METHOD FOR PRODUCING A HELICAL BODY

Abstract

A method for producing a hollow, helical, electrically conducting body. The method comprising: producing a helical core made of a core material that can be at least one of liquefied and evaporated under the action of heat; coating the helical core with a first powder layer of an at least partially electrically conducting powder using a powder coating method; heating the helical core and the first powder layer to a first temperature, at which the helical core is at least one of liquefied and evaporated and at which the first powder layer is at least partially solidified in porous form, the core material exiting space surrounded by the first powder layer; and after the core material has exited the space surrounded by the first powder layer, sintering the first powder layer by heating the first powder layer to a second temperature, which is higher than the first temperature.

Claims

1.-17. (canceled)

18. A method for producing a hollow, helical, electrically conducting body, the method comprising: producing a helical core made of a core material that can be at least one of liquefied and evaporated under the action of heat; coating the helical core with a first powder layer of an at least partially electrically conducting powder using a powder coating method; heating the helical core and the first powder layer to a first temperature, at which the helical core is at least one of liquefied and converted into a gaseous state and at which the first powder layer is at least partially solidified in porous form, the core material exiting space surrounded by the first powder layer; and after the core material has exited the space surrounded by the first powder layer, sintering the first powder layer by heating the first powder layer to a second temperature, which is higher than the first temperature.

19. The method of claim 18, wherein after heating the helical core and the first powder layer to the first temperature, the first powder layer is solidified and remains porous, such that the core material that is at least one of liquefied and evaporated escapes through the solidified first powder layer.

20. The method of claim 18, wherein after the sintering of the first powder layer at the second temperature, the first powder layer is compacted to become impermeable to liquids and gases.

21. The method of claim 18, wherein the first powder layer is formed in the form of multiple consecutively applied sub-layers of the powder.

22. The method of claim 18, comprising at least one second powder layer of a second powder applied to the first powder layer, prior to or after heating the helical core and the first powder layer to the first temperature.

23. The method of claim 22, wherein the second powder is made of an electrically insulating material and forms an insulating layer after one or more of heating at the first temperature and heating at the second temperature.

24. The method of claim 18, wherein the powder coating method includes one or more of spraying, dipping and using a fluidizing powder bed.

25. The method of claim 18, wherein the powder coating method includes one or more of a powder slurry and a powder feedstock.

26. The method of claim 18, wherein the helical core is produced in one or more of a casting process and a foaming process, such that the helical core is assembled from multiple parts.

27. The method of claim 26, wherein the helical core is produced as a blank, and thereafter is brought into the shape of a helix by creating a helical recess.

28. The method of claim 27, wherein the helical recess is created in the helical core using a tool that rotates about an axis extending through the helical core and, at the same time, is steadily advanced along the axis.

29. The method of claim 18, comprising at least one interruption in powder coating of the first powder layer or a second powder layer to create an opening for a cavity defined by the helical core, the cavity being delimited by the powder coating.

30. A helical body, comprising a cavity and being produced by the method of claim

18.

31. The helical body of claim 30, wherein the cavity is designed as a fluid channel and includes at least one opening.

32. The helical body of claim 30, wherein outer dimensions of the helical body are between 3 cm and 1 m in each spatial direction.

33. The helical body of claim 30, wherein a wall thickness of a material surrounding the cavity is between 1 mm and 20 mm.

34. The helical body of claim 30, wherein a cross-section of the cavity designed as a fluid channel is one of polygonal and elliptical and has a cross-sectional surface area of between 10 mm.sup.2 and 50 cm.sup.2.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The disclosure will be shown and described hereafter based on exemplary embodiments in figures of a drawing. In the drawings:

[0039] FIG. 1 shows a perspective view of a helical body/a coil, according to embodiments of the disclosure;

[0040] FIG. 2 shows a winding of a coil/of a helical body in a cross-sectional view, according to embodiments of the disclosure;

[0041] FIG. 3 shows a helix of a further helical body in a cross-sectional view, according to embodiments of the disclosure;

[0042] FIG. 4 shows, in a schematically enlarged form, the powder-coated surface of a helical body in a cross-sectional view, according to embodiments of the disclosure;

[0043] FIG. 5 shows a device for producing a helical core, and a core into which a recess has been partially introduced, according to embodiments of the disclosure;

[0044] FIG. 6 shows a view of a part of a helical body, comprising a power connection and/or a fluid connection, according to embodiments of the disclosure;

[0045] FIG. 8 shows a view of a part of a helical body, comprising a power connection and/or a fluid connection, according to embodiments of the disclosure;

[0046] FIG. 9 shows a view of a part of a helical body, comprising a power connection and/or a fluid connection, according to embodiments of the disclosure; and

[0047] FIG. 10 shows a view of a part of a helical body, comprising a power connection and/or a fluid connection, according to embodiments of the disclosure.

DETAILED DESCRIPTION

[0048] FIG. 1 shows a perspective illustration of an electrically conducting coil 1, serving as a helical body, which is formed by a helical, insulated, strand-shaped electrical conductor 2. The illustration of FIG. 1 shows a coil having a quadrangular, and in particular square, cross-section, wherein the conductor forming the coil itself likewise has a rectangular cross-section. The different helix layers of the conductor are rectangular and placed on top of one another at small distances.

[0049] The helical body has outer dimensions that correspond to a cuboid, having a rectangular (square) base surface area ab, and a height h, along which the cavity extends. The body, however, can also have a different base surface area and/or be tapered in the direction of the height thereof, for example, so as to have the shape of a frustrum of a cone or of a frustrum of a pyramid, for example. The outer dimensions a, b and h are between 3 cm and 1 m in each case.

[0050] FIG. 2, by way of example, shows the cross-section of an insulated conductor, which can be used, for example, to produce a coil, as it is shown in FIG. 1. In FIG. 2, the hollow outer portion formed of a sintered powder is denoted by reference numeral 3, and the core 4 is shown within the powder coating 3, which is made of a foam material, and in particular EPS, for example. The configuration shown in FIG. 2 results, for example, directly after the helical body 4 has been coated with a first powder 3. The powder 3 is designed to be at least partially electrically conducting, and is made of an electrically conducting material, for example a metal or a metal alloy. It can also be made of a mixture of two or more powders, which are preferably all electrically conducting.

[0051] In the shown configuration, the coated core 4 can be heated to a temperature below the melting temperature of the first powder, wherein the material of the core 4 either evaporates or liquefies. The material of the core can then escape at one end of the layer/coating, or through the coating itself, so that only the coating remains, which is sintered at the same time and thereby solidified. The sintering process is usually controlled in such a way that, in a first phase of the sintering process, when the first powder layer 3 is still permeable to gas or fluid, the core is liquefied or rendered gaseous and thereby, for example, is also able to exit through the coating 3/powder layer 3.

[0052] After the material of the core 4 has exited, the sintering process can be continued, either by maintaining the temperature at a stable level for an additional period of time, or by slightly raising the temperature, so that the sintering process progresses further. This can be continued until the first powder layer has been densified, thereby having become impermeable to gas/fluid. The sintering process can be carried out in an inert gas atmosphere, for example.

[0053] The cavity defined by the core 4 then forms a fluid channel, which emerges at the opposite ends of the coil in the example. A cross-sectional surface area pq of the fluid channel, which is rectangular in the present example, is between 10 mm.sup.2 and 50 cm.sup.2, for example. Side lengths p and q of the cross-sectional surface area of the channel can be several millimeters to several centimeters in examples, corresponding to the cross-sectional surface area. A wall thickness w of the material surrounding the cavity, which comprises the first powder layer, can be between 1 mm and 20 mm, for example.

[0054] As an alternative or in addition, in embodiments, it is also possible to provide openings of the fluid channel that are not located at ends of the helical body, but, for example, laterally at the windings. The fluid channel can have a constant or a variable cross-section across the length thereof.

[0055] FIG. 3 shows a configuration including a core 4 having a round cross-section, which is surrounded by a first powder layer 3 and an outer second powder layer 5. The first powder layer 3 is composed of an electrically conducting powder, for example a metal powder, while the second powder layer 5, which surrounds the first powder layer 3, is made of or produced from an electrically insulating material, such as a sinterable ceramic powder or any other sinterable electrically insulating powder.

[0056] During the joint sintering of the first and second powder layers, two hard self-supporting layers are created, wherein the inner layer 3 is electrically conducting and forms the conductor of the helical body, and the outer layer 5 forms an outer insulation for the conductor 3. The powder layers 3 and 5 can also be applied and sintered consecutively. Since powder coating by way of conventional powder coating processes, such as dipping or spraying, requires very little space, it is also possible for windings of the coil that are located very close together, as shown in FIG. 1, to be evenly coated with a powder layer, which is then solidified by way of sintering. As a result, a helical electrically conducting body having little space requirement and little clearance between the individual windings, and optionally also including an insulation, can be easily produced. A coil or a spring can be produced using such a helical body, with optimal space utilization.

[0057] A cross-sectional surface area of the core 4 or fluid channel, which is round in the present case, has the radius r, which is between 5 mm and 5 cm, for example. As an alternative or in addition, the surface area can be between 10 mm.sup.2 and 50 cm.sup.2, for example. A wall thickness w of the material surrounding the cavity, which comprises the first and second powder layers, can be between 1 mm and 20 mm, for example.

[0058] FIG. 4, in an enlarged schematic illustration, shows a first powder layer 3 and a core 4, wherein individual grains of the powder layer are distinguishable. The material of the core is evaporated or liquefied, and can pass through the pores of the first powder layer 3 according to the arrows 6, 7, as long as the material of the first powder layer has not yet been sintered to a fluid-tight state.

[0059] FIG. 5 shows a hollow cylinder 8, which serves as a blank for producing the core. This blank 8 can be made of a foam material, for example, but can also be made of a wax or a similarly meltable material. The cylinder 8 has a cylindrical cavity 9 so as to be designed in the overall as a hollow cylinder having a hollow cylinder wall 10. The longitudinal axis of the hollow cylinder is denoted by reference numeral 11.

[0060] A device for introducing a helical recess into the hollow cylinder 8 is shown beneath the hollow cylinder 8, which comprises a vertically arranged shaft 12 that is mounted rotatably about the longitudinal axis thereof on a holder 17. A tool 13 is arranged on the shaft 12, which projects perpendicularly from the shaft 12. The tool 13 is connected to the shaft 12 by means of a vibratory or saw drive 14. This drive 14 can effectuate an oscillating movement of the tool 13 in the direction of the double arrow 15. Instead of a vibratory drive 14, it is also possible for a heater for the tool 13 to be provided.

[0061] When the shaft 12 is driven rotatably, the tool 13 moves on a circular track about the axis 11, dividing the hollow cylinder 8 when the tool creates a path for itself through the cylinder wall 10. This may take place, for example, by a rasping or sawing motion, provided the tool 13 includes teeth. It is also possible for a heater of the tool 13 to be provided, for heating the tool so as to melt the material of the hollow cylinder 8. Simultaneously with the rotational movement about the axis 11, an axial advancement of the tool 13 in the direction of the axis 11 is provided, which takes place, for example, at a constant speed. The advancement speed, however, can also be changed to create different sections having different pitches. By combining the rotational and advancement movement of the tool 13, a helical recess 16 is introduced into the hollow cylinder 8. The portion of the hollow cylinder 8 that remains between the individual turns of the continuous recess 16 likewise has the shape of a helix. This body can be used as the core for the helical body to be produced, and can later be covered with a first powder layer. After the first powder layer has been sintered and the core material removed, a hollow, helical electrically conducting body in the shape of a coil arises.

[0062] FIG. 6 shows an end section of a hollow helical body 1 in a perspective representation. The helical body can have the shape of a spiral, having a diameter that decreases or increases from winding to winding of the helix, but may also have the shape of a screw having a constant diameter. At one end or both ends, the helical body 1 comprises a fitting 20, which takes on the shape of a sleeve, and in particular a cylindrical sleeve. The sleeve 20 can be made of a metal, for example iron, steel, stainless steel, copper or brass. The sleeve 20 can also include a metallic connecting lug 21 for establishing an electrically conducting connection.

[0063] FIG. 7 shows that, in the case of the production method, the core 4 is connected to the fitting 20, and thereafter both are jointly coated with a powder layer 3, 3. This is indicated by the arrows 22.

[0064] FIG. 8 shows that, when the core 4 is connected to the device 20, the core 4 can end at the device, and this may be attached to the core.

[0065] FIG. 9 shows that the core 4 can also extend into a through-opening 20a of the device. For this purpose, the core 4 can be cast onto and into the device 20 during the production thereof.

[0066] FIGS. 8 and 9 show that the coating 23 is applied both to the core 4 and to the sleeve 20, so that the sleeve 20, without further measures, is connected to the portions of the helical body 1 that are formed by the coating 23, after the core has been removed. Such a connection can be provided at both ends of the body 1.

[0067] In addition to an electrical connection, the sleeve(s) 20 can also form a fitting for the connection of a fluid line for cooling. For this purpose, the sleeve can also include a screw thread 24 (see FIG. 10) and/or a bayonet catch and/or a seal and/or a sealing seat.

[0068] Using the disclosure, a hollow helical body having a low space requirement and high space utilization can be created, which can be used very efficiently as an electric coil due to the option of internal cooling.