US2878579A - Automatic clothes dryer control - Google Patents

Description

March 24, 1959 l. J. FUCHS 2,878,579

AUTOMATIC CLOTHES DRYER CONTROL Filed Aug. 17, 1954 Y 3 Shee ts-Sheet 1 FIG I Y 4 l9 f 0. 20a [8 22 mi ls; g

INVENTOR.

IRVIN J. FUCHS HIS ATTORNEY March 24, 1959 Filed Aug. 17, 1954 l. J. FUCHS AUTOMATIC CLOTHES DRYER CONTROL 3 Sheets-Sheet 2 FIG. 2

MIXED NYLONS & RAYONS TIME F 1 l l I 0 1o 3o 5o 3 MIXED COTTONS O TIME INVENTOR.

IRVIN J. FUCHS Byw' z, I

HIS ATTORNEY March 24, 1959 I. J. FUCHS 2,878,579

AUTOMATIC CLOTHES DRYER CONTROL Filed Aug. 17, 1954 3 Sheets-Sheet 3 I 7 an SO v myszvrox mvm J. FUCHS HIS ATTORNEY United States Patent AUTOMATIC CLOTHES DRYER CONTROL Irvin J. Fuchs, North Arlington, NJ assignor to General Electric Company, a corporation of New York Application August 17, 1954, Serial No. 450,417

13 Claims. (Cl. 34-45) This invention relates to clothes dryers, for example of the domestic type, and more particularly to an automatic control for such machines.

While clothes dryers, particularly those of the domestic type, have been controlled by operator pre-selection of operating time, by operator pre-selection of maximum interior temperature, or by a combination of both systems, experienced operator judgment is required in all cases to prevent over-drying, fabric damage, or underdrying. The problem of determining the proper period of time and the proper temperature of dryer operation is complicated by the wide variety of fabrics, the quantity of moisture in a load, and the desired degree of dryness. For example, rayons, nylons and similar synthetics require a relatively low temperature; while cottons and linels can withstand higher temperatures. Nevertheless, it may take as long to dry the synthetics as linens. The size load may vary from one or two small garments to a full capacity load of 8 to 10 pounds of dry clothes. Finally, for items to be ironed, moisture content should be from 20% to 40% of dry weight, while items for storage or immediate wear should contain less than 10% moisture.

Correspondingly, it is a primary object of this invention to provide an automatic clothes dryer control substantially eliminating the requirement of operator judgment with respect to clothes type and drying load, While permitting operator selection of a damp-dry or dry range of operation.

It is also an object of this invention to construct an automatic dryer control facilitating operator selection of certain operational requirements, by means such as pushbuttons, or other quick positive adjustment devices.

An additional object of this invention is to arrange the automatic dryer control to provide automatically a dampdry range regardless of the type of fabric or the clothes load.

Further objects of the invention include the provision of an automatic control of simplified construction, reduced manufacturing cost, and high reliability, functioning to control duration of dryer and main heater operation and terminating an operational cycle with a cooldown period during which only the dryer drive is operating without heater operation.

Briefly stated, in accordance with one aspect of my invention, the primary automatic control means for a clothes dryer includes a thermally responsive switch which is arranged to respond automatically and jointly to the dryer temperature and also to the operation of means which introduces a time function into the operation of the switch. That is, the over-all resultant deflection controlling the thermal switch operates automatically in accordance with the dryer temperature and also a controlled time function. The latter control is manually adjustable at the will of the operator so that a variation in the shutdown time and temperature may be effected; this control for the time function is automatic in the sense that the operator has only to operate .a control "ice element either to a dry or a damp-dry position to obtain the corresponding result.

In accordance with the illustrated and preferred embodiment, an auxiliary circuit for the dryer is provided with a thermostatically controlled switch for maintaining the dryer drive motor in operation after termination of heater operation, thereby providing a short cool-down period to permit comfortable removval of articles of clothing at the completion of the cycle, although this refinement it is not necessary in all embodiments of the invention.

My invention will be better understood from the following description taken in connection with the accompanying drawings, and its scope will be pointed out in the appended claims.

In the drawings, Fig. 1 is a front elevation, partially in section, of an exemplary clothes dryer embodying this invention; Figs. 2 and 3 are graphic illustrations of the relationship between exhaust temperature and time for different types and sizes of clothes loads; Fig. 4 is a schematic electrical diagram illustrating the automatic control system of this invention; and Fig. 5 is a partial schematic electrical diagram showing a modification of the electrical circuit in accordance with this invention.

Referring now to the drawings, in Fig. l I have shown my invention as applied to a clothes dryer of the domestic type, although obviously the invention is not limited solely thereto. In a typical fashion, a clothes tumbling basket 1 is rotatably mounted within an enclosed cabinet structure consisting of side walls such as 2, a top 3 including integrally therewith a backsplash panel 4, and a recessed toeboard 5 at the base of the machine. Basket 1 is an enclosed cylindrical drum having a toraminated peripheral wall 6, a rear wall 7, and a front wall 8 provided with a centrally located loading opening 9 therein. Thus, articles of clothing may be placed within the basket 1 for tumbling by rotating the basket by any suitable drive means, not shown in Fig. l, but referred to schematically in Fig. 4 as will be described presently.

As well known in the art, clothes dryers usually operate on the principal of applying heat to the articles being tumbled within the basket, thereby to evaporate the moisture is thereafter either discharged into the room or condensed for discharge to a drain. Air flow may or may not be provided, depending upon specific dryer design. However, in the present instance, by way of example, I have shown a clothes dryer of the type employing, in addition to heat, air flow to expedite the extraction of moisture from the articles being tumbled within the basket. This air flow may be induced by a suitable fan or blower 10 rotated by the same drive means which provides motive power to rotate basket 1. As shown in Fig. 1, blower 10 draws fresh air into the machine through a screened inlet opening 11 in the toeboard of the machine, forcing this outside air into the machine through an outlet 12 as shown by the arrows. Within the cabinet structure, a bafile 13 may be provided to direct the air upwardly along the outside of the basket in the direction of an electric heating element 14. After flowing over the heating element, the air enters the basket through the foraminated cylindrical wall 6, to pass downwardly through the clothes and out the opposite side of the basket. The discharged and spent air is conducted through a lint trap of appropriate construction (not shown) to an exhaust outlet 15, which also may be screened as at 16.

Positioned within the dryer cabinet is a temperature sensing device indicated generally at 17 in Fig. 1. Preferably this device is positioned within the dryer to sense as closely as possible the temperature of the clothes. Obviously, the device 17 cannot be placed within the being tumbled within the basket.

-It is, of course, desirable that the machine include some means by which it may be pre-set, whereby it may be adjusted-for variables such as the type of load (nylon,

silk, cotton, linen, etc.) and for damp dry or full dry operation.

In Fig. l, I have shown the manually adjustable controls as including a control'knob 18 and a pair of push buttons 19 and 20 with suitable indicia 19a and 20a to indicate the respective functions of these push buttons. The function of these push buttons and of the control knob 18 will be better understood by a reference to' Fig. 4, presently to be described. A start button21 and appropriate index 22 is also mounted on the 'backsplash panel of the machine as shown.

'In Fig. 2, I have shown time and temperature curves determined from actual tests for loads of mixed nylons and rayons. Curve 23 shows characteristic operation for a load of four pounds; while curves 24 and 25 illustrate operation with six pounds and eight pounds respec tively. Superimposed upon these curves I have shown a line 26, which it is found may be a substantially straight temperature line intersecting each of the curves at a point where moisture retention is less than 10% of the dry clothes weight, that is a dry temperature line. A second straight line 27 has been superimposed upon this family of curves intersecting each curve at a point where moisture retention is in the range from 20% to 40% of the dry weight of the clothes. This latter is the so-called damp-dry range found to be most suitable when the clothes are'to be ironed before wear or before placing in storage. It is to be noted in connection withFig. 2 that both the dry and the damp-dry line are very nearly parallel.

Referring now to Fig. 3, a similar family of curves is shown for mixed cottons, curves 28, 28a, and 28b representing 4, 6, and 8 pound loads respectively. Again a straight line has been selected and is drawn in at 29 to intersect each of the curves at a point wherein moisture retention is less than 10%. A similar line 29a for the damp-dry range intersects each of the curves in the 20% to 40% range of moisture retention. As illustrated, these lines 29 and 29a may be selected to be substantially parallel while fulfilling the requirements as specified with respect to moisture retention. Also, it is to be noted that Figs. 2 and 3 are drawn on the same scale andthat the.lines 29 and 29a aresubstantially parallel to lines '26and 27. 'It is also significant to note in connection with Figs. 2 and 3 that the damp-dry lines 27 and 29a have not-only the .same slope, but also the same displace- .ment or relative position on the temperature-time diagrams. Thus, in accordance with the curves of Figs. 2

and 3, .a control for the damp-dry range is required to terminate dryer operation whenever the clothes temper- .vention to accomplish the desired results is shown by Fig.

4. As shown, the main heater 14 is arranged to be supplied with electrical power from supply lines L1 and L2,

for example representing a 220 volt source. A drive motor 30, functioning both to rotate basket 1 and to drive blower 10 is connected in the circuit to be supplied with electrical power from line .L1 to an electrical neutral, whereby the motor may be operated on 110 volts. Control of motor 30 and heater 14 is accomplished by a main line relay including a heater switch 31 and a motor switch 32. Both of these switches are biased to their normally open position by means such as a spring 33. The common operating shaft 34 for both switches is arranged to be operated by start button 21. A latching plate 35 secured to the operating shaft 34 cooperates with a latch 36 pivotally mounted behind backsplash panel 4 and connected by an operating rod 37 with a solenoid 38. This entire device including contacts 31 and 32 and the latching arrangement may behereinafter referred to as the latching relay. As clearly shown in Fig. 4, machine operation may be commenced by pressing start button 21, closing switches 31 and 32. These switches are maintained in their closed position by latch 36 and latching plate 35. However, if solenoid 38 is energized,

latch 36 is pivoted to a disengaged position, permitting spring 33 to openboth switches.

Solenoid 38 of the latching relay is under control of the temperature sensing device 17, previously referred to in connection with Fig. 1. Temperature sensing device 17 as shown by Fig. 4 includes a pair of thermostatic elements 39and 40. While these elements have been shown as the bimetallic type, obviously other types of thermostats might be employed, as-well as any other type of device producing a deflection responsiveto temperature.

Temperature sensing device 39 is positioned to sense predominantly the temperature of the exhaust air after it has passed through the tumbling basket. The temperature sensing device 40 on the other hand-has been inclosed within an insulating box 41, whereby it is sensitive primarily to the effects of a control heater 42 within box 41. Thermostat '40 is connected by a pin 43 slidable through the wall of "the box to operate a leaf-spring contact carrying member 44 externally of box 41. A cooperating contact is provided on thermostat 39.

The characteristics of thermostats 39 and 40 are so selected that they deflect oppositely and toward each other upon change in temperature. For example, in the specific arrangement shown in Fig. 4,'bimetallic element or thermostat 39 carried by an insulating block 45 deflects upwardly upon increasing temperature in the exhaust air stream. On-the other hand, temperature sensing device 40 is arranged'to deflect downwardly upon increasing temperature. Therefore, as the temperature in the exhaust stream rises, element 39 deflects upwardly, while element 40 influenced by its associated'heater deflects downwardly, to effect a closure of the contacts between element 44 and element 39. This temperature sensing switch thereby can complete a circuit commencing with line L1, through switch 31, conductors 46 and 47 to solenoid 38; the circuit continuing through conductor 48, the temperature sensing switch, and conductor 49 to the electrical neutral.

Since the temperature sensing member '39 is positioned within the exhaust air stream, it senses predominantly the'temperature of the clothes being dried, and hence has a temperature-time characteristic such as one of those illustrated by Figs. 2 and '3. The temperature sensing device 40 on the other hand is primarily influenced'by its associated heater 42, and the characteristics of this temperature sensing device and its heater are selected to produce a very rapid initial temperature increase, within the first few minutes of operation, with the subsequent increase in temperature as steady state conditions are approached being relatively slow and having a slope such that the downward deflection of the temperature sensing device'40 closely approximates the damp-dry line of Figs. 2 and 3. Thus, whenever the temperature. characteristic of thermostat 39 intersects the characteristic of thermostat 40, the contacts'on. element 39 and .spring blade 44 are closed, thereby energizing solenoid 38 to release the latch and permit the circuit through the main heating element and the main drive means to be opened.

As previously indicated, it is desirable for the dry range of operation to include within the control a means for shifting the displacement of the temperature-time characteristic of thermostatic element 40. This may be accomplished by Varying the heat input through the control heater 42. As shown in Fig. 4, from electrical supply conductor 46 and through a conductor 50, power is supplied to a pair of switches 51 and 52 adapted to be operated by push buttons "19 and 20 respectively. The operating shafts 53 and 54 forthese push button operated switches are interconnected by a link 55 pivoted intermediate its ends. Thus, upon closing movement of either switch, the opposite switch is moved to its open position. Damp dry push button 19 closes switch 51, whereby electrical power is conducted through a conductor 56 to a fixed portion 57 of a rheostat. The circuit is completed through a conductor 58 to control heater 42, and conductor 59 to the electrical neutral. Hence, whenever damp-dry switch 51 is closed control heater 42 is supplied with electrical power through a small portion of the current limiting resistance of the adjustable rheostat. The dry button 20 and its associated switch 52, however, completes a circuit through a conductor 60 to the adjustable contact member 61 of the rheostat. Therefore, a portion of the rheostat coil 62 is selected dependent upon the position of knob 18 and adjustable arm 61, the circuit again being completed to control heater 42 through conductors 5 8 and 59 to the electrical neutral. For a given load of clothes, the greater the resistance included in series with control heater 42 the longer will be the drying time. Hence, it is contemplated that control knob 18 or an index associated therewith may be calibrated in terms of the type of material being dried. For example, in the extreme counterclockwise position of the adjustable contact arm 61, control knob 18 should indicate that the machine is set for drying cottons, linens, and like fabrics. At the opposite or clockwise end of the scale of adjustment of knob 18, corresponding to minimum resistance in series with the control heater, will be designations for nylons and other synthetic fabrics.

A brief review of an operational cycle will further clarify the nature of the invention as illustrated. The articles to be dried are, of course, placed within basket 1. The operator then determines whether damp-dry operation or wholly dry operation is desired, making the proper selection by depressing button 19 or 20. Control knob 18 is also adjusted to select or dial the type fabric being dried. The machine does not commence operation, however, until start button 21 is depressed and latch plate 35 is secured under latch 36 with switches 31 and 32 closed. As explained, a circuit to the main heating element 14 is completed through relay or switch 31, while a circuit to the main drive source or motor 30' is completed through relay 32. Assuming first that the damp-dry button 19 has been depressed, power is supplied to control heater 42 through a circuit commencing with L1, and continuing through switch 31, conductors 46 and 50, damp-dry switch 51, conductor 56', segment 57 of the rheostat, conductor 58, the control heater, and

conductor 59 to the electrical neutral. Thus, the thermostatic element 40 through pin 43 deflects the resilient contact arm 44 downwardly, and after an initial warmup period occurring within a few minutes, the deflection of thermostatic element 40 continues as a function of time, closely approaching a straight line relationship. At

the same time, thermostatic element 39 is influenced by the increasing temperature of the exhaust air, which rises rapidly during a warm-up period and then at a decreased rate during moisture evaporation. Operation of the machine continues with bimetallic element 40 deflecting downwardly substantially linearly with respect to time, while bimetallic element 39 deflects upwardly following closely the temperature of the clothes with respect to time. As the movable contacts approach each other and eventually complete the circuit, latch solenoid 38 is energized, thereby to release latch 36 from latching plate 35 and terminate operation of the machine.

At the moment of termination of dryer operation as previously described, the contents may be uncomfortably hot. Therefore, for the safety and comfort of the operator, it is preferred in accordance with this arrangement to continue tumbling and air flow action for a short period of time following the opening of the latching relay. This may be accomplished as shown by Fig. 4 by means of an auxiliary circuit comprising a conductor 63, a thermostatic switch 64, and a conductor 65. Connected in parallel with the latching relay switch 32, the thermostatic switch 64 is arranged whereby its contacts are open when cool, and closed when hot. Thus, when the machine comes up to temperature, switch 64 closes, thereby completing an auxiliary circuit to drive motor 30, and this circuit remains closed at the end of the cycle when latching relay 32 opens. Therefore, the machine continues in operation for a short period of time without heater 14 being energized to permit a cooldown of the contents. As the machine cools, thermostatic switch 64 opens the circuit to motor 30.

In Fig. 5, I have shown a partial electrical diagram of an alternate arrangement of the adjustable rheostat. In this instance, the rheostat instead of being adjusted by a rotary member is in the form of a push button control. For simplicity, I have applied like reference numerals to corresponding parts, for example, 42 designates the control heater, shown in Fig. 4 as encircling the thermostatic element 40. As previously explained, electrical power may be supplied to the rheostat and control heater between conductors 60 and 59, clearly shown and explained above in connection with Fig. 4. In accordance with the Fig. 5 embodiment, the plurality of normally opened switches 6670 may be included in a control box 71 adapted to be mounted im mediately behind the backsplash panel of the machine. It is evident from an examination of the circuit of Fig. 5 that closure of switch 66 includes the maximum amount of resistance in series with control heater 42, thereby to select the maximum drying time for the machine; while closure of switch 70 inserts the minimum resistance in series with the control heater for minimum drying time. The intermediate switches, of course, select intermediate drying times. It is therefore contemplated that the arrangement of switches and series resistance shown by Fig. 5 may replace knob 18 and the resistance coil 62.

The switches 66-70 are adapted to be operated by a series of push buttons 72-76 respectively. In addition, a cancel or off button 77 is provided by which all of the switches 66-70 may be opened. As shown in Fig. 5, each of the push buttons is biased upwardly by means such as a spring 78 encircling an operating shaft 79. The lower end of each operating shaft 79 includes a cam operator 80 cooperating with a flexible arm of each switch in a manner closing the switch when the button is depressed. Any one of the push buttons may be held in a depressed position by a laterally movable latching bar 81 biased to its extreme right-hand position by a resilient means 82. This latching bar has a plurality of latching members 83, each arranged in cooperation with a switch operating rod 79. As clearly shown, each of the switch operating rods includes a projecting detent 84 adapted to engage underneath a corresponding latching member 83. Thus, when any push button is depressed, the switch associated therewith is cammed to its closed position and the push button is retained in its lower operated position by means of a latch 83 and associated detent 84. If, however, at any time a different push button is depressed, the latching bar 81 is cammed to the left, thereby releasing any button or buttons previously depressed. It is contemplated that the push buttons 7276 might be labeled with button 72 marked for linens, button '73 for cottons, button 74 for mixed cottons and linens, and'button 75 for synthetics, while button 76 could be used to select the damp-dry range for all fabrics.

From the above description, it can be seen that if the operator desires that the clothes be dried to the dampdry state ready for ironing, it is necessary merely to depress the damp-dry button and the machine automatically adjusts itself for the type load and weight of load, without judgment or any other type of adjustment on the part of the operator. If it is desired to completely dry a load, it is necessary merelyfor the operator to push a button or rotate a dial to the type fabric, such as nylons, cottons, linens, etc. Again the dryer automatically adjusts itself to the size load to operate the machine the necessary length of time for the completely dry condition. It is unnecessary for the operator to estimate the temperaturerequired or the necessary time of dryer operation, thus greatly facilitating the task, obviating operator errors, and greatly increasing the reliability of operation.

While this invention has been described by reference to particular embodiments thereof, it is to be understood that numerous modifications may be made by those skilled in the art without actually departing from the invention. It is therefore the aim in the appended claims to cover all such equivalent variations as come within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a clothes dryer of the type having heating means for drying the clothes placed therein, an automatic control comprising a pair of thermally sensitive members arranged to provide heat responsive relative deflections of said members in opposite directions, contact means closed by deflections of a predetermined amount, one of said members being primarily sensitive to interior dryer temperature produced by the clothes heating means, control heating means associated with the other of said members for causing the deflection thereof substantially independently of the interior dryer temperature, and an electrical control circuit rendered effective by closure of said contact means to terminate the operation of said heating means.

2. In a clothes dryer having heating means for drying the clothes placed therein, an automatic control comprising a pair of thermally sensitive members arranged with respective heat responsive deflections of said members in opposite directions, contact means closed by total deflection of a predetermined amount, one of said members being predominantly sensitive to interior dryer temperature produced by said heating means, adjustable control heating means associated with the other of said members for causing the deflection thereof, means rendering said other thermally sensitive member primarily sensitive to said control heating means, and an electrical control circuit rendered effective by closure of said contact means to terminate the operation of said heating means.

3. In a clothes dryer of the type having clothes heating means and drive means, an automatic control comprising a pair of thermally sensitive members arranged with respective heat responsive deflections in opposite directions and toward each other, switch means closed by said deflections of a predetermined total amplitude, one of said thermally sensitive members being primarily sensitive to the temperature of the articles being dried, control heating means associated with the other of said thermally sensitive members for causing the deflection thereof, means rendering said other thermally sensitive member primarily sensitive to said control heating means, adjustable means for regulating the quantity of heat supplied by said control heating means, and an electrical control circuit controlled by the closure of said switch means to terminate operation of said heating and drive means.

4. In a clothes dryer of the type having clothes heating means and drive means, an automatic control comprising a pair of thermally sensitive members having respective heat responsive deflections in opposite directions, switch means closed by a sum of said deflections of a predetermined amount, one of said thermally sensitivefmembers being primarily sensitive to the temperature of the articles being dried, control heating means associated with the other of said thermally sensitive members for causing the deflection thereof, means rendering said other thermally sensitive member primarily sensitive to said control heating means, adjustable means for regulating the quantity of heat supplied by said control heating means, an electrical control circuit rendered effective by closure of said contact means to terminate heater and drive means operation, and an auxiliary control circuit for said drive means including a thermostatic switch maintaining said drive means in operation until dryer temperature has decreased to a predetermined minimum,

5. An automatic control system for the clothes heating means of a clothes dryer comprising an electrical circuit for the clothes heating means, a control switch in said circuit having a normally open position and a latched closed position, electrically energized means for releasing said latch thereby to terminate heater operation, a first temperature sensing member exposed to dryer operating temperature and having a temperature responsive deflection in a first direction, a second temperature sensing member having a temperature responsive deflection in the opposite direction, a control circuit including contact means for said electrically energized means, said temperature sensing members operating upon temperature rise to close said contact means in said control circuit, and an electrical control heater associated with said second temperature sensing member for causing the deflection thereof substantially independently of dryer operating temperature.

6. An automatic control system for the clothes heat ing means of a clothes dryer comprising an electrical circuit for the clothes heating means, a control switch in said circuit having a normally open position and a latched closed position, means for moving said switch to said latched position, electrically energized means for releasing said latch thereby to terminate heater operation, a first temperature sensing member having a temperature responsive deflection in a first direction and primarily sensitive to dryer internal temperature, a second temperature sensing member having a temperature responsive deflection in the opposite direction and oriented in proximity to saidfirst temperature sensing member, a control circuit including contact means for said electrically energized means, said temperature sensing members operating upon temperature, rise to close said control circuit, an electrical control heater associated with said second temperature sensing member for causing the deflection thereof and to which said second temperature sensing member is predominantly responsive, and manually adjustable means for varying heat dissipation from said heater.

v7. In an automatic electrical clothes dryer having clothes heating means and drive means, an automatic control comprising electric circuit means including a latching relay to energize the heating and drive means, electrically operated tripping means to release said latching relay and terminate dryer operation, a pair of thermostatic members having cooperating heat responsive motions to energize said tripping means, one of said thermostatic members being sensitive primarily to interior dryer temperature, control heating means associated with the other of said thermostatic members for causing motion thereof and to which said other thermostatic membet is primarily sensitive, and adjustable means for varying the heat output of said control heating means to adapt the dryer to various drying loads.

8. In an automatic electric clothes dryer having clothes heating means and drive means, an automatic control comprising an electric circuit including a manually set latching relay to energize the heating and drive means, electrically operated tripping means to release said latching relay and terminate dryer operation, a pair of thermally sensitive members having cooperating heat responsive motions to energize said tripping means, one of said thermally sensitive members being sensitive primarily to interior dryer temperature, control heating means associated with the other of said thermally sensitive members for causing motion thereof and to which said other member is primarily sensitive, and an adjustable rheostat in series circuit relationship with the control heating means for varying the heat output of said control heating means to adapt the dryer to various drying loads.

9. In an automatic electric clothes dryer having clothes heating means and drive means, an automatic control comprising electric circuit means including a manually set latching relay to energize the heating and drive means, electrically operated tripping means to release said latching relay and terminate dryer operation, a pair of thermostatic members having cooperating heat responsive motions to energize said tripping means, one of said thermostatic members being sensitive primarily to interior dryer temperature, control heating means associated with the other of said thermostatic members for causing motion thereof and to which said other member is primarily sensitive, adjustable resistance means for varying the heat output of said control heating means to adapt the dryer to various drying loads, and manually operable means to select a fixed resistance for damp-dry operation.

10. In an automatic electric clothes dryer of the type having clothes heating means and drive means, an automatic control comprising a latching relay including an electric circuit to energize the heating and drive means, electrically operated tripping means to release said latching relay and terminate dryer operation, a pair of thermostatic members having cooperating heat responsive motions to energize said tripping means, one of said thermostats being sensitive primarily to clothes temperature, control heating means associated with the other of said thermostatic members for causing motion thereof and to which said other member is primarily sensitive, adjustable rheostat means for varying the heat output of said control heating means to adapt the dryer to various drying loads, and push button selector switch means for It) pre-selection of control heater bias thereby to select dryer operation dependent upon degree of dryness desired and type of load.

11. In a clothes dryer having a drying chamber and primary heating means therefor, an automatic control for said heating means comprising a pair of thermally sensitive members arranged to deflect relatively to each other in response to temperature changes, one of said members being predominantly sensitive to the temperature of said chamber, and the other of said members having associated therewith local heating means for causing the deflection thereof and to which said other member is predominantly sensitive, and a control member for said heating means for shutting ofi said primary heating means in response to the total relative deflection of said members efiected by the operation of said local heating means and the high temperature condition obtained in said chamber.

12. In a clothes dryer having a drying chamber and a primary heating means therefor, an automatic control for said heating means comprising a thermally sensitive control switch having a local heating means, said switch responding jointly to the time interval heat is supplied by said local heating means and to the temperature condition in said chamber to move to a controlling position, and a control circuit for said primary heating means controlled by said switch to terminate the operation of said primary heating means when said switch moves to said controlling position.

13. In a clothes dryer having a drying chamber and a primary heating means therefor, an automatic control for said primary heating means comprising a control switch, means responsive to the temperature in said drying chamber for moving said control switch toward an actuated position, time responsive means for simultaneously moving said control switch toward an actuated position as a function of the elapsed time of operation of said primary heating means, and a control circuit for said primary heating means rendered efiective to terminate the operation of said primary heating means upon actuation of said control switch.

References Cited in the file of this patent UNITED STATES PATENTS 1,707,547 Adams Apr. 2, 1929 2,052,536 Shivers Aug. 25, 1936 2,300,418 Hall Nov. 3, 1942 2,398,880 Broglie Apr. 23, 1946 2,463,934 Allen Mar. 8, 1949 2,743,531 Steward May 1, 1956

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