Abstrict
A flexible electric heater comprises a heat resistant support (4)
of sheet or tape form having at least one electrical resistance
heating element (1) secured thereto. The at least one heating element
comprises a ribbon (2) of electrical resistance material provided
with a plurality of integral tabs (3). The tabs have been pressed
through the support to secure the heating element to the support.
The support (4) is flexible and comprises a woven fabric material,
such as woven glass fabric or woven ceramic fabric, or a non-fibrous
material, such as flexible mica.
Claims
What is claimed is:
1. A flexible electric heater made by a method of manufacturing,
which method comprises:
providing a heat resistant support selected from the class consisting
of sheet and tape forms of supports, the support being flexible
and being selected from the group consisting of a woven fabric and
a non-fibrous material;
providing at least one electrical resistance heating element comprising
a length of ribbon of electrical resistance material provided with
a multiplicity of integral tabs extending therefrom and distributed
along the length thereof;
urging the tabs of the ribbon through the support so as to cause
the tabs to emerge from a rear surface of the support; and
deforming the tabs at the rear surface of the support to secure
the heating element.
2. A heater according to claim 1, wherein the tabs are deformed
by means selected from bending, twisting and buckling.
3. A heater according to claim 1, wherein the tabs extend edgewise
from the ribbon.
4. A heater according to claim 3, wherein the tabs are arranged
such that the ribbon is secured edgewise to the support.
5. A heater according to claim 1, wherein the ribbon is of corrugated
form.
6. A heater according to claim 1, wherein the support is selected
from flexible non-fibrous mica, woven glass fabric and woven ceramic
fabric.
7. A method of manufacturing a flexible electric heater comprising:
providing a heat resistant support selected from the class consisting
of sheet and tape forms of supports, the support being flexible
and being selected from the group consisting of a woven fabric and
a non-fibrous material;
providing at least one electrical resistance heating element comprising
a length of ribbon of electrical resistance material provided with
a multiplicity of integral tabs extending therefrom and distributed
along the length thereof;
urging the tabs of the ribbon through the support so as to cause
the tabs to emerge from a rear surface of the support; and
deforming the tabs at the rear surface of the support to secure
the heating element to the support.
8. A method according to claim 7, wherein the tabs are deformed
by means selected from bending, twisting and buckling.
9. A method according to claim 7, wherein during urging of the
tabs of the ribbon through the support, a plate means is provided
adjacent the rear surface of the support, the emerging tabs being
deformed against the plate means.
10. A method according to claim 9, wherein the plate means is selected
from substantially firm and hard material.
11. A method according to claim 10, wherein the plate means is
selected from metal, plastics and rubber.
12. A method according to claim 7, wherein the tabs extend edgewise
from the ribbon.
13. A method according to claim 12, wherein the tabs are arranged
such that the ribbon is secured edgewise to the support.
14. A method according to claim 7, wherein the ribbon is of corrugated
form.
15. A method according to claim 7, wherein the support is selected
from flexible non-fibrous mica, woven glass fabric and woven ceramic
fabric.
Description This invention relates to a flexible electric heater and a method
of manufacturing such a heater.
DESCRIPTION OF PRIOR ART
GB-A-1 569 588 (E.G.O. Elektro-Gerate Blanc u. Fischer) describes
an electrical radiation heater for a glass ceramic plate in which
anchoring tabs formed at the lower edge of a heating conductor strip
pass entirely through an annular sheet and are bent over in a region
below a notch formed in each tab in order to hold the heating conductor
strip against the sheet. The annular sheet has the structure of
a relatively strong cardboard material made from a high temperature-resistant
insulating material. The material of the sheet is a fibrous insulating
material which is combined with a ceramic binder to form an insulating
board, such as that sold under the Registered trade Mark FIBERFRAX.
The tabs are sufficiently strong to pierce the board-like material
of the annular sheet and a rotary tool is then used to press down
the lugs formed beyond the notches against the underside of the
annular sheet.
The disadvantage of such a bound fibrous support is that it is
brittle and lacks flexibility. Therefore the support tends to break
if any attempt is made to flex the same.
OBJECT OF THE INVENTION
It is an object of the present invention to provide an electric
heater which is relatively flexible.
SUMMARY OF THE INVENTION
According to one aspect of the invention there is provided a flexible
electric heater comprising a heat resistant support of sheet or
tape form having at least one electrical resistance heating element
secured thereto, the at least one heating element comprising a ribbon
of electrical resistance material provided with a plurality of integral
tabs extending therefrom, the tabs having been pressed through the
support, wherein the support is flexible and comprises a woven fabric
material or a non-fibrous material.
The tabs of the ribbon may protrude from a rear surface of the
support and may be deformed at that rear surface, such as by being
bent, twisted or buckled.
According to another aspect of the invention there is provided
a method of manufacturing a flexible electric heater comprising:
providing a heat resistant support of sheet or tape form;
providing at least one electrical resistance heating element comprising
a ribbon of electrical resistance material provided with a plurality
of integral tabs extending therefrom; and
urging the tabs of the ribbon through the support to secure the
heating element to the support
wherein the support is flexible and comprises a woven fabric material
or a non-fibrous material.
The tabs may be urged through the support from a front surface
thereof such that they emerge from a rear surface of the support
and are deformed at the rear surface, such as by bending, twisting
or buckling.
During urging of the tabs of the ribbon through the support, plate
means may be provided in contact with the rear surface of the support,
the emerging tabs being deformed against the plate means.
The plate means may comprise a substantially firm or hard material,
such as metal, plastics or rubber.
The ribbon may be provided with the plurality of tabs extending
edgewise therefrom.
The tabs may be arranged such that the ribbon is secured edgewise
to the support.
The ribbon may be provided of corrugated form.
The support may be of any suitable flexible heat resistant sheet
or tape form material, of woven fabric material or non-fibrous material,
capable of having the tabs of the heating element pressed therethrough
and capable of withstanding the operating temperature conditions
of the heater.
The support may comprise flexible non-fibrous mica or may comprise
woven glass fabric or woven ceramic fabric.
The invention is now described by way of example with reference
to the accompanying drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an enlarged perspective view of a portion of corrugated
ribbon form electrical resistance heating element for use in a heater
according to the invention;
FIG. 2 is a plan view of a heater according to the invention incorporating
the heating element of FIG. 1; and
FIG. 3 is a side view of the heater of FIG. 2.
DESCRIPTION OF PREFERRED EMBODIMENT
A radiant electric heating element 1 for a flexible radiant heater
according to the invention comprises a corrugated ribbon 2 of bare
electrical resistance material, such as iron-chromium-aluminium
alloy, provided along its length with a plurality of tabs 3, the
tabs extending edgewise from the ribbon and integral and substantially
coplanar therewith. The tabs may be substantially rectangular or
triangular in shape with each side of the tabs being continuous,
that is without deformations such as notches.
A flexible support 4 for the heating element is provided of sheet
or tape form and comprises a suitably heat resistant material such
as flexible (non-fibrous) mica or woven glass fabric or woven ceramic
fabric. An example of woven ceramic fabric is Nextel (Registered
Trade Mark) 312, manufactured by 3M Co.
The corrugated heating element 1 is pre-formed into a meandered
shape and located with the corrugated ribbon edgewise on the flexible
support 4 and with the ends 5 of the tabs 3 in contact with a front
surface of the support. Using a simple press tool, pressure is applied
between the ribbon 2 and the support 4 to urge the tabs 3, end 5
first, through the support 4. The tabs 3 protrude from a rear surface
6 of the support and are bent over or twisted or caused to buckle,
as shown in FIG. 3 whereby the heating element is secured to the
support 4 with the corrugated ribbon 2 edgewise thereon. The press
tool includes a plate 10 of a substantially firm or hard material,
such as metal, plastics or rubber. During urging of the tabs 3 through
the support 4, the plate 10 is arranged to contact the rear surface
6 of the support and when the tabs 3 emerge from the rear surface
they are deformed against the plate, i.e. bent over, twisted or
buckled, thereby securing the heating element to the support.
For the sake of clarity, the portion of the heating element 1 shown
in FIG. 1 is a detail of a section represented by reference numeral
7 in FIG. 2.
The resulting heater may be flexed into any desired shape according
to its required application, with the ends 8, 9 of the heating element
arranged for electrical connection to an appropriate voltage source.
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