US3122426A

US3122426A - Laundry dryer control mechanism

Info

Publication number: US3122426A
Application number: US119973A
Authority: US
Inventors: Stanley V Horecky
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1961-06-27
Filing date: 1961-06-27
Publication date: 1964-02-25
Anticipated expiration: 1981-02-25

Description

Feb. 25, 1964 s. v. HORECKY LAUNDRY DRYER CONTROL MECHANISM 2 Sheets-Sheet 1 Filed June 27, 1961 FIG. 3

FIG. 4

INVENTOR. STANLEY V. HORECKY BY MW ATTORNEY Feb. 25, 1964 s. v. HORECKY 3,122,426

LAUNDRY DRYER CONTROL MECHANISM Filed June 27, 1961 2 Sheets-Sheet 2 0 u N TLZ lb-III I FIG. 6

INVENTOR. STANLEY V. HORECKY ATTORNEY United States Patent O 3,122,426 LAUNDRY DRYER CONTROL MECHANISM Stanley V. Horecky, Oak Park, Ill., assignor to General ElectricCompany, a ccrporation of New York Filed June 27, 1961, Ser. No. 119,973 13 Claims. (Cl. 34-45) This invention relates to laundry dryers and more particularly to mechanisms for controlling the operative cycle of these dryers.

The art contains numerous examples of controls to provide a fully automatic dryer; that is, a dryer having a simplified control which could be set at the start of the operation and would continue the drying until a sensing mechanism determined that the laundry was dry. In most forms of these controls,- the dryness of the laundry was estimated by sensing various physical conditions within the drum. Some sensed the exhaust air temperature and reacted to changes beyond a predetermined amount. Others sensed the moisture content of the exhaust air and ended the cycle when this moisture content decreased. However, it is difllcult, in the practical sense, to correlate air temperature or humidity to actual clothes dryness, and most contemporary systems of clothes dryer control, in which drying operation is terminated when such a physical condition has reached the control point, are at best, only of an approximating nature. It would appear to be more reasonable to sense the actual moisture condition of the laundry within the drum. In US. Patent 2,820,304, issued on January 21, 1958, to the present inventor, there is shown one form of mechanism for approximating the actual moisture content of the laundry being dried. The present invention provides improved means for actually sensing the moisture content in the laundry, and to an improved control circuit for evaluating the apparent moisture content and terminating the dryer operation as required.

It is therefore an object of the invention to provide an improved laundry dryer control which directly senses the dryness condition of the clothes being dried.

It is a further object of the invention to provide a mechanism with a plurality of moisture-sensing electrodes dispersed about the periphery of the drum to maintain the dryer in operation until the clothes have attained a desired condition of dryness.

Other objects, features and advantages of the invention will become apparent with reference to the following specification viewed with the accompanying drawings in which: g

FIG. 1 is a perspective View of a dryer utilizing my invention, with the cabinet shown in phantom View and portions of the drum, etc., broken away to reveal otherwise concealed structure;

FIG. 2 is a schematic side sectional view of the dryer of FIG. 1 to illustrate air movement therein;

FIG. 3 is a side sectional View of the drum interior;

FIG. 4 is a front sectional view of the drum;

FIG. 5 is a schematic diagram of a control circuit for the dryer;

FIG. 6 is a partial section of the drum sidewall;

FIG. 7 is a partial view from the rear of the slip ring arrangement; and

FIG. 8 is a front view in detail of the control knob of FIG. 1.

In FIG. 1 is shown a dryer 10 having conventional means for circulating air through the clothes as they tumble within the drum. It will be understood, however, thatthe invention is not restricted to any particular air circulation or drying means, for it is the dryness of the clothes load itself, and not the physical condition of the circulating air, which is determined by the present invention. A conventional cabinet 12 has front, top, side 3,122,426 Patented Feb. 25, 1964 and rear walls. An access opening 14 is provided in the front wall, the opening being covered by a side hinged door 16 shown in the closed position in FIG. 2. At the top rear of the cabinet is mounted an enclosed control area 18 in which the necessary electrical controls are fitted. Extending forwardly from this area are the manually manipulatable control knob 19 and a multiple selection switch 20. This switch has a plurality of pushbuttons whereby the operator may select low heat upon pushing button 20.1, high" heat by pushing button 20.2, and no heat when it is desired merely to fluif the clothes by tumbling them in the absence of heat. Switch 20 may advantageously be of the type disclosed in'Andrews US. Patent 2,431,904, granted December 2, 1947. In such a switch, pressing one button will operate any previously-pressed button to return to an unoperated position. The switch 99 (FIG. 5) operated by button 20.3is opened when the button 20.3 is pressed, and returns to closed condition when the button is projected, whereupon pressing either button 20.1 or 20.2 will complete a heater circuit. Operating button 20.1 will open switch 98; operating button 20.2 will close switch 98.

Within the dryer cabinet there is included a drum 22 rotatable on a horizontal axis. Consistent with the illustrated air circulation system, the sidewall of the drum is imperforate. Spaced about the sidewall 23 are the inwardly directed, substantially triangular, lifting vanes 24, each of which extends for the entire axial length of the sidewall. The rear wall 26 of the drum is perforated to allow passage of air into the drum and at the front of the drum there is a circular opening 28 in registry with the cabinet opening to afford access to the drum interior. Consistent with contemporary practice, the drum will have a vitreous enamel coating, and, therefore, the inner surface of the drum will be electrically non-conductive.

To dry laundry being tumbled within the drum, a stream of heated air is circulated through the drum axially. This air receives moisture from the laundry being dried. The air circulation system includes in the cabinet rear wall a plurality of air inlet openings 30 which may be louvered as shown. A louvered circular heater casing or shroud 32 envelops the rearend of the drum and is mounted stationarily to the cabinet structure. Within the shroud are afiixed a plurality of

concentric heater elements

34, 34a, illustratively comprising helically wound resistance wire in heat exchange relation with air passing thereover. The electric heaters merely typify a heating system; gas-burning heaters, under control of a conventional electrical control device such as a relay or solenoid, may be used without departure from the invention, as Will be later apparent.

Air circulation is enforced by a suction producing network which induces air flow into the drum. Air leaving the front opening of the drum enters the exhaust ducting system at the entrance 36 at the bottom of the inter-space between the drum and the cabinet. This entrance may lead through a conventional lint filter (not shown) to a downwardly directed duct 38 and into the blower chamber 49 from which the air enters a duct which conveys the exhaust air out the rear of the cabinet.

The blower chamber 40 includes an air impelling rotor 41 of conventional design and driven by the drivemotor 42 which is common to the fan and the drum drive mechanism, which may comprise any conventional power transmission system, such as a belt and sheave system (not shown). At the front the drum may be cradled on suitable resilient rollers 44 adjacent the drum access throat 46. Further the drum is maintained in its fixed rotating pattern by means of an axial stub shaft 48 secured concentrically to the drum rear wall and maintained rotatably in suitable stationary bearings mounted on the cabinet rear wall.

The structure described to this point is quite conventional and is illustrated in many patents of the prior art. The present invention resides in the control mechanism for the dryer which will now be described. As shown in FIG. 3, circularly disposed about the interior of the drum sidewall are four pairs of parallel electrodes 51. These electrodes which may be considered as bare wires are insulated at all points from contact with the adjacent sidewall by imbedding the wires in suitable strips 52 of heat and moisture resistant, and electrically insulating materials such as the presently known silicones.

Each of these wires describes a single circular loop within the circular sidewall. lllustratively, there are eight parallel loops about the sidewall arranged in four pairs, respectively identified as al, a2; b1, b2; 01, c2; and (ill, One of the ends of each loop is dead ended; the other end is multipled to the corresponding end of the loop once removed from the loop in question. In short, every other loop has one end connected in multiple as shown in FIG. 6. One end of loops al, bl, cl and (ii is connected in multiple and is connected to slip ring 6t The otier multiple from loops (12, b2, c2 and d2 is connected to outer slip ring as. These slip rings may be of any conventional design which allows good electrical contact from an annular rotating conductor to a con ductor connected to a brush riding on the slip ring. The respective brushes, 64, 66 may be mounted from the shroud 32 by suitable insulated supports. The leads from

brushes

64 and 66 are connected into a moisture content sensing circuit (FIG. The circuit is connected to a conventional Edison three-wire source to provide 236 volts across leads L1 and L2 and 118 volts across the intermediate lead N and either one of the outer leads L1 or L2.

Within the circuit of FIG. 5, there is shown a conventional timer motor 7% which may be set manually by manipulation of knob 9 for either a normal timed operation or automatic dry (see FIG. 7). The timer controls a plurality of switches which are operated by cams C1C4 positioned to be rotated by the timer motor and having associated therewith springs which are actuated or released at specific times by the cam action. Such timers are well known and understood by those skilled in the art. Specifically, there is a first set or" switch contacts '72 which control the operation of the timer motor and are closed when the operator wishes to operate the dryer on a purely time basis. As is well known, the knob 1% is rotated manually to the desired registry of the

minute markings

15, 30, 45, etc., with the index 13, whereupon the switch 72 will close and remain closed until the selected time has elapsed, whereupon the dryer operation will terminate. A second set of contacts "/4 serve to connect the automatic sensing network onto the power source when automatic drying is selected. A third set of cam-controlled contacts 76 serve to complete the operating path to the drive motor and must be closed for operaing the drive motor during the timed dry period. A final set of contacts 78 complete a path to the heating units 34 and 34aof heater shroud 32. In the circuit to lead Ll, there can be seen a motor-operated switch 82 which is closed whenever the drive-motor 42 is running at its operating speed and opens the circuit to the heaters on slow down of the motor. Further in series with switch 82 is the operating thermostat 84. Thermostat d4 serves to cycle the heater or heaters during the operative cycle to maintain the air temperature of the drum at a fairly constant level. In the line connection from L2 there can be seen a conventional door switch d6 which opens the line circuit to the drive motor, the timer motor and the heaters on opening of the door. A second set of contacts 86.1 of door switch 86 is connected in the Lil side of the heaters so that both sides of the heater circuit are opened on opening of the door. A high temperature or shut-off thermostat 88 is placed in series with the door switch to shut down the machine on occurrence of a high temperature in the dryer.

The drive motor 42., having the usual start winding 90, run winding 92 and centrifugal switches 32 and 94, is connected between the neutral conductor N and contacts of momentary or safety start switch 95 to obvious circuit components leading to conductor L2. Momentary switch 95 also includes a second set of contacts 97 which are effective in the automatic drying cycle, as will be explained in detail. This switch must be depressed to start the cycle and releases on release of finger pressure by the operator. If the dryer is shut ofi in mid-cycle, switch 9 5 must be depressed for reset. The regular operating circuit also includes a low-temperature setting switch 98 which is opened when the temperature at which the machine is to be operated is set at low temperature. With switch 98 open, the energizing path to heater coil 34:: is opened and only heater 34 remains in the circuit. To allow the clothes to be fiuif-dried (tumbling in the drum with no heat) a fiutl-switch 99 may be provided. When the operator presses control panel button 241.3, this switch 99 opens the circuit to the heaters and this switch will remain operated until released by pressing either of the buttons 2611 or 20.2, as earlier explained.

The automatic drying circuit includes among its components a pair of relays. A first relay 100 is of the marginal electromagnetic type and is quick to pull in, and slow to release. This relay controls its normally open contacts 162, 31M and 106 to close these contacts on operation in the generally known manner. For example, relay 106* may require only about a millisecond of energization for it to operate. The circuit to relay coil 101 includes a capacitor 168 which tends to speed the operation and to slow the release of the relay. Capacitor lili maintains the relay to hold its contacts closed for about ten seconds after cessation of the relay-energizing pulse. The second relay lid is oi the type which closes its contacts 1.12 and 114- after about five seconds of energization of its coil lid and remains operated with its contacts closed for about two minutes after the power has been interrupted to the relay coil. Relay 116' may be a conventional resistance coil-heated bi-metal type which operates its contacts on heating of its coil and releases these contact after its coil circuit has been interrupted for two minutes. The circuit further includes a rectifier I i-6 connected serially through capacitor 168 and current limiting resistor 11% to the electrodes via

brushes

64, 66 and slip rings ea, 62. This circuit serves to supply half wave rectified direct current for energizing the relays, etc. Further there is provided a switch 124- which is operated to either of two circuit closing positions as the knob d9 is turned from its ofi designation to either the dry or the damp dry indexes of the knob. A glow-discharge device such as the neon bulb 126i is connected to a resistor 1'22 and then directly to contact 128 of switch 124, or by Way of the resistor 126, to contact 129' of said switch. It is obvious from HG. 5, that either resistor 122 or both

resistors

122 and 126 are connected between relay ltltl and ground, according to whether the relay coil is in circuit with contact 3123 or contact 129 of switch 124-. As presently appears, this will be determinative of the end clothes condition which will shut ed the dryer. The switch 124 would be closed to contact 128 for automatic drying to the bone dry clothes condition, and to the 129 contact if a damp-dry condition is required.

The following table states the operating condition of the respective cam-operated switches in the time-dry and automatic dry control knob settings:

Cam Switch 'lime Dry Automatic Dry C1 72 Closcd Open. 76 Closed Open. 78 Closed..- Open. 04 74 Open Closed.

Timed drying of the system is quite conventional and operates as follows: Knob 19 is rotated to the position indicating timed drying and is set at the time required for drying the'load in question. The manual rotation of the knob rotates cams C1, C2 and C3 to close their associated cam-operated

contacts

72, 76 and 78. At contacts 72, the timer motor 78 is closed to the ll8-volt source over a path which can be traced from lead L2, through the closed door switch 86, high limit thermostat 88, closed contacts 72, timer motor 70 to lead N and ground. The timer then starts its operation of returning the output carn shaft 73 to the Off position at a fixed rate in a generally known manner.

Nothing further will occur until the momentary start switch 95 is depressed

closing'its contacts

96 and 97. Contacts 97 have no eifeot during this timed operation and their closure may be ignored. At contacts 96, the drive motor 42 windings are energized over a path which may be traced from ground at lead N through the parallel windings (start winding 90 and run winding 92), the normally closed upper contacts of centrifugal switch 94, contacts 96, closed timer contacts 76, to the high limit thermostat 88, and closed door switch 86 to lead L2. The motor 42 accelerates rapidiy and centrifugal switch 82 closes :and switch 94 closes on its lower contacts. This opens the start winding circuit, and the motor continues on the run winding 92 through conductor 130 and timer contacts 76. As contacts 82 close, heater 34 alone (if low heat has been selected) or both

heaters

34 and 34a it high heat switch 98 has been closed, are energized. The heater. circuit may be followed from lead L1, through motor switch contacts 82, thermostat 84, door switch contacts 86.1, heater 34, normally closed contacts 99, cam contacts 78, thermostat 88, and closed contacts 86 to lead L2. If high heat is required, high heat switch 98 is closed by manual operation of switch button 201 on control panel 18 to place heater 34a in parallel with heater 34. With either temperature selection, thermostat 84 cycles to maintain the temperature in the dryer relatively constant by shuttingoif the heaters on reaching a predetermined high temperature and energizing the heaters on the air in the dryer reaching a preset low temperature, as is well known in the art. The drying cycle continues in this manner until the selected timed period approaches completion, at which time cam contacts 78 open deenergizing the heaters and allowing the drum to rotate for a cool down period which may be of five minutes duration or less. At the conclusion of this period,

contacts

72 and 76 open their respective circuits and the dryer is shut off. i I d For automatic drying there is a choice of damp dry or bone dry; the operation in either instance is virtually identical. In operating the machine for bone-dry clothes, the control knob 19 is rotated until 1 the section marked Dry-A-utomatic is positioned under the positioning arrow 13 (FIG. 8). Movement of the knob to this position closes contacts 74 of cam C4 and operates the automatic dry switch 124 to close against its contact 128. This closure completes a path to neon lamp 120 over a circuit from lead L2 through door switch contacts .86, high temperature thermostat 88, contacts 74, rectifier 116, winding of relay 100, switch

contacts

124, 128, resistor 122, and to ground. Lamp 120 then fires to indicate the circuit is prepared for automatic drying. This closure also completes a resistive circuit to relay 100, but the combined eifect of the half wave current passing through rectifier 116, the capacitive effect of capacitor 108, the resistance of resistor 122, and the marginal adjustment of the relay combine to keep the relay from operating at this time. Cam C1 is so arranged that when the knob 19 is rotated to either of its automatic settings, contacts 72 are not closed, hence no timing occurs with p the knob 19 in this position. Contacts 74 remain closed I for the duration of the automatic drying period.

Shortly after knob 19 is positioned to automatic dry, and neon bulb 120 has fired, momentary start switch 95 v 6 is depressed closing its

contacts

96 and 97. Contacts 96 serve no useful function for automatic dry but contacts 97 on closure initiate the sequence of operations to provide automatic dryness sensing. Momentary closure of switch connects the grounded N lead through contacts 97, conductor 103 contacts 128 of switch 124 through the winding 101 of relay and conductor to rectifier 116, contacts 74, thermostat contacts 88 and door switch contacts 86 to lead L2. This closure shunts out resistor 122 and neon lamp so that these components are no longer effective. Lamp 120 then ceases firing to (indicate the automatic cycle has begun. Relay 100,

being of the quick-to-operate type, operates on receipt of the ground pulse from contacts 97 and will remain operated for a period of ten seconds following cessation of its operating pulse. On operation, relay 100 closes its

contacts

102, 104 and 106. Contacts 102 complete a circuit from lead L2 for the motor run circuit, and the motor begins operation at once. Contacts 104 on closure complete a circuit to energize time delay relay 110. This operating path for relay 110 may be traced from ground at lead N through relay winding 111, closed contacts 104, thermostat 88, door switch contacts 86 to lead L2. Aiter a delay of about five seconds (relay 100 once having operated thus maintaining its contacts 104 closed for ten seconds) relay lltloper-ates closing its

contacts

112 and 114. At contacts 112, a parallel circuit is closed for operation of the drive motor 42, said circuit maintaining motor operation following the opening of relay contacts 102, as presently explained. This circuit may be followed from lead N through motor start winding 90 and motor-run winding 92 in parallel, conductor 115,

closed contacts

112 and 74 to thermostat contacts 88, door switch contacts 86 and lead L2. Contacts 114 on closure act to ground the wetness sensor conductor, which as mentioned previously includes the electrodes a1, a2, b1, b2, etc.

It should be noted at this point that there must be wet laundry in the drum for the operation of the circuit to continue for more than two minutes. With Wet laundry in the drum, a circuit is closed from ground through closed contacts 114, brush 66, slip ring 62 to electrodes a2-d2. With wet laundry anywhere in the drum distributed in virtually any random fashion there will be a closed circuit from electrode al-dl multiple to electrode a2d2 multiple. This closure will serve to connect the previously mentioned ground at contacts 114 through slip ring 60 and brush 64, contacts 128, relay 100,-rectifier 116 and closed contacts-74 to the L2 side of'the line. Release of the relay 100 is further slowed by the R-C action of capacitor 108 and resistor 118 which aids in maintaining relay operated by the resistance capacitive shunt across the relay. This capacitor cyclically charges and then discharges across the relay 100 aiding the normal operating path in maintaining the relay operated. Relay 100 inturn maintains relay 110 operated so that the two relays lock eachother operated through the sensor electrodes and the wet laundry in the drum.

The motor accelerates and closes contacts 82 and the lower contacts of switch 94. Switch 94 therefore closes to lead 130, deenergizing the start winding. Run winding 92 is energized from lead N through

closed contacts

102, 112 and 74 to thermostat contacts 88, door switch contacts 86 to lead L2. On closure of motorspeed contact 82, the heater 34 is energized over a path from lead L1, through contacts 82, thermostat contacts 84, door switch contacts 86.1, heater coil 34,

contacts

99, 106, 104, thermo-, stat 88, and door switch 86 to lead L2. As with timed drying, thermostat 84 cycles the heater to maintain a relatively constant air temperature in the drum throughout the drying cycle.

During the drying cycle, the drum tumbles at a nominal tumbling speed of 50 rpm. or approximately one and onedifth seconds per revolution. Thus the drum will complete about eight revolutions during a ten-second perlod. During these eight revolutions, the electrode multiples must be shorted or the circuit must be closed with a low internal resistance at least one time in order to provide relay till? with the necessary operating ground. During the early part of the drying operation, the relay lttl will receive many more than the amount of pulses necessary to keep the relay and consequently dryer operative. As the drying progresses, the relay ldtl will continue to receive successi ely less and weaker ground pulses until the laundry is quite Well dried. At that time, during eight consecutive revolutions and the random tumbling of the laundry during those revolutions, the resistance across the electrode multiples increases considerably and either Weak or no shorting pulses will reach the relay ltlll. Finally, the relay will release. Contacts 192, 1th; and 106 open. Contacts 164 on opening open the circuit to time delay relay llilil. Opening of contacts 164 also serves to open the circuit to heater 34- which is thereby deenergized.

Relay llltl remains operated for about two minutes after the opening of its energizing circuit. Thus, contact 132 remains closed for a period of about two minutes allowing continued operation of the rotor to provide a cool down tumble of the drum for the two-minute period. At the conclusion of the cool down period, relay ill) will restore opening contacts 112 and lid which opens the motor operating circuit and the dryer will come to a halt at the end of that period. Lamp 121 then fires over the previously described firing path and thereby signifies that the clothes are dry and the operative cycle has ended.

As mentioned previously, the ground path through neon lamp 120 and resistor 122 contains too much resistance to allow relay ltltl to become energized or to hold relay lilh operated. Thus, as a practical matter, relay tilt) is maintained operated by the combination of the low amount of current passed by resistor 122 and that of the other parallel branch circuit through the electrode multiple and the Wet clothes. Carrying this viewpoint further, it can be seen that by increasing the resistance of the branch parallel to that of the electrode multiple, the resistance of the clothes determines to a greater extent the drop-out time of relay Hill. This, in short, is the use accomplished by contact 129 of switch 124. When damp dry clothes are desired, rotation of dial 1? to damp dry operates switch 124 to engage contact 12%, placing resistor 126 in series with resistor 122. The added resistance requires a lower resistance and consequent higher current through the electrode multiple to maintain relay 1% operated. With this switch closed to its damp dry position, relay Hill will retsore at a time when the resistance of the clothes is greater than at the time when the switch is in its dry position.

A further advantage of the control circuit is apparent in the drying of materials such as heavy terry-cloth robes or shag rugs. These materials can exhibit a false appearance of dryness, in that the surface may be quite dry, while the heavy body will contain substantial moisture. If such articles were removed on the initial indication of dryness, migration of moisture through the loops of fabric by capillary attraction will again make the articles sensibly damp to the touch. In the present invention, however, the two-minute tumble following the restoration of relay 1% affords opportunity for such movement of moisture again to dampen the outermost fibers, whereupon the sensor electrodes will again have a low-resistance bridge. This restores proper circuit conditions for the reactivation of relay lltlil and resumption of dryer operation until the dryness of the terry cloth or like fabrics interrupts operation as previously described. It will be understood, of course, that the two-minute time delay of the relay 110 is by way of example only, and that longer time delay can be built into the relay if desirable.

Further utilizing the circuit of FIG. 5, it can be seen that if the machine has shut ofi indicating clothes dry to the sensed level, and the machine operator does not consider this condition dry enough, reset of the machine will initiate a further two-minute tumble in the machine. In this instance, the resistance of the clothes is not sufficient to keep relay 1% operated. The machine has restored. The dryness knob is still on automatic dry. The operator depresses start switch 95, reenergizing the motor, as previously described. A path is also closed from ground at lead N, through contacts 97, switch 124, relay ltlll, rectifier 116 and contacts 74 to the lead to L2. Relay 1% operates, closes its contacts 194, closes the circuit to relay llll. Meanwhile motor 42 and heater 34 are reenergized. Relay lllil then falls back opening the heater path. Motor 42 continues to rotate for a period governed by the relay 110. This relay remains operated for two minutes as will motor 42, following which both will again restore.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the scope of the invention.

What is claimed is:

1. In a laundry dryer including a drum mounted for rotation to tumble articles of clothing therein, an electric heater to facilitate evaporation of moisture from said clothes, and an electric motor operative to rotate said drum: the combination comprising a source of electric power, a first relay having a winding responsive to a predetermined value of electrical energy to operate said relay, electric circuit means for first temporarily energizing said relay to operate the same, switching means effective upon operation of said relay to energize said motor and said heater, a second relay having a winding, switching means effective upon operation of said first relay to energize the winding of said second relay to operate the same, switching means operated by said sec ond relay to provide a parallel energizing circuit for said electric motor, other switching means operated by said second relay to prepare a circuit for maintaining energization of said first relay, means in said last named circuit responsive to contact by damp clothes within said drum for completing said circuit at an energy level maintaining operation of said first relay and responsive to a less damp condition of said clothes to reduce said energy level below the operational threshold of said first relay to thereby effect the opening of the switching means associated therewith; each of said relays being of the slowto-release type, with the second relay delaying its release for a predetermined period after the release of the first, whereby to continue operation of said motor for said predetermined period.

2. The combination according to claim 1, further including timer means for terminating operation of said motor and said heater after a predetermined period of operation, and means whereby initiation of said timed operation will disable said first and second relays to prevent the same from interfering with said timed operation.

3. The combination according to claim 2, in which the circuit for temporarily energizing said first relay includes means for disabling said time-operation means and manually operable pushbutton switch means of the momentary contact type.

4. In a laundry dryer including a drum mounted for rotation to tumble articles of clothing therein, an electric heater to facilitate evaporation of moisture from said clothes, and an electric motor operative to rotate said drum: the combination comprising a source of electric power, a first electrically energized relay responsive to a predetermined value of electric energy to operate said relay, electric circuit means including a manually operable momentary contact switch for temporarily energizing said relay to operate the same, switching means elfective only upon operation of said relay to energize said motor 'and said heater, a second electrically energized relay, said first relay including switching means efiective upon initial operation thereof to energize said second relay to energize the same, said second relay including first switching means effective upon operation thereof to pro vide a parallel energizing circuit for said electric motor and second switching means to prepare a circuit for maintaining energization of said first relay, means responsive only to contact by articles having not less than a desired minimum electrical conductivity to complete said energizing circuit at an energy level maintaining operation of said first relay and responsive to a condition of less conductivity of said contacting articles to reduce the energy level of said circuit below the operational threshold of said first relay and thereby effect the opening of the switching means associated therewith; the second of said relays delaying its release for a predetermined period after the release of the first, whereby to continue operation of said motor for said predetermined period.

5. The combination according to claim 4, in which the circuit for maintaining energization of said first relay includes capacitance means arranged to discharge to ground through the winding of said relay.

1 6. The combination according to claim 4, in which the circuit for maintaining energization of said first relay includes means for optionally inserting additional resistance between the winding of said relay and ground.

7. The combination according to claim 4, including a manually operable master switch in the electrical circuit for energizing said first relay winding, a glow discharge lamp, an electric circuit connecting said lamp between said relay'winding and ground potential to energize said lamp upon closure of said master switch, a momentary contact pushbutton switch in series with said master switch and said relay winding, and electric circuit means for shunting out said discharge lamp upon closure of said pushbutton switch.

8. In a laundry dryer including a drum mounted for rotation to tumble articles of clothing therein, an electric heater to facilitate evaporation of moisture from said clothes, and an electric motor operative to rotate said drum: the combination comprising a source of electric power, a first relay having a winding responsive to a predetermined threshold value of electrical energy to operate said relay, means for temporarily energizing said relay to operate the same, switching means effective upon operation of said relay to energize said motor and said heater, a second relay having a winding, switching means effective upon operation of said first relay to energize the winding of said second relay to operate the same, switching means on said second relay to provide a parallel energizing circuit for said electric motor, other switching means on said second relay to prepare a circuit for maintaining energization of said first relay, said last-named circuit including spaced electrodes within said drum in the patch of articles of clothing being tumbled therein, said electrodes constituting a break in said circuit adapted to be bridged by said articles, wherein the electrical re sistance of said circuit is relatively low when the articles are damp and relatively high when the articles are dry, the winding of said first relay being in series with said energy maintaining circuit and being energized above its threshold level only while the resistance of said circuit is at the said relatively low level, said relay therefore restoring to effect the opening of its switching means as said articles attain dryness; said first relay having a delayed release time to maintain its switch means closed for the time necessary for articles of clothing in flight within said drum during the tumbling operation to contact with said electrodes.

9. The combination according to claim 8, in which said electrodes comprise conductors extendingcircumferentially about the interior of said drum and means for insulating said conductors from said drum while exposing the same to articles in the drum to be electrically bridged thereby.

10; The combiriation according to claim 8, in which said electrodes comprise aplurality of relatively closelyspaced pairs disposed at intervals along the axial length of said drum, the exposed surface of said drum between any two of said electrodes beingelectrically non-conductive.

l1. In a laundry dryer including a drum mounted for rotation to tumble anticles of clothing therein, an electric heater to facilitate evaporation of moisture from said clothes, and an electric motor for rotating said drum: the improvement in means for terminating the operation of said motor and said heater according to the dryness of the clothing, comprising: i

a source of electric energy,

a first relay having a winding responsive to a predeter mined threshold value of electri cal energy to activate the same,

a first electric circuit, including a first manually oper able switch, a discharge lamp, and a resistor in series with said relay across said energy source, the re sistance of said circuit being such as to preclude operation of said relay upon closing said switch,

a second electric circuit, including said switch, said lamp and said resistor to effect discharge of said lamp upon closure of said switch,

a third electric circuit including said relay and a second manually operable switch for shunting out said lamp while temporarily energizing said relay upon closure of said second switch,

an electric energy circuit including switch means actuated by said first relayto energize said motor and said heater upon activation of said relay,

a second relay,

an energy circuit including other switch means actuatcd' by said first relay to actuate said second relay,

an energy circuit including switch means actuated by said second relay to establish a parallel electric circuit for said motor, I

an energy circuit including further switch means actuated by said second relay to establish a second circuit for energizing said first relay, said second circuit including a plurality of normally open contacts adapted to be bridged by electrical conductance of the damp clothing thereacross during the tumbling thereof, whereby the maintenance of an energized condition of said first relay is dependent upon the conductance of the damp clothing bridge and the resistance of said first named electric circuit,

and means for adjusting the resistance of said first circuit to adjust the threshold operating level of said first relay, said second relay being arranged to delay opening its switch completing said second motor circuit to maintain operation of said motor for a predetermined period following deenergization of said'first relay and the opening of the motor circuit controlled thereby.

12. In a lanudry dryer including a drum mounted for rotation to tumble articles of clothing therein, an electric heater to facilitate evaporation of moisture from said clothes, and an electric motor for rotating said drum: the improvement in means for terminating the operation of said motor and said heater according to the dryness of the clothing, comprising:

a source of electric energy,

a firstrelay having a winding responsive to a predetermined threshold value of electrical energy to activate the same,

a first electric circuit, including a first switch manually operable to either of two operating positions, a discharge lamp, and a resistor in series with said relay across said energy source, the resistance of said circuit being such as to preclude operation of said relay upon closing said switch to either of its operating positions,

a third electric circuit including said relay and a manually operable momentary contactswitch for shunting out said lamp while temporarily energizing said relay upon closure or said second switch, said third circuit including means for maintaining activation of said relay for a predetermined period following the opening of said switch,

an electric energy circuit including first switch means actuated by said first relay to energize said motor and said heater upon activation of said relay,

a second relay,

an energy circuit including other switch means actuated by said first relay to actuate said second relay,

an energy circuit including switch means actuated by said second relay to establish a parallel electric circuit for said motor,

an energy circuit including switch means actuated by said second relay to establish a second circuit for energizing said first relay, said second circuit including a plurality of normally open contacts adapted to be bridged by the electrical conductance of the damp clothing thereacross during the tumbling thereof, whereby the maintenance of an energized condition of said first relay is dependent upon the resistance of the damp clothing bridge and the resistance of said first named electric circuit,

means for establishing first and second resistance values in the relay energizing circuit established by said second relay according to the operating position of said manually operable switch,

said second relay being arranged to delay opening its switch completing said second motor circuit to maintain operation of said motor for a predetermined period following deenergization of said first relay and the opening of the motor circuit controlled thereby.

13. In a laundry dryer including a drum mounted for rotation to tumble articles of clothing therein, an electric heater to facilitate evaporation of moisture from said clothes, and an electric motor for rotating said drum: the improvement in means for terminating the operation of said motor and said heater according to the dryness of the clothing, comprising:

a source of electric energy,

a first relay having a winding responsive to a predetermined threshold value of electrical energy to activate the same,

a first electric circuit, including a first manually oper- 12 able switch, a discharge lamp, and a resistor in series with said relay across said energy source, the resistance of said circuit being such as to preclude operation of said relay upon closing said switch,

a second electric circuit, including said switch, said switch, said lamp and said resistor to effect discharge of said lamp upon closure of said switch,

a third electric circuit including said relay and a momentary contact switch for shunting out said lamp while temporarily energizing said relay upon closure ofsaid switch, said third circuit including aresistorcapacitor combination for maintaining said first relay activated for an interval following the opening of said momentary contact switch,

a second relay,

anenergy circuit including other switch means actuated by said first relay to actuate said second relay,

an energy circuit including switch means actuated by said second relay to establish a second circuit for energizing said first relay, said second circuit including a plurality of normally open contacts adapted to be bridged by the electrical conductance of the damp clothing thereacross during the tumbling thereof, whereby the maintenance of an energized condition of said first relay is dependent upon the conductance of the damp clothing bridge,

means for introducing a fixed additional resistance into said second circuit to adjust the threshold operating level or said first rela said second relay being arranged to delay opening its switch completing said second motor circuit to maintain operation of said motor for a predetermined period following deenergization of said first relay and the opening of the motor circuit controlled thereby.

Retierencesv Cited in the file of this patent UNITED STATES PATENTS 2,045,381 Elberty June 23, 1936 2,736,970 Engel Mar. 6, 1956 2,743,532 Steward May 1, 1956 2,796,679 Dunkelman June 25, 1957 2,825,146 Kostelich Mar. 4, 1958 2,863,224 Zehrbach Dec. 9, 1958 2,878,579 Fuchs Mar. 24, 1959

Claims

1. IN A LAUNDRY DRYER INCLUDING A DRUM MOUNTED FOR ROTATION TO TUMBLE ARTICLES OF CLOTHING THEREIN, AN ELECTRIC HEATER TO FACILITATE EVAPORATION OF MOISTURE FROM SAID CLOTHES AND AN ELECTRIC MOTOR OPERATIVE TO ROTATE SAID DRUM; THE COMBINATION COMPRISING A SOURCE OF ELECTRIC POWER, A FIRST RELAY HAVING A WINDING RESPONSIVE TO A PREDETERMINED VALUE OF ELECTRICAL ENERGY TO OPERATE SAID RELAY, ELECTRIC CIRCUIT MEANS FOR FIRST TEMPORARILY ENEGIZING SAID RELAY TO OPERATE THE SAME, SWITCHING MEANS EFFECTIVE UPON OPERATION OF SAID RELAY TO ENERGIZE SAID MOTOR AND SAID HEATER, A SECOND RELAY HAVING A WINDING, SWITCHING MEANS EFFECTIVE UPON OPERATION OF SAID FIRST RELAY TO ENERGIZE THE WINDING OF SAID SECOND RELAY TO OPERATE THE SAME SWITCHING MEANS OPERATED BY SAID SECOND RELAY TO PROVIDE A PARALLEL ENERGIZING CIRCUIT FOR SAID ELECTRIC MOTOR, OTHER SWITCHING MEANS OPERATED BY SAID SECOND RELAY TO PREPARE A CIRCUIT FOR MAINTAINING ENERGIZATION OF SAID FIRST RELAY, MEANS IN SAID LAST NAMED CIRCUIT RESPONSIVE TO CONTACT BY DUMP CLOTHES WITHIN SAID DRUM FOR COMPLETING SAID CIRCUIT AT AN ENERGY LEVEL MAINTAINING OPERATION OF SAID FIRST RELAY AND RESPONSIVE TO A LESS DAMP CONDITION OF SAID CLOTHES TO REDUCE SAID ENERGY LEVEL BELOW THE OPERATIONAL THRESHOLD OF SAID FIRST RELAY TO THEREBY EFFECT THE OPENING OF THE SWITCHING MEANS ASSOCIATED THEREWITH; EACH OF SAID RELAYS BEING OF THE SLOWTO-RELEASE TYPE, WITH THE SECOND RELAY DELAYING ITS RELEASE FOR A PREDETERMINED PERIOD AFTER THE RELEASE OF THE FIRST, WHEREBY TO CONTINUE OPERATION OF SAID MOTOR FOR SAID PREDETERMINED PERIOD.