US3361941A - Switching circuit for an electrically heated blanket - Google Patents

Switching circuit for an electrically heated blanket Download PDF

Info

Publication number
US3361941A
US3361941A US449462A US44946265A US3361941A US 3361941 A US3361941 A US 3361941A US 449462 A US449462 A US 449462A US 44946265 A US44946265 A US 44946265A US 3361941 A US3361941 A US 3361941A
Authority
US
United States
Prior art keywords
resistors
control electrode
voltage
circuit
blanket
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US449462A
Inventor
August E F Fickweiler
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
INDOHEEM NV
Original Assignee
INDOHEEM NV
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by INDOHEEM NV filed Critical INDOHEEM NV
Application granted granted Critical
Publication of US3361941A publication Critical patent/US3361941A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
    • G05D23/00—Control of temperature
    • G05D23/19—Control of temperature characterised by the use of electric means
    • G05D23/20—Control of temperature characterised by the use of electric means with sensing elements having variation of electric or magnetic properties with change of temperature
    • G05D23/24—Control of temperature characterised by the use of electric means with sensing elements having variation of electric or magnetic properties with change of temperature the sensing element having a resistance varying with temperature, e.g. a thermistor
    • G05D23/2451—Details of the regulator
    • G05D23/2453—Details of the regulator using discharge tubes
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B5/00—Anti-hunting arrangements
    • G05B5/01—Anti-hunting arrangements electric
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
    • G05D23/00—Control of temperature
    • G05D23/19—Control of temperature characterised by the use of electric means
    • G05D23/20—Control of temperature characterised by the use of electric means with sensing elements having variation of electric or magnetic properties with change of temperature
    • G05D23/24—Control of temperature characterised by the use of electric means with sensing elements having variation of electric or magnetic properties with change of temperature the sensing element having a resistance varying with temperature, e.g. a thermistor

Definitions

  • the heating circuit is switched on through a relay as soon as the resistance of the negative temperature coefiicient resistors, which serve as temperature sensors, rises above a predetermined value, whereas the heating circuit is disconnected as soon as this resistance falls below a predetermined value, whereby the blanket temperature is automatically stabilized between two adjustable values in close proximity to each other.
  • the switching circuit Since the switching circuit is connected to the blanket through a flexible cord, it is not an imaginary hazard that a short-circuit or an interruption occurs in that cord or in the blanket itself.
  • the resistance thereof falls below the predetermined value, in which case the heating circuit is disconnected, so that this cannot give rise to hazards.
  • the resistance thereof rises above the predetermined value, in which case the heating circuit is switched on, regardless of the blanket temperature, which can lead to scorching of the blanket or even to injury of the user.
  • the heating circuit is connected to the supply voltage through a normally open contact of a relay, the coil of which, which is bridged by a capacitor, is connected in the main discharge circuit of a gas discharge valve with two control electrodes, which is supplied with an AC. voltage, the first control electrode being connected through the negative temperature coefficient resistor(s) to the positive terminal of a DC. voltage source and being connected through a conventional resistor to the negative terminal thereof, whilst the second control electrode is through conventional resistors connected to the positive and negative terminals respectively of that DC. voltage source, Whilst the first control electrode is also connected to the cathode of the gas discharge valve through a conventional grid leak with a resistance which is large as compared with the remaining resistors.
  • the resistance of the negative temperature coeificient resistors rises to such extent that a positive voltage with respect to the first control electrode and the cathode, which is connected to the first control electrode through a resistor, is applied to the second control electrode of the gas discharge valve, so that the valve ignited, the relay is energized and the heating circuit is closed.
  • the capacitor across the relay coil serves for smoothing the energizing current of the relay notwithstanding the AC. voltage supply.
  • the resistance of the negative temperature coeflicient resistors rises to such an extent, that the voltage at the second control electrode of the gas discharge valve is insuflicient for igniting the valve anew after the next passage through zero of the supply voltage, so that the relay is de-energized and the heating circuit is disconnected.
  • the first control electrode is rendered negative to such an extent by the current flowing through the grid leak, that notwithstanding the positive voltage which is applied to the second control electrode, the gas discharge valve cannot ignite anew after the next passage through zero of the supply voltage, so that the relay is de-energized and the heating circuit is switched off.
  • the invention is further elucidated below with reference to the drawing, which shows a circuit diagram of an embodiment of a switching circuit according to the invention.
  • the heating element 1 is through the normally open contact of a relay 2 connected to the supply terminals 3, to which an AC. voltage is applied.
  • a transformer 4 By means of a transformer 4, a rectifier 5 and a capacitor 6 a DC. voltage of e.g. 30 v. is derived from the AC. supply voltage.
  • the relay 2 the coil of which is bridged by a capacitor 7, is connected in the anode circuit of a gas discharge valve 8 (e.g. of the PL 21 type), the first control electrode of which is through a grid leak 9 (of e.g. kilohms) connected to the cathode.
  • the heater circuit has not been shown, since this is not essential to the invention.
  • the first control electrode is also connected through a conventional resistor 10 of e.g. 10 kilohms to the negative terminal of the DC. voltage across the capacitor 6 and is through one or more negative temperature coefi'icient resistors 11 (with an overall resistance at 25 degrees centigrade of e.g. 6 kilohms) connected to the positive terminal of the DC. voltage across the capacitor 6.
  • a conventional resistor 10 e.g. 10 kilohms
  • the first control electrode is also connected through a conventional resistor 10 of e.g. 10 kilohms to the negative terminal of the DC. voltage across the capacitor 6 and is through one or more negative temperature coefi'icient resistors 11 (with an overall resistance at 25 degrees centigrade of e.g. 6 kilohms) connected to the positive terminal of the DC. voltage across the capacitor 6.
  • the second control electrode is connected to the movable tap of an adjustable potentiometer 12 with a resistance of e.g. 5 kilohms, the ends of which are through conventional resistors 13 and 14 respectively of e.g. 6 kilohms connected to the positive and negative terminals respectively of the DC. voltage across the capacitor 6.
  • the temperature at which the heating element 1 is switched on and switched off is dependent upon the adjustment of the potentiometer 12. However, it is also possible to dispense with this potentiometer and to make one of the resistors 10, 13 or 14 adjustable.
  • Switching circuit for an electrically heated blanket which is controlled by one or more negative temperature coefiicient resistors which are arranged in the blanket, wherein the heating circuit is connected to the supply voltage through the normally open contact of a relay, the coil of which, which is bridged with a capacitor, is connected in the main discharge circuit of a gas discharge valve with two control electrodes, which is supplied with an A.C. voltage, the first control electrode being connected through the negative temperature coeificient resistor(s) to the positive terminal of a D.C. voltage source and being connected through a conventional resistor to the negative terminal thereof, whilst the second control electrode is through conventional resistors connected to the positive and negative terminals respectively of that D.C. voltage source, whilst the first control electrode is also connected to the cathode of the gas discharge valve through a conventional grid leak, the resistance of which is large as compared with the remaining resistors.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Automation & Control Theory (AREA)
  • Control Of Resistance Heating (AREA)
  • Control Of Temperature (AREA)

Description

Jam 1963 A. E. F. FICKWEILER 3,361,
SWITCHING CIRCUIT FOR AN ELBCTRICALLY HEATED BLANKET Filed April 20, 1965 IN VEN TOR.
AUGUST E. F. FICKWEILER BY 02% ATTORNEYS United States Patent 3,361,941 SWITCHING CIRCUIT FOR AN ELECTRICALLY HEATED BLANKET August E. F. Fickweiler, Waddinxveen, Netherlands, assignor to Indoheem, N.V., a corporation of Netherlands Filed Apr. 20, 1965, Ser. No. 449,462 Claims priority, applicationslzesglerlands, May 6, 1964, 2 Claims. (Cl. 317-132) The invention relates to a switching circuit for an electrically heated blanket, which is controlled by one or more negative temperature coeflicient resistors which are arranged in the blanket.
In such a switching circuit, the heating circuit is switched on through a relay as soon as the resistance of the negative temperature coefiicient resistors, which serve as temperature sensors, rises above a predetermined value, whereas the heating circuit is disconnected as soon as this resistance falls below a predetermined value, whereby the blanket temperature is automatically stabilized between two adjustable values in close proximity to each other.
Since the switching circuit is connected to the blanket through a flexible cord, it is not an imaginary hazard that a short-circuit or an interruption occurs in that cord or in the blanket itself. On the occurrence of a short-circult of the negative temperature coefiicient resistors, the resistance thereof falls below the predetermined value, in which case the heating circuit is disconnected, so that this cannot give rise to hazards. On the occurrence of an interruption of the negative temperature coeflicient resistors, however, the resistance thereof rises above the predetermined value, in which case the heating circuit is switched on, regardless of the blanket temperature, which can lead to scorching of the blanket or even to injury of the user.
It is an object of the invention to provide a control circuit of the type set forth above, in which the heating circuit is disconnected as soon as an interruption of the negative temperature coefficient resistors occurs.
For that purpose, it is a feature of a device according to the invention, that the heating circuit is connected to the supply voltage through a normally open contact of a relay, the coil of which, which is bridged by a capacitor, is connected in the main discharge circuit of a gas discharge valve with two control electrodes, which is supplied with an AC. voltage, the first control electrode being connected through the negative temperature coefficient resistor(s) to the positive terminal of a DC. voltage source and being connected through a conventional resistor to the negative terminal thereof, whilst the second control electrode is through conventional resistors connected to the positive and negative terminals respectively of that DC. voltage source, Whilst the first control electrode is also connected to the cathode of the gas discharge valve through a conventional grid leak with a resistance which is large as compared with the remaining resistors.
It the blanket temperature falls below the desired value, the resistance of the negative temperature coeificient resistors rises to such extent that a positive voltage with respect to the first control electrode and the cathode, which is connected to the first control electrode through a resistor, is applied to the second control electrode of the gas discharge valve, so that the valve ignited, the relay is energized and the heating circuit is closed.
The capacitor across the relay coil serves for smoothing the energizing current of the relay notwithstanding the AC. voltage supply.
If the blanket temperature rises above the desired value, the resistance of the negative temperature coeflicient resistors rises to such an extent, that the voltage at the second control electrode of the gas discharge valve is insuflicient for igniting the valve anew after the next passage through zero of the supply voltage, so that the relay is de-energized and the heating circuit is disconnected.
If an interruption of the negative temperature coeificient resistors occurs, the first control electrode is rendered negative to such an extent by the current flowing through the grid leak, that notwithstanding the positive voltage which is applied to the second control electrode, the gas discharge valve cannot ignite anew after the next passage through zero of the supply voltage, so that the relay is de-energized and the heating circuit is switched off.
The invention is further elucidated below with reference to the drawing, which shows a circuit diagram of an embodiment of a switching circuit according to the invention.
The heating element 1 is through the normally open contact of a relay 2 connected to the supply terminals 3, to which an AC. voltage is applied. By means of a transformer 4, a rectifier 5 and a capacitor 6 a DC. voltage of e.g. 30 v. is derived from the AC. supply voltage. The relay 2, the coil of which is bridged by a capacitor 7, is connected in the anode circuit of a gas discharge valve 8 (e.g. of the PL 21 type), the first control electrode of which is through a grid leak 9 (of e.g. kilohms) connected to the cathode. The heater circuit has not been shown, since this is not essential to the invention.
The first control electrode is also connected through a conventional resistor 10 of e.g. 10 kilohms to the negative terminal of the DC. voltage across the capacitor 6 and is through one or more negative temperature coefi'icient resistors 11 (with an overall resistance at 25 degrees centigrade of e.g. 6 kilohms) connected to the positive terminal of the DC. voltage across the capacitor 6.
The second control electrode is connected to the movable tap of an adjustable potentiometer 12 with a resistance of e.g. 5 kilohms, the ends of which are through conventional resistors 13 and 14 respectively of e.g. 6 kilohms connected to the positive and negative terminals respectively of the DC. voltage across the capacitor 6.
The operation of the circuit has already been described hereinabove.
Instead of a gas discharge valve with heated cathode, as the PL 2.1 type mentioned above, it is also possible to employ a cold cathode gas discharge valve, in which case the heater supply circuit can be dispensed with. The abovementioned resistances and voltage values too have been given by way of example only.
The temperature at which the heating element 1 is switched on and switched off is dependent upon the adjustment of the potentiometer 12. However, it is also possible to dispense with this potentiometer and to make one of the resistors 10, 13 or 14 adjustable.
Whilst a preferred embodiment of the invention has been shown and described above, it will of course, be understood that various other modifications may be made. The appended claims are, therefore, intended to cover any such modification within the true spirit and scope of the invention.
I claim:
1. Switching circuit for an electrically heated blanket, which is controlled by one or more negative temperature coefiicient resistors which are arranged in the blanket, wherein the heating circuit is connected to the supply voltage through the normally open contact of a relay, the coil of which, which is bridged with a capacitor, is connected in the main discharge circuit of a gas discharge valve with two control electrodes, which is supplied with an A.C. voltage, the first control electrode being connected through the negative temperature coeificient resistor(s) to the positive terminal of a D.C. voltage source and being connected through a conventional resistor to the negative terminal thereof, whilst the second control electrode is through conventional resistors connected to the positive and negative terminals respectively of that D.C. voltage source, whilst the first control electrode is also connected to the cathode of the gas discharge valve through a conventional grid leak, the resistance of which is large as compared with the remaining resistors.
2. Switching circuit according to claim 1, wherein one or more of the conventional resistors which are connected to the D.C. voltage source are made adjustable.
References Cited UNITED STATES PATENTS 2,429,453 10/1947 Crowley 219212 2,831,130 4/1958 Obloy 317 132 2,892,917 6/1959 Staats 317-131 X 2,958,008 10/1960 Bray et a1. 2l9501 X LEE T. HIX, Primary Examiner.

Claims (1)

1. SWITCHING CIRCUIT FOR AN ELECTRICALLY HEATED BLANKET, WHICH IS CONTROLLED BY ONE OR MORE NEGATIVE TEMPERATURE COEFFICIENT RESISTORS WHICH ARE ARRANGED IN THE BLANKET, WHEREIN THE HEATING CIRCUIT IS CONNECTED TO THE SUPPLY VOLTAGE THROUGH THE NORMALLY OPEN CONTACT OF A RELAY, THE COIL OF WHICH, WHICH IS BRIDGED WITH A CAPCITOR, IS CONNECTED IN THE MAIN DISCHARGE CIRCUIT OF A GAS DISCHARGE VALVE WITH TWO CONTROL ELECTRODES, WHICH IS SUPPLIED WITH AN A.C. VOLTAGE, THE FIRST CONTROL ELECTRODE BEING CONNECTED THROUGH THE NEGATIVE TEMPERATURE COEFFICIENT RESISTOR(S) TO THE POSITIVE TERMINAL OF A D.C. VOLTAGE SOURCE AND BEING CONNECTED THROUGH A CONVENTIOANL RESISTOR TO THE NEGATIVE TERMINAL THEREOF, WHILST THE SECOND CONTROL ELECTRODE IS THROUGH CONVENTIONAL RESISTORS CONNECTED TO THE POSITIVE AND NEGATIVE TERMINALS RESPECTIVELY OF THAT D.C. VOLTAGE SOURCE, WHILST THE FIRST CONTROL ELECTRODE IS ALSO CONNECTED TO THE CATHODE OF THE GAS DISCHARGE VALVE THROUGH A CONVENTIONAL GRID LEAK, THE RESISTANCE OF WHICHH IS LARGE AS COMPARED WITH THE REMAINING RESISTORS.
US449462A 1964-05-06 1965-04-20 Switching circuit for an electrically heated blanket Expired - Lifetime US3361941A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL6405084A NL121571C (en) 1964-05-06 1964-05-06 DEVICE FOR ELECTRICAL HEATING OF AN OBJECT

Publications (1)

Publication Number Publication Date
US3361941A true US3361941A (en) 1968-01-02

Family

ID=62044203

Family Applications (1)

Application Number Title Priority Date Filing Date
US449462A Expired - Lifetime US3361941A (en) 1964-05-06 1965-04-20 Switching circuit for an electrically heated blanket

Country Status (4)

Country Link
US (1) US3361941A (en)
FR (1) FR1436258A (en)
GB (1) GB1030583A (en)
NL (1) NL121571C (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3673380A (en) * 1971-10-26 1972-06-27 Northern Electric Co Glow switch relay for blanket overheat control switch
US3673381A (en) * 1971-10-26 1972-06-27 Northern Electric Co Thermostatless blanket control circuit
USRE28656E (en) * 1971-10-26 1975-12-16 Thermostatless blanket control circuit

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3445631A (en) * 1966-03-14 1969-05-20 Indoheem Nv Safety system for an electrically heated blanket

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2429453A (en) * 1946-03-21 1947-10-21 Gen Electric Bridge control for electric blankets
US2831130A (en) * 1956-03-16 1958-04-15 Bill Jack Scient Instr Co Electronic pulsing device
US2892917A (en) * 1958-09-29 1959-06-30 Gen Electric Automatic temperature control system
US2958008A (en) * 1959-08-14 1960-10-25 Chemstrand Corp Control circuit

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2429453A (en) * 1946-03-21 1947-10-21 Gen Electric Bridge control for electric blankets
US2831130A (en) * 1956-03-16 1958-04-15 Bill Jack Scient Instr Co Electronic pulsing device
US2892917A (en) * 1958-09-29 1959-06-30 Gen Electric Automatic temperature control system
US2958008A (en) * 1959-08-14 1960-10-25 Chemstrand Corp Control circuit

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3673380A (en) * 1971-10-26 1972-06-27 Northern Electric Co Glow switch relay for blanket overheat control switch
US3673381A (en) * 1971-10-26 1972-06-27 Northern Electric Co Thermostatless blanket control circuit
USRE28656E (en) * 1971-10-26 1975-12-16 Thermostatless blanket control circuit

Also Published As

Publication number Publication date
FR1436258A (en) 1966-04-22
GB1030583A (en) 1966-05-25
NL121571C (en) 1966-07-15
NL6405084A (en) 1965-11-08

Similar Documents

Publication Publication Date Title
US3161759A (en) Electric range heater control
US3364338A (en) Oven temperature control
US3114819A (en) Electrical heating devices
US3462585A (en) Electrically heated bedcover control
US3385957A (en) Electronically controlled heater
US2501499A (en) Electric heating device and control therefor
US3896289A (en) Aquarium water heater
US3361941A (en) Switching circuit for an electrically heated blanket
US3351739A (en) Control system for electrically heated boiler
US2429453A (en) Bridge control for electric blankets
US2795697A (en) Temperature control
US3564206A (en) Fail-safe sensor/override for circuit
GB1206638A (en) Apparatus for controlling the energization of an electrical load
US3360693A (en) Switching circuit for an electrically heated blanket
US3543005A (en) Temperature control system for an electrically heated blanket
US3732394A (en) Iron
US2764663A (en) Electric heating apparatus
US3524968A (en) Thermal control for electrical heating device
GB1112522A (en) Ambient integral pulse switching system
US2543620A (en) Electric blanket control
US2680215A (en) Window temperature control
US2510039A (en) Electric blanket control
US2823290A (en) Electric heating apparatus
US3544767A (en) Heating control circuit with scr-unijunction transistor combination
US3040156A (en) Control circuit