Heating mantle and method for fabricating the same

In order to provide a heating mantle so composed that fixing and unfixing work can be carried out simply and easily and in addition a good thermal uniformity can be obtained, the heating mantle is fabricated by a method, by which sewing by means of a sewing machine is carried out on a sheet-shaped heat resistant and heat insulating core member, using a heating wire, which is a yarn of metal fine wires, for a lower yarn and a glass yarn for an upper yarn; a predetermined heating wire pattern is formed on a surface of the core member; and a layered body consisting of the core member with the heating wire and covering members made of glass cloth, which are laid on upperside and underside thereof, is enclosed by a sack-shaped cover member. By the heating mantle thus constructed winding around a piping is simple and easy and there is no risk that deviation of the heating wire takes place so that a good thermal uniformity with respect to the piping can be exhibited. Moreover, owing to the fact that the heating wire is used for the lower yarn for the sewing machine, it is possible to form easily the predetermined heating wire pattern.

FIELD OF THE INVENTION 
The present invention relates to a heating mantle, and a method for 
fabricating the same and in particular to an improvement of a heating 
mantle suitable for keeping piping, joints, valves, etc. e.g. for 
precision machines and apparatuses, etc. (hereinbelow called piping, etc.) 
warm or heating them, and a method for fabricating the same. 
DESCRIPTION OF THE PRIOR ART 
Heretofore, for heating piping for precision machines and apparatuses, 
etc., there is known a composition, in which a covering heating wire such 
as a nichrome wire is wound in the form of a spiral around the piping on 
the outer surface thereof and a band-shaped heat insulating material made 
of inorganic fiber is wound further thereon for preventing heat 
transmission. 
Although the above mentioned heaters has a simple composition, a 
considerable work is necessary for winding a heating wire. In addition, in 
case where there exist joints, valves, branched pipes, etc., a manner of 
winding the heating wire and a manner of making electric current flow 
therethrough are complicated so that workability is very bad. Further, 
unless the heating wire is wound with a constant pitch, there is a 
drawback that thermal uniformity with respect to the piping is damaged. 
Furthermore, when it is unfixed at maintenance, inspection, etc. of the 
piping, the heating wire should be rewound again. 
SUMMARY OF THE INVENTION 
The present invention has been made in view of the above problems and an 
object thereof is to provide a heating mantle, so composed that fixing and 
unfixing work to piping, etc. can be carried out easily and a good thermal 
uniformity with respect to the piping, etc. can be obtained, and a method 
for fabricating the same. 
A heating mantle according to the present invention is characterized in 
that it comprises a sheet-shaped core member having a flexibility and a 
resistance to heat; a heating wire fixed with a predetermined pattern on a 
surface of the core member; a sheet-shaped covering member having a 
flexibility and a resistance to heat or a sheet-shaped heat insulating 
member having a flexibility and a resistance to heat, which is laid on the 
core member on the side of the heating wire; and a sack-shaped cover 
member having a flexibility and a resistance to heat enclosing a layered 
body of the core member with the heating wire and the covering member or 
the heat insulating member. 
Further a method for fabricating a heating mantle according to the present 
invention is characterized in that a heating wire is fixed on a surface of 
a sheet-shaped core member having a flexibility and a resistance to heat 
by means of a sewing machine, disposed with a predetermined pattern; a 
sheet-shaped covering member having a flexibility and a resistance to heat 
or a sheet-shaped heat insulating member having a flexibility and a 
resistance to heat is laid on the core member on the side of the heating 
wire pattern, and these members are enclosed by a cover member having a 
flexibility and a resistance to heat in a form of a sack. 
For the core member, the covering member or the heat insulating member and 
the cover member constituting a principal part of the heating mantle 
according to the present invention, it is preferable to use sheet-shaped 
cloths or mats made of inorganic fiber such as glass fiber, ceramic fiber, 
etc. However, any other material can be suitably selected to be used, if 
it has a flexibility, a resistance to heat and an electric insulation. 
Concerning the cover member, it is desirable to attach bands with clasps 
thereto for fixing and maintaining a heating mantle so that it does not 
get off the piping after having been wound thereon. 
The heating wire sewn on the core member by means of a sewing machine may 
be single, but since a thick single wire is rigid, it is difficult to deal 
with it by means of the sewing machine. Instead of the single wire, metal 
fine wires can be used. A wire obtained by twisting a required number of 
metal fine wires having a diameter of several micrometers has a 
flexibility and moreover a satisfactory strength, and therefore it is 
suitable for fixing it by means of a sewing machine. For yarn used for 
surfaces where no heat generation is required it is preferable to use yarn 
having an electric insulation e.g. such as glass yarn. 
As a method for forming a heating wire pattern on the core member by means 
of a sewing machine, there is known a method wherein a heating wire, which 
is e.g. twisted metal fine wires, is used for a lower yarn for the sewing 
machine, while a glass yarn is used for an upper yarn, and the core member 
is put on a table of the sewing machine and moved forward and backward and 
to the left and the right similarly to usual sewing by means of a sewing 
machine to form a predetermined pattern of the heating wire. 
There is another method, wherein a drawing of a heating wire pattern 
prepared in advance on the basis of a design is laid on the core member 
and the heating wire is sewn while tracing the pattern drawn on the 
drawing, the drawing being removed thereafter. 
By the former method, since the heating wire pattern is formed while sewing 
by means of the machine, a fair skill is required. On the other hand, by 
the latter method, since it is sufficient to trace the heating wire 
pattern drawn on the drawing, it is easy to sew-on the heating wire and 
therefore workability is good. 
Further there is an automatic sewing system using computer control. By this 
system, at first, a predetermined heating wire pattern is designed by 
using a CAD; instructions from the CAD are stored in a memory of a 
programming device; the programming device is connected with an industrial 
computer-aided sewing machine through a cable; and the heating wire is 
sewn on the core member according to the wiring pattern, while moving a 
movable table on the machine side supporting the core member according to 
instructions from the computer. By this method it is possible to realize 
full automation from preparation of the drawing of desired heating wire 
pattern to work of sewing the heating wire on the core member.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 1 to 4 show a preferred embodiment of the present invention. 
In the figures, a heating mantle A is so composed that a predetermined 
heating wire pattern is sewn by means of a sewing machine on a surface of 
a core member 1 having a flexibility made of a heat insulating resin 
porous body, an inorganic fiber blanket, a heat resistant rubber sheet, 
etc. by using a heating wire 2 consisting of a yarn of metal fine wires 
for a lower yarn and a heat resistant yarn 3 made of glass fiber, etc. for 
an upper yarn to form a predetermined pattern; heat resistant and 
electrically insulating sheet-shaped covering members 4 and 5 made of 
glass cloth, etc. are laid on upperside and underside of the core member 1 
with the heating wire; layered body thus obtained is enclosed by a heat 
resistant electrically insulating sheet-shaped cover member 6 made of 
glass cloth, etc.; and a terminal or a connector 8 is fixed on leads 7 
taken out for connecting them with a power supply through a part of the 
cover member 6. 
In FIGS. 1 to 4, A is a heating mantle and 1 is a sheet-shaped core member 
made of silicone sponge. A predetermined heating wire pattern is sewn on 
this core member 1 by means of a sewing machine using a heating wire 2 
formed by twisting nichrome fine wires for a lower yarn and a glass yarn 3 
for an upper yarn. 4 and 5 are sheet-shaped covering members made of glass 
cloth laid on upperside and underside, respectively, of the core member 1 
with the heating wire. The covering member 4 on the side of the heating 
wire facing the piping is used mainly for the purpose of improving 
electric insulation and thermal uniformity, while the covering member 5 on 
the opposite side is used mainly as a heat insulating member for 
preventing heat transmission. The layered body consisting of the core 
member 1 with the heating wire and the covering members 4 and 5 is 
enclosed by a sheet-shaped cover member 6 made of glass cloth. For this 
cover member 6 made of glass cloth it is preferable to use glass cloth 
coated with fluorocarbon resin for the purpose of making it dust-proof. 
The two ends of the heating wire 2 sewn on the core member 1 with a 
predetermined pattern are taken out outside through leads 7 passing 
through predetermined places of the cover member 6 and a connector 8 for 
connecting them with a power supply is attached thereto. 
A plurality of belts 10 made of heat resistant cloth having clasps 9 are 
sewn on an end portion of the cover member 6 and belt guides 11 made of a 
similar material are sewn on predetermined places on the surface. 
FIG. 4 shows a state where the heating mantle A thus composed is wound 
around a straight pipe B and fastened thereon by means of the belts 10 
with the clasps 9. Instead of the clasps 9, easily fixable and unfixable 
fasteners called usually "magic tapes" can be used therefor. 
Work for fixing the heating mantle thus composed to a piping and work for 
unfixing it at maintenance or inspection can be carried out simply and 
easily. Further, since there is no risk of deviation of the heating wire, 
a good thermal uniformity with respect to the piping can be exhibited. 
In addition, it is possible to fabricate easily heating mantles having any 
shapes not only for straight pipes but also for elbows, branches, and 
pipings having various shapes. 
In particular, since the heating mantle is so composed that a heating wire 
is sewn on a core member with a predetermined pattern by means of a sewing 
machine, using the heating wire as a lower yarn for the sewing machine, it 
is possible to obtain a core member with a heating wire without trouble. 
Moreover it is possible also to adopt an automatic sewing system using 
computer control and to lower fabrication cost of the heating mantle. 
A concrete fabrication process of the heating mantle indicated in FIGS. 1 
to 4 will be described below. 
At first, a developed view of a piping, to which the heating mantle should 
be fixed, is prepared by means of a CAD. A required resistance of the 
heating wire is obtained by using a cross-sectional area of the piping and 
a length of the heating wire described later is calculated. Then, a pitch 
of the heating wire and a wiring pattern thereof are additionally drawn on 
the developed view obtained by means of the CAD to prepare a drawing of 
the heating wire pattern. 
A silicone sponge 5 mm thick is used for the core member. The drawing of 
the heating wire pattern is laid on a surface of the core member after 
having cut it in a predetermined form and fixed provisionally thereto by 
means of a thread, etc. so as not to move. 
An industrial sewing machine is used for the machine, in which a glass yarn 
coated with fluorocarbon resin is used for the upper yarn, while a heating 
wire obtained by twisting 3 metal fine wires having a diameter of 0.05 
.mu.m and further by twisting 7 yarns of metal fine wires thus obtained is 
used for the lower yarn. 
Sewing by means of the machine is carried out while tracing the heating 
wire pattern in the drawing laid on the surface of the core member. The 
core member with the heating wire is obtained by removing the drawing 
after having terminated the sewing. 
Next covering members made of glass cloth are laid on upperside and 
underside of the core member with the heating wire and the whole is 
enclosed by a cover member made of glass cloth coated with fluorocarbon 
resin, which is sewn so as to be a sack. At this time, leads for the 
heating wire are taken out through holes formed in the cover member at 
predetermined positions. A connector for connecting them with a power 
supply is fixed thereon and belts with clasps and belt guides are sewn on 
the cover member at predetermined places to obtain the heating mantle for 
a straight pipe. 
FIGS. 5 and 6 show heating mantle according to other embodiments of the 
present invention. 
In the embodiment indicated in FIG. 5, heat resistant electrically 
insulating cloth such as glass cloth, etc. is used for the core member 1', 
on which the heating wire 2 is sewn with a predetermined pattern by means 
of a sewing machine similarly to the preceding embodiment. 3 is a glass 
yarn serving as the upper yarn and 4' is a sheet-shaped covering member 
made of silicone sponge, which is used as a heat insulating member for 
preventing heat transmission. 6 is a cover member. 
In the embodiment indicated in FIG. 6, A is a heating mantle; 12 is a core 
member made of glass cloth (0.26 mm thick); 13 is a heat insulating member 
made of glass fiber mat (4 to 10 mm thick); and 14 is a sack-shaped cover 
member made of glass cloth (0.11 mm thick). For this cover member glass 
cloth coated with fluorocarbon resin is used for the purpose of making it 
dust-proof. 
On a surface of the core member 12 a covered heating wire 15, in which a 
nickel-chrome wire is covered by a glass sleeve, is disposed in a zigzag 
pattern and sewn thereon with a glass yarn 16. A mat-shaped heat 
insulating member 13 is laid on the core member 12 with heating wire and 
these members are enclosed by a cover member 14. 
As described in detail in the above, according to the present invention, 
work for fixing a heating mantle to a piping and unfixing it therefrom is 
not troublesome and it can be fixed simply and easily and moreover a good 
thermal uniformity with respect to the piping can be exhibited. In 
addition, a heating mantle can be obtained, in which a heating wire can be 
formed in a predetermined heating wire pattern by means of a sewing 
machine.