CA2279578A1

CA2279578A1 - Multilayer flat cable

Info

Publication number: CA2279578A1
Application number: CA002279578A
Authority: CA
Inventors: Jorma Pohjola
Original assignee: IWS International Oy
Current assignee: IWS International Oy
Priority date: 1998-08-04
Filing date: 1999-08-03
Publication date: 2000-02-04
Also published as: BR9903419A; CN1244020A; EP0978850A3; FI981697A0; JP2000057856A; PL334766A1; EP0978850A2; FI981697A

Abstract

A multilayer flat cable, comprising a continuous strip of thin sheet. The strip of thin sheet is provided with folding zones extending lengthwise thereof, at which the strip of thin sheet is bent for the multilayer cable. In line with the folding zones are weakenings extending lengthwise of the cable.

Description

Multilayer flat cable The. present invention relates to a multilayer flat cable of the type defined in the pre;amble of claim 1.
Prior;known are multilayer flat cables, comprising a continuous strip of thin sheet which is folded for a multilayer flat cable as shown in fig_ 1. The folding zones present in the side edges of such cables tend to counteract the bending of a cable. As a result of sharp bends; the cable fractures easily at its folding zones, which on its part contributes to rupturing the plastic coating of a cable. In addition, the cable will have a bending arch which is discontinuous, as the bending occurs sharply at points of fracture.
An object of the invention is to provide a multilayer flat cable, which is more readily bendable and which is more durable as to its folding zones.
These objectives are achieved by means of a multilayer cable assembly as set forth in claim 1.
The non-independent claims disclose preferred embodiments of the invention.
The invention will now be described with reference to the accompanying dravvings, in which fig. 1 shows a multilayer flat cable, fig. ~ shows a strip of thin sheet according to one embodiment, fig. 3 shows a strip of thin sheet according to a second embodiment of the invention in an axonometric view, and fig. ~t shows a cable according to a third embodiment of the invention in a cross-section.
A c:able 1 is made from a continuous strip of thin sheet 1 a, the material of which preferably comprises copper. The finished multilayer cable is coated with an insulation (not shown), the materials of which preferably comprise plastics generally used as a conductor insulation.
Fig. 2 depicts lengthwise folding zones A, B. C for the strip of thin sheet 1 a, the number of which is three in the illustrated embodiment but the number of zones ma~~ range from one to five. The strip of thin sheet 1 a is pleated at the folding zones A, B, C for the multilayer flat cable 1 of fig. 1, having a height H
which is about quadruple with respect to the material thickness of the thin sheet 1 a, as wet! as a width which is about 1/4 with respect to the width of the thin sheet 1 a_ Prior to folding to its final shape, the strip of thin sheet 1 a of fig. 2 is machined at the folding zones A, B, C for elongated weakenings 2 lengthwise of the strip of thin sheet 1 a, which in this embodiment comprise elongated successive cut-outs. driven through the strip of thin sheet 1 a. The cut-outs 2 present in various folding zones A, B, C can be level with each other in the lateral direction of the strip of thin sheet 1 a or staggered at different levels. Alternatively, the cut-outs 2 can be successive, substantially circular holes, as shown in the folding zone B.
Betvveen the successive cut-outs 2 present in the same zone A, B, C remain webs 3, having a width in the lengthwise direction of the strip of thin sheet 7 a within the range of 0,3 mm - 1 mm, most preferably 0,5 mm.
This removal of material from the folding zones A, B, C assits in folding the strip of thin sheet 1a into the multilayer cable 1, while the webs 3 nevertheless maintain the cable 1 as an integral element. The removal of material eliminates or e:~sentially reduces intra-material stresses normally created in folding, which cau;ce fractures occurring at the folding zones A, B, C, and thus contributes to the durability of a cable.

In the embodiment shown in frg. 3 (the strip of thin sheet 1 a having its material thickness exaggerated in relation to the width), the weakenings 2 comprise continuous recesses or grooves lengthwise of the cable 1 and in line with each folding zone A. B, C. The recesses or grooves 2 are made either by removing or displacing material. The thickness of sheet material at the recesses or grooves has been reduced by 30 - 90 % from the original thickness. The strip of thin sheet 1 a is bent at each weakening 2 according to depicted curved arrows for the multilayer cable 1 of fig. 1. The benefit provided by the recesses 2 for the cable 1 is the same as In the preceding embodiment.
A corresponding removal or displacement of material can also be effected after the bending, whereby weakenings 2a depicted in fig. 4 are worked by grinding or yin equivalent technique to be flush with each other, while reducing the material thickness at the weakenings 2a. The reduced thickness may vary befiNeen 70 - 10 % from the original thickness. This embodiment provides an improved fracture strength for the weakenings 2a.
It is obvious that the above embodiments can be combined in a single cable 1, as ciesired_

Claims

1. A multilayer flat cable (1), comprising a continuous strip of thin sheet (1a), said strip of thin sheet (1a) being provided with folding zones (A, B, C) lengthwise thereof, at which the strip of thin sheet (1a) is bent for the multilayer cable (1), characterized in that in line with the folding zones (A, B, C) are weakenings (2, 2a) extending lengthwise of the cable (1).

2. The cable (1) of claim 1, characterized in that the weakenings (2) comprise elongated cut-outs machined lengthwise of the strip of thin sheet (1a) prior to its bending.

3. The cable (1) of claim 1 or 2, characterized in that between the longitudinally successive cut-outs (2) remain webs (3).

4. The cable (1) of claim 1, characterized in that the weakenings (2) comprise recesses or grooves lengthwise of the cable (1) and in line with each folding zone (A, B, C).

5. The cable (1) of claim 1, characterized in that the strip of thin sheet (1a) has a reduced material thickness which is substantially less at the weakening (2a) than elsewhere within the strip of thin sheet (1a).