ELECTRIC BLANKETS

• US 3,591,765 A
• Filed: 05/19/1969
• Issued: 07/06/1971
• Est. Priority Date: 06/17/1968
• Status: Expired due to Term

• Current Assignee: Leonard C. Owers
• Original Assignee: Leonard C. Owers
• Inventors: Owers, Leonard C.
• Application Number:
  US04/828,092
• Time in Patent Office: 778 Days
• US Class Current: 219/212
• CPC Class Codes: H05B 1/0213 using bimetallic elements
• CPC Class Codes: H05B 2203/014 Heaters using resistive wires or cables not provided for in H05B3/54
• CPC Class Codes: H05B 2203/017 Manufacturing methods or apparatus for heaters
• CPC Class Codes: H05B 2203/035 Electrical circuits used in resistive heating apparatus
• CPC Class Codes: H05B 3/342 heaters used in textiles

Abstract

A circuit for an electric blanket or an electrically heated pad has two heater elements. The circuit is such that these heater elements can either be connected directly to a source of supply, or indirectly by way of a transformer.

Claims

1. An electric blanket including a circuit comprising two heater elements, a transformer having a primary winding and a secondary winding, a pair of terminal across which a source of electric power can be connected, first switch means having a first condition in which said elements are connected across said terminals and a second condition in which said elements are connected across the secondary winding of the transformer and the primary winding is connected across said terminals, and second switch means which acts as a temperature control, the circuit being such that the root mean square current in the second switch means is the same whether the first switch means is in the first or the second condition.

2. A blanket according to claim 1 wheRein the two heater elements are wound together as a dual-concentric cable.

3. A blanket according to claim 2 wherein a rectifier element is connected in series between the heater elements to form with a fuse a protective arrangement such that if a short circuit occurs between the heater elements in the cable the rectifier element is shorted out of the circuit and there is a large increase in the current in the fuse.

4. An electric blanket including a circuit comprising two heater elements wound together as a dual-concentric cable, a transformer having a primary winding and a secondary winding, a pair of terminals across which a source of electric power can be connected, switch means having a first condition in which said elements are connected across said terminals and a second condition in which said elements are connected across the secondary winding of the transformer and the primary winding is connected across said terminals, a rectifier element connected in series between the heater elements, and a fuse which forms with the rectifier element a protective arrangement such that if a short circuit occurs between the heater elements in the cable, the rectifier element is shorted out of the circuit and there is an increase in the current through the fuse sufficient to open circuit the fuse and to terminate the delivery of current to the heater elements.