Patent Publication Number: US-4255612-A

Title: Insulator for covering electric cables

Description:
FIELD OF THE INVENTION 
     The present invention relates to insulators for covering electric cables and, more particulary, to such insulators which are especially adapted for use in connection with flat multiconductor cables. 
     BACKGROUND OF THE INVENTION 
     In copending U.S. patent application Ser. No. 042,709, filed on May 25, 1979, and entitled &#34;Flat Cable and Installation Method&#34;, which is owned by the assignee of the present invention, there is disclosed a technique for connecting flat multiconductor cables. The specification of that copending application is incorporated into this specification by reference thereto herein. 
     Briefly, the method disclosed in that copending application involves overlapping a pair of flat multiconductor cables and then mechanically and electrically connecting the overlapping portions of the cables using metallic connectors which extend beyond the surface of at least one of the cables. Any connector which electrically connects two hot, i.e. electrically energized, conductors also becomes electrically energized and therefore potentially dangerous, inasmuch as an individual who touches the connector, either directly or indirectly, could receive a serious electric shock. 
     In order to electrically insulate the connectors, it has been proposed to cover them with a flat sheet of relatively flexible electric insulation. Because the cable is designed for undercarpet installation, it is undesirable to use a thick sheet of insulation which might, due to its thickness, create lumps in the carpet. However, if the thickness of the insulation is decreased to prevent the formation of lumps in the overlying carpet, the insulation is more susceptible to puncture or piercing by the relatively sharp edges of the connectors when the carpet above is walked on. 
     Pierced or punctured insulation results in the same potentially hazardous condition that exists when the connectors are not covered by any insulation whatsoever. Moreover, the piercing or puncturing of the insulation increases the possibility of eventual tracking or arcing between the partially exposed connectors. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes many of the disadvantages and shortcomings of the devices discussed above by providing an insulator with a spacer which supports electric insulation a distance from an adjacent surface of an electric cable and accommodates protruding portions of any connectors which extend beyond the surface of the cable. The distance between the insulation and the surface of the cable may be selected so as to inhibit the connectors from cutting into the insulation, thereby preserving the integrity of the insulation to avoid the safety and tracking problems discussed above. 
     In one especially advantageous embodiment, the spacer is made from a relatively noncompressible material having a plurality of openings therein. The noncompressibility of the spacer permits it to have a thickness which is approximately equal to the distance that the connectors extend beyond the surface of the cable, thereby maintaining as low a profile as possible to inhibit the formation of lumps in an overlying carpet. Each of the openings is adapted to receive a corresponding one of the connectors. By making the spacer from an electric insulating material, portions of the spacer interposed between adjacent connectors can function as a barrier to further inhibit tracking between the connectors. 
     Another aspect of the invention involves sandwiching overlapping portions of a pair of cables, which are electrically connected to each other by at least one connector, between a pair of insulators. Each of the insulators is sized and shaped so as to completely cover and overhang the overlapping portions of the cables. Interfaced overhanging portions of the insulators are attached together so as to envelop the overlapping portions of the cables, thereby inhibiting moisture and other foreign substances from getting between the overlapping portions of the cables and contacting the connectors. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the invention, reference may be had to the following description of an exemplary embodiment taken in conjunction with the accompanying figures of the drawings, in which: 
     FIG. 1 is a top plan view of one embodiment of an insulator constructed in accordance with the present invention, a portion of the insulator being broken away to facilitate consideration and discussion; 
     FIG. 2 is a cross-sectional view, taken along line II--II in FIG. 1 and looking in the direction of the arrows, of the insulator shown in FIG. 1; 
     FIG. 3 is an exploded view of one embodiment of an insulator-cable combination construction in accordance with the present invention; and 
     FIG. 4 is a cross-sectional view of the insulator-cable combination shown in the exploded view of FIG. 3, the cross-section being taken along a diagonal line similar to the line II--II in FIG. 1. 
    
    
     DESCRIPTION OF EXAMPLARY EMBODIMENTS 
     With reference to FIGS. 1-4, in which like elements are designated by the same reference numerals, there is shown an insulator 10 including a spacer 12, a thin clear film of electric insulation 14 laminated to one face 16 of the spacer 12, a layer of pressure-sensitive adhesive 18 applied to an opposite face 20 of the spacer 12, and a liner 22 removably attached to the adhesive 18. 
     The spacer 12 is preferably made from a relatively noncompressible, electric insulating material, such as polyvinylchloride. Spacer 12 is sized and shaped so as to completely cover and overhang overlapping portions 24, 26 of a pair of flat multiconductor cables 28, 30, respectively (see FIGS. 3 and 4). Although the spacer 12 is shown as being square in FIG. 1, it can have any other suitable shape depending upon the configuration of the overlapping portions 24, 26 of the cables 28, 30, respectively. 
     A plurality of holes 32 extend through the spacer 12 between the faces 16, 20 thereof. The holes 32 are sized, shaped, and arranged so as to receive connectors 34 (see FIGS. 3 and 4) which electrically and mechanically connect the overlapping portions 24, 26 of the cables 28, 30. Tracking between the connectors 34 is inhibited by the spacer 12. 
     The connectors 34 may be any suitable electric-conductor such as is disclosed in copending U.S. patent application Ser. No. 042,441, filed on May 29, 1979 and entitled &#34;Self-Locking Clamp Member,&#34; which is owned by the assignee of the present invention. The specification of that copending application is incorporated into this specification by reference thereto herein. 
     Each of the holes 32 has an elongated hexagonal shape which is symmetrical about a line 36 perpendicular to and bisecting the two opposite parallel sides 38, 40 of the holes 32, so that each of the holes 32 is divided into two longer mirror-image portions 42, 44 (see FIG. 1). Each of the portions 42, 44 has a generally pentagonal shape which matches the pentagonal shape of at least one of a pair of arms 46, 48 of a corresponding one of the connectors 34 (see FIGS. 3 and 4), so that each of the connectors 34 can be arranged in a corresponding one of the holes 32 in either of two different orientations 50, 52 (indicated by dotted lines in FIG. 1) with respect to the line 36. The size and shape of the holes 32 may be varied depending upon the size and shape of the connectors 34. 
     A single substantially square aperture 54 is arranged in one corner 56 of the spacer 12. This square aperture 54 extends through the pressure-sensitive adhesive 18 and release paper 22 as well unless they are both made of clear materials. No similar aperture is required in insulation 14 because it is clear, which also permits an inspector to view the connectors 34 to determine that they are the correct connectors and properly installed. In the event that insulation 14 is not clear, then a similar aperture would be required in insulation 14. A series of three substantially square apertures 58 extend along an edge 60 of the spacer 12 in alignment with each other and the aperture 54. The apertures 54, 58 are designed for automatically registering the holes 32 with the connectors 34, for instance, by aligning the aperture 54 with two intersecting edges 62, 64 of the cables 28, 30 respectively, (see FIG. 3) and then aligning at least one of the apertures 58 with the edge 62 of the cable 28. Markings or locating lugs on the face 20 of the spacer 12 can be used in place of the apertures 54, 58. 
     The film 14 of electric insulation can be made from any suitable material, such as a laminate of polyvinylchloride and polyester adapted for lamination to the spacer 12. Alternatively, the film 14 can be formed monolithically with the spacer 12. 
     In order to prevent the film 14 from being pierced or punctured by the arms 48 (see FIG. 4) of the connectors 34, the film 14 is supported a predetermined substantially fixed distance from the arms 46, 48 of the connectors 34 by the spacer 12. The thickness of the spacer 12 may be varied to vary the distance between the film 14 and the arms 46, 48 of the connectors 34, as long as the film 14 is positioned above the arms 46, 48 of the connectors 34 so as to avoid being cut by the arms 46, 48 of the connectors 34. 
     The liner 22 prevents the inadvertent sticking of the pressure-sensitive adhesive 18 to the cables 28, 30 or other objects. Preferably, the liner 22 is made from a piece of clear plastic, so that the apertures 54, 58 can be easily observed through the liner 22. 
     FIGS. 3 and 4 illustrate a typical tap splice in which the cables 28, 30 are arranged perpendicular to each other. The cable 28 has five electric conductors 66, each of which is electrically and mechanically connected to a corresponding one of five electric conductors 68 of the cable 30 by a respective one of the connectors 34. The five connectors 34 extend diagonally across the overlapping portions 24, 26 of the cables 28, 30 respectively. 
     When applying the insulator 10 to the overlapping portion 26 of the cable 30, the liner 22 is bent back onto itself in such a manner that a portion of the liner 22 extends beyond an edge 70 of the spacer 12. The portion of the liner 22 extending beyond the edge 70 of the spacer 12 is then pulled a distance sufficient to expose a portion of the pressure-sensitive adhesive 18 located adjacent to the edge 60 of the spacer 12, so that a corresponding portion of the spacer 12 can be attached to the overlapping porition 26 of the cable 30 by the exposed portion of the pressure-sensitive adhesive 18. Further pulling of the liner 22 exposes the remainder of the pressure-sensitive adhesive 18 on the face 20 of the spacer 12, so that the insulator 10 can be adhesively attached over its entire length to the overlapping portion 26 of the cable 30. 
     If the insulator 10 is properly installed, the arms 48 of the connectors 34 will register with five of the holes 32 which are aligned diagonally across the face 20 of the spacer 12 (see FIG. 1). The other two of the holes 32, which along with the middle one of the five diagonally aligned holes are aligned laterally or longitudinally across the face 20 of the spacer 12, may be used when insulating a tap splice between five-conductor electric cable and three-conductor electric cable. For instance, any one of the three laterally or longitudinally aligned holes may register with a connector 34 which selectively connects one conductor of a three-conductor cable to one of three corresponding conductors of a five-conductor cable. Of course, the number and arrangement of the holes 32 may be varied depending upon the configuration of the connectors 34. 
     As shown in FIGS. 3 and 4, another insulator 72 is applied to the overlapping portion 24 of the cable 28. The insulator 72, which is identical to the insulator 10, includes a spacer 74, a thin film of electric insulation 76, and a layer of pressure-sensitive adhesive 78. The spacer 74 has a plurality of openings 80 for receiving the arms 46 of the connectors 34 and a plurality of apertures 82 used, when necessary, to properly align the insulator 72 during its application to the overlapping portion 24 of the cable 28. 
     When the insulators 10, 72 have been properly installed, overhanging portions 84 of the insulator 10 are adhered to overhanging portions 86 of the insulator 72 by the pressure-sensitive adhesives 18, 78 (see FIG. 4). The adhered insulators 10, 72 cooperate so as to completely envelop exposed ends 88 of the conductors 66, the connectors 34, and the overlapping portions 24, 26, of the cables 28, 30, respectively. 
     To minimize any effects of pinhole passages through the insulators 10, 72 which could act as capillary tubes to conduct moisture to the interspace between the cables 28, 30, the interior surfaces of the overlapping portions 24, 26 may be coated with a filler material such as a mastic to completely seal the cables 28, 30. This filler provides a total solid insulation between the cables 28, 30, tends to cause any moisture that enters the interspace to be pocketed, and provides some pressure relief for forces applied downwardly, directly on the joint. If the filler is a pressure-sensitive adhesive, it can additionally be used to temporarily set the cables 28, 30 with respect to one another and permit their being handled as a single unit during later installation of the connectors. 
     It will be understood that the embodiments described herein are merely exemplary and that a person skilled in the art may make many variations and modifications without departing from the spirit and scope of the invention. For instance, the insulator of the present invention may be applied to round electric cable as well as flat electric cable. Also, the insulator is equally suitable for use in covering any overlapped portions of a pair of electric cables which are spliced together by, for example, a butt splice or any other type of splice. All such modifications and variations are intended to be included within the scope of the invention as defined in the appended claims.