US1606414A - Protecting device for electric detonators - Google Patents

Description

Nov 9,1926. 150mm H. L. GRANT PROTECTING DEVICE FOR ELECTRIC DETONATORS Filed NOV. 20. 1925 nvamkoz flarry Z Grarzi,

Patented Nov... 9, 1926.

UNITED STATES PATENT OFFICE.

HARRY I. GRANT, OF TAMAQUA, PENNSYLVANIA, ASSIGNOR TO ATLAS POWDER COMPANY, OF WILMINGTON, DELAWARE, A CORPORATION OF DELAWARE.

PROTECTING DEVICE FOR ELECTRIC DETONATORS.

Application filed November 20, 1925. Serial No, 70,365.

This invention relates to a protecting de-,

vice for electric detonators of. the character of that shown in my copending application, SeriaLNo. 748,214, filed on November 6, 1924. I l Like the device of the application referred to, the protecting device of the present invention is intended to be applied to the lead-in wires of electric detonators and to serve, while in position, to establish a short circuit between thetwo lead-in wires,

so that any stray currents imposed upon the lead-in wires,-outwardly of the point of application of said device, may not find their way to the detonator and prematurely explode the same and so that no difference in potential can be created between the said wires, inwardly of the point of application of the device under the influence of accidental or stray currents imposed upon said wires.

I am aware'of the fact that it has been proposed to short circuit the main firing cable leading from the blasting machine. However, that method is of utility only at the time of use. An important object of the present inventionris to provide a structure which will be operative with respect to the individual detonators, at all times between the time of manufacture of the detonator and until the same is actually exploded on the job, the structure being of particular utility during the time that the detonator is being transported and while it.

is being handled about the work preliminary to the actual connection of its lead wires to the main firing cable.

The present application is directed to the protection of a specific form of short circuiting shunt and method of applying the same to the lead-in wires of the individual blasting caps, with its inner end abutting and resting firmly against the terminal end the usual insulation of the detonators. the provision of a structure of this character, which is used only once and then thrown away, it is of importance that it be of a simple and inexpensive nature and one adapted to be applied rapidly by automatic 1nachinery-.- With this end in view, I have devised the shunt shown in the accompany' ing drawing wherein:

Fig. 1 is a side elevation of a detonator having the shunt applied thereto,

Fig. 2 is a transverse sectional view of In.

through the shunt after the insertion of the Wises but before compression of the shunt an Fig. 3 is a view like Fig. 2 after compression of the shunt.

Like numerals designate corresponding parts in all of the figures of the drawing.

Referring to the drawing, 5 designates the conventional electric detonator and 6 and 7 designate the usual lead-in wires of said detonator.

In the ordinary use of the detonator the flow of current of sulficient strength pastan igniting element 8, which connects the inner ends of the wires 6 and 7, explodes the detonator. The lead-in wires are insulated, as indicated at 9 and 10, for some distance from the detonator and the ends of the leadin wires are left bare beyond the point where the insulation terminates, to adaptthem for ready application to the firing cable, leading from a blasting machine.

The short circuiting shunt of the present invention comprises a block 11, of lead, copper, aluminum or any other suitable conductive material. This block is grooved along its opposite edges as indicated at 12, 12 for the reception of the wires 6 and 7. The grooves may be made of such size with respect to the diameter of the wires, that the wires will frictionally wedge or bind therein, after having been once forced into said grooves. I prefer, though, to compress the material of the block, firmly into engagement with the wires, after the insertion of the latter in the grooves, so that accidental dislodgement of the shunt during shipment or handling will be impossible.

When the time of use of the detonator arrives, the shunt may be removed byv stripping it longitudinally from the lead wires 6 and 7 This stripping action not only removes the shunt but cleans and brightens the 1 exposed ends of the wires so that they will make a good electrical connection with the main firing cable of a blasting machine.

It is apparent that as long as the shunt is in place, a short circuit is created between wires 6 and 7 at its point of application, so that diflerences in electrical potential be- .tween said wires will not be effective to explode the detonator. Since the shunt abuts the insulation 9 and 10, it follows that the detonator is completely protected at all points. It is not to be understood that the device is of utility only when actually touching the termination of the insulation. It will give a very appreciable measure of protection even when spaced somewhat from the insulation because the influences which might bring about such difference in potential between the lead wires as to explode the detonator, are not those sought to be created by an intelligent human agency but only those which might accidentally occur.

, Stray currents of such low E. M. F. as to escapeordinary notice constitute a marked source of danger and are rendered absolutely harmless by this invention.

It is to be understood that the invention is not limited to the precise construction set forth but that it includes within its purview Whatever changes fairly come within either the terms or the spirit of the appended claims.

Having described my invention, what I claim is:

The combination with an individual electric detonator and its bifilar lead wires, said lead wires having their inner portions cov- In testlmony whereof he afiixes his sig- 7 nature.

HARRY L. GRANT.

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