Metal spool

Abstract

The invention specifies a metal spool for receiving metallic winding material (5) in the form of a wire, which spool comprises two flanges (1, 2) in the form of circular disks, arranged parallel to one another and having the same diameter and an elongate core (3) connecting the flanges and having a circular cross section and smaller radial dimensions in comparison with the flanges (1, 2), the mid-axis of which core corresponds to the mid-axes of the flanges (1, 2). A winding space (4) for receiving the winding material (5), is delimited by the core (3) and the two flanges (1, 2). The dimensions of the winding space (4) in the direction of the mid-axis of the spool can be enlarged at an increased temperature. In addition, means are provided to bring the dimensions of the winding space (4) back to the initial position when the temperature returns to room temperature.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 USC §119(a) to German Patent Application No. DE102005060279.7 which was filed on Dec. 16, 2005.

TECHNICAL FIELD

The invention relates to a metal spool for receiving metallic winding material in the form of a wire, comprising two flanges in the form of circular disks, arranged parallel to one another and having the same diameter and an elongate core connecting these flanges and having a circular cross section and smaller radial dimensions in comparison with the flanges, the mid-axis of which core corresponds to the mid-axes of the flanges, in which spool a winding space for receiving the winding material is delimited by the core and the two flanges, and in which spool the distance between the flanges can be altered elastically by forces acting on them (DE 41 38 189 A1).

BACKGROUND OF THE INVENTION

These spools have long been known and available on the market. In the known technology, they are used for winding up metallic wires which are envisaged, in particular, as structural elements of electrical cables and lines. Spools in which the distance between the flanges can be altered are known. For example, DE 41 38 189 A1, mentioned at the outset, describes a spool in which transverse stresses occurring when spooling wire which is subjected to temperature are intended to be compensated for in a controlled manner. For this purpose, the flanges are arranged on the core such that they can move in the axial direction. Once the spooling has come to an end, the spool has its rated dimension owing to the displacement of the flanges towards the outside. DE 33 12 178 A1 describes a spool having a core comprising two parts, of which in each case one is attached to one flange. The parts of the core engage telescopically one inside the other and can be connected to one another by being latched in different relative positions for the purpose of setting different core lengths. A similar spool having a core comprising two parts is described in U.S. Pat. No. 3,840,198 A, in which the flanges are connected to one another via spring elements.

In order to set specific properties for wires which are intended to be used in cables and lines as electrical conductors, it is necessary for them to be pretreated. In this case, the wires are provided with predetermined diameters by means of mechanical processing and, for example, bending properties which can be set in a targeted manner by thermal treatment. The thermal treatment takes place, for example, using so-called “annealing spools” consisting of metal, in particular of steel, onto which the wires are wound and, in the wound-on state, are subjected to an annealing treatment together with the spools. The required mechanical and electrical properties of the wires can thus be set with a sufficient degree of accuracy. However, problems often occur when withdrawing the wires, which have cooled down again after the annealing, from the spools since the wires can be “caked” to one another by the annealing process.

The reason for this fact is essentially that the material of the wires provided for electrical applications expands to a greater extent on heating than the material of a spool consisting of a metal having a high tensile strength, in particular of steel. This applies, on the one hand, to copper, but in particular to aluminum, as the conductor material for the wires. In comparison with steel, aluminum has a coefficient of thermal expansion which is greater by a factor of approximately 2, while this factor is approximately 1.4 for copper in comparison with steel. The expansion of a wire which has been wound onto the spool with a large number of turns during heating in the annealing process is then drastically impeded by the respective spool. As a result, the turns of the wire not only push against the flanges of the spool, but they are also pushed against one another with a considerable amount of force. This results in the abovementioned caking of the wire turns.

SUMMARY OF THE INVENTION

The invention is based on the object of designing the spool outlined at the outset such that caking of the wires during an annealing process can be ruled out with a high degree of reliability.

This object is achieved in accordance with the invention by virtue of the fact that

• • the dimensions of the winding space in the direction of the mid-axis of the spool can be enlarged at an increased temperature, in particular up to an annealing temperature required for annealing the winding material, in comparison with an initial position at room temperature by forces which are brought about by different coefficients of thermal expansion of the winding material, on the one hand, and of the core of the spool, on the other hand, and
  • means are provided which can be used to bring the dimensions of the winding space back to the initial position when the temperature returns to room temperature.

When using the spool according to the invention, caking of the turns of a wire wound onto said spool can be ruled out with a high degree of reliability. The core of the spool can, for example, itself be designed to be so elastic that, as a result of the heating during an annealing process, it is extended reversibly owing to the pressure exerted, for example, on the flanges of the spool when the wire turns expand. The individual wire turns can expand relatively unimpeded, however, in all embodiments of the spool during the annealing process owing to the expansion of the winding space, and the pressure exerted on these wire turns is as a result considerably reduced. The corresponding “extension distance” of the winding space is dependent on the level of the annealing temperature, of the coefficient of thermal expansion of the material for the wire wound on and of the size of the spool. It is, for example, between 2 mm and 10 mm.

The elasticity of the core existing in the axial direction can be achieved by spring elements acting in the axial direction being incorporated, but with particular advantage owing to the use of a tube as the core, which tube is corrugated all the way around at least in an axial section transversely with respect to its axis, preferably over its entire length.

Caking of the wire turns during an annealing process can also be ruled out with a high degree of reliability in another embodiment of the spool when the material of said spool has a coefficient of thermal expansion which corresponds at least approximately to that of the material for the wire wound onto the spool.

Exemplary embodiments of the subject matter of the invention are illustrated in the drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a view of a spool known in principle.

FIGS. 2 to 6 show different embodiments of the core of a spool according to the invention.

FIG. 7 shows a further embodiment of the spool according to the invention.

FIG. 8 shows a section through FIG. 7 along the line VIII-VIII.

FIG. 9 shows a detail of the spool shown in FIG. 7 in an enlarged illustration.

FIG. 10 shows a further embodiment of the spool.

FIG. 11 is a graph of the displacement travel of the flanges over the length of the core at different temperatures.

DETAILED DESCRIPTION

The spool illustrated in FIG. 1 has two flanges 1 and 2 in the form of circular disks and having the same diameter. The flanges 1 and 2 consist of a metal having a high tensile strength, in particular of steel. They are arranged parallel to one another in the spool and are connected to one another by a core 3, which likewise consists of metal and, in the exemplary embodiment illustrated, is cylindrical. The elongate core 3 could also be conical. The mid-axes of the flanges 1 and 2 and the core 3 correspond to one another. A winding space 4 serving the purpose of receiving the winding material is delimited by the flanges 1 and 2 and the core 3.

The spool according to the invention consists of metal and is used for receiving winding material in the form of wire, which is wound on with a large number of turns and likewise consists of metal—referred to below as “wire” for short. The upper part of FIG. 1 shows a large number of turns 5 of a wire. Its material should have a markedly greater coefficient of thermal expansion than the material for the flanges 1 and 2 and, in a preferred embodiment, also for the core 3. All parts of the spool therefore preferably consist of steel, and the wire is preferably a copper-cladded aluminum wire—referred to below as “CCA wire”, for short. The invention is naturally not restricted to the use of these materials. However, they are taken into consideration in the description below.

A spool which has been fully wound with CCA wire is introduced into an annealing furnace for an annealing treatment of the CCA wire and is heated there, for example, to temperatures of between 400° C. and 600° C. In the process, the turns 5 of the CCA wire expand to a greater extent than the spool or its core 3. In order that, as a result, the turns 5 of the CCA wire are not pressed too firmly against one another, the distance between the flanges 1 and 2, for example, can be extended elastically or reversibly such that the winding space 4 can be altered in the direction of the mid-axis of the spool.

The displacement travel of the flanges 1 and 2 at an increased temperature or the expansion of the winding space 4 can be calculated, starting from a length at room temperature and subsequent return to the initial position at room temperature. The elements required for the reversible change in length can then have corresponding dimensions. The displacement travel of the flanges 1 and 2 and therefore the change in length of the winding space 4 between room temperature and the increased temperature is equal to a length el in accordance with the following equation
el=l_o1×Δδ(α_w−α_c),
in which:
l_o1=length of the core at room temperature
Δδ=difference between the room temperature and the maximum temperature
α_w=coefficient of thermal expansion of the material for the winding material
α_c=coefficient of thermal expansion of the material for the core.

The dependence of the length el of the “displacement travel” on the level of the annealing temperature is shown, for example, in FIG. 11 for an aluminum wire which has been wound onto a steel spool. A core having a length of 1000 mm is accordingly extended at a temperature of 200° C. by 2 mm, while the extension at 400° C. is approximately 4.8 mm, i.e. more than double that at 200° C. This effect is even more serious at a core length of 2000 mm. Here, the extension at 200° C. is approximately 3.8 mm and 9.5 mm at 400° C. The respective extension of the core, which is reversed when the wound spool is cooled to room temperature, is necessary, as mentioned above, in order that the wire turns do not cake to one another during annealing and subsequent cooling. The expansion of the flanges 1 and 2, which likewise occurs at increased temperature, is so low in relation to the extension of the core that it is negligible.

The reversible enlargement of the winding space 4 between the two flanges 1 and 2 in the axial direction of the core 3 can be achieved in a different way:

As shown in FIG. 2, the core 3 may be in the form of a tube 6, which is corrugated all the way round transversely with respect to its axis over its entire axial length. Since the core 3 is fixedly connected to the two flanges 1 and 2, it is expanded by the turns 5 of the CCA wire which are expanding and pressing against the flanges 1 and 2, with the result that the clear width of the winding space 4 is increased. When the spool and the CCA wire are cooled, the core 3 returns to its original length.

The same effect can be achieved when the core shown in FIG. 3 is in the form of a tube 7, which is corrugated all the way round transversely with respect to its axis at least in an axial section.

In the embodiment of the spool shown in FIG. 4, the core 3 is fixedly connected to the flange 1 and connected to the flange 2 via a spring mechanism 8. Such a spring mechanism, however, can also be provided in each case between the two flanges 1 and 2 and the core.

As shown in FIG. 5, the core can also comprise two tubes 9 and 10, which engage telescopically one inside the other, bear against one another such that they can move in relation to one another and are connected to one another via a spring mechanism 11. The tube 9 is only fixedly connected to the flange 1, while the tube 10 is fixed to the flange 2.

In one further embodiment of the spool according to the invention, the core can also be designed such that there are no substantial measures for elastically changing its length. As shown in FIG. 6, the core 12 may consist of aluminum and therefore substantially of the same material as the CCA wire. It therefore has at least approximately the same coefficient of thermal expansion as the CCA wire, with the result that the expression in parentheses in the above equation in the extreme case is equal to zero. With this design of the spool as well, no substantial pressure is applied to the turns 5 of the wire. This embodiment of the spool is generally designed such that the material of the core 12 has at least approximately the same coefficient of thermal expansion as the material of the wire which has been wound on and is to be annealed.

One preferred embodiment of the spool is shown in FIGS. 7 to 9:

As shown in FIG. 7, an intermediate flange 14 is mounted on a core 13 of the spool such that it can be displaced in the axial direction of the core 13, to be precise in the vicinity of the flange 2. The intermediate flange 14 likewise consists, for example, of steel. It is connected to the flange 2 via springs 15. As shown in FIG. 8, preferably four springs 15 are provided which are offset with respect to one another uniformly in the circumferential direction. For the guidance of the intermediate flange 14, bolts 16 are provided which are attached fixedly to the intermediate flange 14 and pass through holes 17 in the flange 2, as is shown in a detail in FIG. 9. As shown in FIG. 8, four bolts 16, which are offset with respect to one another in the circumferential direction, may be provided. They also prevent the intermediate flange 14 from tilting on the core 13 during displacement of said core.

In the spool shown in FIG. 7, the winding space 4 is therefore delimited by the flange 1 and the intermediate flange 14. On expansion of the turns 5 of the wire wound onto the spool, the intermediate flange 14 moves in the direction of the stationary flange 2. The springs 15, which are pushed together in the process, move the intermediate flange 14 back into its initial position if the temperature returns to room temperature. The spool in the embodiment shown in FIG. 7 is particularly robust since the flanges 1 and 2 are fixedly connected to the core 13.

This also applies to the spool illustrated in FIG. 10, in which a displaceable intermediate flange 18 with springs 19 and bolts 20, is attached to the core 13, also in front of the flange 1. The same applies for the mode of operation of the intermediate flange 18 as for the intermediate flange 14.

Claims

1. A metal spoool for receving metallic winding material in the form of a wire, comprising:

two flanges in the form of circular disks, arranged parallel to one another, and

an elongate core connecting said flanges and having a circular cross section a smaller radial dimension in comparison with radial dimensions of the flanges, the mid-axis of said core corresponding to mid-axes of the flanges, a winding space for recieving the winding material being delimited by the core and the two flanges, said flanges and core arranged so that the distance between the flanges can alterd elastically by forces acting on them, wherein

the dimensions of the winding space in the direction of the mid-axis of the spool can enlarged at an increased temperature, in comparsion with and initial position at room temperature by forces which are brought about by different coefficients of thermal expansion of the winding material, on the one hand, and of the core of the spool, on the other hand, and

means for bringing the dimensions of the winding space back to the initial position when the temperature returns to room temperature.

2. The spool as claimed in claim 1, wherein the enlarging of the dimensions of the winding space between room temperature and the increased temperature is equal to a length el in accordance with the following equation el=lo1×Δδ(αw−αc), where the variables:

lo1=length of the core at room temperature

Δδ=difference between the room temperature and the increased temperature

αw=coefficient of thermal expansion of the material for the winding material

αc=coefficient of thermal expansion of the material for the core.

3. The spool as claimed in claim 2, wherein the core is in the form of a tube, which is corrugated all the way round transversely with respect to its axis at least in one section of the tube.

4. The spool as claimed in claim 2, wherein the core is attached fixedly to one flange of the spool and is connected to the other flange via a spring mechanism.

5. The spool as claimed in claim 2, wherein the core comprises two tubes which are arranged concentrically with respect to one another and bear against one another and of which one is fixed to one flange and the other is fixed to the other flange and which are connected to one another by a spring mechanism which is effective in the axial direction.

6. The spool as claimed in claim 1, wherein an intermediate flange is arranged in the winding space between the two flanges at least in the vicinity of one flange, which intermediate flange is mounted displaceably on the core and is connected to the flange in whose vicinity it is arranged via springs acting in the axial direction of the core.

7. The spool as claimed in claim 6, wherein outwardly protruding bolts, which pass through holes in the associated flange, are attached to the intermediate flange in the axial direction of the core.

8. A metal spool for receiving metallic winding material in the form of a wire, comprising:

two flanges in the form of circular disks arranged parallel to one another, and

an elongate core connecting said flanges and having a circular cross section and a smaller radial dimension in comparison with radial dimensions of the flanges, the mid-axis of said core corresponding to mid-axes of the flanges, a winding space for receiving the winding material being delimited by the core and the two flanges, wherein the core comprises a material which has a coefficient of thermal expansion which is at least approximately the same as the material for the winding material.

9. The spool as claimed in claim 1, wherein the core is in the form of a tube, which is corrugated all the way round transversely with respect to its axis at least in one section of the tube.

10. The spool as claimed in claim 1, wherein the core is attached fixedly to one flange of the spool and is connected to the other flange via a spring mechanism.

11. The spool as claimed in claim 1, wherein the core comprises two tubes which are arranged concentrically with respect to one another and bear against one another and of which one is fixed to one flange and the other is fixed to the other flange and which are connected to one another by a spring mechanism which is effective in the axial direction.