US1603048A - Protecting device for electric detonators - Google Patents

Description

Oct. 12 1'926. 1,603,048 V H. L. GRANT PROTECTING DEVICE FOR ELECTRIC DBTONATORS Filed Nov. 20, 1925 awue/nfoz flarry l. Grant,

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HARRY L. GRANT, OF TAHZAQUA, PENNSYLVANIA, ASSIGNOR TO ATLAS EGW'DER CGIVL IANY, OF WILI/IINGTQN, BELAW'ARE, A CGRPDRATIQN 0F DELAXVARE.

PROTECTING DEVICE FOR ELECTRIC DETONATORS.

Application filed November 2'0, 1925. Serial No. 70,364.

This invention relates to a protecting device for electric detonators of the character of that shown in my copending application, Serial No. 748,214, filed on November 6, 19%.

Like the device of the application referred to, the protecting device of the present in vention is intended to be applied to the lead-in wires of electrical detonators and to serve, while in position, to establish a short circuit between the two 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 of potential can be created between the wires inwardly of the point of application of the device under the influence of accidental or stray currents.

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 invention is 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 eX- ploded 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, preferably with its inner end abutting and resting firmly against the terminal end of the usual insulation of the detonators. In 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 machinery. l Vith this end in view, I have devised the shunt shown in the accompanying drawing wherein:

Fig. 1 18 a perspective vlew of the short circuiting shunt the same,

Fig. 2 is a side elevation of a detonator with the shunt applied thereto,

Fig. 3 is an end view of the shunt after being applied, and

Fig. 4 is a longitudinal sectional view through the shunt, after application.

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 sutficientstrength past an igniting element 8, which connects the inner ends of the wires 6 and 7, explodes the detonat'or. 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 adapt them for ready application to the firing cable, leading from a blasting machine.

To provide for the rapid and economical application of a shunt to the lead-in wires 6 and 7 of the detonator, I provide a tubular body 11 and thread the lead-in wires through this body and then compress said body firmly about the wires and into the form of a block. The body 11 may be formed of lead, copper, aluminum or any other suitable conductive material and it is usually applied to the leadin wires in such manner that the inner end of the resultant block abuts snugly against the outer end of the insulation, 9 and 10, of the wires. It is not to be understood that the device is of utility only when actu ally touching the termination of the insu lation. 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 escape ordinary notice constitute a marked source of danger and are rendered absolutely harmless by this prior to the application of said wires do not touch each other. Thus great care 1D the positioning of the wires,

during the application of the body 11, is rendered unnecessary and the short circuiting shunt may be applied rapidly and upon a commercial scale. The tubular shunts may be rapidly made by severing. them from a long tube of the proper metal.

lVhen the short circuiting shunt is to be removed at the time of use of the detonator, it is stripped longitudinally from the wires 6 and 7. from the wires cleans and brightens them and insures a good electrical union between said wires and the firing cables towhich they are to be attached. To facilitate the cleaning action 01 the shunt as it is stripped from the Wires, I cut the end of the tubular body 11 squarely across to render the contacting edges of said body, which engage the wires, as sharp as possible, so that in the stripping action they will exert a scraping The act of stripping the shunt effect upon the lead wires of the detonator.

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

Having described my invention, what I claim is:

1. The combination with a detonator and its lead wires, said lead wires having their inner portions covered with insulating ma terial and their outer portions left bare, of an electric shunt comprising a body of conductive material of tubular form through which the bare portions of the wires have been threaded and which body has been compressed about said wires, with its inner ends abutting the outer ends of the insulation.

2. A structure as recited in claim 1 Wherein the. outer end of the, tubular body is shaped to constitute a scraping edge when the shunt is stripped longitdinally from the- Wll'QS.

In testimony whereof he aiiines his s1gnature.

HARRY L. GRANT.

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