Electric resistance heating devices – Heating devices – Radiant heater
Reexamination Certificate
2001-07-26
2003-11-25
Jeffery, John A. (Department: 3742)
Electric resistance heating devices
Heating devices
Radiant heater
C219S553000, C219S541000, C313S110000
Reexamination Certificate
active
06654549
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an infrared ray lamp to be used for a heater for heating objects and a space heater for heating rooms, etc. (hereinafter referred to as a heating apparatus), more particularly to an infrared ray lamp having good functions as a heat source by using a carbon-based substance as a heating element, to a heating apparatus using the infrared ray lamp, and to a method of producing the infrared ray lamp.
BACKGROUND ART
A conventional infrared ray lamp causes a problem wherein its power consumption increases abnormally after use for a long time, and its heating portions fuse and break in some cases. This problem will be described below.
As an infrared ray lamp conventionally used as a heat source, an infrared ray lamp having a tungsten spiral filament held at the central portion of a glass tube by a number of supports of tungsten is used. However, the infrared ray emission rate of the tungsten is so low as, 30 to 39%, and the rush current at the time of turning on is high. Furthermore, it is necessary to use a number of the tungsten supports for holding the tungsten spiral filament at the central portion of the glass tube, and the assembly work for them was not easy. In particular, sealing the plural tungsten spiral filaments in the glass tube in order to obtain high output was very difficult.
In order to solve these problems, an infrared ray lamp, wherein a carbon-based substance formed into a rod shape is used instead of the tungsten spiral filaments as a heating element, has been proposed conventionally. As such a conventional infrared ray lamp, an infrared ray lamp disclosed in Japanese Published Unexamined Patent Application, Publication No. Hei 11-54092 applied by the same applicant as that of the present invention is available. Since the carbon-based substance has a high infrared ray emission rate of 78 to 84%, the infrared ray emission rate of the infrared ray lamp also becomes high by using the carbon-based substance as a heating element. Furthermore, since the carbon-based substance has a negative resistance temperature characteristic wherein its resistance value lowers as the temperature rises, the carbon-based substance has a significant characteristic of capable of reducing its rush current at the time of turning on.
FIGS. 20 and 21
are front views showing the conventional infrared ray lamp described in Japanese Published Unexamined Patent Application, Publication No. Hei 11-54092, wherein the carbon-based substance is used as a heating element. Part (a) of
FIG. 20
is a view showing the structure of the lead wire taking-out portion of the conventional infrared ray lamp in which a heating element
200
is sealed inside a glass tube
100
. Part (b) of
FIG. 20
is a partially magnified view showing the connection portion between the heating element
200
and the lead wire
104
of the infrared ray lamp shown in the part (a) of FIG.
20
.
FIG. 21
is a partially magnified view showing the connection portion between the two heating elements
200
a
and
200
b
and the lead wire
104
of the conventional infrared ray lamp in which the two heating elements
200
a
and
200
b
are sealed inside the glass tube. The part (a) of
FIG. 20
shows the structure of one end of the infrared ray lamp, and the other end of the infrared ray lamp has similar structure. Furthermore, the structure of the infrared ray lamp shown in
FIG. 21
is similar to that shown in the part (a) of
FIG. 20
, except for the connection portion between the two heating elements
200
a
and
200
b
and the lead wire
104
shown in the figure.
As shown in the part (a) of
FIG. 20
, in the conventional infrared ray lamp, a metal wire
102
wound in a coil shape is wound around the end of the heating element
200
formed of a carbon-based substance and formed into a rod shape. The end portion of the coil-shaped metal wire
102
is covered with a metal foil sleeve
103
, and this metal foil sleeve
103
is secured to the end of the heating element
200
by crimping. The internal lead wire
104
formed of a metal wire and having a coil portion
105
wound in a coil-spring shape in the middle of the wire is electrically bonded to one end of the metal foil sleeve
103
. One end of a molybdenum foil sheet
107
is spot-welded to the other end of the internal lead wire
104
. Furthermore, an external lead wire
108
formed of a molybdenum wire is welded to the other end of the molybdenum foil sheet
107
. The heating element
200
, the metal foil sleeve
103
, the internal lead wire
104
, the molybdenum foil sheet
107
and the external lead wire
108
connected in series as described above are inserted into the glass tube
100
and disposed therein. An inert gas, such as argon, nitrogen or the like, is sealed inside the glass tube
100
, the glass tube
100
is fused and bonded at the portion of the molybdenum foil sheet
107
, thereby completing an infrared ray lamp.
FIG. 21
is a perspective view showing the inside of another conventional infrared ray lamp and showing the structure of the connection portion between the two heating elements
200
a
and
200
b
and the metal lead wire
104
of the conventional infrared ray lamp. As shown in
FIG. 21
, this conventional infrared ray lamp has a structure wherein the two heating elements
200
a
and
200
b
are sealed in one glass tube (not shown). In the infrared ray lamp shown in
FIG. 21
, coil-shaped metal wires
102
a
and
102
b
are wound around the end portions of the heating element
200
a
and
200
b
respectively, and metal foil sleeves
106
are fitted over the wires. The fitted metal foil sleeves
106
are secured to the end portions of the heating elements
200
a
and
200
b
by crimping. The metal lead wire
104
having a coil portion
105
wound in a coil-spring shape in the middle of the wire is electrically connected to the metal foil sleeves
106
.
The infrared ray lamps having the above-mentioned structures have good infrared ray emission rates, since their heating elements are formed of a carbon-based substance; but, there are the following problems.
In the conventional infrared ray lamp having the structure shown in
FIG. 20
, for the lamp of large wattage of the infrared ray lamp, that is, for the lamp of a large power consumption, the coil-shaped metal wire
102
is heated to a high temperature. As a result, when the infrared ray lamp having this structure is used for a long time, the contact resistance of the connection portion among the heating element
200
, the coil-shaped metal wire
102
and the metal foil sleeve
103
increases because of the temperature rise. The conventional infrared ray lamp therefore has the problem of abnormal heating at the connection portion. Furthermore, if the temperature at the connection portion between the coil-shaped metal wire
102
and the metal foil sleeve
103
rises continuously for a long time, the temperature at the bonding portion may rise high and, in the worst case, the bonding portion may fuse and break. Moreover, the stress caused by heat cycles due to the difference in thermal expansion coefficient between the heating element
200
and the coil-shaped metal wire
102
is added, and the contact resistance becomes higher than the value at the beginning of use, whereby the temperature rise at the connection portion is accelerated.
In addition, in the structure of the infrared ray lamp having the two heating elements
200
a
and
200
b
shown in
FIG. 21
, the following problems are caused.
In the process wherein both ends of the two heating elements
200
a
and
200
b
are crimped by using the metal foil sleeve
106
, no problem occurs if the two heating elements
200
a
and
200
b
are crimped by a uniform tension or compression force; however, crimping may occur in a state of an unbalanced tension or compression force. In the conventional infrared ray lamp undergone crimping in such away, if the heating elements
200
a
and
200
b
are heated, the two heating elements
200
a
and
200
b
expand thermally in different states. For this reason, the imb
Jeffery John A.
Matsushita Electric - Industrial Co., Ltd.
Pearne & Gordon LLP
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