Electric heating – Heating devices – With heating unit structure
Reexamination Certificate
1999-08-19
2002-05-14
Hoang, Tu Ba (Department: 3742)
Electric heating
Heating devices
With heating unit structure
C219S546000, C219S549000, C219S553000
Reexamination Certificate
active
06388237
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a heater cable in combination with a lead cable. More particularly, the invention relates to a wiring pattern which is capable of minimizing the generation of leak magnetic field from the heater cable.
2. Description of the Prior Art
A conventional sheet-like heating appliance such as an electric blanket or an electric carpet is fabricated by wiring a heater cable
40
and a sensor cable
50
in a combination in a carpet fabric material; for example, the heater cable
40
comprising, as shown in
FIG. 15
, a heating element wire
32
wound in a spiral at intervals of a given distance on the outer surface of a polyester core thread
31
, a fusing layer
33
of nylon or polyester provided over the heating element wire
32
, a short-circuit wire
34
wound in a spiral on the outer surface of the fusing layer
33
, and a protective coating
35
of polyvinyl chloride (PVC) provided over the short-circuit wire
34
, and the sensor cable
50
comprising, as shown in
FIG. 16
, a signal wire
42
wound in a spiral on the outer surface of a polyester core thread
41
, a fusing layer
43
provided over the signal wire
42
, another signal wire
44
wound in a spiral on the outer surface of the fusing layer
43
, and a protective coating
45
provided over the signal wire
44
.
In such a conventional sheet-like heating appliance when turned on, the heating element wire
32
of the heater cable
40
only is supplied with a flow of current.
The fusing layer
33
and
43
have a so-called fusing function (fuse action) that when the heater cable
40
is overheated with a sensor wire
50
on the sheet-like heating body malfunctioning and its temperature locally rises up close to the melting point of a resin material of the fusing layer
33
and
43
(referred to as a fusing layer material hereinafter), the fusing layer material is softened or fused to short-circuit between the heating element wire
32
and the short-circuit wire
34
, and the signal wires
42
and
44
, and to disconnect the power supply. More particularly, the fusing layer
33
and
43
are designed to act as finally a safety circuit for protecting the sheet-like heating body from being overheated.
The polyamide resin, such as nylon-12, which is used in the fusing layer
33
and
43
have acceptable levels of molding formability, mechanical properties, and thermal properties required for the fusing layer material.
When the heater cable
40
of the conventional appliance arranged in a known pattern is energized, the current which flows in the heater cable
40
may generate a leak magnetic field. Consequently, high frequencies of the leak magnetic field develop a magnetic noise which gives adverse effects over the other electric appliances. It is now said that low frequencies may also affect the human body. Therefore, those problems are particularly emphasized in the conventional sheet-like heating appliances, namely electric blankets and carpets, for warming the human body.
SUMMARY OF THE INVENTION
The present invention has been schemed for solving the above problems of the prior art and its object is to provide a wiring pattern which is capable of diminishing the leak magnetic field from the heater cable, as preferably applicable to a sheet-like heating appliance such an electric blanket or an electric carpet.
As a first feature of the present invention, a heater cable in combination with a lead cable, in which the heater cable comprising a heating element wire wound in a spiral on the outer surface of a core thread, a fusing layer coated over the heating element wire, a signal wire wound in a spiral on the outer surface of the fusing layer and a protective coating provided over the signal wire, the lead cable comprising a conductive wire covered at its outer surface with an insulating coating, and the heater cable and the lead cable are formed such a pattern that the heater cable and the lead cable are spaced by a predetermined distance L from each other and are capable to be supplied with opposite flows of current is provided.
In the heater cable in combination with the lead cable according to the first feature of the present invention, the two opposite flows of current introduced into the heater cable
10
and the lead cable
20
respectively permit their induced intensities of magnetic field to be offset by each other, hence diminishing the leak magnetic field.
As a second feature of the present invention is a heater cable in combination with a lead cable, wherein the distance L is not greater than 10 mm.
In the heater cable in combination with the lead cable according to the second feature of the present invention, the distance L between the heater cable
10
and the lead cable
20
which are uniformly spaced from each other in the wiring pattern is set not greater than 10 mm, thus effectively diminishing the leak magnetic field. It is desired that the above mentioned fusing layer comprises copolymer polyester resin which has the following characteristics (a) and/or (b) and (c) to (f).
(a) The angle &agr; between the baseline and a tangent to the heat absorption peak of a Differential Scanning Colorimetry (DSC) curve defined by a Japanese Industrial Standard (JIS) K7121 (ISO 3146) method is 90° to 120°.
(b) The angle &agr;′ between the baseline and a tangent to the shift portion of a ThermoMechanical Analysis (TMA) curve determined in an expansion mode by a thermal-mechanical measuring method is 90° to 100°.
(c) The melting point is 160° C. to 210° C.
(d) The reduction viscosity is not lower than 0.5 dl/g.
(e) The moisture absorption is not higher than 1.0% at a temperature of 20° C. and a relative moisture rate of 65%.
(f) The hardness measured by a JIS K7215 (ISO 868) method is Hardness Degree (HDD) 40 to 74.
Also, it is desired that the anti-heat deterioration of the resin of the fusing layer stand for 500 hours at a temperature of 140° C.
The composition of the above mentioned copolymer polyester resin is now explained in more detail. One of its acid components is aromatic dicarboxylic acid which may be selected from terephthalic acid, isophthalic acid, 2-6-naphthalenedicaboxylic acid, biphenyldicarboxylic acid, so on and their ester. Similarly, its aliphatic dicarboxylic acid component having 2 to 20 carbon atoms may be selected from succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanedionic acid, dimer acid, so on and their ester. Its alicyclic dicarboxylic acid component may be selected from 1.4-cyclohexanedicarboxylic acid, so on and its ester. Its hydroxy-carboxylic acid component may be selected form p-hydroxy-aromatic acid, so on and its ester.
Its glycol component is aliphatic glycol which may be selected from 1,4-butanediol, 1,3-butanediol, 1,2-butanediol, ethylene glycol, propylene glycol, 1,2-propanediol, 1,3-propanediol, 1,5-pentadiol, 3-metyl-1,5-pentadiol, 1,9-nonanediol, 1,6-hexanediol, doracanedionic acid, neopentyl glycol, neopentyl glycol hydroxy pivalate, 2-ethyl-2-butylpropanediol, and bisphenol-A-ethylene-oxide or -propylene-oxide derivative, so on.
Other copolymer components than the above mentioned are glycol such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, so on, &egr;-caprolactone, hyroxycapronic acid, polycaprolactone, and tricyclodecanedimethylol, so on.
The above materials may arbitrarily be combined in a desired combination or ratio without departing from the characteristics (a) to (f) defined above to produce a type of the copolymer polyester resin according to the present invention. The copolymer polyester resin of the present invention may be added, if desired, with anti-oxidation agents, stabilizers, anti-copper agents, non-organic fillers, nucleating agents, surface activators, anti-static agents, flame-retardants, plasticizers, and thickening agents, so on.
Thermoplastic resins are generally classified into crystalline polymer and non-crystalline polymer depending on their molecular structures. Such polymers have a wide range of melti
Aoki Hidekazu
Koiwai Kazuhiko
Miyahara Shouhei
Mizumura Yutaka
Nakajima Atsushi
Hoang Tu Ba
Jordan and Hamburg LLP
Totoku Electric Co., Ltd.
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