Abstrict
In the manufacture of an electric heater, means (24, 26) is provided
for feeding and guiding an elongate corrugated metal ribbon heating
element (14) progressively into overlying edgewise relationship
with a base (2) of thermal and electrical insulation material. Means
(6, 8) is provided for supporting the base (2) and for effecting
relative motion between a surface of the base (2) and the means
(24, 26) for feeding and guiding the heating element (14), such
that motion of the base (2) is synchronised with feeding of the
element (14). Further means (28) is provided for applying localised
edgewise pressure to the heating element (14) as it is progressively
fed and guided into the overlying edgewise relationship with the
base (2), to urge the heating element (14) towards the base (2)
and cause an edge portion (22) of the heating element (14), or one
or more parts (22) secured to the heating element (14) and extending
edgewise therefrom, to become secured by embedding in the base (2).
Claims
1. A method of manufacturing an electric heater in which an elongate
corrugated metal ribbon heating element (14) is supported edgewise
on a base (2) of thermal and electrical insulation material, the
heating element (14) having one of an edge portion (22) thereof
and at least one part (22) secured thereto and extending edgewise
therefrom, secured by embedding in the base (2), the method comprising
the steps of providing means (24, 26) for feeding and guiding an
elongate corrugated metal ribbon heating element (14) progressively
into overlying edgewise relationship with a base (2) of thermal
and electrical insulation material; providing means (6, 8) for supporting
the base (2) and for effecting relative motion between a surface
of the base (2) and the means (24, 26) for feeding and guiding the
heating element (14), such that motion of the base (2) is synchronised
with feeding of the heating element (14); and providing means (28)
for applying localised edgewise pressure to the heating element
(14), as it is progressively fed and guided into overlying edgewise
relationship with the base (2), to urge the heating element (14)
towards the base (2) and cause an edge portion (22) of the heating
element (14), or at least one part (22) secured to the heating element
(14) and extending edgewise therefrom, to become secured by embedding
in the base (2).
2. A method according to claim 1, wherein the elongate corrugated
metal ribbon heating element (14) is initially formed by corrugation
of a substantially planar elongate metal ribbon (16).
3. A method according to claim 1 wherein the edge portion (22)
of the elongate corrugated metal ribbon heating element (14) which
is secured by embedding in the base (2) comprises an edge region
selected from a continuous edge region (22) of the element (14),
and tabs (22) extending from and integral with the element (14).
4. A method according to claim 1, wherein the at least one part
(22) secured to the elongate corrugated metal ribbon heating element
(14) and extending edgewise therefrom and secured by embedding in
the base (2), comprises at least one tab (22) secured to the heating
element (14).
5. A method according to claim 1 wherein the means (24, 26) for
feeding and guiding the elongate corrugated metal ribbon heating
element (14) comprises an arrangement selected from a tube arrangement
and a channel arrangement (24).
6. A method according to claim 1 wherein the means (24, 26) for
feeding and guiding the elongate corrugated metal ribbon heating
element (14) is associated with means (26) selected from means for
establishing and means for maintaining a desired upstanding orientation
of the heating element (14).
7. A method according to claim 6, wherein the means (26) for establishing
and maintaining a desired upstanding orientation of the heating
element (14) comprises intermeshing rotatable gear wheels (27),
complementary to a corrugation profile of the heating element (14),
and between which the heating element (14) is arranged to be fed.
8. A method according to in that claim 1, wherein the means (6,
8) for supporting the base (2) is mechanically driven, such that
motion selected from rotational motion and translational motion
of the base (2) is effected in synchronisation with the feeding
of the heating element (14) and whereby a desired pattern is effected
for the secured heating element (14).
9. A method according to claim 8, wherein the means for mechanically
supporting the base (2) is driven by motor means.
10. A method according to claim 1, wherein the means (28) for applying
localised edgewise pressure to the heating element (14) comprises
an arrangement selected from a block, cam, wheel and roller arrangement.
11. A method according to claim 10, wherein the means (28) for
applying localised edgewise pressure is of stepped form.
12. A method according to claim 11, wherein the means (28) for
applying localised edgewise pressure is of stepped roller form,
having a portion (30) for edgewise engagement with the heating element
(14) and at least one portion (32) for engaging the surface of the
base (2), whereby embedding of the element (14), or part or parts
(22) secured thereto, of the element (14) into the base (2) is limited.
13. A method according to claim 1, wherein the means (28) for applying
localised edgewise pressure is movable so as to be sequentially
advanced towards, and retracted away from, the base (2).
14. A method according to claim 13, wherein the means (28) for
applying localised edgewise pressure is movable by means selected
from electromagnetic, piezoelectric, pneumatic and hydraulic means.
15. A method according to claim 1 wherein feeding of the heating
element (14) is effected by feeding selected from continuous feeding
and feeding in discrete steps.
16. A method according to claim 15, wherein the feeding is in discrete
steps and is synchronised with sequential advancement and retraction
of the means (28) for applying localised edgewise pressure to the
heating element (14).
17. A method according to claim 15, wherein the feeding is continuous
and the means (28) for applying localised edgewise pressure to the
heating element (14) is arranged to be continuously cyclically advanced
and retracted towards and away from the base (2).
18. A method according to claim 17, wherein the means (28) for
applying localised edgewise pressure is caused to be vibrated, whereby
it is rapidly cyclically advanced and retracted towards and away
from the base (2).
19. A method according to claim 1, wherein the base (2) of thermal
and electrical insulation material comprises microporous thermal
and electrical insulation material.
20. A method according to claim 1, wherein the base (2) of thermal
and electrical insulation material is contained in a support dish
(4).
21. A method according to claim 20, wherein the support dish (4)
comprises metal.
22. Apparatus for manufacturing an electric heater in which an
elongate corrugated metal ribbon heating element (14) is supported
edgewise on a base (2) of thermal and electrical insulation material,
the heating element (14) having one of an edge portion (22) thereof
and at least one part (22) secured thereto and extending edgewise
therefrom, secured by embedding in the base (2), the apparatus comprising
means (24, 26) for feeding and guiding an elongate corrugated metal
ribbon heating element (14) progressively into overlying edgewise
relationship with a base (2) of thermal and electrical insulation
material; means (6, 8) for supporting the base (2) and for effecting
relative motion between a surface of the base (2) and the means
(24, 26) for feeding and guiding the heating element (14), such
that motion of the base (2) is synchronised with feeding of the
heating element (14); and means (28) for applying localised edgewise
pressure to the heating element (14) as it is progressively fed
and guided into the overlying edgewise relationship with the base
(2), to urge the heating element (14) towards the base (2) and cause
an edge portion (22) of the heating element (14), at least one part
(22) secured to the heating element (14) and extending edgewise
therefrom, to become secured by embedding in the base (2).
23. Apparatus as claimed in claim 22, wherein the elongate corrugated
metal ribbon heating element (14) is initially formed by corrugation
of a substantially planar elongate metal ribbon (16).
24. Apparatus as claimed in claim 22 wherein the edge portion (22)
of the elongate corrugated metal ribbon heating element (14) which
is secured by embedding in the base (2) comprises an edge region
selected from a continuous edge region (22) of the element (14),
and tabs (22) extending from and integral with the element (14).
25. Apparatus as claimed in claim 22 wherein the at least one part
(22) secured to the elongate corrugated metal ribbon heating element
(14) and extending edgewise therefrom and secured by embedding in
the base (2), comprises at least one tab (22) secured to the heating
element (14).
26. Apparatus as claimed in claim 22, wherein the means (24, 26)
for feeding and guiding the elongate corrugated metal ribbon heating
element (14) comprises an arrangement selected from a tube arrangement
and a channel arrangement (24).
27. Apparatus as claimed in claim 22, wherein the means (24, 26)
for feeding and guiding the elongate corrugated metal ribbon heating
element (14) is associated with means (26) selected from means for
establishing and means for maintaining a desired upstanding orientation
of the heating element (14).
28. Apparatus as claimed in claim 21, wherein the means (26) for
establishing and maintaining a desired upstanding orientation of
the heating element (14) comprises intermeshing rotatable gear wheels
(27), complementary to a corrugation profile of the heating element
(14), and between which the heating element (14) is arranged to
be fed.
29. Apparatus as claimed in claim 22, wherein the means (6, 8)
for supporting the base (2) is mechanically driven, such that motion
selected from rotational motion and translational motion of the
base (2) is effected in synchronisation with the feeding of the
heating element (14) and whereby a desired pattern is effected for
the secured heating element (14).
30. Apparatus as claimed in claim 29, wherein the means (6, 8)
for supporting the base (2) is driven by motor means.
31. Apparatus as claimed in claim 22, wherein the means (28) for
applying localised edgewise pressure to the heating element (14)
comprises an arrangement selected from a block, cam, wheel and roller
arrangement.
32. Apparatus as claimed in claim 31, wherein the means (28) for
applying localised edgewise pressure is of stepped form.
33. Apparatus as claimed in claim 32, wherein the means (28) for
applying localised edgewise pressure is of stepped roller form,
having a portion (30) for edgewise engagement with the heating element
(14) and at least one portion (32) for engaging the surface of the
base (2), whereby embedding of the element (14) into the base (2)
is limited.
34. Apparatus as claimed in claim 22 wherein the means (28) for
applying localised edgewise pressure is movable so as to be sequentially
advanced towards, and retracted away from, the base (2).
35. Apparatus as claimed in claim 34, wherein the means (28) for
applying localised edgewise pressure is movable by means selected
from electromagnetic, piezoelectric, pneumatic and hydraulic means.
36. Apparatus as claimed in claim 22, wherein feeding of the heating
element (14) is effected by feeding selected from continuous feeding
and feeding in discrete steps.
37. Apparatus as claimed in claim 36, wherein the feeding is in
discrete steps and is synchronised with sequential advancement and
retraction of the means (28) for applying localised edgewise pressure
to the heating element (14).
38. Apparatus as claimed in claim 36, wherein the feeding is continuous
and the means (28) for applying localised edgewise pressure to the
heating element (14) is arranged to be continuously cyclically advanced
and retracted towards and away from the base (2).
39. Apparatus as claimed in claim 38, wherein the means (28) for
applying localised edgewise pressure is caused to be vibrated, whereby
it is rapidly cyclically advanced towards and away from the base
(2).
40. Apparatus as claimed in claim 22, wherein the base (2) of thermal
and electrical insulation material comprises microporous thermal
and electrical insulation material.
41. Apparatus as claimed in claim 22, wherein the base (2) of thermal
and electrical insulation material is contained in a support dish
(4).
42. Apparatus as claimed in claim 41, wherein the support dish
(4) comprises metal.
43. A method according to claim 1, wherein the means (28) for applying
localised edgewise pressure is fixed at a predetermined distance
from the base (2).
44. A method according to claim 11, wherein the means (28) for
applying localised edgewise pressure is of stepped roller form,
having a portion (30) for edgewise engagement with the heating element
(14) and at least one portion (32) for engaging the surface of the
base (2), whereby embedding of at least one part (22) secured to
the element (14) into the base (2) is limited.
45. Apparatus as claimed in claim 22, wherein the means (28) for
applying localised edgewise pressure is fixed at a predetermined
distance from the base (2).
46. Apparatus as claimed in claim 32, wherein the means (28) for
applying localised edgewise pressure is of stepped roller form,
having a portion (30) for edgewise engagement with the heating element
(14) and at least one portion (32) for engaging the surface of the
base (2), whereby embedding of at least one part (22) secured to
the element (14) into the base (2) is limited.
Description [0001] This invention relates to a method and apparatus for manufacturing
an electric heater, such as a radiant electric heater for use in
a cooking appliance.
[0002] More particularly, the invention relates to a method and
apparatus for manufacturing an electric heater in which an elongate
corrugated metal ribbon heating element is supported edgewise on
a base of thermal and electrical insulation material, the heating
element having an edge portion thereof, or one or more parts secured
thereto, secured to the base by embedding in the base.
[0003] Electric heaters are well known for use in cooking appliances
in which an elongate corrugated metal ribbon heating element is
supported edgewise on a base of thermal and electrical insulation
material, such as microporous insulation material. Such heaters
are manufactured by a process in which an elongate planar ribbon
heating element is corrugated and then wound into a grooved press
tool, the press tool having a groove formed in a pattern corresponding
to that required for the heating element in the heater. The press
tool is urged towards the surface of an insulation base for the
heater, which is located in a special press, and an edge portion
of the ribbon heating element protruding from the press tool is
caused to be secured by embedding in the insulation base. The edge
portion of the ribbon heating element protruding from the press
tool is advantageously of profiled form such that it comprises spaced-apart
tabs or legs which are caused to be embedded in the insulation base.
Alternatively, the ribbon heating element can have separate tabs
secured thereto, such as by welding, and these tabs are arranged
to protrude from the press tool, for embedding in the insulation
base.
[0004] This prior art manufacturing process is disadvantageous.
Separate press tools have to be provided for each required pattern
and size of heating element and such press tools are expensive to
manufacture. They are also required to be used with expensive presses
producing the necessary high force to embed the heating element
in the insulation base. The process is therefore complex and labour-intensive.
[0005] It is an object of the present invention to overcome or
minimise these problems.
[0006] According to one aspect of the present invention there is
provided a method of manufacturing an electric heater in which an
elongate corrugated metal ribbon heating element is supported edgewise
on a base of thermal and electrical insulation material, the heating
element having an edge portion thereof, or one or more parts secured
thereto and extending edgewise therefrom, secured by embedding in
the base, the method comprising: providing means for feeding and
guiding an elongate corrugated metal ribbon heating element progressively
into overlying edgewise relationship with a base of thermal and
electrical insulation material; providing means for supporting the
base and for effecting relative motion between a surface of the
base and the means for feeding and guiding the heating element,
such that motion of the base is synchronised with feeding of the
heating element; and providing means for applying localised edgewise
pressure to the heating element, as it is progressively fed and
guided into the overlying edgewise relationship with the base, to
urge the heating element towards the base and cause an edge portion
of the heating element, or one or more parts secured to the heating
element and extending edgewise therefrom, to become secured by embedding
in the base.
[0007] According to a further aspect of the present invention there
is provided apparatus for manufacturing an electric heater in which
an elongate corrugated metal ribbon heating element is supported
edgewise on a base of thermal and electrical insulation material,
the heating element having an edge portion thereof, or one or more
parts secured thereto and extending edgewise therefrom, secured
by embedding in the base, the apparatus comprising: means for feeding
and guiding an elongate corrugated metal ribbon heating element
progressively into overlying edgewise relationship with a base of
thermal and electrical insulation material; means for supporting
the base and for effecting relative motion between a surface of
the base and the means for feeding and guiding the heating element,
such that motion of the base is synchronised with feeding of the
heating element; and means for applying localised edgewise pressure
to the heating element as it is progressively fed and guided into
the overlying edgewise relationship with the base, to urge the heating
element towards the base and cause an edge portion of the heating
element, or one or more parts secured to the heating element and
extending edgewise therefrom, to become secured by embedding in
the base.
[0008] The elongate corrugated metal ribbon heating element may
be initially formed by corrugation of a substantially planar elongate
metal ribbon.
[0009] The edge portion of the elongate corrugated metal ribbon
heating element which is secured by embedding in the base may comprise
a continuous edge region of the element, or tabs or legs extending
from and integral with the element.
[0010] The one or more parts secured to the elongate corrugated
metal ribbon heating element and extending edgewise therefrom and
secured by embedding in the base, may comprise one or more tabs
or legs secured to the heating element.
[0011] The means for feeding and guiding the elongate corrugated
metal ribbon heating element may comprise a tube or channel arrangement.
[0012] The means for feeding and guiding the elongate corrugated
metal ribbon heating element may be associated with means for establishing
and/or maintaining a desired upstanding orientation of the heating
element, such as intermeshing rotatable gear wheels, complementary
to a corrugation profile of the heating element, and between which
the heating element is arranged to be fed.
[0013] The means for supporting the base may be mechanically driven,
such as by motor means, such that rotational and/or translational
motion of the base is effected in synchronisation with the feeding
of the heating element and whereby a desired pattern is effected
for the secured heating element.
[0014] The means for applying localised edgewise pressure to the
heating element may comprise a block, cam, wheel or roller arrangement.
Such means for applying localised edgewise pressure may be of stepped
form, such as stepped roller form, having a portion for edgewise
engagement with the heating element and one or more portions for
engaging the surface of the base, whereby embedding, into the base,
of the element, or part or parts secured thereto, is limited.
[0015] The means for applying localised edgewise pressure may be
located at a predetermined fixed distance from the base or may be
adapted to be sequentially advanced towards, and retracted away
from, the base, such as by electromagnetic, piezoelectric, pneumatic
or hydraulic means.
[0016] Feeding of the heating element may be effected continuously
or in discrete steps. When the feeding is in discrete steps, such
feeding may be synchronised with sequential advancement and retraction
of the means for applying localised edgewise pressure to the heating
element. When the feeding is continuous, the means for applying
localised edgewise pressure to the heating element may be arranged
to be continuously cyclically advanced and retracted towards and
away from the base.
[0017] The means for applying localised edgewise pressure may be
caused to be vibrated, whereby it is rapidly cyclically advanced
and retracted towards and away from the base.
[0018] The base of thermal and electrical insulation material may
comprise microporous thermal and electrical insulation material
and may be contained in a support dish, such as of metal.
[0019] For a better understanding of the present invention and
to show more clearly how it may be carried into effect, reference
will now be made, by way of example, to the accompanying drawings
in which:
[0020] FIG. 1 is a schematic view of an embodiment of apparatus
according to the present invention for manufacturing an electric
heater;
[0021] FIG. 2 is a detail showing an arrangement in the apparatus
of FIG. 1 for maintaining and/or establishing a desired orientation
of a heating element during feeding thereof;
[0022] FIG. 3 is a plan view of an electric heater produced by
the apparatus of FIG. 1;
[0023] FIGS. 4 and 5 are side views showing alternative press arrangements
for use in the apparatus of FIG. 1;
[0024] FIG. 6 is a perspective view of a stepped press arrangement
for use in the apparatus of FIG. 1;
[0025] FIG. 7 shows a stepwise operating scheme for a movable press
arrangement in the apparatus of FIG. 1; and
[0026] FIG. 8 shows a continuous operating scheme for a movable
press arrangement in the apparatus of FIG. 1.
[0027] Referring to FIG. 1, an electric heater, such as for use
in a cooking appliance, is manufactured by providing a base 2 of
thermal and electrical insulation material. The thermal and electrical
insulation material suitably comprises microporous thermal and electrical
insulation material and is optionally provided in a metal support
dish 4.
[0028] The base 2 of insulation material is arranged to be located
on a supporting means 6 which is connected to a drive mechanism
8 which operates to effect rotational motion of the base 2, as indicated
by arrow 10, and/or translational motion of the base 2, as indicated
by arrows 12.
[0029] An elongate corrugated metal ribbon heating element 14 is
produced in well known manner from a substantially planar ribbon
16. The heating element 14 has an upper edge 18 and a lower edge
20. The lower edge 20 is provided with spaced-apart tabs or legs
22, although this is not essential. The tabs or legs 22 can be formed
as an integral part of the heating element 14 or can be manufactured
separately and secured to the heating element 14, such as by welding,
and such that they extend edgewise from the heating element 14.
[0030] The ribbon heating element 14 is arranged to be progressively
fed and guided through a tube or channel means 24 into overlying
edgewise relationship with the base 2 of thermal and electrical
insulation material.
[0031] In order to ensure that the ribbon heating element 14 is
established and/or maintained in an upstanding overlying edgewise
relationship with the surface of the base 2, the heating element
14 is passed through an arrangement 26, as shown in FIG. 2, located
at the end of the tube or channel means 24. The arrangement 26 comprises
intermeshing rotatable gear wheels 27, complementary to a corrugation
profile of the ribbon heating element 14 and between which the heating
element 14 is fed.
[0032] The tube or channel means 24 is fixed and the heater base
2 is arranged to undergo rotational and/or translational motion
relative thereto on its supporting means 6, by means of the drive
mechanism 8.
[0033] The base 2 is caused to undergo appropriate rotational and/or
translational motion in synchronisation with progressive feeding
of the heating element 14 through the tube or channel means 24.
As the heating element 14 advances progressively into overlying
edgewise relationship with the base 2, it passes beneath an arrangement
28 which applies localised pressure edgewise to the upper edge 18
of the heating element 14. The applied pressure from the press arrangement
28 forces the tabs or legs 22 on the lower edge 20 of the heating
element 14 into the surface of the base 2 and they become securely
embedded in the base 2. In this way, the heating element 14 is secured
to the base 2.
[0034] By appropriate selection of the rotational 10 and translational
12 motion of the supporting means 6, on which the base 2 is located,
during feeding of the heating element 14, a desired pattern of the
heating element 14, secured to the base 2, is obtained. An example
of such a secured heating element 14 is shown in FIG. 3.
[0035] The press arrangement 28 for applying localised pressure
to the heating element 14 suitably comprises a block, cam, wheel
or roller arrangement. As shown in FIGS. 4 and 5, the press arrangement
28 can be static and fixed at a predetermined distance from the
surface of the base 2. The fed ribbon 14 is effectively squeezed
between the press arrangement 28 and the surface of the base 2 and
forcibly embedded into the base 2. As shown in FIG. 4, the press
arrangement 28 comprises a block or cam and as shown in FIG. 5,
the press arrangement 28 comprises a wheel or roller. Such wheel
or roller 28 can be arranged to be rotated either by contact with
the advancing heating element 14 or by a motor means (not shown).
[0036] As shown in FIG. 6, the press arrangement 28 can be a roller
of stepped form, having a central portion 30 arranged to engage
the upper edge of the heating element 14, and outer portions 32
arranged to engage the surface of the base 2 to limit embedding
of the tabs or legs 22 on the heating element 14 into the base 2.
[0037] The press arrangement 28 for applying localised pressure
to the heating element 14 can be movable and arranged to be advanced
towards, and retracted away from, the base 2 by operating means
such as electromagnetic, piezoelectric, pneumatic or hydraulic means.
In one such arrangement, as illustrated by steps (A), (B) and (C)
in FIG. 7, feeding of the heating element 14 is effected in discrete
steps, in synchronisation with movement of the base 2. As shown
in step (A), a portion of the heating element 14 is advanced and
stops under the press arrangement 28. The press arrangement 28 is
then advanced by its operating means 34 to apply pressure to the
portion of the heating element 14 and embed the tabs or legs thereon
into the base 2, as shown in step (B). As shown in step (C), the
press arrangement 28 is then retracted by its operating means 34
and the base 2 moves to allow a further portion of the heating element
14 to be advanced into a position ready for being engaged by the
press arrangement 28.
[0038] In another arrangement, as shown in FIG. 8, the heating
element 14, in synchronisation with the base 2, is fed continuously
beneath the press arrangement 28, which is adapted to undergo slow
or fast cyclic up and down motion to operate on the heating element
14 to press the tabs or legs 22 thereon into the base 2. Fast cyclic
up and down motion can be effected by electromagnetic or piezoelectric
means 36, such that the press arrangement 28 effectively undergoes
vibrating motion during operation. |