Safety circuit for electric bedcover

• US 4,281,237 A
• Filed: 03/05/1979
• Issued: 07/28/1981
• Est. Priority Date: 03/05/1979
• Status: Expired due to Term

• Current Assignee: Sunbeam Products, Inc. d/b/a Jarden Consumer Solutions (Newell Brands Inc.)
• Original Assignee: Sunbeam Corp. (Newell Brands Inc.)
• Inventors: Berenson, Allen V.
• Primary Examiner(s): Rubinson, Gene Z.
• Assistant Examiner(s): PASCHALL, MARK H
• Application Number:
  US06/017,509
• Time in Patent Office: 876 Days
• Field of Search: 219/212, 219/490, 219/505, 219/494, 219/504, 219/501, 219/483, 219/508, 337/415
• US Class Current: 219/511
• CPC Class Codes: H02H 5/043 the temperature dependent resistor being disposed parallel to a heating wire, e.g. in a heating blanket
• CPC Class Codes: H05B 1/0227 Applications
• CPC Class Codes: H05B 2203/014 Heaters using resistive wires or cables not provided for in H05B3/54
• CPC Class Codes: H05B 2203/016 Heaters using particular connecting means
• CPC Class Codes: H05B 2203/035 Electrical circuits used in resistive heating apparatus
• CPC Class Codes: H05B 3/34 flexible, e.g. heating nets or webs

Abstract

In an electric bedcover of a type wherein a safety thermostat having a bimetallic element is adapted to deenergize a heater when the bimetallic element is heated sufficiently, as when an overheated condition occurs, an elongated flexible sensor of a type comprising a pair of conductors spaced from each other by a layer of material having a negative temperature coefficient of resistance is adapted to influence the bimetallic element through a resistor, which is mounted for heat dissipation to the bimetallic element, and a first circuit branch comprising the resistor, the conductors, and the layer between the conductors, in series with each other, is connected so as to maintain the conductors at different potentials when the heater operates, and so as to conduct sufficient current to cause the resistor to conduct sufficient heat to cause the bimetallic element to open the contacts when some part of the layer between the conductors is heated so as to act as an electrical conductor having a low impedance rather than as an electrical insulator having a high impedance. Both such circuit branches are confined by a network of serpentine passages within a fabric shell of the electric blanket.

Claims

1. In an electric bedcover of a type comprising

a fabric shell, which has plural plies and a network of serpentine passages within said plies,

an elongated flexible heater, which is deployed throughout at least some of said passages, and

a safety thermostat, which is connected in series with at least part of said heater and with plural conventional thermostats, which is located within said network of serpentine passages, which comprises a bimetallic element and electrical contacts arranged to be opened and closed by said bimetallic element, and which is operative to disconnect at least part of said heater from a source of electrical power at said contacts when said bimetallic element is heated sufficiently and to reconnect the same part of said heater to the source of electrical power through said contacts when said bimetallic element is cooled sufficiently, an improvement wherein an elongated flexible sensor, of a type comprising a pair of elongated flexible electrical conductors spaced from each other by an elongated flexible layer of material having a negative temperature coefficient of resistance, is deployed through at least some of said passages, wherein a resistor is mounted for heat dissipation from said resistor to the bimetallic element of said safety thermostat, and wherein a first circuit branch comprising said resistor, said conductors, and said layer, in series with each other, is confined by and embodied entirely within said network of serpentine passages so as not to require additional leads extending from the fabric shell and connected in parallel with a second circuit branch comprising at least part of said heater so as to maintain said conductors at relatively different electrical potentials at least when said heater operates, so as to conduct essentially no current except when said layer acts as an electrical conductor having low impedance rather than as an electrical insulator having high impedance, and so as to conduct sufficient current to cause said resistor to dissipate sufficient heat to cause said bimetallic element to open said contacts when some part of said layer is heated so as to act as an electrical conductor having low impedance rather than as an electrical insulator having high impedance, whereby said bimetallic element receives essentially no heat from said resistor except when said layer thus acts as an electrical conductor.

2. The improvement of claim 1, in an electric bedcover of said type in which said heater has two parallel branches deployed through at least some separate passages of said passages, in which said safety thermostat cooperates with one such branch of said heater as aforementioned, and in which another safety thermostat having a bimetallic element is provided to cooperate with the other branch of said heater, said improvement wherein a resistor is mounted for heat dissipation to the bimetallic element of the safety thermostat cooperating with said other branch of said heater, wherein said sensor has two branches deployed through at least some passages of said passages, and wherein each such branch of said sensor cooperates with the resistor mounted for heat dissipation to the bimetallic element of the safety thermostat cooperating with one such branch of said heater as aforementioned, whereby one such branch of said heater may operate while the other branch of said heater may be inoperative.

3. The improvement of claim 1, in an electric bedcover of said type in which said heater has two parallel branches deployed through at least some separate passages of said passages and a common return deployed in at least one of said passages, in which said safety thermostat cooperates with one such branch of said heater as aforementioned, and in which another safety thermostat having a bimetallic element is provided to cooperate with the other branch of said heater, said improvement wherein a resistor is mounted for heat dissipation to the bimetallic element of the safety thermostat cooperating with said other branch of said heater, wherein said sensor has two parallel branches deployed through at least some passages of said passages, and wherein each such branch of said sensor cooperates with the resistor mounted for heat dissipation to the bimetallic element of the safety thermostat cooperating with one such branch of said heater as aforementioned, whereby one such branch of said heater and the common return of said heater may operate while the other branch of said heater may be inoperative.