US2743533A

US2743533A - Automatic control for clothes driers

Info

Publication number: US2743533A
Application number: US352443A
Authority: US
Inventors: Thomas R Smith
Original assignee: Maytag Corp
Current assignee: Maytag Corp
Priority date: 1953-05-01
Filing date: 1953-05-01
Publication date: 1956-05-01
Anticipated expiration: 1973-05-01

Description

y 1956 T. R. SMITH 2,743,533

AUTOMATIC CONTROL FOR CLOTHES DRIERS Filed May 1, 1953 2 Sheets-Sheet l rwentov Thoma QSmiPh May 1, 1956 T. R. SMITH 2,743,533

AUTOMATIC CONTROL FOR CLOTHES DRIERS Filed May 1, 1955 2 Sheets-Sheet 2 HEA r/Na ELEMENT 5mm arop //34 ;9.9 000,? Okla E N070? SWITCH 5/09 awn E1 MOTOR 1. N

,dnvenlor moms Qsmirh temperature for comfortable handling.

United States Patent AUTOMATIC CONTROL FoR CLOTHES omens Thomas R. Smith, Newton, Iowa, assignor to The litaytag Company, Newton, Iowa, a corporatien of Delaware Application May 1, 1953, Serial No. 352,443 13 Claims. c1. s4-- 4s The invention relates to control apparatus and more particularly to control apparatus for clothes driers of 2,743,533 Patented May 1, 1955 'ice medium.

Other objects, features, capabilities and advantages are comprehended by the invention, as will later appear and drier through an inlet and itfflows over a surface. associated with the casing and out of an outlet. Under drying conditions, after the drier has been put into operation for a predetermined length of time to initiate the drying operation, the vapor evaporated from the clothing contacts the surface cooled by the condensing medium and is condensed, with the result that the temperature of the condensing medium is increased as it flows to the outlet. A differential control mechanism responsive to the temperature of the condensing medium entering and leaving the drier is provided and this difference'in temperature is reflected upon switch means which, when the temperature difference is relatively high, maintains the heating element circuit closed. Toward the end of the drying operation when the major portion of thevapor is evap orated from the clothes, the rate of heat absorptionby the condensing medium decreases. Thus the difference in temperature of the condensing medium at the inlet and outlet tends to become more nearly equal and this is reflected on the control mechanism to open the heating element circuit to thereby terminate the-heating operation, after which the clothes may be tumbled for apredetermined length of time to cool the clothing to a lower In still another form, control apparatus is provided which eliminates the tumbling of the clothing after the heating operation is terminated. Accordingly, it is another object of the invention to provide a vapor condensing type clothesdrier with control apparatus which is responsive to the temperature difference between the condensing medium at, its inlet and outlet to terminate the application of heat to the drier.

It is yet another object of the inventionto provide a vapor condensing type clothes drier with a simplified control apparatus which maintains the energization of the heating means regardless of the load in the drier until the temperature difierence between' the condensing medium at its inlet and outlet decreases, to a predetermined value.

It is another object of the invention to provide a vapor condensing type clothes drier with control apparatus which initiates the drying operation for a predetermined length of time after which a temperature dilferential responsive switch controls the duration of the dryingoperation.

It is still another object of the invention to provide a as are inherently possessed thereby.

Referring to the drawings:

Figure 1 is a diagrammatic vertical longitudinal sectional View of a vapor condensing type clothes drier to which the improved control apparatus may be applied;

Figure 2 is a vertical transverse sectional view taken generally along the line 2-2 of Figure 1;

Figure 3 is a diagrammatic wiring diagram and arrangernent for a vapor condensing type clothes drier incorporating the improved temperature diiferential control features, and

Figure 4 is a diagrammatic wiring diagram and arrangement for a slightly modified differential control applied to a vapor condensing clothes drier of a different type.

Referring now more in detail to Figures 1 to 3 of the drawings for an embodiment of a clothes drier selected to illustrate an embodiment of the improved control apparatus, there is shown a tumbler type clothes drier 10 having a horizontally mounted rotatable perforate'drum 11 enveloped or encompassed by a substantially imperforate stationary sheet metal casing or container 12 providing a drying chamber 13 in which the drum 11 rotates. The container or casing 12 is suitably supported on a base frame 14 and the entire assembly is surrounded by' rotated.

From the rear wall of the drum the drum shaft 18 extends axially rearwardly through the container 12 and its outer end has, a driven pulley 21 of any suitable type secured thereto. This pulley may be driven at a reduced speed by means of a speed reduction pulley and belt arrangement 22 connected to a driving'means or motor 23 mounted on the base frame construction 14. In addition, the drum shaft is suitably journaled in a housing construction 24 which in turn is rigidly secured to the base 14 in any suitable manner.

The container or casing 12 surrounding the drum 11 includes a substantially imperforate longitudinally extending wall 26, whose lower sector 27 is generally cylindrical in transverse section and axially recessed at its lowermost portion for substantially its entire length to provide a water collecting trap or sump 28, a rear wall 29 and a front wall 31 having an access opening 32 aligned with the access opening 17 in the drum. All of these elements are secured together at their marginal edges in any suitable manner to provide a unitary rigid structure. On addition, the outer surface of the container 12 is preferably provided with suitable heat insulating material 33 to improve the overallefnciency of the drier.

The cabinet 16 which completely encloses the container 12, base frame construction 14, drive mechanism 23 and other auxiliary equipment, has an access opening 34 in its front wall 36 in alignment with the

access openings

32 and 17 in the casing and drum, respectively, and the cabinet opening 34 is provided with a hinged insulated door or closure 37. Covering or encompassing the aligned access openings is a resilient combination gasket and seal 39 for engaging the inner surface of the door 37 to seal about the openings and to provide a static seal between the. adjacent portions of the cabinet and casing. A door switch 38 is automatically operated by movement of the door in a manner to be hereinafter described.

In order to evaporate the moisture in the clothing, heat from a suitable source must be supplied to the drying chamber 13. In the modification shown, there is disclosed, by way of example, a pair of standard sheathed electric heating elements 41 which are mounted within the drying chamber 13 in oppositely disposed recessed portions at the upper section of the casing beyond the outer periphery of the drum 11.

Since the stationary container 12 is not provided with an air inlet or outlet, means must be provided to dispose of the vapor evaporated from the moist clothing being dried. In the preferred form, the vapor is condensed by having it directly contact a zone or area 42 on one side of the lower cylindrical wall portion 27 of the container 12 which is directly cooled by a stream or thin film of cool water flowing over its inner surface or periphery. The cooling or condensing water may be supplied from any suitable source of supply under the control of a solenoid operated water control valve 43 and it is discharged from the downwardly directed end of a conduit 44 into a distribution box or receptacle 46. The inner wall of the receptacle is formed as part of the wall 26 of the casing and defines the upper end of the condensing section or zone 42. In addition, the portion of the casing 12 defining the inner wall of the water distributing receptacle is provided with a plurality of parallel and horizontally spaced small orifices or openings 47 through which the water fiows by gravity during the drying operation.

Covering these openings within the casing is a curtain type flap or check valve 48 having its upper end anchored to the casing and its lower end free. In this manner, the escape of vapor through the openings 47 into the interior of the cabinet 17 is obviated, while at the same time the condensing water flows through some of the distributing openings 47, passes the lower edge of the check valve and flows downwardly over the condensing zone 42 in rela tively thin film. I

The lower end of the condensing zone 42 is recessed as previously mentioned to provide the trap or sump 28 for collecting the condensing water, condensed vapor and a lint, and this sump has a centrally located drain outlet 49 which also provides the inlet to a centrifugal pump 51 mounted directly therebelow at the lowermost portion of the casing. The pump may be rotated by the drive motor 23 through suitable drive or belt mechanism 52 and the discharge end of the pump is connected to an enlarged space 53 open to a conduit 54 which leads to a suitable drain.

Referring now more particularly to Figure 3 for a dc tailed description of the improved control apparatus for a vapor condensing clothes drier, there is shown a timer 56 having a shaft 57 extending upwardly through the top wall of the cabinet 16 on which is mounted a control knob or dial 58 adapted to be grasped by the operator and turned in a clockwise direction, as viewed in the drawings, to initiate the drying operation. As shown, the timer knob 58 has been manipulated to start the drying operation.

Rigidly secured to the shaft 57 are switch actuating cam means 59 and 60 each having spaced lobes or

abutments

61 and 62 and 63 and 64, respectively, which are adapted to engage and actuate

suitable switches

65, 66, 67 and 68, respectively, in a manner to be hereinafter described. In addition to the control knob 58, the timer shaft 57 is adapted to be slowly advanced or rotated. in

til)

one direction by means of a low capacity constant speed motor 69 through suitable speed reduction or escapement mechanism 70. The timer motor 69 is connected, along with the condensing water control valve 43 and the drum drivemotor 23, to the neutral line N through a common conductor 71 and the switch 67 which is actuated by the lobe 63 on the cam 59 as soon as the timer shaft 57 is shifted or rotated. The opposite side of the valve and the drive motor are connected in parallel to a conductor 72 in series with the door switch 38 leading to the line Ll. Thus, as soon as the knob 58 is turned, the drive motor 23 is energized to rotate the drum 11 about its horizontal axis, the valve 43 is opened to supply condensing water to the receptacle 46 to flow the same over the condensing area 42 to the sump 28, and to energize the timer motor 69 to advance the cams in a positive manner. The opposite side of the timer motor is initially energized from a conductor 73 leading to the cam operated switch and from the opposite side of the switch to a conductor 74 connected to the conductor 72 leading to the line Li.

Initial energization of the heating elements 41 is from the line L2 and from the opposite side of the heating elements to a thermostat actuated switch 75 which has its temperature responsive bulb 76 mounted within the drying chamber 13 to provide an upper limit on the temperature therein. From the opposite side of the thermostat switch 75 conductors 77 and 78 lead to the switch 66 actuated by the lobe 62 on the cam 60 and the heating element circuit is completed by means of conductor 79 connected to the conductor 72 leading to the line L1.

Disposed within the liquid distribution receptacle 46 is a temperature responsive bulb 80 which reflects the inlet temperature of the condensing water discharged from the conduit 44 through a tube 81 directly to an expansibic member or sylphon bellows 82 which forms part of a differential temperature responsive switch 83. A second temperature responsive bulb 84 placed in the chamber 53 at the discharge side of the centrifugal pump 51, or any other suitable location, is responsive to the temperature of the condensing water as it leaves the drying chamber 13 to transfer a force through a tube 85 to a second expansible member or sylphon bellows 86 mounted in opposition to the first mentioned one. These bellows may be adjustably mounted to provide the required balance of forces and act in opposition on opposite sides. of a suitable pivoted arm or contact carrying member 87 which, in this instance, carries a contact 88 directly connected to the line L1 through the conductor 72.

The contact 88 on the movable arm 87 is double acting and when the difierence in temperature of the condensing Water at the inlet and outlet is the same or relatively slight, the contact 88' engages a contact 89 which is connected to a conductor 90 leading to the timer motor 69. Under these conditions the timer motor is energized to advance the cams 59 and 60. .However, when the drier is in operation and vapor is being condensed, the temperature of the condensing water is increased in so doing; therefore, with the inlet water temperature remaining substantially constant the temperature of the condensing Water leaving the drying chamber 13 will be increased by an amount equal to the latent heat of vaporization, the sensible' heat in the condensate and the heat naturally absorbed in passing through the heated drying chamber 13. This temperature difference is reflected on the bellows 86 which counteracts the force of the opposing bellows 82 and shifts the movable contact 88 in the direction to engage a heating element contact 91 which in turn is connected to a conductor 92 leading to the cam operated switch 68 on the timer. This switch is also connected to the conductor 77 and completes the heating element circuit from the lines L2 and L2.

As, long as. vapor is being generated by the heating elements 41, this tempcrature ditterence will exist or prevail and after the initial timed operation has transpired: and the

switches

65 and 66. on the timer cam 60 are opened,

energy will be continuously supplied to the heating elements, assuming, of course, that the temperature responsive switch 75 remains closed. Toward the end of the drying period, the quantity of vapor in the chamber 13 decreases; therefore, less vapor is condensed, with the result that the outlet temperature of the condensing water starts to drop. When the outlet water temperature approaches the inlet water temperature the movable contact 88 is moved away from the heating element contact 91 by the balancing forces of the

bellows

82 and 86 and opens the heating element circuit. At the same time, this action closes the timer circuit at the contact 89 and the timer motor 69 is energized to again advance the cams. After a predetermined length of time, from five to ten minutes, the timer motor advances the cams to a point Where they open the switches 67 and 68 to thereby open the circuits to the heating elements 41, drive and

timer motors

23 and 69, respectively, and the water control valve 43. At this point the drying operation is completedbecause the

switches

65 and 66 were opened at the end of the initial timed starting portion of the cycle. The switch 68 is primarily provided to maintain the heating element circuit open at the end of the drying operation.

In the operation of a clothes drier of the type disclosed, the operator opens the door 37 and inserts the damp clothing to be dried into the rotatable drum 11 through the aligned access openings, after which the door is closed and latched against the door gasket 39 to seal the interior of the container 12 at this point and such action closes the door switch 38.

Next the operator adjusts or manipulates the control knob 58 to its starting position. This action closes the

switches

65, 66 and 67 in the timer to energize the timer and drive motors, 69 and 23, respectively, open the condensing water control valve 43 and energize the heating elements 41. At the start of the drying operation, the

bellows

82 and 86 are substantially in equilibrium because there is no or very little temperature difierence between the two and the movable contact 88 engaging contact 89 is in the position to energize the timer motor 69 in parallel with the closed switch 65. Since the switch 68 and the

contacts

88 and 91 are open, energization of the heating elements 41 is effected through the closed switch 66 to supply heat to the drying chamber 13 to evaporate the moisture in the clothing, while they are tumbled at approximately 45 R. P. M. within the drum 11 by the drive motor 23. As the water control valve 43 opens, water flows throughr the conduit 44 into the water distribution receptacle 46 at the upper portion of the condensing area 42. This water then flows through the small openings 47 to provide a relatively wide and thin stream or sheet of water which passes from beneath the lower edge of the check valve 88 and flows uniformly downwardly by gravity over the condensing area. As the cooling or condensing water reaches the bottom of the casing, it is collected in the sump 28, flows to the outlet opening 49 providing the inlet to the centrifugal pump 51 and is discharged therefrom through the chamber 53 and conduit 61 to drain. Since the bulb 80 is in the dis- 1 tribution receptacle 46 and the other bulb 84 is in the chamber 53 at the discharge side of the pump, they directly reflect their respective water temperatures on the

bellows

82 and 86 forming the differential temperature responsive switch 83.

During the initial timed operation, the timer motor 69 slowly advances the cams 59 and 60. As the heat builds up in the drying chamber 13 the moisture in the clothing is evaporated therefrom. With the drum 11 being rotated in a counterclockwise direction, as viewed in Figure 2, the vapor is circulated around the inner periphery of the stationary container 12 and in so doing a portion of the vapor directly contacts the cold water flowing over the condensing area or zone 42 and is condensed. This results in a flow of vapor in the direction of the cold surface Where it is condensed. As the condensing water and condensate reachthe bottom of the chamber, it flows into the sump 28 and is discharged as previously mentioned.

Upon condensation of the vapor, heat is absorbed by the condensing water which, of course, raises the temperature of the same. As the heated condensing water passes over the bulb 84 in the chamber 53 and heats the same, the bellows 86 is expanded by the increased temperature, reacts against the opposing bellows 82 and compresses the same. In so doing the movable contact 88 is shifted to the left, as viewed in the drawings, to engage the heating element contact 91 to condition this side of the line for operation. At the end of the timed interval, for example, ten minutes, sufiicient to start the drying operation and raise the temperature of the discharge water, the

switches

65 and 66 on the timer are opened by the cam 60 and the switch 68 is closed by the lobe 67 on the cam 59. This action continues energization of the heating elements 41 through the

switches

83 and 68 and places the heating elements under the direct control of the differential temperature responsive switch. At the same time, the opened switch 65 deenergizes the timer motor to arrest the timer operation, while the drive motor 23 and valve 43 remain energized by the closed switch 67 at this point.

As long as vapor is evaporated from the clothing, this temperature difference of the water at the inlet and outlet will be maintained regardless of the initial temperature of the water at the inlet. It may be mentioned that the inlet water temperature may vary widely from a low temperature up to well over 100 F. and still provide for efficient operation.

When the major portion of the vapor is evaporated from the clothing, the rate of heat absorption of the condensing water decreases or declines with the result that the temperature of the water as it leaves the drying chamber is more nearly that of the inlet temperature. As the temperature at the discharge reaches a relatively low value, the bellows 86 responding to the bulb 84 is contracted and the other bellows 82 acts to shift the movable contact 88 in the direction to open the heating element circuit and terminate the application of heat to the drying chamber 13. As the movable contact opens the heating element circuit, it closes the timer circuit through the conductor 90, and energizes the timer motor which again begins to advance the timer cams.

This interval represents the cool-down period in which the clothes are tumbled within the chamber without the application of heat while the condensing water acts to absorb a portion of the residual heat to reduce the clothes to a temperature for comfortable handling. After a predetermined length of time, for example, five to ten minutes, the timer motor will move the cam 59 to open the remaining closed switches 67 and 68. This final movement opens the heating element circuit to prevent reenergization, and that portion of the control circuit in series with the timer and driving motors and valve. At this time, the operator need but open the door and remove the clothing which has been properly dried and cooled for safe handling.

By way of example, assuming the bulbs and 84 are at room temperature of approximately 70 F. the op posing forces on the bellows will be substantially equalized. As water is discharged through the conduit 44, the temperature of the bulb 80 will be reduced to approximately 50" F. and initially, before the temperature within the chamber is elevated by the heating element, the water discharge from the pump 51 over the bulb 84 will be approximately the same temperature; therefore, the forces of the bellows will likewise remain substantially equalized.

After the drying operation starts .the temperature of the water discharged over the bulb 84 will increase, due to the absorption of the latent heat of vaporization of the vapor and the sensible heat of the condensate, to approximately, lOOQF.v This increase in temperature is reflected on the bellows 86 and moves the arm 87 in opposition to the bellows 82 to maintain the

contacts

88 and 91. engaged. This temperature difference will remain substantially constant throughout the drying operation and will be maintained within relatively narrow limits regardless of the temperature of the inlet water.

As the heat absorption of the condensing water decreases toward the end of the drying operation because of decreased vaporization of moisture from the clothes, the temperature of the water discharged over the bulb 84 begins to decrease. When the temperature decreases approximately l to degrees the arm 87 is moved by the contracting bellows 86 and the bellows 82 in the opposite direction away from the heating element contact 91 to engage the timer contact 89 in the manner previously described.

Referring now to Figure 4 there is shown a modified type of vapor condensing clothes drier 94 and a modified differential temperature responsive control arrangement 95 in which the timing means. has been eliminated. This drier includes a rotatable drum 96 encompassed by a substantially imperforate casing 97 to provide a drying chamber 95. A drive motor 99 is adapted to rotate the drum about its horizontal axis through suitable speed reduction mechanism in the usual manner and the entire mechanism is preferably closed by a cabinet 100 to provide a pleasing appearance.

Extending downwardly from the lower portion of the casing is a heat exchanger 101 comprising a plurality of vertically extending tubular members 102 whose upper open ends communicate directly with the drying chamber 98 and whose lower open ends communicate with a lower header 103 in which the condensed vapor is collected prior to being discharged through a conduit 104 in any suitable manner to drain. Surrounding the heat exchanger is a generally horizontally arranged duct 105 having an inlet 106 and an outlet 107 with a fan or blower 103 driven by a motor 109 disposed in the duct at one side of the heat exchanger 101. This blower is adapted to draw condensing air through the inlet 106 from the ambient atmosphere, circulate the same about the tubular condensing members 102 to condense the vapor within the tubes by removing the latent heat of vaporization and some of the sensible heat from the liquid, after which it is discharged through the outlet opening 107 back into the ambient atmosphere at the opposite side of the cabinet.

Disposed within the drying chamber 98 adjacent its upper sector is a heating element 110 of any suitable type and a temperature responsive switch 111 which provides an upper limit on the temperature therein.

The operation of the drier is adapted to be manually initiated after which it is under the control of the differential control means 95. This control means includes a pair of sylphon bellows 112 and 113 mounted in opposition to each other through a bar or member 114. The one bellows 112 is made responsive to the temperature of the inlet air by means of a bulb 115 carried at the inlet side 106 of the heat exchanger 101 while the other bellows 113 is made responsive to the air on the discharge side of the heat exchanger by directly connecting it to a bulb 116 suitably positioned adjacent the outlet 107 of the duct 105. Each bellows is properly proportioned for the operating conditions and adjusting means 117 may be provided to modify within limits the movement of the bellows.

Between the sylphon bellows and loosely encompassing the bar- 114 there is provided a stationary abutment or stop member 118 and a pivotal or movable arm 119 carrying a pair of

movable contacts

120 and 121 thereon, which. are adapted to engage mating stationary contacts to energize a pair of electrical circuits. These two elements. are longitudinally spaced from each other a suitable distance to provide roomfor a slidable contact moving member or abutment 122 therebetween. This member has a passage therethrough encompassing the bar 114 and is frictionally held in position thereon by a spring member 123 or any other suitable gripping device. The movable abutment 122 is further provided with a pair of oppositely sloping cam surfaces 124 and 125 facing in the direction of a pair of independently

movable cams

126 and 127 which are each normally biased in a direction away from the movable abutment by means of. independent compression springs 128. The outer end of cam 12d has a start push button 129 thereon which, when depressed the full limit, engages the mating cam surface 124 with the result that the abutment 122 is shifted to the right, as viewed in the drawings, regardless of the relative position of the bellows with respect to the stationary abutment 118. The other cam 127 has an of? push button 130 which, when depressed the full limit, engages the opposite cam surface 125 on the movable abutment and shifts the same to the left along the bar 114 to engage and move the arm 119 carrying the

contacts

120 and 121 in such direction as to open the electrical circuits.

The electrical circuits involved are the heating means and drive and blower motor circuits. In this instance, the heating means circuit extends from the line L1 through the door switch 131 and a conductor 132 to the movable arm 119 carrying the

contacts

120 and 121. A conductor 135 connects the upper cont act 121 in series with the thermostat 111 and heating element 110, and the opposite end of the heating element is connected to the line L2 to provide a 230 volt circuit. The lower contact 1'20 on the movable arm is connected to a conductor 1'34 leading to one side of the drive and blower motors 9'9 and 109, respectively, and the other side of the motors is connected to the neutral N to complete the circuit therethrough and provide a 115 volt circuit.

Thus it can be seen that when the movable contacts are moved to the right by the spring 135 they engage their respective contacts and both circuits are simultaneously energized; likewise, when moved to the left by the movable abutment 122, the circuits are opened and the drying operation is terminated. Also, note that the movable abutments position may be changed relative to the movable arm 119' by means of the differential force of the opposing bellows in either direction. When moved to the right the movable abutments relative position is changed when the same contacts the stationary member 118 and when moved to the left, by the dilferential (forces of the bellows or earn 127, the circuits are opened when it engages and moves the arm 119.

In operation the operator follows the same procedure as previously outlined. At the start the movable abutment 122 will be positioned to the left and is holding the

contacts

120 and 121 open against the force of the spring 135, and both sylphon bellows 112 and 113 will be substantially balanced because the temperature of the controlling,

bulbs

115 and 116 are approximately equal. The operator next momentarily presses the start button 129' for its full length which causes contact with the cam surface 124 and such. action shifts the movable abutment 122 along the bar 114 to the light. This action. moves the abutment away from the movable arm 119 and the spring force moves the arm so that the

contacts

120 and 121 carried thereby engage the stationary contacts and closes both the heating element and the motor circuits. Upon energization of the circuits the drive motor 99 causes tumbling of the clothes by rotating the drum 96 and the blower motor 109 draws air from the ambient atmosphere through the inlet 106, circulates the same about the heat exchanger 101 and discharges it into the ambient atmosphere through the outlot 107. At' the same time the heating element 110 supplies heat to the chamber 98 to evaporate the moisture from'the tumbling clothing. The moisture leaving the clotting in the form" of vapor moves toward the heat exchanger, releases its latent heat of vaporization to the air circulating about the tubes 102 and is condensed. The condensate passes to the header 103 and out of the opening 104 for discharge to drain.

As the vapor is condensed the temperature of the air is increased by an amount equal to the latent heat of vaporization plus some of the sensible heat in the condensate. This increased temperature is detected by the bulb 116 at the discharge side of the duct and is reflexed on the bellows 113 which expand against the force of the other bellows 112 responding to the inlet temperature. Since the temperature at the inlet is relatively constant the force of the bellows responding thereto will remain substantially constant, Thus the increased expansion of the bellows 113 compresses the other and moves the bar 114 to the right carrying with it the abutment 122. Prior to attaining the upper limit of the temperature difference, the abutment 122 engages the stationary member 118 and any further movement of the bar 114 to the right merely shifts the relative position of the abutment and bar.

Toward the end of the drying operation the rate of vaporization decreases with the result that the rate of heat absorption of the air decreases, thus the bulb 116 permits the bellows 113 to contract with'the result that the bar 114 carrying the abutment 122 begins to move to the left and approach the movable arm 119. As the temperature of the inlet and outlet air approaches equilibrium the contracting bellows 113 moves the abutment into engagement with the arm 119 and moves the same against the spring force to open the contacts 120 and I 121. This action opens both circuits to deenergize the heating element 110 and stop the drive and "

blower motors

99 and 109, respectively, and the drying operation has been completed, "after which the clothes may 'be removed as previously described.

It at any time the operator wishes to terminate the operation of the drier, the o button 130 is momentarily depressed and the mating cam surfaces force the movable abutment 122 to the left to engage the arm 119 to open the contacts.

In the above disclosed arrangement the timer for initiating and terminating the drying operation has been eliminated. However, it is to be understood that either control arrangement may be applied equally as well to either of the drier modifications shown, and that other modifications of vapor condensing type driers may be provided utilizing controls as outlined above. 7

From the foregoing, it can be seen that control apparatus for a vapor condensing type clothes drier has been provided which is responsive to the difference in temperature of the condensing medium entering the inlet and leaving the outlet of the drier casing to control the duration of the drying operation. Also, that a simplified drier control has been provided which is only dependent upon the quantity and condition of the materials being treated to determine the duration of the drying cycle and is independent of outside extraneous conditions for proper operation. 1

While I have herein described and upon the drawings shown i'llustrative embodiments of the invention, it is to be understood that the invention is not limited thereto, but may comprehend other constructions, arrangement of parts, details and features without departing from the s irit of the invention.

It is claimed:

1. In control apparatus for a vapor condensing type clothes drier, the combination of means for agitating the clothes, a casing surrounding said means to provide a drying chamber, means for heating the clothes in said chamber to evaporate the moisture therefrom, condenser means for receiving a cooling medium for condensing the vapor evaporated from the clothing by absorbing the heat from said vapor, an inlet and an outlet for said cooling medium, a timer for initiating the drying operation, circuit means responsive to a difference in temperature of the cooling medium between said inlet and said outlet, 21 first switch controlled by said timer for conditioning said circuit means for control over said heating means, a second switch controlled by said timer for de-energizing said timer to transfer control of said heating means from said timer to said circuit means, said circuit means operative to transfer control of said heating means back to said timer upon a decrease in the rate of heat absorbed by said cooling medium.

2. A drier for damp clothing, comprising means for agitating the clothes, a casing defining a drying chamber enclosing said means, means for heating said chamber to evaporate the moisture in the clothing, means for conducting a cooling medium over a surface associated with said casing to condense the vapor evaporated from the clothing by absorbing the latent heat of vaporization there from, said last named means including an inlet and an outlet, means for initiating the drying operation and controlling said heating means, a first switch responsive to differences in temperature of said cooling medium at said inlet and said outlet, means controlled by said initiating means for conditioning said first switch for control of said heating means, switch means controlled by said initiating means for transferring control of said heating means to said first switch, said circuit means being operable to return control of said heating means to said initiating means upon a decrease in the rate of heat absorption by said cooling medium.

3. A drier for damp clothing, comprising means for agitating the clothes, a casing defining a drying chamber enclosing said means, means for heating said chamber to evaporate the moisture in the clothing, means for conducting cooling air over a surface associated with said casing to condense the vapor evaporated from the clothing by absorbing its latent heat of vaporization, said means including an air inlet and an air outlet, manually operable means for initiating the operation of said drier, and means including a switch responsive to differences in temperature of the cooling air between said inlet and outlet for maintaining said heating means operative as the outlet temperature of the cooling air increases during the drying operation, and responsive when the difference in air temperature therebetween decreases to terminate the operation of said drier.

4. A drier for damp clothing, comprising means for agitating the clothing, a casing defining a drying chamber enclosing said means, means for heating said chamber to evaporate the moisture in the clothing, a heat exchanger having a portion in direct communication with said chamber, a duct having an inlet and an outlet communicating with the ambient atmosphere surrounding said heat exchanger, means for conducting air through said duct to condense in said heat exchanger the vapor generated in said casing by absorbing its latent heat of vaporization, a switch for controlling the operation of the drier, means for manually initiating the operation of said drier, and differential temperature responsive means responsive to a decrease in the temperature difference of the air on opposite sides of said heat exchanger during the drying operation for terminating the operation of the drier by opening said switch.

5. A clothes drier for drying damp clothing comprising a casing defining a drying chamber for said clothing, means for heating said chamber to evaporate moisture in said clothing, condenser means associated with said casing to condense said evaporated moisture, said condenser means being. provided with an inlet and an outlet for movement of a cooling medium therebetween, manually operable means for controlling said heating means, circuit means responsive to diiterences of the temperatures at said inlet and said outlet for assuming control of said heating means from said manually operable means and maintaining said heating means operative while said evaporated, moisture is condensed by said condenser means, said manually operable means operable to condition said heating means for control by said circuit means, said circuit means being operable to render said heating means inoperative upon a substantial decrease in the rate of condensation of the evaporated moisture.

6. A clothes drier for drying damp clothing comprising a casing defining a drying chamber for said clothing, means for heating said chamber to evaporate moisture in said clothing, condenser means associated with said casing to condense said evaporated moisture, said condenser means being provided with an inlet and an outlet for movement of a cooling medium therebetween, a first cam operated switch for controlling said heating means, circuit means responsive to dilferences of the temperatures at said inlet and said outlet for assuming control of said heating means from said first cam operated switch and maintaining said heating means operative While said evaporated moisture is condensed by said condenser means, a second cam operated switch operable to condition said heating means for control by said circuit means, said circuit means being operable to render said heating means inoperative when the condensation of said evaporated moisture is substantially terminated.

7. A clothes drier for drying damp clothing comprising a casing defining a drying chamber for said clothing, means for heating said chamber to evaporate moisture in said clothing, condenser means associated with said casing to condense said evaporated moisture, said condenser means being provided with an inlet and an outlet for movement of a cooling medium therebetween, a timer, circuit means including a set of contacts, said circuit means being responsive to differences of the temperatures at said inlet and said outlet, a switch, said timer being operable to control said heating means during a first interval and operable to actuate said switch to condition said heating means for operation through said set of contacts during a second interval, said circuit means being operable to render said heating means inoperative at the termination of said second interval upon a substantial decrease in the rate of vapor condensation by said condenser means.

8, A clothes drier for drying damp clothing comprising a casing defining a drying chamberfor said clothing, means for heating said chamber to evaporate moisture in said clothing, condenser means associated with said casing to condense said evaporated moisture, said condenser means being provided with an inlet and an outlet for movement of a cooling medium therebetween, a timer, circuit means including a set of contacts, said circuit means being responsive to differences of the temperatures at said inlet and said outlet, a switch, said timer being operable to control said heating means during a first vapor condensing interval and operable to condition said switch for operation through said set of contacts during a. second vapor condensing interval, said circuit means being operable to render said heating means inoperative responsive to a decrease in the rate of heat absorption by said cooling medium.

9. A clothes drier for drying damp clothing comprising a casing defining a drying chamber for said clothing, means for heating said chamber to evaporate moisture in said clothing, condenser means associated with said casing to condense said evaporated moisture, said condenser means being provided with an inlet and an outlet for movement of a cooling medium therebetween, a timer, a switch, circuit means responsive to thermal difierem tials between said inlet and said outlet, said timer controlling said hcating means during the first interval and conditioning said switch for operation, said circuit means being operable to assume control of said heating means from said timer after said switch has been conditioned for operation, said circuit means being further operable to relinquish control of said heating means to said timer responsive to a decrease in the rate of heat absorption 12 by said cooling medium as the rate of moisture vaporization decreases substantially.

10. A clothes drier for drying damp clothing comprising a casing defining a drying chamber for said clothing, means for heating said chamber to evaporate moisture in said clothing, condenser means associated with said casing to condense said evaporated moisture, said condenser means being provided with an inlet and an outlet for movement of a cooling medium therebtween, a timer, a switch, cooling medium thermal sensing devices near said inlet and said outlet, circuit means responsive to said thermal sensing devices, said timer controlling said heating means during a first interval and operable to actuate said switch to condition said circuit means for dcenergizing said timer and assuming control of said heating means from said timer, a second switch, said circuit means operable to deenergize said heating means and energize said timer upon a substantial decrease in the rate of vapor condensation by said condenser means, said timer being operable to deenergize itself after a timer interval.

11. A clothes drier for drying damp clothing comprising a casing defining a drying chamber for said clothing, an agitator for tumbling said clothing, power means for said agitator, heating means for evaporating moisture in said clothing, condenser means associated with said casing to condense said evaporated moisture, said condenser means being provided with an inlet and an outlet for movement of a cooling medium therebetween, a control for regulating the movement of said cooling medium, a timer, first and second switches, cooling medium thermal sensing devices near said inlet and said outlet, circuit means responsive to said thermal devices, said timer controlling said heating means during a first interval through said first switch and operable to actuate said second switch. to condition said circuit means for deenergizing said timer and for assuming control of said heating means from said timer, said circuit means being operable to render said heating means inoperative and energize said timer upon a substantial decrease in the rate of vapor condensation by said condenser means.

12. In a clothes drier for dry damp clothing comprising a drying chamber for said clothing, heating means tor evaporating moisture in said clothing, condenser means associated with said drying chamber to condense said evaporated moisture, said condenser means being provided with an inlet and an outlet for providing a cooling medium, the automatic control which comprises a first timer switch connected in a circuit for energizing said heating means, a second timer switch, a temperature responsive switch connected in series with said second timer switch, said temperature responsive switch and said second timer switch connected in parallel with said first timer switch, a first timer means for closing said first timer switch to energize said heating means for a first timer interval, a second timer means for closing said second timer switch prior to the end of said first timer interval to energize said heating means through said temperature responsive switch upon the termination of said first timer interval.

13. In a clothes drier for drying damp clothing comprising a drying chamber for said clothing, heating means for evaporating moisture in said clothing, condenser means associated with said drying chamber to condense said evaporated moisture, said condenser means being provided with an inlet and an outlet for providing a cooling medium, the automatic control which comprises a first timer switch connected in a circuit for energizing said heating means, a second timer switch, a temperature responsive switch connected in series with said second timer switch, said temperature responsive switch and said second timer switch connected in parallel with said first timer switch, a first timer cam for closing said first timer switch to energize said heating means for a first timer interval, and a second timer cam for closing said second timer switch prior to the end of said first timer interval 13 to energize said heating means through said temperature responsive switch upon the termination of said first timer interval, means for actuating said first and second timer cams, a third timer switch for energizing said latter means, and manual means for closing said first and third timer switches at the beginning of the timing cycle.

References Cited in the file of this patent UNITED STATES PATENTS 14 2,505,041 Gorsuch Apr. 25, 1950 2,644,245 Hammell et a1. July 7, 1953 2,654,160 Peterson Oct. 6, 1953 2,654,961 Manecke Oct. 13, 1953 FOREIGN PATENTS 979,825 France Dec. 13, 1950 OTHER REFERENCES Frigidaire Service Tech-Talk, vol. III, N0. 8, July 1952, Frigidaire Division, General Motors Corp., Dayton, Ohio. Pages 1-l2 relates to the Model TR-60-Frigidaire Filtra-matic Clothes Drier. Pages 1, 2 and 11 relied on.