Electric heater

Abstract

Electric heating device (1) for heating a cylindrical component, an injection molding nozzle, a hot runner of an injection molding tool or similar cylindrical component through which a plastic melt flows, wherein the electric heating device (1) has an electric heating element (2) which can be applied to the cylindrical component and has electrical connections (3) and a metal tube (4) which encloses the heating element (2), characterized in that the tube (4) consists of a body made of wire which is wound to form the tube (4).

Description

[0001] The invention relates to an electric heating device for heating a cylindrical component, an injection molding nozzle, a hot runner of an injection molding tool or similar cylindrical component through which a plastic melt flows, wherein the electric heating device has an electric heating element which can be applied to the cylindrical component and has electric connections and a metal tube which encloses the heating element in the desired position.

[0002] Heating devices for injection molding nozzles and similar cylindrical components through which a plastic melt is passed are widely known in the prior art. They consist of a heating element that is applied to the cylindrical component to heat the component and ensure a constant melt flow.

[0003] DE 691 10 858 T2 discloses a heated nozzle, the nozzle body having grooves into which a heating wire is inserted. A metal strip is wound around the heating wire and the nozzle body, which is used to press the heating wire into the grooves. The metal strip covering the heating wire is in contact with the outer surface of the heated nozzle body and is also welded, so that the heat from the heating wire is also transferred to the heated nozzle main body through the metal strip. This results in improved heat transfer properties of the nozzle, which are achieved by the two heat transfer systems.

[0004] US 4,150,281 A discloses a method in which a heating element is formed by arranging a pair of heating wires and a pair of thermocouple wires as well as a powdered mineral material in a metal shell, subjecting the material to repeated drawing and annealing processes, and then cutting the heating element to a desired length.

[0005] To attach a heating element to a component and ensure good contact between the component and the heating element, a tube is attached to the heating element. This tube encloses the heating element in the desired position, at least over its entire length, and clamps it firmly to the component. The tube thus prevents a coiled heating element, for example, from opening up or lifting off a nozzle, especially during its intended use, i.e., at elevated temperatures.

[0006] To connect the heating element to the tube, the heating element is first mounted on a calibration mandrel, which has an outer diameter that corresponds to the outer diameter of the component to be heated, such as a nozzle. The tube is pushed onto the heating element and pressed into place. The heating device can then be removed from the calibration mandrel and applied to the component to be heated.

[0007] The tube also reflects the heat emitted by the heating element toward the component, directing the heat into the component and reducing heat loss. The tubes used are typically made of stainless steel.

[0008] The use of such stainless steel pipes brings with it numerous disadvantages.

[0009] The components to be heated do not always have the same diameter, so heating devices with different diameters must be manufactured. This requires stainless steel pipes of different diameters, which must be kept in stock to ensure rapid production and delivery in the event of an order. This entails very high storage costs.

[0010] If a pipe with a required diameter isn't in stock, extremely long delivery times must be expected. Furthermore, large quantities of stainless steel pipes must be purchased, even if only small quantities are needed.

[0011] Due to these circumstances, the production of small quantities of heating devices can become disproportionately expensive and also take a very long time.

[0012] A further disadvantage is that the pipes have large tolerances in the inner diameter, which are caused by the manufacturing process.

[0013] In order to cut the pipes to the desired length, the corresponding sections are sawn to size, after which the pipes must be cleaned.

[0014] The object of the invention is to create a heating device that can be manufactured and provided particularly simply, quickly and inexpensively.

[0015] To solve the problem, the invention proposes that the tube consists of a body of wire that is wound into the tube.

[0016] The wire can be wound into a tube of the required diameter as needed, reducing storage costs, especially those previously incurred by large quantities of stainless steel tubes with a wide variety of diameters. This also eliminates dependence on delivery times, as the tubes can be custom-made from the wire as needed. The manufacturer is flexible and can produce quickly and cost-effectively. Even small quantities can be produced quickly and cost-effectively.

[0017] The inner diameter of the wound tube can be precisely matched to the dimensions of the heating element so that the tube sits optimally on the heating element in the desired position.

[0018] In addition, the wire can be easily cut once the required pipe length has been reached, eliminating the need for time-consuming cleaning of the pipe.

[0019] It is preferably provided that the heating device has a thermocouple with a flexible sheathed cable, wherein the sheathed cable is wound together with the wire to the pipe or at least to a pipe section of the pipe, wherein the sheathed cable has an outer sheath made of metal.

[0020] The thermocouple is, for example, a sheathed thermocouple. Such thermocouples are widely known in the state of the art, for example, as hotcontrol HPS 400 or hotcontrolTemp from Hotset GmbH. WIKA data sheet TE 65.46 also describes thermocouples that can be used, for example.

[0021] The sheathed cable of the thermocouple is flexible and consists of an outer sheath made of metal in which the inner conductors (thermocouple(s)) are embedded in a ceramic powder insulation.

[0022] The wire and the sheathed cable are wound together to form the pipe or pipe section, for example by winding them onto a calibration mandrel, with the wire and the sheathed cable being wound next to and parallel to each other to form the pipe or pipe section.

[0023] The sheathed cable of the thermocouple preferably has the same diameter as the wire, so that after winding together to form the pipe or pipe section, a flat pipe inner surface and pipe jacket surface are formed.

[0024] The sheathed cable can be wound together with the wire either over the entire length of the pipe or only over a section of the pipe.

[0025] In addition, it is preferably provided that the tube has a plurality of adjacent metal windings which are wound close together on the system.

[0026] When the wire is wound, a multitude of adjacent wire turns are created. If a thermocouple is incorporated into the tube or a section of tube, the wire turns and the turns of the sheathed cable are arranged alternately next to each other. The metal turns are in contact, so that the tube has a closed outer surface with no gaps between the individual turns. This ensures that the heating element is held evenly against the component to be heated, preferably over its entire length, and that it rests evenly against it, improving heat reflection toward the component to be heated.

[0027] It is preferably provided that a second metal winding of the sheathed cable is arranged alternately next to a first metal winding of the wire, wherein the alternating arrangement of the first and second metal windings is continued in an alternating sequence over the length of the pipe or the pipe section of the pipe.

[0028] This arrangement is achieved for the pipe or pipe section when the wire and the sheathed cable are wound side by side and parallel to each other on the pipe or pipe section. This allows the thermocouple to be integrated into the pipe or pipe section particularly easily.

[0029] It is also preferably provided that the adjacent metal windings are materially connected to one another.

[0030] The bonded connection is preferably achieved by welding the metal coils and ensures good pipe stability. Other bonded connection methods are also possible.

[0031] It is preferably provided that the metal windings are connected to one another by at least one, preferably at least three laser weld seams running parallel to the longitudinal axis of the tube and at least over part of the length of the tube.

[0032] Preferably, at least three weld seams are provided, arranged, for example, continuously along the entire length of the pipe. A different arrangement and number of weld seams can also be selected. Laser welding is a simple and cost-effective joining method.

[0033] Alternatively or additionally, it is preferably provided that the metal windings are integrally connected in the entire contact area in contact with one another.

[0034] This creates a particularly stable and seamless connection between the metal windings.

[0035] Preferably, the wire and / or the sheathed cable of the thermocouple has or have a circular, oval, polygonal, rectangular or square cross-section.

[0036] The wire cross-section can be selected based on the specific application. If a thermocouple is incorporated into the tube or a section of the tube, the wire and the sheathed cable preferably have the same cross-section to ensure the tube or section of tube has a uniform, flat inner and outer surface.

[0037] It can also preferably be provided that the wire is a hollow wire, wherein it is particularly preferably provided that the hollow wire has a filling.

[0038] For example, a liquid, solid, or gaseous filling can be incorporated into the wire. It is particularly advantageous to fill the hollow wire with a heat-insulating filling to achieve better insulation.

[0039] Preferably, the wire is made of X6Cr17 or NiCo29-18.

[0040] These materials have a particularly low coefficient of expansion, which ensures that the tube sits firmly and securely on the heating element, and thus the entire heating device, on the component to be heated, even at higher temperatures.

[0041] It is preferably provided that the heating element is fixed in the pipe, preferably by means of a material bond.

[0042] If necessary, the heating element can be attached to the tube, for example by soldering.

[0043] It is also preferably provided that the tube has at least one cutout through which the electrical connections of the heating element are passed.

[0044] Depending on the arrangement of the heating element's connections, the cutout can be located centrally in the pipe or at an end of the pipe. Preferably, the metal coils severed by the cutout are connected, for example, by welding or other joining techniques or means in the area adjacent to the cutout.

[0045] In addition, it is preferably provided that the pipe consists of at least two pipe sections, wherein a first pipe section consists of a first wire and at least one further pipe section adjoining the first pipe section consists of a further wire, wherein the first wire and the further wire consist of different materials with different heat-dividing capabilities.

[0046] A first section of the pipe is wound from a first wire and cut when the desired section length is reached. A second wire is connected at the cut point for another section of the pipe and wound into another section. This process can be repeated as often as required, creating a pipe with multiple sections of different insulating properties.

[0047] In addition to the heating device, the invention also relates to a method for producing an electric heating device described above. All parts of the above description that relate to the heating device apply equally to the following method and the heating device used therein. All statements below regarding the heating device and its manufacturing methods that have not yet been described in connection with the heating device are to be considered supplementary to the above description and apply accordingly to the heating device.

[0048] The invention thus relates to a method for producing a heating device, according to claims 1 to 14, for electrically heating a cylindrical component, an injection molding nozzle, a hot runner or similar cylindrical component through which a plastic melt is passed, wherein the heating device has an electrical heating element with electrical connections which is sheathed with a metal tube, wherein the heating device is applied to the cylindrical component and heats it.

[0049] The statements on the state of the art and the disadvantages refer equally to the process.

[0050] The object of the invention is therefore to provide a method for producing an electric heating device which can be carried out particularly simply, quickly and cost-effectively in order to provide an equally cost-effective heating device.

[0051] To achieve the object, the invention proposes that a wire is wound into the tube, wherein the tube has a plurality of metal windings and the wire tube is applied to the heating element.

[0052] This can be achieved, for example, by winding the wire onto a calibration mandrel that has the diameter required for the application. After the wire is wound into the tube, the tube is pulled onto the heating element, and the heating device can be attached to the component to be heated.

[0053] Preferably, it is provided that a thermocouple, which has a flexible sheathed cable, is wound together with the wire to the pipe or at least to a pipe section of the pipe, wherein the sheathed cable has an outer sheath made of metal.

[0054] For this purpose, the wire and the sheathed cable are wound together onto the calibration mandrel, with the wire and the sheathed cable being wound next to each other and parallel to each other to form the pipe or a pipe section.

[0055] It is also preferably provided that the metal windings of the wound wire and / or the wound sheathed cable touch each other.

[0056] The wire and / or the sheathed cable are wound tightly together to create a closed tube surface that is particularly stable and reflects the heat emanating from the heating element without significant heat loss.

[0057] It is preferably provided that first metal windings of the wire and second metal windings of the thermocouple are arranged alternately next to one another over the length of the pipe or the pipe section of the pipe.

[0058] In addition, it is preferably provided that the metal windings are connected to one another in a materially bonded manner.

[0059] It is preferably provided that the metal windings are connected during winding in the entire contact area that touches each other, preferably in a materially bonded manner.

[0060] To achieve this, the metal coils are joined, preferably welded, during the winding process to form the pipe or pipe section. This creates a particularly tight and gap-free pipe body.

[0061] It can also preferably be provided that the heating element is fixed in the pipe.

[0062] It is particularly preferred that the tube is wound with an undersize compared to the outer diameter of the heating element and is then pulled onto the heating element.

[0063] The undersized tube is first drawn onto the heating element along its entire axis. This is achieved, for example, by rotating or screwing the tube. The coils are then firmly bonded together along the tube axis. By manufacturing the tube undersized, the tube sits in the desired position on the heating element with tension, improving contact between the heating element and the component. The tube can also be pressed onto the heating element to ensure a secure fit.

[0064] Furthermore, it is preferably provided that a first pipe section made of a first wire and at least one further pipe section made of a further wire are wound to form the pipe, wherein the first wire and the further wire consist of different materials with different heat dissipation capabilities.

[0065] Various embodiments of the electric heating device according to the invention are shown in the drawings and described in more detail below.

[0066] It shows: Fig. 1 shows an electric heating device with a coiled heating element and a tube wound from wire; Fig. 2 an electric heating device with a heat conducting body into which a heating element is pressed and a tube wound from wire in view; Fig. 3 an electric heating device with a coiled heating element and a tube wound from a wire and a sheathed cable in view.

[0067] The figures show an electric heating device 1 for heating a cylindrical component, an injection molding nozzle, a hot runner of an injection molding tool, or a similar cylindrical component through which a plastic melt flows. The electric heating device 1 comprises an electric heating element 2 with electrical connections 3 that can be applied to the cylindrical component, as well as a metal tube 4 that encloses the heating element 2.

[0068] Heating elements 2 are described many times in the prior art. In Fig. 1 shows a heating device 1 with a coiled heating element 2. Alternatively, Fig. 2 shows a heating device 1 in which a heating element 2 is pressed into a groove of a heat-conducting body 11. In order to be able to be applied to a corresponding cylindrical component, the heating elements 2 have a cylindrical through-opening 12.

[0069] The pipe 4, which is in the Fig. 1 and Fig. 2, consists of a wire body, with the wire wound into a tube 4. Depending on requirements and application, the wire can be wound into tubes 4 of the required diameter. This allows, in particular, the storage costs previously incurred due to the large quantities of stainless steel tubes with a wide variety of diameters to be reduced. The dependence on delivery times is also eliminated, as the tubes 4 can be individually manufactured from the wire as needed.

[0070] The disadvantage of the large tolerances that arise from the manufacturing process for stainless steel pipes does not exist with the wound pipe 4 made of wire either, since the inner diameter can be precisely matched to the dimensions of the heating element 2 and maintained so that the pipe 4 sits optimally on the heating element 2 in the desired position.

[0071] There is also no need for cleaning work after sawing the stainless steel pipes to the desired length, since the wire is only cut when the final length of the pipe 4 is reached.

[0072] Fig. Figure 3 shows a heating device 1 comprising a thermocouple 5 with a flexible sheathed cable 6. The outer tube of the sheathed cable is made of metal. The sheathed cable 6 is wound together with the wire to form the tube 4. This is achieved, for example, by winding the wire and the sheathed cable 6 onto a calibration mandrel, with the wire and the sheathed cable 6 being wound side by side and parallel to each other to form the tube 4. The wire and the sheathed cable 6 have the same round cross-section, so that the inner and outer surfaces of the tube are flat and without any interfering protrusions.

[0073] The tubes 4 shown in the figures have a plurality of adjacent metal windings 7, 8, which are wound tightly together on the system. The tube 4, which is Fig. 1 and Fig. 2, has only wire windings 7. The Fig. The tube 4 shown in Fig. 3 has first metal windings 7 (wire windings) and second metal windings 8 (sheathed cable) which are arranged alternately next to one another.

[0074] The metal windings 7, 8 are in contact, so that the tube 4 has a closed outer surface without gaps between the individual windings 7, 8. In the desired position, the tube 4 encloses at least the entire heating element 2, so that the heating element 2 is preferably held evenly over its entire length against the component to be heated and lies evenly against it. The closed outer surface of the tube 4 also improves the reflection of heat through the tube 4 toward the component to be heated.

[0075] The metal coils 7, 8 are connected to each other by three laser welds 9 running along the entire length of the tube to ensure that the tube 4 is stable and retains its shape. Only two of the three welds 9 are visible in the figures. The welds 9 are evenly spaced on the outer surface of the tube 4 and run parallel to the longitudinal axis of the tube 4.

[0076] The wire is made of a material with a particularly low coefficient of expansion, ensuring a firm and secure fit of the tube 4 on the heating element 2, and thus of the entire heating device 1 on the component to be heated, even when the temperature increases. Materials such as X6Cr17 or NiCo29-18 are particularly suitable.

[0077] The heating element 2 is firmly fixed in the tube 4 by a soldered connection.

[0078] At one end of the tubes, a cutout 10 is provided through which the electrical connections 3 of the heating element 2 are routed. The metal coils 7, 8 are severed in the area of ​​the cutout 10. To secure the position of the metal coils 7, 8, they are connected by an additional weld seam 14 in the area adjacent to the cutout 10.

[0079] The invention is not limited to the embodiments, but is variable in many ways within the scope of the disclosure.

Claims

[1] Electric heating device (1) for heating a cylindrical component, an injection molding nozzle, a hot runner of an injection molding tool or similar cylindrical component through which a plastic melt flows, wherein the electric heating device (1) has an electric heating element (2) which can be applied to the cylindrical component and has electrical connections (3) and a metal tube (4) which encloses the heating element (2), characterized by that the tube (4) consists of a body of wire which is wound into the tube (4). [2] Heating device according to claim 1, characterized by in that the heating device (1) has a thermocouple (5) with a flexible sheathed cable (6), wherein the sheathed cable (6) is wound together with the wire to the pipe (4) or at least to a pipe section of the pipe (4), wherein the sheathed cable (6) has an outer sheath made of metal. [3] Heating device according to claim 1 or 2, characterized bythat the tube (4) has a plurality of adjacent metal windings (7,8) which are wound close together on the system. [4] Heating device according to claim 2 or 3, characterized by that a second metal winding (8) of the sheathed cable (6) is arranged alternately next to a first metal winding (7) of the wire, wherein the alternating arrangement of the first and second metal windings (7, 8) is continued in alternating sequence over the length of the pipe (4) or the pipe section of the pipe (4). [5] Heating device according to claim 3 or 4, characterized by that the adjacent metal windings (7,8) are firmly connected to each other. [6] Heating device according to one of claims 3 to 5, characterized by that the metal windings (7,8) are connected to one another by at least one, preferably at least three laser weld seams (9) running parallel to the longitudinal axis of the tube (4) and at least over part of the length of the tube (4). [7] Heating device according to one of claims 3 to 6, characterized by that the metal windings (7,8) are firmly connected in the entire contact area. [8] Heating device according to one of claims 1 to 7, characterized by that the wire and / or the sheathed cable (6) of the thermocouple (5) has or have a circular, oval, polygonal, rectangular or square cross-section. [9] Heating device according to one of claims 1 to 8, characterized by that the wire is a hollow wire. [10] Heating device according to claim 9, characterized by that the hollow wire has a thermally insulating filling. [11] Heating device according to one of claims 1 to 10, characterized by that the wire is made of X6Cr17 or NiCo29-18. [12] Heating device according to one of claims 1 to 11, characterized by that the heating element (2) is fixed in the pipe (4), preferably by means of a material bond. [13] Heating device according to one of claims 1 to 12, characterized by that the tube (4) has at least one cutout (10) through which the electrical connections (3) of the heating element (2) are passed. [14] Heating device according to one of claims 1 to 13, characterized by that the pipe (4) consists of at least two pipe sections, wherein a first pipe section consists of a first wire and at least one further pipe section adjoining the first pipe section consists of a further wire, wherein the first wire and the further wire consist of different materials with different heat-dividing capabilities. [15] Method for producing a heating device (1) according to claims 1 to 14 for electrically heating a cylindrical component, an injection molding nozzle, a hot runner or similar cylindrical component through which a plastic melt is passed, wherein the heating device (1) has an electrical heating element (2) with electrical connections (3) which is encased in a tube (4) made of metal, wherein the heating device (1) is applied to the cylindrical component and heats it, characterized by that a wire is wound onto the tube (4), the tube (4) having a plurality of metal windings (7, 8) and the wire tube is applied to the heating element (2). [16] Method according to claim 15, characterized bythat a thermocouple (5) having a flexible sheathed cable (6) is wound together with the wire to the tube (4) or at least to a tube section of the tube (4), wherein the sheathed cable (6) has an outer sheath made of metal. [17] Method according to claim 15 or 16, characterized by that the metal windings (7,8) of the wound wire and / or the wound sheathed cable (6) touch each other. [18] Method according to claim 16 or 17, characterized by that first metal windings (7) of the wire and second metal windings (8) of the thermocouple (5) are arranged alternately next to one another over the length of the tube (4) or the tube section of the tube (4). [19] Method according to one of claims 15 to 18, characterized by that the metal windings (7,8) are firmly connected to each other. [20] Method according to one of claims 15 to 19, characterized bythat the metal windings (7,8) are connected during winding in the entire contact area that touches each other, preferably by a material bond. [21] Method according to one of claims 15 to 20, characterized by that the heating element (2) is fixed in the pipe (4). [22] Method according to one of claims 15 to 21, characterized by that the tube (4) is wound with an undersize compared to the outer diameter of the heating element (2) and is then pulled onto the heating element (2). [23] Method according to one of claims 15 to 22, characterized by that a first pipe section made of a first wire and at least one further pipe section made of a further wire are wound to form the pipe, wherein the first wire and the further wire consist of different materials with different heat dissipation capabilities.

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