Alternate polarity kickless cables are well known in the art and are widely used to connect welding guns to transformers. Such cables have a number of stranded conductors or individual cables which alternate in polarity. A star separator isolates the adjacent cables which are connected to high current capacity end terminals which include semi-cylindrical halves insulated from each other. Since every other conductor has to be connected to opposite halves, the cable termination presents a complex connection which also happens to be the usual point of wear or failure limiting the service life of the cable. While the design of the cables is to minimize the kicking or twisting which occurs during each welding cycle, some, nonetheless, occurs. One application of such welding cables is in robotic welders. In such applications, the welding head may move into many different positions, again requiring the cable to flex or twist. It is therefore important that the overall cable be quite flexible in the middle, but not too flexible adjacent the terminations, where most stress concentrations occur.
One efficient form of cable termination is shown in prior U.S. Pat. No. 4,199,653 to Talley. Adjacent the terminations, the individual conductors are not twisted or threaded through each other to obtain the alternate polarity. An example of such twisting is seen in prior U.S. Pat. No. 4,487,990 to Lane, where the center cable in each group of three literally has to be twisted around the corresponding cable of the other group. This enlarges the overall cable or restricts internal passages.
In Talley, two sets of conductors are provided with each set of two including end fittings. There are also two individual conductors each mounted in a fitting, or six conductors altogether. The fittings and mounting surfaces on the two terminations are arranged such that a single conductor fitting mounted on one half termination nests that single conductor slightly radially outwardly and between the two conductors of a two conductor fitting mounted on the opposite half termination. In this manner, the conductors do not have to twist or weave around each other and the cable is easier to construct and repair. The conductor fittings are readily mounted on appropriate platforms on the respective termination halves using fasteners. While the cable of the Talley patent has many advantages, one drawback is the use of such fasteners. If a fastener starts to loosen, it will shorten the life of the cable, even though it can readily be repaired. However, with the increasing use of such cables in exotic and expensive robotics machinery, any unscheduled downtime may be detrimental to major production and assembly lines.
For simplicity of construction, the star-shape spider core separator is preferred such as shown in the noted prior art patents. One drawback of such separators is that the V-notch between the radially projecting arms creates two pinch points on a conductor, particularly when the cable is twisted. What is normally a 60.degree. angle, for six conductors, can significantly reduce pinching and grabbing the individual strands of the conductor. This is particularly true if the separator is too hard or of wear resistant material and there is no significant radius at the notch.
It is also important that the separator provide significant flexibility between the terminations and less flexibility near the inflexible terminations. A gradation of increasing stiffness toward the terminations would be preferable to eliminate points of stress concentration.
It would therefore be desirable to provide a cable with the simplicity of conductor positions and construction, as disclosed in Talley, and yet have enhanced efficiency, reliability, and durability.