US 3845449 A
Two identically curved strips are intermeshed and bolted together to provide a circular clamp for making electrical connection with the ribbon shield of a power cable.
Description (OCR text may contain errors)
[ 1 Oct. 29, 1974 CABLE SHIELD CLAMP 2/1927 Feige 339/251 FOREIGN PATENTS OR APPLICATIONS Inventor: Ronald D. Taylor, Blaine, Minn.
 Assignee: Minnesota Mining and Manufacturing Cmnpany, St Paul, 873,932 4 1942 339 251 France.,.............
22 Filed: Aug. 2, 1973 21 Appl. No.: 384,932
Primary Examiner-loseph H. McGlynn Attorney, Agent, or FirmAlexander, Sell, Steldt & DeLaHunt  ABSTRACT Two identically curved strips are intermeshed and 52 us. 339/14 L, 24/115 A, 24/135 K, 24/284, 174/40 cc, 339/251  Field of Search............ 339/14, 251
bolted together to provide a circular clamp for making 24/135 2791 284; 174/40 CC electrical connection with the ribbon shield ofa power cable.
7 Claims, 5 Drawing Figures References Cited UNITED STATES PATENTS 813,526 Simpson......................,...... 339/251 CABLE SHIELD CLAMP This invention relates to electric power distribution and is concerned particularly with improvements in the grounding of tape or ribbon shielded high voltage power cable.
In making a running splice in power cable it is necessary to join not only the ends of the current-carrying conductors but also the ends of the ribbon shields. For the latter purpose, conventional practice has involved installing jumper wires or cables across the splice. Prior art clamping devices of adequate strength and currentcarrying capacity have invariably been bulky, difficult to install, or otherwise unsatisfactory. Soldering of the jumpers to the shields results in a more compact structure but is difficult to accomplish under field conditrons.
The clamp of the present invention is simple in construction, easily applied, and of fully adequate mechanical strength and electrical current-carrying capacity.
In the drawing,
FIG. 1 is an elevational view showing two of the clamps of FIGS. 2 and 3 in use at a power cable splice area, the cable and cover being shown in phantom;
FIG. 2 is a plan view of a blank;
FIG. 3 is a sectional elevation of an assembled clamp as shown in FIG. 1, taken approximately at line 3 3 thereof;
FIG. 4 is a sectional elevation showing a modified form of clamp with pre-connected jumper cable; and
FIG. 5 is a plan view of a blank for an alternative form of clamp member.
Each clamp consists of two identically curved generally L-shaped plates l1, 12 held together in opposing and intermeshing relationship by a bolt 13 and nut 14. Each plate is centrally perforate within a flat or very slightly laterally warped end portion 15; the remainder of the plate is curved along a circular path and extends over approximately 240 degrees of arc. The end 15 extends radially from the curved portion. The curved central segment 16 retains the full width of the end 15; the curved extension 17 is slightly less than one-half of such width. When placed tightly face-to-face as in FIGS. I and 3, the two pieces intermesh to complete the circle at full width, and the curved portions are terminally unconnected.
In a specific Example for use with 15 KV ribbonshielded power cable, the clamp members are made from a resilient plate of beryllium copper alloy No. 172 (Berylco 25"), A hard, 0.025 inch thick. The blanks are each 3.219 inches long and 1.25 inches wide. The end 15 is 0.700 inch long; the narrow extension 17 is 1.252 inches long and 0.600 inch in width. The segments l6 and 17 are curved to an inside diameter of 1.200 inches. The pieces are hardened by heat treatment to a Rockwell hardness, C scale, of 38-42, and are lightly tin plated.
The method of application will be readily apparent on consideration of FIG. 1. The two halves are slipped over the bared shielded cable-ends into face-to-face intermeshing contact, the resiliency of the pieces being fully adequate for the purpose. Ajumper wire 19 of sufficient load-carrying capacity, previously provided with perforate contact terminal lugs 20, is fitted onto bolts 13 which are passed through the aligned perforations in the two pieces, and nut 14 is tightened in place to hold the assembly firmly together.
The stiffness and resiliency of the hardened alloy are such that, once applied, the clamp cannot be moved by hand. Full electrical contact is obtained, and the current-carrying capacity is entirely adequate for the intended use.
FIG. 4 illustrates a modified clamp 40 wherein one.
clamp member 42 is raised within the full width central portion 46 to provide a rounded loop 48. A segment 45 of a jumper, in this case a stranded cable, is preattached within the loop by soldering as shown at 47. The two halves 41, 42 are held together by bolt 43 and nut 44. The free end of the jumper cable 45 is to be connected to the free end of the corresponding cable of an opposing clamp assembly in a splice situation as described in connection with FIG. 1, e.g., by bolt or other cable-joining means, not shown; alternatively, the free end may be connected directly to ground, e.g., in a termination situation. Advantages of this structure are that the cable-ends may be attached to the clamps prior to installation, may be of any length and easily adjustable to any length of splice area, and are easily interconnected at any desired point. The loop 48 adds to the spring compression reserve of the assembled clamp and this modification is particularly useful on cables of larger diameter and current-carrying capacity.
Another modification is shown in FIG. 5, wherein the terminal extension of the central segment 56 of the generally L-shaped blank 51 is bifurcate, the two legs 57 and 58 intermeshing with similar extensions of an opposing blank when the two are formed and combined as described in connection with FIGS. 1 and 3.
What is claimed is as follows:
1. A clamp comprising a pair of rigidly resilient generally L-shaped electrically conductive metal plates each formed to provide a substantially flat centrally perforate end section, a curved central section of the same width as said end section, and a curved extension of slightly less than one-half of said Width, the curved portions together extending over significantly more than one-half but less than three-fourths of a complete circle, the perforate end section being radially extended from said circle, the two pieces fitting together in face-to-face relationship with the curved portions terminally unconnected to define a circular clamping area.
2. Clamp of claim 1 wherein said central section and said extension each extend over approximately of arc.
3. Clamp of claim I wherein said curved extension is in two parallel parts bifurcate.
4. Clamp of claim 1 including fastening means applied through said perforate end sections for holding said pair of plates together in face-to-face interfitting relationship.
5. Clamp of claim 4 including electrically conductive jumper means attached thereto.
6. Clamp of claim 4 wherein one of said pair of plates includes a raised loop within the central section for solder connection with a jumper cable.
7. Clamp of claim 6 including a jumper cable segment soldered into said loop.