|
(11) | EP 0 106 518 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
|
|
|
|
|||||||||||||||||||
| (54) | Flat cable |
| (57) A flat cable comprising a series of conductors (11) insulated by plastics material
and located side by side in parallel coplanar relation by a series of longitudinally
spaced, transverse, plastics webs (12) integrally joining adjacent insulated conductor
portions (13), the webs isolating between them groups (16) of insulated conductors
(11) located in laterally spaced apart relation, each group (14) of insulated conductors
(11) being stiffly flexible In transverse direction In the plane of the cable such
that each group (14) can be deformed for routing around obstacles from a rectangular
profile to the profile of a parallelogram independently of an adjacent group and will
maintain such deformation when the flat cable is located against both a horizontal
and vertical support. |
[0002] Flat cable comprising a series of insulated conductors located to extend side by side in parallel coplanar relation is well known and in increasing demand for various applications as a result of the increasing complexity and compactness of electrical hardware.
[0003] In particular, there is a growing interest in the application of flat cable to electrical harnesses and to office and domestic wiring.
[0004] A problem of great practical difficulty arises both in the field and in assembly of harnesses when routing flat cable around corners or unforeseen obstacles. As a result of the width of the cable, the radius of curvature of the outside of the bend will be significantly less than that of the inside of the bend with the result that the arcuate length of the outer individual conductors will be substantially greater than the arcuate length of the wires individual conductors at the bend.
[0005] In conventional flat cable, where the adjacent insulated conductors are joined by a continuous web, the differential arcuate length produces both undesirable distortion of the cable out of its general plane and the compressive forces and tensile forces produced in the inner and outer conductors respectively, result in stored energy causing the flat cable to spring back making manipulation in the field very difficult..
[0006] For this reason, numerous proposals have been directed to folding the cable into specific overlapping configurations to enable routing around corners.
[0007] Clearly, the resulting cable still does not lie entirely flush with a floor or wall panel on which it is routed and the overlapping technique is even less suitable for relatively thick flat cable for higher currents such as those encountered in office and domestic use.
[0008] An additional requirement is the facility to connect in the field, terminals to individual conductors or to predetermined groups of conductors at desired locations intermediate the ends of the flat cable. In known flat cable where the insulated conductors are located by a continuous web of insulation extending between adjacent conductors, it has been necessary to prepare the cable by slitting or punching out portions of the web to free the insulated conductors for termination which is time consuming and laborious particularly when carried out in the field.
[0009] A prior proposal directed to a flat cable comprising a series of insulated conductors located side by side in laterally spaced apart parallel coplanar relation by a series of longitudinally spaced transverse insulating webs joining adjacent insulated conductor portions is described in Japanese Utility Model No. 48-60075.
[0010] However, there is no indication that such cable can readily be permanently deformed in the field to permit routing around obstacles.
[0011] In a cable according to the invention, the webs isolate between them groups of insulated conductors located in laterally spaced apart relation, each group of insulated conductors being stiffly flexible in transverse directions in the plane of the cable such that each group can be deformed for routing around obstacles from a rectangular profile to the profile of a parallelogram independently of an adjacent group and will maintain such deformation when the flat cable is located against both a horizontal and vertical support.
[0012] Deforming successive groups of insulated conductors in the plane of the cable and in the same direction enables a substantial change in cable direction to be built up incrementally, the flat cable adopting a stepped configuration, while remaining completely planar. The webs remain substantially parallel to each other after deformation and the conductor portions joined to the web remain undeformed extending in the original direction of the cable. The longitudinal separation of the webs is reduced by the deformation while the lateral spacing of the individual conductors of the groups is also reduced, central portions of the conductors remaining straight with their opposite ends being curved in mutually opposite senses adjacent the webs obviating any net curvature in one direction.
[0013] Any build up of stress resulting from net curvature in one direction in the prior flat cable is therefore avoided and there is no significant tendency for the cable to resile, enabling routing in the field to be carried out easily by a single operator without any requirement (within limits) to fix the cable to a supporting surface during deformation.
[0014] In addition, access to the individual insulated conductors is available without a requirement for preparation of the cable in the field. The separation of the individual conductors of the group may readily be adjusted to any desired pitch (within limits) to facilitate mass termination.
[0015] Examples of cable folding proposals for routing are described in U.S. Patent No. 4,319,075; U.S. Patent No. 4,283,593; U.S. Patent No. 4,219,928; U.S. Patent No. 4,065,199, and U.S. Patent No. 3,544,192.
[0016] A ribbon cable having a perforated web to permit twisting is disclosed in U.S. 2,626,303 and a ribbon cable having slits in plastics web joining adjacent insulated conductors is disclosed in U.S. Patent 2,361,374. A means for providing strain-relief holes in tape cable is described in U.S. Patent No. 3,243,846. Apertured cable is also disclosed in U.S. Patent No. 3,239,916 and U.S. Patent No. 3,818,117.
[0017] Examples of flat cables according to the invention will now be described with reference to the accompanying drawings in which:
Figure 1 is a plan view of a first example of flat cable prior to routing;
Figure 2 is a similar view of the cable after deformation for routing;
Figure 3 is a similar view of a second example of flat cable prior to routing; and,
Figure 4 is a similar view of the second example after deformation for routing.
[0018] As shown in Figure 1, the flat cable comprises a series of insulated conductors 11 located side by side in parallel coplanar relation by a series of longitudinally spaced transverse webs 12 integrally joining adjacent insulated conductor portions 13. The webs 12 isolate between them groups 14 of insulated conductors located in laterally spaced apart relation.
[0019] The cable may be deformed in the field from the configuration shown in Figure 1 to the configuration shown in Figure 2, for example, for routing around an obstacle by manually moving successive webs transversely of the longitudinal direction of the undeformed cable. The separation both of the webs from each other (D) and of the conductors from each other is reduced although they remain in generally parallel relation. The individual groups of conductors 14 are deformed from a generally rectangular profile to the general profile of a parallelogram. The cable will largely maintain the deformation even when located in a vertical plane, for example, against a wall board enabling routing of the cable around obstacles to be carried out easily during, for example, the wiring of buildings.
[0020] In this example, the conductor insulation and the webs are polyvinyl chloride and the stranded conductors are 26 gauge. The thickness of the webs is .024 inches.
[0021] In the second example shown in Figures 3 and 4, primed reference numerals designate similar parts. The insulation is polyvinyl chloride and the stranded conductors are 22 gauge. The thickness of the webs 12', is the same as in the first example but their lengths, relative to the lengths of the groups of conductors 14', is much greater providing a cable of greater stiffness, more able to sustain the deformed configuration.
1. A flat cable comprising a series of insulated conductors (11) located side by side
in laterally spaced parallel, coplanar relation by a series of longitudinally spaced,
transverse, insulating webs (12) joining adjacent insulated conductor portions (13),
characterized in that, the webs (12) isolate between them groups (14) of conductors
(11) insulated by plastics material and located in laterally spaced apart relation,
each group of insulated conductors (14) being stiffly flexible in transverse directions
in the plane of the cable such that each group (14) can be deformed for routing around
obstacles from a generally rectangular profile to the general profile of a parallelogram
independently of an adjacent group (14) and will maintain such deformation when the
flat cable is located against both a horizontal and vertical support.
2. A flat cable comprising a series of insulated conductors located side by side in
parallel coplanar relation by a series of longitudinally spaced, transverse, insulating
webs (12) joining adjacent insulated conductor portions (13), the webs (12) isolating
between them groups (14) of insulated conductors (11) located in laterally spaced
apart relation, each group (14) of insulated conductors (11) being stiffly flexible
in transverse directions in the plane of the cable and groups (14) having been deformed
in the plane of the cable from generally rectangular profiles to the general profiles
of parallelograms.
3. A flat cable according to claim 1 or claim 2 in which the transverse web (12) are
plastics material and integrally formed with the conductor insulation.