US970693A - Ground-connector. - Google Patents

Description

J. L. DONALD. GROUND CONNECTOR. APPLIOATIOH rmm mm. 19, 1908.

Patented Sept. 20, 1919'.

cuit branches and connections.

JAMES L. DONALD, OF MOORESVILLE, NORTH CAROLINA.

osouun-oon'nncron.

Specification of Letters Patent.

Application filed December 19, 1908.

Serial n6. 3

"i atented Sept. 20, 1910.

see, as.

Ground-Connectors, of which the followingis a full, clear, and exact description.

My invention relates to a ground connector, particularly for use in conduit wiring.

"it isa usual practice to run the circuit wires for lamps, motors and other electrical appliances through -'conduits of ordinary iron piping, interrupted at intervals by the switch, outlet and junction boxes forthe cir- .The main object of this arrangement is to provide ah solute protection against fire, it being evident that any grounds or short-circuite n the circuit wires can do no damage if they are entirely inclosedin a wrought iron pipe. But in order to make the protection com plete and adequate, it is evident that the pipev must be thoroughly grounded at all points, so that grounds or short-circuits from the interior circuit Wires or from any exterior conductor, will not electrify a portion of the length or the pipe to a sparking or arcing potential by reason of any poor or inadequate ground connection of such pipe section. it IS evident thatsonie means must be provided for insuring a low resistance path to ground from every portion of the conduit pipe, in case the latter is to.be any real protection against fire a; l. other damage, due to grounds or short-circuits of the interior circuit wires, or any exterior charged conductor. J l V g It s the purpose oi my invention to provide a very simple and eliicient means for this urpose/ i 1th this object in view, my invention consists in the features of construction and combination as hereinafter set. forth and claimed.

In the drawings: Figure 1 is a view'showing the general features of an ordinary conduit wiring system embodying the principles of my invention; liig. 2 is a perspective view (if one of the grounding applizinc-es, and Fig. 3 is a detail sectional View of the same.

Referring to the drawings: 1 designates sections or portions of an ordinary conduit, pipe, and Qdenotes an outlet, switch or.

junction box of the type ordniamyflenr ployed and to which the pipe sections 1 aret'hreaded, either directly or through any iuteriuediute bushings (not shown). The boxes are ordinarily made of stamped sheet metal and have such thin walls that a good direct threaded engagement with the pipe sections is ditlicult to secure. Where connecting bushings of some sort are em- 6!, ploycd, a suliici'ently good mechanical connection is made between the pipe sections and the switch boxes, but the electrical connection is very inferior. If the sheet metal of the switchuhoxes is oxidized, as is the usual case, it may happen that the pipe is practically insulated from the boxes altogether. Under' these circumstances, a short on such pipe section would immediately dangerously elevate its potential.

In carrying out my invention to overcome the foregoing diihculties, I make use of the fact that the ends of the pipe sections,where theyjoin the switch or outlet boxes, are nec-. essarily threaded with usuai pipe threads. The ordinary pipe thread is slightly tapering or (:oniwl, which fact has an important hearing in my invention. 1 provide stamped sheet metal collars 3, of brass or copper with t alug ion one side.and inieriorly threaded at 5 to fit standard pipe threads. These collars will, of course, be stamped in diil'ercnt sizes corresponding to different sizes of conduit piping ordinarily employed. They are most conveniently punched. out of 3/16 or .1/4 sheet brass or copper, and then merely interiorly threaded, whereupon they are ready to be assembled upon the threaded section of the pipe, without any further machining or finishing processes to insure perfect lit. The

lateral lug i should, however, be drilled with a hole 6 of sufficient size to receive a stout copper wire, and the interior of this hole is conveniently tinned at 7 to facilitate soldering such copper wire integrally to the lug.

The use and operation of the invention will be clear from the drawings.

It is merely necessary to assemble the collars 3 upon the threaded ends of the pipe sections 1 adjacent to the connections of these pipe sections to the various outlet, switch and auction boxes. Short lengths of copper Wire 8 are then soldered to the collars on opposite sidesof the various boxes, thereby bonding the various p pe sections to- 0 gether in a continuous low-resistance circuit.

At some point a pipe 9 may be driven into the 011ml, or otherwise arranged to make a manner as the various sections 1 arebond-' ed to one another. Each collar ma-kes aperfect electrical connection-with itspipe section, partly because it is of suflicientthickness. to make a good threaded engagement therewith, and partly because of the fact that it can be screwed back upon the tapered threads of the pipe section as far as the strength of the workman will permit, brightening up the surfaces of the threads by the friction, and insuring a high pressureand 00d electrical contact-between the engagmg metallic surfaces. The bond wires 8 be- 'ing soldered to the respective collars, make v a substantially perfect electrical connection therebetween, so that the entire conduit pipe length is bonded into a very "perfect low f "evcgees resistance grounded circuit. capable of carrying off heavy current, without undue rise of potential at any point.

comprising an integral metal collar interiorly pipe threaded for engagement with a pipe end, the pipe thread by reason of its taper affording especially good electrical ground 'eonnector for conduit Wiring 25 connection between said collar and )ll)!...Stll(l collar further being provided with an integral laterally extending 111;; having a lined aperture therein foiztlic reception of a connecting wire.

In Witness whereof, I subscribe my signa-. 3

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