US3758750A - Surface heating apparatus having one or more heating elements in its heating - Google Patents

Surface heating apparatus having one or more heating elements in its heating Download PDF

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Publication number
US3758750A
US3758750A US00219390A US3758750DA US3758750A US 3758750 A US3758750 A US 3758750A US 00219390 A US00219390 A US 00219390A US 3758750D A US3758750D A US 3758750DA US 3758750 A US3758750 A US 3758750A
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United States
Prior art keywords
groove
heating
thread
heating element
layer
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Expired - Lifetime
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US00219390A
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English (en)
Inventor
Toorn C Van
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TOORN C VAN
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TOORN C VAN
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21F—WORKING OR PROCESSING OF METAL WIRE
    • B21F15/00—Connecting wire to wire or other metallic material or objects; Connecting parts by means of wire
    • B21F15/10—Connecting wire to wire or other metallic material or objects; Connecting parts by means of wire wire with sheet metal
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H05B3/20—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater
    • H05B3/22—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible
    • H05B3/28—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible heating conductor embedded in insulating material
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H05B3/20—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater
    • H05B3/22—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible
    • H05B3/28—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible heating conductor embedded in insulating material
    • H05B3/30—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible heating conductor embedded in insulating material on or between metallic plates
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H05B3/40—Heating elements having the shape of rods or tubes
    • H05B3/42—Heating elements having the shape of rods or tubes non-flexible
    • H05B3/48—Heating elements having the shape of rods or tubes non-flexible heating conductor embedded in insulating material
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H05B3/68—Heating arrangements specially adapted for cooking plates or analogous hot-plates
    • H05B3/688—Fabrication of the plates

Definitions

  • ABSTRACT Heating apparatus provided with resistance threads lying close to the temperature contact surface thereof and being embedded in grooves which show a crosssectional area increasing towards and extending to the bottom of the groove, preferably dove-tail shaped, in which grooves the threads are rolled-in leaving clear near to the bottom a space around that thread half that is facing said groove bottom. Said space serves among other things as heat barrier and may be filled under extreme circumstances with a heat insulating material.
  • the heating apparatus can have many applications such as a hot plate, or in calendering or rolling various kinds of material.
  • a special application is stripping off the back-layer of a wide self-adhesive tape for which purpose a crack-back-roll has been developed in which the back-layer of the tape is caused to release from the adhesive layer by crack-building created by intensive radiation heat. Temperatures are lying in the reach between 1,000 and 2,000C requiring special resistance threads. The invention describes how such resistance threads can be embedded into the grooves.
  • the invention relates to a heating apparatus having a member being electrically heatable by means of one or more electrical resistance threads of the coaxial type, situated adjacent the temperature contact surface which elements are disposed in one or more grooves extending continuously in the material of the member, in each of which a resistance thread is rolled-in, the coverage of said threads being established by means of a separate thin metallic layer applied onto the member by spraying, shrinking or in any other suitable manner and constituting its temperature contact surface.
  • a heating member can be shaped as a bent or a flat body.
  • the grooves are having a cross-sectional area flaring towards and extending to the bottom of the groove, each thread being more or less ovally flattened over its full length by the rolling-in step, such that the greatest dimension of the flattened thread runs parallel to the temperature contact surface, while still some space being left around that half of the threads facing the groove bottom.
  • the flaring shape of the cross-sectional groove area extending to the groove bottom provides a space bounded on the one hand by the walls of the groove bottom and groove flanks and on the other hand by that half of the resistance thread adjacent to the groove bottom.
  • This space serves not only to compensate for the thermal expansion of the resistance thread but also as a heat barrier.
  • the second effect is based upon the heat-insulating property of the air trapped within said space and has as a consequence that the greater part of the heat produced in the resistance thread is propagated over the shortest distance towards the temperature contact surface, whereas a minor portion of said heat flows away in the opposite direction or sideways in respect of the main direction of the heat flow.
  • the thread over its lower half is completely enclosed by the groove bottom and flanks so that relatively much heat is flowing away therethrough.
  • the cross-sectional area of the groove is shaped as a'dove-tail.
  • the groove bottom is flat or has a curve being opposite to that of the adjacent thread half.
  • a'me'thod which is characterised by the steps that in the heating member a groove is shaped having a cross-sectional area flaring towards and extending to the groove bottom, and a heating resistance thread is disposed and rolled within said flaring groove under transverse deformation whilst leaving space around that half of the thread facing the groove bottom.
  • asbestos material may be employed shaped in the form of a rope or ribbon, commercially available under the trade name Fiberfrax.
  • F I08. 1 and 2 relate to a conventional method of rolling-in a heating resistance thread of the coaxial type into a surface of a heating member
  • FIGS. 3, 4 and 5 show a first embodiment in accordance with the invention for placing a heat resistance thread into a heating member
  • FIGS. 6 and 7 show a second embodiment in accordance with the invention in which use is made of an insulating material in the groove;
  • FIG. 8 shows an embodiment in accordance with the invention in which the bottom of the dove-tail groove is vaulted
  • FIG. 9 shows an alternative embodiment in accordance with the invention in which use is made of a canthal thread as the resistance thread
  • FIG. 10 shows an arrangement for the controlled adjustment of the distance between the heating thread and the object to be heated.
  • FIG. 11 shows schematically an arrangement for a crack-back roll to be applied for stripping the backlayer of a self-adhesive tape.
  • a heating resistance thread or element 3 of the coaxial type is placed in a cylindrical surface 2 having therein a continuous spiral-shaped groove 1 and is flattened by the action of a roll 4. It takes then the shape indicated at 5.
  • the thread comprises a metallic jacket 6 made of copper, a core 7 and an insulating mass 8 made of sintered aluminium oxyde.
  • a metallic layer 9 is applied, it will show a number of dislocations 10 and 11. Said layer 9 is not smooth and ought to be ground. After grinding this layer, its thickness is extremely thin at the place of the dislocation. It appears that during the heat treatment the thread 3 can be pushed out of the groove 1 rather easily.
  • the thread or element can be kept in place well when the heating thread is enclosed in a groove 12 flaring towards its depth of which the cross-sectional area has the shape of a dovetail (FIG. 3).
  • the heating base member 13 can be shaped as a plate, in which a plurality of grooves 12 are running parallel to each other. It can also be shaped as roll, having in its outer surface a continuous parallel shaped groove 12.
  • the thread 14 has a cross-sectional area, its width being greater than the smallest width of the groove. It does not project above the groove.
  • This heating member 13 is covered with a metallic layer 15 being applied in the usual manner.
  • the more or less oval cross-sectional area of the thread 14 can be obtained by disposing into the groove 17 a thread 16 with circular cross-sectional area and thereafter deforming it by means of a tool 18 indicated with dotted lines; the thread will then obtain the shape indicated at 19 (FIG. 4). It will be clear that the thread can only be deformedto a very restricted degree so that the dove-tail shaped cross-sectional area is filled only partially and a space 32 (FIGS. 3-5) is left allowing compensation for thermal expansion and partially acting as a heat barrier.
  • a flattened shape is given to a round thread (FIG. 5).
  • the smallest thickness of the flattened thread 20 is a little smaller than the width of the groove 21, permitting it to be readily placed into the groove.
  • a roller-shaped means 22 being movable-according to arrow 23
  • said thread 20 is deformed again and obtains the shape indicated at 24.
  • a ribbon 26 of thermic insulating material for instance asbestos fibres, can be placed into the groove prior to inserting the thread 27 (FIG. 6). After deformation of said thread 27 this material will fill the groove space 32 and assume the shape indicated at 28. The thread 29 is then over the greater part of its circumference thermically insulated from the heating member 30 except its side indicated at 31, being the heating side of the member 30.
  • the introduction of a ribbon 26 has the additional advantage that the thread 27 can be deformed in a more efficient way.
  • the bottom of the groove 12, 17 or 25 can also be vaulted, for instance, as shown in FIG. 8, possessing a curve being opposite to the curve of the adjacent half of the flattened thread 19 so that a larger remaining space 32 and thus a better thermal insulation are obtained.
  • a heating plate or heating oven being provided in accordance to the invention with grooved-in resistance threads is particularly suitable for all kinds of heat treatments, for instance electrical cooking, calendaring and rolling of various kinds of material, such as paper, fiber or plastic material.
  • a special application can be made of the invention in the so called crack-back rollheating.
  • a self-adhesive tape having a width of 'for instance 60 cm has to be stripped of its projecting backing-layer (back).
  • back backing-layer
  • Trials to remove this backing-layer in a chemical or mechanical way have sofar been crowned with little success. In the latter event the backing-layer is'torn orthogonally from the tape, but this requires relatively large forces.
  • a satisfying method can be ob- I tained by guiding the tape with its backing-layer in contact with the temperature contact surface 40 (see FIG. 7) in such a manner over the heating member that the longitudinal direction of the tape forms an angle of 45 with respect to the heating thread 29 in the heating member. If said threads are grooved in the heating member as a spiral with a pitch of for instance 7 cm, the backing-layer after the temperature is increased to more than 1,000C during which it cracks according to diagonally extending lines, can be pulled off the adhesive in a diagonal direction.
  • nickel chromium thread as the resistance thread in combination with a thermic insulating ribbon, such as morganite, (extruded aluminium oxyde), is Satisfying at temperatures up to 1,000C, one needs for this special application in which the possibility should be available to increase the temperature to 1,700C or even higher, likewise a special resistance thread.
  • canthal-thread is particularly suitable since it maintains at this very extreme temperature a constant diameter and so a constant electrical resistance.
  • This material has such a metallurgical composition that it forms, when heated, a skin, secluding itself from the air, so that it does not oxydize and therefore does not pulverize nor erode.
  • the groove 25 (see FIG. 9) in the heating member 30 is internally sprayed with a plasma 41 of aluminium oxyde. Thereafter a ribbon 28 of thermic insulating material is applied in the groove space 32 and subsequently the brittle, naked canthal-thread 42 is carefully disposed into the groove 25. Since the exposed side 43 of the thread is not electrically insulated, a thin fleece of boran 44 is applied which fleece is electrically but not thermically insulating.
  • the canthal-thread as resistance thread can be replaced by disposing a coaxial cable into the groove, of which the insulating magnesium-oxide layer ensures the electrical insulation, but which is from a thermic point of view diathermic, so that the ribbon of for instance morganite cana reference plane.
  • a particular property of the canthal-thread 42 is that at the high temperatures to be applied it is affixed to the ribbon 28 by sintering, and the ribbon 28 in turn is affixed to the groove bottom 34 resulting in a rigid connection between the glow-element (the thread 42 itself) through the ribbon 28 towards the groove bottom 45.
  • Something similar occurs with the co-axial cable in which a sintering connection is formed between the magnesium layer, the ribbon and the bottom of the groove.
  • the paper of the back-layer may not be scorched nor burned but has to become exclusively by radiation heat so hot that it is cracking loose from the adhesive layer. So the resistance threads have to be arranged below the temperature contact surface at such a depth that the temperature delivered is nevertheless sufficient for the paper of the back-layer to get loose from the adhesive layer by radiation heat. While determining said depth one should also take into account the thickness which disappears during the finishing treatment by grinding off and the thickness of the finishing coating to be applied on the heating member.
  • a second dome-shaped roller 33 is used which is rotatable about the axis 34 and by means of which the heating side 31 of the thread 29 is gradually pushed farther into the groove 17.
  • FIG. 11 is schematically shown an arrangement of a crack-back roll. From left to right is represented a supply roll 52 containing the stock of the self-adhesive tape 53, said roll 52 being rotatable about an axis 51.
  • the tape 53 is fed through a span roller 54 to a heating apparatus 55 and is shown interrupted at that place for reasons of clarity.
  • the heating apparatus comprises a curved surface 56 in which a plurality of dove-tail shaped grooves 57 is arranged at an angle of 45 with respect to the travelling direction of the tape 53.
  • Said paper leaving continuously the heating apparatus 55 shows a pattern of burst lines 59 extending under an angle of 45 which lines are indicated as dotted lines in the figure. This pattern can, dependent on the travelling speed of the tape, be made coarser or finer.
  • the tape passes subsequently a span roller 60 and leaves the installation through pinch rollers 61 and 62.
  • An electric heating device comprising a base metal member having'a heating surface provided with at least one continuous groove, the width of said groove increasing from its opening toward its bottom, an electrical sheathed heating element positioned in said groove, said heating element having a substantially oval cross section with the longest dimension thereof parallel to said heating surface and greater than the width of the groove opening, and the corss-sectional areas and shapes of said heating element and said groove being respectively so related to each other as to provide aspace between the heating element and at least a portion of the groove bottom, said space being substantially filled with a thermally insulating material, whereby said heating element, upon thermal expansion, is confined within said groove, and whereby the major portion of the heat produced by said heating element is effectively transmitted directly toward said heating surface, with only a minor portion of said heat flowing in other directions outwardly from said groove, and a thin metallic layer covering the grooved heating surface.
  • a device in which the groove bottom is convexly curved with reference to the heating element.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Resistance Heating (AREA)
US00219390A 1971-01-21 1972-01-20 Surface heating apparatus having one or more heating elements in its heating Expired - Lifetime US3758750A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL7100788A NL7100788A (cg-RX-API-DMAC10.html) 1971-01-21 1971-01-21

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3981233A (en) * 1975-10-03 1976-09-21 Restaurant Technology, Inc. Anti-stick grill
US4045653A (en) * 1976-06-28 1977-08-30 National Presto Industries, Inc. Electric cooker with press-staked heating element and method of making the same
US4481407A (en) * 1980-05-12 1984-11-06 Stokes (Australasia) Limited Electric hotplate
US4894515A (en) * 1985-04-08 1990-01-16 The Kanthal Corporation Hot plate for cooking
DE20108963U1 (de) 2001-05-29 2001-08-16 Türk & Hillinger GmbH, 78532 Tuttlingen Elektrischer Flachheizkörper
US20080031604A1 (en) * 2004-10-05 2008-02-07 Kerschbaum, Wolfgang Heating Device
US20110179957A1 (en) * 2010-01-25 2011-07-28 Shyh-Ming Chen Method for flattening heat dissipating tube and device for performing the same
US20150001207A1 (en) * 2011-03-30 2015-01-01 Kyocera Corporation Heater

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3981233A (en) * 1975-10-03 1976-09-21 Restaurant Technology, Inc. Anti-stick grill
US4045653A (en) * 1976-06-28 1977-08-30 National Presto Industries, Inc. Electric cooker with press-staked heating element and method of making the same
US4481407A (en) * 1980-05-12 1984-11-06 Stokes (Australasia) Limited Electric hotplate
US4894515A (en) * 1985-04-08 1990-01-16 The Kanthal Corporation Hot plate for cooking
DE20108963U1 (de) 2001-05-29 2001-08-16 Türk & Hillinger GmbH, 78532 Tuttlingen Elektrischer Flachheizkörper
US20080031604A1 (en) * 2004-10-05 2008-02-07 Kerschbaum, Wolfgang Heating Device
US20110179957A1 (en) * 2010-01-25 2011-07-28 Shyh-Ming Chen Method for flattening heat dissipating tube and device for performing the same
US20150001207A1 (en) * 2011-03-30 2015-01-01 Kyocera Corporation Heater
US9681498B2 (en) * 2011-03-30 2017-06-13 Kyocera Corporation Heater with particle shield for noise

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Publication number Publication date
NL7100788A (cg-RX-API-DMAC10.html) 1972-07-25

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