US1980020A - Ground rod - Google Patents

Description

NW. 0, 10340 W. R. WEBSTER 1,980,020

GROUND ROD Filed Aug. 24, 1931 Patented Nov. 6, 1934 UNITED STATES PATENT OFFICE 1 Claim.

This invention relates to what is commonly known as a ground rod. It is often necessary in connection with electrical wiring to effectively ground certain circuits or parts of circuits. This is true with respect to many electrical installations, and in connection with the operation of overhead electrical circuits for railways and the like, it is necessary to provide at intervals a conducting connection between lightning arresters l and other devices and the ground. To effect this end it is convenient to drive into the ground a metal rod, which may be six or eight feet in length. This rod must, of course, comprise conducting material and in the usual instance the top of the rod projects above the ground for several inches when installed, and secured thereto is a wire or suitable conductor which is electrically connected to the device or circuit which it is desired to ground.

It is desirable that the rod so used shall be long enough to extend some distance beneath the surface and preferably to project into the moist layers of earth so that a good ground connection will be had. It is, therefore, necessary that the rod should be as stiff and rigid as possible so that it may be driven into relatively hard or resistant soil without bending or buckling. It is also nec= essary that the rod should have good electrical conductivity.

One object of this invention is the provision of an improved ground rod which shall be relatively stiff and rigid and which will have good electrical conductivity.

Another object is to provide a strong inexpensive structure in which the rod has a core of ferrous metal and a thin coating of copper or like metal intimately adhering to the core so as to prevent shucking or displacement of the coating relatively to the core and any looseness between said parts.

To these and other ends the invention consists in the novel features to be hereinafter described and claimed.

In the accompanying drawing:

Fig. l is an elevational view of a rod which forms the inner portion or core of the completed article;

Fig. 2 is a similar view of the same rod after it has been subjected to a cold drawing operation;

Fig. 3 is a view or the assembled inner core and outer jacket, the assembly having been pointed or reduced at one end;

Fig. 4 shows the parts of Fig. 3 after completion of the operation of drawing the assembly through a die to secure the outer covering or jacket upon the core; and

Fig. 5 is a view illustrating the completed rod.

In manufacturing a ground rod according to my invention, I prefer to use for the inner portion or core of the device a rod 10 shown in Fig. 1, which may be a section of an ordinary hot rolled steel rod. This rod is prepared for cold drawing in the usual or ordinary way, and then drawn in a cold state through a drawing die.

This results in a reduction of the diameter of the rod and also serves to harden it and greatly increase its rigidity and stiffness. The rod which results from this operation is shown at 11 in Fig. 2 of the drawing.

A tube 12 of material of high conductivity, such as copper, for example, having an inside diameter somewhat larger than the cold drawn rod 11 is then slipped over the rod 11 until the end of the tube is substantially flush with that of the rod. This end of the assembled rod and tube is then placed into a suitable pointing device and reduced in size or pointed as shown at 13. This pointing operation results in contracting the outer copper tube upon the rod and renders the end of the assembled tube and rod suificiently small to be inserted through the opening of a die which is used in the next operation to be performed.

The end 13 of the assembled tube and rod is then inserted through the opening of a suitable 35 drawing die. This pointed end is then grasped by means of draw bench tongs and the assembly is drawn through the die opening. This causes the tube to be reduced in size and to adhere tightly and securely to the surface of the inner steel rod, as shown at 14 in Fig. 4. It will be understood that as the inner steel rod has a relatively smooth exterior surface due to its preparation for the outer covering, the copper tube will be caused to adhere thereto so closely that in effect the two become parts of a unitary structure, that is, there is no danger of any movement of the copper tube or jacket with respect to the core when the rod is driven into the ground.

The rod which has been formed as described 100 is then cut to the required length, which may be six or eight feet, for example, and is sharply pointed at one end, as shown at 15 in Fig. 5. This enables it to be readily driven into the ground when used.

Rods of various diameters may be made by the improved process heretofore described, the diameter, of course, depending upon the diameter of the inner core or steel rod and the thickness of the copper jacket or tubing. In making a inch 110 rod, for example, I find it convenient to use a hot rolled steel rod approximately of an inch in diameter. when this rod has -been passed through the cold drawing operation and its diameter reduced, as shown in Fig. 2, it will be drawn to approximately .541 inch in diameter.

The tube of copper slipped thereon,- which is preferably a seamless-tube, will have an outside diameter of about of an inch and have a wall approximately .055 of an inch in thickness. The assembled rod and tube may then be pointed, as shown at 13, so that the outside diameter of the assembly at the pointed end ,will be slightly less than of an inch. The assembled rod and tube may then be drawn through a die having 'a inch opening so that the outside diameter of the completed rod with its copper jacket will have a diameter of of aninch. j Other sizes may, of course, be made from rods and tubes having corresponding dimensions. The tube of copper is quite thin, having a'wall many times less thick than the diameter of the core, as only a thin outer shell .of highly conductive metal is required, and on the other hand the reinforcement imparted by the hardened steel core is of such importance that this core should be of comparatively large diameter in order to give the article the requisite mechanical strength.

, It will be apparent that the finished groun rod shown at 16 in Fig. 5 is of composite struc-.

ture having an inner rigid and stiff core of relatively hard material and an outer covering or jacket of high conductivity. The union between the outer covering and the core will be of such a character due to the method of manufacture that the tube and core will adhere tightly together and will to all intents andpurposes be one and the same structure. It will be understood that when the tube is drawn upon the rod which forms ,engaged, i. e., with one extending into minute cavities of the other, thus binding the parts securely together.

While I have shown and described apreierred embodiment of my invention and a preferred method of manufacturing the same, it will be understood that it is not to be limited to all of the details or steps described, but modification and variation may be resorted to within the spirit of the invention and within the scope of the appended claim.

What I claim is:

A ground rod for connecting electrical apparatus to ground comprising a cold drawn core of relatively strong metal. said metal being a ferrous metal, and a cold drawn outer coating of weaker but more highly conductive metal conforming closely to the core, the wall of said coating being quite thin as compared to the diameter ing a conical end. 1

I R. WEBSTER.

Images