Note: Descriptions are shown in the official language in which they were submitted.
~o55094
The present invention relates to an electrically heatable
wall covering on the basis of a fabric of natural and/or synthetic
fibres, more particularly an electrically heatable carpet, in
which a wire-shaped electrical heating element is enclosed in the
carpet body.
In a well-known electrically heatable wall covering the
electrical heating element is formed by a finely coiled
resistance wire i.e. a wire of a material having a high specific
resisti~ity. Such a construction could not be used for a floor
carpet as the finely coiled resistance wire would by readily
damaged and even broken as a result of the loads applied to the
carpet, such as footsteps, impressions of (heavy) furniture
pieces etcetera.
It is also known to apply an electrically conducting paint
in a zig-zag pattern on a carrier of plastics material, such as
polyester and to connect such carrier to the proper wall covering,
for example wall "paper". auch a heating element in the form of
a zig-zag ribbon of electrically conducting paint (so-ca~led
carbon paint) could not be applied in a floor carpet either, as
the electrically conducting paint would soon break under the
influence of the mechanical luads exerted on the carpet in use.
For this reason this type of wall covering is used only as
electrically heated wall "paper" and as ceiling covering.
From a standpoint of heat distribution heating from the floor
covering would be advantageous, as in this manner a course of the
temperature - considered from the floor to the ceiling of the room
to be heated - could be realized which corresponds with the ideal
course of temperature, according to which the room temperature has
its maximum value adjacent the floor and decreases towards the
ceiling,
-- 2 --
1055~94
Therefore it is the object of the present invention to provide an
electrically heatable wall covering which is more particularly adapted to
be used as a floor carpet as the electrical heating element(s) is (are)
capable of withstanding the loads exerted on it in use, such as footsteps,
impressions by furniture pieces etcetera.
For this purpose in accordance with the present invention there
is provided an electrically heatable floor covering comprising a carpet
of woven electrically non-conducting fibers, wherein the improvement
comprises an electrical heating element woven in the carpet as a weft thread
in a zig-zag pattern covering the area of the carpet, said heating element
being made of a stranded wire having a resistivity per meter of about 0.36
ohm, and being composed of a plurality of copper filaments each of which
has a diameter of about 0.1 mm and is covered with a reinforcing coating
of polytetrafluoroethylene which causes the wire to withstand impressions
produced by footsteps and by heavy furniture without being broken, the total
wire length being about 15 m. per square m.
This means that according to the invention for the heat develop-
ment use is made of a material having a relatively low specific resistivity,
which is normally applied in connection with its heat conducting properties
rather than in connection with its heat developing properties.
The advantage of a thin wire of copper or comparable material is
to be seen in that such a wire, in combination with the outstanding
mechanical strength of the coating of polytetrafluoroethylene successfully
withstand all of the loads exerted on the carpet in use.
In order to further increase the flexibility of the electrical
heating element a stranded wire of copper or similar material is used. An
electrical heating element of this structure may be considered as absolutely
safe.
An electrical heating element as proposed by the present invention
~ -3-
A~
lOSS~94
may be woven into the carpet body in a simple way during the normal carpet
weaving process. For example the polytetrafluoroethylene-coated copper
wire may be inserted in the carpet body as a weft thread.
s ~ -3a-
10551D94
Further details of the invention will be hereinafter
further described with reference to the accompanying drawings
in which:
Fig. 1 is a diagrammatic plan view of a carpet according
to the present invention and
Fib, 2 is a cross-section through a carpet according to
the present invention, in which can be seen how the heating
element is interwoven in the carpet body.
In the example shown in Fig. 1, the carpet 1 consists of
two sections la and lb. In each of these two sections the wire-
shaped element 2 is formed into a zig-zag pattern which covers the
whole surface of the section. The electrical heating element 2
consists of a thin wire of copper, which is coated by an
electrically insulating high-temperature material, such as
polytetrafluoroethylene. The wire portions extending between
the bends or curves of the zig-zag pattern are straight rather
than being coiled as in the well-known electrically heated wall
coverings. The distance between two adjacent straight wire
portions is for example 6 cm, whereas the surface of a carpet
section is for example 4 m2 (2 x 2 m). This means that the
total length of heating wire is about 60 m per carpet section.
For the heating wire 2 it is advantageous to make use of a
type of electrical conductor, which is applied in space crafts.
More particularly the types R30 and E2~, manufactured by Essex
International Incorporation, are suitable for this purpose. The
types just referred to relate to stranded wires (each consisting
of seven elementary wires, each elementary wire having a diameter of
about O.lmm) of nickel or silver-coated copper, covered by an
extruded coating of polytetrafluoroethylene. The resistivity per
meter of a wire of type E30 is for example 0.36 ohm.
1055094
When using a power source of 220 V the heating power of
one section is about 2.2 KW, which means a heating power of about
550 Watts per m carpet.
The heating elements 2 in the two carpet sections la and
lb are connected in parallel to a control box 3, which may comprise
a temperature-regulating system and is provided with a plug 4
for connection to the power supply.
In the example sho~n in Fig. 2 the carpet consists of a
backing 5, on which piles 6a are formed in some well-known
manner, e.g. by pushing loops of a continuous thread 6 from the
underside of the backing 5 through the meshes of the same
upwardly.
As shown the heating wire 2 of the present invention can be
simply woven into the carpet body by introducing it between the
backing 5 and the loop portions 6b on the underside of the
backing 5.
Also in a well-known manner the piles 6a, the loop portions
6b and the heating wire 2 may be bonded or locked to the backing.
For example, a tacky liquid latex compound or hot polyethylene or
other thermoplastic cement may be applied to the underside of the
carpet structure shown in Fig. 2.
It will be understood that the invention is not limited to
the example shown. In general, the heating wire 2 may be
introduced for example as a selected weft thread in any well-
known carpet weaving process.
