US2564868A - Temperature control thermostatic switch device - Google Patents

Description

Aug. 21, 1951 I v. WEBER ETAL TEMPERATURE CONTROL THERMOSTATIC SWITCH DEVICE 2 Sheets-Sheet 1 Original Filed Feb. 19, 1946 pa R A $2 f H my M i m I .A mm v wm H T Aug. 21, 1951 v. WEBER ET AL TEMPERATURE CONTROL THERMOSTATIC SWITCH DEVICE 2 Sheets-Sheet 2 Original Filed Feb. 19, 1946 Patented Aug. 21, 1951 TEMPERATURE CONTROL THERMOSTATIC SWITCH DEVICE Victor Weber and William S. Kunzler, Greens burg, Pa., assignors to Robertshaw-Fulton Controls Company, Greensburg, Pa., a corporation of Delaware Continuation of application Serial No. 648,780, February 19, 1946. This application December 27, 1948, Serial No. 67,532

10 Claims.

This invention relates to control devices and, more particularly, to condition responsive controls for electrically driven apparatus such as clothes dryers. This application is a continuation of our copending application, Serial No. 648,780 filed February 19, 1946 now abandoned.

Appliances of this nature may include a motor driven shell or drum in which the clothes are placed and an electrical heating element from which heated air may be circulated by a fan or blower throughout the load of clothing which is undergoing the drying operation. It is apparent that considerable latent heat remains in the load upon completion of the drying operation although the heating element has been cutoff. Hence, the load cannot be removed from the appliance with safety until after a cooling-down period which should not be too prolonged.

An object of this invention is to render the control of the clothes drying operation fully automatic after the starting operation is accomplished.

Another object of the invention is to ensure a predetermined cooling-down period before the drying operation is completed.

Another object of the invention is to further dry the load of clothing during the cooling-down period.

Another object of the invention is to eliminate the possibility of damage to the clothing should the appliance become unattended after being started.

Another object of the invention is to require a manual resetting operation to again place the appliance in full operation after an initial heating cycle.

Other objects and advantages will become apparent from the following description taken in connection with the accompanying drawings, wherein:

Fig. 1 is a front elevation of the heat control device;

Fig. 2 is a side elevation with-portions of the cover of the device broken away to show the inside structure;

Fig. 3 is a front elevation similar to Fig. 1 but with the front cover removed;

Fig. 4 is a rear elevation of the device with the rear cover removed;

Fig. 5 is a side elevation similar to Fig. 2 but showing other details of construction;

Fig. 6 is a. partial enlarged section taken on the line V'I-VI of Fig. 3;

Fig. 7 is a section taken on the line VII-VI of Fig. 1; and

2 Fig. 8 is a wiring diagram. Referring more particularly to the drawings, a main housing for the heat control structure comprises an L-shaped frame It to which is secured by the screws I2 a channel-shaped cover I4. The arrangement provides a housing having an open end within which a block I6 of insulating material is securedby means of the screws I8. As shown in Fig. 5, the frame I 0 is adapted to be fastened to an accessible portion of the appliance (not shown) by means of the lugs 20 through which suitable securing means may project.

The cover I4 is provided with a centrally located boss 22 having an axial opening in which a spud-piece 24 is secured and projects outwardly of the cover I4. Journalled on the spud-piece 24 is a bushing 26 carrying a handle 28 having a dial 3B thereon. The dial 30 carries indicia representing the various heatingpositions together with an off positionall of which cooperate with a stationary reference point 32 formed on an escutcheon plate 34 which surrounds the dial 30 and is secured to the cover I4 by a bracket 36.

The handle 28 is non-rotatably mounted on the bushing 26 by cooperation with a cam element 38 which, as shown more clearly in Fig. 5, is formed on the bushing 26 intermediate the ends thereof. The handle 28 is provided with a recess 40 on the inner face thereof which interlocks with the cam element 38 to prevent relative rotation between the handle and the bushing. The cam element 38 is adapted for engagement with an operating bar 42 upon rotation of the handle 28 to off position. The bar 42 projects from the interior of the cover I4 through the boss 22 thereon and is slidably supported adjacent the cam element 38 by a portion of the bracket 36. The cam element 38 is provided with a stepped portion 44 with which the operating bar 42 is adapted for engagement to prevent further rotation of the handle 28 in a.clockwise direction beyond the off position. The operating bar 42 is normally urged outwardly of the cover I4 by a leaf spring 46 secured to the front wall of the cover I4 and extending. through a slot formed in the operating bar 42 as shown in Fig. 5.

The spud-piece 24 also carries a threaded element or stud 48 having a detentj'50 projecting laterally from one end and. cooperating with a slot 52 formed in the bushing 26 to prevent rela-' tive rotation. The inner end of the stud 48 supports an expansible and contractible diaphragm 5.4 and serves to move the diaphragm relative to the cover I4 upon rotation of the handle 28. The interior of the diaphragm 54 is in communication with a capillary tube 56 which is partly coiled in- .side the boss 22 and extends therefrom exterior ,provided in the bulb 60 and the capillary tube 56 so that upon expansion of the liquid as a result of the heat to which the bulb is subjected the liquid will be forced through the tube into the expansible and contractible diaphragm thereby actuating it to a sufficient extent to operate parts now to be described.

A button 62 provided on the face of the diaphragm 54 opposite the stud 48 abuts a depression formed in a main actuating lever 64. This lever, which is generally of U-shaped conformation, is provided with a knife-edge 66 serving to connect the legs of the U-shaped lever and which is seated in a knife-edged bearing 68 formed on a bracketlO secured to the inner wall of the L- shaped frame I0. The base of the main actuating lever 04 is recessed at the center portion to provide a seat for one end of a tension spring 12, the other end of which is hooked in an aperture formed in the center cross bar 14 of an R-shaped control lever 16.

, The two legs 18 and 80 of the control lever iii are provided with knife edges cooperating with spaced knife-edged bearings 32 formed in a channel-shaped support 84 extending substantially parallel with the base of the frame I0. As shown more clearly in Fig. 6, the support 84 carries proiections 86 which are loosely mounted in the wall of the L-shaped frame I adjacent the base thereof and serve to retain the sup ort in position at one end thereof. Lateral displacement of the control lever 16 is prevented by a bracket 90 carried by the inner wall of the frame I0 and having arms projecting on each side of the legs I8 and 80. The su port 84 also carries at the front end an adjusting screw 88 which may be adjusted to raise or lower the support 04 and change the tension of the spring I2 as desired.

An .inverted V-shaped take-up arm 92 is attached to the control lever I6 rearwardly thereof by means of forwardly projecting spaced lugs 94 suitably notched for engagement with oppositely dis osed shoulders 96 formed on the le s I8 and 80 of the control lever 16. The take-up arm 92 is further provided at the o posite end with a hook 98 which extends around the underside of the cross-bar of the R-shaped control lever I6 at the central portion thereof. The hook 98 limits the movement of the take-u arm 92 with res ect to the control lever I6 and cooperates with the lugs 94 to attach it thereto.

The, take-up arm 92 extends laterally bevond the cross-bar of the control lever 16 and carries a contact block I00 of insulating material mounted thereon-for restricted pivotal movement in a horizontal plane. A contact bridge I02 is secured to the rear face of the contact block I00 for cooperation with contacts I04. I06 mounted on the insulating block I6 and pro ecting exteriorly of the cover I 4. It will be observed that in this embodiment the contact I04 is provided with terminal connections including the screw I08 while the contact I06 is adapted for permanent connection with a conductor I I0. It will be apparent. however, that such arrangement can be modified as dictated by the circuit arrangement with which the control apparatus is used.

The structure so far described constitutes a snap action mechanism by means of which the control lever I6 can effect contact operation. Thus, as the liquid in the bulb 60 and the capillary tube 56 expands in response to temperatures prevailing at the oint where the bulb is located, the diaphragm 54 will also expand and urge the free end of themain actuating lever 04 toward the knife-edged bearing 62 of the control lever I0. Due to tension of the spring .12, the control lever I6 and its companion take-up arm 92 will be moved to the right as viewed in Fig. 2 with a snap action as the actuating lever 64 moves overcenter past a line between the respective bearings of the two levers. Such snap action causes engagement of the contact bridge I02 and the contacts I04, I06, as will be apparent.

The closed position of the contacts I02, I04 and I06 will continue untilthe diaphragm 54 starts to contract upon cooling of the bulb 60' whereupon a similar over center snap action will occur but inthe opposite direction to cause contact disengagement'as the contact lever "I6 resumes its normal position as shown in Fig. 2. Separation ofthe levers 64 and "I6 under bias of the spring I2 is prevented by a limit stop member I09 which is secured to the insulating block I 6 and extends into the path of movement of the lever I6.

Additional contacts are provided for support by the insulating block I6 and are located to one side of the contacts I04, I06. These contacts may be two in number and are designated H2 and H4, respectively. The conductor H0 connects contact I06 with contact II2 permanently, while contact I I4 is similar to contact I08 in having a terminal connection including a screw II6. The contacts I4, I06 which, as stated, oooperate with the contact bridge I02 are also provided with back contacts H8 and I20, respectively. The back contacts II8, I20 and the contacts H2, H4 cooperate'with a pair of contact bridges I22, 524, respectively.

The contact bridges I22, I24 are mounted upon separate insulating plates I26 carried by flexible members I28 upon the opposite bifurcated ends of a secondary lever I30. The secondary lever I30 extends between the arms of the bracket and is provided with lateral projections I32 pivotally mounted in the arms 90 and serving to support the secondary lever and associated parts in condition for pivotal movement to engage and disengage the contact bridges I22 and I24. A compression spring I34 is mounted between the secondary lever I30 and the inner wall of the frame I 0 on the side of the pivotal mounting opposite the contact bridges I22, I24, thus serving to bias the contact bridges out of engagement with the contacts IIB, I20, and H2, H4, respectively.

The secondary lever I30 is adapted to be operated during the snap action of the main actuating lever 64. Thus, interengaging means on the main lever 64 and the secondary lever I30 are provided andtake'the form' of a rocker I36 mounted on a' pivot I38 supported on the depending portion of an angular arm I40 projecting from the bracket 90 immediately below and inwardly of one of the arms thereof. The rocker I36 extends toward the main actuating lever 64 in position to be engaged thereby when over center-snap action occurs. Preferably, the rocker I36 has a ramp I 42 formed thereon and the lever 64 is provided with a lateral projection I44 which will ride along the ramp I42 and serve to. tilt the rocker I36 during the over center snap action of the lever 64.

In order to maintain the contact bridges I22, I24 in engagement with their respective contacts, the bias of the spring I34 is overcome by a latching arrangement now to be described. The underside of the rocker I36 is engaged by the free end of a U-shaped strip of spring metal I46 which is secured to the channel-shaped support 84 and has its free end spaced therefrom. The opposite end of the rocker I36 is thus urged. about the pivot I38 toward a projection I48 which is formed on a depressed portion of the secondary lever I 30. Latching engagement between the secondary lever I30 and the rocker I36 is secured by forming the end of the rocker adjacent the projection I48 with a notch I56 with which the projection I48 may engage. As shown in Figs. 2 and 6, the secondary lever I30 is in what may be termed the unlatched position, notch I50 being disengaged from the projection I48. In this position, the spring I34 has biased the secondary lever I30 from normal latched position so that the contact bridges I 22, I24 are disengaged from their respective contacts. A button I52 is provided on the exterior of the cover I4 to reciprocate a pin I54 carried by and extendin into operative engagement with the secondary lever I30 when the button I52 is depressed. The pin is normally biased out of engagement with the lever I30 by a compression sprin I56 operative between the button and the cover I4. The pin I54 engages the lever I30 on the side thereof opposite the projection I48 and thus serves to pivot the lever against the bias of the lever spring I 34.

Secured to the back of the L-shaped frame I0 is a housing I58 of insulating material. A pair of oppositely disposed screws I60 xtending between the frame I0 and the housing I58 serve to secure these parts together. The housing I58 carries on one side thereof a pair of fixed contacts I62, I64 with which a movable contact bridge I66 is adapted to cooperate. The contact I64 is in the nature of a permanent connection inasmuch as a conductor I68 is permanently connected at one end thereto. The contact I62, however, is provided with terminal connections includin the screw I10.

The contact bridge I66 is carried by a switch arm I12 of insulating material which is pivoted by a mounting I13 on a frame I14 secured by means of the screw I16 to the housing I 58. A coil spring I18 operative between a projection I19 on the frame I14 and the switch arm. I12 serves to bias the latter and therefore the contact bridge I66 carried thereby into engagement with the contacts I62 and I64. Disengagement of these contacts I62, I 64 with the contact bridge I65 is effected by a pin I80 which extends from the mounting I 13 through alined apertures in the housing I58 and the frame I0 for engagement by the adjacent insulating plate I26 which is carried by the secondary lever I30. It is apparent that contact bridge I66 is either disengaged or engaged with its contacts simultaneously with the disengagement or engagement of contact bridges I22, I 24 with their contacts.

The other portion of the housing I58 is provided with a pair of flexible switch arms I82, :84 carrying contacts I86, I88, respectively at their free ends. The switch arms I 82, I84 are secured at the opposite ends to the housing I 58 by screws I90 and are provided with separate terminal con- 6 nections I92. The contacts I86, I88 are adapted to cooperate with contacts I94, I96, respectively, which are secured to the housing I58 by screws I91. The conductor I68 is connected at its oppo-v .tends from the base of the housing I58 inter-- mediate the switch arms I82, I84 and serves as a pivot point for one end of an actuating plate 202 of insulating material which underlies the switch arms I82, I84. The other end of the plate 202 is suported on the end face of a hollow projection 204 which carries a pin 206 adapted for free reciprocation therein. The pin 206 extends through suitable alined apertures in the wall of the housin !58 and frame I0 for engagement by the end of the operating bar 42 as shown clearly in Fig. 7. The arrangement is such that upon longitudinal movement of the operatin bar 42 in a right-hand direction as viewed in Fig. '1, the pin 206 will move the plate 202 and serve to disengage the contacts I86, I88 from their related fixed contacts A I94, I96.

Referring now more particularly to the wiring diagram shown in Fig. 8, it will be apparent that the pair of terminals I 92 may be connected by line wires 203, respectively, to a source of electrical energy such as a house current supply. A heating element A has one end connected by a wire 2I0 to the terminal l1! and the opposite end connected to one end of a second heating element B which has its opposite end connected by a wire 2I2 to the terminal I IS. A ground wire 2 I 3 is tapped into the connection between the heating elements A and B.

Heat distributing means in the form of an electric motor-operated fan or blower (not shown) is provided for circulating heated air throughv the load of clothing which is placed in the drying drum (not shown) to be dried. The motor may also operate the drum which revolves during the drying operation. The motor is shown in Fig. 8 as having one terminal connected to ground and the opposite terminal connected by a conductor 2I4 to the terminal I68. Further description of circuits for the heating elements and the motor will be given in connection with the description of the operation of the device, which follows.

In the operation of the device it may be assumed that the dial 30 is in the ofi position so that the cam element 36 has forced the operating *bar 42 inwardly to engage and move the pin 206 and thus operate the flexible switch arms I 82, I84 to disengage the contacts I86, I88 thereon from the contacts I94, I96, respectively. Thus, the current is broken on both sides of the line and movement of the handle 26 in a counter-clockwise phragm 54 and the button 52 to the right but is insufficient to operate the main actuating lever: 64 and cause snap action or the control lever 16.

Thus, the auxiliary switching means for the motor comprising the contact bridge I02 remains in position where the contacts I04, I06 are disengaged. However, the operating bar 42 no longer causes disengagement of contacts I86, I88 from contacts I94, I96, respectively. The button I52 is then operated to cause the pin I54 to engage and move the lower end of the secondary lever I30, thus overcoming the bias of the spring I34 and permitting the spring arm I46 to tilt the rocker I36 and engage notch I50 with projection I48. The secondary lever I30 is thus latched in its forward position with the contact bridges I22 and I24 in engagement with the contacts II8, I and H2, H4, respectively. Due to the forward movement of the secondary lever I30 the contact bridge I66 is simultaneously moved by the contact arm I12 under bias of the spring I'I8 into engagement with the contacts I62, I64 as previously explained.

A circuit may now be traced on Fig. 8 from the right-hand line wire 208, terminal I92, contacts I88, I96, wire I68, contact I62, contact bridge I66, contact I64, wire 2I0, heating element A, heating element B, wire 2I2, contact II4, contact bridge I24, contact II2, wire I98, contact I94, contact I86, terminal I92 and left-hand line wire 208. The circuit for both the heating elements is thus complete.

At the same time, a circuit for the motor may also be traced by way of a left-hand line wire 208, terminal I92, contact I86, contact I94, wire I98, contact II2, wire III), contact I20, contact bridge I 22, contact H8 and wire 2I4 to one terminal of the motor which, as stated, has its other terminal grounded. Thus, the circuit for the motor is completed and operation of both the heating element and the motor can occur.

When the temperature in the drying appliance reaches that which has been preselected on the dial, then the control will operate thermostatically. That is, the diaphragm 54 will expand sufficiently to cause the overcenter snap-action of the control lever "I6. It should be noted at this point that the control device can be adjusted so that upon a rise in temperature at the bulb 60 the auxiliary switching means for the motor comprising contacts I04, I06 and contact bridge I62 become engaged just below the preselected setting. However, as long as such contact engagement occurs substantially simultaneously with the disengagement of the other contacts due to the snapaction the operation of the motor will not be interrupted.

Thus, upon snap action of the control lever I6 the projection I44 on the main actuating lever 64 tilts the rocker I36 and releases the secondary lever I30. The contact bridges I22 and I24 carried by this lever I30 are thereby disengaged from their related contacts simultaneously with disengagement of contact bridge I66 from its related contacts I62, I64 by operation of the pin I80. The heating elements A and B are therefore deenergized but the circuit to the motor is continued through the auxiliary switching means comprising contact bridge I02 and contacts I84, I06.

When the temperature at the bulb 60 drops an amount corresponding to the differential of the thermostat then the diaphragm 54 contracts sufficiently to cause overcenter snap-action in the opposite direction. The auxiliary switching means is therefore opened by the biasing means therefor comprising the spring I2 and the motor ceases to run.

It is thus apparent that the auxiliary switching means comprising contact bridge I02 and contacts I04, I06 is operated thermostatically and will beopened and closed according to the temperature at the bulb 60. The switches controlled by the secondary lever I30, that is, contact bridges I22, I24 and I66 and associated contacts are operated thermostatically to open position but require manual resetting to closed position. Thus the heating elements remain deenergized until the control is manually operated.

It is further apparent that the motor will continue to run and will drive the fan and drum after the heating elements are cut out until the temperature at the bulb has dropped to a safe level. Thus, the clothes can then be handled without fear of burning the hands and at the same time an additional drying period is obtained.

The control is fully automatic. After the wet clothes are put in the appliance and the controls set as described, then the heating cycle and cooling down period will take place and thereafter the appliance will shut itself down. Thus, the appliance will operate safely with no attention on the part of the operator once the controls have properly been set. Cross reference is made to copending application of Weber and Garner, Serial No. 688,582, filed August 5, 1946.

It will be understood that various changes may be made in the details of construction and arrangement of parts and that th control device may be utilized for useful purposes other than clothes drying controls. The push button control could be omitted and a sliding dial utilized in place thereof. The rotating motion of the dial could be used as described for settin the tempera- P ture and axial motion for bringing the switches into contact engaged position. This and other modifications may be made within the scope of the appended claims without departing from the spirit of the invention.

We claim:

1. A control device comprising switching means having open and closed positions for controlling an energizing circuit, switching means having open and closed positions for controlling a second energizing circuit, means for closing both said switching means to establish said circuits, auxiliary switching means having open and closed positions for controlling one of said circuits independently of said switching means therefor, means responsive to changes in a condition to be controlled, means for opening both said switching means upon a change in said condition affecting said condition responsive means and for substantially simultaneously closing said auxiliary switching means to maintain said one of said circuits, and means for opening said auxiliary switching means to discontinue said one of said circuits upon a further change in said condition affecting said condition responsive means.

2. A control device comprising switching means having open and closed positions for controlling an energizing circuit, switching means having open and closed positions for controlling a second energizing circuit, manually operable means for closing both said switching means to establish said circuits, auxiliary switching means having open and closed positions for controlling the first said circuit independently of said switching means therefor, means responsive to a condition to be controlled, means for opening both said switching means upon a change in said con dition affecting said condition responsive means auxiliary switching means to maintain said first circuit, and means for opening said auxiliary switching means to discontinue said first circuit upon a further change in said .condition affecting said condition responsive means.

3. A control device forelectrical heat distributing apparatus comprising switching means having open and closed positions for controlling a heating circuit, switching means having open and closed positions for controlling a heat distributing circuit, means for closing both said switching means to establish said circuits, auxiliary switching means having open and closed positions for controlling said heat distributing circuit independently of said switching means therefor, temperature responsive 'IIlEflI'lSy-JTIGHJIS for opening both said switching means upon a change in temperature aifecting said temperature responsive means and for substantially simultaneously closing said auxiliary switching means to maintain said heat distributing circuit, and means for opening said auxiliary switching means to discontinue said heat distributing circuit upon a further change in temperature affecting said temperature responsive means.

4. A control device for electrical heat distributing apparatus comprising switching means having open and closed positions for controlling a heating circuit, switching means having open closed positions for controlling a heat distributing circuit, manually operable means for closing both said switching means to establish said circuits, auxiliary switching means having open and closed positions for controlling said heat distributing circuit independently of said switching means therefor, temperature responsive means, means for opening both said switching means upon a rise in temperature aiiecting said temperature responsive means and for substantially simultaneously closing said auxiliary switching means to maintain said heat distributing circuit, k

and means for opening said auxiliary switching means to discontinue said heat distributing circuit upon a further drop in temperature afiecting said temperature responsive means.

5. A control device for electrical heat distributing apparatus comprising switching means having open and closed positions for controlling a heating circuit, switching means having open and closed positions for controlling a heat distributing circuit, means for biasing both said switching means to open position, means for overcoming said biasing means and closing both said switching means to establish said circuits, means for latching both said switching means in closed position, auxiliary switching means having open and closed positions for controlling said heat distributing circuit, means for biasing said auxiliary switching means to open position, temperature responsive means, and means for releasing said latching means to open both said switching means upon a change in temperature affecting said temperature responsive means and for substantially simultaneously overcoming the biasing means for said auxiliary switching means for closing'the same to maintain said heat distributing circuit, said auxiliary switching means being opened by the biasing means therefor upon afurther change in temperature afiecting said temperature responsive means.

6. A control device for electrical heat distributing apparatus comprising switching means having open and closed positions for controlling a heating circuit, switching means having open and closed positions for controlling a heat distributing circuit, temperature responsive means adjustable to different temperature settings, adj llS'Ge ing means for said temperature responsive means including a reciprocable element for closi both said switching means to establish said circuits, auxiliary switching means having open and closed positions for controlling said heat distributing circuit independently of said switching means therefor, means for opening both said switching means upon a change in temperature affecting said temperature responsive means and for substantially simultaneously closing said auxiliary switching means to maintain said heat distributing circuit, and means for opening said auxiliary switching fians .to discontinue said heat distributing circuit upon a further change in temperature affecting said temperature responsive means.

7. A control device for electrical heat distributing apparatus comprising switching means having open and closed positions for controlling a heating circuit, switching means having open and closed positions for controlling a heat distributing circuit, means for biasing both said switching means to open position, temperature responsive means adjustable to difierent temperature settings, adjusting means for said temperature responsive means including reciprocable and rotatable means, said reciprocable means being operative for overcoming said biasing means and closing both said switching means to establish said circuits, means for latching both said switching means in closed position, auxiliary switching means having open and closed positions for controlling said heat distributing circuit, means for biasing said auxiliary switching means to open position, said position being established when said rotatable means is adjusted to a selected temperature setting, means for releasing said latching means to open both said switching means upon a change in temperature aiTecting said temperature responsive means and for substantially simultaneously overcoming the biasing means for said auxiliary switching means for closing the same to maintain said heat distributingcircuit, said auxiliary switching mean being opened by the biasing means therefor upon a further change in temperature affecting said temperature responsive means.

8. A heat control device for an electrical heating appliance having a heating element and a motor, comprising temperature responsive means for controlling operating temperatures in the heating appliance, switching means common to both the heating element and the motor and having open and closed positions for controlling separate heating and motor circuits, adjusting means for said temperature responsive means, manually operable means for closing said switching means and establishingsaid circuits, means for returning said manually operable means to an inoperative position, auxiliary switching means having open and closed positions for controlling said motor circuit, means for opening said switching means upon a change in temperature affecting said temperature responsive means and for substantially simultaneously closing said auxiliary switching means to maintain said motor circuit, and means for opening said auxiliary switching means to discontinue said motor circuit upon a further change in temperature affecting said temperature responsive means, said switching means and. said auxiliary switching means remaining open irrespective of subsequent temperature changes affecting said temperature responsive means until said manually operable means is operated from said inoperative position,

9. A control device for drying apparatus having an electrical heating element and an electric motor, comprising switching means for controlling energization of the motor and the current supply to the heating element, auxiliary switching means for controlling energization of the motor, and temperature responsive means for opening the first said switching means at a predetermined temperature caused by operation of the heating element and simultaneously closing said auxiliary switching means.

10. A control device as claimed in claim 9 wherein said temperature responsive means is 12 adapted to open said auxiliary switching means in response to a temperature drop below sai predetermined temperature. VICTOR WEBER. WILLIAM S. KUNZLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Cobb Apr. 19, 1949

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