Electrical heating apparatus protected against an overheating condition

Claim 2

An electrical heating apparatus protected against an overheating condition and comprising an electrical heating means for generating heat in proportion to the amount of electrical current flowing therethrough, said heating means providing essentially all of the heat for the apparatus; a heat sensitive means in a thermally responsive relationship with respect to said electrical heating means for monitoring the heat generated by said electrical heating means and for providing a signal in response to an overheating condition, said heat sensitive means consisting of a single conductor having positive temperature coefficient electrical impedance characteristics continuously along its entire length so that it may detect an overheating condition at any position along its entire length; and control means associated with said electrical heating means and said heat sensitive conductor for controlling the electrical current flowing through said electrical heating means in response to a signal from said heat sensitive conductor.

Claim 3

The apparatus of claim 1 wherein said control means comprises semiconductor switch means electrically connected in series with said electrical heating means.

Claim 4

The apparatus of claim 1 wherein said control means comprises gate controlled semiconductor means having terminals electrically connected in series with said electrical heating means and a gate terminal electrically connected to said heat sensitive conductor.

Claim 5

The apparatus of claim 1 wherein said control means comprises a pair of gate controlled bidirectional semiconductor switches connected to one another in series, means connecting said pair of semiconductor switches in series to said electrical heating means for permitting either one to control the electrical current flowing through said electrical heating means, means electrically connecting the gate of one of said semiconductor switches to a terminal of said other semiconductor switch through said positive temperature coefficient heat sensitive single conductor and means electrically connecting the gate of said other semiconductor switch to a terminal of said one of said semiconductor switches for triggering the semiconductor switches in response to the sensing of an overheating condition.

Claim 6

The apparatus of claim 1 wherein said electrical heating means and said heat sensitive conductor are substantially coextensive.

Claim 7

The apparatus of claim 5 wherein said electrical heating means and said heat sensitive conductor are coaxially disposed with respect to one another.

Claim 8

The apparatus of claim 6 further including a core strand for reinforcement, said heating means being disposed closer to said core strand.

Claim 9

The apparatus of claim 1 wherein said electrical heating means and said heat sensitive conductor are disposed in side-by-side relation.

Claim 10

The apparatus of claim 8 further including a core strand for reinforcement and a jacket encasing said core strand said electrica1 heating means and said heat sensitive conductor to form a single strand.

Claim 11

The apparatus of claim 4 wherein said semiconductor switches are connected in front-to-front (MT 1 to MT 1 ) orientation.

Claim 12

The apparatus of claim 1 further comprising a jacket encasing both said electrical heating means and said heat sensitive conductor to form a single strand.

Claim 13

An electrical heating apparatus protected against an overheating condition and comprising an elongate electrical heating means for generating heat in proportion to the amount of electrical current flowing therethrough, said heating means providing essentially all of the heat for the apparatus; an elongate heat sensitive means in a thermally responsive relationship with respect to said electrical heating means for monitoring the heat generated by said electrical heating means and for providing a signal in response to an overheating condition, said heat sensitive means consisting of a single conductor having positive temperature coefficient electrical impedance characteristics continuously along its entire length so that it may detect an overheating condition at any position along its entire length, said heat sensitive conductor being coextensive with said electrical heating means; and control means associated with said electrical heating means and said heat sensitive conductor for controlling the electrical current flowing through said electrical heating means in response to a signal from said heat sensitive conductor, said control means comprising gate controlled semiconductor switch means having terminals electrically connected in series with said electrical heating means and a gate terminal electrically connected to said heat sensitive conductor for selectively controlling the flow of electrical current through said electrical heating means when an overheating condition is detected by said heat sensitive conductor.

Claim 14

An electrical heating apparatus protected against an overheating condition and comprising an elongate electrical heating means for generating heat in proportion to the amount of electrical current flowing therethrough, said heating means providing essentially all of the heat for the apparatus; an elongate heat sensitive means in a thermally responsive relationship with respect to said electrical heating means for monitoring the heat generated by said electrical heating means and for providing a signal in response to an overheating condition, said heat sensitive means consisting of a single conductor having positive temperature coefficient electrical impedance characteristics continuously along its entire length so that it may detect an overheating condition at any position along its entire length, said heat sensitive conductor being coextensive with said electrical heating means; and control means associated with said electrical heating means and said heat sensitive conductor for controlling the electrical current flowing through said electrical heating means in response to a signal from said heat sensitive conductor, said control means comprising gate controlled semiconductor switch means having terminals electrically connected in series with said electrical heating means and a gate terminal electrically connected to said heat sensitive conductor for selectively controlling the flow of electrical current through said electrical heating means when an overheating condition is detected by said heat sensitive conductor.

Claim 15

The apparatus of claim 12 wherein said control means comprises a pair of gate controlled bidirectional semiconductor switches connected to one another in series, means connecting said pair of semiconductor switches in series to said electrical heating means for permitting either one to control the electrical current flowing through said electrical heating means, means electrically connecting the gate of one of said semiconductor switches to a terminal of said other semiconductor switch through positive temperature coefficient heat sensitive conductor and means electrically connecting the gate of said other semiconductor switch to a terminal of said one of said semiconductor switches for triggering the semiconductor switches in response to the sensing of an overheating condition.

Claim 16

The apparatus of claim 12 wherein said electrical heating means and said heat sensitive conductor are coaxially disposed with respect to one another.

Claim 17

The apparatus of claim 12 wherein said electrical heating means and said heat sensitive conductor are disposed in side-by-side relation.

Claim 18

The apparatus of claim 12 wherein said semiconductor switches are connected in front-to-front (MT 1 to MT 1 ) orientation.

Claim 19

The apparatus of claim 12 further comprising a jacket encasing both said electrical heating means and said heat sensitive conductor to form a single strand.

Claim 20

The apparatus of claim 12 wherein said heat sensitive conductor further includes spaced bands of conductive material on the outer surface of said heat sensitive conductor to lower the resistivity of said heat sensitive conductor along its length.

Claim 21

An electrically heated bedcover protected against an overheating condition and comprising a bedcover; electrical heating means in said bedcover for generating heat in proportion to the amount of electrical current flowing therethrough, said heating means providing essentially all of the heat for the bedcover; heat sensitive means in a thermally responsive relationship with respect to said electrical heating means and for providing a signal in response to an overheating condition, said heat sensitive means consisting of a single conductor having positive temperature coefficient electrical impedance characteristics continuously along its entire length so that it may detect an overheating condition at any position along its entire length; and control means associated with said electrical heating means and said heat sensitive conductor for controlling the electrical current flowing through said electrical heating means in response to a signal from said heat sensitive conductor.

Claim 22

An electrically heated bedcover protected against an overheating condition and comprising a bedcover; electrical heating means in said bedcover for generating heat in proportion to the amount of electrical current flowing therethrough, said heating means providing essentially all of the heat for the bedcover; heat sensitive means in a thermally responsive relationship with respect to said electrical heating means and for providing a signal in response to an overheating condition, said heat sensitive means consisting of a single conductor having positive temperature coefficient electrical impedance characteristics continuously along its entire length so that it may detect an overheating condition at any position along its entire length; and control means associated with said electrical heating means and said heat sensitive conductor for controlling the electrical current flowing through said electrical heating means in response to a signal from said heat sensitive conductor.

Claim 23

The apparatus of claim 19 wherein said control means comprises semiconductor switch means electrically connected in series with said electrical heating means.

Claim 24

The apparatus of claim 19 wherein said control means comprises gate controlled semiconductor means having terminals electrically connected in series with said electrical heating means and a gate terminal electrically connected to said heat sensitive conductor.

Claim 25

The apparatus of claim 19 wherein said control means comprises a pair of gate controlled bidirectional semiconductor switches connected to one another in series, means connecting said pair of semiconductor switches in series to said electrical heating means for permitting either one to control the electrical current flowing through said electrical heating means, means electrically connecting the gate of one of said semiconductor switches to a terminal of said other semiconductor switch through positive temperature coefficient heat sensitive single conductor and means electrically connecting the gate of said other semiconductor switch to a terminal of said one of said semiconductor switches for triggering the semiconductor switches in response to the sensing of an overheating condition.

Claim 26

The apparatus of claim 19 wherein said electrical heating means and said heat sensitive conductor are substantially coextensive.

Claim 27

The apparatus of claim 23 wherein said electrical heating means and said heat sensitive conductor are coaxially disposed with respect to one another.

Claim 28

The apparatus of claim 24 further including a core strand for reinforcement, said heating means being disposed closer to said core strand.

Claim 29

The apparatus of claim 19 wherein said electrical heating means and said heat sensitive conductor are disposed in side-by-side relation.

Claim 30

The apparatus of claim 26 further including a core strand for reinforcement and a jacket encasing said core strand, said electrical heating means and said heat sensitive conductor to form a single strand.

Claim 31

The apparatus of claim 22 wherein said semiconductor switches are connected in front-to-front (MT 1 to MT 1 ) orientation.

Claim 32

The apparatus of claim 19 further comprising a jacket encasing both said electrical heating means and said heat sensitive conductor to form a single strand.