US2654160A - Variable time automatic clothes drier and control therefor - Google Patents

Description

Temperotureflf) Oct. 6, 1953 E J. PETERSON 2,654,160

VARIABLE TIME AUTOMATIC CLOTHES DRIER AND CONTROL THEREFOR Filed March 26, 1951 2 Sheets-Sheet 1 Time inuTes) imam M QQIM. I

2 Sheets-Sheet 2 E. J. PETERSON VARIABLE TIME AUTOMATIC CL DRIER AND CONTROL THEREFOR Oct. 6, 1953 Filed March 26, 1951 [m/emor ElmerJ @Zerrozz filzfys.

av uw Patented Oct. 6, 1953 VARIABLE TIME AUTOMATIC CLOTHES DRIER AND CONTROL THEREFOR Elmer J. Peterson, Minneapolis, Minn., assignor to Franklin Transformer Manufacturing Company, Inc., Minneapolis, Minn., a corporation of Minnesota Application March 26, 1951, Serial No. 217,586

Claims. 1

My invention relates to an improved automatic clothes dryer and control therefor characterized by the ability to dry clothes automatically until preset condition of dryness is reached regardless of the drying time required for this purpose.

Automatic clothes dryers are usually operated on a fixed time cycle wherein the dryer is energized for a preset time and then automatically stops. While this type of control frees the operator from attending the dryer at all times, it is subject to the disadvantage that it depends entirely on the judgment of the operator with respect to the time setting. For example, if the operator has great skill in estimating the quantity of clothes going into the machine, the quantity of water entrained in the clothes and the characteristics of the clothes with respect to the difficulty of evaporating the water therefrom, it may be possible to set the timing of the dryer with a considerable degree of success. However, if the operator is like most housewives and can only estimate the time of drying a particular load in a rough way, great variations in the degree of dryness of the clothes are to be expected, some loads coming out of the dryer in an unduly wet condition and other loads being over-dried with the attendant difilculties of ironing and possibility of scorching.

The foregoing difliculties are particularly acute in the case of dryers intended for domestic use, for the average housewife is prone to ignore directions and cannot take measurements of the weight and water content of the clothes and has neither the interest nor the opportunity to develop the skill required for the esoteric art of estimating drying time by mere inspection.

In accordance with the present invention, the foregoing problem inherent in all fixed time dryers is overcome by providing variable time energizing elements sensitive to the degree the clothes are dry and operative to deenergize the dryer when a preset degree of dryness is reached. These elements, operative in response to temperatures at various points in the dryer, sense the condition of the clothes with respect to dryness and can be set to produce the optimum degree of dryness under all conditions of load, thereby eliminating entirely the need for close control, accurate evaluations of the character of the load, and the like heretofore required.

The apparatus of the present invention has the further advantage of being particularly suitable for application to dryers of the type described and claimed in Ralph G. Pugh patent application Serial No. 200,069, filed December 9, 1950, entitled Clothes Dryer. This clothes dryer 2 is characterized by provision of a heater, a drying chamber, an aspirator unit and means forming a closed path for air circulation through these parts in succession and, as described in the aforesaid Pugh application, is particularly efficient in drying.

It is therefore a general object of the present invention to provide an automatic dryer and control therefor capable of drying clothes to a predetermined degree of dryness. Y Another object of the present invention is to provide an improved control mechanism for a dryer of the type having a heater, a drying chamber, an aspirator unit and means forming a closed path for air circulation through these parts in succession and capable of drying clothes to a predetermined degree of dryness.

Further it is an object of the present invention to provide a clothes dryer and control therefor of the variable time type wherein a simple and rugged temperature responsive switch senses the degree of dryness of the clothes.

Another object of the present invention is to provide a clother dryer and control therefor of the variable time type wherein simple switching arrangement establishes the circuit connections required for drying and maintains the same until temperature responsive elements indicate that the clothes are dry and deenergize the unit.

Still another object of the present invention is to provide an improved dryer of the type using an aspirator and air heating means automatically operable to dry clothes to a predetermined degree of dryness and thereafter automatically operable to inject aspirator water until the mechanism cools.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, together with further objects and advantages thereof, will best be understood by reference to the following description taken in connection with the accompanying drawings, in which:

Figure 1 is a view in perspective of a clothes dryer constructed in accordance with the present invention with the cabinet and parts broken away to show the interior thereof;

Figure 2 is a somewhat diagrammatic circuit diagram of the control of the present invention;

Figure 3 is a circuit diagram of an alternative form of the present invention; and,

Figure 4 is a chart showing how the temperature varies in the dryer in the absence of the timing mechanism of the present invention.

Referring now to Figure 1 there is shown at in a tumbling drum for clothes to be dried. This drum has a plurality of inwardly extending paddle blades illa which, as the drum is rotated, aid in causing the clothes to partake of the peripheral velocity of the drum. The end iflb of the drum has a circular opening covered by the screen I2 to permit air travel into the drum in the axial'direction. The drum is supported by a suitable shaft extending backwardly behind end Iflb (not shown) by a plurality of ribs lllc forming a spider with a hub to which the shaft is secured. The forward end id of the drum HI is of annular shape and forms at its center an opening for introducing clothes into the drum or removing clothes from the drum. Heat losses from the drum are reduced by the heat insulation it which is held in place by the metal bands Ma.

The forward central access opening of the drum receives a fixed access tube l5 which, at its upper portion has a rectangular air exit window or aperture lBa An air outlet tube I8 is located over this aperture and extends in slanting direction upwardly and outwardly as shown. At its end, the tube [8 receives the circular aspirator tube which is oriented in parallel relation to the axis of drum l0 and extends backwardly to the separator unit 22.

The separator unit 22 extends downwardly from the rear end of the tube 20 and defines an air passage extending into the header 24 located directly behind the screen l2. This header is of semi-circular shape and extends close to the screen l2 to assure that practically all the air flows directly from the header 2 into the back end of the drum. A semi-circular panel 26 extends downwardly from the front end of the header 24 to seal the portions of screen l2 not located directly over the header 2!.

The above described structure is disclosed and claimed in Ralph G. Pugh application Serial No. 200,069, filed December 9, 1950, entitled Clothes Dryer. Briefly, its operation is as follows:

The drum in is rotated by motor 28 at a speed sufiicient to cause the clothes to ride against the walls of the drum and to fall in a well-defined descending stream straddled by the air flowing axially through the drum. This airis heated by the electric heating element at in the header 24 so as to reach a condition of low relative humidity to form an effective drying medium. The clothes falling through this air are thereby dried.

Air is withdrawn from the drum l0 through the window I611 in the access tube i6 and passes into the duct l8 as shown by the arrows. Upon reaching the end of this duct, the air is struck by the water jet 32 issuing from the aspirator nozzle 34, this jet being derived from the water pipe 36, connected to a suitable source of water under pressure (not shown), through the solenoid valve 38. The aspirator jet drives the air into the tube 20, thus producing the air pressure gradient that drives air through the closed air circulating path to cause it to pass through said tumbling drum, aspirator jet, and heater in succession.

In addition to causing air motion, the jet stream 32 cools the moisture laden air from tube Hi to a relatively low temperature. In this condition, the water content of the air, even when saturated, is quite low and water condenses out on the droplets of the aspirator jet. As a consequence, the air, though saturated at the relatively low temperature of the jet water, has a low actual moisture content.

The saturated, droplet carrying, cool air issues from duct 20- into the separator unit 22. This unit defines a U-shaped vertical air passage which, at its lower end has an abrupt change of direction of air flow from down to up, as shown by the arrows. The heavy droplets of water cannot partake of this abrupt change in velocity and so continue their downward movement to the sump portion 22a of the separator. Pump 40 draws the water from this sump and discharges it to a suitable drain (not shown).

The air, cool and saturated but carrying no entrained moisture travels from the separator 22 into the short duct 42 leading to the header 24. The air thereupon comes into contact with the heater 30 to be heated to a condition of low relative humidity to form an effective drying medium. From this point on the cycle is repeated.

As pointed out in the above-mentioned patent application, the drying unit is highly eflicient in operation, particularly with respect to power consumption when operating at optimum speed, and is suitable for use as a domestic clothes dryer.

Control Heretofore, it has been common practice to provide domestic clothes dryers with timing devices operative to energize the dryer for a predetermined time and then to deenergize the dryer. This type of control is subject to the disadvantage that it does not automatically accommodate the type or condition of the clothes being dried and consequently requires an accurate estimatitan of the required drying time as the unit is se The apparatus of the present invention differs from the fixed-time control heretofore used in providing a variable time control sensitive to the condition of the clothes being dried. In the form shown in Figures 1 and 2, this unit includes a pair of thermostats, one (the cut-off thermostat), indicated generally at 44, being responsive to the temperature of the saturated air as it leaves the duct 20 and the other (the setting thermostat). indicated generally at 46, being responsive to the temperature of the air as it enters the tumbling drum [0. The thermostat 46 serves to maintain the unit in the on condition until the air temperatures reach normal drying values. The thermostat 44 then takes over to maintain dryer operation until its temperature falls below a preset value indicative of the end of the drying cycle.

It has ben found that with the drying cycle of the dryer of Figure 1, the temperature of the air entering the header 24 falls when the moisture has been removed from the clothes. This temperature is believed to fall because the water of jet 32 evaporates as required to bring the air in duct 20 to a saturated condition, an effect that requires evaporation of a greater quantity of water when the air from duct I8 is drier than when it is wet. Moreover, the specific heat of the dry air entering the aspirator chamber when the clothes are in a relatively dry condition is less than that of the relatively wet air when the clothes are not dry. Since this evaporation requires heat, the temperatures of the air at the outlet of duct 20 falls and a corresponding drop is sensed by the thermostat 44.

The circuit diagram of Figure 2 shows the circuit arrangement for achieving variable time automatic drying. Alternating voltage from a suitable source (not shown) is applied to the three terminals 48, 50, and 52 of a conventional three wire system wherein volts, for example, appears across terminals 48 and 50 and across terminals 50 and 52, and 220 volts appears across terminals 48 and 52.

The heater 30 is connected across terminals 48 and 52 by the solenoid operated connector 54. When the solenoid 54a is energized, the circuit for this purpose may be traced from terminal 52, through conductor 52a, and contact elements 54b, to the heater 30. The opposite end of the heater is connected to terminal 48 through conductor 48a and contact elements 54c. A high temperature operated switch 56 is provided to interrupt the energizing circuit to heater 30 if the air temperature exceeds a preset value. This switch may, for example, be located in the duct 42 as shown in Figure 1. Since this element is well known in the art and many wellknown devices may be used for this purpose, it is not shown in detail.

The motor 28, and the water valve 38, Figures 1 and 2, are energized by two circuits, one traceable from terminal 48, through conductors 48b and 48c'to thermostat 48 and from that thermostat through motor 28 and valve 38 to terminal 50. The other circuit may be traced from terminal 48, through conductors 48b and 48d and contactors 54d, to motor 28 and valve 38 and then to terminal 50. The motor and valve are energized through the latter circuit to initiate operation and through the former circuit during the later part of the clothes drying operation.

The solenoid 54a is energizable through two circuits. One circuit, used for starting, can be traced from terminal 48, through thermostat 48 (which in the low temperature starting condition has the dotted line position of Figure 2), stop switch 58, solenoid 54a, and start switch 80, to conductor 50a and hence to terminal 50. The solenoid 54a is also energized through the sealin circuit traceable from terminal 50', through contactors 54e to solenoid 54a, and through stop switch 58 to thermostat 44 or 46, conductor 48c, and conductor 48b to terminal 48.

The thermostat 46 is of the type operative to close at one temperature, say 89 C., to the position shown in the solid lines of Figure 2 and to open to the dotted line position at a substantially lower temperature, such as 69 C. One way to accomplish this relatively wide dead band while achieving positive contact-making is by the use of the over-center bimetal 48a and a compression spring 46b which biases the bimetal in a general longitudinal direction. The bimetal and the spring coact to form a toggle which cannot be driven over-center to the opposite position until a substantial force is exerted, a condition requiring a substantial temperature change and, when once driven over center positively moves to contact-making position. Other methods of achieving a wide dead band may, of course, be used. I

The thermostat 44 is a make or break type thermostat of the bulb type. The sensing bulb 44a is positioned in the separator 22 adjacent the outlet of duct 20 and is connected by tube 44b to the control unit 62, Figure 1. This unit includes switch arm 44d with which bellows 44e coacts to make contact when the temperature of bulb 44a is above a preset value. The switch arm engages the fixed arm 441 in the contactmaking position, the position of arm 44f being determined by the adjusting knob 440 to set the degree of dryness to be imparted to the clothes. Other thermostat devices, operative to open. circuit when a predetermined low temperature exists may be used as the thermostat 44.

As is described in further detail hereafter, the thermostat 44 acts as a shut-off switch.

The switch 48, Figure 2, is closed by closure of the door of the dryer. the indicator light 49a. The unit is protected by fuse 5| which may, for example, be a 10 ampere fuse.

Operation Operation of the mechanism of Figures 1 and 2 is as follows:

When the unit is in a shut down condition and start button is closed, the solenoid 54a is energized through switch 48 by connection across terminals 48 and 50. The solenoid then seals in through the contacts 54c which bridge the start button 80 which, upon release, opens.

When the solenoid 54a. picks up, motor 28 and valve 38 are energized from terminals 50 and 48 through the thermostat 46 and the contactors 54d. The heater 30 is energized from terminals 48 and 52 through the contactors 54b and 540. The dryer accordingly commences operation, with the drum l0 rotating, water being emitted from the jet 34, and the heater 3!] being energized.

As the dryer continues operation, the temperatures in the system rise until the temperature sensed by the bulb 44a exceeds the value between 30 C. and 50 C. to which the knob 440 is adjusted. At this time, the thermostat contact plate 44d swings from the dotted position of Figure 2 to the contact-making solid position, thus estab lishing a circuit in parallel with the thermostat 48 for the energization of the solenoid 54a.

As the system temperature continues to rise, the temperature sensed by thermostat 4B exceeds the value of 89 C. to cause that thermostat to snap from the dotted position to the solid position of Figure 2. In the solid position of Figure 2, the thermostat breaks its parallel circuit across the thermostat 44 and establishes an energizing circuit from terminal 48 to motor 28 and valve 38 independent of contactors 54d.

As the temperature at the outlet of the drum l0 continues to rise, the high temperature cutout thermostat operates to prevent temperature in excess of a safe value. Since this merely interrupts the circuit to heater 30, it does not otherwise alter the operation of the system.

During the operation described above, the clothes are in process of being dried and the rate of moisture removal is determined primarily by the drying ability of the air introduced into drum l0. The temperature sensed by the thermostat 44 is above the set value between 30 C. and 50 C. and the switch remains closed. However, when the water is removed from the clothes, the rate of water removal falls and is reflected in reduced humidity of the air in duct l8. This causes the temperature sensed by thermostat 44 to fall and eventually drop below the value (between 30 C. and 50 C.) to which this thermostat is set. The thermostat thereupon drops out to open the circuit to solenoid 54a and cause drop-out of the contactors 54b to Me, inclusive. The heater 30 is then deenergized.

Upon drop-out of the solenoid operated switch 54, the motor 28 and valve 38 remain energized through the thermostat 48. This condition continues until the temperature falls below the low temperature limit of this thermostat (i. e., 69 C.).

The circuit shown diagrammatically in Figure 3 is a modification of that of Figure 2 wherein a This switch energizes aeuaao timer I is substituted for the thermostat ii. The timer 6 is a single pole double throw switch exactly like thermostat 46 and connected in the same circuit relation. However, it operates on a fixed time cycle to maintain the contact position shown by the dotted lines, Figure 3, for a predetermined period and then to shift to the solid position for a second predetermined period. The first period is sufficiently long to raise the temperature of thermostat 44 to contact making position and the second is sufficiently long to exceed the time required for drying and the after-operation of the motor 28 and valve 38 to cool the unit.

The timer may be any one of many constructions well known in the art and forms no part of the present invention. Its fixed contact arm M61) is connected to the common terminal of motor 28 and valve 38 by conductor 6c, Fig.- ure 3.

Figure 4 shows in chart form the variations in temperature in the dryer when it is operated without the controls of the present invention. In this figure, curve A represents the temperature of the air entering the drum which is the temperature sensed by the switch 46, Figure 1. The curve B is the temperature of the air entering duct l8, that is, the air entering the spray unit, The curve C is the temperature sensed by the bulb 44a, Figure 1, that is, the temperature of the air as it leaves the spray chamber.

It will be observed from Figure 4 that the temperature of bulb 44a rises from about 20 C. to a. peak value of almost 40 C. during the first 25 minutes of operation. However, this temperature falls after reaching this peak value and by the time 55 minutes have elapsed, is well below 30 C. Consequently, if the thermostat 44 is set to deenergize the unit at, say, 30 degrees, as indicated by the heavy dashed line, Figure 4, the

unit will be deenergized after about minutes operation.

Experiment has shown that the droop of the curve C after reaching the peak value is determined by the water content of the clothes being dried and that the temperature value at any time is a measure of the degree of dryness of the clothes. While applicant cannot state positively the reason for this temperature variation, it is believed to be due to the decreased moisture content of the air entering duct l8 as the clothes are dried. When the clothes are wet, the water evaporated from them appears as increased humidity of the air in duct IS with the incident increased specific heat of the air. The cooling associated with operation of the spray 34 is accordingly less than it would be if the air contained less moisture and hence had smaller specific heat.

In the appended claims I have used the term aspirator unit to describe generally the apparatus downstream of the aspirator nozzle 34 and extending to the heater 30. The thermostat 44 may be placed at any point in this region to sense the degree of dryness of the clothes in tumbling drum [0, although the location shown in Figure 1 is preferred.

From the above description it will be apparent that I have provided an improved automatic clothes dryer which is energized in a time cycle of duration determined by the degree of dryness of the clothes and needs no presetting other than that of the knob c which fixes the degree of dryness at which the unit cuts oii. Moreover, the unit of the present invention is suitable for use with the closed, efficient, automatic dryer of Ralph G. Pugh patent application Serial No. 200,069, entitled Clothes Dryer.

It will be observed that the switches 45 and I46 act as conditioning switches to maintain initial operation of the dryer until the thermostat 44 comes up to temperature.

In the appended claims the words jet cooling unit are used to designate a water spray type unit which directly exposes water to the air stream. While the specific jet shown at 3 is also an asplrator, this is not necessary to the operation of the unit.

While I have shown and described specific forms of the present invention, it will of course be understood that many modifications and alternative constructions may be made without departing from the true spirit and scope thereof. I therefore intend by the appended claims to cover all modifications and alternative constructions falling within the true spirit and scope of the appended claims.

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

1. In a clothes dryer comprising a heater, a drying chamber, means for injecting a .cooling liquid, and means forming a closed path for circulating air through said elements in the above order; the mechanism comprising: a first switch means responsive to the temperature of the air in said drying chamber, a second temperature responsive switch means located downstream of the cooling liquid injecting means with respect to the air fiow past said liquid injecting means, and means defining an energizing circuit through said switch means and heater, said first switch means being operative through said circuit to energize the heater independently of the second switch means until a predetermined temperature is reached and being then operative to establish an energizing circuit through the second switch means and the second switch means being operative through said circuit to interrupt the energizing circuit of the heater when the temperature falls.

2. In a clothes dryer comprising a heater, a drying chamber, means for injecting a cooling liquid, and means for circulating air through said elements in the above order; the mechanism comprising: means defining an energizing circuit for the heater; a switch in said circuit to open or close the same; and elements responsive to the temperature downstream the point of cooling liquid injection operative to open the switch when that temperature falls below a preset value.

3. In a clothes dryer comprising a heater, a drying chamber, means for injecting a cooling liquid, and means for circulating air through said elements in the above order; the mechanism comprising: means defining an energizing circuit for the heater; a switch in said circuit to open or close the same; and elements responsive to the temperature downstream the point of cooling liquid injection operative to open the switch when that temperature falls below a preset value; and switch means shunting said first switch, and elements operative when set to close said last switch means independently of said first switch until the temperature in the drying chamber exceeds said preset value.

4. In a clothes dryer comprising a heater, a drying chamber having a clothes tumbler with a drive motor, means for injecting a cooling liquid, and means forming a closed path for circulating air through said elements in the above order: means defining a first energizing circuit for the motor and heater; means defining a second energizing circuit for the motor only; a twoposition switch operative in one position to close said first circuit; and in the other position to close said second circuit; means responsive to the temperature in said drying chamber operative to move said switch from said one position to said other position when the temperature exceeds a predetermined value; a second switch connected in electrically parallel relation to the first switch when in said one position; and means operative to open said second switch when the temperature downstream the point of injecting cooling liquid exceeds a predetermined value.

5. An automatic dryer for clothes and the like comprising in combination: a heater; means defining a clothes drying chamber; means for injecting a cooling liquid; means for circulating air through the heater, the chamber, and said means in the above order; means defining an energizing circuit for the heater; a switch in said circuit to open and close the same; and elements responsive to the temperature downstream the point of cooling liquid injection operative to open the switch when that temperature falls below a preset value.

6. An automatic dryer for clothes or the like comprising in combination: a heater; means defining a clothes drying chamber; means for injecting a cooling liquid; means for circulating air through the heater, the chamber, and said means in the above order; means defining an energizing circuit for the heater; a first switch means in said circuit and responsive to the temperature of the air in said drying chamber; a second temperature responsive switch means in electrical parallel relation with said first switch means, said second switch means being located downstream of the cooling liquid injecting means with respect to the air fiow past said liquid injecting means, said first switch means being operative through said circuit to energize the heater independently of the second switch means until a predetermined temperature is reached and the second switch means being operative through said circuit to interrupt the circuit when the temperature at said second switch means falls. 4

7. An automatic dryer for clothes or the like comprising in combination: a heater; means defining a clothes drying chamber; means for injecting a cooling liquid; means for circulating air through the heater, the chamber, and said means in the above order; means defining an energizing circuit for the heater; a setting switch in said circuit; means responsive to the temperature in the drying chamber and having a relatively large dead band operative to open the setting switch when said temperature rises to a predetermined value; a cut-off switch in electrical parallel relation to the setting switch; means responsive to the temperature downstream the cooling liquid injecting means operative to move the cut-off switch to oil. position when said temperature falls below a predetermined value.

8. An automatic dryer for clothes or the like comprising in combination: a heater; a clothes tumbling drum; means for injecting a cooling liquid; means for circulating air through the heater, the drum, and said means in the above order; a motor operative to rotate the drum; means defining an energizing circuit for the heater and the motor; a setting switch in said circuit having an on position and an off position;

' means responsive to the temperature in the drum and having a relatively large dead band operative to move the setting switch to off position when said temperature rises to a predetermined value; a cut-off switch in electrical parallel relation to the setting switch when in the on position; means responsive to the temperature downstream the cooling liquid injecting means operative to move the cut-off switch to oil position when said temperature falls below a predetermined value; and means defining an energizing circuit for said motor through the setting switch in the off position.

9. In combination, a clothes tumbling drum; means defining an air duct external to said drum and forming a closed air circulating path in conjunction therewith; means to inject an aspirating spray of cooling liquid into said duct; means located downstream of said last means to remove condensed moisture from the air; a heater located downstream said last means; a motor operative to rotate the drum; means defining an energizing circuit for the heater and the motor; a setting switch in said circuit and having an off position and an on position; means responsive to the temperature in the drum and having a relatively large dead band operative to move the setting switch to off position when said temperature rises to a predetermined value; a cut-oiT switch in electrical parallel relation to the setting switch when in the on position; means responsive to the temperature downstream the means to inject the aspirating spray operative to move the cut-oif switch to off position when said temperature falls below a predetermined value; and means defining an energizing circuit for said motor through the setting switch in the oil position.

10. In combination, a clothes drying container;

means defining an air duct external to said container and forming a closed air circulating path in conjunction therewith; means to inject an aspirating spray of cooling liquid into said duct; means located downstream of said last means to remove condensed moisture from the air; a heater located downstream said last means; means defining an energizing circuit for the heater; a switch in said circuit having an ofi position and an on position; and means to move said switch to of! position when the temperature downstream said means to inject the aspirating spray falls below a predetermined value.

ELMER J. PETERSON.

References Cited in the file of this patent UNITED STATES PATENTS Number

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