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Publication numberUS3055188 A
Publication typeGrant
Publication dateSep 25, 1962
Filing dateJan 16, 1961
Priority dateJan 16, 1961
Publication numberUS 3055188 A, US 3055188A, US-A-3055188, US3055188 A, US3055188A
InventorsThomas I Syfert
Original AssigneeRanco Inc
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Refrigeration defrost device
US 3055188 A
Abstract  available in
Previous page
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Claims  available in
Description  (OCR text may contain errors)

P 1962 T. I. SYFERT 3,055,188

REFRIGERATION DEFROST DEVICE Filed Jan. 16, 1961 4INVENTOR THOMAS I. SYFERT ATTORNEY l I 1 t tea This invention relates to refrigerator control apparatus for effecting periodic defrosting of mechanical refrigerators, and more particularly to an improved control apparatus of the type which initiates a defrosting operation whenever a door of the refrigerator has been opened and closed a predetermined number of times.

The rate of accumulation of frost on the freezing unit of a refrigerator is generally dependent upon the number of times the door is opened and also upon the degree of humidity in the air which enters the refrigerator cabinet when the door is opened. Controls have been devised which initiate the defrosting operation after a predetermined number of door openings or closings; however, due to the differences in humidity generally prevailing throughout the different parts of the country, the number of door openings and closings required to maintain relatively frost-free freezing units of refrigerators in different sections of the country will vary. Accordingly, it is a principal object of this invention to provide a refrigerator control apparatus for initiating a defrosting operation or cycle after a predetermined number of door openings, and which predetermined number may be readily varied in accordance with the prevailing requirements.

It is a more specific object of this invention to provide a control apparatus of the above mentioned character having an electric switch for controlling a defrosting cycle and which is operated after a predetermined number of door openings by counting means driven by the reciprocation of an actuating member which is engaged and moved through a drive stroke by the door upon each closing thereof, and wherein the predetermined number of openings can be changed by the provision of a removable extension means on the actuating member to change the length of the drive stroke thereof.

Other objects and advantages of this invention will be apparent from the following detailed description of a presently preferred embodiment thereof and from the accompanying sheet of drawings forming a part of this specification, and in which FIG. 1 shows a top elevational view of a control apparatus embodying this invention with the cover plate removed;

FIG. 2 is a view similar to FIG. 1 but showing the parts thereof in different positions;

FIG. 3 is a view similar to FIGS. 1 and 2 but showing the parts in still different position, and including an extension means on the actuating member thereof;

FIG. 4 is a sectional view of the apparatus of FIG. 1 taken substantially along line 44 thereof;

FIG. 5 is a fragmentary sectional view taken along line 55 of FIG. 4;

FIG. 6 is a fragmentary view of the device of FIG. 1 showing a modification thereof; and 7 FIG. 7 is a fragmentary view illustrating another modification.

In the form of the control apparatus illustrated, there is provided a housing 10 in the form of a generally recice tangular box, preferably of a suitable molder insulating material and having an open side normally closed by a cover plate 11. Electric switch means are mounted in the housing for initiating and terminating defrosting cycles in the freezing unit of a refrigerator by controlling the completion of a circuit for a defrosting system which may be of any well known type such as one in which a solenoid operated valve directs hot gas into the freezing unit.

Although the defrosting switch means may be of any suitable construction, it is preferably of the over center type of snap acting switch, and it is herein illustrated as comprising a fiat spring switch arm 12 having an electrical contact 12a at one end thereof and being secured to the rear wall 10a of the housing 10 by a screw 14 at the other end thereof. The screw 14 also serves to secure one end of a conductor 15 which leads from arm 12 to a screw 16 which secures to wall 10a a terminal lug (not shown) for connection of the switch into the defrosting circuit. A stationary contact member 20, having a contact 2021 in registration with contact 12a, is secured to housing wall 10a by a screw 2012 which may also secure a terminal lug 20c thereto. Switch arm 12 is movable to bring contact 12a into and out of engagement with contact 20a to make and break an electrical circuit therethrough in a manner which will be made apparent as the description proceeds.

A tongue member 12b is struck out of the central portion of arm 12 and has its free or movable end in engagement with one end of a C-shaped spring 18, the other end of which engages the switch arm 12 adjacent the contact 12a thereof, as shown, and normally biases contact 12a against a stop 21 formed on the housing wall 10a.

A plunger 24, having one end disposed adjacent tongue member 1212, is reciprocably carried in a bearing 25 which is preferably formed as a part of the housing 10. Plunger 24 is adapted to be driven by means more fully described hereinafter, against the tongue member 12b to move the latter through its dead center position, in alignment with contact arm 12, to a position on the other side thereof so that C-shaped spring 18 biases contact arm 12 in a direction away from housing wall ltla and brings contact 12a into maintained engagement with contact 20a.

The means for moving plunger 24 against the tongue 12b is in the nature of a ratchet type counting means responsive to a predetermined number of door openings and closings, and comprises as one part thereof a U-shaped spring member 26 which has one leg 26a thereof secured to housing 10 by a screw 27, and has another leg 26b in overlying relation to an exposed end of plunger/24. An opening 26c is conveniently provided in leg 26b of spring 26 to provide access to the securing screw 27. A ratchet wheel 28, forming another part of the counting means, is rotatably mounted on a reduced portion 25a of bearing 25 surrounding the exposed end of plunger 24, and is conveniently retained thereon by a circular end portion 26d of spring 26. A semi-circular cam member 30 is secured to the ratchet wheel 28 forrotation therewith and presents an inclined cam surface 30a which is adapted to engage the leg 26b of spring 26 and to move the latter away from the end of plunger 24 upon rotation of the ratchet wheel. Continued rotation of ratchet wheel 28 will permit the leg 26b to drop off the end 3% of cam 30, allowing it to spring back toward the plunger 24. The inertia of the leg 2611 will carry it past its normal resting position, shown in FIG. 4, causing it to drive plunger 24 sharply against tongue 12b, moving the latter through its dead center position and bringing contact 12a into engagement with contact 2011 in the manner described previously, and thereby completing an electrical circuit for initiating the heating phase of the defrosting cycle.

Rotation of ratchet Wheel 28 is effected in a step-bystep or incremental manner, upon repeated openings of a refrigerator door, by ratchet means including a flexible dog member 32 which is preferably formed of fiat spring stock and includes a ratchet wheel engaging end 32a and a. cam follower portion 32b. A ratchet pawl 33 having a ratchet wheel engaging end 33a is preferably formed integrally with dog member 32 and the two are secured to the housing by a common eye 33!) received in a cylindrical opening 34 formed in the housing.

An elongated actuating member 36, for moving dog member 32, extends through an opening 37 in one Wall of housing 10 and is reciprocably disposed therein. The inner end of actuator 36 is provided with a cam surface having a plurality of steps 36a, 36b and 360 upon which the cam follower portion 32b of dog 32 is adapted to ride and the purposes of which will become apparent as the description proceeds. The outer end 36d of the actuator member is adapted to be engaged by a refrigerator door, a fragment of which is indicated at 38, for effecting inward movement thereof through a drive stroke. The actuating member 36 is normally biased outwardly to the position illustrated in FIG. 1 by a wire spring 39 which acts against the inner end of the actuating member and is coiled about a post 40* formed in the housing 10, and has a portion 39a bearing against a side wall of the housing.

It will be recognized that upon closing of the refrigerator door 38, the actuating member 36 will be engaged thereby and will be moved inwardly a distance A to the position shown in FIG. 2. It will also be recognized that uponv such movement cam follower portion 32b of ratchet dog 32 will be moved to the left, coming to rest on the step or cam surface 36b, and that the tooth engaging portion 32a will elfect rotation of ratchet wheel 28 in a counter-clockwise direction, as viewed in FIG. 2 a distance of one tooth. Upon a subsequent opening of door. 38, actuator member 36 will be moved outwardly through a return stroke by spring 39 and ratchet dog 32 will move to the right with the end 32a thereof riding over one tooth, and with the cam follower portion 32b thereof coming to rest on the surface 36a. During the return movement of the ratchet dog 32, ratched wheel 28 is held against movement in a clockwise direction by the ratchet pawl 33. A number of door openings and closings corresponding to the number of teeth 28a of ratchet wheel 28 will result in one complete revolution of the ratchet wheel, and will cause the spring 26 to strike plunger 24 and actuate the defrosting switch means, closing contacts 12a, 20a thereof to initiate the defrosting cycle.

In some instances it is desirable to have a defrost cycle initiated upon one half a revolution of ratchet wheel 28, in which case a second semi-circular cam member 30 is provided on the ratchet wheel, as shown in FIG. 6. The second cam member 30' serves to operate the defrost switch in the same manner as cam member 30, thereby decreasing the number of door closings required to initiate a defrosting operation.

Means are provided to operate the defrosting switch means to open contacts 12a, Ztla to terminate the defrost ing cycle and return the refrigerator to normal operation when the freezing unit has been heated sufliciently to effect the defrosting. To this end a thermally responsive bellows means, generally indicated at 42, is mounted in a recess 10b defined by Wall portions 10c extending from the housing rear wall 10a, and comprises a flexible metal bellows member 43 secured to a base plate 44 which is suitably fastened to, wall portions 10c as by screws 44a. 7 Bellows 43 is provided with a central post or plunger 45 which is threaded at its outer end and has an insulator member 46 threadedly engaged thereon. Insulator member 46 extends through an opening 10d in housing wall 10a and is adapted to engage tongue 1221 when the latter has been moved by plunger 24. Base plate 44 includes an inwardly extending member 44b having a lug 44c thereon. A lever 47 has an opening 47a which received lug 44c and is thereby pivotally connected to member 44b. Lever 47 extends across the face of bellows 43 and has a central opening 47d through which plunger 45 extends. A compression spring 48 surrounds plunger 45 and is disposed between lever 47 and a flange 46a of insulator member 46. An adjusting screw 49 extends through a threaded opening in end 470 of lever 47 and bears against plate 44 with the end of the screw received in an indentation in the plate. Screw 49 can be advanced or retracted to move lever 47 and vary the tension of spring 48 which loads or biases the bellows in a direction tending to expand the same.

A tubular element 50, which is sealed at one end, is connected at its other end by brazing or soldering to plate 44, and is in communication with the interior of bellows 43. Both the tubular element 50 and the bellows 43 contain a fluid at a pressure less than atmospheric, which fluid expands and contracts with increases and decreases in temperature. The tubular element is preferably placed in a position adjacent the freezing unit of the refrigerator so that when the temperature of the unit rises to a predetermined degree, the bellows will be expanded by spring 48 forcing plunger insulator 46 against tongue 12b and moving the latter through its center position for actuating the defrosting switch means to return the refrigerator to normal operation. The predetermined temperature at which the defrosting operation is terminated may be adjusted or varied by means of load adjusting screw 49. The latter may be conveniently adjusted from the front of the device through an opening in cover 11 which is aligned with a tunnel 10c formed in housing 10 and leading to screw 49. Preferably, a nylon washer 49a surrounds screw 49 to hold the screw in its adjusted position.

After the refrigerator is returned to normal operation and as the freezing unit then cools, the fluid in tubular member 50 and bellows 43 contracts permitting the bellows to be compressed by atmospheric air pressure to withdraw plunger 45, thereby placing the apparatus in condition for initiating another defrosting cycle after the completion of the predetermined number of door openings required to turn ratchet wheel 28 through one revolution.

The construction of the bellows means 42 provides a fail-safe feature in that if a leak occurs in the tubular element or bellows, the sub-atmospheric condition therein will be destroyed and the plunger will move to the right as viewed in FIG. 4, under the influence of spring 48, thereby actuating the defrosting switch to return the refrigerator to normal operation or, to prevent a defrost cycle from being initiated. Thus, if such a leak occurs during a defrosting operation, there will be no danger of the defrosting means causing the temperature within the refrigerator to rise beyond the predetermined temperature and spoil the food or damage the refrigerator.

The invention provides means for readily changing the number of door closings required to initiate the defrost cycle so that when refrigerators equipped with the defrosting control of this invention are to be used in a section of the country having a high degree of humidity, where frost builds up on the freezing unit more rapidly, they can be simply and rapidly adjusted or modified to initiate the defrosting operation more frequently than those in less humid sections. T 0 this end, and as illustrated in FIG. 3, an actuating member extension means in the form of a removable rubber or plastic cap 56 is provided on the end of the actuating member and serves to extend the length thereof. The cap or extension memher 56 is conveniently retained on the actuating member 36 by engagement of a reduced neck portion 56a with a groove 36e formed in the actuating member adjacent the end thereof. With the cap 56 in place, it will be seen that upon each closing of door 38, actuating member 36 will be moved through a distance indicated at B in FIG. 3. The distance B, which is greater than distance A, represents a lengthened drive stroke of the member 36. With each such lengthened drive stroke the dog 32 will be moved to the left by the cam surface on actuating member 36 until cam follower 32b rests on step 36c, thereby effecting rotation of the ratchet wheel 28 through an angular distance corresponding to two teeth rather than one tooth as in the previously described operation. It will be recognized that with such longer drive strokes as are effected with cap 56 in place, and with the resultant increased rotation of ratchet wheel 28, contacts 12a, 20a will be closed and a defrosting operation will be initiated upon one-half the number of door closings required to initiate the operation when cap 56 is not used.

As an alternative to the use of a cap 56 to extend the drive stroke of member 36, a striker plate or button 57 may be installed on the door 38 as shown in FIG. 7. It will be understood that the striker plate or button 57 will extend above the normal surface of the door 38 and is adapted to engage and move the actuating member 36 so as to provide an increased rotation of ratchet wheel 28 and a consequent decrease in the number of door openings and closings required to initiate defrosting of the refrigerator.

Although the apparatus has been described as moving the ratchet wheel one tooth for each normal drive stroke of actuator member 36, and two teeth for each lengthened drive stroke thereof, it will be understood that different sizes of steps 36b and 360 can be used as well as different sizes of teeth 28a to vary the number of strokes required to operate the switch means. Also, although the device has been described as including only contacts 12a and 20a, which comprise a single pole, single throw switch means, it will be understood that additional contact means could be included in the place of stop member 21 to provide a single pole, double throw switch means.

From the foregoing detailed description of a refrigerator control apparatus embodying this invention, and from the accompanying sheet of drawings, it will be recognized that there has been provided by this invention an improved control apparatus whereby refrigerator defrosting operations can be initiated in accordance with difierent predetermined numbers of door openings as re quired by different frosting conditions and that the invention accomplishes this in a particularly simple, reliable and effective manner.

Although the invention has been described herein with reference to a specific embodiment of control apparatus, it is understood that the invention is not limited thereto but, rather, the invention includes all such adaptations, changes and modifications as are reasonably embraced by the scope of claims hereof.

Having described my invention, I claim:

1. A defrosting control apparatus for use in initiating a defrosting operation in a defrosting means of a refrigerator freezing unit in response to a predetermined number of openings and closings of the refrigerator door, said apparatus comprising:

(a) a housing,

(b) switch means mounted on said housing and having first and second operative positions for initiating and terminating defrosting cycles,

(0) a ratchet wheel rotatably mounted in said housing,

(d) means between said ratchet wheel and switch to effect operation of the latter to said lfirst position upon predetermined rotation of said ratchet wheel,

(e) an actuator member reciprocable in said housing and presenting first and second cam surfaces,

(1) dog means movable by said first cam surface and operative to rotate said ratchet wheel through an increment of said predetermined rotation upon reciprocation of said actuator member through a stroke of a first length,

(g) said dog means being movable by said first and second cam surfaces and operative to rotate said ratchet wheel through a greater increment of said predetermined rotation upon reciprocation of said actuator through a stroke of a second and greater length,


(h) whereby said predetermined rotation of said ratchet wheel is effected by one number of strokes of said first length and by a lesser number of strokes of said second length.

2. Control apparatus as defined in claim 1 and wherein said actuator member is adapted to be reciprocated by engagement by a refrigerator door, and said actuator member comprises an extension means removably to vary the length of said strokes.

Wood Oct. 23, 1956 Newberry Apr. 16, 1957

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2767555 *Jul 16, 1953Oct 23, 1956Whirlpool Seeger CorpFrost bank automatic defrost actuator
US2788640 *Dec 23, 1954Apr 16, 1957Westinghouse Electric CorpControl for refrigeration apparatus
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3223798 *Apr 18, 1963Dec 14, 1965Gen Motors CorpVariable timer switch
US3899895 *Oct 15, 1974Aug 19, 1975Texas Instruments IncAutomatic defrosting control system
US4463348 *Nov 23, 1981Jul 31, 1984General Electric CompanyRefrigerator door usage monitor and display system
U.S. Classification62/267, 62/153, 62/234
International ClassificationF25D21/00
Cooperative ClassificationF25D21/004, F25D2700/02
European ClassificationF25D21/00A1