US3012089A - Grounding rod - Google Patents

Description

' of the connected nited ttes 3,012,089 GRQUNDTNG RGB Frederick George Ridgers, 91 Arkell St., Hamilton, Ontario, Canada Filed May 26, 1959, Ser. No. 815,336 Claims Priority, application Canada Dec. 15, 1958 1 Claim. (Cl. ll'7Ai-7) This invention relates generally to ground rod constructions for electrical equipment.

More specifically, the invention relates to ground rods which are formed from smaller sectional rods shaped for quick self-holding connection.

The invention is in fact an improvement over ground connections for electrical equipment such as are disclosed and illustrated in Canadian Patents Nos. 454,152 dated January 18, 1949, to Canadian Line Materials Limited and 473,618 dated May 15, 1951 to A. l. Lawson. This is the closest prior art known to the applicant.

It can be said that in the generation, transmission and use of electrical energy, there are components from which any non-functional accumulation of electricity must be dissipated by carrying it to earth. Some electrical circuits rely on the earth carrying the return current. In this case the electrical energy rnust be introduced to the earth with a minimum electrical resistance.

Various devices and schemes are presently employed for grounding electricity. A standard method is the driving of a metal rod into the earth and leading the circuit to earth through the rod.

In using a metal rod for grounding it is necessary to drive the rod into the earth until a predetermined factor of electrical resistance has been reached. For instance, the factor at electrical resistance would differ in watersaturated earth and substantially dry earth.

To effect the minimum resistance factor it is sometimes necessary to drive the metal rod a considerable distance into the earth. This is a time and lahour consuming operation with respect to which any characteristic of metallic rod that effects economy is important since a great many of such installations must be made.

Another important aspect in achieving minimum electrical resistance is that there should be as few as possible joints since each joint contributes a certain amount of resistance.

The conventional. grounding rod comprises a solid steel bar approximately feetin length and certain conditions may require several rods to be driven in as a continuing structure before the factor of electrical resistance reaches the required minimum. The connection between 'the successive conjoining bars forming the completed grounding rod installation must have good electrical conductivity characteristics and must also have mechanical strength to withstand the strenuous drivng efiort to which it may be subject. Any design of coupling must of necessity be effective as to these two characteristics.

A conventional union provided for coupling successive grounding rod bars follows in conception the conventional method of joining pipes with threaded connectons. The bars are threaded on each end and a threaded coupling is provided into which the ends of the bars are threadably secured. The aforesaid patent, 454,152, illustrates a similar type of conventional coupling.

There are disadvantages with the use of a threaded couplng connection. For example, there is present the factor of time consumed in lining up the bars into position to engage the female threads of the coupling and then twisting the bar into engagement with the coupling. There is also the factor of resistance to driving created by the coupling protruding beyond the outer periphery grounding rods. Additionally, in driving the rod into position in the earth, the protruding cou- Fatented Dec. 5, 1858i pling tends .to push the earth away from the grounding rods proper thus preventing a snug contact with the earth of the rods and consequently reducing its effectiveness.

Canadian Patent No. 473,618 discloses a method of coupling grounding bars which in conception substitutes self-holding tapers for the threaded coupling arrangement previously discussed. in this patented self-holding coupling there are disadvantages. There is for instance, the factor and presence of four surfaces to machine to prepare the coupling and engaging ends of contiguous grounding rods and the factor of resistance to drive created by the coupling protruding beyond the surface dimensions of the groundng bar. The invention also introduces economic features in the manufacture of ground rods in eliminating several-of the steps necessary in the preparation of prior ground rods. This saving will be apparent to a machinist skilled in the art. Additionally, laboratory tests have proved that due to the pounding the coupling receives during installation the walls of the sieeves expand so that they do not remain parallel.

The ground rod of the present invention, however, eliminates considerable of the contacting surfaces in any complete assembly of grounding rods. The present invention also eliminates any coupling protrusion and hence facilitates both the driving of the rods and the contact the rods have with the earth. It follows that the present invention also eliminates the carrying of couplings into the field and the matching up of couplings with rods as was previously necessary. The user is given the advantage of convenience and efiiciency of having only one item to carry and assemble. In the prior devices the user had to buy rods, joints and points. These had to be recorded in an inventory, counted out for installations and assembled in the `field. With the present invention there is only one itemthe rod itself.

The present invention also provides extensive contacting areas at the joints to ensure the minimum of electrical resistance to the current carried by the rods in the assembly. It should be noted that except in soldered or welded connections, every surface to surface contact in a conductor of electricity reduces its eiiiciency by adding resistance. The present invention reduces the number of surface contact joints to about one-half as compared with rods that employ sleeves at the joints. An innovation in an electrical conductor that reduces joint resistance by about one-half is significant and particularly important in grounding rods.

It may be said that laboratory tests have proven that in accomplishing all of these desired results there is no accornpanying penalty of loss of mechanical strength, bending characteristics or other attributes as compared with grounding rods now available in commercial practice.

Therefore, according to the present invention an electrical grounding rod assembly comprises a first rod having an end shaped to form a truncated tapering projection, a second rod having an end shaped as a complementary socket to receive said projection in firm self-holding relationship, the contacting surfaces of said rods exhibiting a minimum resistance to the fiow of electric current therethrough, whereby, in combination the outer peripheries of said rods are substantially in alignment and free from protrusions.

The invention will now be more specifically described with reference to the accompanying drawings in which:

FIGURE 1 is a side view showing the manner in which one rod is secured within the socket of the adjacent rod;

FIGURE 2 is a side elevation in cross-section of the invention; and

FGURE 3 is a side elevation bodiment.

FIGURE 1 shows the manner' in ground rods 10 are joined together.

of an alternative emwhich two typical Each rod 10 has eniaose The end of the truncated cone is charnfered or beveled beginning at 20, to give the machined end of the rod the shape of a truncated double cone. The other end of the rod is machined to form a complementary socket 12 which terminates at a drilled point 21. The wall of i socket 12 is tapered to generally conform to the cone 12. At the point 20 at which the chamfer begins, the socket is drilled out to a generally cylindrical shape and to a slightly greater depth than the length of cone 11. Consequently, the lower end of the socket is spaced from the sides and ends of the cone to provide an air cushion. The angle of the sides of the cone 11 should of course be kept with the limits that will form a self-holding taper when assembled in the position illustrated in FIGURE 1, the peripheries 13 of the rods are substantially in alignment. In this Way there is no objectionable coupling or projection to provide resistance to drive into the ground. The simplified rod assembly enables full driving force to be applied to the end of a rod, the only other contact being the surface 14 of the cone 11 on the inner surface of the socket 12. i

There is consequently no difficulty in matching up couplings in the field. The time spent in screwing up the previously discussed coupling is also avoided.

Whereas a eone-shaped projection is preferred it would also be possible to use, for instance, a projection of hexagonal shape as illustrated in -FIGURE 3. The socket `would in this instance be shaped to receive the hexagonal projection 15 in self-holding relationship. This arrangement Would not be objectionable always providing that the peripheries of the assembled rods were substantially in alignment.

As a man skilled in the art will realize that during installation a driving plug is used which has a solid head which fits into the socket of each rod inV succession as it is being driven. Additionally, a specially shaped driving element may be used in the installation process to contact the rods as they are driven. 'Ihis element would have a cone shaped end of hardened steel but since it is not part of the actual invention disclosed this element is not illustrated herein.

Despite the more convenient and less bulky assembly the present invention will take bending such as occurs during installation. =It will also take the pounding driving installation Without splitting the walls of the joints equally as Well as rods having sleeves at the joints.

The need for such a simplified efficient electrical ground rod is therefore clearly apparent.

I clairn: o

An electrical lgrounding rod assernbly comprising a plurality of rod Sections the perpheries of which are substantially in alignment, one of said Sections having a truncated cone end portion, the end of which is charnfered to provide a double cone Shape, another of said Sections having anrend shaped as a complementary socket tapered to conform to the principal taper of said cone, to receive said cone, said socket being spaced by an air gap from the chamfered end of said truncated cone having a Wall of adequate thickness throughout its length to absorb the force of driving in installation, said assembly being of uniform cross-sectional shape and alignment along its length and free from protrusions.

References Cited in the file of this patent UNITED STATES PATENTS 670,470 Cox Mar. 26, 1901 789,021 Hartman May 2, 1905 1,512,786 Morton Oct. 21, 1924 1,976,264 Miner Oct. 9, 1934 2,157,180 Little May 9, 1939 2,186,482 Frank Ian. 9, 1940 2,407,723 Pe'trie Sept. 17, 1946 FOREIGN PATENTS 337,617 Great Britain Nov. 6, 1930 473,618

Canada May 15, 1951V

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