FIELD

[0001 ] The invention relates to a method for manufacturing a current conductor and to a current conductor.

BACKGROUND

[0002] Flexible current conductors are used in locations where a rigid connection is not appropriate due to vibration, thermal expansion or movement of the current conductor.

[0003] Typically a current conductor has an elongated structure and contains a plural number of sheet layers.

[0004] Prior art sheets are fastened together for example by welding or stapling them at their ends. However, this is complicated and not an optimal solution in terms of electrical conductivity.

BRIEF DISCLOSURE

[0005] It is therefore an object of the invention to provide a manufacturing method, an arrangement implementing the method, and a current conductor. The object of the invention is achieved by a method and arrangement characterized by what is stated in the independent claims. Preferred embodiments of the invention are disclosed in the dependent claims.

[0006] An advantage of the method and arrangement of the invention is that compared with the prior art, the manufacturing of current conductors becomes significantly easier. According to the invention a current conductor is entirely made of a single uniform piece of strip, all prior art work phases required to interconnect separate pieces of strip being thus left out.

LIST OF FIGURES

[0007] In the following the invention will be described in greater detail with reference to preferred embodiments and the accompanying drawings, in which

Figure 1 illustrates an embodiment of the method:

Figure 2 is a block diagram of an apparatus arrangement; Figure 3 illustrates the formation of a strip coil;

Figure 4 illustrates the pressing of a formed strip coil; and Figure 5 illustrates the bending of a pressed strip coil.

DESCRIPTION OF SOME EMBODIMENTS

[0008] The embodiments disclosed below relate to current conductors that may be used for interconnecting electronic devices and components in an electrically conductive manner. The current conductor in question is preferably flexible, as this allows it to be used in environments where the current conductor is subjected to temperature variations, vibration or movement.

[0009] The material used to fabricate the current conductor is electrically conductive. For example, the material may be metal, such as copper or aluminium. Other possible materials to be used include an electrically conductive metal alloy or some other electrically conductive material.

[0010] Preferably the material to be used is strip-like or cut into a strip-like form and hence it is preferably a copper strip, for example, having a width of 10 to 150mm and a thickness of 0.03 to 0.3mm.

[0011] In the embodiment of Figure 1 the method starts from step 100, where a 2800mm long piece of a copper strip is cut with the aim of fabricating an elongated current conductor with 14 conductor portions each 200mm in length between the ends of the current conductor. In other words, the current conductor is made of a single piece of strip.

[0012] In step 102 the cut strip having a length of 2800mm, for example, is made into a coil which in this embodiment consists of 7 windings. The side profile of the coil thus formed may be oval or elliptic, for example.

[0013] In step 104 the coil is formed into a current conductor by bringing opposite sides of the coil towards each other. This shaping may be made with pressing means, for example, placed on the opposite sides of the coil. By moving the pressing means towards each other, the coil between them flattens into a thickness which is substantially n ^* t, n being the number of windings and t the thickness of the original coil. Instead of or in addition to the pressing, a flat coil shape may be achieved also for example by drawing opposite ends of the coil away from each other and possibly subjecting the coil to a simultaneous pressing from outside the coil.

[0014] The shaping in step 104 means that the overall shape/side profile of the coil changes from an oval coil shape, for example, to a flat one. During the shaping, which may thus consist of pressing, for example, the strip is subjected to forces that cause a deformation in an advancing strip. This means that in the pressed shape, two ends are formed to the coil is, the strip making turns of substantially 180 degrees at the ends. In other words, in this context 'shaping/pressing' does not refer to a deformation of the strip material.

[0015] In step 106 the current conductor may be subjected to further measures, if desired, such as making of fastening holes. The current conductor may be provided with one or more fastening holes at one or both ends.

[0016] In step 106 the current conductor may also be bent, if desired, to a desired shape. One or more bending points may be provided, and their bending angles may vary depending on the purpose of use. The bending axis, about which the bending is made, may be parallel to the width of the current conductor, although it may also be at an angle other than a right angle to the longitudinal axis of the current conductor. Likewise with the pressing in step 104, also bending causes a permanent deformation in the pressed current conductor. This means that a current conductor made of a metal strip, for example, substantially stays in its bent shape.

[0017] The method of Figure 1 provides a number of advantages. In the starting step 100 a piece of strip required for a current conductor is obtained by a single cutting measure. Prior art current conductors are manufactured using a plural number of pieces of strip, which all have to be cut separately and later attached together by welding or soldering, for example. Compared with the prior art, the solution now presented reduces the number of measuring and cutting actions from seven to a single action. Further, the present method allows a single piece of strip to be handled in subsequent steps, whereby mutual aligning of a plurality of pieces of strip in different work phases is not needed, which further simplifies the making of the current conductor.

[0018] Figure 2 is a block diagram illustrating an embodiment of an apparatus arrangement. The disclosed apparatus arrangement may be implemented in practice by one and the same apparatus or by a plural number of separate apparatuses.

[0019] Consequently, the arrangement includes a control unit for controlling the operation of one or more parts of the process by a computer program, for example.

[0020] The arrangement also includes cutting means 202 for cutting a strip. The metal strip to be used in the manufacture of current conductors may be on a coil comprising several hundred running metres, a piece of strip having a suitable length and needed for one current conductor being cut from the coil with the cutting means 202. The current conductor to be formed thus consists of a uniform piece of strip without strip joints.

[0021] The arrangement further includes coiling means 204 for winding the cut piece of strip to form a coil consisting of at least two strip windings. It is also possible that the final coil consists of several dozens of windings. The strip is arranged to the coil so that the strip layers substantially set one on top of the other.

[0022] The arrangement further includes flattening means 206 for rendering the strip winding formed onto the coil into a flat shape. These means may preferably consist of pressing means, in which case the pressing may be performed using two planar pieces, for example, arranged on opposite sides of the strip coil so that the planar pieces set against the surface of the topmost strip on the strip coil along the width dimension thereof. The planar pieces are moved towards each other so that the strip coil between them is pressed into a flat and elongated current conductor, in which the strip layers set substantially against one another.

[0023] The arrangement may further include perforating means 208 known per, which may used for making one or more fastening perforations to one or more ends of a completed current conductor. Typically each end of the current conductor is provided with one hole enabling a bolt and screw fastening. The holes at different ends of the current conductor need not be equal in size.

[0024] The arrangement may further include bending means 210 known per se for bending the current conductor into a desired shape. The bending means may include a pushing means, for example, and two bending planes. The bending planes are placed on a different side of the current conductor than the pushing means. The pushing means is placed to a desired bending point and pushed forward, the bending planes placed to the opposite side thus causing the current conductor to bend at the bending point. The bending angle to be applied may be freely chosen according to the purpose of use.

[0025] Figure 3 illustrates a winding apparatus. The figure shows a strip cut for manufacturing one current conductor, the thickness of the strip being indicated with reference t. The thickness may be 0.5mm, for example. The width of the strip, in turn, may be some dozens of times the thickness of the strip. [0026] The strip, which may be a flexible metal strip, has a forward end and a tail, which are indicated by references 31 OA and 31 OB, respectively. The figure also shows winding rollers 304 placed above, below and on the sides. The rollers are rotated in the direction indicated by the arrow for winding the strip into a strip coil 300. In the example of Figure 3 the strip has been wound into a layered coil of three windings/layers. The coil in Figure 3 has an elliptic shape, the strip advancing evenly, without abrupt bends, on the coil.

[0027] Figure 4 illustrates a pressing step in the manufacture of the current conductor, this step being performed after the coiling step of Figure 3. In the pressing step, the coil 300 formed in Figure 3 is moved between planar pressing planes 406A and 406B of the flattening means. When the pressing planes are subjected to force F for moving them towards each other, the strip coil between the pressing planes flattens into a flat shape 300A. In this context the term 'flat shape' means that a central opening present in the coil at the start has substantially disappeared and the different sides of the coil have set against one another. The flattened strip coil 300A has two distinguishable ends 312A and 312B, where the coiled strip makes windings of substantially 180 degrees.

[0028] As is shown, the flattened current conductor 300A has six windings, formed of the strip coil of Figure 3, which had three full windings of strip. Consequently, the current conductor 300A has a thickness n ^* t, where t is the thickness of an individual strip and n the number of the layers, i.e. six in Figure 4.

[0029] The pressing places of Figure 4 are to be considered only as one example of an apparatus solution suitable for the pressing. Obviously, pressing planes 406A and 406B may be equal to an entire current conductor in length, or longer, for example. Further, instead of moving both the pressing planes towards each other, it is possible to keep one of the planes stationary.

[0030] Figure 5 illustrates an apparatus solution for bending the flattened/ pressed current conductor formed in Figure 4. The arrangement includes two bending planes 510B and 510C placed on the same side of the current conductor, with the desired bending point between them and at a desired angle a to each other. The figure also shows a pushing element 51 OA, which may be a piece to be placed on a pushing point along the width dimension of the strip. The length of the pushing element in the width dimension of the strip is at least equal to the width of the strip so that the pushing element supporting the entire width of the strip during the pushing.

[0031] When the bending of the straight elongated current conductor formed in Figure 4 is started with the apparatus solution of Figure 5, the current conductor is at first supported only by the angles of the bending planes 510B, 510C that are furthest away from one another. As the pushing proceeds, the current conductor bends at the bending point into the shape shown in Figure 5, and in the end situation the current conductor sets completely against planes 510B, 510C to the bent shape.

[0032] A person skilled in the art will find it obvious that as technology advances, the basic idea of the invention may be implemented in various ways. The invention and its embodiments are therefore not restricted to the above examples, but may vary within the scope of the claims.