Field of the Invention

The present invention relates generally to cutters for polymeric materials and, more particularly, to splitters designed to separate the individual conductors of a flat ribbon cable.

Background of the Invention

Flat ribbon cables include a series of parallel, spaced conductors, usually cylindrical in cross-section, coated with electrical insulation. Adjacent insulated conductors are connected by flat ribs to produce, a cable cross-section of a series of circles connected by thin ribs. To terminate this cable to certain types of connectors, the individual insulated conductors must be separated from each other for a distance of approximately 6 to 25 mm. The present standard splitter for such cables consists of two round knife sets of 0.625 mm thick knives separated by 0.625 mm spacers. Of course, this splitter is made for cables having a 0.625 mm conductor spacing. Other spacings are possible and adjustment of the knife spacing will be required. The cable is fed into the .:ip of the knife sets causing the insulated conductors of the cable to be broken apart with odd numbered conductors being bent in one direction and even numbered conductors being bent in the opposite direction. This splitter works well with cables having polyvinyl chloride insulation or these insulated with polymers which are loaded with fillers and so are somewhat brittle and frangible. Other more high performance insulations which exhibit great elongation before fracture, such as

polytetrafluorethylene (FEP), polyethylene, polypropylene, blends of these materials, and thermoplastic elastomers, stretch rather than break in the existing splitters because the cutting knives are slightly separated from each other by the spacers. The insulated conductors are not completely separated by this existing splitter and require manual separation with razor blade type knives. This operation is dangerous and time consuming.

Summary of the Invention

The present invention overcomes the drawbacks of the prior art and completely separates the insulated conductors of a flat ribbon cable by providing a cable splitter which includes knife sets having cutting edges which are free to move toward adjacent cutting edges. By interleaving two sets of knife sets and using springs to force all the cutting edges together, the knives remain in contact and cut with a shearing, scissoring action which cuts completely through the cable insulation, even high performance insulations. In particular, the cable splitter of the present invention includes a base; a cutting arm pivoted to the base for movement between an open position and a closed position; a first set of cutting blades mounted on the base, the first set of cutting blades including a plurality of individual planar blades each having a mounting edge for engagement with the base and a cutting edge disposed opposite the mounting edge and away from the base; a plurality of spacers disposed between each blade of the first set of cutting blades, the spacers having a thickness approximately equal to the spacing of the conductors of the cable, with the measurement to adjacent spacers being equal to twice the width of a knife, the spacers engaging the blades adjacent the

mounting edge and extending only part way to the blade cutting edge so that the cutting edges of the blades are free to approach the cutting edges of each adjacent blade; a second set of cutting blades mounted on the cutting arm, the second set of cutting blades including a plurality of individual planar blades each having a mounting edge for engagement with the cutting arm and a cutting edge disposed opposite the mounting edge and away from the cutting arm; a plurality of spacers disposed between each blade of the second set of cutting blades, the spacers having a thickness approximately equal to the spacing of the conductors of the cable, with the measurement to adjacent spacers being equal to twice the width of a knife, the spacers engaging the blades adjacent the mounting edge and extending only part way to the blade cutting edge so that the cutting edges of the blades are free to approach the cutting edges of each adjacent blade; first biasing means for urging the first set of cutting blades toward each other; second biasing means for urging the second set of cutting blades toward each other; wherein the base and the cutting arm are pivoted to each other such that the first set of cutting blades and the second set of cutting blades are interleaved and engaged in contact with each other by the fist biasing means and the second biasing means in the open position and the first set of cutting blades and the second set of cutting blades move toward each other in a shearing, scissoring manner as the cutting arm is moved toward the closed position. The blades of the splitter are preferably rectangular in shape and have a concave edge to aid in alignment of the insulated conductors and the cutting edges. The cutting edge does not need to be sharp. Preferably, the cutting edge is perpendicular to the side of the blade and approximately 0.003" wide.

Brief Description of the Drawings

The present invention will be described with respect to the accompanying drawings wherein like numbers refer to like numbers in the several views, and wherein: Figure 1 is a side elevational view of a cable splitter according to the invention; Figure 2 is a side elevational view of a cutting blade used in the cable splitter of Figure 1; Figure 3 is a top plan view of a base portion of the cable splitter of Figure 1; Figure 4 is a top plan view of a cutting arm portion of the cable splitter of Figure 1; and Figure 5 is an enlarged elevational view of a portion of the cable splitter of Figure 1 showing meshing of its cutting blades.

Description of the Preferred Embodiment

Figure 1 illustrates a cable splitter, generally indicated as 10, designed to separate the insulated conductors of a flat ribbon cable from each other. The cable splitter includes a base 12 and a cutting arm 14 as major components. The cutting arm 14 is pivotally mounted to the base 12 at a pin 16 extending through two sides of the base 12 and two sides of the cutting arm 14 to define a fulcrum. The base 12 supports a first set of cutting blades 18 and the cutting arm 14 supports a second set of cutting blades 20 which are in mesh with the first set of cutting blades 18 when the cutting arm 14 is in the fully open position illustrated in Figure 1. Each cutting blade 22 of the first set of cutting blades 18 and the second set of cutting blades 20 is shown in Figure 2. The blades 22 are trapezoidal in shape, although they could be many other shapes

(rectangular is shown in Figures 1, 3 and 4), and include mounting edges 24 for attachment of the blades 22 to the base 12 and the cutting arm 14, and cutting edges 26 which engage each other and perform the function of splitting the flat ribbon cable. The blades 22 can be fashioned from any material exhibiting sufficient strength and hardness, but preferred is tool steel, spring steel or stainless steel. The width of the blades 22 will of course determine the width of the cut and so must be matched to the pitch of the conductors of the cable. Returning to Figure 1 momentarily, splitting of a flat ribbon cable is accomplished by inserting the cable atop the first set of cutting blades 18 associated with the base 12 until the cable abuts the second set of cutting blades 20 associated with the cutting arm 14. While maintaining the cable in place, the cutting arm 14 is rotated downwardly about the pin 16 until an adjustable stop 28 hits the surface upon which the base 12 is mounted. Figures 3, 4 and 5 illustrate how the cutting blades 22 are mounted to enable cables to be split effectively. The base 12 and the cutting arm 14 are formed with a series of channels 30 which position the cutting blades 22 with respect to each other. The lands 32 between the channels 30, and consequently the blades 22, act as spacers to maintain the cutting blades 22 at the desired separation. This separation is the spacing or pitch of the conductors of the flat ribbon cable and can be any dimension. The width dimensions of the channels 30 is not critical and, in fact, should be slightly larger than the thickness of the cutting blades 22 so that the blades 22 are free to tilt with respect to the channels 30. It is to be noted that the channels need only enclose a short portion of the mounting edges 24 of the cutting blades 22. It should also be noted that, though the

clearance between the channel and the knife may be as much as 20% of the cable spacing, the repeat measurement to adjacent channels should coincide with twice the blade thickness at accumulated error of no more than one half cable pitch to avoid tilting the knives excessively. Above the mounting edges 24 of the cutting blades 22 are located two rods 34 attached to the base 12 and two rods 36 attached to the cutting arm 14 which extend through holes 38 formed in the cutting blades 22 to locate the blades 22 with respect to the base 12 and the cutting arm 14. Disposed on these rods 34 and 36 are compression springs 40 which contact the outer blades 22 of both the first set of cutting blades 18 and the second set of cutting blades 20 to force the cutting edges 26 inwardly toward each other. The base 12 may additionally include another set of springs 42 bearing upon the center of the first set of cutting blades 18 to fine tune and balance the force compressing the cutting edges 26 of the sets of cutting blades 22. Although sets of springs 40 are shown on both the base rods 34 and the cutting arm rods 36, it has been found that one set of springs 40 can be eliminated. If one set of cutting blades 18 or 20 includes blades which define the outermost blades when the sets are interleaved, then it is only necessary to provide springs bearing on these outermost blades to force all cutting edges 26 into engagement with all others. Figure 5 best illustrates that this spring force causes the cutting blades 22 to be forced together with no clearance between the cutting edges 26. As mentioned earlier, the width of the channels 30 does not rigidly restrict the blades 22 but rather allows the cutting edges 26 to approach each other. Figure 5 also illustrates the lands 32 between the channels should not extend very far toward the blades cutting edges 26 lest

the springs 40 and 42 be inhibited from forcing the cutting edges 26 together. Also illustrated in Figure 5 is the preferred profile of the cutting edges 26. These edges may be flat, but preferably are formed with a concave edge 44 to match the profile of the flat ribbon cable. More preferable, and as shown, the cutting edges 26 are formed with a semi-circular concave edge 44 and flat marginal areas 46 adjacent the semi-circle to precisely match the profile of the cable since this arrangement mirrors the insulated conductors and half the rib of insulation which connects the insulated conductors of the flat ribbon cable. Of course, the optimum shape of the cutting edges 26 will be determined by the profile of the cable with which the cable splitter 10 is to be used. The feature which separates the present cable splitter from those in the past is that the cutting edges 26 are free to approach each other and, in fact, are forced together very strongly by the springs 40 and 42. This eliminates any clearance between the cutting edges 26 of the blades 22 and causes the cutting edges 26 to move relative to each other with a shearing, scissoring movement. In the past, no matter how much attention was paid to tolerances and clearances, there was always some small gap between cutting edges which merely stretched the insulation between conductors rather than cleanly cutting the insulation. This was particularly true with the high performance insulations listed earlier. Thus there has been described a cable splitter which utilizes cutting blades in intimate contact to efficiently separate the insulated conductors of flat ribbon cables. As an added benefit, the action of the cable splitter separates the conductors in the preferred manner wherein even numbered conductors are bent one direction relative to the plane of the cable and odd numbered conductors are bent in the opposite direction

which is useful in terminating the cable to some connectors. . Although the cable splitter of the invention has been described with respect to only a single embodiment, it will be apparent to those skilled in the art that many modifications are possible without departing from the spirit of the invention. For example, the blades may assume many shapes including shapes which would include a rounded cutting edge. The channels used to separate the blades could be replaced by discrete spacers or a comb- like spacer assembly simply positioned above the base and the cutting arm rather being an integral part of these structures. It remains important, however, that whatever spacer is used not interfere with the ability of the springs to force the cutting edges together. Other types of springs could be utilized to force the blades together rather than the helical compression springs shown ^' . For example leaf springs with holes to accommodate the blade positioning rods could be used. And elastomers or hydraulic or air bladders or pistons biasing means would be possible.