing of capacitor 46 occurs only through resistor 48 by bypassing resistor 52. Once capacitor 46 reaches approximately two-thirds the *t 4 44
I
1 1 1 II I I 4 4
III.
II
I I voltage of the supply, the output of timer 42 becomnes low, and the timer switches to a capacitor discharging mode. Discharging of capacitor 46 occurs through resistor 52. The use of diode 50 causes capacitor 46 to charge very rapidly and discharge much more slowly. This operation of timer 42 generates a rectangular pulsed output having a very lowJ percentage duty cycle, i.e. narrow positive voltage spikes are separated by' relatively long dw~ell periods. The output of timer 42 controls the base current of driver transistor 54 through resistor 56. The rectangular pulsed output which drives the base of driver transistor 54 switches a twelve volt signal fran power supply 24 to cause current to flow through IR transmitter 18 which is preferably a light emnitting diode (LED) and is connected to several pins of terminal strip 32. LED 58 is also provided as an auxiliary mR transmitter which is mounted on PC board 34 which may be used for future applications but is not mnployed in connection with the present invention.
Detector circuit 28 is comprised of a numnber of integrated operational amplifiers (multipurpose analog amplifiers) such as the National Semiconductor Model LM 324 having four individual operational amplifiers (op amps) packaged together. Photo detector 21 provides a variable resistance dependent on its exposure to light within its sensitive range. Auxiliary photo detector 20 -may be provided for future applications. Photo detector 21 provides a variable current signal which is applied to the inverting (minus) terminal of op amp 60 which functions as a current-to-voltage convertor 62. The nonr-inverting (plus) terminal of op, amp 60 is provided with a constant voltage biasing source of approximately eight volts which is set by the voltage division provided by resistors 64 and 66. Variations in current through photo detector 21 -4caused by exposure to the pulsating light from IR transmitter 18 results in op amp 60 providing a positive going only alternating voltage output Isignal. Feedback resistor 70 provides gain control for op amp Capacitor 68 acts as an ambient light level blocker 72 by removing DC components from the output of op amp 60 which could result, for example, due to constant or low~ frequency ambient light inputs to phioto detector 21. Capacitor 71 and resistor 80 are provided for additional signal conditioning.
Op amp 74 is used as an amplifier 76 of the signal from capacitor S68, boosting it to a desired level using feedback resistor 78. Resistors 78 and 82 adjust the input levels to op amp 74 to desired magnitudes. Op .~amps 84 and 86 are configured to provide a peak detector circuit 88 by emplo~ying diodes 90 and 92, capacitor 94 and resistors 91, 93 and 95. The output of peak detector circuit 88 is a DC level with some sawtooth V rippling interposed on it due to charging of capacitor 94. The output of the peak detector circuit 88 from op amp 86 is positive when an alternating signal is received by photo detector 21. When this condition 4 occurs, voltage is supplied to LED 96 and through resistor 97 which is mounted to PC board 34 to provide an indication that ice bin 16 is not filled.
Op amp 96 is emploiyed as a threshold detector 98 by comparing the ,~signal provided by op amp 86 with a reference voltage provided by a voltage divider defined by resistors 102 and 104. Op amp 96 provides a positive output once the difference between the signals supplied by op amp 86 and the reference signal becomies positive. A time delay circuit 106 is defined by resistor 108, capacitor 110 and op, amp 112. The values of resistor 108 and capacitor 110 are chosen such that the voltage signal applied to the minus terminal of op, amp 112 changes slowly. When the output of op amp 96 goes positive, time delay circuit 106 causes the input signal to op amp 112 to rwiain below the reference voltage for a predetermined period of time, for example, about 10 seco~nds. Similarly, when the output of op amp 96 goes negative, the input signal to op amp 1.12 remains above the reference voltage for a predetermined time period. When the signal applied to the minus terminal of op amp 96 exceeds the reference voltage, a negative output is provided bry op amp 112. Resistor ,,113 is provided for gain control of op amp 112. Terminal 99 is provided which is connected to the minus input of op amp 96 and enables a test .signal to be applied to check the operation of circuit 22.
The signal from the output of op, amp 112 is transuitted to a pair of op amps 114 and 116 which comprise a driver-inverter 118. The signal from op amp 112 is divided and applied to both negative inputs of op amps 114 and 116 which ompare this signal with the reference signal applied across resistor 104. Op amps 114 and 116 drive relay driver transistor 120 through resistors 122 and] 124. Transistor 120 co~ntrols current flow to relay 126 which operates the ice making apparatus used with this invention. Diode 128, capacitor 130 and resistor 132 are provided to dampen electrical noise generated byj operation of the high inductance relay 126.
Ice bin sensor circuit 22, as described above, automatically operates an ice making device bry continually monitoring the level of retained ice and periodically activating and deactivating the ice maker to maintain a desired ice supply level. When light from IR transmitter 18 strikes phloto detector 21 for a time exceeding the time delay, the ice maker is activated to produce ice. The time delay function prevents -6llormuLUu~- inadvertent operation of the ice making device in response to transient exposure of photo detector 21 to light which may occur when ice is being removed from ice bin 16. When the ice bin becomes filled, light from IR transmitter 18 is interrupted. If the light beam interruption exists for a period of time exceeding the time delay, the ice maker is deactivated.
The time delay in deactivating the ice maker is desirable to avoid response to transient conditions, and also to allow a small degree of overfilling of the ice bin to reduce cycling of the system.
While the above description constitutes the preferred embodiments oo2.% of the present invention, it will be appreciated that the invention is susceptible to modification, variation and change without departing from o0000 the proper scope and fair meaning of the acccmpanying claims.
0 a 0 0 pt 0 0 0 0 -7-

Claims (17)

1. An electrical circuit for use in a refrigeration device having an ice making device, an ice bin for receiving ice produced by said ice making device, said electrical circuit controlling said ice making device to cause said device to produce ice when the accumulated ice in said bin is below a predetermined level, said circuit comprising: a light source, a light sensitive element spaced from said light source such that when said ice is above said predetermined level, the light path between said light source and said light sensitive element is interrupted, said light sensitive element producing a current proportional to the level of light it receives, current-to-voltage convertor means which receives a current signal frno said light sensitive element and converts said signal to a voltage signal, peak detector means for detecting the peaks of said voltage signal from said current-to-voltage means, threshold detector means for passing the signal from said peak detector means only if said signal exceeds a predetermined threshold, and i time delay means which provides an output which controls said ice making apparatus only after the signal from said threshold detector means exists for at least a first predetermined time duration, such that when said ice is below said predetermined level for said first predetermined time duration, said time delay means activates said ice making apparatus, said time delay means further maintaining said output until said signal from said threshold detector does not exist for a second predetermined -8- i time duration, such for said second deactivates said ice that when said ice is above said predetermined level predetermined time period, said time delay means making apparatus. I ii
2. The electrical circuit according to claim 1 further comprising an oscillator for driving said light source to produce a pulsed light output and direct current blocking means for receiving said voltage signal from said current-to-voltage convertor means and passes only alternating voltage components, thereby functioning as an ambient light level blocker.
3. The electrical circuit according to claim 1 wherein said light source generates infrared frequency light.
4. The electrical current-to-voltage convertor amplifier. circuit means according to claim 1 wherein said comprises a first operational II I j) The electrical circuit according to claim 2 wherein said direct current blocking means comprises a capacitor.
6. The electrical circuit according to claim 2 further comprising an amplifier which amplifies the signal from said direct current blocking means and provides an amplified signal to said peak detector means. -9- i II__~
7. The electrical circuit according to claim 6 wherein said amplifier is a second operational amplifier.
8. The electrical circuit according to claim 1 further comprising a visible light emitting means which is energized by the signal from said peak detector means, thereby providing an indication that said light sensitive element is receiving a signal from said light source.
9. The electrical circuit according to claim 1 wherein said time delay means comprises a resistor-capacitor network. I
10. The electrical circuit according to claim 1 further I, coprising a driver inverter which receives a signal from said time delay means and drives a driver transistor which controls said ice maker.
11. The electrical circuit according to claim 10 wherein said driver transistor provides a signal to a relay controlling said ice maker.
12. The electrical circuit according to claim 1 wherein said peak detector comprises a third and a fourth operational amplifier.
13. The electrical circuit according to claim 1 wherein said threshold detector comprises a fifth operational amplifier.
14. The electrical circuit according to claim 9 wherein said time delay means further comprises a sixth operational amplifier. The electrical circuit according to claim 10 wherein said driver-inverter canprises a seventh and, an eighth operational aulifier.
16. The electrical circuit according to~ claim 1 wherein said first and secondIamWe time dura .ons are approximately equal. A -11-
17. An electrical circuit for use in a refrigeration device having an ice making device, an ice bin f or receiving ice produced by said ice making device, said electrical circuit controlling said ice making device to cause said device to produce ice when the accumnulated ice in said bin is below~. a predetermined level, said circuit ocnprising: a light emitting diode light source which produces light of infrared frequencies, a first driver transistor controlling current flow~ to said light source, an oscillator driving said first driver transistor to control *:,~1,said first driver transistor to produce a pulsed light output, 4 a photo detector spaced from said light source such that when said ice is above said predetermined level, the light Feth between said light source and said photo detector is interrupted, said ph~oto detector producing a current proportional to the level of light it receives, a first. operational amp1ler operating as a current-to-voltage convertor which receives a current signal fromn said photo detector and converts said siqr~i1 to a voltage signal, a capacitor couplA~ to the output of said first operational amplifier thereby passing only alternating voltage signal canponents and functioning as an ambient light level blocker, a second operational amplifier for amplifying the signal from said capacitor, third and fourth operational amplifiers coupled to a pair of diodes functioning as a peak detector for detecting the peaks of said signal from said second operational amplifier, a fifth operational amplifier coupled to said fourth operational -12- amplifier and functioning as a threshold detector for passing the signal from said fourth operational amplifier only if said signal exceeds a predetermined threshold, a time delay mreans including a resistor capacitor network and a sixth operational amplifier which provides an output after the signal frcm said fifth operational amplifier exists for at least a first predetermined time duration, and continues to provide said output until said signal from said fifth operational amplifier is interrupted for at least a second -44 41* predetermined time duration, a driver including a seventh operational amplifier which receives a signal fraxn said sixth operational amplifier, a relay driver transistor controlled b~y said seventh operational amplifier, and a relay coupled to said relay driver transistor' whereb~y whe .n said ice is belcw said predetermined level for said first predetermined time duration, said relay driver transistor actuates said relay and said ice making apparatus to produce ice and when said ice is above said predetermined level for said second predetermined tine duration, said relay driver transistor deactivates said relay and said ice making apparatus.
18. The electrical circuit acco~rding to claim 17 further comprising an eighth operational amplifier connected in parallel with said seventh operational amplifier and operating with said seventh operational amplifier to control said seco~nd driver transistor. -13-
19. The electrical circuit according to claim 17 wherein Said first and second pred~etermined time durationts are approximately equal. An electrical circuit substantially as hereinbefore described with reference to the drawings. ~~Li~-him thzrzr 0 40 00 0 0 4 0 4 0 ~t 0 0. 04 0*9 0 000 0 41 0 00 00 o 000 00 00 0 4*0 0 00 0 0 *0 04 00 0 4 060 oO 4 0 ii 11 0 e Dated this 31st day of March, 1987 KINqG-SEELEY THiERMOS CO., By Its Patent Attorneys, DAVIES COLLISON Li -14-
AU70918/87A 1986-04-03 1987-03-31 Ice bin level sensor Ceased AU601413B2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US84791786A 1986-04-03 1986-04-03
US847917 1986-04-03

Publications (2)

Publication Number Publication Date
AU7091887A AU7091887A (en) 1987-10-08
AU601413B2 true AU601413B2 (en) 1990-09-13

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AU70918/87A Ceased AU601413B2 (en) 1986-04-03 1987-03-31 Ice bin level sensor

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JP (1) JPS62237264A (en)
AU (1) AU601413B2 (en)
BE (1) BE1003058A3 (en)
BR (1) BR8701523A (en)
CA (1) CA1267203A (en)
CH (1) CH674074A5 (en)
DE (1) DE3711241A1 (en)
FR (1) FR2596857B1 (en)
GB (1) GB2188724B (en)
IT (1) IT1202718B (en)
MX (1) MX168749B (en)
SE (1) SE460925B (en)
ZA (1) ZA871865B (en)

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IT1230039B (en) * 1988-07-21 1991-09-24 Frimont Spa AUTOMATIC EQUIPMENT FOR ICE CUBE PRODUCTION.
IT1244433B (en) * 1990-09-12 1994-07-15 Castel Mac Spa ELECTRONIC ICE LEVEL CONTROL DEVICE IN AN ICE COLLECTION CONTAINER FOR THE PRODUCTION OF ICE IN FLAKES
ES2108765T3 (en) * 1991-10-22 1998-01-01 Thermotech International Pty L COOLING SYSTEM.
DE9114777U1 (en) * 1991-11-27 1993-03-25 Kluee, Ulrich, Dipl.-Ing., 2054 Geesthacht, De
US5671606A (en) * 1995-09-18 1997-09-30 Lancer Corporation Method and apparatus for sensing and controlling the level of ice in an ice dispenser
US8646285B2 (en) 2006-09-04 2014-02-11 Lg Electronics Inc. Control apparatus for taking out ice of refrigerator and method thereof
WO2008035942A2 (en) 2006-09-20 2008-03-27 Lg Electronics, Inc. Refrigerator

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US3045445A (en) * 1960-12-19 1962-07-24 Carrier Corp Ice making
US3525232A (en) * 1968-08-30 1970-08-25 Gen Electric Automatic ice maker control means
US3731496A (en) * 1972-01-31 1973-05-08 Gen Electric Photoelectric ice level sensor

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IT1125671B (en) * 1978-11-24 1986-05-14 Loomhurst Ltd CONDENSATE DRAINAGE VALVE
US4238930A (en) * 1978-12-26 1980-12-16 Whirlpool Corporation Ice maker apparatus
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US3045445A (en) * 1960-12-19 1962-07-24 Carrier Corp Ice making
US3525232A (en) * 1968-08-30 1970-08-25 Gen Electric Automatic ice maker control means
US3731496A (en) * 1972-01-31 1973-05-08 Gen Electric Photoelectric ice level sensor

Also Published As

Publication number Publication date
JPH0144983B2 (en) 1989-10-02
JPS62237264A (en) 1987-10-17
GB8705896D0 (en) 1987-04-15
FR2596857B1 (en) 1992-04-30
ZA871865B (en) 1987-09-03
GB2188724A (en) 1987-10-07
DE3711241A1 (en) 1987-10-15
GB2188724B (en) 1989-11-15
AU7091887A (en) 1987-10-08
SE8702772D0 (en) 1987-07-06
FR2596857A1 (en) 1987-10-09
CA1267203A (en) 1990-03-27
MX168749B (en) 1993-06-07
IT1202718B (en) 1989-02-09
BR8701523A (en) 1988-01-19
DE3711241C2 (en) 1991-03-21
SE460925B (en) 1989-12-04
CH674074A5 (en) 1990-04-30
BE1003058A3 (en) 1991-11-12
IT8719902A0 (en) 1987-03-30
SE8702772L (en) 1989-01-07

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