GB2154159A - Continuous production of profiled metal strips - Google Patents

Abstract

For the continuous production of profiled metal strips, having at least two longitudinally-extending zones of different thickness, shaping of the strip 12 by cutting is effected by milling 13 the strip in at least one such zone 14 to a strip thickness which is reduced in comparison to the starting thickness, this milling process being directly followed by a scraping or planing 16 process for the smoothing of the zones of reduced thickness produced as a result of the milling procedure. The strip is intended to be used for making electrical contact elements. The material disclosed is a copper alloy. <IMAGE>

Description

SPECIFICATION Method and apparatus for the continuous production of profiled metal strips The present invention relates to a method for the continuous production of profiled metal strips having at least two longitudinally-extending zones, with different thicknesses (cross-sectional dimensions), from a starting strip of constant, or approximately constant, thickness, by the starting strip to shape it, the strip being conducted under initial tension past stationary shaping tools.

Conductive metal strips which have one or more longitudinally-extending zones of differing thickness are required for many applications, for example, as starting material for lining claddings or for contact elements in electrical and electronic technology. If the zones in question consist of a thicker zone and a thinner zone at the respective sides of the metal strip, then in the case of contact elements, the thicker zone usually serves for current connection, whilst the thinner zone is used, possibly after appropriate shaping, for the actual contacting to a corresponding counterpart.

In the past, the production of the profiled metal strips required as starting material for such contact elements has been carried out in various ways.

Known rolling processes have the disadvantage that they are limited to specific shapes and, in particular, require complicated tools. Moreover, components produced by rolling processes do not possess the necessary tolerances and the surface quality leaves much to be desired (see German Patent Specification OS 28 36 475).

The use of milling to produce the profiling in the metal strips, although known, has clearly not been successful in practice. Milling processes were considered to be extremely time-consuming and the unfavourable cutting shape produced has been criticised (see German Patent Specification AS 26 47 407).

Previous proposals (see German Patent Specifications AS 26 47 407, and OS 28 36 475) have therefore consisted in removing the material in the thinner strip zone to be formed by paring or planing. One of the ways in which an attempt was made to avoid the so-called "chatter marks" produced by this process was to guide the metal strip through the paring device over a curved surface in order to enlarge the cutting angle. Also, in order to avoid embrittlement of the material, the metal strip was to be processed under a pre-tension below the yield point.

Apart from the fact that a plurality of passages of the strip are required during the scraping or planing step, in order to remove the large volume of material required as a result of the special profiling, the strips produced by the known processes, and the crude products and finished products produced from these stips by division, splitting, or stamping, do not have the surface quality required, for example, for contacts which are to be goldplated.

It is accordingly an object of the present invention to provide an economic production method which makes it possible to produce profiled metal strips of high surface quality.

According to the invention, there is provided a method for the continuous production of profiled metal strip having at least two longitudinally extending zones of different thicknesses from starting metal strip of constant, or approximately constant thickness by cutting the starting strip to shape by passing it under initial tension past stationary shaping tools, wherein the strip is first milled in at least one zone to a strip thickness which is reduced in comparison to the starting thickness, and immediately thereafter, in the same transit past the cutting tools, the surface of the or each zone where the strip thickness has been reduced is smoothed by scraping or planing.

Such a combination of immediately consecutive process stages enables a sufficient amount of matrial to be removed in a single operating step. As a result, a considerable reduction in production time can be achieved. The co-operation of the various cutting tools, which almost result in a reciprocal guidance of the metal strip, means that specific production tolerances can be adhered to, even within narrow limits. The surface quality achieved by means of the invention permits the application, for example electrolytically, of even extremely thin noble metal layers, so that a substantial economy in the use of expensive noble metals, such as gold, silver, platinum and the like, is achieved in further processing, for example, to form electrical contact elements.

A preferred feature in carrying out the invention is that the amount of material removed in the milling process should be a multiple of the amount of material removed by scraping or planing. This means that the actual profiling, for example, the formation of a longitudinal groove, or the removal of strip material in the edge zone at one or both sides of the strip, is carried out by the milling process, whilst the surface roughness and the final dimensions of the strip are determined by the scraping or planing process which concludes the processing.

It is also advantageous for the dimensional accuracy and quality of the profiled metal strip that the thickness of the paring which is removed in the scraping or planing process and which determines the amount of material removed should be set independently of the amount of material removed by the preceding milling process. In accordance with a further feature of the invention, this layer, the thickness of which may, for example, be 0.01 or 0.02 mm, can be removed in two or more scraping or planing steps which are carried out successively and following the milling process. Thus, for example, when a layer of 0.02 mm thickness is to be removed, it is possible, after the milling step, for the profiling to obtain the final strip dimensions and final quality to be effected in two consecutive steps, in each of which 0.01 mm material is removed.

For specific alloys, in particular those having a high spring characteristic, a special guidance of the strip can on occasions simplify the production process. In such cases, it has been found to be expedient for the metal strip which is to be profiled by milling and smoothed by scraping or planing in the milled zones, to be straightened prior to milling. Drawing devices made, for example, of metal or synthetic resin and of appropriate shape are suitable for this purpose.

The basic shaping of the metal strip to profile it is carried out in accordance with the invention, in contrast to currently conventional technology, not by scraping but by milling. It is only for surface finishing that a scraping or planing process is subsequently carried out in the same operating stage.

Therefore the amounts of material, considered as volume, which are removed by milling should be a multiple of the amount of material removed by planing. Depending upon the type of profiling and the kind of material used, for example, CuZn, CuNi, or CuFe, the layer thickness removed by milling can advantageously be, for example, 10, 20 or 50 or more times the layer thickness removed by planing.

It has also been found to be advantageous for the possibly straightened and subsequently milled metal strip to be smoothed by cutting whilst being deflected, for example, while being conveyed over a roller or cylinder. This results in an increase in the cutting angle with a simultaneous reduction in the transverse curvature in the final product.

As already stated, an essential feature of the invention is that, in the course of the processing, the metal strip should pass through the various processing stations consecutively in one operating step. Apparatus therefore, which has been found to be most expedient for carrying out the method of the invention comprises a stationary milling device and one or more stationary scraping or planing devices arranged in series in the direction of movement of the strip. This results in optimum processing and reciprocal influence favouring strip quality.

For the shaping by cutting of particularly hard copper alloys, for example of spring quality, for the additional guidance of the strip a straightening device may be arranged before the milling device.

Such a measure has been found to be particularly advantageous for thicker metal strips.

The invention will now be further described with reference to the drawings, in which: Figures 1 to - are similar schematic cross-sectional views of four different metal strips profiled by a method in accordance with the invention; and Figures 5 to 7 are similar schematic perspective views of three forms of apparatus according to the invention.

Figures 1 to 4 are cross-sections of metal strips profiled by a method in accordance with the invention, possibly having copper alloy basis. Whilst in the strip of Figure 1, a central groove 2 running in the longitudinal direction has been milled out of the strip between the residual edge zones 1 which are equal in volume, and the milled surface has been subsequently scraped, in Figure 2 the groove 3 lies between edge zones 4 and 5, which differ in volume.

Figure 3 shows a strip having a part 6 which is milled out on one side and where ore surface of the remaining metal portion 7 has teen chamfered.

The zone of the original strip, i.e. tie zone which has not been affected either by scraping or by milling, is indicated at 8. Finally, Figure 4 shows a strip cross-section in which the residual central zone 9 of the original strip thickness is bordered by shaped zones 10 and 11 extending to the strip edges.

Figures 5 to 7 illustrate the method of producing the profiled metal strips illustrated in Figures 1 to 4.

Referring to Figure 5, a metal strip 12 which consists, for example, of CuZn alloy, is pared off from a strip feed (not shown) and conveyed in the direction of the arrow to a milling device 13. The cylindrical milling device which is used here cuts a strip 14, extending in the direction of movement of the strip and having a thickness for example of 0.18 mm, from the metal strip 12, the thickness of which is 0.5 mm. A scraping or planing device 15 is arranged in the direction of passage of the strip 12, after the milling device 13. As illustrated, the cutting or scraping blade 16 of this device lifts a shaving having a thickness of 0.01 mm from the surface of the milled part of the strip. This ensures that the milled surface is smoothed, i.e. is freed of any traces of milling.At the same time, as a result of the intervention of the scraping blade 16, the milling process is stabilised, so that narrow production tolerances can be adhered to.

In contrast, Figure 6 illustrates a production method in which a strip 18 consisting, for example, of copper and having a width of 60 mm and a thickness of 1.3 mm, is provided with a central groove corresponding to, for example, the profile of Figure 1, the depth of which is 0.8 mm. This is effected by means of a cylindrical milling device 20 which firstly cuts a groove 21, the thickness of which may, for example be 0.78 mm, from the strip 18. Immediately thereafter, this groove 21 is smoothed by a plane 22, a shaving 23 having a thickness of about 0.02 mm being lifted from the central zone, and the groove 19 so formed is provided with its final shape and dimensions by simultaneous chamfering of the two-sided edges 24, if desired.

Two following planes, 25 and 26, are provided, the function of which is simply to remove any possible burr from the edges of the groove. Naturally, other known means, such as grinding discs, brushes, or the like, can be used for this purpose.

Finally, Figure 7 illustrates the production of a strip 27 of a copper-iron alloy, the width of which may, for example, be 66 mm and the thickness of which may for example, be 1.3 mm, in which as shown in Figure 4, a central zone 28 of, for example, 27 mm is to remain. The thickness of the edge zones 29 of the strip, which are to be produced is to be about 0.4 mm.

For this purpose, two cylindrical milling devices 30 and 31 are provided which, when the strip 27 is passed in the direction of the arrow, produce grooves 32 and 33 which run in the longitudinal di rection of the strip and the depth of which are about 0.9 mm. For the smoothing of the surfaces of these grooves, a planing device 34 is provided which lifts off the shavings 35 and 36 of a thickness of about 0.02 mm and possibly also serves to chamfer the edge regions 37. Any burr which may remain on the central zone during these operating steps, can, as indicated, be removed by means of further planes 38 and 39, or by any other suitable means.

A comparison of the production processes of the exemplary embodiments illustrated in Figures 5 to 7 results in comparative values of about 18 : 1, 39 : 1 and 45 1 for the quantities of material removed as a result of the milling and as a result of the planing processes.

In place of the cylindrical milling devices used in the exemplary embodiments described, it is naturally also possible to use end-milling or other suitable milling devices. On the other hand, it is essential to the invention that the profiling should be carried out by a milling process and that the smoothing and final dimensions and final quality of the finished strip should be achieved by means of a final scraping or planing process.

Claims (13)

1. A method for the continuous production of profiled metal strip having at least two longitudinally-extending zones of different thicknesses from starting metal strip of constant, or approximately constant thickness by cutting the starting strip to shape by passing it under initial tension past stationary shaping tools, wherein the strip is first milled in at least one zone to a strip thickness which is reduced in comparison to the starting thickness, and immediately thereafter in the same transit past the cutting tools, the surface of the or each zone where the strip thickness has been reduced is smoothed by scraping or planing.

2. A method as claimed in Claim 1, wherein the amount of material removed in the milling process is a multiple of the amount of material removed during the scraping or planing process.

3. A method as claimed in Claim 1 or Claim 2, wherein the thickness of the paring or parings removed in the scraping or planing process and which determines the amount of material removed, is set independently of the amount of material removed as a result of the preceding milling process.

4. A method as claimed in Claim 3, wherein the set paring thickness is removed by means in two or more scraping or planing steps which are carried out consecutively in the direction of transit of the strip.

5. A method as claimed in any one of the preceding Claims, wherein the starting metal strip is straightened prior to the milling process.

6. A method as claimed in any one of the preceding Claims, wherein the milled strip is smoothed by cutting whilst being deflected.

7. A method for the continuous production of profiled metal strip substantially as hereinbefore described with reference to the drawings.

8. Profiled metal strip produced by a method as claimed in any one of the preceding Claims.

9. Apparatus for carrying out a method as claimed in any one of Claims 1 to 6, comprising means for continuously feeding said starting strip, and a stationary milling device and one or more stationary scraping or planing devices arranged in series in the direction of movement of the starting strip.

10. Apparatus as claimed in Claim 9, wherein a straightening device for the strip is arranged before the milling device.

11. Apparatus as claimed in Claim 9 or Claim 10, wherein the milling device comprises a cylindrical miller.

12. Apparatus for producing profiled metal strip substantially as hereinbefore described with reference to and as shown in Figure 5, or Figure 6, or Figure 7 of the drawing.

13. Contact elements of coatable quality produced from profiled metal strip as claimed in Claim 8.