US 3806308 A
An automatic clothes drying machine timer control circuit having the timer operation controlled by the operation of a normally closed switch in the automatic ignition system of a gas valve assembly. The timer is connected to the voltage source through the switch and is operative when the switch is closed.
Description (OCR text may contain errors)
United States Patent 11 1 1111 3,806,308 Cahoe et al. 1 Apr. 23, 1974 [5411 GAS DRYER TIMER CONTROL CIRCUIT 3,527,446 9/1968 White 432/43 1 3,558,110 l/l97l K hn 34/45 [751 Inventors: James Cab, Fem i 3,589,846 6/1971 PIZSCC 431/66 Edward G. Sommer, Jr., Loulsville, both of Ky. 1  Assignee: General Electric Company Primary Examiner-Carroll B. Dority, Jr.
1 Louisville Asslstant Exammer-Paul Devmsky Attorney, Agent, or Firm-Francis H. Boos, Jr.  Filed: Oct. 20, 1972 ] Appl. N0.: 299,227
 ABSTRACT  US, Cl 432/44, 431/66, 34/45, 1 1
1 34/55 An automatic clothes drying machine timer control  Int. Cl. F23n 5/24, F26b 19/00 circuit having the timer operation controlled by the Field 0f Search 4/ 5 operation of a normally closed switch in the automatic 431/ 36; 432/43, 44 ignition system of a gas valve assembly. The timer is 1 3 1 connected to the voltage source throughthe switch  I 1 References ted and is operative when the switch is closed.
1 UNITED STATES PATENTS 1 1 3,238,636 3/1966 Chafee, Jr. et al. 34/45 5 Claims, 2 Drawing Figures ti 1 .\3 1 11) 1 I 36" I l 50b "'fi- ,1z 1 so Soq 51 5E h 1 .1i1 b l 4-0 I 33 S2.
4" i1 1 k) A f 1 l 7 i \J L/ I I I I I I 1 1 46 I I F 1 1% I I 1 1 l 1 1 44 BACKGROUND OF THE INVENTION DESCRIPTION OF THE PREFERRED I EMBODIMENT Referring now to FIG. 1, the. machine illustrated is a e The present invention utilizes an automatic gas clothes dryer provided in the usual manner withacabiburner ignition system of the type using a radiant energy heat sensor switch to control timer run time independentlyofthe thermostat means when the machine is in an automatic mode wherein the drying cycle oper- 1 ation is controlled by a combination of. gas burner cycles initiated bythe thermostat means sensing temperature condition in the machine and timer running time controlled by the sensor switch incorporated in the ignition system of the gas burner.
In present machines automatic cycles are generally effected by use of a thermostatic control sensitive to the temperature of.clothes in themachine. This is done on the basis thata predetermined rise in clothes temperature indicates that the heat energy applied to the clothes is no longer: beingused to vaporize moisture from the clothes, but instead is free to raise the temperature, In otherwords, such control systems utilize a predetermined temperature as a trip point for shutting off the means provided for heating the clothes. Depending upon the type of fabric being dried and the size of the load, either a single such Occurrence may be sufficientor several such heating cycles may be required in a single drying operation. The number. of heating cycles is usually determined by having a timer run each time the heater shuts off, with the total length of timer operation being predetermined.
In prior art clothes dryers the thermostatically controlled switching means have been employed to open the circuit to the heating means, and simultaneously energize the timer motor when the thermally operated switch means reached a predetermined temperature. This arrangement has had undesirable effects when due to malfunction the thermally operated switches remain open and in effect prevent the machine from terminating a cycle by keeping the timer motor circuit open.
SUMMARY OF THE INVENTION In accordance with this invention, there is provided a timer control for an automatic gas dryer which includes utilizing an ignition system for a gas burner to control timer run time to terminate a drying cycle. The thermostats are wired in serieswith the ignition system BRIEFDESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic side elevational view of a clothes dryer suitable .for incorporation of the invention, the view being partly broken away and partly in section to illustrate details;
FIG. 2 is a schematic illustration of my improved control circuit.
net 1 having a front door 2 to provide access to the cab I inet for loading and unloading clothes. Provided on the top wall of the cabinet is a control panel which may include a suitable manual control 3 connected to a con- 0 trol assembly 4. By manually pro-setting the control as- 'sembly 4, the machine may be caused to start and automatically proceed through a cycle of operation.
Within cabinet 1, thereis provided a clothes tumbling drum 6 mounted for rotation on a substantially horizontal axis. In Order to provide for a flow of drying air through the clothes drum, there is provided an opening 7 through which the clothes are placed in the drum 6 and a pluralityof perforations 8 in the rear wall. The air provided to the drum is heated by a gas flame which issues from an outlet 9 of a. conventional burner 10 located in a channel 11. Burner 10 receives a regulated supply of gas from a solenoid-operated controlling valve assembly 12, the gas being supplied to the assembly 12 through a pipe 13. In the conventional way, primary air is drawn into the burner, the combustion occurs as a result of the mixture of this primary air with al. on Feb. 24, 1970, and will hereafter be described in conjunction with the improved control circuit in enough detail for a complete understanding of the present invention.
The outlet end of chamber 11 communicates with an upwardly extending duct 14 which communicates with the openings 8 in the rear wall of drum 6. The air outlet from the drum is provided through opening 7, duct 16,
blower 17, driven by motor 18 through duct 19 and is I discharged through an appropriate outlet (not shown) in the rear of the cabinet 1. i I I -In addition to driving blower 17, motor 18 rotates the drum 6. To this end themotor 18 is provided with pul ley 20 which has an endless belt 21 extending over it, e
and completely around thecylindrical wall of the drum 6. Thus, the air ispulled through the drum at the same time the fabrics in the drum are tumbled. The air is heated by the flame emitted from the burner 9, the
heated air passing through the drum causes vaporization of the moisture from the clothes. Thevapor is car ried off with the air as it passes outof the machine.
Referring now to the circuit diagram of FIG. 2, there is shown a timer control circuit for an automatic clothes drying machine having a gas valve assembly 12 in which an embodimentof this invention isincorporated. An AC voltage source (not shown) typically volts AC is connected to the terminals 30 and 31 to energize the entire control system of the dryer including the-dryer drive motor 18, the gas valve assembly in cluded within the dotted lines 12,a timer motor 32 which controls a plurality of cam operated switches, and a control thermostat 33. In order to initiate operation of the dryer drive motor 18, it is necessary to close the contacts of a switch 34 which are operated by a cam 36 driven by timer motor 32. While the switch contacts 34 are operable by cam 36 driven by timer motor 32, the timer cam may also be driven by the manually operated control knob 3, which may be rotated to close the contacts of switch 34. With the contacts 34b of switch 34 closed, drive motor 18 is energized by the conductors 30 and 31 by closing the contacts of a door switch 38. Energization of the drive motor 18 is terminated when either the timer motor 32 has driven the cam operating switch 34 to a position wherein it opens, or the dryer door is open thereby opening the contacts of switch 38. The gas valve assembly 12 is connected from conductor 31 to conductor 30 through contact 34a and the control thermostat 33. The thermostat 33 may include a thermally operated switch 40 which is responsive to the dryer drum inlet temperature and a thermally operated switch 41 which is responsive to the drum outlet temperature connected in parallel. When the drum outlet temperature rises to a predetermined temperature, switch 41 opens. The drum inlet thermally operated switch 40 is closed at lower temperatures and when the drum inlet temperature rises to a predetermined temperature opens.
Located in series between the thermostat 33 and the gas valve assembly 12 is a safety or high limit switch 52 which will open the circuit to the gas valve assembly in the event of thermostat malfunction such as being welded shut and unable to break the circuit to the gas valve assembly.
Thus, when operation of the dryer is initiated the contacts of thermally operated switches 40 and 41 will normally be closed such that the AC supply voltage supplied to terminals 30 and 31 will be supplied to the gas valve assembly 12. The gas valve assembly 12 comprises igniter 42'which in the illustrated embodiment is a resistance heating element of recrystallized silicon carbide.
lgniter 42 is an electrical resistance type heating element which when supplied with the required voltage will reach a temperature above the minimum temperature necessary for ignition of the gaseous fuel. While the specific type of igniter used does not form part of the invention, reference is made to US. Pat. No. 3,372,305 issued to A. R. Mikulec on Mar. 5, 1968, which discloses in detail a silicon carbide igniter suitable for use in the illustrated gas valve assembly. Connected in series with the igniter 42 is a radiant energy heat sensor switch 43. The radiant energy heat sensor 43 is positioned to receive radiant energy emanating from the igniter 42 when energized, and from the gas flame when the burner is operating. While the specific type of radiant energy heat sensor used does not form part of this invention, the prior mentioned patent of Donald E. Place et al. discloses in detail the structural characteristics of a radiant energy heat sensor and circuitry including the sensor suitable for use in connection with the timer control means of the present invention. The sensor switch 43 is normally closed, and is opened when the igniter 42 reaches a predetermined temperature above ignition temperature of the gas, wherein it emits sufficient radiant heat energy to cause the switch 43 to open. The gas valve assembly includes, for purposes of controlling the gas flow, two solenoid actuated gas valves 44 and 47 connected in series. A first one of these valves 44 is responsive to energization ofa holding coil 45 and a booster coil 46. Gas valve 44 will be actuated to the open position only when both holding coil 45 and booster coil 46 are energized by the full supply voltage. However, once the valve is actuated to the open position, it will remain open as long as holding coil 45 is energized by the voltage, irrespective of a decrease in the voltage supplied to booster coil 46. The second or main gas valve 47 is operated by coil 48.
In the non-automatic cycle wherein the timer is set to run for a pre-selected amount of time the circuit to timer motor 32 is from line 30 through contact 34b of switch 34 contact 5012 of a switch 50 to line 31. In this mode a cool-down period is provided in the cycle of operation of the dryer by completing a circuit from line 30 through the motor 18 to maintain the flow of air through the dryer drum while keeping contact 34a of switch 34 open to prevent a circuit through the thermostats and gas valve assembly.
In accordance with an embodiment of the present invention the timer 32 is connected to the junction point of the igniter 42, radiant sensor switch 43, booster coil 46 of solenoid 44 and coil 48 of the main valve 47 through a contact 50a of switch 50 and through a conductor 51. At the start of a normalcycle of gas valve and ignition operation, with the switch 34, thermally actuated switches 40 and 41 closed, and the door switch 38 also closed, the line voltage will be applied to the gas valve assembly. Since the radiant sensor switch 43 is closed, full line voltage will be applied to the timer 32, the igniter 42, the booster coil 46, and the holding coil 45. However, gas will not flow since the main gas valve coil 48 is shunted by the closed sensor switch 43. When the igniter 42 reaches a predetermined temperature above the gas ignition temperature the sensor switch 43 will open. This will result in igniter 42 being connected in parallel with the booster coil 46 both being in series with the main valve coil 48 across the power supply. Since the igniter 42 has a very low resistance as compared to that of the coil 48, the coil 48 will be energized near line voltage to cause valve 47 to open. The holding coil 45 of the valve 44 remains energized at line voltage, and gas will be supplied to the burner 9 to be ignited by the energized igniter 42. Because of the relatively low resistance of the igniter 42 relative to the timer 32, and due to the parallel relationship with the timer 32, the timer in effect is shunted out by the closed contacts of thermostat 33 and igniter 42 and the timer will not run.
In a normal cycle of operation, the control thermostats 40 and 41 open when they sense a build up in temperature beyond the effective range of drying clothes through evaporation. The opening of a path through the normally closed thermostats 40 and 41 de-energizes the main valve voil 47 and the holding coil 45 to effectively shut down gas flow and the flame from burner 9. The timer circuit from line 30 through timer 32, timer switch 50, conductor 51 and the main coil 47 to line 31 is effective to run the timer motor 32. In this mode with the radiant switch 43 open the timer 32 is in series with the main valve 47 and is designed to operate at the voltage imposed thereon while the current is insufficient to keep the coil 47 energized. However, when the switch 43 cools and resets in a relatively short time, for example, between 10 and 30 seconds, the coil 48 will be completely shunted, and full voltage is again applied to the timer motor 32 through the switch 43. From the above description of the embodiment of the present invention it can readily be understood that an automatic drying cycle is provided the length of which is in part radiant sensor 43 or the main solenoid coil 48 in the event thermostat 33 or safety switch 52 fail in the open position. In the event the igniter 42 fails in the open position the coils 46and 47 are in series and will not be energized because of the voltage drop across each is less than the voltage required to energize them, there being no gas flow ignition will not occur but the timer will be energized through the switch 43.,The above will be true if ignition does not occur due to failure of the coils 44, 46 or 48 in the open position.
It will thus be seen that by the present embodiment of the invention the timer will advance to terminate machine operation in the event ignition does not occur.
While there has been shown and described a specific embodiment of the present invention, the invention is not limited thereto and it is intended by the appended claims to cover all modifications falling within the true spirit and scope of this invention.
What is claimed as new and desired to be secured by letters patent of the United States is: l
1. An automatic clothes dryer timer control'circuit comprising:
a voltage source;
i a gas valve assembly coupled to the voltage source through a thermostat means for providing drying heat and having a normally closed switch adapted to be opened when the gas valve assembly is rendered operative by said thermostat means in response to the application of voltage thereto; and
a timerconnected to said voltage source through said normally closed switch to be operative when the switch is closed for positive operation of said timer means, independent of the operation of said thermostat means when said thermostat means renders said gas valve assembly inoperative.
t 2. An automatic clothes dryer timer control circuit comprising:
timer means arranged to discontinue operation of said dryer after a predetermined period of timer operation; 3 i t gas valve assembly including solenoid valve means operable to supply gas to a burner means;
thermostat means in said control circuit connected in series with said gas valve assembly, said thermostat means movable to de-energize said solenoid valve means when the air temperature is above a predetermiried level;
switch means in said gas valve assembly operable to energize said solenoid valve means each time ignition is required; and
circuit means connecting said timer means through said switch means for positive operation of said timer means independent of the operation of said thermostat means when said thermostat means move to de-energize said solenoid valve means.
3. An automatic clothes dryer timer control circuit comprising: i
gas valve assembly including solenoid valve means operable to supply gas to a burner means;
thermostat meansin said control circuit connected in series with said gas valve assembly, said thermostat means movable to de-energize said solenoid valve means when the air temperature is above a predetermined level;
switch means in said gas valve assembly operable to energize said solenoid valve means each time ignition is required;
igniter means in said gas valve assembly operable to open said switch means and to initiate combustion when said valve means are energized; and timer means for discontinuing operation of said dryer after a predetermined period of timer operation, said timer means being connected through said switch means to operational voltage for positive operation of said timer means independent of the operation of said thermostat means when said thermostat means moves to de-energize said solenoid valve means. 4. The control circuit of claim 3 wherein said switch means and solenoid valvemeans are connected in parallel and the timer means is energized through said solenoid valve means when said thermostat means and said switch means are open.
5. An automatic clothes dryer comprising:
a rotatably mounted drum for receiving clothes to be dried;
air moving means for passing air into and out of said drum;
an electric motor for operating said air moving means and for rotating said drum;
an electrically operable gas valve assembly including a burner for heating the air passing into said drum;
timer means arranged to discontinue operation of said dryer after a predetermined period of timer operation;
thermostat means in said circuit connected in series with said gas valve assembly, said thermostat means movable between an open position, to deenergize said gas valve assembly when the air temperature is above a predetermined level, and a closed position to energize said gas valve assembly when the air temperature is below said predetermined level;
said gas valve assembly including a first valve means having a solenoid and a second valve means having a solenoid having a booster coil and a holding coil, said first and second solenoids being operable to supply fuel to said burner only when both valves are open, igniter means, and switch means;
said igniter means operable to open said switch means and initiate combustion;
said switch means operable to energize said first valve means each time ignition is required;
said timer means being connected through said switch means to operational voltage for positive operation of said timer independent of the operation of said thermostat means when said thermostat means moves to de-energize said solenoid valve means; and t t a said switch means and said first valve means are in parallel and the timer means is energized through said first valve means when said thermostat and said switch means areopen.