JPS6321116Y2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an electrical safety device for use with carbon sheet heating elements and the like.

(Prior art and its problems) The carbon planar heating element B, which is provided with power supply electrode bands AA along both side edges, has conventionally been temperature controlled using a thermostat C as shown in Fig. 1.
or a thermofuse D... connected to the power supply line EE to the electrode band AA and arranged evenly on the surface of the planar heating element B, or a second
As shown in the figure, a thermosensor wire F was arranged in a meandering manner on the surface of a planar heating element B and was controlled by a controller.

However, in any case, these conventional temperature control methods are not perfect against local overheating, and there is a risk of burning out.
In addition, in this type of sheet heating element, electricity constantly flows from one electrode band A to the other electrode band A over the entire carbon surface b, so cracks may appear in the carbon surface b, and electrode band A When the electrode band is cut, the arc generated by the shot is larger than that of a wire heater, and the current concentration causes overheating at the ends of the crack (U) and the cut side (E) of the electrode band, leading to ignition. There is a danger that the

(Means for solving the problems) The present invention was developed in view of the above-mentioned circumstances, and its purpose is to prevent problems such as local overheating, cracks in the heating surface, or cutting of the electrode strip. The present invention provides a safety device for a planar heating element that prevents the danger of fire, which may occur even in the event of a fire, by cutting off the power supply.

The present invention will be explained below based on the embodiments shown in FIGS. 3 to 5. In the figure, reference numeral 1 is a carbon sheet heating element, which is made by coating a cloth with carbon liquid, weaving electrode bands 2, 2 for power supply along both side edges, and vinyl chloride sheets on the front and back sides. It is constructed by pasting electrically insulating sheets 3, 3 such as the following.

A conductive film 4 made of polyvinyl chloride kneaded with carbon or the like is pasted to the outer surface of the electrically insulating sheets 3, 3 of the carbon planar heating element 1 constructed in this manner. A conductive band 5 made of aluminum foil or copper foil is attached to the center of the conductive film 4, and a lead wire 6 is drawn out from the conductive band 5 and connected to a relay coil 8, which is connected to a relay switch 7. The other ends are connected to respective poles of power supply lead wires 10, 10 via diodes 9, 9. The relay switch 7 is connected to the power supply electrode band 2 of the carbon planar heating element 1 of the power supply lead wires 10, 10.
It is located between 2. Note that 11 is a capacitor, and 13 is a diode for preventing malfunction. 1
4 is a diode, and 15 is a resistor. Incidentally, the conductive film 4 may be attached to both sides of the carbon planar heating element 1.

(Function) The safety device configured as described above is designed so that, in the unlikely event that a seat cushion or folded blanket that generates a large amount of heat is placed in a local area of the planar heating element 1, a thermostat, thermoswitch, or sensor wire is activated. When the electrically insulating sheets 3, 3 become carbonized when they are overheated without working, the conductive film 4 receives a leakage current from the planar heating element 1, and this current flows into the conductive band 5. , the relay coil 8 is operated, and the switch 7 is operated to open the circuit and cut off the power supply to the planar heating element 1, thereby preventing an accident from occurring without causing a fire.

Furthermore, when cracks occur in the planar heating element 1 or when the electrode bands 2 are cut into a shot state and an arc is generated, current will be passed through the conductive film 4. Similarly to the above, the relay switch 7 operates to cut off the power supply to the planar heating element 1, thereby preventing a fire accident.

(Effects) As described above, according to the present invention, when the sheet heating element locally overheats due to trapped heat, when the electrode band is cut and becomes short, or when cracks occur on the heating surface and short occurs, When this occurs, the leakage current is sensed and the power to the heating element is cut off, making it possible to prevent burnout accidents due to overheating and shot arc, and to ensure safety. It can be used for

In the above embodiment, a conductive film made of polyvinyl chloride mixed with carbon is placed on the insulating sheet of the planar heating element, so it has good bending and fitting properties, excellent strength, and is easy to use.

Furthermore, the conductive film is melted and fused due to sparks or abnormal heating caused by the shot, so that leakage current is ensured and the relay switch operates perfectly.

Furthermore, in the case of a configuration in which a thermosensor wire F is provided as shown in FIG. 2, a relay switch 7 is provided between the lead wires to the controller 12 as shown in FIG. 6, and by cutting off or shorting the signal to the controller 12, the sensor wire breakage alarm circuit of the controller is operated, thereby cutting off the power supply to the sheet heating element.
This also makes it possible to achieve the object of the present invention.

[Brief explanation of the drawing]

1 and 2 of the drawings are perspective views for explaining a conventional control method for a planar heating element, and FIGS. 3 to 6 show an embodiment of the present invention. A perspective view of a planar heating element equipped with a safety device according to the above, FIG. 4 is a sectional view of the same, and FIG. 5 is an electric circuit diagram.
FIG. 6 is a circuit diagram according to another embodiment. DESCRIPTION OF SYMBOLS 1...Carbon planar heating element, 2...Electrode band for power supply, 3...Electrical insulating sheet, 4...Conductive film, 7...Relay switch, 8...Relay coil, 9...Diode, F ...Thermo sensor wire.

Claims (1)

[Scope of utility model registration request] A planar heating element with electrode strips for power supply along both side edges and electrically insulated on the front and back sides by an insulating sheet.A conductive material made of polyvinyl chloride or the like kneaded with carbon on the outer surface of the insulating sheet. A conductive film is pasted, and a conductive band made of copper foil or aluminum foil is pasted to the center of this conductive film and provided as a power supply input path to the sheet heating element or a lead wire to the temperature sensing wire. A safety device using a sheet heating element in which one end of the coil of a relay switch is connected, and the other end of the coil is connected to each pole of the power supply input path via a diode.