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Publication numberUS3205590 A
Publication typeGrant
Publication date14 Sep 1965
Filing date23 Feb 1962
Priority date23 Feb 1962
Publication numberUS 3205590 A, US 3205590A, US-A-3205590, US3205590 A, US3205590A
InventorsDeaton Homer W
Original AssigneeGen Motors Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Humidity responsive dryer control
US 3205590 A
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Description  (OCR text may contain errors)

Sept. 14, 1965 H. w. DEATON HUMIDITY RESPONSIVE DRYER CONTROL 2 Sheets-Sheet 1 Filed Feb. 23 1962 INVENTOR. Home) dd Dea f0)? 2 m H15 ATTORNEY United States Patent 3,205,590 HUMlDITY RESPQNSVE DRYER CONTROL Homer W. Deaton, Dayton, ()hio, assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Filed Feb. 23, 1962, Ser. No. 175,071 8 Claims. (Cl. 34-45) This invention relates generally to an improved power termination control circuit and more particularly to a point relative humidity.

In the clothes drying art, it has been recognized that different fabric loads (size and type) have different drying characteristics when considering dryer exhaust air humidity versus time for drying. Therefore, any device which automatically terminates a drying cycle on exhaust humidity alone cannot produce consistent drying results when the load varies both as to size and character of fabric. Note has been taken of the fact that the relative humidity of the outlet or exhaust air drops as the temperature thereof rises. Using this fact, this invention is directed to a control circuit which progressively lowers the humidity control point at which the drying cycle will terminate. Thus, this invention recognizes that smaller loads and lighter fabrics are properly dry at lower exhaust air relative humidity readings.

Accordingly, it is an object of this invention to provide a dryer termination control circuit equally effective in terminating the drying cycle of small or large loads of different fabrics.

Another object of this invention is the provision of a dryer termination control which is effective to select the control termination point in accordance with the type of load being dried.

A more specific object of this invention is the provision of a humidity element controlled dryer termination control in which the relative humidity termination point is continuously reduced whenever the sensible temperature of the dryer exhaust exceeds a predetermined value to indicate the load is approaching a dry condition.

Another object of this invention is the provision of an amplifier for a dryer control for terminating the drying cycle, said amplifier being actuated by a voltage divider circuit including a humidity sensing element responsive to the dryer exhaust air and a variable resistance element which is continuously mechanically increased to lower the relative humidity control point at which the exhaust air at the sensing element would be effective to terminate the drying cycle.

Another object of this invention is the provision of an improved amplifier in a dryer control which includes relay coil winding in parallel with a transistor-the transistor being selectively operated by a voltage divider circuit having a humidity sensing element and a variable resistance.

A more general object of this invention is the provision of a relay control circuit having a relay coil winding in parallel with a transistor or semiconductor switch means.

Another object of this invention is the provision of a. control for a power supply including a circuit having a relay coil actuatable for connecting and disconnecting the circuit from said power supply, a transistor in parallel with said coil and a voltage divider circuit in parallel with said coil and connected to said transistor for biasing said transistor to actuate said coil.

Another object of this invention is provision of a voltage divider circuit in a clothes dryer control, said voltage divider circuit including a variable resistance which is progressively increased throughout the drying cycle to change the point at which the drying cycle is terminated.

Further objects and advantages of the present inven- Patented Sept. 14, 1965 "ice tion will be apparent from the following description, reference being had to the accompanying drawings wherein preferred embodiments of the present invention are clearly shown.

in the drawings:

FIGURE 1 is a cross-sectional view of a clothes dryer suitable for use with this invention;

FIGURE 2 is a schematic wiring diagram of the control circuit of this invention; and

FIGURE 3 is a graph of relative humidity versus time for the last part of a clothes drying cycle controlled in accordance with the teachings of this invention.

In accordance with this invention and with reference to FIGURE 1, a clothes dryer 10 is illustrated. The dryor includes a front wall 12, a rear wall 14 and a top panel 16 having a control console 18 at the rear thereof. The walls 12, 14 and 16 partially form a casing for enclosing a tumbling drum 20 which is journaled in a bearing 22 carried by a rear bulkhead 24. The tumbling drum 20 has a perforated rear wall 26 and a flanged collar 28 which surrounds an inwardly directed collar 30 on a front port plate 32. The front port plate 32 is fixed to a recessed shoulder 34 in the front wall 12 of the dryer cabinet. Thus, the port plate 32 and its integral collar 30 form the access passage for placing clothes within the tumbling drum 20.

A door 36 is hingedly mounted on the front wall of the dryer and carries a lint collecting housing 38 which nests within the port plate 32 in sealing engagement thereto when the door is closed. The lint collecting housing carries a lint collecting screen 40 which is interposed between the perforations -42 of the lint collector housing 38 on one side of the screen 40 and an outlet passage 44 on the other side of the housing. The port plate 32 carries an arcuate series of ports 46 at its lower edge which directs air into a front duct 48 leading to a blower 50 within the dryer cabinet. This blower 50 exhausts the air to the atmosphere through a duct 74. Between the front duct 48 and the blower 50 is a control conduit 52 in which a humidity sensing element or sensor 54 resides. An amplifier 56 in the dryer console is electrically connected to the sensor 54 and adapted to signal the end of the automatic drying cycle. A heater 60 is included in the annular space between the bulkhead 24 and the perforated rear wall 26 of the tumbling drum. A motor 62 is positioned in the lower part of the dryer casing and adapted to drive the blower 50 and rotate the tumbling drum 20 through a conventional pulley and belt arrangement 64.

Air flow through the tumbling drum 20 for drying the clothes is thus afforded as follows. Air enters the back wall 14 of the dryer casing through openings, such as 66 and 68. The air is drawn through the perforations 70 of the rear bulkhead 24 and across the heating element 60 into the tumbling drum 20. Air leaving the tumbling drum after vaporizing moisture from the clothes enters the lint collecting housing 38 through the perforations 42 thereof and has the lint filtered therefrom by the screen 40. This exhaust air flowing from the tumbling drum by way of the front duct 48 and the conduit 52 passes the humidity sensing element 54 prior to its being exhausted through the outlet duct 74 to the atmosphere. This invention is directed to a control for terminating the drying cycle in the dryer describer hereinabove.

The control circuit is best seen in FIGURE 2 and includes a push-actuated start button 76 in an accessible location such as on the control console of the dryer. The start button '76 is depressed momentarily to energize a holding circuit which includes a holding relay coil 78 and a switch 80 actuated by the holding coil. A delay means may be provided for the push button 76 to prevent 3 its opening before moisture is reflected at the sensing element 54 in the dryer exhaust. It should be recognized, however, that .a more sensitive sensing element 54 will preclude the necessity for this time delay in the start switch.

The dryer termination control includes an improved amplifier 56 having a direct current relay coil or winding 82 for actuating a switch 84 in series with the holding circuit coil 78. The switch 84 is norm-ally open and is closable so long as the relay coil 82 is energized. By-passing the relay coil 82 is a transistor 86 having its emitter 88 connected to one side of the coil 82, and its collector 90 connected to the other side of the relay coil. Since the relay coil 82 is actuatable by direct current, a diode 92 is included in parallel relationship with the coil to pass current in one direction only. A capacitor 94 may also be included for relays which have a tendency to hum when used on AC. or pulsating D.C. A resistance 96, in series with the relay coil 82, must be small enough to permit the energization of the coil 82 with the available power supply. Grouping the foregoing components, the only electrical connections to the amplifier 56 are a conductor 98 to one side of the domestic 115 v.230 v. power supply line L and a conductor 100 to the neutral side of the line N. The base connection 102 for the transistor 86 extends out of the amplifier 56 and is connected to a voltage divide-r circuit which includes the humidity sensing element 54 and a motorized resistance unit 104 in juxtaposition to the amplifier in the console. The unit 104 ha a variable resistance 108 and a positioning motor 106 which is thermally responsively energizable for progressively increasing the resistance 108. Since the resistance 108 is gradually and progressively increased during the drying cycle whenever the motor 106 is energized, a mechanical connection (shown schematically at 110) is provided between the positioning motor shaft and the start button 76 so that the variable resistance 108 may be mechanically repositioned to its lowest value each time a new drying cycle is initiated.

The resistances 108 and 54 in the voltage divider circuit are proportioned such that the resistance 108 is much larger, on the order of 100 to 1, than the sensing element resistance 54. Insofar as the voltage divider circuit is concerned, therefore, when the motor 106 runs, the increase in resistance 108 tends to cancel out or offset a portion of the increased voltage drop across the sensor 54 due to the drying of the clothes load (resistance 54 increases as the clothes become dry). The partial offsetting action tends to delay the point at which a ufficient voltage potential exists, base 102 to emitter 88, to fire the transistor 86 and terminate the drying cycle. In effect, the gradually increasing resistance 108 acts to continually decrease the percent relative humidity requirement of the exhaust air necessary to terminate the drying cycle.

Referring now to FIGURES 1 and 2, the dryer control circuit includes such normal safety feature as a high limit thermostat 112 which opens upon an abnormal rise in temperature within the heater chamber and a motor switch 114 which is closed by a centrifugally actuated mechanism (not shown) in the main motor 62 to insure that the heater 60 will not be energized unless the motor 62 is operating to rotate the tumbling drum 20. In addition to the safety controls, thi circuit includes a termination conrol thermostat 116 responsive to the temperature of air leaving the tumbling drum. The thermostat 116 has a switch blade 118 which closes on a heater circuit contact 120 when the temperature of the exhaust air is between and 140 F. or below. Above this predetermined temperature range, the switch blade moves to the contact 122 in which position it energizes the positioning motor 106 to increase the resistance 108 in the voltage divider circuit. Note that the termination control thermostat 116 is first moved to its positioning motor contact 122 when the sensible temperature of the exhaust air increases suddenly over the said predetermined temperature range. This generally occurs when the clothing is reaching a dry condition as reflected by the moisture content of the dryer exhaust air. This dry bulb temperature jump has been used repeatedly in prior art devices to terminate the drying cycle. However, such prior art systems fail to cornpensate for the occasional or LIGHT loads, such as a shag rug or four to five pound of assorted clothing and hardto-dry items wherein fabric seams resist giving up moisture evenly. in these LIGHT loads, the point at which the sensible temperature jumps above the predetermined temperature range is in advance of the proper dryness end point for the clothes load and, thus, this invention seeks to prolong the cycle by operating the motor 106 to gradually reduce the percent relative humidity at which the cycle will terminate. As has been explained hereinbefore, this is accomplished by increasing the resistance 108 in the voltage divider circuit to delay the point at which the humidity sensing element 54 is effective to bias transistor 86 to by-pass the power and shunt the termination relay coil 82.

An operating drying cycle will be explained with reference to the control circuit of FIGURE 2 and the graph in FIGURE 3. Note that the graph in FIGURE 3 takes into account only the last portion of the drying cycle which shows the manner in which the various type loads terminate. Consider first a NORMAL eight pound load which is placed in the tumbling drum 20 and the dryer energized by pushing the button 76. At the start, the temperature in the tumbling drum is below 130 F. and the thermostat 116 is positioned to energize the heater 6i) and the prime mover or main motor 62. The amplifier 56 is actuatable by humidity sensed by the sensing element 54 in the exhaust duct 52. It is possible that the system may terminate the NORMAL or regular eight pound load cycle before the motor 106 is even ener"izedassuming that the sensor 54 fired the transistor 86 in advance of the point at which the sensible temperature jumps to actuate the thermostat 116. In this situation, the NORMAL drying cycle will terminate when the resistance of the element 54 is increased to the point at which the transistor 86 is biased to shunt the power from the relay coil 82 to cause the switch 84 to open. However, most loads do ermit the temperature to increase enough to actuate the thermostat 116 and run the positioning motor 106 some. In graphic form, this more usual condition is represented by curve 136 which is shown dropping 01f to about to 35% R.H. marl; at which point 138 the relay coil 82 is deenergized and the cycle terminated before the clothes are overdried. Thus, at point 138 a NGRMAL eight pound load of clothes i dry when the resistance of the sensor 54 increases to create a volt-age at the base 102 which will fire the transistor.

Let us assume now that a LIGHT load, such as a shag rug or a small load (under five pounds) of light fabrics, is being dried. The moisture Will be very quickly vaporized from the exposed fabric surface in the LIGHT load. However, in the depths of the shag rug and in the folds and seams of the light fabrics, the moisture will still be retained so that an exhaust air indication of thirty-fivepercent relative humidity would be a premature indication that the load is dry. Consequently, and in accordance with this invention, when the sensible temperature first jumps and moves above the predetermined setting of thermostat 116, say 140 F., the switch blade 118 will move to the contact 122 to energize the positioning motor 1116. The motor then starts to gradually increase the resistance 10% to hold off the point at which the sensing element 54 would normally fire the transistor 86 to terminate the drying cycle. This, in effect, lowers the relative humidity setting which is necessary to terminate the drying cycle.

A load controlled in accordance with this invention would exhibit three curves of interest. The drying rates of a typical LIGHT load and NORMAL load are evidenced on the drying curves 140 and respectively, and the rate of depressing termination point relative humidity is shown by the control curve 142. The respective drying cycle will terminate where the drying curves intersect with the control curves-a variable end point depending on the number of times that the thermostat 116 energizes or cycles the control motor 106 while the load is drying. Therefore, the more frequently that thermostat 116 energizes the motor 106 the more prolonged will be the drying cycle. Thus, it can be seen that the drying of a NORMAL eight pound load may be terminated at point 138 (35% RH), whereas the drying of the particular LIGHT load evidenced by the curve 140 is terminated at point 144 RH). The more gradual the slope of the drying curve 140 (i.e. the greater the affinity of the load to retain its moisture), the longer will be the total cycle time and the lower will be the percent R.H. of the exhaust air when the clothes have reached their proper dryness condition. In short, the positioning motor 106 operates solely to adjust the amplifier 56 to terminate the drying cycle at a lower percent R.H. A detailed description of the improved amplifier 56 will be described next following. It should be recognized, however, that any conventional amplifier could be substituted for the improved amplifier within the purview of this invention.

The transistorized humidity element amplifier 56 is used in conjunction with the above dryer control. This amplifier has the advantages of transistor reliability and the novel circuit in which the elements of the amplifier are arranged circumvents the disadvantages of transistors, i.e. low input impedance, because the transistor is looking at a constant input current or high voltage source. In other words, the voltage across the potentiometer or variable resistance 108 is a constant 115 voltsa fact which permits a small increase in relative humidity seen at the sensor 54 to actuate the transistor by a biasing con nection 102 between the two resistances 108 and 54. The amplifier 56 is comprised of the solenoid or relay actuating coil 82 for actuating a normally open switch 84 in the drying cycle start circuit. Whenever the coil 82 is deenergized, the switch 84 opens to deenergize the coil 78 and the drying cycle is thus terminated. For controlling the coil 82, the amplifier 56 further includes the capacitor 94, the diode 92, a resistance 96 small enough to permit energization of the relay coil 82 and a transistor 86 having the integral components of collector 90, emitter 88 and the base leg 102.

In operation, the amplifier 56 is connected across the leads L and N of a 115 volt alternating current power source and functions as follows at the start of a drying cycle. When the push button 76 is depressed, the positive half of the AC. sine wave will move from L through the diode 92, thereby by-passing the relay coil 82 to the neutral side of the line. On the next half A.C. sine wave, power flow in the negative direction from N to L will energize the solenoid coil 82 to close the switch 84. The capacitor 94 is charged and the transistor 86 is inactive due to low humidity at the element 54. In the next positive half wave from L to N, the capacitor 94 discharges to maintain the relay coil 82 energized while the diode 92 by-passes the coil. Thus, the coil 82 remains energized in one direction by the half wave flow from N to L and in the other direction by the discharge of the capacitor 94. This situation maintains throughout the clothes drying cycle since the predetermined voltage to actuate or fire the transistor 86 is not being applied at the biasing leg 102. However, as the cycle progresses, considering the shag rug or LIGHT load characteristic, the resistance 108 is increased whenever the motor 106 is energized. At a certain point, the voltage applied at 102 through the voltage divider circuit including the thermally responsively variable resistance 108 and the humidity responsive variable resistance 54 will be effective to fire the transistor 86. When this happens, the capacitor 94 will discharge through the transistor 86 instead of the coil 82 and the switch 84 will open. When switch 84 opens, the holding relay coil 78 is deenergized and switch 80 opens to terminate the drying cycle.

It should now be seen that an improved clothes dryer termination control has been provided wherein a variable end point dryness is effected to accommodate light loads of light fabrics or loads of heavy deep pile material, such as a shag rug. Further, this invention includes a novel transistorized amplifier wherein the relay coil is placed in parallel with the transistor and fed from a line voltage source rather than a transformer as in the prior art. This improved amplifier circuit overcomes the problem of matching impedances of the humidity sensing element and the transistor. It also eliminates the need for a rectifier circuit since the circuit provides its own DC. power supply.

While the embodiments of the present invention as herein disclosed constitute preferred forms, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. In combination, a clothes dryer having means for conveying a stream of air into moisture absorbing relationship with said clothes in a clothes drying cycle, means for heating said stream of air, control means for energizing or deenergizing said heating means in response to the temperature of said air, switch means for initiating and terminating said cycle, and voltage divider circuit means for controlling said switch means, said circuit means including first resistance means, the resistance of which increases in response to the decreasing relative humidity of said air as said clothes approach a dry condition for terminating said cycle when a predetermined resistance value is attained and second resistance means in resistance comparing relationship to said first resistance means, means connected to said second resistance means and actuatable for increasing the resistance thereof for at least partially balancing said first resistance means whenever said control means is deenergizing said heating means, thereby to increase said predetermined resistance value and extend said clothes drying cycle.

2. In combination with a clothes dryer having means for conveying a stream of air into moisture absorbing contact with said clothes, termination control circuit means comprising a pair of lead wires connected across a source of voltage, one of said lead wires including a power termination switch means operable to connect and disconnect said one of said lead wires from said source of voltage, a first circuit connected across said lead wires including a relay coil winding, said power termination switch means operating to connect and disconnect said one of said leads from said source of power in response to the actuation of said relay coil winding, a second circuit connected across said lead wires for by-passing said relay coil winding and including a semiconductor switch means, a third circuit connected across said lead wires for by-passing said relay coil winding and said semiconductor switch means and including first and second resistance elements, and means connected to said third circuit between said resistance elements and associated with said semiconductor switch means for controlling the lay-passing of said relay coil winding, thereby to operate said power termination switch means, said first resistance element being in humidity responsive relationship to said stream of air downstream from said clothes, means connected to said sec-0nd resistance element and actuatable for increasing the resistance thereof, and means in thermally responsive relationship to said stream of air downstream from said clothes for actuating said last named means.

3. In combination with a clothes dryer having means for conveying a stream of air into moisture absorbing contact with said clothes, termination control circuit comprising a pair of lead Wires connected across a source of voltage, one of said lead wires including a power termination switch means operable to connect and disconnect said one of said lead Wires from said source of voltage, a first circuit connected across said lead wires including a relay coil winding, said power termination switch means operating to connect and disconnect said one of said leads from said source of power in response to the actuation of said relay coil winding, a second circuit connected across said lead wires for by-passing said relay coil winding and including a semiconductor switch means, a third circuit connected across said lead wires for bypassing said relay coil winding and said semiconductor switch means and including first and second resistance elements, and means connected to said third circuit between said resistance elements and associated with said semiconductor switch means for controlling the by-passing of said relay coil winding, thereby to operate said power termination switch means, said first resistance element being in humidity responsive relationship to said stream of air downstream from said clothes, means connected to said second desistance element and actuatable for increasing the resistance thereof, and means in thermally responsive relationship to said stream of air downstream from said clothes for actuating said last named means to increase the resistance of said second resistance element when the temperature of said stream of air is above a predetermined value.

4. A drying cycle termination control circuit for a clothes dryer having means for conveying a stream of air into moisture absorbing contact with said clothes comprising a pair of lead wires connected across a source of Voltage, one of said lead wires including a power termination switch means operable to connect and disconnect said one of said lead wires from said source of voltage, a first circuit connected across said lead wires including a relay coil winding, said power termination switch means operating to connect and disconnect said one of said leads from said source of power in response to the actuation of said relay coil winding, amplifier means for selectively actuating said relay coil winding, a third circuit connected across said lead wires for by-passing said relay coil winding and said amplifier means and including rst and second resistance elements, and means connected to said third circuit between said resistance elements and associated with said amplifier means for controlling the bypassing of said relay coil winding, thereby to operate said power termination switch means, said first resistance element adapted to be in humidity responsive relationship to said stream of air downstream from said clothes, means connected to said second resistance element and actuatable for increasing the resistance thereof, and means adapted to be in thermally responsive relationship to said stream of air downstream from said clothes for actuating said last named means to increase the resistance of said second resistance element, thereby to extend the drying cycle.

5. A drying cycle termination control circuit for a clothes dryer having means for conveying a stream of air into moisture absorbing contact with said clothes comprising a pair of lead wires connected across a source of voltage, one of said lead wires including a power termination switch means operable to connect and disconnect said one of said lead wires fnom said source of voltage, a first circuit connected across said lead wires including a relay coil winding, said power termination switch means operating to connect and disconnect said one of said leads from said source of power in response to the actuation of said relay coil winding, amplifier means for selectively actuating said relay coil winding, a third circuit connected across said lead wires for bypassing said relay coil Winding and said amplifier means and including first and second resistance elements, and means connected to said third circuit between said resistance elements and associated with said amplifier means for controlling the by-passing of said relay coil winding, thereby to operate said power termination switch means, said first resistance element being in humidity responsive relationship to said stream of air downstream from said clothes, means connected to said second resistance element and actuatable for increasing the resistance thereof, and means in thermally responsive relationship to said stream of air downstream from said clothes for actuating said last named means to increase the resistance of said second resistance element when the temperature of said stream of air is above a predetermined value, thereby to extend the drying cycle.

6. A power termination control circuit comprising a pair of lead wires connected across a source of voltage, one of said lead wires including a power termination switch means operable to connect and disconnect said one of said lead wires from said source of voltage, a first circuit connected across said lead wires including a relay coil winding, said power termination switch means operating to connect and disconnect said one of said leads from said source of power in response to the actuation of said relay coil winding, 2. second circuit connected across said lead wires for by-passing said relay coil winding and including a semiconductor switch means, a voltage divider circuit connected across said lead wires for bypassing said relay coil winding and said semiconductor switch means and including first and second resistance elements, and means connected to said third circuit between said resistance elements and associated with said semiconductor switch means for controlling the by-passing of said relay coil winding, thereby to operate said power termination switch means; one of said resistance elements being responsive to a first condition to actuate said controlling means and the other of said resistance elements being increasable in resistance to alter the actuation of the controlling means by changing said first condition, means connected to said second resistance element and actuatable for increasing the resistance thereof, and means responsive to a second condition for actuating said last named means.

7. In combination with air impelling means for producing an air stream subjected to variable conditions of temperature and humidity power termination control circuit comprising a source of voltage for selectively energizing said air impelling means, a pair of lead wires connected across said source of voltage, one of said lead wires connectable to said air impelling means and including a power termination switch means operable to connect and disconnect said one of said lead wires from said source of voltage to energize and deenergize said air impelling means, a first circuit connected across said lead wires including a relay coil winding, said power termination switch means operating to connect and disconnect said one of said leads from said source of power in response to the actuation of said relay coil winding, a second circuit connected across said lead wires for by-passing said relay coil winding and including a semiconductor switch means, a third circuit connected across said lead wires for by-passing said relay coil winding and said semiconductor switch means and including a first resistance element in humidity responsive relationship to said air stream and a second resistance element, means actuatable for progressively increasing the resistance of said second resistance element, means in thermally responsive relationship to said air stream actuating said last named means, and means connected to said third circuit between said resistance elements and associated with said semiconductor switch means for controlling the by-passing of said relay coil winding, thereby to operate said power termination switch means.

8. In combination with air impelling means for producing an air stream and means for subjecting said air stream to variable conditions of temperature and humidity, power termination control circuit means comprising a source of voltage for selectively energizing said air impelling means and said subjecting means, a pair of lead wires connected across said source of voltage, one of said lead wires connectable to said air impelling means and said subjecting means and including a power termination switch means operable to connect and disconnect said one of said lead wires from said source of voltage to energize and deenergize said air impelling means and said subjecting means, a first circuit connected across said lead wires including a relay coil winding, said power termination switch means operating to connect and disconnect said one of said leads from said source of power in response to the actuation of said relay coil winding, a second circuit connected across said lead Wires for bypassing said relay coil winding and including amplifier means, a third circuit connected across said lead Wires for by-passing said relay coil winding and said amplifier means and including a first resistance element in humidity responsive relationship to said air stream and a second resistance element, means for progressively increasing said second resistance including means in thermally responsive relationship to said air stream, said thermally responsive means connected to said one of said lead wires and having a first position for increasing said second resistance and a second position for energizing said subjecting means, and means connected to said third circuit References Cited by the Examiner UNITED STATES PATENTS 2,820,304 1/58 Horecky 3445 2,828,450 3 5 8 Pinckaers.

2,878,580 3/59 Hughes 34-45 2,895,230 7/59 Reiley 3445 2,991,653 7/61 Thompson.

3,014,159 12/61 Frank 317--148.5 X 3,032,690 5/62 Elliot 317-148.5 X 3,073,244 1/63 Elliot 317148.5 X

NORMAN YUDKOFF, Primary Examiner.

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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3445676 *21 Feb 196720 May 1969Controls Co Of AmericaMoisture sensing control circuit detecting reversed polarity of power supply
US4268247 *24 May 197919 May 1981Challenge-Cook Bros., IncorporatedMethod for drying fabrics
US8015726 *24 Oct 200513 Sep 2011Whirlpool CorporationAutomatic clothes dryer
US8629377 *19 May 200814 Jan 2014Mabe Canada Inc.Heater assembly for clothes dryer
US20090020520 *19 May 200822 Jan 2009Mabe Canada Inc.Heater assembly
US20120263444 *15 Apr 201118 Oct 2012Tutco, Inc.Electric resistance heater assembly and method of use
Classifications
U.S. Classification34/527, 432/37, 432/43, 219/519, 361/178, 219/501
International ClassificationG05D22/00, D06F58/28, G05D22/02
Cooperative ClassificationD06F58/28, G05D22/02
European ClassificationG05D22/02, D06F58/28