Abstrict
An electric heater comprises a braid construction of a plurality
of strands having electric resistance, thereby the strands are heated
due to a Joule heat when a current flows therethrough. The strands
are braided with a core wire of tube or without cores. These strands
are placed in two core wires dielectrically insulated, which core
wires have exposed portions formed therein in a shape of semi-circle
or arc-like at a regular interval mutually. The core wires are covered
with an insulator laid thereon and an electric heating element is
wound around the insulator covering in a large spiral. A C-shaped
fixing piece made of metal is used to be adapted on the exposed
portions of the core wires. Then the opening of the C shape of the
fixing piece is pressed toward each other to close it. Claws, formed
on the inner face of the fixing piece, grip firmly the strands of
the heater element to the core wires.
Claims
What is claimed is:
1. A heat generating cable comprising:
a feeder line comprising at least two insulatedly covered core
wires, each of said wires have an insulated cover and being arranged
parallel to each other and having a plurality of exposed portions
of said core wires made by cutting off a predetermined zone width
of said insulating cover cyclically in a semi-ring shape at a predetermined
interval at alternatively different longitudinal positions;
a resistance comprising a single or a plurality of resistance strands
constructed to form a braid structure around said feeder line;
a connector comprising a single or a plurality of conductive elemental
wires braided in a beltlike shape to form a braid structure and
wound around said resistance and said feeder line width-wise at
the position of each of said exposed portions of said core wires
to press said resistance against and into electric connection with
said core wires at multiple points thereby defining a plurality
of consecutive heating zones of said resistance formed at the joint
portions of said resistance and said core wires along said feeder
line and corresponding to said zone width; and
a further insulator circumferentially covering said connectors,
said resistance and said feeder line altogether to form a single
cable;
whereby said resistance of the braid structure is heated at every
said heating zone due to a Joule effect by the flow of current through
said feeder line of said cable.
2. A heat generating cable according to claim 1, wherein said feeder
line comprises two wires and is connected to a single-phase alternating
current source.
3. A heat generating cable according to claim 1, wherein said feeder
line comprises three wires and is connected to a three-phase alternating
current source.
4. A heat generating cable comprising:
a feeder line comprising at least two insulatedly covered core
wires, each of said wires have an insulated cover and being arranged
parallel to each other and having a plurality of exposed portions
of said core wires made by cutting off a predetermined zone width
of said insulating cover cyclically in a semi-ring shape at a predetermined
interval at alternately different longitudinal positions;
a resistance comprising a single or a plurality of resistance strands
constructed to form a braid structure around said feeder line;
a connector comprising a single or a plurality of conductive elemental
wires braided in a beltlike shape to form a braid structure and
wound around said resistance and said feeder line width-wise at
the position of each of said exposed portions of said core wires
to press said resistance against and into electric connection with
said core wires at multiple points thereby defining a plurality
of consecutive heating zones of said resistance formed at the joint
portions of said resistance and said core wires along said feeder
line and corresponding to said zone width;
a C-shaped fixing piece having the same width as said exposed portions
of said feeder line and having a plurality of claws on its inner
surface to project therefrom to narrowingly press said resistance
from above said connector said resistance against said feeder line
and electrically connect thereto at the position of each said exposed
portion; and
an insulator circumferentially covering said fixing pieces, said
connectors, said resistance and said feeder line altogether to form
a single cable;
whereby said resistance or the braid structure is heated at every
said heating zone due to Joule effect by the flow of current through
said feeder line.
5. A heat generating cable according to claim 4, wherein said feeder
line comprises two wires and is connected to a single-phase alternating
current source.
6. A heat generating cable according to claim 4, wherein said feeder
line comprises three wires and is connected to a three-phase alternating
current source.
7. A heat generating cable comprising:
a feeder line comprising at least two insulating covered core wires
each of said wires have an insulated cover and being arranged parallel
to each other and having a plurality of exposed portions of said
core wires made by cutting off a predetermined zone width of said
insulating cover cyclically in a semi-ring shape at a predetermined
interval at alternately longitudinal positions;
a resistance comprising a single or a plurality of resistance strands
constructed to form a braid structure around said feeder line;
a connector comprising a single or a plurality of conductive elemental
wires braided in a beltlike shape to form a braid structure and
wound around said resistance and said feeder line width-wise at
the position of each of said exposed portions of said core wires
to press said resistance against and into electric connection with
said core wires at multiple points thereby defining a plurality
of consecutive heating zones of said resistance formed at the joint
portions of said resistance and said core wires along said feeder
line and corresponding to said zone width;
a C-shaped fixing piece having the same width as said exposed portions
of said feeder line and having a plurality of claws on its inner
surface to project therefrom to narrowingly press from above said
connector said resistance against and into electric connection with
said feeder line at the position of each said exposed portion;
an insulator circumferentially covering said fixing pieces, said
connectors, said resistance and said feeder line altogether; and
an outer covering comprising a stainless steel sheath wound around
said insulator to enclose the outermost layer to form a single cable;
whereby said resistance of the braid structure is heated at every
said heating zone due to a Joule effect by the flow of current through
said feeder line of said cable.
8. A heat generating cable according to claim 7, wherein said feeder
line comprises two wires and is connected to a single-phase alternating
current source.
9. A heat generating cable according to claim 7, wherein said feeder
line comprises three wires and is connected to a three-phase alternating
current source.
10. A heat generating cable comprising:
a feeder line comprising at least two insulatedly covered core
wires each of said wires have an insulated cover and being arranged
parallel to each other and having a plurality of exposed portions
of said core wires made by cutting off a predetermined zone on width
of said insulating cover cyclically in a semi-ring shape at a predetermined
interval at alternately different longitudinal positions;
a resistance comprising a plurality of resistance elemental wires
braided in a beltlike shape to form a braid structure and arranged
parallelly along a longitudinal direction of said feeder line so
as to come into multi-point contact at the positions of said exposed
portions of said feeder line to make electric connection to said
feeder line;
a connector comprising a single or a plurality of conductive elemental
wires braided in a beltlike shape to form a braid structure and
wound around said resistance and said feeder line width-wise at
the position of each of said exposed positions of said core wires
to come into multi-point contact with said resistance and electrically
connect said resistance to said core wires thereby defining a plurality
of consecutive heating zones of said resistance formed at the joint
portions of said resistance and said core wires along said feeder
line and corresponding to said zone width; and
an insulator circumferentially covering said connectors, said resistance
and said feeder line altogether to form a single cable;
whereby said resistance of the braid structure is heated at every
said heating zone due to a Joule effect by the flow of current through
said feeder line of said cable thereby heating an object to be heated.
11. A heat generating cable according to claim 10, wherein said
feeder line comprises two wires and is connected to a single-phase
alternating current source.
12. A heat generating cable according to claim 10, wherein said
feeder line comprises three wires and is connected to a three-phase
alternating current source.
13. A heat generating cable comprising:
a feeder line comprising at least two insulatedly covered core
wires each of said wires have an insulated cover and being arranged
parallel to each other and having a plurality of exposed portions
of said core wires made by cutting off a predetermined zone width
of said insulating cover cyclically in a semi-ring shape at a predetermined
interval at alternately different longitudinal positions;
a resistance comprising a plurality of resistance elemental wires
braided in a beltlike shape to form a braid structure and arranged
parallelly along a longitudinal direction of said feeder line so
as to come into multi-point contact at the positions of said exposed
portions of said feeder line to make electric connection to said
feeder line;
a connector comprising a single or a plurality of conductive elemental
wires braided in a beltlike shape to form a braid structure and
wound around said resistance and said feeder line width-wise at
the position of each of said exposed positions of said core wires
to come into multi-point contact with said resistance and electrically
connect said resistance to said core wires thereby defining a plurality
of consecutive heating zones of said resistance at the joint portions
of said resistance and said core wires along said feeder line and
corresponding to said zone width;
a C-shaped fixing piece having the same width as said exposed portions
of said feeder line and having a plurality of claws on its inner
surface to project therefrom to narrowingly press and electrically
connect said connector to said feeder line at the position of each
exposed portion; and
an insulator circumferentially covering said fixing piece, said
connector, said resistance and said feeder line together to form
a single cable;
whereby said resistance of the braid structure is heated at every
said heating zone due to a Joule effect by the flow of current through
said feeder line of said cable thereby heating an object to be heated.
14. A heat generating cable according to claim 13, wherein said
feeder line comprise two wires and is connected to a single-phase
alternating current source.
15. A heat generating cable according to claim 13, wherein said
feeder line comprise three wires and is connected to a three-phase
alternating current source.
16. A heat generating cable comprising:
a feeder line comprising at least two insulatedly covered core
wires each of said wires have an insulated cover and being arranged
parallel to each other and having a plurality of exposed portions
of said core wires made by cutting off a predetermined zone width
of said insulating cover cyclically at a predetermined interval
at alternately different longitudinal positions;
a resistance comprising a plurality of resistance elemental wires
braided in a beltlike shape to form a braid structure and arranged
parallelly along a longitudinal direction of said feeder line so
as to come into multi-point contact at the positions of said exposed
portions of said feeder line to make electric connection to said
feeder line;
a connector comprising a single or a plurality of conductive elemental
wires braided in a beltlike shape to form a braid structure and
wound around said resistance and said feeder line width-wise at
the position of each of said exposed portions of said core wires
to come into multi-point contact with said resistance and electrically
connect said resistance to said core wires thereby defining a plurality
of consecutive heating zones of said resistance formed at the joint
portions of said resistance and said core wires along said feeder
line and corresponding to said zone width;
a C-shaped fixing piece having the same width as said exposed portions
of said feeder line and having a plurality of claws on its inner
surface to project therefrom to narrowingly press said connector
against said feeder line and electrically connect thereto at the
position of each said exposed portion;
an insulator circumferentially covering said fixing pieces, said
connectors, said resistance and said feeder line altogether; and
an outer cover comprising a stainless steel sheath wound around
said insulator to enclose the outermost layer to form a single cable;
whereby said resistance of the braid structure is heated at every
said heating zone due to a Joule effect by the flow of current through
said feeder line of said cable.
17. A heat generating cable according to claim 16, wherein said
feeder line comprises two wires and is connected to a single-phase
alternating current source.
18. A heat generating cable according to claim 16, wherein said
feeder line comprises three wires and is connected to a three-phase
alternating current source.
Description BACKGROUND OF THE INVENTION
The present invention relates to an electric heater used to an
electric heating cable and a heating tube.
Nowadays, transporting high-viscosity oil and the like through
pipes, the viscosity of the moving oil has been reduced by electrical-heating
of the pipe line in order to improve an efficiency of transportation
of oil. According to the prior art, such electrical heating system
is constructed, for example, by an electric heating cable consisting
of a feeder line and an electric heater, respectively are covered
by a inorganic insulating cover material, and a heat retaining material
made of calcium silicate and the like, the electric heating cable
is laid in straight or revolutionally along a longitudinal direction
of an oil pipeline, consequently heat loss through the pipe is prevented.
According to other example of the prior art, a small-dia pipe is
welded on the oil pipeline and an electric heating cable is placed
within the small-dia pipe using a skin current heating effect in
the pipe. It is called a SECT (Skin Effect Current Tracing) Method.
Also, such electric heating cables are used to prevent roads, pedestrian
sidewalks, and pedestrian crossing bridges in cold regions from
freezing and being deposited of snow, or heat buildings. In case
that the electric heating cables are installed in roads and sidewalks,
the cables are buried in a shape of snake under the ground of 50-100
mm in depth and cement or asphalt concrete is cast direction the
snaked cable.
Other than the electric heating cable above, heating tubes have
been used in order to sustain heat of the fluid flowing through
the tube and control the temperature of the fluid, which heating
tubes are made by integrally constructing or assembling a tube,
a feeder line, and the electric heater. The heating tube is usually
made of a thermal resisting tube of metal or non-metal a fluid flows
therethrough, a feeder line extending along the thermal resisting
tube, and an electric heater wound around the assembly of the tube
and the feeder line in revolution or spirally in order to dielectrically
cover the tube. Such heating tube has been employed to, for example,
a medical dialyser so as to sustain heat or temperature of the dialysis
liquid flowing in the tube at a human temperature. The electric
heater used in the electric heating cable and the heating tube generates
electrically heat due to Joule effect to heat the target material.
Next, disadvantageous features of the conventional electric heater
will be described with reference to FIG. 1 and FIG. 2(A), 2(B),
respectively showing the construction of the electric heating cable
and a heating tube formed according to the prior art.
As shown in FIG. 1 depicting an electric heating cable, it is constructed
by a feeder line 1, two core wires 2 of the feeder line 1, insulating
covers 3, 4 and 9 made of insulation material, a resistance wire
5 wound around the insulating cover 4 spirally, and a shield 10.
The resistance wire 5 is an electric heating means. Ordinarily,
a diameter of the resistance wire 5 is AWG (American Wire Gauge)
about 36-42. The two core wires 2 are developed through an exposed
portion 7 formed in the insulation cover 4. The core wires 2 and
the resistance wire 5 are connected each other at a connection point
8.
Such electric heating cables are attached to, for example, pipes
of installations in cold regions. In operation of such electric
heating cables, when an alternative voltage is impressed to the
core wires 2, respective resistance wire 5 connected in a zone section
between two the exposed portion 7 adjacent generates heat. Owing
to the heat of respective heat resistance wires 5, the piping for
installations are heated every zone section, so as to prevent a
fluid flowing through the piping for installations from freezing.
Another conventional heating tube disclosed in Japan Patent Application
Laid-open No. Sho 56-85352 is shown in FIGS. (A) and (B).
The conventional heating tube consists of an inner layer of tube
1, a heat generating layer 2, an outer layer of tube 3, an electric
heating resin film 22, two tape-like metal foil conductors 23, and
a fluoroethylene plastics tape-like protective resin film 24. The
metal foil conductors 23 is covered on the electric heating resin
film 22 and they are wrapped by the protective resin film 24 in
a shape of sandwich in order to form a surface heating member 21.
The surface heating member 21 is wound around the tube 1 and the
heat generating layer 2 is constructed. The assembly of them is
covered by a tube outer layer 3.
In general, the electric heating resin film 22 above is constructed
by a conductive polymer and the like having a positive thermal coefficiency.
When a voltage is impressed between the metal foil conductors 23,
the higher the temperature rises, the higher the resistance becomes.
With an improvement of the electric resistance, a current decreases
and accordingly the temperature of the heat generating layer 2 decreases.
As a result, the electric heater of this kind belongs to a type
of self-control.
Such heating tube has been used to, for example, a medical installment
as a medical tube, When AC is impressed to two tape-like metal foil
conductor 23, the electric heating resin film 22 is heated. Heat
generated by the film 22 warms the tube 1 to heat medical liquid
such as dialysis liquid, and medical gas flowing through the tube
1, sustaining them at a fixed temperature.
The conventional electric heating cable shown in FIG. 1 and described
above uses a resistance wire 5 wound around the insulation shield
of the feeder line 1 in spiral as an electric heating means. The
resistance wire 5 mutually is connected to the core 2 at a junction
point 8. When a current is fed to the resistance wire 5, a joule
effect happens generating heat. When and AC is impressed to the
resistance wire generating heat in a certain temperature cycle and
the cycle changes or an outside force such as a bending is applied
to the resistance wire 5, the wire is apt to be broken failing to
generate disadvantageously heat in a corresponding zone section.
Also, a heat generation load of a resistance wire 5 when a current
flows through the wire rising its temperature is large, the wire
is not suitable to sustain the wire and a load to heat at a temperature
zone of middle to high (more than 50.degree. C.). In addition, because
the single resistance wire 5 is joined to cores 2 at the junction
point 8, it is afraid that a bad contaction happens at the point
8.
The conventional heating tube shown in FIGS. (A) and (B) are constructed
to generate heat in the automatic control-type electric heating
resin film 22 by impressing an AC to two insulated tape-type metal
foil conductor 23. Consequently, a stable heat generation is limited
in a low temperature zone and it is disadvantageously difficult
to obtain a stable generation of heat at a temperature of more than
50.degree. C.
SUMMARY OF THE INVENTION
It is the primary object of the present invention to prevent the
occurrence of any non-heating zone due to a break in a heating resistance
in a zone-type heat generating cable including a plurality of continuous
heating zones along a feeder line.
Particularly, it is a first object of the present invention to
provide a zone-type heat generating cable so designed that a heating
resistance is composed of innumerable parallel circuits within the
respective heating zones cyclically connected in parallel with a
power source and joints of the heating zones arranged at an interval
on a feeder line are electrically connected positively to core wires
of the feeder line.
In accordance with the present invention, braided naked strands
50 of the braid resistance 5 are electrically connected to one another
to form innumerable fine net-like parallel circuits within the heating
zones L. Therefore, even if some of the strands 50 are broken, the
other strands 50 maintain the electric connection. Therefore, even
if any partial break is caused in the heating resistance 5 due to
the occurrence of thermal expansion or contraction in the course
of the installation work or use of the heat generating cable C,
there is no difficulty to the generation of heat and there is no
occurrence of any heating zone L failing to generate heat on the
heat generating cable C.
On the other hand, a joint 6 having conductivity and a beltlike
braided construction is wound around a joint portion 8 of each heating
zone L from above, the resistance 5 of the braided construction
covering exposed portions 7 of the feeder line 1 and thus the resistance
5 is brought into contact and connected to exposed core wires 2
of the feeder line 1. The braided strands of both the resistance
5 and the joints 6 are placed one upon another at the respective
joint portions 8 so that the resistance 5 is pressed against the
core wires 2 to contact therewith at multiple points. As a result,
the electric connection between the resistance 5 and the feeder
line 1 is ensured thus preventing the occurrence of any contact
failure.
In particular, by using C-shaped fixing members 11 made to have
the same width as the exposed portions 7 at the joint portions 8
so as to further narrowingly press the resistance 5 from above the
joints 6 wound around the resistance 5, there is the effect of not
only making the connection between the resistance 5 and the feeder
line 1 more positive but also rendering the connection construction
compact. Thus, there is the effect of eliminating the occurrence
of connection failure at the joint portions 8, preventing the occurrence
of any non-heating zone L due to such connection failure by virtue
of the cooperative operation with the construction of the resistance
5 of the braided construction and preventing the occurrence of such
non-heating zone L even by virtue of the joints.
It is another purpose of the present invention to provide an electric
heater, without the disadvantageous problems of the prior art, having
several advantages of no-wire-breaking owing to temperature cycle
changes and any external pressure.
According to another purpose of the present invention, is provided
an electric heating cable and heating tubes using the electric heater
of the present invention in order to construct a composite tube
enabling to use in a high temperature zone of to about 200.degree.
C. and having few happenings of trouble.
The electric heater of the present invention has a braided structure
consisting of a single or plural strands.
The electric heaters constructed above are electrically connected
to expose portions formed periodically on the cores of the feeder
line at a regular interval.
According to the present invention, the braided structured electric
heater is arranged around a tube and a heating tube is obtained.
The electric heating cable using the electric heater of the present
invention is arranged along the tube through which a fluid flows.
When a switch is turned ON, and AC voltage is impressed between
two cores of the feeder line. Then, the current flows-through the
electric heater of the braided structure electrically connected
to the cores through multi-position of the exposed portions provided
with joints generating a Joule heat. The Joule heat generated in
the electric heater of the present invention heats the piping to
sustain the temperature of the fluid flowing through the piping.
In case that the heating tube is connected to the route through
which a fluid flows, when the switch is turned ON, a voltage is
impressed to the feeder line. Accordingly, a current is fed to the
electric heater of the braided structure electrically connected
to the cores through multiposition of the exposed portions provided
with joints generating a Joule heat. The Joule heat heats the tube
and it is transmitted to the fluid flowing through therein sustaining
it at a fixed temperature.
BRIEF DESCRIPTION OF THE DRAWING
FIGS. 1 and 2 (A), (B) are construction explanations of the conventional
electric heating cable and a heating tube;
FIGS. 3 and 4 (A), (B) are construction explanations of an embodiment
of the present invention;
FIG. 5 is an construction explanation of the electric heating cable
of the first embodiment or application of the present invention;
FIG. 6 is an exploded perspective view of a part of the arrangement
shown in FIG. 5,
FIG. 7 (A), (B), (C) are explanations of a fixing piece for connecting
the electric heater to the feeder line;
FIG. 8 shows primitively an electricity layout of the electric
heating cable;
FIG. 9 is an explanation of the electric heating cable of the first
embodiment which is use according to the present invention;
FIG. 10 is a construction explanation of the second embodiment
in use according to the present invention:
FIG. 11 is a section explanation of a part of the arrangement shown
in FIG. 10,
FIG. 12 is a longitudinal section explanation of the heating tube
shown in FIG. 10;
FIG. 13 (A), (B), (C), are exploded explanations of the connection
of the joint;
FIG. 14 is a primitive electric layout of the heating tube shown
in FIG. 10;
FIG. 15 is a construction explanation of another heating tube to
which the present invention is applied; and
FIG. 16 is a section explanation of a part of the arrangement depicted
in FIG. 15;
FIG. 17 is a diagrammatic view of another embodiment of the present
invention in which the feeder line is connected to a three-phase
AC source; and
FIG. 18 is an electric connection diagram of FIG. 17.
PREFERRED EMBODIMENT
As shown in FIGS. 3 and 4, the electric heater 5 consists of a
plurality of strands 50. The strands 50 are naked resistance wires
of diameters of about 0.08-0.1 mm. These strands 50 are arranged
in a manner of mutual-in-and-out and form a braid. FIGS. 3 (A) and
3 (B) show one being braided of a single strand or a plurality of
strands 50 in a shape of band. FIGS. 4 (A) and 4 (B), respectively
show another one being braided of a single strand or a plurality
of strands 50 around a core member 51. Such constructed electric
heater 5 is used in various apparatuses as shown in FIGS. 5 to 16.
FIG. 5 is a construction explanation of the electric heater according
to the first embodiment of the present invention. FIG. 6 is an exploded
perspective view depicting a part of the heater shown in FIG. 5.
FIGS. 7 (A), (B), and (C), respectively show explanation of fastner
pieces for joining the electric heater to the feeder line and show
the case in which the electric heater of the present invention is
applied to the electric heating cable for low and middle temperature
(0.degree.-50.degree. C., 50.degree.-120.degree. C.). In FIGS. 5-7,
the parts having the corresponding function to these of FIGS. 1
and 2 have the identical reference numerals and some parts will
be explained again in detail a little.
FIG. 5 shows the feeder line 1, two core wires 2 of the feeder
line 1, an insulator 3 covering around the feeder line 1, and another
insulator 4 for assembling both the insulators 3. The core wires
2 are concentrated strands of, for example, copper or plated of
nickel plating or of copper plated with a silver of high conductivity.
The insulators 3 and 4 are fluoroethylene plastics of high thermal-resistive.
The electric heater 5 constructed according to the present invention
has a braided construction braided of the naked strands 50 of the
resistance wires. A joint 6 is a thin wire such as copper-made one
of high conductivity and constructed in a brand-shape of braided
construction. Similar to one shown in FIG. 6, the exposed portion
7 is formed in these two cores 2 and the joint portion 8 is formed
thereon to connect the core 2 to the electric heater 5. It is noted
that the exposed portion 7 are alternately formed at a regular interval
L in two cores 2 and a joint 6 of the braided construction is wound
on the developed portion 7. The joint 6 connects the electric heater
5 to the cores 2 at respective joint portions 8 by pressing the
electric heater 5 of a braid construction to cores 2 coming in contact
through an number of points or lines. The heat insulator 9 covers
the joint 6 and other elements and the outer shield 10 protects
the insulator 9. An electric cable C of the present invention apparently
consists of the feeder line 1, the electric heater 5, and joints
6 and the other.
For example, one manufacturing method of the electric heating cable
C above will be explained. First, the core wire 2 consisting of
strands of a plurality of fine conductors such as silver plated
copper wires is wound around the insulator 3 making a covered conductor.
Two conductors are assembled side by side and they are covered by
the insulator 4, so that the feeder line 1 provided with two core
wires 2 and of a ribbon-like is molded with a plastic. Next, outer
portions of the insulator 4 around the feeder line 1 are cut at
a regular interval L in a shape of semi-ring alternately. Consequently,
the core wires 2 are half developed with a fixed width informing
exposed portion.
After the formation of the exposed portion 7, the strands 50 of
resistance wires are braided around the feeder line 1. Then, the
braid is forcibly wrapped by the braided electric heater 5. In order
to make a contact between the electric heater 5 and two cores 2
sure, the width of the joint 6 of a braided structure to be wound
on the exposed portion 7 is determined so as to be narrow a little
than the width of the exposed portion 7. A fixing member 11 of a
C shape as shown in FIGS. 7(A)-7(C) is applied on the braid of the
joint 6 and an open portion of the fixing member 11 is pressed from
both sides of the member, so that claws 12 provided on an inner
face of the fixing member invade into a gap between strands of the
core wires 2. As a result, the core wires 2 are fixed in a shape.
A plurality of strands 50 consisting of the electric heater 5 are
pressed in points or lines and the electric heater 5 comes into
contact with the cores 2 through a number of positions joining them
electrically a principle of connection between the electric heater
5 and the cores 2 is shown in FIG. 8. As apparent from FIG. 8, a
plurality of strands 50 constituting the electric heater 5, respectively
come into contact with the cores 2 through multi-point and they
are electrically connected firmly. After that, the insulator 9 is
extruded and plastic-molded so as to cover these cores 2. If necessary,
a shield 10 such as a braided fiber or a stainless sheath is applied
thereon to protect them.
The electric heating cable C manufactured according to the present
invention is used in an installation of, for example, an oil plant
as shown in FIG. 9.
As shown in FIG. 9, a main pipe 30 through which a fluid flows
has a branch pipe 31, a heat insulator 32 provided on a part of
the main pipe 30, and a manual control valve 33, and also a power
box 34 and a band 35 for fastening the power box 34. The electric
heating cable C according to the present invention is adapted to
be arranged along the main pipe 30 as shown. The cable C has a branch
portion separated from a suitable branch point c and extends into
the branch pipe 31. In particular, the electric heating cable C
is turned twice or triple on the manual control valve 33 to strengthen
a heating effect thereon. When an AC voltage is impressed from the
power box 34 to the electric heating cable C, the strands 50 of
respective braids of the electric heater 5 is heated by a Joule
effect. Consequently, the fluid flowing through the interior of
the main pipe 30 and the branch pipe 31 or the manual control valve
33 is heated by the hot electric heater 5 and the temperature of
the fluid is detected by a temperature detector (not shown) in order
to adjust the fluid flowing through the main pipe 30 and the branch
pipe 31 at a fixed temperature.
FIG. 10 is a construction explanation of the heating tube according
to the second embodiment of the present invention, FIG. 11 is a
section showing a part of FIG. 10, FIG. 12 is a longitudinal explanation
of the heating tube shown in FIG. 10, FIG. 13 (A) (B), and (C) are
exploded explanation of connection of a joint, and FIG. 14 a primitive
layout of electricity of the heating tube shown in FIG. 10. FIG.
10 shows a heating tube T having a central tube t making a fluid
flown therethrough.
In FIGS. 10 and 11, the central tube t is a metal tube treated
by a fluoric resin or an insulation. The heating tube T has a feeder
line 1, two cores 2 for the feeder line 1, an insulator 3 covering
both the cores 2, and another insulator 4 filling the gap or space
generated by existence of the feeder line 1 and making the whole
section of the tube T circular. Also, the heating tube T has the
electric heater 5 of a braid arranged around the tube t, a joint
6, and the exposed portion 7 of the two cores 2. The cores 2 and
the electric heater 5 are joined through the exposed portion 7 (see
FIGS. 10-13).
The exposed portion 7 is formed mutually in the two core wires
2 wound around the tube t in a large spiral at a fixed interval
L and the joint 6 is fixed to the exposed portion 7. A shield or
cover 10 is applied on the insulator 4 and the cover 10 is secured
in place by the fixing piece 11. The material used to make the cores
2, the insulators 3 and 4, the electric heater 5 is the same as
the corresponding parts of the first embodiment of the present invention.
Therefore, as shown in FIG. 10, the tube t, the feeder line 1, and
the electric heater 5 and the other parts construct the heating
tube T.
The heating tube T above is manufactured by, for example, the following
steps.
First, the insulator 3 is laid around the core wires 2 making a
covered conductor 1. The two covered conductors 1 are arranged side-by-side
and a two-core wire feeder line 1 is obtained. Portions of the insulator
3 at a regular interval L are mutually cut out. A circumferential
part of the insulator 3 is cut to develop a part of the core wires
2 forming the exposed portion 7 having a predetermined width.
While, a braid of the resistance line is arranged around the tube
t and the electric heater 5 pushes the braid from the surroundings
of the heater 5. The feeder line 1 is wound in a large spiral around
the tube t covered by the electric heater 5. In order to come the
electric heater 5 into contact mutually with two core wires 2, a
joint 6 made in a ring of the braided structure of the substantial
same width as that of the exposed portion is applied to the exposed
portion 7 as shown in FIG. 13. Similar to the case shown in FIG.
7, a C shape fixing piece 11 is covered on the exposed portion 7
and an open portion of the fixing piece 11 is pushed from both the
sides of the C shape fixing piece 11, thereby the claws 12 formed
on the inner face of the fixing piece 11 invade fixedly into the
gap between strands of the cores 2. As a result, midportion of the
ring-like joint 6 is squeezed as shown in FIG. 13 (B) and a plurality
of strands 50 constructing the electric heater 5 are pushed and
come into contact forcibly the cores 2. In detail, due to such pressing,
the electric heater 5 comes into contact electrically and mutually
with the cores 2 through multi-point. The primitive connection of
the electric heater 5 and the cores 2 is shown in FIG. 14. In this
case, a plurality of strands 50 as shown constructing the electric
heater 5 come into contact with the core wires 2 through multi-point
forming a complicated parallel circuit. Then, the gap left by two
feeder lines 1 wound in a large spiral around the tube t is filled
by the insulator 4. The deformed section of the assembly is made
neat in a circle. After the section controlling step, the cover
10 covers the insulator 4 and the joint 6 and other parts so as
to obtain the heating tube T.
It is noted that it is possible to construct a composite tube of
the single heating tube t by proving further an insulator 9 on the
cover 10 and a protective shield 10 on the insulator 9 as shown
in FIG. 11 by two-dash chained line.
FIG. 15 is a construction explanation of a usage of another heating
tube according to the present invention. The heating tube shown
in FIG. 15 is differed from that shown in FIG. 10 only in the structures
of the feeder line 1 and the electric heater 5. As shown, the feeder
line 1 and the electric heater 5 use a plurality of strands 50 to
form a flat braid. It is possible to omit the core 51 from the braided
band-like electric heater 5 similar to the cases shown in FIG. 3
(A), (B) and FIG. 4 (A), (B). As shown in FIG. 15, according to
the embodiment of the present invention, two flat core wires 2 having
the exposed portion 7 of the feeder line 1 are wound in a large
spiral at a distance of about 180 degree as shown or in a side-by-side
relation around the outer periphery of the tube t. The electric
heater 5 of a flat braid is laid thereon spirally. Then similar
to the embodiment of FIG. 10, the insulators 3 and 4 are plastic-molded
and the cover 10 is provided thereon. According to the construction
of the embodiment shown in FIG. 15, the feeder line 1 and the electric
heater 5 are both formed in flat, so that it is possible to obtain
the compact heating tube T.
Such heating tube T is used as a conduit of electric heating sustaining
fluid and of gas analyzer, and as a medical tube which is arranged
on the medical installation and the like. When a voltage is impressed
to two core wires 2 of the heating tube T installed, a current is
flown to the electric heater 5 through the joint 6 generating a
Joule heat. The Joule heat generated in the electric heater 5 is
transferred to the tube t, thus a liquid or gas in the tube t is
heated or sustained at a fixed temperature.
Meanwhile, according to the embodiments above, the electric heater
5 consists of a plurality of strands (5) of resistance wires made
of nickel chrome, however, it is possible to employ other strands
made of a carbon fiber, or twisted strand of carbon fiber, a ceramic
and a plastic fiber, or a strand of ordinal metal resistance wire
and a carbon fiber. Also it is constructed the electric heater 5
of three cores so as to impress a three-phase AC similar to the
case of an AC voltage using two core wires.
Although a case of the electric heater 5 consisting of a plurality
of resistance wires was exemplified and explained, it is possible
to use a braid of a single wire, of a carbon fiber, or a carbon
fiber and ceramic material and plastics, or of a normal metal resistance
wire and a carbon fiber. In addition, concerning the cover of the
insulators 3, 4 and the tube t, it is possible to construct the
electric heater 5 by a silicagel fiber, a ceramic fiber or a polyamide
film. An electric heater suitable to a high temperature can be provided
by constructing insulators of these ceramic fibers in a shape of
sheath. Although a case of two core wires being used and a voltage
being impressed thereon has been explained, it is possible to use
three core wires, a three-phase AC being impressed thereto.
In short, the electric heater of the present invention connected
to the feeder line so as to generate a Joule heat is constructed
by a braid of a plurality of strands of resistance wires, respectively
connected to the feeder line through a number of points.
Consequently, according to the present invention, it is possible
to obtain an electric heater having a wide usage range of temperature
without trouble in operation.
In addition, when the electric heater of the present invention
is used on the electric heating cable, it is hardly to be failed
to generate heat in a certain zone section of the cable or to happen
an incomplete contact even a part of the strands are broken since
the temperature cycle changes during a heat generation or external
force such as a bending is applied. The reason for a sure-generation
of heat and a complete contact is that the electric heater is connected
to the respective feeder lines through a number of points. Because
the heat generation load of the electric heater due to a temperature
rise happened when a current is impressed to the electric heater
is distributed, the electric heater of the present invention can
be used suitably to sustain a temperature at not only in the range
of middle level (50.degree.-120.degree. C.) but also in the range
of high level (over 120.degree. C.). In this case, when any thermal
insulators of a sheath type such as an inconel-made insulator of
ceramic fibers and polyamid fibers, it is possible to provide a
heating tube durable to high temperature.
In particular, because a joint for joining forcibly the electric
heater to the feeder line is provided according to the present invention,
it is hardly that an incomplete contact happens in the electric
heater.
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