US2674665A - Clock initiated defroster control for mechanical refrigerators - Google Patents

Description

Aplll 5, 1954 E. c. RANEY ETAL 2,674,665

cLocx INITIATED DEFRosTER CONTROL FOR MECHANICAL REFRIGERATORS Filed June 14, 1951 2 sheets-sheet 1 Ze-STEL C PAA/Y MX Y 7 ,4 T TOR/Vf Ys RANEY ET AL CLOCK INITIATED DEFROSTER CONTROL April 6, 1954 FOR MECHANICAL REFRIGERATORS 2 Sheets-Shes*l 2 Filed June 14, 1951 'IIlIIIIII/IIIIIIIIIIII IIIIIIIIIIIIL "IIIIIIIIIIIIIIIIIIIIIIIlIIHIIII n H u INVENTORS [J7-L C' PA/wsy BYJo/f/v L /E RMA/vw o, ATmR/vf Y@ Patented Apr. 6, 1954 CLOCK INITIATED DEFROSTER CONTROL FOR MECHANICAL REFRIGERATORS Estel C. Raney, Delaware, and John Liebermann,

Columbus, Ohio, assignors to Ranco Inc., Columbus, Ohio, a corporation of Ohio Application June14, 1951, Serial No. 231,464

4 Claims. 1

The present invention relates tov a control mechanism for refrigerators, and more particularly to a control mechanism to cause periodical defrosting of the evaporator of a mechanical refrigerator.

Another object of the present invention is to provide a control mechanism for a mechanical refrigerator, which mechanism is-operative to initiate defrosting cycles. in the evaporator of the refrigerator Vat predetermined times and to terminate such defrost cycles when the temperature of the evaporator reaches a predetermined temperature above the melting point of frost.

A more specific object of the invention. is to provide a control mechanism of the character referred to having a motor-driven time mechanismwhich includesl a normally relatively slowly driven actuator for moving a reciprocable control member from a normal control position tol a` defrosting control position at a predetermined time and which actuator-.is moved. quickly beyond the range of contact with thecontrol member following actuation of the control member thereby so that the control. member may be returned to its normal position within a brief period without interference with the actuator.

Another object of the invention is to provide a control mechanism of the character described having a member movableY in response to the temperature of theevaporator of the refrigerator to move the control member t its normal position to terminate the defrosting cycles, and which mechanism rincludes yielding means between the motor driven control member actuator and the control member so that the actuator cannot be stalled by the control member in the event the control member is held in its normal position by the temperature responsive member.

Other. objects. and advantages of the invention will be apparent from the following description of preferred. formsof embodiments ofthe invention, reference being had to the. accompanyingdrawings wherein;

Fig. 1 is a plan view of an automaticdefrost control for an electrical refrigerator embodying the invention, certain parts being shown broken away;

Fig. 2 is a sectional view taken substantially along line 2--2 "of` Fig. 1

Figs. 3, 4 and 5 are fragmentary sectional views taken substantially online 3"-3 of Fig. 1, show.- ing certain parts of the control mechanism in different positions;

Fig. 6 is a schematicshowing of an electrical refrigerator motor and evaporatorheater cir- (Cl. 20G-38) cuits, and a switching device of the defroster control connected therein; and

Fig. '7 is a view similar to Fig. 6, but showing the defroster control switch in a dierent position.

Referring to the drawings, a control mechanism It embodying the invention is shown which is operative to initiate and terminate defrosting cycles in the evaporator of an electrical motordriven refrigerating apparatus R. The refrigerating apparatus comprises a compressor and motor unit M, a condenser C and an evaporator E, all connected to form the well known compressor-condenser expansion refrigerating system. The power for the motor is supplied through lines LI, L2 and the operation of the compressor motor is controlled by a thermostatically operated switch T which may be of any conventional construction and is preferably responsive to the temperature of the evaporator. An electrical heating element H is arranged to heat the evaporator E and melt the frost therefrom when the heater is energized. Thecontrol mechanism I0 is operative to open the circuit for the motor M and close the heater circuit to defrost the evaporator at a predetermined hour -of each day, and to open the heater circuit and reclose the motor circuit to restore normal refrigeration when the temperature of the evaporator has reached a predetermined maximum. It is to be understood that the invention could be used in connection with mechanical refrigerating systems other than that disclosed and that other means for applying heat to the evaporator to defrost the same could be employed.

The control mechanism I0 includes a housing Il having a snap switch I 2 supported inA one end thereof. Any suitable switching mechanism could be used and in the form shown the switch comprises a base I3 formed of a suitable dielectric material having terminal memberslll,l I5,

'I6 attached thereto and projecting therethrough to the exterior of the housing.` The terminal member I4 is part of a bridge-like bracket I 4' which carries a fixed Contact Il on the interi-or of the housing and spaced from the base It. The terminal member I5 is part of a bar which is attached to base I3 and carries a contact I8 which is spaced from and opposite the contact I'I. A double `contact I9 is carried on one end of a pivoted contact strip 2t which end is snap moved between the contacts I l, It to alternatelyV engage contact I9 with the latter contacts.Y The opposite end of the contact strip 2i) is attached toa bracket 2l ofvwhich the terminal lisa 3 part and the contact strip is formed of conducting material so that a circuit may be established from the terminal I6 through the contact strip to either terminal I4 or I5.

lhe strip 25J is snap moved in opposite directions by a toggle member 22 which is disposed in a central opening in the strip and has one end pivoted to the strip and the opposite end of the toggle member has spaced stops which engage opposite surfaces ci a stop lug 2 la to limit the swinging movement of the toggle. A tension spring 23 is connected at one end to the swinging end or the toggle and the opposite end is attached to a tongue 24 which extends from a leg 25 of an l.. -shaped operating lever 25 which is pivoted to shoulders 21 on the bracket 2|. The tongue 24 is adapted to extend through the opening in the contact strip, and when the lever 2B is oscillated the spring 23 is shifted so that its line of tension moves from one side to the other of a dead center line, extending through the pivot of the toggle member and the axis of the spring, and the toggle member is thereby snapped from one of its stops to the other and urges the contact strip in one direction or the other between contacts il, i3 as the case may be. The leg 25 of lever 25 includes an extension 28, preferably formed of dielectric material which strikes the bracket lll to limit clockwise movement of the lever 25.

The particular' switch construction shown is the subject of the United States patent of Estel C. Raney, No. 2,551,590, and as mentioned previously this particular construction is not essential to the invention.

The pivot for the operating lever 25 is located relative to the toggle member 22 so that the tension of the spring 23 tends to rotate the lever clockwise when the axis of the spring moves to the upper side of the center of contact strip 20, as seen in Fig. 6, and urges the lever counterclockwise when the center tension is on the lower side of the contact strip, as seen in Fig. '1. By this arrangement the operating lever 26 is urged by the spring 23 to either of two extreme positions, which may be referred to as control positions, and by initially moving the lever a predetermined distance from either control position toward the other, the spring 23 becomes effective to urge the lever to the other position.

rEhe switch mechanism is connected in the circuit of the refrigerating apparatus so that when the operating lever 26 is in the position shown in Fig. 6 the circuit for the motor M is established from LI through the switch T, motor M, contacts l1, I9, contact strip 20, terminal I6 to L2, and when the operating lever is moved counterclockwise to the position shown in 7, the motor circuit is interrupted at the contacts I1, I9 and a circuit through the evaporator heater H is established. from line Ll through heater H, contacts i8, lil, contact strip 20, terminal I6 to line L2.

The operating lever 25 is moved from the position shown in Fig. 6, which may be considered its normal position, to the defrost cycle initiating position shown in Fig. '1 by a clock or time device 32, and is moved from the defrost position to its normal position by a thermoresponsive mechanism 33 which is responsive to temperature in the evaporator to terminate the defrost cycle and restore normal refrigerating cycles.

The time mechanism 32 preferably comprises an electric synchronous motor 35 which drives an eccentric through a suitable reduction gear train which drives the eccentric at one revolution per hour. A pawl 31 is attached to the eccentric and is oscillated thereby to drive a ratchet wheel 38 mounted on a shaft 45 which is journalled in a bushing 42 in a wall of the housing H. The ratchet wheel 33 preferably has twenty-four teeth, and the pawl 31 advances the wheel one tooth per hour so that the wheel makes one revolution each twenty-four hours. The pawl 31 has a slot 43 therein into which the wheel 38 projects, and a spring 45 urges the pawl into engagement with the ratchet teeth of the wheel. By this construction, the walls of the slot 43 cooperate with the sides of the ratchet Wheel to guide the pawl in its reciprocation. The ratchet wheel has sufficient resistance to rotation thereof to prevent movement of the pawl along the inclines of the ratchet from rotating the wheel counterclockwise, as viewed in Fig. 2.

In the preferred form the ratchet Wheel 33 is frictionally connected to the rod 4l) so that the rod may be rotated manually counter to the direction of rotation of the ratchet, and a friction clutch is provided which comprises a flange 45 formed integral with the rod 46 and a hub and flange 43 formed integral with the ratchet wheel 38, and the flanges 46 and 43 face one another and have a washer 49 of suitable friction material therebetween. The flange 48 is urged against the washer by a coil spring 5| which surrounds a portion of the rod and is compressed between the ratchet wheel 33 and a disk 54 on the rod.

As actuator is carried on the shaft 40 so that it may rotate freely relative to the shaft, and the actuator comprises a disk-shaped member 56 having an arm 51 projecting radially therefrom. The arm 51 is arranged to engage and depress a leaf spring 58 attached to the leg 60 of the operating lever 25 to move the lever to initiate a defrosting cycle as the disk 55 rotates on the shaft. It is desirable that the movement of the disk 55 through that segment of its rotation in which the arm 51 engages the spring 53 of the lever 25 be greatly accelerated over the speed of rotation of the shaft so that the switch actuating lever can be restored to its normal position within a relatively short period Without interference with the arm 51. To provide for the accelerated movement of the actuator disk 56, the disk is rotated by the driving member or disk 54 which is attached to and rotates with the shaft 4D and is connected with the actuator by a torsion spring 62 and a lost motion connection. The lost motion `connection is eiected by two axially projecting stops 63, 64 located adjacent the periphery of the driving disk 54 and which are located at 180 with respect to one another. The stops 63, 64 are arranged to engage opposite sides respectively of the arm 51. The torsion spring 52 is coiled around the rod 40 and one end thereof is hooked to the stop 64 and the other end is hooked to arm 51 and tends to urge the actuator disk 56 in the direction of rotation of the rod 4l] by the ratchet wheel 38 and urges the arm 51 to the stop 64, as shown in Fig, 5.

The actuator disk 56 is restrained from rotation by the torsion spring as the arm 51 thereof approaches the spring 53 by a restraining means comprising a detent spring 61 attached at one end to a wall of the housing Il and having the other end yieldingly disposed in the path of the arm 51. When arm 51 engages the detent 61 as age'zgees shown in Figf.- 3 its` rotation is arrestedfuntili'stop (i3V engages and drives it to deflect the-detentto release the arm. Thestoppage of rotation ofthe actuator disk 56 by engagement. ofthe arm 51 withthe detent causes the tension ofthe. torsion spring 62 to ybuild up as the disk- 551 is rotated and When'the arm 51 is positively moved by the disll54 to actuate the detent-to release the-arm, the torsion spring snap Ymoves ther arm Yto stop 54 andv during the snap movement arm 51 engages the spring 58 and deflectsV the operating lever 26, as seen in Fig. 4. Thev stop 54' is located relative to stop 63 to assu-re sufficient movement` of` the arm 51 that it Will pass from the range of engagement with the spring 58 so that the operating lever can be returned "to itsnormal position within a much shorter period. than. -would be required for the rod 40 to rotate through the angle in which arm- 51 is effective to movey the operating lever to the. defrost position.

In the form shown, stop` 64 is 180 from. stop 53, but this angle could be more orless'provided the angle through which arm 51 issnapped is suflicient to clear the spring 58 .of the operating lever as` described.

When the control lever 25 is moved by thearm 5i to initiate defrosting it engages a lever 10 which is pivoted on a pin 1i supportedin the Walis .of the` housing Il. The. lever 1li is preferably formed of sheet metal andthe end opposite the pivotedend has an upturned lip which is engaged` by the` leg 60 of the operating lever. Preferably the leg 55 is formed of insulating material to prevent short-circuiting through the lever-15.

The lever 'Itis a part ofthe thermoresponsive mechanism 33 and it is movableV clockwise by an expansible Wafer 124 to return the lever 261:0y its normal position when the temperature. of: the evaporator `has reached a predetermined vdegree above the melting point of frost.` The wafer 12. is attached to a plate 13 which is supported in an opening'v in the housing- Il and it has a button 14 which engages a turned edge portion 15 of the lever 1l). The Wafer has a tube 11 connected therewith and the tube has a bulb 18 at its outer end. which is suitablyv secured in heat exchange relationwith theevaporatorE. The Wafer, tube and bulb; are lled .with a vapor, such as methyl chloride or sulphur dioxide,r and the vapor vpressure varies according to the temperature of the bulb, as is Well understood in the art. Accordingly, as the temperature of the evaporator and bulb increases the vapor pressure increases and the wafer urges the lever clockwise to move the operating lever 26 toward its normal position. Clockwise movement of the lever 10 is limited by a stop 80 struck inwardly from a wall of the housing Il.

The movement of the lever by the Wafer 12 is opposed by a tension spring 3|, one end of which is hooked to a lug 82 on the lever 10 and the other end of which is attached to a nut 83 threaded on a bolt 84 rotatably supported in a bearing in a Wall of the housing H.

Preferably, the head of the bolt 84 is slotted so that the bolt may be rotated by a screwdriver to move the nut 83 therealong and thereby change the tension of the spring. The tension of the spring governs the temperature at Which the lever 10 is moved by the wafer 12 to cause the operating lever 26 to be returned to its normal position, and ordinarily the spring 8| is adjusted so that the operating lever is returned to its evaporator andy bulb: isatleast several degrees above the-melting point of frost;`

It is tor be noted that spring 58,` normally yieldingly moves the operating lever 26 when it is defiected by the arm 51 as described, `butin theevent lever `1l) is in a position toblock movermentof the operatingzlever to initiatedefrosting, springd58 yields to the arm 51 sothatthelatter passes ontoy the stop. 64,. although the operating leverhas notzmovedto cause defrosting..l This situation may occur when the. temperature-V of the evaporator is relatively high.. due to` loading of the refrigerator with warmr articles, or by prolonged orfrequent: opening of the; refrigerator cabinet door. The spring 58 thus eliminatesthe possibility. of' thearm 51v becoming stalled,` in the situation vjust mentionedg. and causing distortionor damage; to partsor stallingof the synchronous. motor;

It is desirable toprovide for, theselection of the hour of day at which the defrost'cyclesv will occur, andA this selection may bemade by, setting the driving disk 51.at a predetermined angular position by rotatingthe rod 40; Af knob 85fis `drivingly connectedto. the outerend of theirod 4l! bya key 81 attached to the rod, and the knob preferably has a pointer thereon (not shown) Whichregisters with a dial (not shown) on the face. ofthe housing. The dial preferably; has

vtwenty-four'markers indicating the hours ofv the day, and assuming that the knob ismounted on the rod so thatthe defrosting cyclesv are initiated whenthe pointer is at the 2:0()V a. m. marking, theknob can' be rotated accordinglyyto cause de.- frosting to occur at any other desired hour. The clutch mechanism comprisingpflanges t6. A18 and Washer 49 permits the rod. Mito be rotated by the knob in either direction, althoughfthe ratchet wheel is prevented by thev pawl from rotation in ,one direction.

Alternatively, the friction clutch between the rod 4D ,and ratchet Wheel llcouldbe omitted and the rod could rthen be turned, only in thedirection of rotation of the ratchetwheel to change theidefrost hour.

By our invention We have provided a relatively inexpensivev andreliable control mechanism for automatically initiating andterrninating defrosting cycles.v in mechanical refrigerators.` The mecha-nismis. particularly suitable for use in refrigerators having means for accelerating the application of heat to the evaporator to melt collected ice or frost therefrom since the clock operated member for initiating the defrosting cycle is quickly removed from its actuated position following the initial operation of the control mechanism. Furthermore, in the event the evaporator is too warm for effecting the defrosting operation, the time mechanism cannot be stalled by the inability of the control lever to move to its defrosting position.

While the preferred form of the invention has been shown, it is to be understood that other forms and adaptations of the invention may be made without departing from the spirit of the invention as defined in the claims which follow.

Having thus described our invention, We claim:

1. A control mechanism comprising a control member movable between two control positions, means for moving said member from one of said positions to the other, an actuator movable in a path in Which it moves into and out of range of operative engagement with said control member to move said member from said other position normal position when the temperature in the toward the rst mentioned position, power means lincluding a driving member having a lost motion driving connection with said actuator permitting movement of said actuator independently of said driving member through said path, spring means urging said actuator from one limit of said lost motion connection and operative to move said actuator relative to said driving member through said path to actuate said control member, and means to prevent movement of said actuator by said spring through said path, the last mentioned means operative to release said actuator in response to predetermined movement of said actuator by said driving member.

2. A control mechanism comprising a control member movable between two control positions, means for moving said member from one of said positions to the other, a rotatable actuator including an arm movable in a rotary path in which it moves into and out of range of engagement with said control member during movement through a predetermined segment of said path to engage and move said member from said other position toward the rst mentioned position, power means including a rotating driving member having a lost motion driving connection with said actuator permitting rotation of said actuator relative to said driving member to cause movement of said arm through said segment of said path independently of said driving member, spring means urging said actuator from one limit of said lost motion connection and operative to move said actuator through said segment of said path to actuate said control member, and means to restrain movement of said actuator by said spring through said segment of said path, the last mentioned means operative to release said actuator in response to predetermined movement of said actuator by said driving member.

3. A control mechanism comprising a control member movable between two control positions, means for moving said member from one of said positions to the other, a rotatable actuator including an arm movable in a rotary path in which it moves into and out of range of engagement with said control member during movement through a predetermined segment of said path to engage and move said member from said other position toward the first mentioned position, power means including a rotating driving member having a lost motion driving connection with said actuator permitting rotation of said actuator relative to said driven member to move said arm through said segment of said path independently of said driving member, spring means urging said actuator from one limit of said lost motion connection and operative to move said actuator through said segment of said path to actuate said control member, means to restrain movement of said actuator by said spring through said segment of said path, the last mentioned means operative to release said actuator in response to predetermined movement of said actuator by said driving member, and means forming a resilient operative connection between said actuator and control member to permit movement of said arm through said segment of said path in the event the iirst mentioned means is operative to urge said control member toward said other position.

4. A control mechanism comprising a control member movable between two control positions, means for moving said member from one of said positions to the other, a rotatable actuator movable in a rotary path in which it moves into and out of range of engagement with said control member to engage and move said member from said other position toward the first mentioned position, power means including a driving member having a lost motion driving connection with said actuator permitting rotary movement between said driving member and actuator during movement of said actuator through said path, spring means urging said actuator from one limit of said lost motion connection and operative to move said actuator through said path to actuate said control member, and a yieldable detent engageable by a part of said actuator to restrain movement of said actuator by said spring through said path, said detent being deected by movement of said actuator by said driving member and operative to release said actuator at a predetermined angular position of the latter.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 826,331 Harthan July 17, 1906 2,297,090 Weaver Sept. 29, 1942 2,366,635 McCloy Jan. 2, 1945 2,553,846 Clemens May 22, 1951

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