Abstract: An induction energy transmission system includes a supply unit having a supplying induction element for supplying energy, and a receiving unit having a receiving induction element that receives energy from the supplying induction element when in an operational state a shortest connection between the supplying induction element and the receiving induction element is minimal. The supplying induction element has a sub-region which, in the operational state, is oriented at an angle relative to a plane that is at least substantially perpendicular to the shortest connection between the supplying induction element and the receiving induction element.

Abstract: Methods and apparatus to reduce biological carryover using induction heating are disclosed herein. An example method includes washing an aspiration and dispense device. The example method includes generating an alternating electromagnetic field and introducing the aspiration and dispense device into the alternating electromagnetic field. The example method includes inductively heating the aspiration and dispense device with the alternating electromagnetic field. In the example method, the washing is to occur in concert with the heating.

Abstract: A method for welding at least two parts including a thermoplastic material and having respective surfaces to be welded, including: inserting an insert between the surfaces to be welded of the two parts; generating heat via the insert; wherein the insert moves in relation to the parts to be welded in a welding direction. Also, an installation adapted for implementation of this method.

Abstract: A conductive wire welded structure of which a stator is composed can be obtained using a conductive wire welding method in which a plurality of conductive wires are welded together using a high-frequency induction heating device. This conductive wire welding method involves performing a disposition step in which a plurality of conductive wires are made to intersect and the end of at least one of the conductive wires is disposed at a location that is extended from an intersection portion, and a welding step in which the end of the at least one conductive wire that is at a location extended from the intersection portion is welded outside an induction heating coil by induction heating, and the welded material thereof is solidified at the intersection portion.

Abstract: An apparatus for hardening a spring having a helical or beehive shape. The apparatus has a rotation support system and an induction heating system. The rotation support system is designed to support the spring while the spring is heated by the induction heating system. The induction heating system has an induction coil system having a coil system. The coil system has a spaced region designed to receive the spring and to heat the spring while the spring is supported on the rotation support system.

Abstract: An openable induction coil is provided. An electromagnetically shielded inductor assembly can be formed from the openable induction coil and an electromagnetically shielded enclosure into which the coil can be inserted. The induction coil can be pivoted open while in the shielding enclosure without complete disassembly of the enclosure. In some examples of the invention, a dynamic “curtain” of a gas is injected through spaces between opening portions of the coil and adjacent sections of the shielding enclosure, and into the interior of the induction furnace formed by the openable induction coil when it is in the closed position.

Abstract: A method and device for heating or hardening at least an axial segment of a rotationally-symmetric surface of a work piece includes rotating the work piece about its rotational axis and moving a peripheral portion of an inductor along a longitudinal profile of the axial segment of the rotating work piece with a constant spacing between the peripheral portion and the axial segment. At least a portion of the movement of the peripheral portion is composed of a first vector component in the direction of the rotational axis and a second component extending perpendicularly to the first vector component. The peripheral portion has a length in the rotational axis direction that is less the length of the axial segment in the rotational axis direction.

Abstract: An induction heating apparatus for heating a traveling metal plate includes an induction coil for surrounding the metal plate. The induction coil includes an upper induction coil for being located above the metal plate and a lower induction coil for being located below the metal plate. The upper and lower induction coils are spaced from each other in a longitudinal direction of the metal plate a constant distance across a transverse direction of the metal plate. Each of the upper induction coil and the lower induction coil is arranged obliquely at an edge area of the metal plate so as to form an oblique angle with the transverse direction of the metal plate.

Abstract: The present invention is one that uniformly and simultaneously heats a plurality of cup-shaped or annular metallic bodies to improve productivity, and has a plurality of divided core parts formed by dividing an annular core; configured such that a plurality of divided end parts of the divided core part are respectively attached with metallic bodies W made of non-magnetic metal; and inductively heats the metallic bodies W through input windings provided in outer or inner circumferential parts of the metallic bodies W.

Abstract: The invention relates to a device for curing a plastic material, in particular a sealing compound and/or a filling compound for tolerance adjustment or gap filling, respectively, wherein the plastic material is at least partly inserted in a gap area between two components, and wherein at least one of the components is made of a fiber reinforced plastic material, in particular of a carbon fiber reinforced epoxy resin. According to the invention the device is provided with at least one electromagnetic inductor for a locally defined heating of the gap area and for curing the plastic material arranged in the gap area. Due to the electromagnetic inductor which might be a linear inductor or a circular inductor a contact-less and fast curing of the plastic material is possible.

Abstract: A soldering head for an induction-soldering apparatus for soldering a contact strip onto a solar cell and a soldering process using the soldering head are provided. The soldering head has a soldering side, with which the soldering head is placed onto the site to be soldered during the soldering process, an inductor loop with a feed region and a coupling-out region arranged on the soldering side, a main body made of an electrically non-conductive material, and a fastener, with which the main body is fixed to the inductor loop, wherein the coupling-out region of the inductor loop is exposed on the soldering side, and the main body has one or more spacer elements, on the soldering side, which are arranged outside the coupling-out region and protrude beyond the coupling-out region of the inductor loop.

Abstract: The present invention is an inductive sealing unit, which includes a conductive coil assembly that has at least two sections. At least one of the sections is adjustable with respect to the other. Each section has a magnetic flux concentrator, such as a ferrite core. A flexible conductive coil, such as litz wire, is disposed with respect to the magnetic flux concentrator to provide an electromagnetic field which induces heat sufficient to seal an object. The assembly can be adjusted to accommodate different size objects to be sealed.

Abstract: The invention concerns an apparatus (1) for inductively heating an electrically conductive workpiece (2) in the form of a closed ring, the apparatus having a U-shaped magnet core (3) with two legs (4), with an electrically conducting coil (5) arranged on at least one leg (4) of the U-shaped magnet core (3) and connectable with an alternating current source, and a magnet yoke (6) which is spaced from at least one freestanding end of a leg (4) of the U-shaped magnet core (3), so that a closed magnetic circuit with at least one air gap (7) is formed, the height of the air gap (7) being so chosen that the electrically conductive workpiece (2) can be moved in a non-contacting manner into the air gap (7).

Abstract: A portable induction tool is provided for soldering or brazing sections of metal pipe together. A work coil head (with induction coil) is U-shaped, allowing placement of the head around lengths of pipe, heating a susceptor (e.g., the pipe) to form a joint, and then to be withdrawn after the pipe joint is made. In one form, the tool uses heat pipes to remove thermal energy from the head, and also a heat exchanger for higher-powered units. Power capacitors are generally included with the induction (work) coil to create a tank circuit of a resonant frequency. The induction coil uses Litz wire, copper tubing, or heat pipes with a conductive outer skin to carry the high-current being delivered to the induction coil. The induction coil has a general racetrack configuration, which is typically wound in a U-shape (or as a semicircle) as a single winding, with multiple turns.

Abstract: An image forming apparatus includes a fixing device which fixes a toner image on a recording medium. The fixing device includes a heating device. The heating device includes a heat-generating member, an exciting member, and a changing device. The heat-generating member is subjected to electromagnetic induction heating. The exciting member is placed to sandwich a front surface and a rear surface of the heat-generating member, without contacting the heat-generating member. The changing device changes an opposing distance of the exciting member to at least one of the front surface and the rear surface of the heat-generating member.

Abstract: Magnetic heating device includes energy feeding elements, control unit and at least two magnetic field generators, where each magnetic field generator has two free ends. All free ends of the magnetic field generators define a plane and the control unit is adapted to control the feeding elements to apply magnetic field generating energy to the magnetic field generators to generate alternating magnetic fields, wherein a ferromagnetic material positioned in a space defined above the plane is heated. The generated magnetic fields being such that the magnetic field through one of the free ends has an opposed direction as compared to the magnetic fields through the other free ends.

Abstract: A portable induction tool is provided for soldering or brazing sections of metal pipe together. A work coil head (with induction coil) is U-shaped, allowing placement of the head around lengths of pipe, heating a susceptor (e.g., the pipe) to form a joint, and then to be withdrawn after the pipe joint is made. In one form, the tool uses heat pipes to remove thermal energy from the head, and also a heat exchanger for higher-powered units. Power capacitors are generally included with the induction (work) coil to create a tank circuit of a resonant frequency. The induction coil uses Litz wire, copper tubing, or heat pipes with a conductive outer skin to carry the high-current being delivered to the induction coil. The induction coil has a general racetrack configuration, which is typically wound in a U-shape (or as a semicircle) as a single winding, with multiple turns.

Abstract: An apparatus and process are provided for controlling the cross sectional temperature profile of a continuously moving workpiece with an induction coil assembly that provides for a combination of longitudinal and transverse magnetic flux field heating of the workpiece. The induction coil assembly includes means for laterally moving the workpiece in and out of the coil assembly without movement of the coil assembly.

Abstract: A portable induction tool is provided for soldering or brazing sections of metal pipe together. A work coil head (with induction coil) is U-shaped, allowing placement of the head around lengths of pipe, heating a susceptor (e.g., the pipe) to form a joint, and then to be withdrawn after the pipe joint is made. In one form, the tool uses heat pipes to remove thermal energy from the head, and also a heat exchanger for higher-powered units. Power capacitors are generally included with the induction (work) coil to create a tank circuit of a resonant frequency. The induction coil uses Litz wire, copper tubing, or heat pipes with a conductive outer skin to carry the high-current being delivered to the induction coil. The induction coil has a general racetrack configuration, which is typically wound in a U-shape (or as a semicircle) as a single winding, with multiple turns.

Abstract: An apparatus and process are provided for reducing the electromagnetic field intensity in selected regions for a field produced when ac current flows through one or more induction coils through which a workpiece moves for induction heating of the workpiece. The electromagnetic shield has transverse screen elements through which the workpiece moves at opposing ends of the one or more induction coils. One or two longitudinal screen elements connect the transverse screen elements.

Abstract: A process for the production of an inductor device comprising the steps of forming a green sheet to form an insulating layer; forming a plurality of conductive coil pattern units on the surface of the green sheet in order that a plurality of unit sections each including a single coil pattern unit are arranged on the surface of the green sheet and each two coil pattern units adjoining in the substantially perpendicular direction to the longitudinal direction of the unit sections are arranged centro-symmetrically with respect to a center point of a vertical boundary line of adjoining unit sections; stacking a plurality of green sheets formed with the plurality of coil pattern units arranged in centro-symmetry and connecting the upper and lower coil pattern units separated by the green sheets to form a coil shape; and sintering the stacked green sheets.

Abstract: There is disclosed an induction heating device or work coil for heating electroconductive material to a desired temperature. The work coil can be used on a roll or cylinder of any diameter. The work coil has an open core of ferrite material shaped in a U. Wire is wound around the opposing legs of the U so that on excitation one leg becomes the N pole and the other leg becomes the S pole and the polarity alternates as the polarity of the excitation current alternates. A substantially thin rectangular flat layer of ferrite can be attached to ends of each pole piece. Each layer of ferrite has having a length sufficient to cover bottom end of each leg and a width in the direction of an axis perpendicular to the face of the U that corresponds to the width of the desired control heating effect.

Abstract: The invention relates to a coil to be used in transverse flux induction heating of an object in the form of a metal strip or another elongate metal workpiece. The coil contains at least one pair of loops of conductors, which are non-symmetrically positioned to each other and the conductors overlap each other so that the inductor has double conductors across the object to be heated and a single conductor parallel to the object to be heated at the edges. The heating effect is prevented alone in the conductors by dividing the induced current for the conductors to two equal branches each having the same width as the original current and the combined heating effect in the branches is only half of the heating effect before branching.

Abstract: A transverse flux induction heating apparatus adjusts the level of edge heating of a workpiece by changing the pole pitch of induction coils forming the apparatus to provide a more uniform transverse temperature of the workpiece. Changes in the operating frequency of the induction power supply and in the distance between induction coils and workpiece are not required to adjust edge frequency heating. The pole pitch, and therefore, the level of edge heating can be continuously changed, or conveniently adjusted prior to a production run, in a high speed continuous heat treatment process for a workpiece.

Abstract: In transverse flux induction heating of electrically conductive strip, conductors that cross the strip width are stacked, or connected, such that a multiple of the induced current flows across the strip width as compared to that which flows along the strip edges. Conductors across the width of the strip and conductors along the edges of the strip are connected in series to insure that the current which flows in the conductors is everywhere the same. In the case of two stacked cross conductors, this gives an I2R heating of four times the heating across the strip width as compared to that along the strip edges.

Abstract: In a device for longitudinal field heating of metallic stock, a coil (21) having two coil halves (9, 10) is provided, through which the stock is to be guided. In this case, each coil half (9, 10) includes one or more turn halves (2, 3; 14, 15; 16, 17), which are arranged one behind the other in the transport direction of the stock, and connecting elements (7; 18). Each two turn halves (2, 3; 14, 15; 16, 17) assigned to one another form one complete turn (1), the ends of these turn halves (2, 3; 14, 15; 16, 17) ending at a slight distance to one another and each turn half end being connected in an electrically conductive way to a connecting element (7; 18). The respective connecting elements (7; 18) connected to neighboring ends of two turn halves (2, 3; 14, 15; 16, 17) form a pair insulated in relation to one another by solid insulators. For simple introduction and removal of the stock, the coil halves (9, 10) may be pulled apart transverse to the transport direction to form two introduction passages.

Abstract: A method for transverse flux induction heating using a heating machine including an iron core, that essentially has a U-shape with an opening facing downwards. The legs lie in contact with downwards facing displaceable core jaws. These are so arranged that they are displaceable towards and from each other by means of pneumatic pistons. The object that is to be heated is placed between the core jaws. The core jaws are at the displacement guided by means of U-shaped rails and rolls or linear bearings. The displacement serves among other things to free the object that is to be heated or has been heated for transport into and out from the machine. When the right position has been reached the displacement is stopped and the two core jaws are locked by a pressurized bellow pressing the core jaws upwards against the legs of the U-shaped core.

Abstract: A modular induction heated cooking hob inductor and hob are disclosed. The inductor is a wound conductor having turns at substantially right angles to previous turns. Parallel turns of the conductor are separated by a layer of insulation adjacent to the turns of the conductor. The hob may comprise multiple inductors. The inductor may have sensors for detecting a device to be heated and/or illuminatable segments that light up in response to the presence of an object to be heated.

Abstract: An apparatus for hardening cylindrical bearing faces (L) of a shaft (K), wherein at least one of the transitional radii (R1, R2) to the adjoining shaft portions (W1, W2) is constructed recessed, includes a pair of inductive heating units (1, 2), which are each formed at least by one inductor (3, 4) having two spaced-out heating conductor branches (20, 22; 21, 23); an adjusting device (11, 12) for adjusting the inductors (3, 4) simultaneously from the radial direction (R) on to the bearing face (L) to be hardened and a second adjusting device (13, 14) for moving at least the inductor (3, 4) associated with the recessed radius R1, R2) after application to the bearing face (L) by a movement directed axis-parallel with the longitudinal axis (X) of the shaft (K) in the direction of the recessed transitional radius (R1, R2) until its outer heating conductor branch (20) has moved into the particular transitional radius (R1, R2).

Abstract: An induction heating coil for joining structural members by heating a bonding material disposed between the structural members includes first and second elements with complementary shapes spaced equidistantly apart along the length of opposing surfaces of the structural members. Bases and risers connected to the first element to a source of high frequency electrical current. Conductive elements connect the first and second elements into a single turn coil. The first and second elements, and at least the riser, are formed of hollow, tubular members to form a coolant flow path therethrough.

Abstract: In an induction heating method for a manifold in a hot runner mold, it is possible to uniformly heat a material over the entire length of a runner. Also, a coil is easily attached to and detached from the manifold. The hot runner mold includes a fixed mold and a movable mold, and a space is provided along a side surface of the manifold on which clamping force applied by the fixed mold and the movable mold does not act. A coil is wound to the side surface along an axial line of a runner of the manifold within the space such that the manifold is induction-heated from the side surface.

Abstract: There are provided an induction heating coil for carrying out high frequency induction heating (heating during movement) of a hot rolled steel or the like by surrounding the hot rolled steel or the like which is placed on a plurality of conveying rollers and conveyed, and an induction heating apparatus using this induction heating coil. In an induction heating coil 2 for induction heating a heated body (a thin slab 8 or the like) by surrounding it, a first coil portion 13 wound in a spiral form while transferring in one direction (the direction of the arrow mark &agr;) along a coil axis S and a second coil portion 14 which is connected to a terminal (turn point 18) of the first coil portion 13 and wound back while transferring in the other direction (the direction of the arrow mark &bgr;) along the coil axis S are combined so as to overlap in the non-contact state.

Abstract: According to a method of melting a bump improved to omit processes of flux application, reflow, cleaning and drying, a bump formed on a substrate is heated and melted by electromagnetic induction using an induction heating coil in ambient of low oxygen concentration.

Abstract: A multi-station induction heat treatment system is used for heat treating metal workpieces that have multiple generally cylindrical components whose axes are parallel to and offset from a common workpiece axis. The heat treatment system includes heat treatment stations that heat treat while the workpiece and inductor components are stationary. The system is particularly suited to the heat treatment of workpieces, such as crankshafts, that have an intervening non-symmetrically shaped component between two substantially cylindrically shaped components, some of which are not coaxial, that must be heat-treated.

Abstract: The invention relates to a device for simultaneous peripheral electro-inductive hardening of bearing surfaces (2A, 3A) and transition A radii in crankshafts (1), comprising lifting pins (2, 3) arranged directly adjacent to each other and one behind the other with different angular positions on the plane perpendicular to the their axis of rotation (D), wherein inductors (8, 9) are provided which are placed on the lifting pins (2, 3) approximately in the same direction (C) thereof. A lifting pin (2, 3) is allocated to each inductor, which is arranged in such a way that it intersects the axial direction of the crankshaft (1). Said inductor comprises at least two inductor detents (8C, 8D, 9C, 9D) arranged parallel to each other. One inductor detent (8D, 9D) is arranged in an overlay area (4) of the lifting pins (2, 3) while the other inductor detent (8C, 9C) is arranged in an edge area of the lifting pin (2, 3) facing a cheek (5, 6).

Abstract: The invention relates to the rotary and simultaneous electroinductive hardening of the bearing surfaces (2a; 3a) of crank pins (2; 3) of a crankshaft (1) disposed immediately one beside the other and offset in relation to one another in the axial direction (D), having inductors (10; 11) which each engage around the crank pins (2; 3) by a maximum of 180.degree. and which each have two inductor branches (12, 13; 14, 15) arranged in parallel and following the curvature of the bearing surfaces (2a; 3a), of which one branch is associated with the overlapping zone (5) of the crank pins (2; 3), the other branch being associated with the particular other edge zone (2b; 3b) of the crank pin (2; 3) associated therewith, the inductor branches (12, 13; 14, 15) of each inductor (10; 11) having in the axial direction (D) a distance (A) increased in relation to half the total width (B) of the crank pins (2; 3).

Abstract: An induction heating device for surface treating the teeth (11) of a mechanical part on which each tooth (111) has a projecting tip (111s) and a tooth root linking the tooth to an adjacent tooth, wherein an in duction coil (12, 12') is spaced from the tooth tips and powered by at least one high-frequency current source. The coil consists of a set of conductive segments (24, 24') individually orthogonal to the generatrix (d, d') of the teeth, located above respective tooth tips and interconnected via connecting segments (25, 25').

Abstract: An induction heating apparatus for heating continuous strip material. In a first embodiment, two coil sections each having a gap at one end for the strip material to pass edgewise into and out of the apparatus for heating wherein the coil sections are adapted for connection to two power supplies such that the first power supply connects through one half-turn of each of the coil sections, and thence to the second power supply, which is connected through the second half-turns of the respective coil sections and back to the first power supply, all in series. In a second embodiment, the coil sections are adapted for connection to four power supplies in series; each power supply connected to a respective half-turn of the coil sections, such that one half-turn is connected between each of the four power supplies. The series connection ensures uniform amplitude and phase of the electrical current applied to the induction heating coil apparatus.

Abstract: An inductor for inductively heating bearing surfaces of a crankshaft is machined from a block of copper to provide parallel, closely spaced and integrally joined inductor block portions having machined coolant passages therein. The machined inductor is rigidly supported between juxtaposed side plates having portions of the inner surfaces thereof machined to provide recesses which receive the inductor and in which the inductor is clampingly engaged between the plates. Positioning fingers are supported by the side plates to accurately position the active face of the inductor relative to a bearing surface to be heated, and tubular leads extend upwardly between the side plates for connecting the inductor across a source of power. An inlet conduit for coolant extends laterally between the side plates, and the tubular leads provide outlets for coolant flow from the inductor.

Abstract: A high-frequency induction heating coil is provided which enables a semiconductor single crystal in the process of growth to incorporate impurities uniformly therein, permits ready adjustment of the heat distributing property, and precludes the discharge of electricity across a slit. The high-frequency induction heating coil comprises a pair of annular conductors 21 and 22, a pair of power source terminals 23a and 23b for feeding a high-frequency electric current to the pair of annular conductors 21 and 22, and a plurality of small coils 24a through 24f and 25a through 25f having the pair of annular conductors as opposite electrodes and projecting toward the axis of the pair of annular conductors extending from a first annular conductor 21 to a second annular conductor 22.

Abstract: An inductive device can heat a body having a slender bore, with an inductor assembly that includes a coolant system. The assembly has a parallel pair of elongate inductors sized to fit deep inside the bore. Each of these inductors has a distal end and a proximal end. The distal ends of the inductors can be electrically interconnected. These inductors are adapted at their proximal ends to connect to a source of current for circulating current along the inductors. The coolant system is adapted to communicate with a source of coolant to circulate coolant along the inductors. The inductors are inserted through the bore of the body to lie lengthwise, without coiling, along the length of the bore. Coolant can then be pumped along the elongate inductors. Then by driving alternating current to flow through the inductors, magnetic coupling to the body occurs to produce heating effects.

Abstract: An induction heating coil apparatus for heating continuous strip material comprising at least a pair of generally rectangular full-turn coils arranged in parallel relation and separated from each other to permit continuous strip material to pass axially through the open interiors of the coils. Each coil has an opening in a first end portion thereof such that continuous strip material may pass into or out of the interior of the coil apparatus. The coil apparatus further comprises a pair of shunt conductors connecting the respective coils to each other. The shunt conductors are arranged on opposite sides of the openings in the end portions of the coils for providing a continuous current path from one rectangular coil to the adjacent coil. In one preferred embodiment there is an opening in the second end portion of one coil. Two more conductors, one on each side of this opening, provide connection to the respective poles of an alternating current power source.

Abstract: An inductor for inductively heating bearing surfaces of a crankshaft is machined from a block of copper to provide parallel, closely spaced and integrally joined inductor block portions having machined coolant passages therein. The machined inductor is rigidly supported between juxtaposed side plates having portions of the inner surfaces thereof machined to provide recesses which receive the inductor and in which the inductor is clampingly engaged between the plates. Positioning fingers are supported by the side plates to accurately position the active face of the inductor relative to a bearing surface to be heated, and tubular leads extend upwardly between the side plates for connecting the inductor across a source of power. An inlet conduit for coolant extends laterally between the side plates, and the tubular leads provide outlets for coolant flow from the inductor.

Abstract: An apparatus for the inductive cross-field heating of flat material includes a plurality of mutually opposite induction loops being disposed above and below the flat material. At least one pair of induction modules is formed of two induction modules being adjustable independently of one another in their position relative to the flat material. Each induction module has two mutually opposite U-shaped induction loops having geometries and dimensions which are invariable, base legs which can be positioned in such a way that they terminate at least a predeterminable distance in front of one edge of the flat material and within the width of the flat material, and two side legs which can be positioned in such a way that they project at least a predeterminable distance beyond the other edge of the flat material.

Abstract: A high frequency bolt heater is provided which can heat up the inside of a narrow hole much faster than a conventional bolt heater employing a resistance wire. The high frequency bolt heater includes an induction heating coil made of a copper tube bent in a hairpin fashion and whose shape is made approximately circular in section by pinching a magnet between opposed portions thereof. The heater can be inserted into a hole bored in the axial direction of a metallic bolt. A length of the coil is made approximately equal with that of the bored hole, and the magnet is omitted from a region of the heater which corresponds to a screw portion of the bolt for mounting a nut. An adjustable stopper made of a heat resistant electrical insulator is provided for setting a necessary length of the induction heating coil to be inserted into the hole, and a heat resistant insulator is provided on the surface of the induction heating coil.

Abstract: An induction coil for joining structural members by heating a bonding material disposed between the structural members. The induction coil includes first and second elements disposed in a non-parallel arrangement adjacent one surface and along one side edge of two juxtaposed structural members. In one embodiment, the first and second elements are joined together at adjacent ends. A base and a riser are connected to intermediate spaced ends of the first element for attaching the induction coil to a source of high frequency electrical current. The first and second elements, the base and the riser are formed of hollow, tubular members to form a coolant flow path therethrough.

Abstract: The invention relates to an inductor having two parallel main heating conductors which are interconnected at one of their ends via a bridge-shaped branch and are connected at their other end to a transformer, the connections also forming a bridge-shaped conductor branch. The characterizing feature of the invention is that disposed at least at one end of the parallel main heating conductors is a separate auxiliary inductor which is mounted displaceably in relation thereto and has two conductor portions parallel with the main heating conductors and inductively coupled thereto which are collectively interconnected at one of their axial ends via a bridge-shaped conductor branch determining the end of the heating zone and at the other end via a tunnel-shaped return conductor which over the whole displacement length is disposed beneath the bridge-shaped branch of the main heating conductors and is inductively coupled thereto.