US2164021A - Ground-wire clamp - Google Patents

Description

June 27, 1939. RQGQFF 2,164,021

GROUND-WIRE cum Filed Dec. 15, 1936 12v V NT. BY JULIAN RoeoFF MIA/H ATTORNEY.

Parental June 21, 1939 UNITED STATES 2,164,021 oaoomwmu mm Julian Burndy New York Rogofl', New York, N. Y. assignor to Engineering 00., Inc., a corporation of Application December 15, 1936, Serial No. 115,929

, 1 Claim. My invention relates to ground-wire clamps.

' and more particularly humans for connecting electric conductors to ground rods.

In utility grounding practice, it is often customary to drive a copper coated steel rod into the ground and attach ground wires or cables to the rod by means of a clamp.

Up to the present, clamps have been devised which used flexible bands to force the ground rod or pipe against a contact screw to which the conductor cable was electrically connected. In one of these prior clamps, the contact screw 'car ries the current, and is preferably made .of substantially pure copper because of its high conductivity. The contact screw threadedly engages a pressure bar which transmits the pressure from the flexible bands.

In another such clamp, the contact screw again is used to ground the current, and therefore should be made of substantially pure. copper to obtain proper conductivity. Pure copper is soft and has no yield point, and undue pressures cause the metal to creep and loosen the connection- Electrical contact was the this invention, sures were or could be developed.

.- To overcome the weakness inherent in devices important aspect of which rely on current transmission through a contact screw,- clamps were developed which utilized high pressures between ground rod and cable.

Thus connectors were developed having pressure members which, it was assumed, did not to provide a ground clamp carry all the current, and which, by our corollary, could be made of an alloy having high tensile strength and thus allow pressures greatly in exe cess of those permitted by pure copper members which carry current.

Where the construction is as rugged as possible to permit the maximum pressure, the electric contact between cable conductor and ground rod is the only contact relied on' and is established solely by pressure between therod and conductor.

Where the device has been adapted to permit lateral entrance to a continuous cable, the plurality of parts found necessary are awkward to bandie for a rubber-gloved linesman, or they are not readily accessible because .they accidentally fall apart during shipment or handling.

Accordingly, a primary object of'my'invention is to provide a ground clamp for causing an electrical contact between an electric conductor and a ground rod, the component parts of the clamp structurally adapted to produce high pressures and the electrical conductivities of these component parts being sacrificed for mechanical strength. v

Another important object of my invention is capable of being slipped over a ground rod or continuous conducand'consequently no great pres-- tor, and which thoughit may be disassembled intoits component parts, is normally interlocked during shipment and handling.

Another object of my invention is to provide such a .clamp which will lend itself to economical manufacture by high speed production methods.

A further object isto provide a high strength corrosion-resistant clamp which can be stressed to high values in installation and buried directly into the ground without fear of failure. Still another object is to provide centering means for ground rod and cable so that maximum pressures can be applied and developed between the two.

Y I accomplish these and other objects of my invention by providing a U-shaped member, a. novel pressure bar for engagement with the U-shaped member and a.v pressure screw for applying the pressure, none of which membersare designed unit when not in use. The interlocked members may be separated when it is desired to instal the clamp on a ground rod or continuouscable, and

attachment is made with the assurance that all necessary'parts are available and readily accessible.

I attain my objects and accomplish my results as can be readily understood from a consideration of the accompanying description taken together with the drawing, in which:

Fig. 1. is a side view of my clamp assembled 'on I a ground rod and conductor.

Fig. 2 is an end view of the same assembly.

.Fig. 3 is a sectional view with the parts sepa- I rated to permit entrance of the ground rod and conductor.

Fig. 4 is an end view of an assembled clamp, ground rod and conductor, with a protective washer inserted between the pressure screw and conductor.

Fig. 5 is a side view. of the same. 1

'Fig. 6 is a side view of the assembled clamp, ground rod and conductor, with a protective the pressure screw.

Fig. 7 is an end view of the same.

Fig. 8 illustrates the interlocking feature of the component parts of the clamp when not in use.

Fig. 9 illustrates a separation of the interlocking members to provide an entrance for ground rod and conductor. r

Referring to Fig. l, the clamp consists of a sheet metal body I I a forged or extruded pressure bar l2, and a pressure screw l3. The prespressure plate rotatably mounted on'the end of sure screw l3 and the pressure bar l2 are assembled into unitary relationship by striking the end M of the screw IS in order to damage the last thread. The sheet metal body H is bent into the form of a U with a V-shaped bottom I5 as an aid in centering the conductor cable It or ground rod I! which may rest therein.

The two legs 24, of the U-shaped member II are provided with two trapezoidal shaped apertures l8 allowing for movement of the round ends 2| of the pressure bar I2. On the upper surface of the pressure bar l2, grooves l8 are provided which interlock with the upper edge 20 of the apertures I8.

As illustrated in Figs. 3 and 9, in order to release the pressurebar and screw from the clamp, it is first necessary to rotate the pressure screw l3 outwardly from the U. The pressure bar I2 is then released from the upper edges 20 of the apertures I8 and inserted as far as it will go into one of the apertures. This will free one end of the pressure bar, so that the bar may be removed by simply sliding out through the open end of the U. In order to facilitate this process, the ends of the pressure bar are rounded or tapered, as at 2 I, leaving the central portion, where the bending movement is greatest, thicker than the two ends. The parts are so proportioned, however, that in order to prevent accidental disassembly in shipping or handling, the pressure screw l3 need simply be threaded part way or entirely .into the pressure bar l2 and towards the bottom of the U, whereupon the bottom of the screw will strike against the sides of the U and prevent the pressure block from disengaging from the U as illustrated in Fig. 8.

Figs. 4 and 5 show the same assembly as Figs. 1, 2 and 3, with the exception that washer 22 has been added to prevent the end ll of the screw l3 from bearing directly on the cable l6, when it is located above the rod, thus protecting the cable from abrasion or nicking by the revolving pressure screw l3. Washer 22 contains two punched out sections 23, which permit the two legs 24 and the U clamp II to enter. The washer is shaped as at 25 to permit the conductor Hi to be centered within the clamp.

A method of protecting the ground rod from abrasion or nicking when it is on top, is shown in Figs. 6, 7, 8 and 9. Here pressure plate 30 is attached in rotatable relationship to the end M of the screw l3, and acts as an integral part of the pressure screw and pressure block assembly. Thus, when the connector is taken apart, as shown in Fig. 9, there are only two sections to handle. Pressure strip 30 consists of two end wings 33 which are curved to fit the upper rounded surface of the ground rod and a flat section 32 into which the end H of the pressure screw I3 is mounted. The cut-out portions 3| allow the pressure screw and pressure block assembly to move towards the trapezoidal holes l8 without striking the pressure strip 30 against thesides of the U clamp. I

It is apparent that an assortment of conductor sizes can be accommodated in a single sized clamp.

Each of the foregoing embodiments of this invention have the distinct advantage of being made up of low cost elements, the constituent parts in the simplest form being simply a screw, a sheet metal stamping, and an extruded or forged bar. Each of these parts is made by mass production methods in highly specialized machines, which means a minimum tooling up expenses, as well as a low unit cost. In addition, because of the minimum of cutting necessary to be done in the parts, high strength, highly corrosive-resistant copper alloys can be economically used for all the parts, in spite of the fact that such alloys are very difficult to machine. Alloys having the following composition are recommended for strips, pressure screw plates and bars:

98% copper, 1%% silicon,and manganese, having a tensile strength of from 85,000 to 100,- 000 per square inch, the tensile strength being sufficient to produce a distortion of the surface of the electric cable coming in contact with said ground rod.

. In my invention, once the screw is threaded entirely into the block, the assembly cannot work its way free from the sheet metal body. On the other hand, when it is desired to take the connector apart, this can readily be done with only two pieces to handl. It is significant that this may be done even though the height of the holes punched in the sheet metal body is less than the thickness of the pressure bar. This may be an important advantage inasmuch as the less metal is punched from the U, the stronger is that part. This invention also makes possible the use of a pressure plate to prevent abrasion of the conductors and to distribute the pressure evenly without the addition of another part to handle when the connector is takenapart.

Applicants device-distinguishes from all prior art devices in that the U-shaped member is substantially rigid and is not adapted to change its shape to conform with the ground rod or cable supported therein. Provision is also madefor centering the cable and rod with respect to each other, so that the maximum .pressures may be developed by the centrally located pressure screw, whether applied to rod or cable.

I have thus described my invention, but I desire it understood that it is not confined to the particular forms shown and described, the same being merely illustrative, and that the invention may be carried out in other ways without departing from the spirit of my invention, and, therefore, I claim broadly the right to employ all equivalent instrumentalities coming within the scope of the appended claim, and by means of which, objects of my invention are attained and new results accomplished, as it is obvious that the particular embodiments herein shown and describedare only some of the many that can be employed to attain these objects and accomplish these results.

I claim:

A connector comprising a substantially rigid U-shaped member having an aperture in each of the two legs of the U-shaped member; a pressure screw; and a pressure bar for engagement with each of the apertures in the U-shaped member, said pressure bar having a central threaded aperture for said pressure screw and rounded ends to facilitate entrance through the apertures in the legs of the U-shaped member which ends are curved in substantially the same direction as the U-shaped member.

- JULIAN ROGOFF.

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