USRE20212E

USRE20212E - raney

Info

Publication number: USRE20212E
Authority: US
Publication date: 1936-12-22

Description

Dec. 22, 1936. Q RANEY Re. 20,212

REFRIGERATOR CONTROL Original Filed April 29, 1932 2 Sheets-Sheet 1 3 wuc wfo v @LZM C? @any Gum/wen;

Dec. 22, 1936. E. -c. RANEY Re. 20,212

napnmniznoa con'moL Original Filed April 29, 1932 2 Sheets-Sheet 2 ReisauedDec.22,l936

I ass-momma coirraor. m 0. Barney, Columbus, om. amignsr u lancolnoorporatelcolumhmohhacorporationofohlo Original No. 1,877)", dated September 20, 1.32, Serial No. 6.8.15, April 29, 1932. on for rdlue October 30, 1933, Serial No. 895,93

Claims.

My invention relates to control systems for controlling the cyclic operations of refrigerators to produce periodic defrosting to prevent more than the formation of a slight amount of frost on the surfacm of the cooling units of refrigerators and thus producea greatly increased refrigerating eiliciency.

. The object of the invention is to provide an automatic control device which not only maintains refrigerating temperatures at desired values. but also periodically raises the temperature of the cooling unit of the refrigerator sufiiciently to defrost the refrigerator, and then restores it to I the refrigerating temperatures. The invention is also has for its object to provide a means for adjusting the refrigerating mean temperature without aflecting the periodic defrosting temperature. the adjusting means being so compensated that the defrosting high temperature limit will remain practically constant regardless of the adjustment of the refrigerating temperature range of the refrigerator.

Thus, by my invention, I provide a defrosting means that will enable initiation of the defrosting cycle at a desired temperature and a means for 'adjmting the refrigerating temperatures without affecting the high temperature limit occurring at the end of the defrosting cycle. The invention thus provides means for raising the normal refrigerating upper temperature limit to a materially higher temperature and a compensating means whereby the said higher temperature limit remains at a practically fixed point regardless of the adjustment of the temperature limits of the normal-operating refrigerating cycle. It more particularly provides a defrosting means includ-' ing switch closing resistant opposing means for causing the rise of the refrigerating temperature at which the switch is normally closed to a 40 defrosting temperatin'e and a member for inversely affecting the closure means of the switch to provide for the variation of the normal refrigerating temperature and yet maintain a substantially constant defrosting temperature.

My invention also provides a switch mechanism or means for opening and closing the circuit of the motor that drives the compressor of the refrigerator in response to the changes in the refrigerating and defrosting temperatures and also in 5 response to the flow of a current which, if unduly continued, would injure the motor that drives the compressor of the refrigerating apparatus.

The invention also provides means whereby the circuit of a motor usedto operate the compressor 55 may be closed at desired temperatures and opened (Cl. OH)

atatemperaturelowerthantheselectedtemperature. The closing temperatures may be above or below degrees l"., or normal water freezing temperature. The opening and closing temperatures are maintained for periods of time tops- 5 rated by intervals during which the switch mechanism or means maintains the circuit open to permit a materially greater rise in temperature thanthatpermittedduringsaidperiods. Thisis accomplished by a suitable resistant device that 10 at intervals resists closing movements of the switch mechanism produced bya pressure device and enables removal of frost that gathers on the refrigerating unit.

The invention more particularly provides a pair 15 of resistance devices, one or both of which are operable to resist the switch-closing movement of an electrically operated refrigerator, and means for adjusting the said resistance devices to producethesameproportionatechangeinthesaid 0 resistance devices but in opposite degree by means of which a predetermined resistance to the switch-closing movement will be produced when both of the resistance devices operate to resist the switch closing movement, notwithstanding varia- 25 tions in the resistance to the switch closing movement when but one of the resistance devices operates alone to resist the switch closing movement. The invention thus provides means for normally maintaining the refrigerating temperature be- 30 tween adjustable temperature limits, and means for altering one of the said temperature limits to produce a predetermined abnormal temperature without affecting the other of the said temperature limits, and means for adjusting the normal 5 refrigerating temperature without altering the predetermined abnormal temperature limit.

The invention also consists in the provision of other features that will appear from the following description and upon examination of the 40 drawings. Structures and wstems containing the invention may partake of different forms and still embody the invention. Tolllustrate a practical application of the invention, I have selected a system containing my invention, it being under- 5 stood that variations may be made without departing from the spirit of the invention. The particular system and parts of the structure selected as illustrating an embodiment of my invention are described hereinafter and shown in the drawings.

Fig. 1 illustrates the structure embodying the invention and shows 0 tically the connections of the structure in a apparatus. Fig. 2 illustrates parts of the switch mechanism for controlling the circuit of the motor and shows the relative location of the said parts when the switch is open. Fig. 3 illustrates in chart form the cyclic operation of the refrigerator during desired selected normal operations and also defrosting operations that are separated in their occurrence by a plurality of normal operations.

As shown diagrammatically in the drawings, a refrigerator i is provided with a cooling unit 2. A compressor I operates to circulate a refrigerant medium through the cooling unit I to reduce its temperature in the manner well known in the art. The compressor I is driven by a motor t that is subiect to the control of a switch mechanism I. The switch mechanism 5 is operated by the changes in temperature of the cooling unit I and by an excess ilow of current through the motor I.

The motor that drives the compressor of the refrigerating apparatus is controlled by the temperature produced by operation of the compressor and also by the flow of the current in the circuit of the motor. A bellows II is connected to a suitable bulb I! by a tube II and they are filled with a suitable low boiling point fluid. The bulb i2 is located in close heat transferring relation with the cooling unit 2 of the refrigerating apparatus. The fluid in the bulb and in the bellows varies in pressure as the temperature of the portion located in the bulb changes. The pressure of the fiuid in the bellows ll operates through the lever ll to open and close the switch mechanism I. The lever I5 is pivotally supported on a suitable pin ll and is provided with a snap switch arm I! that is drawn by means of a spring it into a notch ll formed on a part of the lever II. The springisalsoattachedtoabarilthathasone end located in a notch 2i formed in the lever Ii. Thespring ll operates to hold the ends of the bars in thenotches I. and Il. When the pivoted ends of the bars. that is, the ends located in the notches II and II, pass the spring it. when moved in either direction, the spring ll operates to open or close the switch mechanism I.

To enable adjustment of the responsiveness of the bellows, a tension spring It is connected to thelever II andtoaplateilsoastodrawthe lever ll against the end of the bellows and to resist the expansive movement of the bellows. The plate I! is adjusted to adjust the spring 14 to vary the pressure of the lever i! on the bellows. A contact member it, forming a part of the switch mechanism I, is connected to one end of the bar ii and is adapted to electrically connect the fixed contacts 21 and 28. When the lever I! is depressed by the operation of the spring 24 upon the contraction of the bellows i to cause thepivotpointsofthebars l'l andiltopassthe center of the spring is, the circuit through the switch mechanism will be opened. Adjustment ofthetensionofthespringfl adjnststhetemperature at which the switch closes and at which the switch opens in as much as the spring it maintains a substantially constant pressure differential within the bellows between the closing and opening of the switch during the normal expansive and contractile movents of the bellows. Theupward movements of the bars l1 and 2. are limited by suitable stops located on a pivoted arm 8.. The position of the arm 8. may be adjustedbyascrewiltolocatethebars l1 and II inpoaition so that when the lever I! is raised andthepivotpointsofthebars i'l andilpas's the center of the spring II, the movable contact 28 will be snapped downwardly so as to close the circuit of the motor 4 that drives the compressor which circulates the refrigerant medium through the cooling unit 2 according to the temperature produced by the cooling unit.

By the repeated cyclic operations of the compressor, due to the opening and closing of the circuit of the motor, the moisture that condenses and freezes on the cooling unit 2 gradually accumulates as frost, and to defrost the cooling unit, I have provided means for periodically preventing closing of the circuit of the motor until the temperature of the cooling unit has raised suillciently to cause the frost to melt thereby preventing accumulation of more than a film of frost.

To produce periodic defrosting I have provided means for periodically increasing the resistance to the expansive movement of the bellows at intervals separated by a predetermined number of cyclic refrigerating operations of the compressor and th restoring the control of the motor and the compressor to the refrigerating temperature control to produce'the normal cyclic refrigerating operations. Increasing the resistance to the expansive movement of the bellows increases the pressure of the gas in the bellows required to move the lever II to operate the contact I! and, consequently. the contact will not close the circuit until the temperature of the cooling unit I rises to a point that corresponds to the total resistance to which the bellows is subjected. In order to produce an increased load on the bellows at intervals separated by a predetermined number of cyclic operations of the motor and the compressor, the lever II operates a member that is moved step by step, and when the member is moved to a certain point, it operates to connect a second resistant member to the lever I! which cooperates with the spring ll to resist movement of the lever I! to close the circuit of the motor until the pressure on the bellows, and the temperature of the cooling unit rise to points higher than that at which the bellows will close the circuit when loaded only by the spring II.

In the form of construction shown, a ratchet wheel 84 is rotatably supported on one end part of a lever IS. The lever I is pivotally supported on a bracket It and the compression spring I! is disposed between the other end part of the lever SI and the plate II to which the tension spring ll is connected. The plate II is adjustably supported on a screw it. The screw 38 is rotatably supported in a suitable frame or shell and may be rotated by a knob ll located on the outside of the shell. A suitable pointer ll may be connected to the knob Cl and a stop 42 may be connected to the shell and in position to be engaged by the pointer for limiting the adjustment of the screw I by means of the knob ll. Further adjustment may be made by the removal of the pointer ll from the knob an; rotation of the screw and reconnection of the pointer to the knob at another point on the knob. Since the spring 24 is a tension spring, and the spring 81 is a compression spring, adjustment of the plate II operates to increase the pressure of one spring and decrease the pressure of the other spring. dependent upon the movement of the plate ll.

The ratchet wheel N is operated bymeans of a slidably supported pawl ll thatis spring pressed bymeansof the spring llthat operatestoraise pawl ll operates to engage the teeth of the pawl.

II as it is stepped around by the movement of the pawl II. The catch pawl I. is also spring biasedbymeansofasprlnglltoholdtheratchet It in the position to-which it is turned by the operations of the lever I.

In order to subject the switch opening movements of the lever I to the control of the ratchet 34. the lever II is provided with a link or pivoted arm I, and the ratchet wheel 34 is provided with -'a projection it that at one point in the rotation of the ratchet wheel engages the projection I1 formed on the end of the arm ll. If desired, the end of the projection It may be made v-shaped to insure engagement of the pro- Jections I. and 51 when the lever II is raised egistration or alignment. us engaged by the ratchet subsequent to their When the arm II is wheel, movement of the lever II is resisted by and the compressor lowers the temperature in normal mean temperature of the refrigerator vmay be varied as may be desired by rotation of the knob ll to vary the tension of the spring II. This, however, correspondingly varies inversely the pressure of the spring 31 with the result that if the tension of the spring 24 is decreased or increased to lower or raise the normal mean temperature of the refrigerator, the high limit of the defrost temperature will remain substantially unchanged. As indicated in Pig. 3,

the normal refrigerating cycles may be adjusted to produce switch operations at any desired temperature whereby the required coldness may be produced in the refrigerator. Fig. 3 indicates substantially the response to adjustments that -may be made. The line indicating the cycles of the apparatus will vary according to operating conditions of the apparatus and the switch and according to room temperatures. The chart disproduce opening at 24 and switch closing at 36 which produces an average temperature ,below 32 by the cycleaindlcated at 0. Following the normal cycles of operations. the chilling element is again defrosted by raising the switch closing temperature to 45 as indicated at h not withstanding the normal high temperature cycles. The chart indicates two extreme cyclic temperature operations of a refrigerator, namely between 0 and 12 and between 24 and 38 and an intermediate operation between 15 .and 27 sting temperature limits and the proper defrosting temperature occuring at separated intervals will be insured.

The switch mechanism I will not only maintain the refrigerating cyclic operations of the refrigerating apparatus and the periodic defrosting of the cooling unit, but'also will protect the motor as against an overload.- The switch mechanism I may be operated to open the circuit of the motor by the operation of an overload heat coil 02 which is connected in the circuit of the motor 4. The heat coil 02 surrounds a shell in which a fixed pin is inserted and on which is located a ratchet 63. The ratchet is held from rotation normally by a low temperature melting solder that interconnects the shell to the pin. when the heat of the coil 82 exceeds a predetermined value, the solder is melted so as to free the ratchet wheel and permit its rotation, in the manner well known in the art. The ratchet wheel is engaged bya pawl it connected to a slidable frame 85 that is subject to the tension of the spring 06 that operates to draw on the periphery of the ratchet wheel 03. When, therefore the ratchet wheel is liberated by the melting of the solder, the ratchet wheel I! is rotated and the frame 65 is moved by the spring 6.

A lever 61 is pivotally supported by means of a pin ll and has an arm 8! that is engaged by the frame I to rotate the lever 01. The lever also has an arm III to which is connected a bar II that carries a movable contact II that is adapted to electrically connect the contacts and BI to close the circuit of the motor. The bar II is connected to a rocker bar 13 by a spring N and the rocker bar is pivotally connected to the arm 18 of the lever 61. when, therefore, the frame is released by releasement of the ratchet wheel 68, the lever Cl is rotated so as to lower one end of the bar ll below the point of connection of the spring It with the rocker bar 18 and the spring 14 operates to ralse'the bar II and open the circuit of the motor at the points I and ll.

'Ihisoperatestoswingtheannllofthe lever t1 againsttherockerbarll andlifttheendofthe rockerbar'ilconnectedtothearm'llofthe lever II. The partb berestored when the heatcoilflandthesolderlnvecooledsuiiiciently to fixedly hold the ratchet wheel It by manually moving the lever II. The arm It moves the frame I against the tension of the springltandthearmllraisesoneendofthe bar'li toraisethesaidendofthebarli above the spring ll. The spring It then causes the contact If to snap against the fixed contacts and close the circuit of the motor between the points It and ti. Assuming that the temperature of the refrigerator has raised sufiiciently to cause thebeiiows lltoclosethecircuitofthemotor between the points 21 and II, the motor 4 will immediately start the operation of the compressor I to lower the temperature of the refrilerator. v

Thus by my invention, I have provided a switch mechanism that will insure protection of the motor as against undue hating and injury and. at the same time, maintain eiiicient operation of the refrigerator and eliminate the inconvenience of constant attendance of the user to the defrosting operations.

I claim- 1. In a control system, means for maintaining a normal operating refrigerating .cycle between fixed temperature limits, means for periodically modifying the upper temperature limit, mans for adjusting the temperature range of the normal operating cycle, a compensating means whereby the upper temperature limit of the periodic cycle remains at a practically fixed value regardless of adjustment of the normal operating cycle.

2. In a refrigerator control, a switch, a pressure mam including a resistant member for operatingthe switchtonormallymaintainasubstantially constant refrigerator temperature, a defrosting means including a resistant member for periodically raising the temperature at which theswitchisclosedbythepre'ssuremeanaa member for inversely vary n the effectiveness oftheresistantmemberstovarythenormaltemperatureofciosingtheswitchbythepressure means and maintaining a substantially upper limit of defrosting temperature.

3. In a refrigerator control, a switch, a pressure mans for operating the switch, means for periodically raising the refrigerating temperature at which the switch is closed and adjustable mans for varying the temperature at which the pressuremeansoperatestheswiteha'ndmain- 'taining substantially constant the periodic closingtemperatureoftheswitch.

4.Inarefris ratorcontrol,aswitch,apressure operated bellows for operating the switch, a resistance device for normally resisting the switch closing movement of the bellows. a second resbtance device. means for periodically connecting the second resistance device to furtherresisttheswitchcloeingmovementofthe bellows. and mans for adjusting the said resistance devices toproduce the same P p rtionatechangeinoppositedegreeineachofthesaid resbtancedevices.

ii. In arefrigerator, a switch, a pressure operatedbeliowsforoperatingth'eswimaratchet wheel, mans including a spring for yieldingly supportingtheratchet wheel for rotatable movementsandmovementstransversetotheaxisof rotationofthewheel,apawlconnectcdtothe switch for rotating the ratchet wheel, the ratchet wheelhavingapartengas bytheswitchat a point in its rotation for resisting closing movements of the switch by the bellows. i

6. In a refrigerator control, a compremor motor,aswitchforcontrollingthecircuitofthe compressor motor, a pressure operated bellows for operating the switch. a pivoted arm, a ratchet wheel rotatably supported on the arm, a spring for resisting the movement of the arm, a pawl connected tothe switch for moving the ratchet wheel step by step by opening movements of the switch. the ratchet having a part engaged'by the switch to produce movement of the arm that is resisted by the spring upon a closing movement of the switch.

7. In a refrigerator control, a compressor mo- W, a switch for controlling the circuit of the compressor motor. a pressure operated bellows,- a spring for resisting the movements of the bellows, a pivoted arm, a spring for resisting the movement of the arm, a ratchet wheel rotatably supported on the arm, a pawl connected to the switch for moving the ratchet wheel step by step by opening movements of the switch, the ratchet wheel having a part engaged by the switch to produce movement of the arm that is resisted by the second named spring upon a switch closing movement of the bellows, and an adjustable member for increasing the effectiveness of one spring and decreasing the effectiveness of the other spring.

8. In a refrigerator control, a compressor motor, a means for automatically opening the circult of the motor upon flow of an excess current through the motor and also at a predetermined low refrigerator temperature, and means for closing the circuit at a predetermined high refrigerator temperature, and means periodically operated for preventing the operation of the last named means until the refrigerator is defrosted.

9. In a refrigerator control, a compressor motor, a mans for automatically opening the circuit ofthe motor upon flow of an excess current through the motor and also at a predetermined low refrigerator temperature and means for closing the circuit at a predetermined high refrigerator temperature, and means periodically operated for preventing the operation of the last named means until the refrigerator is defrosted and an adjustable member for varying the high temperature circuit closing means and maintaining the high limit of the'refrigerator defrosting temperature substantially constant.

10. In a refrigerator control, a compressor motor, a manually operated mans for opening and closingthecircuitofthemotorandhavingan automatic means for opening the circuit of the motorupontheiiowofanexcesscurrentand also at a predetermined low refrigerator temperatureandameansforclosing thecircuitata predetermined high refrigerating temperature to produce a plurality of normal refrigerating cycles, and a periodically operated means'for retainingtheeircuitopentoraisetherefrigerator temperature to a predetermined defrosting value and restoring the temperature to the said normal operating cycle.

11. In a refrigerator control, a compressor motor, means for controlling the compressor motor and comprising a switch means actuated by an excess current through the motor and predetermined low and hi h refriger mperatures. the control having means for raising the temperature to defrost the refrigerator, and an adtermined refrigerating temperature limits. means for periodically actuating the circuit control means for raising the higher temperature limit without aflecting the lower temperature limit.

for defrosting the refrigerator, and means for adjusting the pressure means to alter the normal predetermined temperature limits to other normal refrigerating temperature limits and maintaining substantially constant the higher periodic refrigerating temperature limit for defrosting the refrigerator.

13. A refrigerating system comprising means for starting and stopping a refrigerator at definite temperature limits successively for a predetermined number of cycles, an ,automatic means for increasing the starting temperature to a defrosting temperature for a defrosting cycle after the said predetermined number of cycles, means whereby the temperature range of the said successive cycles may be readily adjusted without changing the upper temperature limit of the defrosting cycle.

14. In a refrigerator, a switch. a pressure operated bellows for operating the switch, a ratchet wheel, means including a spring for yieldingly supporting the ratchet wheel for rotatable movements and movements transverse to theaxis of rotatlo'n of the wheel. the spring operating to resist the transverse movements of the ratchet wheel, a pawl connected to the switch forrotating the ratchet wheel. the ratchet wheel having a part engaged by the switch at a; point in its rotation to I move the ratchet wheel transverse to the axis of rotation of the ratchet wheel. the spring operating to resist closing movements of the switch by the bellows.

15. In a refrigerator control, means for opening an electric circuit at a predetermined temperature and means for closing the circuit at a predetermined temperature below 32 degrees Fahrenheit the said means operating a predetermined number of times to close and open the circuit and means for closing the circuit during a single operation at a temperature in excess of 32 degrees Fahrenheit and means for varying the opening and closing temperatures below 32 degrees Fahrenheit without changing materially the circuit closing temperature above 32 degrees Fahrenheit.

16. In a refrigerator control system means for maintaining a normal operating refrigerating cycle between fixed temperature limits, means for adjusting the temperature range of the normal operating cycle. means for raising the upper'temperature limit of the normal cycle to a materially higher temperature. a compensating means whereby the said higher temperature remains at a practically fixed value regardless of the adjustment of the normal operating refrigerating temperature.

17. In a refrigerator control. a switch, a pressure means including a resistant member for operating theswitch toproduceadesirednormal refrigerating temperature, a defrosting means including a resistant member for raising the temperatureatwhichtheswitchisciosedbythepresjustable meansforvarying the normal refrigerasure means to a defrosting temperature and a member for varying the effectiveness of the resistant members to vary the normal refrigerating temperature of closing the switch by the pressure means and maintaining a substantially constant defrosting temperature.

18. In a refrigerator control, a switch,- a pressure operated bellows-for operating the switch. a resistance device for normally resisting the switch closing movement of the bel1ows,-a second resistance device, means for engaging the second resistance device to further resist the switch closing movement of the bellows, and means for adjusting the said resistance devices to produce the same proportionate change in opposite degree in each of the said resistance devices.

19. In a refrigerator control, a compressor motor, a circuit control means for controlling the circuit of the motor, a pressure means for operating the circuit control means at predetermined points of pressure to maintain normally predetermined refrigerating temperature limits, means for raising the higher temperature limit for defrosting the refrigerator without aiIecting the lower temperature limit, and means for adjusting the pressure means to alter the normal reirigerating temperature limits to other normal refrigerating temperature limits and maintaining the higher defrosting temperature limit substantially constant.

20. 'A refrigerating system comprising in combination, a cooling element normally maintained between desired temperatures limits, means for raising the high normal temperature limit of the cooling element to a defrosting temperature and means for varying the higher normal temperature limit while maintaining the upper limit of the defrosting temperature of the cooling element constant regardless of the variation of the higher normal temperature limit.

21. In a refrigerating apparatus, means for producing a plurality of cycles of operation, means for limiting the operations of the apparatus between normal refrigerating temperature limits, and means for maintaining the apparatus between a defrosting temperature limit and the low normal temperature limit, and means for varying the normal refrigerating temperature limits while maintaining the high defrosting temperature limit constant.

22. In a thermostatic control for controlling refrigerators, means for normally maintaining operating cycles between fixed temperature limits, means for adjusting the temperature limits of said operating cycles, means for producing a higher temperature limit for a defrosting cycle, and means whereby the higher temperature limit of the defrosting cycle remains substantially constant regardless of the adjustment of the normal operating cycle.

23. In a thermostatic control for controlling cyclic operating heat transferring devices, means for adjusting the temperature limits of the normally maintained cycles, means for temporarily changing a temperature limit of the normally maintained operating cycles, and means whereby the temperature to which the said normal temperature limit is changed remains at a substantially fixed value regardless of adjustment of the temperature limits of the normal operating cycles.

24. In a thermostatic control for controlling refrigerators, means for normally maintaining operating cycles between fixed temperature limits, means for varying the temperature limits of said normally operating cycles, means; for modify- 7 normal defrosting cycle; means whereby the upper temperature limit of the defrosting cycle remains at a practically fixed valueregardlessoftheadiustmentofthetemperature limits of the normal operating cycles. and automatic means for restoring the normal operating cycles upon completion of the defrostinl cycle.

25. In a pressure responsive control for controlling cyclic operating preuure producing devices. means for normally maintaining operating cycles between fixed pressure limits. means for adiustingthepressurelimitsofthesaidnormal operating cycles, means for temporarily changing a pressure limit of the normal operating cycles, and means whereby the pressure to which the normalpressurellmitischangedremainsata substantially fixed value resardless of the adjustment of the pressure limits of the normal operating cycles.

26. In a thermostatic control for heat transferring device, means for normally maintaining operating cycles between fixed temperature limits.meansforvaryingthetemperaturelimitsof said normal operating cycles. means for temporarilychangingatemperaturelimitofthenormally maintained operating cycles, means wherebythetemperatm'etowhichthenormaltemperaturelimitischangedremainsatasubstantiallyfixedvalueregardlessofadiustmentofthe normal operating cycles, and means for automatically restoring the said device to the normal operating cycles upon completion of the cycle producedbythechangingofthetemperahirelimit of the normal cycles.

27. In a refrigerator control. a switch. a pressuremeansforoperatingtheswitchtoproduce a normal operating refrigerating temperature between predetermined limits. means for adjustably "wil the normal operating refrigerating temperature limits. means for raising the higher normal temperature limit to a temperature point above the said higher limit and for returning the uppertemperaturelimitfromsaidpointtothe normal operating refrigerating temperature limit andmeansformaintaining thesaid temperature point substantially constant notwithstanding the adfustable variation of the normal operating refrlgerating temperature.

28. A refrigerating system. comprising means for normally producing temperatures between adjustablelimitameansforalteringoneofthetemperature limits to produce a predetermined abnormal temperature limit materially different fromtheonealteredwithout aifectingtbeother ofthesaidnormaltemperaturelimitsandmeans for adlustingthenormalrefrigerating temperas ture limits without altering the predetermined 20. In a refrigerating apparatus, controlling means for limiting-the operation of the apparatustoproduoearefrigeratingtemperaturebetween certain normal temperature limits. means foralterlngoneofthenormaltemperaturelimits to produce a predetermined temperature point materiallyrunotefromthesaidnormaltemperaturelimitsandtoproduceoperationoftheapparatusbetweentheotherofthenormaltempersturelimitsandthesaidpredeterminedtemperaturepoint,meansforsd.iustingthenormalrefrigeratingtemperaturelimits.andmeansformaintainlngthesaid predetermined temperature point substantially constant regardless of the adjustment of the normal refrigerating temperature limits.

80. In a refrigerator control defroster. means for openingan electric circuitatapredetermined 26 temperature below 32 degrees Fahrenheit and meansforclosingthecircuitatapredetermlned temperature above 32 degrees Fahrenheit, and means forvarylngtheopeningtemperaturesbelow 32 degrees Fahrenheit without changing materiallythecircuit closing temperatureabovefl degreesl ahrenheit.

31. In a thermostatic control for controlling cyclic operating heat transferring devices; means for adiustingatemperaturelimitofthenormally maintained operating cycles; means for temporarilychanglngatemperaturelimitofthenormally maintained operating cycle; and means wherebythetemperaturetowhichthesaidnormaltemperaturelimitischangedremainsatsubstantiallyfixedvalueregardlemoftheadlustmentoffirstmeans.

32. Inarefrigeratorcontrolsysteimmeanafor maintaininganormal operating refrigerating cycle between fixed temperature limits; means for 45 adiustingoneofsaidtunperaturelimits; and means operable, when the second mentioned meansisinanyofitsadjustedpositionafortemporarily causing one offthe temperature limits tobechangedtoafixedvslueregardiessofthew positionofthesecondmentionedmeans.

lie-mam.