Electric blanket

• US 4,031,352 A
• Filed: 10/16/1975
• Issued: 06/21/1977
• Est. Priority Date: 10/18/1974
• Status: Expired due to Term

• Current Assignee: C S Oosterberg Limited
• Original Assignee: C S Oosterberg Limited
• Inventors: Oosterberg, Cedric Siegfried
• Primary Examiner(s): Albritton, C. L.
• Application Number:
  US05/623,105
• Time in Patent Office: 614 Days
• Field of Search: 219/212, 219/529, 219/549, 219/545, 219/505, 219/504, 219/501, 307/310
• US Class Current: 219/212
• CPC Class Codes: G05D 23/1909 whose output amplitude can only take two discrete values
• CPC Class Codes: G05D 23/24 the sensing element having a resistance varying with temperature, e.g. a thermistor
• CPC Class Codes: H05B 1/0227 Applications
• CPC Class Codes: H05B 2203/035 Electrical circuits used in resistive heating apparatus
• CPC Class Codes: H05B 3/342 heaters used in textiles

Abstract

An electric blanket assembly having a blanket whose heating elements are supplied from a low voltage supply source and a control circuit assembly adapted both to regulate the heating of the blanket and to disconnect the supply source from the heating elements under conditions of malfunction of the assembly. The control circuit includes temperature sensitive elements suitably located in the blanket and associated circuitry arranged to generate a control voltage which is selectable and reference voltage generating means which is also selectable. The control circuit also includes means to compare the control voltage and the reference voltage and to control current flow through the heating elements.

Claims

1. An electric blanket assembly including a blanket having elements adapted to be heated from an electric supply source and a control circuit assembly adapted to control current through the elements to regulate the heating of the blanket and further adapted to disconnect the supply source from the heating elements under conditions of malfunction of the blanket, characterised in that the control circuit assembly includes temperature sensitive elements suitably located in the blanket and arranged to generate a control voltage, timing means adapted to generate a reference voltage and regulating means to compare the control voltage and the reference voltage and to trigger a solid state switching device which is adapted to control the current through the blanket heating elements.

2. The electric blanket assembly claimed in claim 1 wherein the regulating means includes differential amplifier circuitry, zero crossing detector amplifier circuitry and an output pluse circuit.

3. The electric blanket assembly claimed in claim 2 wherein the control voltage is applied to one input of the differential amplifier and the reference voltage is applied to the other input of the differential amplifier.

4. The electric blanket assembly claimed in claim 3 in which the output pulse circuit is connected to the solid state switching device and is adapted to trigger the latter.

5. The electric blanket assembly claim in claim 4 in which the solid state switching device is a triac.

6. The electric blanket assembly as claimed in claim 1 wherein the reference voltage is of a ramp like nature and is arranged to be cyclic with a preset time period.

7. The electric blanket assembly as claimed in claim 1 wherein the temperature sensitive elements are negative temperature coefficient thermistors.

8. The electric blanket assembly claimed in claim 1 wherein the control circuit assembly includes means to disconnect the supply source from the heating elements under conditions of malfunction of the blanket which is connected to the control voltage generated by the temperature sensitive elements and which is adapted to operate a relay to disconnect the supply from the heating elements, and further including differential amplifier circuitry, zero crossing detector amplifier circuitry and an output pulse circuit.

9. The electric blanket assembly claimed in claim 8 in which the output pulses from the output pulse circuit act to trigger a solid state switching device.

10. The electric blanket assembly claimed in claim 9 in which the solid state switching device is a triac.

11. The electric blanket assembly claimed in claim 1 in which the control circuit assembly includes a visible alarm.

12. The electric blanket assembly claimed in claim 11 in which the alarm is a visible alarm.

13. The electric blanket assembly claimed in claim 11 in which the alarm is visible and audible.

14. The electric blanket assembly claimed in claim 13 wherein the control circuit assembly includes delay circuitry to delay the triggering of the audible alarm.