US2624180A - Automatic defrost actuator - Google Patents

Automatic defrost actuator Download PDF

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Publication number
US2624180A
US2624180A US260290A US26029051A US2624180A US 2624180 A US2624180 A US 2624180A US 260290 A US260290 A US 260290A US 26029051 A US26029051 A US 26029051A US 2624180 A US2624180 A US 2624180A
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Prior art keywords
evaporator
arm
actuator
defrosting
door
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US260290A
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Charles S Grimshaw
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General Electric Co
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General Electric Co
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
    • F25D21/00—Defrosting; Preventing frosting; Removing condensed or defrost water
    • F25D21/02—Detecting the presence of frost or condensate

Definitions

  • the primary object of my invention is to provide in a refrigerator means for controlling a refrigerator defrosting operation in accordance with the formation of frost therein.
  • Another object of my invention is to provide in a refrigerator including an evaporator, an improved arrangement for initiating a refrigerator defrosting operation when frost in excess of a predetermined thickness is formed on'the evaporator.
  • Still another object of my invention is to provide in a refrigerator including an evaporator an improved arrangement eective upon detection of an excessive thickness of frost. on thel evaporator for releasing actuating means to initiate a defrosting operation and effective in response to a predetermined maximum temperature of the evaporator when defrosting thereof is completed for restoring the released actuating means to thereby stop the defrosting operation and return the operation of the refrigerator to normal.
  • a refrigerator including an evaporator, evaporator heating means, a compressor motor and a door.
  • a switch is provided and set for maintaining the circuit of the compressor motor closedl and a circuit controlling the evaporator heating means open.
  • Opening and closing of the refrigerator door causes an arm to be moved, respectively, into and out of an operative position a predetermined distance from the evaporator.
  • -A button yieldably carried by the arm is arranged to be moved to a predetermined' proximity to the evaporator when the arm is operatively positioned and to be moved away from the evaporator when the arm is moved out of the operative position.
  • the button normally restrains an actuator which is mounted slidably on the arm and biased for actuating the switch to open and close the circuits of the compressor motor and evaporator heating means, respectively.
  • the button is displaced relative to the arm whereby the actuator is released to actuate the switch
  • Means responsive to the temperature of the evaporator is effective at a predetermined maximum temperature of the evaporator for restoring the actuator to its restrained state and thereby resetting the switch.
  • FIG. 1 is a sectional view of a refrigerator cabinet provided with the device of my invention
  • Fig. 2 is a plan view of the device of my invention
  • Fig. 3 is a rear and inverted elevational view of the device of my invention
  • Fig. 4 is a sectional view taken along the line 4 4 in Fig. 3
  • Fig. 5 is a plan view of the device illustrating the manner in which the actuator is released
  • Fig. 6 is a wiring diagram of the circuits controlled by the switch.
  • a refrigerator cabinet i including an outer wall 2,-an inner wall or liner 3, an evaporator '4 and a door Evsuitably hinged to the right-side wall of the cabinet.
  • a housing 6 Provided in the right-side wall of the cabinet l and adjacent the rear wall' is a housing 6.
  • the housing 6 is disposed between the outer wall 2 and the inner wall 3 and is suitably secured to the latter.
  • the housing 6 is formed with an open rear side and provided for covering the rear side is a cover plate l.
  • the housing 6 is provided in the left-side wall thereof with an elongated aperture 8. Extending through the aperture 8 is an arm i0 which is formed as a channel with forwardly extending side edges il. At its extreme right-side end the arm ID is pivotally connected to the housing 8 by means of a pin l2 extending between a, portion of the housing and a tab i3 bent inward from the right-side wall thereof.
  • the arm i9 extends from the housing 6 and behind the rear wall' of the evaporator 4'. Carried on the portion of the arm l0 which extends behind the evaporator is a clip I4.
  • the clip Il is adapted to secure to the rear side of the arm Il) one end of a leaf spring I5.
  • the other end of the leaf spring extends beyond the left-side end of the arm I0 and carries a member or button I6.
  • the button i6 is formed with a face Il and a collar i8. As also seen in Figs.
  • the clip I4 assists in retaining an actuator or bar i9 between the forwardly extending edges Il of the arm l0.
  • the actuator i9 is arranged for longitudinal sliding movement along the arm I3 and one end thereof extends into the housing 3 through the aperture 8.
  • the end of the actuator I9 extendingl into the housing 6 is formed with a forwardly extending projection 23.
  • a compression spring 2I resiliently connects the projection 20 on the actuator I3 with a similar projection 22 bent forward from the arm I3. This arrangement is such that the actuator I3 is biased outwardly from the housing 6, or to the left in Figs. 2 and 3.
  • the leaf spring I5 tends to remain in full engagement along its length with the rear side of the arm I3. This causes the button I6 to be so positioned relative to the end of the arm I that the leftward movement of the actuator I3 is restrained by engagement of the left-side'end thereof with the collar I8 formed on the button, in the manner shown in Fig. 2.
  • a compression spring 24 is provided in the spring seat between the arm I3 and the cover plate 'I.
  • the compression spring 24 is stronger than the leaf spring I5, for a purpose which will be seen hereinafter, and is adapted to bias the arm I3 forwardly for engagement with a stop 25 secured to the rear wall of the evaporator 4'.
  • a push rod 21 Cooperating with the front side of the clip 23 and extending through an aperture 23 in the front wall of the housing 6 is a push rod 21.
  • the push rod 21 extends through the side wall of the cabinet I, in the manner shown in Fig. 1, and cooperates at its forward end with the door 5.
  • the spring 24 is compressed by the push rod 21 and the arm I3 is held away from the stop 25, in the position indicated by dot and dash lines in Fig. 2.
  • the arm When the door 5 is closed and the arm I0 is held away from the stop 25, the arm is inoperatively positioned, that is, the face I1 of the button I3 is held away from the evaporator 4 and out of engagement with frost formed thereon.
  • the push rod 21 permits the spring 24 to be effective for causing the arm I0 to engage the stop 25.
  • the arm I3 is operatively positioned a predetermined distance from the rear wall of the evaporator 4. Operative positioning of the arm I0 is effective for moving the face I1 of the button I6 toward a position a predetermined proximity to the rear wall of the evaporator 4.
  • the rear wall of the evaporator 4 is shown as having no frost formed thereon and the face I1 of the button I6 is shown as being positioned a predetermined proximity to the rear wail of the evaporator. 'Ihis predetermined proximity or spacing is indicated by 28 in Fig. 2 and corresponds to a predetermined frost thickness.
  • Fig. 5 indicates frost formed on the rear wall of the evaporator 4 in excess of the predetermined thickness thereof.
  • the face I1 of the button I3 engages the frost and is thereby prevented from being moved to the position of predetermined proximity to they rear wall of the evaporator.
  • the compression spring 24 is stronger than the leaf spring I5. Therefore, the arm I3 continues on to its operative position in which it engages the stop 25. As a result, the leaf spring I5 yields and the button I6 is displaced or moved relative to to the evaporator 4.
  • another switch 33 is provided in addition to the usuall switch 32 included in the circuit of the compressor motor 33 for controlling the operation of the system.
  • switch 33 is also included in a circuit provided for controlling the evaporator heating means 3I.
  • 'I'he switch 33 is contained in the housing 6 and normally is set for maintaining the compressor motor circuit closed and for maintaining the evaporator heating means circuit open.
  • a pendent portion of the projection 23 formed off the inner end of the actuator I3 is adapted to cooperate with and actuate the switch 33 when the actuator I3 is released by the displacement or movement of the button I3 relative to the arm I0.
  • Actuation of the switch 33 initiates a defrosting operation by opening the compressor motor circuit and thereby stopping the compressor motor 33 to stop the refrigeration process and by closing the circuit controlling the evaporator heating means 3I to heat the evaporator.
  • heating means 3I is used to hasten defrosting of the evaporator and that defrosting could be effected, although somewhat more slowly, in an arrangement in which the device of the present invention controls only a compressor motor and in which no heating means is provided.
  • a bellows 34 there is provided in the housing 3 a bellows 34.
  • the bellows 34 is connected by a tube 35, in the manner seen in Fig. 1, with a bulb 36.
  • the bulb 35 contains an amount of v volatile iiuid and is placed in heat exchange relationship with the evaporator 4. Defrosting of the evaporator 4 causes the temperature of the evaporator to increase. This causes the fluid in the bulb 33 to expand whereby the bellows 34 is extended.
  • the actuator I3 is a bar 31 which is pivotally connected as at 33 to the bottom wall of the housing 3. When the bellows 34 is extended. the bar 31 is actuated to the right in Fig. 3.
  • the bar 31 is formed to include a spring seat 33. Situated in the spring seat 33 is a. compression spring 40. Fitted on the other end of the spring 43 is a spring cap 4I. Cooperating with the spring cap 4I and threadedin a stationary nut 42 secured to the 'said member, said member ment 'of said member screw 43 to the evaporator temperature at which the bellows i will be effective thereby stopping the defrosting operation.
  • the lower end of the bar 31 is disposed between a pair of projections 44 bent inward from thefront wall of the housing 6. This arrangement'limits the movements of the bar 31.
  • the temperature of the evaporator 4 is much lower than the defrosting temperature and there is a tendency for the spring 40 to cause the bar 31 to collapse and damage the bellows 34.
  • the temperature of the evaporator 4 might be higher than the defrost temperature. With this condition. thereis a tendency for the bellows to become damaged by overextending.
  • the projections 44 by limiting the movements of the barl 31, are effective for preventing damage to the bellows 34 from either excessive contraction or overextension thereof.
  • a refrigerator including an evaporator, evaporator defrosting meansv and means for controlling said evaporator defrosting means
  • evaporator defrosting means comprising; an arm, means for moving said arm to an operative position a predetermined distance from said evaporator, a member yieldabiy carried by said arm, said member being positioned by said arm a predetermined proximity to said evaporator when said arm is in its operative position, said member being arranged to move relative to said arm when the thickness of frost formed on said evaporator prevents movement of said member to said predetermined proximity to said evaporator, and means operated by movement of said member relative to said arm for initiating operation of said evaporator defrosting means.
  • a refrigerator including an evaporator, evaporator defrosting means and means for controlling said evaporator defrosting means
  • evaporator defrosting means comprising; an arm, means for moving said arm to an operative position a predetermined distance from said evaporator, a member yieldably carried by said arm, said member being positioned by said arm a predetermined proximty to said evaporator when said arm is in its operative position, an actuator mounted on said arm for longitudinal movement relative thereto, said actuator being normally biased against and restrained by being arranged to move relative to said arm when the thickness of frost formed on said evaporator prevents moveto said predetermined proximity to said evaporator, the movement of said member relative to for releasing said actuator, and means operated by the release of said actuator for initiating operationrof said evaporator defrosting means.
  • a refrigerator including an evaporator, evaporator defrosting means and means for controlling said evaporator defrosting means comprising; an arm, means for moving said arm to an operative position -a predetermined distance from said evaporator, a member yieldably carfor restoring the actuator I3 and said arm being eiective ltudinal movement relative ried by said arm.
  • said member being positioned by said arm a predetermined proximity to saidl evaporator when said arm is in its operative position, an actuator mounted on said arm for longithereto, said actuator being normallybiased against and restrained by said member, said member being arranged to move relative to said arm when the thickness of frost formed on said evaporator prevents movement of.
  • a refrigerator including an evaporator, evaporator heating means, a compressor, and circuits controlling said evaporator heating means and said compressor, means for controlling defrosting of said evaporator comprising; switching means normally set for maintaining said evaporator heating means and compressor motor circuits open and closed, respectively, an arm, means for moving said arm to jan operative position a predetermined distance normally engaging said member and being therel by restrained from actuation of said switching means, said member being arranged to move relative to said arm when the thickness of frost formed on said evaporator prevents movement of said member to said predetermined proidmity to said evaporator, the movement of said member relative to said arm being effective for releasing said actuator to thereby actuate said switching means, and means responsive to the temperature of said evaporator and effective at a predetermined temperature thereof for restoring said actuator whereby said switching means is reset and defrosting of said evaporator is stopped.
  • means for controlling said evaporator defrosting means comprising; an arm, means dependent on movement of said door for operatively positioning said arm a predetermined distance from said evaporator, a memberyieldably carried by said arm, said member being positioned by said arm a predetermined proximity to said evaporator when said arm is operatively positioned, said member being arranged to move relative to said arm when thethickness of frost formed on said evaporator prevents movement of said member to said predetermined proximity to ⁇ said evaporator, and means operated by movement of said .member relative to said arm for initiating operation oi said evaporator defrosting means.
  • a refrigerator including an evaporator, evaporator defrosting means and a door
  • means for controlling said evaporator defrosting means said arm being eiective including an evaporator, y
  • a refrigerator including an evaporator, evaporator defrosting means and a door
  • means for controlling said evaporator defrosting means comprising; an arm, a push rod associated with said door, said push rod being actuated by movement of said door to closed position for inoperatively positioning said arm, said push rod being biased to move said arm to an operative position a predetermined distance from said evaporator when said door is opened, a member yieldably carried by said arm.
  • said member being positioned away from said evaporator when said arm is inoperatively positioned, said member being positioned a predetermined proximity to said evaporator when said arm is in its operative position, said member being arranged to move relative to said arm when the thickness of frost formed on said evaporator prevents movement of said member to said predetermined proximity to said evaporator, and means operated by movement of said member relative to said arm for initiating operation of said evaporator defrosting means.
  • a refrigerator including an evaporator, evaporator defrosting means and a. door.
  • means for controlling said evaporator defrosting means comprising; an arm, means dependent on movement of said door for operatively positioning said arm a predetermined distance from said evaporator, a member yieldably carried by said arm, said member being positioned by said arm a predetermined proximity to said evaporator when said arm is operatively positioned, an actuator mounted on said arm for longitudinal movement relative thereto, said actuator being normally biased against and restrained by said member, said member being arranged to move relative to said arm when the thickness of frost formed on said evaporator prevents movement of said member to said predetermined proximity to said evaporator.
  • the movement of said member relative to said arm being effective for releasing said actuator, and means operated by the release of said actuator for initiating operation of said evaporator defrosting means.
  • means for controlling said evaporator defrosting means comprising; an arm, a push rod associated with g said door, means including said push rod for operatively positioning said arm a predetermined distance Irom said evaporator when said door is opened, a member yieldably carried 'by said arm, said member being positioned by said arm a.
  • an actuator mounted on said arm for longitudinal movement relative thereto, said actuator being normally biased against and restrained by said member, said member being arranged to move lfor controlling said evaporator defrosting means .comprising; an arm, a push rod associated with said door, said push rod being actuated by movement of said door to closed position for inoperatively positioning said arm, said push rod being biased to move said arm to an operative position a predetermined distance from said evaporator when said door is opened, a member yieldably carried by said arm, said member being positioned away from said evaporator when said arm is inoperatively positioned.
  • said member being positioned a predetermined proximity to said evaporator when said arm is in its operative position, an actuator mounted on said arm for longitudinal movement relative thereto, said actuator being normally biased against and restrained by said member, said member being arranged to move relative to said arm when the thickness of frost formed on said evaporator prevents movement of said member to said predetermined proximity to said evaporator, the movement of said member relative to said arm being effective for releasing said actuator, and means operated bythe release of said actuator for initiating operation of said evaporator defrosting means.
  • a refrigerator including an evaporator, evaporator defrosting means and a door
  • means for controlling said evaporator defrosting means comprising; an arm, means dependent on movement of said door for operatively positioning said arm a predetermined distance from said evaporator, a member yieldably carried by said arm, said member being positioned by said arm a predetermined proximity to said evaporator when said arm is operatively positioned, an actuator mounted on said arm for longitudinal movement relative thereto, said actuator being normally biased against and restrained by said member, said member being arranged to mo've relative to said arm when the thickness of frost formed on said evaporator prevents movement of said mem- .ber to said predetermined proximity to said evaporator, the movement of said member relative to said arm being effective for releasing said actuator, means operated by the release of said actuator for initiating operation of said evaporator defrosting means, and means responsive to the temperature of said evaporator and effective at a predetermined temperature thereof for restoring said actuator to thereby stop
  • ⁇ evaporator heating means a compressor, circuits.
  • controlling said evaporator heating means and said compressor and a door, means for controlling defrosting of said evaporator comprising; switching means normally set for maintaining said evaporator heating means and compressor motor circuits open and closed, respectively, an arm, a push rod associated with said door, means including said push rod for operatively positioning said arm a predetermined distance from said evaporator when said door is opened, a member yieldably carried by said arm, said member being positioned by said arm a predetermined proximity to said evaporator when said arm is operatively positioned
  • a refrigerator including an evaporator, evaporator heating means, a compressor, circuits controlling said evaporator heating means and said compressor and a door, means for controlling defrosting of said evaporator comprising; switching means normally set for maintaining said evaporator heating means and compressor motor circuits open and closed, respectively, an arm, means dependent upon movement of said door for operatively positioning saidarm a predetermined distance from said evaporator, a
  • said actuator being normally biased for actuating said switching means to close and open said circuits of said evaporator heating means and said compressor motor, respectively, and thereby initiating a defrosting operation, said actuator normally engaging said member and being thereby restrained from actuation of said switching means, said member being arranged to move relative to said arm when the thickness of frost formed on said evaporator prevents movement of said member to said predetermined proximity to said evaporator, the movement of said member relative to said arm being eiective for releasing said actuator ⁇ to thereby actuate said switching means, and means responsive to the temperature of said evaporator and effective at a predetermined temperature thereof for restoring said actuator whereby said switching means is reset and defrosting of said evaporator is stopped.
  • a refrigerator including an evaporator, evaporator heating means, a compressor, circuits controlling said evaporator heating means and said compressor and a door
  • means for controlling defrosting of said evaporator comprising; switching means normally set for maintaining said evaporator heating means and compressor motor circuits open and closed, respectively, an arm, a push rod associated with said door. said ,push rod being actuated by movement of said door to closed position for inoperatively positioning said arm,.
  • said push rod being biased to move said arm to an operative position a predetermined distance from said evaporator, a member yieldably4 carried by said arm, said member being positioned away from said evaporator when said arm is inoperatively positioned, said member being positioneda predetermined proximity to said evaporator when said arm is in its operative position, an actuator mounted on said arm tor longitudinal movement relative thereto, said actuator.
  • an arm a push rod associated with said door, said push rod being actuated byl movement of said door to closed position forinoperatively positioning Asaid arm, a spring biasing said push rod to move said arm to-an operative position a predetermined distance from said evaporator, a stop engageable by said arm for determining said operative position, a button attached to said arm by a spring, said button being positioned away from said evaporator when said arm is inoperatively positioned, said button being positioned by said arm a predetermined proximity to said evaporator corresponding to said predetermined thickness of frost when said arm is in its operative position, an actuator mounted slidably on said arm for longitudinal movement relative thereto, a spring connecting said actuator with said arm and whereby said actuator is normally biased for actuating said switch to close and open said cir:
  • said actuator normally engaging said button and being thereby restrained from actuation of said switch, said button being arranged to move relative to said arm when frost formed on said evaporator in excess of said predetermined thickness prevents movement of said button to said predetermined proximity to said evaporator, the movement of said button relative to said arm being'eiiective for releasing said actuator to thereby actuate said switch.
  • a bellows associated with said actuator said bellows being responsive to the temperature of said evaporator and eiective at a predetermined maximum temperature thereof for restoring said actuator whereby said switch is reset and defrosting of said vevaporator is stopped, and adjusting means associated with said bellows for determining the temperature of said evaporator at which said actuator is restored.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Defrosting Systems (AREA)

Description

Jan- 6, 1953 c. s. GRlMsHAw 2,624,180
AUTOMATIC nEFRos'r AcTuA'roR med Dec. 6. 1951 ze l Inventor:
27, Char-'les S. Grmshaw,
His Attorney;
Patented Jan. 6, 1953 AUTOMATIC DEFROST A CTUATR, Charles S. Grimshaw, Erie, Pa., assignor to General Electric Company York ,1a corporation of New Application December 6, 1951, Serial No. 260,290
17 Claims. (Cl. 62-4) My invention relates to refrigerators and pertains more particularly to automatic defrosting.
means for'refrigerators.
The primary object of my invention is to provide in a refrigerator means for controlling a refrigerator defrosting operation in accordance with the formation of frost therein.
Another object of my invention is to provide in a refrigerator including an evaporator, an improved arrangement for initiating a refrigerator defrosting operation when frost in excess of a predetermined thickness is formed on'the evaporator.
Still another object of my invention is to provide in a refrigerator including an evaporator an improved arrangement eective upon detection of an excessive thickness of frost. on thel evaporator for releasing actuating means to initiate a defrosting operation and effective in response to a predetermined maximum temperature of the evaporator when defrosting thereof is completed for restoring the released actuating means to thereby stop the defrosting operation and return the operation of the refrigerator to normal.
Further. objects and advantages of my invention will become apparent as the following de- Y scription proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.
In carrying out the objects of my invention, I provide a refrigerator including an evaporator, evaporator heating means, a compressor motor and a door. A switch is provided and set for maintaining the circuit of the compressor motor closedl and a circuit controlling the evaporator heating means open.. Opening and closing of the refrigerator door causes an arm to be moved, respectively, into and out of an operative position a predetermined distance from the evaporator. -A button yieldably carried by the arm is arranged to be moved to a predetermined' proximity to the evaporator when the arm is operatively positioned and to be moved away from the evaporator when the arm is moved out of the operative position. The button normally restrains an actuator which is mounted slidably on the arm and biased for actuating the switch to open and close the circuits of the compressor motor and evaporator heating means, respectively.' When during the operative positioning of the arm the thickness of the frost formed on the evaporator prevents themovement of the button to the predetermined proximity thereto,
4 and thereby initiate a defrosting operation.l
, 2 the button is displaced relative to the arm whereby the actuator is released to actuate the switch Means responsive to the temperature of the evaporator is effective at a predetermined maximum temperature of the evaporator for restoring the actuator to its restrained state and thereby resetting the switch.
For a better understanding of my invention, reference may be had tothe accompanying draw ing in which Fig. 1 is a sectional view of a refrigerator cabinet provided with the device of my invention; Fig. 2 is a plan view of the device of my invention; Fig. 3 is a rear and inverted elevational view of the device of my invention; Fig. 4 is a sectional view taken along the line 4 4 in Fig. 3; Fig. 5 is a plan view of the device illustrating the manner in which the actuator is released; and Fig. 6 is a wiring diagram of the circuits controlled by the switch.
Referring to the drawing. I have shown in Fig. 1 a refrigerator cabinet i including an outer wall 2,-an inner wall or liner 3, an evaporator '4 and a door Evsuitably hinged to the right-side wall of the cabinet. Provided in the right-side wall of the cabinet l and adjacent the rear wall' is a housing 6. The housing 6 is disposed between the outer wall 2 and the inner wall 3 and is suitably secured to the latter. -The housing 6 is formed with an open rear side and provided for covering the rear side is a cover plate l.
As better seen in Fig. 2, the housing 6 is provided in the left-side wall thereof with an elongated aperture 8. Extending through the aperture 8 is an arm i0 which is formed as a channel with forwardly extending side edges il. At its extreme right-side end the arm ID is pivotally connected to the housing 8 by means of a pin l2 extending between a, portion of the housing and a tab i3 bent inward from the right-side wall thereof.
The arm i9, as shown in Figs. l and 2, extends from the housing 6 and behind the rear wall' of the evaporator 4'. Carried on the portion of the arm l0 which extends behind the evaporator is a clip I4. The clip Il, as best seen in Figs. 3 and 4, is adapted to secure to the rear side of the arm Il) one end of a leaf spring I5. The other end of the leaf spring extends beyond the left-side end of the arm I0 and carries a member or button I6. The button i6 is formed with a face Il and a collar i8. As also seen in Figs. 2, 3 and 4, the clip I4 assists in retaining an actuator or bar i9 between the forwardly extending edges Il of the arm l0. The actuator i9 is arranged for longitudinal sliding movement along the arm I3 and one end thereof extends into the housing 3 through the aperture 8. The end of the actuator I9 extendingl into the housing 6 is formed with a forwardly extending projection 23. A compression spring 2I resiliently connects the projection 20 on the actuator I3 with a similar projection 22 bent forward from the arm I3. This arrangement is such that the actuator I3 is biased outwardly from the housing 6, or to the left in Figs. 2 and 3. Normally, however, the leaf spring I5 tends to remain in full engagement along its length with the rear side of the arm I3. This causes the button I6 to be so positioned relative to the end of the arm I that the leftward movement of the actuator I3 is restrained by engagement of the left-side'end thereof with the collar I8 formed on the button, in the manner shown in Fig. 2.
Carried on the arm I0 -just inward of the leftside wall of the housing 3 is another clip 23 which is formed on the rear side of the arm I0 to provide a spring seat. Provided in the spring seat between the arm I3 and the cover plate 'I is a compression spring 24. The compression spring 24 is stronger than the leaf spring I5, for a purpose which will be seen hereinafter, and is adapted to bias the arm I3 forwardly for engagement with a stop 25 secured to the rear wall of the evaporator 4'.
Cooperating with the front side of the clip 23 and extending through an aperture 23 in the front wall of the housing 6 is a push rod 21. The push rod 21 extends through the side wall of the cabinet I, in the manner shown in Fig. 1, and cooperates at its forward end with the door 5. When the door is closed, the spring 24 is compressed by the push rod 21 and the arm I3 is held away from the stop 25, in the position indicated by dot and dash lines in Fig. 2.
When the door 5 is closed and the arm I0 is held away from the stop 25, the arm is inoperatively positioned, that is, the face I1 of the button I3 is held away from the evaporator 4 and out of engagement with frost formed thereon.
When the door is opened, the push rod 21 permits the spring 24 to be effective for causing the arm I0 to engage the stop 25. When engaged with the stop 25, in the manner shown in full lines in Fig. 2, the arm I3 is operatively positioned a predetermined distance from the rear wall of the evaporator 4. Operative positioning of the arm I0 is effective for moving the face I1 of the button I6 toward a position a predetermined proximity to the rear wall of the evaporator 4. In Fig. 2 the rear wall of the evaporator 4 is shown as having no frost formed thereon and the face I1 of the button I6 is shown as being positioned a predetermined proximity to the rear wail of the evaporator. 'Ihis predetermined proximity or spacing is indicated by 28 in Fig. 2 and corresponds to a predetermined frost thickness.
In Fig. 5, 23 indicates frost formed on the rear wall of the evaporator 4 in excess of the predetermined thickness thereof. When the door is opened and this condition exists, the face I1 of the button I3 engages the frost and is thereby prevented from being moved to the position of predetermined proximity to they rear wall of the evaporator. However, as pointed out above, the compression spring 24 is stronger than the leaf spring I5. Therefore, the arm I3 continues on to its operative position in which it engages the stop 25. As a result, the leaf spring I5 yields and the button I6 is displaced or moved relative to to the evaporator 4. In addition to the usuall switch 32 included in the circuit of the compressor motor 33 for controlling the operation of the system there is provided another switch 33. The
switch 33 is also included in a circuit provided for controlling the evaporator heating means 3I. 'I'he switch 33 is contained in the housing 6 and normally is set for maintaining the compressor motor circuit closed and for maintaining the evaporator heating means circuit open. A pendent portion of the projection 23 formed off the inner end of the actuator I3 is adapted to cooperate with and actuate the switch 33 when the actuator I3 is released by the displacement or movement of the button I3 relative to the arm I0. Actuation of the switch 33 initiates a defrosting operation by opening the compressor motor circuit and thereby stopping the compressor motor 33 to stop the refrigeration process and by closing the circuit controlling the evaporator heating means 3I to heat the evaporator. It is to be understood that the heating means 3I is used to hasten defrosting of the evaporator and that defrosting could be effected, although somewhat more slowly, in an arrangement in which the device of the present invention controls only a compressor motor and in which no heating means is provided.
As seen in Fig. 3, there is provided in the housing 3 a bellows 34. The bellows 34 is connected by a tube 35, in the manner seen in Fig. 1, with a bulb 36. The bulb 35 contains an amount of v volatile iiuid and is placed in heat exchange relationship with the evaporator 4. Defrosting of the evaporator 4 causes the temperature of the evaporator to increase. This causes the fluid in the bulb 33 to expand whereby the bellows 34 is extended. Commonly cooperating with the bellows 34 and the projection 20 formed 01T the actuator I3 is a bar 31 which is pivotally connected as at 33 to the bottom wall of the housing 3. When the bellows 34 is extended. the bar 31 is actuated to the right in Fig. 3. When the evaporator 4 reaches a predetermined maximum temperature extension of the bellows 34 resultant actuation of the bar 31 is suiiicient for restoring the actuator I3. When the actuator I3 is restored, the leaf spring I5 again positions the button I3 relativeto the arm I3 so that the actuator is restrained by engagement with the collar I3 formed on the button. Also, restoration and restraint of the actuator I3 is effective for resetting the switch 33 whcrebythe motor circuit is closed and the evaporator heating means circuit is opened. Thus, the defrosting operation is stopped and the operation of the refrigerator is returned to normal.
As seen in Fig. 3, the bar 31.is formed to include a spring seat 33. Situated in the spring seat 33 is a. compression spring 40. Fitted on the other end of the spring 43 is a spring cap 4I. Cooperating with the spring cap 4I and threadedin a stationary nut 42 secured to the 'said member, said member ment 'of said member screw 43 to the evaporator temperature at which the bellows i will be effective thereby stopping the defrosting operation.
As best seen in ligs.l 3 and 5, the lower end of the bar 31 is disposed between a pair of projections 44 bent inward from thefront wall of the housing 6. This arrangement'limits the movements of the bar 31. During normal operation of the refrigerator, the temperature of the evaporator 4 is much lower than the defrosting temperature and there is a tendency for the spring 40 to cause the bar 31 to collapse and damage the bellows 34. Also, vduring shipment and transportation of the refrigerator, the temperature of the evaporator 4 might be higher than the defrost temperature. With this condition. thereis a tendency for the bellows to become damaged by overextending. It will be seen that the projections 44, by limiting the movements of the barl 31, are effective for preventing damage to the bellows 34 from either excessive contraction or overextension thereof.
While I have shown and described a speciiic embodiment of my invention, I do not desire my invention to be limited to the particular construction shown and descr'bed and I intend by the appended claims to cover all modifications within the spirit and scope of my invention.
What I claim as new and desire to secure by Letter Patent of the United States is:
1. In a refrigerator including an evaporator, evaporator defrosting meansv and means for controlling said evaporator defrosting means comprising; an arm, means for moving said arm to an operative position a predetermined distance from said evaporator, a member yieldabiy carried by said arm, said member being positioned by said arm a predetermined proximity to said evaporator when said arm is in its operative position, said member being arranged to move relative to said arm when the thickness of frost formed on said evaporator prevents movement of said member to said predetermined proximity to said evaporator, and means operated by movement of said member relative to said arm for initiating operation of said evaporator defrosting means.
2. In a refrigerator including an evaporator, evaporator defrosting means and means for controlling said evaporator defrosting means comprising; an arm, means for moving said arm to an operative position a predetermined distance from said evaporator, a member yieldably carried by said arm, said member being positioned by said arm a predetermined proximty to said evaporator when said arm is in its operative position, an actuator mounted on said arm for longitudinal movement relative thereto, said actuator being normally biased against and restrained by being arranged to move relative to said arm when the thickness of frost formed on said evaporator prevents moveto said predetermined proximity to said evaporator, the movement of said member relative to for releasing said actuator, and means operated by the release of said actuator for initiating operationrof said evaporator defrosting means.
3. In a refrigerator including an evaporator, evaporator defrosting means and means for controlling said evaporator defrosting means comprising; an arm, means for moving said arm to an operative position -a predetermined distance from said evaporator, a member yieldably carfor restoring the actuator I3 and said arm being eiective ltudinal movement relative ried by said arm. said member being positioned by said arm a predetermined proximity to saidl evaporator when said arm is in its operative position, an actuator mounted on said arm for longithereto, said actuator being normallybiased against and restrained by said member, said member being arranged to move relative to said arm when the thickness of frost formed on said evaporator prevents movement of. said member to said predetermined proximity to saidevaporator, the movement of said member relative 'to for releasing said actuator, means operated by the release of said actuator for initiating operation of said evaporator defrosting means, and means responsive to the temperature of said evaporator and effective at a predetermined temperature thereof for restoring said actuator to thereby stop defrosting of said evaporator.
4. In a refrigerator including an evaporator, evaporator heating means, a compressor, and circuits controlling said evaporator heating means and said compressor, means for controlling defrosting of said evaporator comprising; switching means normally set for maintaining said evaporator heating means and compressor motor circuits open and closed, respectively, an arm, means for moving said arm to jan operative position a predetermined distance normally engaging said member and being therel by restrained from actuation of said switching means, said member being arranged to move relative to said arm when the thickness of frost formed on said evaporator prevents movement of said member to said predetermined proidmity to said evaporator, the movement of said member relative to said arm being effective for releasing said actuator to thereby actuate said switching means, and means responsive to the temperature of said evaporator and effective at a predetermined temperature thereof for restoring said actuator whereby said switching means is reset and defrosting of said evaporator is stopped.
5. In a refrigerator evaporator defrosting means and a door, means for controlling said evaporator defrosting means comprising; an arm, means dependent on movement of said door for operatively positioning said arm a predetermined distance from said evaporator, a memberyieldably carried by said arm, said member being positioned by said arm a predetermined proximity to said evaporator when said arm is operatively positioned, said member being arranged to move relative to said arm when thethickness of frost formed on said evaporator prevents movement of said member to said predetermined proximity to `said evaporator, and means operated by movement of said .member relative to said arm for initiating operation oi said evaporator defrosting means.
' 6. In a refrigerator including an evaporator, evaporator defrosting means and a door, means for controlling said evaporator defrosting means said arm being eiective including an evaporator, y
comprising; an arm, a push rod associated with said door, meansvincluding said push rod for operatively positioning said arm a predetermined distance from said evaporator when said door is opened, a member yieldably carried by said arm, said member being positioned by said arm a predetermined proximity to said evaporator when said arm is operatively positioned, said member being arranged to move relative to said arm when the thickness of frost formed on said evaporator prevents movement of said member to said predetermined proximity to said evaporator, and means operated by movement of said member relative to said arm for initiating operation o1' said evaporator defrosting means.
'7. In a refrigerator including an evaporator, evaporator defrosting means and a door, means for controlling said evaporator defrosting means comprising; an arm, a push rod associated with said door, said push rod being actuated by movement of said door to closed position for inoperatively positioning said arm, said push rod being biased to move said arm to an operative position a predetermined distance from said evaporator when said door is opened, a member yieldably carried by said arm. said member being positioned away from said evaporator when said arm is inoperatively positioned, said member being positioned a predetermined proximity to said evaporator when said arm is in its operative position, said member being arranged to move relative to said arm when the thickness of frost formed on said evaporator prevents movement of said member to said predetermined proximity to said evaporator, and means operated by movement of said member relative to said arm for initiating operation of said evaporator defrosting means.
8. In a refrigerator including an evaporator, evaporator defrosting means and a. door. means for controlling said evaporator defrosting means comprising; an arm, means dependent on movement of said door for operatively positioning said arm a predetermined distance from said evaporator, a member yieldably carried by said arm, said member being positioned by said arm a predetermined proximity to said evaporator when said arm is operatively positioned, an actuator mounted on said arm for longitudinal movement relative thereto, said actuator being normally biased against and restrained by said member, said member being arranged to move relative to said arm when the thickness of frost formed on said evaporator prevents movement of said member to said predetermined proximity to said evaporator. the movement of said member relative to said arm being effective for releasing said actuator, and means operated by the release of said actuator for initiating operation of said evaporator defrosting means.
9. In a refrigerator including an evaporator, evaporator defrosting means and a door, means for controlling said evaporator defrosting means comprising; an arm, a push rod associated with g said door, means including said push rod for operatively positioning said arm a predetermined distance Irom said evaporator when said door is opened, a member yieldably carried 'by said arm, said member being positioned by said arm a. predetermined proximity to said evaporator when said arm is operatively positioned, an actuator mounted on said arm for longitudinal movement relative thereto, said actuator being normally biased against and restrained by said member, said member being arranged to move lfor controlling said evaporator defrosting means .comprising; an arm, a push rod associated with said door, said push rod being actuated by movement of said door to closed position for inoperatively positioning said arm, said push rod being biased to move said arm to an operative position a predetermined distance from said evaporator when said door is opened, a member yieldably carried by said arm, said member being positioned away from said evaporator when said arm is inoperatively positioned. said member being positioned a predetermined proximity to said evaporator when said arm is in its operative position, an actuator mounted on said arm for longitudinal movement relative thereto, said actuator being normally biased against and restrained by said member, said member being arranged to move relative to said arm when the thickness of frost formed on said evaporator prevents movement of said member to said predetermined proximity to said evaporator, the movement of said member relative to said arm being effective for releasing said actuator, and means operated bythe release of said actuator for initiating operation of said evaporator defrosting means.
l1. In a refrigerator including an evaporator, evaporator defrosting means and a door, means for controlling said evaporator defrosting means comprising; an arm, means dependent on movement of said door for operatively positioning said arm a predetermined distance from said evaporator, a member yieldably carried by said arm, said member being positioned by said arm a predetermined proximity to said evaporator when said arm is operatively positioned, an actuator mounted on said arm for longitudinal movement relative thereto, said actuator being normally biased against and restrained by said member, said member being arranged to mo've relative to said arm when the thickness of frost formed on said evaporator prevents movement of said mem- .ber to said predetermined proximity to said evaporator, the movement of said member relative to said arm being effective for releasing said actuator, means operated by the release of said actuator for initiating operation of said evaporator defrosting means, and means responsive to the temperature of said evaporator and effective at a predetermined temperature thereof for restoring said actuator to thereby stop defrosting of said evaporator.
12. In a refrigerator including an evaporator, evaporator defrosting means and a door, means for controlling said evaporator defrosting means comprising; an arm, a push rod associated with said door, means including said push rod for operatively positioning said arm a predetermined distance from said evaporator when said door is opened, a member yieldably carried by said arm, said member being positioned by said arm a predetermined proximity to said evaporator when said arm is operatively positioned, an actuator mounted on said arm for longitudinal movement relative thereto,Y said actuator being normally biased against and restrained by said member, said member being arranged to move relative to -said arm when the thickness oi.' -frost formed on for controlling said evaporator defrosting means comprising; an arm, a push rod associated with said door, said push rod being actuated by movement of said door to closed position for inop- -eratively positioning said arm, said push rod being biased to move said arm-to an operative position a predetermined distance from said for releasing said actuator to thereby actuate said switching means, and means responsive to the temperature of said evaporator and Aeiective at a predetermined temperature thereof for restoring said actuator whereby said switching means 1 is reset and defrosting of said evaporator is 'evaporator defrosting means and a door, means stopped.
15. In a refrigerator including an evaporator,
` evaporator heating means, a compressor, circuits.
controlling said evaporator heating means and said compressor and a door, means for controlling defrosting of said evaporator comprising; switching means normally set for maintaining said evaporator heating means and compressor motor circuits open and closed, respectively, an arm, a push rod associated with said door, means including said push rod for operatively positioning said arm a predetermined distance from said evaporator when said door is opened, a member yieldably carried by said arm, said member being positioned by said arm a predetermined proximity to said evaporator when said arm is operatively positioned| an actuator mounted on said evaporator when said door is opened, a members yieldably carried by said arm, said member being positioned away from said evaporator when said arm is inoperatively positioned, said member being positioned a predetermined proximity to said evaporator when said arm is in its operative position, an actuator mounted on said arm for longitudinal movement relative thereto, said actuator being normally biased against and restrained by said member, said member being arranged to move relative to said arm whenl the thickness oi frost formed on said evaporator prevents movement of said member to said predetermined proximity to said evaporatorl the movement of said member relative to said arm being eiective for releasing said actuator, means operated by the release of said actuator for initiating operation of said evaporator defrosting means, and means responsive to the temperature of said evaporator and eective at a predetermined temperature thereof for restoring said actuator to thereby stop defrosting of said evaporator.
14.1In a refrigerator including an evaporator, evaporator heating means, a compressor, circuits controlling said evaporator heating means and said compressor and a door, means for controlling defrosting of said evaporator comprising; switching means normally set for maintaining said evaporator heating means and compressor motor circuits open and closed, respectively, an arm, means dependent upon movement of said door for operatively positioning saidarm a predetermined distance from said evaporator, a
member yieldably carried by said arm, said member being positioned by said arm a predetermined proximity to said evaporator when said arm is operatively positioned, an actuator mounted on said arm for longitudinal movement relative thereto, said actuator being normally biased for actuating said switching means to close and open said circuits of said evaporator heating means and said compressor motor, respectively, and thereby initiating av defrosting operation, said actuator normally engaging said member and being thereby restrained from actuation of said switching means, said member being arranged4 to move relative to said arm when the thickness of frost formed on said evaporator prevents movement of said member to said predetermined proximity to said evaporator, the movement of said member relative yto said arm being effective arm for longitudinal movement relative theretof.
said actuator being normally biased for actuating said switching means to close and open said circuits of said evaporator heating means and said compressor motor, respectively, and thereby initiating a defrosting operation, said actuator normally engaging said member and being thereby restrained from actuation of said switching means, said member being arranged to move relative to said arm when the thickness of frost formed on said evaporator prevents movement of said member to said predetermined proximity to said evaporator, the movement of said member relative to said arm being eiective for releasing said actuator` to thereby actuate said switching means, and means responsive to the temperature of said evaporator and effective at a predetermined temperature thereof for restoring said actuator whereby said switching means is reset and defrosting of said evaporator is stopped.
16. In a refrigerator including an evaporator, evaporator heating means, a compressor, circuits controlling said evaporator heating means and said compressor and a door, means for controlling defrosting of said evaporator comprising; switching means normally set for maintaining said evaporator heating means and compressor motor circuits open and closed, respectively, an arm, a push rod associated with said door. said ,push rod being actuated by movement of said door to closed position for inoperatively positioning said arm,. said push rod being biased to move said arm to an operative position a predetermined distance from said evaporator, a member yieldably4 carried by said arm, said member being positioned away from said evaporator when said arm is inoperatively positioned, said member being positioneda predetermined proximity to said evaporator when said arm is in its operative position, an actuator mounted on said arm tor longitudinal movement relative thereto, said actuator. being normally biased for actuating said switching means to close and open said circuits of said evaporator heating means and said compressor motor, respectively, and thereby initiating a defrosting operation, said actuator normally engaging said member and being thereby restrained from actuation of said switching means, said member being arranged to move relative to said arm when the thickness of rost evaporator heating means, a' compressor. circuits controlling said evaporator heating means and said compressor and a door. means for defrosting said evaporator when frost forms thereon in excess of a predetermined thickness comprising; la switch normally set for maintaining said evaporator heating means and compressor motor circuits open and closed. respectively, an arm, a push rod associated with said door, said push rod being actuated byl movement of said door to closed position forinoperatively positioning Asaid arm, a spring biasing said push rod to move said arm to-an operative position a predetermined distance from said evaporator, a stop engageable by said arm for determining said operative position, a button attached to said arm by a spring, said button being positioned away from said evaporator when said arm is inoperatively positioned, said button being positioned by said arm a predetermined proximity to said evaporator corresponding to said predetermined thickness of frost when said arm is in its operative position, an actuator mounted slidably on said arm for longitudinal movement relative thereto, a spring connecting said actuator with said arm and whereby said actuator is normally biased for actuating said switch to close and open said cir:
cuits of said evaporator heating means and said compressor motor,y respectively, and thereby initiating a `dei'rcsting operation. said actuator normally engaging said button and being thereby restrained from actuation of said switch, said button being arranged to move relative to said arm when frost formed on said evaporator in excess of said predetermined thickness prevents movement of said button to said predetermined proximity to said evaporator, the movement of said button relative to said arm being'eiiective for releasing said actuator to thereby actuate said switch. a bellows associated with said actuator, said bellows being responsive to the temperature of said evaporator and eiective at a predetermined maximum temperature thereof for restoring said actuator whereby said switch is reset and defrosting of said vevaporator is stopped, and adjusting means associated with said bellows for determining the temperature of said evaporator at which said actuator is restored. j
CHARLES S. GRIMSHAW.
REFERENCES CITED The following references are of record in the le of this patent:
UNITED STATES PATENTS
US260290A 1951-12-06 1951-12-06 Automatic defrost actuator Expired - Lifetime US2624180A (en)

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Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2704441A (en) * 1953-03-11 1955-03-22 Admiral Corp Automatic defrosting system
US2711079A (en) * 1952-11-18 1955-06-21 Gen Electric Automatic refrigerator control
US2741097A (en) * 1952-11-29 1956-04-10 Gen Electric Automatic refrigerator control
US2767555A (en) * 1953-07-16 1956-10-23 Whirlpool Seeger Corp Frost bank automatic defrost actuator
US2780442A (en) * 1952-06-24 1957-02-05 Gen Motors Corp Refrigerating apparatus
US2867092A (en) * 1954-08-26 1959-01-06 Hupp Corp Automatic defrost control
US3033004A (en) * 1960-01-08 1962-05-08 Controls Co Of America Defrost control responsive to frost accumulation
US3256707A (en) * 1965-07-30 1966-06-21 Robert H Thorner Control defrost device for refrigeration apparatus
US3321928A (en) * 1964-02-03 1967-05-30 Robert H Thorner Defrosting control for a refrigeration device
US3399541A (en) * 1966-04-25 1968-09-03 Robert H. Thorner Defroster control
US3465535A (en) * 1968-05-01 1969-09-09 Gen Electric Frost detector for refrigerant evaporators

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US1916315A (en) * 1929-07-03 1933-07-04 Emory L Groff Means for automatically defrosting refrigerating units
US1999191A (en) * 1930-09-20 1935-04-30 Marcus A Hirschl Defrosting
US2007409A (en) * 1932-10-28 1935-07-09 John J Schweitzer Defrosting indicator for mechanical refrigerators
US2114768A (en) * 1932-12-08 1938-04-19 Nash Kelvinator Corp Refrigerating apparatus
US2123073A (en) * 1932-04-30 1938-07-05 Edythe H Bell Means for automatic defrosting of refrigerating systems
US2147867A (en) * 1934-07-23 1939-02-21 Servel Inc Automatic defrosting refrigerator apparatus
US2421819A (en) * 1942-06-10 1947-06-10 Int Harvester Co Device for regulating the thickness of ice formations on evaporator coils

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1916315A (en) * 1929-07-03 1933-07-04 Emory L Groff Means for automatically defrosting refrigerating units
US1999191A (en) * 1930-09-20 1935-04-30 Marcus A Hirschl Defrosting
US2123073A (en) * 1932-04-30 1938-07-05 Edythe H Bell Means for automatic defrosting of refrigerating systems
US2007409A (en) * 1932-10-28 1935-07-09 John J Schweitzer Defrosting indicator for mechanical refrigerators
US2114768A (en) * 1932-12-08 1938-04-19 Nash Kelvinator Corp Refrigerating apparatus
US2147867A (en) * 1934-07-23 1939-02-21 Servel Inc Automatic defrosting refrigerator apparatus
US2421819A (en) * 1942-06-10 1947-06-10 Int Harvester Co Device for regulating the thickness of ice formations on evaporator coils

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2780442A (en) * 1952-06-24 1957-02-05 Gen Motors Corp Refrigerating apparatus
US2711079A (en) * 1952-11-18 1955-06-21 Gen Electric Automatic refrigerator control
US2741097A (en) * 1952-11-29 1956-04-10 Gen Electric Automatic refrigerator control
US2704441A (en) * 1953-03-11 1955-03-22 Admiral Corp Automatic defrosting system
US2767555A (en) * 1953-07-16 1956-10-23 Whirlpool Seeger Corp Frost bank automatic defrost actuator
US2867092A (en) * 1954-08-26 1959-01-06 Hupp Corp Automatic defrost control
US3033004A (en) * 1960-01-08 1962-05-08 Controls Co Of America Defrost control responsive to frost accumulation
US3321928A (en) * 1964-02-03 1967-05-30 Robert H Thorner Defrosting control for a refrigeration device
US3256707A (en) * 1965-07-30 1966-06-21 Robert H Thorner Control defrost device for refrigeration apparatus
US3399541A (en) * 1966-04-25 1968-09-03 Robert H. Thorner Defroster control
US3465535A (en) * 1968-05-01 1969-09-09 Gen Electric Frost detector for refrigerant evaporators

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