US2020390A - Shunt for electric blasting caps - Google Patents

Description

Nov. 12, 1035. w, MLSON 2,020,390

SHUNT FOR ELECTRIC BLASTING CAPS Filed Nov. 1, 1932 CED/45'6" (Y/q/ao 6: 77775017 INVENTOR.

BY Q64 I A TTORNE Y.

Patented Nov. 12, 1935 UNITED STATES- smm'r son nnnc'rarc BLASTING cars Waldo 0.. Wilson, Wilmington, Del., assignor to E. I. du Pont de Nemours &.Company, Wilmington, Del., a corporation of Delaware Application November 1, 1932, Serial No. 640,608 11 Claims. (Cl.-102 10) This invention relates to an improved electric blasting cap assembly, and more particularly toa means for short-circuiting the leading wires of blasting caps to protect the caps from firing by accidental contact of the wires with stray currents or other electric charges during transportation or handling preliminary to actual firing of the detonators to which the leading wires are connected.

Blasting caps consist generally of cylindrical containers, of metal or other suitable-material,

containing one or more explosive charges capable of sudden and violent explosion under the action of suitable initiating means. In the case of electric blasting caps, the ignition of the explosive is brought about electrically by passing an electric charge through or into the cap. For this purpose two leading wires pass into the cap shell, insulated one from the other and from the shell wall, and the wires are connected by a bridge wire of small diameter. This bridge wire passes through the ignition charge in the cap and, when brought to incandescence by the passage of the electric current, causes the firing of the cap.

The leading wires of electric blasting caps are of considerable length, varying generally from- '4 to 20 feet, and are covered with insulating material throughout. their length, except several inches of the free end portions of the wires which are left bare in order to facilitate making the proper connections with a source of electric current after the caps are placed in position .for fir- The presence of these uninsulated end portions of the wires has always presented a considerable hazard during transportation and handling of the blasting caps both out of and in the mines, because of the possibilities of these exposed ends coming in contact with electric circuits or stray currents in the vicinity of blasting operations. This is particularly true in-mim'ng operaftions where the workmen frequently carry the blasting caps to the place of use with the ends of the wires draggin on the ground and accidentally contacting with objects charged with electricity.

Various methods and means have heretofore been suggested for overcoming these disadvantages and safeguarding against the accidental discharge of electric blasting caps prior to placing the caps in the main explosive charges for properly controlled detonation. One method and means has comprised short-circuiting the leading wires by twisting the bare ends together for a short distance at the termination of the insulation, including preferably a portion of the uninsulated as well as a portion of the insulated wires, so that, in case of contact of the bare ends with an electric circuit or an electrically charged object, a shunting action will result and insuiiicient current will pass through the blasting cap to cause firing. While this means and method has given considerable satisfaction, it has the disadvantage that the wires when once twisted and then untwisted are slightly distorted so as to make them more diflicult to connect as efiiciently with the firing circuit. a

. Other attempts to accomplish this same result have been made, principally by means of clips .of' m one form or another which are placed on the bare wires to hold them-in contact with one another, but these have in general been unsatisfactory because of the difliculty of removing them from. the wires after the blasting caps are in place for firing u blasting charges, and have the further. disadvan-- tage that the clips are sometimes spaced suflicientlyfar-from the termination of the insulation that stray currents may contact the'bare wires between the ends of the insulation andthe clips pr 20 the junction of the bare wires and thus defeat the primary purpose of the clip.

An object of this inventionis to provide a more efiicient and satisfactory means for safeguarding a the handling and transportation of electric blasting caps. A further object of my invention isto provide a short-circulating device that ngt'only properly contacts the bare wires of blasting caps but at the same time is capable of protecting that-- portion of the wires between the point of contact" and the ends of the insulation. A still furtherobject is such ameans which causes no bending or distortion of the bare ends of the wires and at th same time can be easily removed. Other and further objects will present themselves as the description of the invention proceeds, wherein;

Figures 2, 4, 6, 8, 10 and 12 are perspective views of the various modifications of my inven-- tion: Figures 1, 3, 5, 7, 9 and 11: are plan views of the blanks from which the clips are formed by bending. Fig. 13 is a perspective assembly view of one form of my invention applied to the lead wires of an electric blasting cap.

These objects are accomplished by the following invention in which I have found that a suitable shunting means for this purpose maybe constructed from a resilient piece of conductive metal comprising a main section having diametrically opposed projections positioned .to press firmly 50 against each other to engage the bare ends of the wires that. are inserted through an. opening in the main section. This is so constructed that the bare ends of the wires are adapted to protrude electric blasting cap with certainty in case the bare ends of the cap wires come into contact with any electric charge so long as the shunting device remains-attached to the wires. This device may also be used for twisting the wires together at a point about the termination of the insulated portions to effect a greater security against premature detonation of the blasting caps to which the wires are attached. This may be accompli sh'ed by holding the wires in one hand while rotating the device with the other hand, or vice versa, using the wires as an axis.

While I have described the broad fundamental principles of my invention in the foregoing, it may be embodied in various specific modifications, some of which are described below with reference to the accompanying drawing.

Figure 1 shows a strip of metal suitable for working or shaping into final form to comprise serted therein. These end portions may,

one of the embodiments of my invention. Figure 2 represents a view in elevation of the completed device ready for attachment to the'leading wires. In these figures D represents an opening through that portion of the metal plate A forming the base. Sections B B form the outer sides of the resilient projections. While these side portions may meet as substantially straight surfaces at their ends I preferably bend them inwardly upon themselves in the form of a loop in order to provide vise-like jaws to grip the bare wires inof course, be bent outwardly to form similar loops but I prefer the form illustrated in the drawing, 'so as to facilitate the insertion of the shunt upon the wires. In utilizing the invention in actual practice, the uninsulated ends of the leading wiresare thrust through the hole D and thence between the contacting resilient elements CC 'sufliciently far that the termination of the insulated portion is within the shunt between the opening D and the point of contact 'of the resilient elements so that that portion of the wires between the points of contact and the insulation may not come into contact with stray currents or other charges of electricity.

In place of bending the end portions of the resilient elements inwardly to form a loop as shown in Figure 2, these ends may, of course, be bent inwardly only sufliciently far to permit the inner faces to contact as flat surfaces against each other. These surfaces may also be roughened or slightly corrugated so as to prevent sidewise movement of the wires. Another modification of my invention is shown in Figures 3 and 4 in which two metallic side pieces or shields EE' are included which are bent into a plane perpendicular to the base A.

The principal advantage of this modification is that these side portions E-E' prevent sidewise movement of the ends of the bare wires and prevent them from slipping out of the contacting resilient elements of the shunt as well as further preventing that portion of the bare wires between the opening D and the jaws of the vise from coming into contact with pointed or other electrically charged objects.

A further modification of this invention is illustratedin Figures 5 and 6, Figure 5 illustrating a T section of metal, while Figure 6 illustrates the 5 finished shunt. It will be noted that Figure 4 is similar to Figure 1 except for the additional portions F and G. In this modification the portions F-G are bent into a plane perpendicular to A and then G is bent over in a plane'parallel to the 10 base A before the sections B-B are bent up wardly to form the vise-like jaws by means of the loop portions CC'. With the section G horizontally positioned above the base A, the opening D' will register with the opening D in the base. 15 This provides a-guard which aids in maintaining the wires in direct alignment and assists thejaws, in combination with the base A, in securely protecting the wires, as well as preventing'sidewise movement. The wires are shunted in the 20 same manner as described in Figure 1 byinserting the bare wires first through openings D-D' and thence through the jaws of the vise so that a substantial length of the bare portions protrude.

A still further modification of this invention is 2'5 illustrated'in Figures 7 and 8, which resemble Figures 1 and 2, except that the portions CC' are omitted. In this modification the sections B-B' are slightly longer and are bent upwardly and inwardly to form a triangle with the base sec:- 86 tion A. The outer edges of the sections B-B may be left smooth or may be provided with jagged or tooth-like contacting surfaces H-H' so that the wires may be securely held in place against sidewise movement. e 7 Figures 9 and 10 illustrate another modification of my shunting means similar'to that shown inFigures 1 and2but withguardsonthe resilient end sectionsC-C' which are bent over into the position shown to aid in preventing ,the 40' bare wires from working out of or being pushed out of the gripping elements of the shunt during handling of the blasting capequipped with this shunting means.

ment when the shunt is in place.

Figure 13 illustrates an assembly of an electric 5:) blasting cap and this novel shunting device. The detonating cap is dted I! having two leading wires NN' with the wires stripped of the insulation neartheir ends as shown at 0-0. In thisfigure the bare ends have been through the opening D of the base A and, to a substantial extent of their length, through-the gripping elements C-G' so that the termination of the insulation is within the shunt, while the bare wires are short-circuited against premature 0 detonation of the cap. The modifications illustrated in the other figures of the drawing are similarly attached.

It will be apparent from the foregoing that various embodiments of my invention exist and may 65 through which the leading wires are adapted to protrude with the bare'ends secured in the vise, and a guard for the wires.

2. In an electric blastingcap a shunting device of resilient conductive material for short-circuiting the leading wires comprising a main or base section, diametrically opposed contact members secured thereto and forming a vise at'their point of juncture, an opening in the main section through which the leading wires are adapted to protrude with the bare ends secured in the vise, and a guard intermediate the base member and the contact members to prevent lateral movement of the wires.

3. In an electric blasting cap a shunting device of resilient conductive material for shortcircuiting the leading wires comprising a main or base section, diametrically opposed contact members secured thereto and forming a vise at their point of juncture, an opening in the main section through which the leading wires are adapted to protrudewith the bare ends secured in the vise, and a guard in spaced relation with the base member. I

4. In an electric blasting cap, a shunting device of resilient conductive material for shortcircuiting the leading wirescomprising a main or base section, diametrically opposed contact members secured thereto and forming a vise at their point of juncture, an opening in the main section through which the leading wires are adapted to protrude with the bare ends secured in the vise, and a pair ofv guards substantially vertical to the base or main section.

5. In an electric blasting cap, a shunting deviceoi resilient conductive -material for shortcircuiting the leading wires comprising a main or base section, diametrically opposed contact members secured thereto bent'into triangular position and forming a vise at their point of juncture, an opening in the main section through which the leading wires are adapted .to protrude with the bare-ends secured in the vise, and a pair of guards extending across the open sides of the triangle.

6. The device of claim 2 in which the guard is spaced from the base ormain section but is substantially in parallel relation therewith, and an opening in the. guard registering with the opening in the main section.

7. In an electric blasting cap, a shunting device of resilient conductive material for shortcircuiting the leading-wires comprising a main or base section, diametrically opposed contact members securedthereto and forming a vise having a jagged or irregular surface at their point of juncture, and an opening in the main section throughwhich the leading wires are adapted to a. In an electric blasting cap, .5. shunting device of. resilient conductive material for shortcircuiting the leading wires comprising a main or base section, diametrically opposed contact members secured thereto and forming a vise with 5 a roughened-surface at-their point 01' juncture, and an opening in the'main section through which the leading wires are adapted to protrude with the bare ends secured in the vise.

9. The combination with a detonator, the individual bifilar lead wires of which have a covering of insulated material thereon for a portion of their length outwardly and being bare therebeyond, of a shunt of resilient conductive mate rial for short-circuiting the leading wires comprising a portable main or base section, diametrically opposed resilient elements secured thereto and having a tendency to firmly contact at their outer ends, andan opening in the main section through which the leading wires protrude with the bare'cnds secured between the esilient elements, so that the point where the i sulation terminates and the bare portion be- .gins lies between the main or base section and the resilient contact elements. 10. The combination with an electric detonatorand its lead wires, said lead wires being bare for a portion of their length at the outer ends with the bare ends secured between the resilient 40 elements, so that the point where-the insulation terminates and the bare portion begins, lies between the main or base section and the resilient contact elements. Y

11. The combination with an electric detonator and its lead wires, saidwires having a substantial protrude with the bare ends secured in the vise.

portion thereof covered 'byinsulating material and the portions near their outer ends left bare, of a portable shunt of resilient conductive material for short-circuiting the leading wires comprising a .main or base section having an opening therein through which the leading wires are inserted, and diametrically opposed resilient elements secured to the base section and engaging the bare portion or the wires, so that the oint?! where the insulation terminates and the bare portion begins,v lies between the main or base section and the resilient contact elements.

- WALDO C. WILSON.-

CERTIFICATE OF CORRECTION.

Patent No. 2;020,39o. November 12, 1935.

WALDC C. WILSON.

It' is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, second column, line '12, for "vise-like jaws" read contacting portions of the resilient elements; and line 25, for "jaws of the vise" read contacting resilient elements; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office. D

Signed and sealed this 28th day of January, 'A. D. 1936.

Leslie Frazer (Seal) Acting Commissioner of Patents.

CERTIFICATE OF CORRECTION.

Patent No. 2,020,390. November 12, 1935.

wALDo c. 'wILson.

It' is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, second column, line -12, for "vise-like jaws" read contacting portions of the resilient elements; and line 23, for "jaws of the vise" read contacting resilient elements; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office. 7

Signed and sealed this 28th day of January, it. D. 1936.

Leslie Frazer (Sea1) Acting Commissioner of Patents.

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