US3218730A

US3218730A - Termination control for a condensing clothes dryer

Info

Publication number: US3218730A
Application number: US202486A
Authority: US
Inventors: Melvin A Menk; James L Miller
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1962-06-14
Filing date: 1962-06-14
Publication date: 1965-11-23
Anticipated expiration: 1982-11-23

Description

Nov. 23, 1965 M. A. MENK ETAL 3,218,730

TERMINATION CONTROL FOR A CONDENSING CLOTHES DRYER Filed June 14, 1962 4 Sheets-Sheet 1 r INVENTORS m N Melvin A. Menk BY James L. Miller Their Attorney Nov. 23, 1965 A. MENK ETAL 3,218,730

TERMINATION CONTROL FOR A CONDENSING CLOTHES DRYER Filed June 14, 1962 4 Sheets-Sheet 2 INVENTORS. Melvin A. Menk Y James L. Miller Nov. 23, 1965 M. A. MENK ETAL 3,218,730

' TERMINATION CONTROL FOR A CONDENSING CLOTHES DRYER Filed June 14, 1962 4 Sheets-Sheet s 95 I66 .Q I74 5 2o- 54 470 Timed Peroid /1 I58 Pause Peroid I I 50 I00 I50 200 250 300 Temperature F F jg 5 Time Advancement Switch Aufomuflc Cycle Off 100 J I04 mg f cool I Delicate R g off Starr Start laz INVENTORS Fig 4 Melvin A. M

BY James L. Miller 7' I; air A fforney Nov. 23, 1965 M. A. MENK ETAL 3,218,730

TERMINATION CONTROL FOR A GONDENSING CLOTHES DRYER Filed June 14, 1962 4 Sheets-Sheet 4 3o- '98 Fig. av

I I96 I94 E l5 @K Timed Peroid I90 Pause Peroid lll lll|l|filllllllllllll T empera/ure "F s 230 W/l/l/l/l/l/l/l/ k\\\ Timed Peroid E Pause Peroid E i: I5-

Fig. 7 INVENTORJ.

Melvin A. Menk James L. Miller Tlll'lllll ||ll |l||| BY 50 I00 I50 200 250 300 Tem era/ure "F p Their Attorney United States Patent Office 3,218,730 Patented Nov. 23, 1965 3,218,730 TERMINATION CONTROL FOR A CONDENSING CLOTHES DRYER Melvin A. Menk and James L. Miller, Dayton, Ohio,

assignors to General Motors Corporation, Detroit,

Mich., a corporation of Delaware Filed June 14, 1962, Ser. No. 202,486 12 Claims. (CI. 3445) This invention relates to a domestic appliance and more particularly to an improved control arrangement for terminating a clothes drying cycle.

The clothes drying art has been faced with the disadvantage of venting the moisture laden exhaust products from a dryer to the outside atmosphere. For those situations where construction or other problems prevent outside venting, a condensing clothes dryer has been provided of the type taught generally in the patent to Whyte et al. 3,032,887, issued May 8, 1962. The condensing dryer includes a recirculating drying air flow system for picking up moisture from the clothes and a condensing means such as a cooling air fiow system which blows in counterflow heat transfer relationship to the recirculating air. Thus, the recirculating air picks up moisture in the tumbling drum and, while passing through the condenser, is cooled by the cooling air flow system to release the entrained moisture as condensate.

Various controls have been used with condensing dryers to automatically terminate the drying cycle and it is to an improved control for this result that this invention is directed.

Accordingly, it is an object of this invention to terminate the drying cycle of a condensing dryer automatically.

Another object of this invention is the provision of a control for a condensing dryer which uses the temperature of the heated inlet air to terminate the drying cycle.

A more specific object of this invention is the provision of a control which includes a drying cycle termination thermostat in the heater chamber ahead of the tumbling drum to operate a timer motor, a drying temperature control thermostat in the exhaust air from the tumbling drum having an ON position for energizing the heater and an OFF position in series with said drying cycle termination thermostat, said drying cycle termination thermostat acting to terminate the drying cycle by continuously operating the timer motor when the heater is deenergized and the temperature of the air in the heater chamber falls below a predetermined value.

Another object of this invention is the provision of a drying cycle termination control having a preset temperature for terminating the drying cycle of regular fabrics at one temperature, a cycling control for regulating the temperature during drying and means 'for relating said termination control to said cycling control for terminating the drying cycle of delicate fabrics at a temperature different from said preset temperature.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

FIGURE 1 is a fragmentary perspective view of a condensing dryer with parts broken away to show a recirculating air flow system and a cooling air flow system suitable for use with this invention;

FIGURE 2 is a schematic representation of the condensing dryer detailed in FIGURE 1;

FIGURE 3 is a schematic wiring diagram of the inlet air temperature termination control of this invention;

FIGURE 4 is a timer cycle chart showing the positions of the timer switches in FIGURE 3;

FIGURE 5 is a graphic representation of a REGULAR load of clothes (cottons, linens, etc.) being automatically dried in accordance with the teachings of this invention;

FIGURE 6 is a graphic representation similar to FIG- URE 5 for a six pound DELICATE load of clothes (man made fabrics such as nylon, Acrilon, etc.); and

FIGURE 7 is a graphic representation for a two pound DELICATE load.

In accordance with this invention and with reference to FIGURE 1, a condensing type clothes dryer 10 is illustrated. The clothes dryer 10 is comprised of an enclosing casing on the top of which is a control housing 18. The housing 18 supports a control knob 14 which may be selectively positioned for initiating and controlling the drying cycle in accordance with the teachings of this invention and a knob 16 for setting the type of fabric to be dried and thus the temperature to be maintained during the drying cycle. A tumbling drum 20 is disposed within the casing and interposed between a front bulkhead 22 and a rear bulkhead 24. The tumbling drum 20 is comprised of a perforated rear wall 26 which is rotatably supported on a stub shaft 28 journalled on the rear bulkhead 24. Further, the tumbling drum 20 includes a cylindrical access collar 32 which is relatively rotatably supported by a front port blade 34 carried on the front bulkhead 22. The access opening formed by the collar 32 is closed by a door shown at 36. On the door is a lint collecting housing 38 which projects into the access opening collar 32 of the tumbling drum when the door is closed, an annular seal 37 engaging the port plate to force all air leaving the tumbling drum to travel through the lint collecting housing.

The recirculating air flow system is defined by perforations 40 in the front port plate 34 which open into a front duct 42. This front duct opens into an inlet header 46 for a heat exchanger or condenser, shown generally at 48. The condenser 48 is comprised of a plurality of slightly leftwardly sloping tubes 50 which interconnect the inlet header 46 with an outlet header 52. A recirculating air blower 54 has its inlet 56 connected to the outlet of the outlet header 52 and impels air through a flexible conduit 58 to a rear duct 60 behind the rear bulkhead 24. The rear duct has an opening 62 through the rear bulkhead 24 into an annular chamber formed by a generally channel-shaped annular pan 64 fastened to the front side of the bulkhead 24. The annular channel or heater housing provides the means for enclosing and supporting the annular heating elements 66 in juxtaposition to the perforated rear wall 26 of the tumbling drum.

Thus, recirculating drying air is impelled by the blower 54 through the flexible conduit 58 to the rear duct 60. From the outlet opening 62 in the rear duct 60, air enters the heater chamber formed by the channel pan 64. The air is heated by the heating element 66 and enters the tumbling drum 20 through the perforations in the drum wall 26. Moisture is entrained from the clothes in the tumbling drum and this moisture laden air flows out of the drum by way of the access opening collar 32 and the lint collecting housing 38 into the front duct 42 by way of the port plate openings 40. This air is channeled through the inlet header 46 for the condenser 48 and through the tubes 50 into the outlet header 52. While traveling through the condenser tubes, moisture is deposited therein by the cooling air fiow system which will be described next following and this moisture flows by gravity into the outlet header where an opening 70 channels the moisture to a mating opening 72 and a removable substantially enclosed envelope-like condensate container 74.

The cooling air system for the condenser 48 is comprised of a cooling air blower 76 connected by way of a fan-shaped duct '78 to the rear side of the condenser tubes 50. The blower 76 is effective to draw air through a screened opening 80 at the front of the condenser tubes, over the outside of the condenser tubes and into the duct 78, from which point the air is impelled to the atmosphere. This relatively cool air will cool the condenser tubes 50 and cause condensation of moisture from the recirculating air therein.

A single prime mover or motor 82 is effective through a belt and pulley system (not shown) behind the rear bulkhead 24 to rotate the tumbling drum 20 and to drive the cooling air blower 76 and the recirculating air blower 54.

The two air flow systems have been shown by arrows in FIGURE 1the solid arrows indicating the recirculating air flow and the dashed arrows indicating the cooling air flow for the condenser 48.

Turning now to FIGURE 2, the inlet air temperature dryer termination control of this invention will be described-components in FIGURE 2 carrying the same reference numeral as their counterparts in the detailed version of FIGURE 1. The basic relationship of the condensing dryer components shows the tumbling drum 20 in a recirculating air stream initiated by the blower 54. Diposed in the recirculating air stream on opposite sides of the tumbling drum is the heater 66 and the condenser 48 which may be either air cooled as shown in FIGURE 1 or water cooled. The condenser removes the moisture from the recirculating air stream which has been picked up from the clothes in the tumbling drum 20 and also reduces the air temperature when the clothes are dry from about 170 F. at the inlet of the condenser to about 130 F. at the condenser outlet. This pronounced temperature differential is used to advantage in the automatic control of this invention as will be understood more fully hereinafter.

The schematic wiring diagram for controlling the automatic drying cycle of the condensing drying is illustrated to FIGURE 3. The control circuit includes a power supply L L and a neutral line N. Disposed in intercepting relationship to the various dryer componets is a timer having its control knob 14 exposed on the console of the dryer and enclosing a plurality of cam actuated switches, such as 100 in the heater circuit, 102 in the timer motor circuit, 104 in the circuit for the

main motor

82 and 106 leading to an alarm 108 which may be sounded to signal the end of the automatic drying cycle. The

various timer switches

100, 102, 104 and 106 may be sequentially operated by a timer shaft 110 incrementally advanced or rotated whenever a timer motor 112- is energized. Other components in the drying circuit may include a door switch 114 having a position in series with the main motor 82 when the door is closed and a position in series with a lamp 116 when the door is opened. In the heater circuit there are various safety features such as a high limit control 118 which opens if temperatures exceed a safe level within the dryer and a centrifugal switch 120 which closes whenever the prime mover or motor 82 is satisfactorily in operation.

In addition to the foregoing, the novel automatic dryer control of this invention includes a fabric selector switch 122 which may be set through knob 16 or push buttons for a REGULAR drying cycle or a DELICATE drying cycle depending on the type fabric to be dried. More particularly, the cycle selector switch 122 includes a main heater switch 124 having a first position contact 126 whenever any heat is required in the drying cycle (knob 16 set for either REGULAR or DELICATE) and a second position contact 128 when NO HEAT is desired. The cycle selector also includes a switch 130 having a firstv position contact 132 in series with a biasing heater 134 (knob 16set forDELICATE) and a second position 4 contact 136 for by-passing the biasing heater 134 (knob 16 set for REGULAR).

The automatic control circuit includes an exhaust air thermostat or cycling control 140 which may be positioned on the door 36 in the path of air leaving the tumbling drum through the lint collecting housing. This cycling control includes a temperature responsive switch 142 having a first position contact 144 in series with the main heater 66 and a second position or back contact 146 connected through an inlet air thermostat or termination control 148 to the timer motor 112. The switch 142 is selectively heat biased in order to provide a low temperature range for DELICATE fabrics (142 F.- 150 F.) when the selector switch 130 is engaged with contact 132 and a high temperature range for REGULAR fabrics F.-177 F.) when the switch 130 is moved to contact 136. Assuming a REGULAR cycle, for instance, the switch 142 engages the contact 144 when the temperature of air leaving the tumbling drum is below approximately 170 F. to energize heater 66. On the other hand, the switch 142 engages the back contact 146 when the exhaust air temperature exceeds approximately 177 F. Thus, the switch 142 moves between

contacts

144 and 146 to maintain a predetermined temperature within the tumbling drum.

The inlet air thermostat or termination control switch 148 has an open position so long as the temperature of the air entering the tumbling drum is above 210. However, the switch 148 remains closed whenever the inlet air temperature is below 200 F. With the foregoing components, the control cycle for a DELICATE or REGULAR drying cycle will be described next following.

General On the Automatic drying cycle of this invention, the user sets the timer knob 14 to either DELICATE or REGULAR and the Fabrics control knob 16 for the type of material being dried. This indirectly establishes the drying time and temperature. The Automatic drying cycle is based on temperature and, on the DELICATE setting, the timer runs only when the heater element is off and the cycle termination switch 148 is closed or when timer switches 102 and 104 are closed.

Regular load drying cycle Referring to FIGURES 3, 4 and 5, a REGULAR drying cycle will be initiated when the cycle control knob 14 is manipulated to position the contacts as shown at the REGULAR start indicator in FIGURE 4. At the same time, the operator will operate the selector switch 122 by manipulating the control knob 16 to position the switch 124 on contact 126 and the switch 130 on contact 136 for the REGULAR fabric drying temperature. As the timer is advanced to the REGULAR start position, timer switches 100, 102 and 104 are closed. Thus, the main motor 82 is energized through timer switch 104 to start the rotation of the tumbling drum 20 and the recirculation blower 54. At the star of a drying cycle, the temperature of the recirculating air would be below the temperature setting of the selector switch 124 and the temperature cycling control switch 142 will engage the contact 144 to energize the heater 66. As aforesaid, the centrifugal switch 120 will be closed when the main motor 82 is running. Note also that the termination control switch 148 which is measuring drum inlet air temperature is closed at the start of the cycle since the initial temperatures of the recirculating air are below 200 F.

The timer motor. 112 will be energized from L through the timer switch 104, jumper line 150, timer switch 102, the timer motor 112 to the other side of the line N. As the automatic cycle advances, and with reference to FIG- URE 5, the temperature at the exhaust air thermostat or cycling control switch 140 is shown by the curve portion 154 and the temperatures occurring at the inlet air thermostat or termination control switch 148 are evidenced by the curved portion 156. Note that the temperatures at both the inlet and the exhaust are increasing as would be expected with the heater 66 energized. At a point .158, the termination control switch 148 opens to break the shunt or parallel path through the temperature selector switch 130 and the timer switch 104; and the timer motor 112 is then energized solely through the timer switch 102. The temperature of the recirculating air at the outlet of the tumbling drum continues to increase to a point 160, at which point, the temperature of the air coming out of the tumbling drum exceeds 177 so that the switch 142 moves to its position in engagement with the back contact 146. This deenergizes the heater 66 and the recirculating air temperature starts to cool along the curve portion 162 until a curve :point 164 is reached, at which point, the switch 142 again moves into engagement with the contact 144 to reenergize the heater 66 along a curve portion 166. Thus, the heater 66 is energized and deenergized while the REGULAR clothes load is being driedeach period of heater energization being progressively shorter as the clothing gives up its moisture and, thus, its latent load to the recirculating air stream.

Simultaneously with the cycling of the heater 66 and, more specifically, at a point 168 which coincides with the point 160 on the exhaust air temperature curve, the temperatures of the recirculating air at the inlet of the tumbling drum start to cycle in response to the on-olf operation of the heater 66. Thus, when the heater is 011 and the exhaust air is falling as at curve portion .162, so also does the air temperature fall off at the inlet of the tumbling drum as evidenced by curve portion 170. Since the heater is energized for progressively shorter periods (curve portion 166 spans a greater period of time than curve portion 172), it would be natural to expect that the temperature gradient of the inlet air adjacent the heater would fall off gradually. This is evidenced by the fact that inlet air temperature curve points 174, 176 and 178 are progressively lower and are approaching the 200 F. point 180, at which time, the termination control switch 148 will close.

The foregoing explanation of FIGURE 5 shows the various temperature variations wihch occur at the cycling control 140 and the termination control 148 throughout the entire automatic drying cycle. It is necessary now to return to FIGURE 4 to explain the interplay between the

thermostatic controls

140 and 148 and the timer motor 112. It can be seen that the timer switches 100, 102 and 104 remain closed for a timed period 105 from start up until the timer switch 102 opens to initiate an indefinite pause period 182. This timed period 105 of approximately eight minutes built into the timer is shown by upwardly leftwardly diagonal shading in FIGURE 5. Once timer switch 102 opens at the end of this timed period, the energization of the timer motor 112 is under the sole control of the series arranged termination control 143 and the timer motor switch 104 through the fabric selector switch 130 engaged on contact 136. In other words during the REGULAR drying cycle, the cycling control switch 142 on its back contact 146 does no more than parallel the circuit to the termination control 148. Thus, from the inlet air curve point 159 to the curve point 180 the termination control 148 remains open and the timer motor 112 deenergized. As soon as the curve point 180 is reached, the termination control switch 148 closes and the timer motor 112 will be reenergized to advance the automatic cycle through the pause period 182. At its first timer pulse after reenergization, the timer motor cam shaft 110 will open the timer switch 100 to deenergize the heater circuit while maintaining closed the timer switch 104 to continue the recirculating air in a COOL-OFF period to lower the temperature of the fabric to a point suitable for handling. The timer motor switch 102 will be closed for the duration of the cool-oft period. The REGULAR drying cycle will be terminated at the conclusion of the cool-off period when the timer switch 106 is closed to energize the alarm 108 after which timer switches 102, 104 and 106 will be opened to terminate the drying cycle.

Delicate load drying cycle Using FIGURES 3, 4 and 6 for the operational timer sequence of the condensing dryer, assume that a DELI- CAT E setting on the Timer and on the Fabrics control has been made. The switches 104 and of the timer are closed but switch 102 for the timer motor is open. Referring back to FIGURE 3, note that the circuit from L through the timer switch 100, the fabrics control switch 126, cycling control switch 142, limiter control 118, heater element 66 and centrifugal motor switch to L is complete when the motor comes up to speed. In normal operation on DELICATE, current is supplied from timer switch 104 through the internal circuit switch of the Fabrics control to the heater or resist-or 134 in the cycling control to cause the control switch 142 to open sooner than its normal air operating temperature. Note: The resistor 134 is not energized on the high temperature or REGULAR fabric settings and the cycling control regulates the dryer as though it were a normal 177 F. thermostat.

When the clothes load gets up to heat, approximately F. air temperature, bimetal disc switch 142 closes on its back contact 146-approximately 177 F. i5 disc temperature at rated 240 volts clue to the additional heat being supplied by the resistor 134. Current then flows through to the termination control and, if the switch 148 is closed, current is supplied to the timer motor to advance the timer. Due to the long heat period of the first cycle the termination control switch 148 will more than likely remain open during the entire heater element OFF period 192 of the first cycle (FIGURE 6) and the timer will not advance. During the second heater element ON period 194, less heat is required to bring the load up to heat. This allows the terminating control area at the rear of the tumbling drum to cool more rapidly so that switch 148 can close to advance the timer during the second element OFF period 1%. Note: Timer advance is shown by two differently shaded areas in FIG- URES 6 and 7; one type of shading indicates pause periods of indefinite duration while the timer is under the combined control of the termination control switch 148 and the cycling control switch 142; another type of shading indicates programmed or timed periods when the timer motor is energized continuously through the timer switch 102.

As the DELICATE clothes load dries and progressively less heat is required to bring the dryer up to temperature, the terminating control area remains cooler and the timer will advance for longer periods, i.e., shaded area 198 is longer than shaded area 200. Once the timer advances through the pause period 186, using up the last of the four minute interval built into the timer pause period as at 201, the timer switch 102 is closed to drive the timer motor continuously for approximately 12 minutes and the heater element cycles OFF and ON as required during this timed period 202. At the end of the timed period, the timer switch 102 open again and current must again be supplied through switch 142 and contact 146 of the heat control and through the termination control 148 to drive the timer approximately one minute. In FIGURE 6 this second one minute pause period is made up of shaded

sections

204 and 206. When the second pause period 182 is used up, timer switch 102 then closes to drive the timer through approximately a 7 minute cool-off period. Heater element switch 100 in the timer is open during this cool-off period.

FIGURE 7 is a graphic representation showing the rying cycle characteristics for a two pound DELICATE load. The foregoing explanation for the six pound DELICATE load should provide adequate background for a complete understanding of FIGURE 7.

It should now be seen that an improved automatic con trol has been provided for a condenser dryer. Throughout the time that air is being recirculated to dry the clothes, a condenser is effective to remove the moisture from the air and to cool the recirculating air as it gives up its heat of condensation. The pronounced cooling effect afforded by a condenser in the recirculating air stream when the clothes load is dry and the progressively decreasing heating effect of the heater throughout the drying cycle combine to effect an improved termination control which very accurately senses the proper end point dryness of the clothes load. Further, a circuit arrangement has been taught which will permit a single termination control to terminate drying cycles for different loads at difierent temperatures.

While the embodiment of the present invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows.

1. In combination with a condensing clothes dryer having means defining a recirculating air stream, means for condensing moisture from said recirculating air stream, means for tumbling clothes in said recirculating air stream, heating means on the upstream side of said tumbling means for heating said recirculating air stream and blower means for initiating said air stream, a control circuit comprising timing means for sequentially controlling said heating means and said blower means in a programmed drying cycle of predetermined duration including a timer motor to advance said drying cycle, first switch means thermally responsive to the temperature of said recirculating air stream on said upstream side of said tumbling means and in series electrical flow relationship with said timer motor for energizing and deenergizing said timer motor, said first switch means having a closed position for energizing said timer motor when the temperature of said recirculating air stream at said first switch means is below a first predetermined value and an open position for deenergizing said timer motor when the temperature of said recirculating air stream is above said first predetermined value, second switch means thermally responsive to the temperature of said recirculating air stream on the downstream side of said tumbling means and manually selectively electrically connected to a portion of said timing means and in selective series electrical flow relationship with said first switch means or said heating means, said second switch means having a first position in series with said heating means when the temperature of said recirculating air stream at said second switch means is below a second predetermined value to heat said recirculating air to dry the clothes and a second position in series with said first switch means when the temperature of said recirculating air stream at said second switch means is above said second predetermined value to condition said timer motor to advance said drying cycle, said drying cycle being terminated in a time interval longer than said predetermined duration of said programmed drying cycle when said first switch means remains in said closed position due to the action of said condensing means and said second switch means moves to said second position to energize said timer motor until said portion of said timing means deenergizes said control circuit.

2. In combination with a condensing dryer having means defining a recirculating air stream, means for condensing moisture from said recirculating air stream, means for tumbling clothes in said recirculating air stream, and heating means on the upstream side of said tumbling means for heating said recirculating air stream, a control circuit comprising timing means for sequentially controlling said heating means in a programmed drying cycle of predeter mined duration including a timer motor to advance said drying cycle, first switch means thermally responsive to the temperature of said recirculating air stream on said upstream side of said tumbling means and in series electrical flow relationship with said timer motor for energizing and deenergizing said timer motor, said first switch means having a closed position for energizing said timer motor when the temperature of said recirculating air stream at said first switch means is below a first predetermined value and an open position for deenergizing said timer motor when the temperature of said recirculating air stream is above said first predetermined value, second switch means thermally responsive to the temperature of said recirculating air stream on the downstream side of said tumbling means and electrically connected to a portion of said timing means and in alternating series electrical flow relationship with said first switch means or said heating means, said second switch means having a first position in series with said heating means when the temperature of said recirculating air stream at said second switch means is below a second predetermined value to heat said recirculating air to dry the clothes and a second position in series with said first switch means when the temperature of said recirculating air stream at said second swtich means is above said second predetermined value to condition said timer motor to advance said drying cycle, said drying cycle being terminated in a time interval longer than said predetermined duration of said programmed drying cycle when said first switch means remains in said closed position due to the action of said condensing means and said second switch means moves to said second position to energize said timer motor until said portion of said timing means deenergizes said control circuit.

3. The combination of claim 2 including manually selectable means interposed between another portion of said timing means and said first switch means for bypassing said second switch means to condition said timer motor for energization in response to said first switch means and said another portion of said timing means.

4. In combination with a condensing fabric dryer having means defining a recirculating air stream, means for condensing moisture from said recirculating air stream thereby to cool said air stream, means for tumbling fabric in said recirculating air stream, heating means on the upstream side of said tumbling means for heating said recirculating air stream and blower means for initiating said air stream, a control circuit comprising timing means for sequentially controlling said heating means and said blower means in a programmed drying cycle of a first predetermined duration for delicate fabrics including a timer motor to advance said drying cycle, first switch means thermally responsive to the temperature of said recirculating air stream on said upstream side of said tumbling means and the downstream side of said condensing means and in series electrical flow relationship with said timer motor for energizing and deenergizing said timer motor, said first switch means having a closed position for energizing said timer motor when the temperature of said recirculating air stream at said first switch means is below a first predetermined value effected by the cooling of the recirculating air stream as it passes through said condensing means when the clothes are dry and an open position for deenergizing said timer motor when the temperature of said recirculating air stream is above said first predetermined value, second switch means thermally responsive to the temperature of said recirculating air stream on the downstream side of said tumbling means and the upstream side of said condensing means, said second switch means being electrically connected to a portion of said timing means and in selective series electrical fiow relationship with said first switch means or said heating means, said second switch means having a first position in series with said heating means when the temperature of said recirculating air stream at said second switch means is below a second predetermined value lower than said first predetermined value to heat said recirculating air to dry the clothes and a second position in series with said first switch means when the temperature of said recirculating air stream at said second switch means is above said second predetermined value to condition said timer motor to advance said drying cycle, said drying cycle being terminated when said first switch means is in said closed position simultaneously with said second switch means in said second position to energize said timer motor until said portion of said timing means deenergizes said control circuit.

5. The combination of claim 4 including means for bypassing said second switch means to condition said timing means for sequentially controlling said heating means and said blower means in a programmed drying cycle of a second predetermined duration shorter than said first predetermined duration for regular fabrics.

6. In combination with a condensing dryer for moist fabric having means for agitating said fabric, means defining a recirculating air flow including said agitating means, means upstream from said agitating means for heating said recirculating air flow, means defining a cooling air flow in heat transfer relationship to said recirculating air flow for condensing moisture from said recirculating air flow, means for actuating said agitating means and inducing said air flows, and drying cycle control means having timer switch means for starting and automatically stopping said heating means and said agitating and inducing means, said control means including a timer motor for operating said timer switch means, a first increasing temperature responsive switch means in said recirculating air flow downstream from said agitating means and in series electrical flow relationship with a portion of said timer switch means, said first switch means having a first position in series with said heating means and a second position, a second decreasing temperature responsive switch means in said recirculating air flow upstream from said agitating means and in series with said timer motor and said first switch means in said second position, said drying cycle being advanced only when said portion of said timer switch means, said first switch means in said second position and said second switch means are in electrical supply relationship to said timer motor.

7. In combination with a condensing dryer for moist fabric having means for agitating said fabric, means defining a recirculating air flow including said agitating means, means upstream from said agitating means for heating said recirculating air flow, means defining a condenser in heat transfer relationship to said recirculating air flow for condensing moisture from said recirculating air flow, means for actuating said agitating means and inducing said air flows, and drying cycle control means having timer switch means for starting and automatically stopping said heating means and said agitating and inducing means, said control means including a timer motor for operating said timer switch means, a first increasing temperature responsive switch means in said recirculating air fiow downstream from said agitating means and upstream from said condenser and in series electrical flow relationship with a portion of said timer switch means, said first switch means having a first position in series with said heating means and a second position, a second decreasing temperature responsive switch means in said recirculating air flow upstream from said agitating means and downstream from said condenser and in series with said timer motor and said first switch means in said second position, said drying cycle being advanced only when said portion of said timer switch means, said first switch means in said second position and said second switch means are in electrical supply relationship to said timer motor.

8. In combination with a condensing dryer for moist fabric having means for agitating said fabric, means defining a recirculating air flow including said agitating means, means upstream from said agitating means for heating said recirculating air flow, means defining a condenser in heat transfer relationship to said recirculating air flow for condensing moisture from said recirculating air flow, and drying cycle control means having timer switch means for starting and automatically stopping said heating means, said control means including a timer motor for operating said timer switch means, a first increasing temperature responsive switch means in said recirculating air flow downstream from said agitating means and upstream from said condenser and in series electrical flow relationship with said timer switch means, said first switch means having a first position in series with said heating means and a second position, a second decreasing temperature responsive switch means in said recirculating air flow upstream from said agitating means and downstream from said condenser and in series with said timer motor and said first switch means in said second position, said drying cycle being advanced only when said timer switch means, said first switch means, said first switch means in said second position and said second switch means are in electrical supply relationship to said timer motor.

9. In combination, casing means defining a fabric drying chamber having an inlet and an outlet, means connected to said inlet and said outlet to form a closed circuit duct system, means for recirculating air in said duct system, means adjacent said inlet to said drying chamber for heating said air to a first or second temperature to vaporize moisture from said fabric in a drying cycle, means for selecting said first or second temperature, means in said duct system for condensing said moisture from said recirculating air, power supply means, timer means for completing a power circuit to said power supply means and operable by a timer motor to interrupt said power circuit, and means for controlling said timer motor to terminate said drying cycle, said last named means including a termination control switch in said recirculating air at said inlet and in series with said timer motor, said termination control switch having a closed position when the temperature of said air at said inlet is at a predetermined value higher than either said first or second temperature, a cycling control switch in said recirculating air at said outlet and in series with said timer means, said cycling control switch having a first position in series with said heating means to dry said fabric when the temperature of said air is below said preselected temperature and a second position in series with said termination control switch to condition said timer motor for connection to said power circuit to operate said timer means when said termination control switch is closed and the temperature of said air is above said preselected temperature.

10. The combination of claim 9 wherein said temperature selecting means includes means connectable to said power supply means and in series with said termination control switch for by-passing said cycling control.

11. In combination, casing means defining a fabric drying chamber having an inlet and an outlet, means connected to said inlet and said outlet to form a duct system including a condenser, means for recirculating air in said duct system through said condenser, means adjacent said inlet to said drying chamber for heating said air to a first or second temperature to vaporize moisture from said fabric in a drying cycle, means for selecting said first or second temperature, power supply means, timer means for completing a power circuit to said power supply means and operable by a timer motor to interrupt said power circuit, and means for controlling said timer motor to terminate said drying cycle, said last named means includ ing a termination control switch in said recirculating air on the downstream side of said condenser at said inlet and in series with said timer motor, said termination control switch having a closed position when the temperature of said air at said inlet is at a predetermined value higher than either said first or second temperature, a cycling control switch in said air on the upstream side of said condenser at said outlet and in series with said timer means, said cycling control switch having a first position in series with said heating means to dry said fabric when the temperature of said air is below said preselected temperature and a second position in series with said termination control switch to condition said timer motor for connection to said power circuit to operate said timer 1 1 means when said termination control switch is closed and the temperature of said air is above said preselected temperature.

12. The combination of claim 11 wherein said temperature selecting means includes connectable to said power supply means and in series with said termination control switch for by-passing said cycling control.

References Cited by the Examiner UNITED STATES PATENTS 2,505,041 4/1950 Gorsuch 34-45 Hammell 34-53 Shewmon 3477 Dunkelman 3445 Engel 34-45 Hughes 3445 Gray 34-45 WILLIAM F. ODEA, Acting Primary Examiner.

10 NORMAN YUDKOFF, Examiner.