US2717551A

US2717551A - Method of protecting electric blasting caps

Info

Publication number: US2717551A
Application number: US195974A
Authority: US
Inventors: Charles M Blackburn; Frederick R Seavey
Original assignee: Olin Corp
Current assignee: Olin Corp
Priority date: 1950-11-16
Filing date: 1950-11-16
Publication date: 1955-09-13
Anticipated expiration: 1972-09-13

Description

Sept. 13, 1955 c. M. BLACKBURN ET AL 2,717,551

METHOD OF PROTECTING ELECTRIC BLASTING CAPS Filed Nov. 16, 1950 DNVENTORSZ CHARLES M. BLACKBURN FREDERICK R. S AVEY "7 ATTORNEYS.

United States Charles M. Blackburn and Frederick R. Seavey, Alton, Ill., assignors to Olin Mathieson Chemical Corporation, a corporation of Virginia Appiication November 16, 1950, Serial No. 195,974

1 Claim. (Cl. 10228) This invention relates generally to electric blasting caps, and particularly to the treatment, prior to packaging, of the terminal portions of the lead wires for such blasting caps.

The ordinary electric blasting cap of commerce is provided with long lengths of lead wire, the free ends of which are adapted to be connected into the firing circuit when the blasting cap is placed in position to detonate explosive.

In the packaging of electric blasting caps for shipment and handling, it is important to protect the cap from the possibility of accidental detonation which might occur by virtue of the lead wires coming in contact with stray electric currents and other sources of electrical energy. Protection of the caps in this respect involves shunting or otherwise temporarily, i. e., for the duration of the shipping and handling process, electrically connecting together the respective lead wires near their free ends, as well as the provision of an insulating cover about any naked portions of the wire.

The object of the present invention, generally stated, is to provide a method of treating the lead wires of electric blasting caps and packaging the same whereby to protect the device in shipment and to facilitate its connection into a firing circuit.

Another object of the invention is to provide an electric blasting cap wherein, as the shunt is removed, the lead wires are bared of insulation at their terminal portions.

Other objects will become apparent to those skilled in the art when the following description is read in connection with the accompanying drawings, in which:

Figure 1 is a view in side elevation of apackaged electric blasting cap constructed in accordance with the present invention, part of said package being shown in section to reveal the relationship of the several parts;

Figure 2 is an enlarged detail view showing the free ends of the lead wires of the blasting cap shown in Figure 1;

Figure 3 is an end view of the shunting device shown in Figure 1;

Figure 4 is a view corresponding to Figure 1, but showing a different embodiment of the invention; and

Figure 5 is an enlarged detail view of the free ends of the lead wires treated as shown in Figure 4.

The present invention contemplates that the lead wires of the usual electric blasting cap have their free ends treated so that the insulation covering the terminal two or three inches is severed from the insulation covering the balance of the wires, and the terminal portion slightly separated from the main portion by slipping the separated piece lengthwise of the wire so that the separated portion overhangs the end of the conductor. A gap between the terminal portion of insulation and the main portion of insulation is thus formed whereat the conductors within the lead wires are bare. The invention contemplates that the lead wires be electrically shunted at said gap, and this may be accomplished by engaging the two bared conductors and suitably but temporarily securing them in enatent C) gagement, or by applying an auxiliary conductive clip to the bared conductors at said gap. In either event, it is desirable to surround the connection between the bared conductors with a protective member of non-conducting material in order to prevent contact with live electrical parts.

the member holding the wires together may be gripped and slipped endwise of the wirestoward their free end-to straight, as used in connection with the terminal por tions of the lead wires in this specification and the appended claims, is not used in its geometric sense, but rather connotes the freedom from kinks or abrupt turns or bends, which would interfere with the free slipping of the original insulation covering from the wires.

Referring now to Figures 1, 2, and 3 of the drawings for an illustrative embodiment of the invention, an electric blasting cap 1 of any suitable construction is provided with apair of lead wires 2 and 3, which are of substantial length and coiled about a tubular spool 4 in amanner well known to those skilled in the art.

The lead wires 2 and 3 are of the type generally employedv in the art wherein a conductor strand is encased. in insulation, which may be plastic, rubber textile, I or any other suitable material, severed increments of which retain a tubular form;

The invention contemplates that the free ends of the lead. wires 2. and 3 be treated so as to separate. the insulation at the terminal portions thereof from the insulation upon the balance of the wires. 'The operation is shown most clearly in Figure 2. The two or three inches of lead wire at the extremities thereof is herein referred to as the terminal portion, by which is meant the. portion of the wire usually stripped of its insulation in. order to make the electrical connections into the firing; circuit. Between the terminal portion and the main portion of the. lead wires, the insulation is cut, as for example, at lines 5 and 6 of wires 2 and 3, respectively. The cutting operation may be accomplished with any of the well known tools available for the purpose, but is preferably done in such manner that the conductor element within the lead wires is not mutilated. The lines of cut 5 and 6 permit the short sections of insulation 7 and 8 about the terminal portions of wiresv 2 and 3, respectively, to be slipped lengthwise of the wires, thus forming a gap 9 between the shoulders of insulation formed by the cuts 5 and 6 between the main portions of insulation and the terminal portions 7 and 8. At the gap 9, the conductor within lead wire 2 is bared of insulation, as shown at 10, and the conductor within lead wire 3 is bared of insulation, as shown at 11. When the portions of insulation 7 and 8 are slipped lengthwise as above indicated, the ends thereof overhang and thus protect the tips 12 and 13 of the conductors within the lead wires 2 and 3, respectively. As above indicated, it is desirable to maintain the conductors within the terminal portions of insulation 7 and 8 straight.

After the insulation on the terminal portions of the lead wires 2 and 3 has thus been separated from the insulation on the main portions thereof, the wires are connected together at

sections

10 and 11. As shown in Figures 1 and 3, the connection takes the form of a split metallic cup 14, which is fitted Within spool 4. The cup 14 has its bottom split to provide two

spring members

15 and 16, which will yield sufiiciently to per- Patented Sept. 13, 1955 Furthermore, it is desirable to form the connection. between the lead wires at the gap in such manner that mit the lead wires to be passed therebetween. As shown in the drawings, the

parts

15 and 16 are flared in a direction such that the force exerted incident to forcing the tip of the lead wires inwardly therethrough readily separates the

parts

15 and 16, but the reverse movement tends to draw said parts together. The terminal portions of the lead wires are passed through cup 14 so as to lie on the interior of spool 4 with the

parts

15 and 16 engaging the bared conductors at 10 and 11. Thus, when the cup 14 is formed of conductive material, the lead wires are thereby electrically shunted.

The extremities of the lead wires may be passed through the cup 14 before the latter is inserted in spool 4, or afterwards, as is desired, it being unnecessary to rigidly secure the cup 14 within the spool 4. When the user is readyto connect the lead wires 2 and 3 into the firing circuit, the spool 4 may be gripped in one hand in such manner that a thumb or forefinger prevents withdrawal of cup 14 from the interior of the spool. With the adjacent portions of lead wires 2 and 3 gripped in the other hand and pulled in the withdrawing direction, it isevident that the tips of

spring members

15 and 16 will engage the shoulder formed on terminal portions 7 and 8 of the insulation by cuts 5 and 6 and prevents the latter from being withdrawn concurrently with the lead wires. Hence, as the wires are withdrawn, the terminal portions of insulation 7 and 8 are completely removed from the conductors therein contained and, as the wires are' withdrawn from the spool 4, they are ready for connection into the firing circuit without any further treatment.

In the embodiment shown in Figures 4 and 5, the lead wires 2 and 3 are treated in the same manner as described above with reference to Figure 2, so as to provide terminal portions of insulation 7 and 8 spaced from the main portions of insulation on wires 2 and 3. In this embodiment, however, the electrical connection of the lead wires at the gap between the two separated portions of insulation is accomplished by bringing the wires into physical engagement with each other at the aforesaid gap. With the wires in physical contact, the same may be temporarily fastened together in any suitable way, as for example, by tying them with a string, thread, or ribbon, or by applying a sticker, clip, or clamp, so as to maintain the bared parts in electrical connection during the process of shipping and handling. As shown in the drawings, the bared sections of conductor are held in contacting relation by being bound by a layer of non-conductive thread 20. The non-conductive thread 20 not only assures the maintenance of electrical contact between the two conductors, but prevents contact therewith of live electrical parts. The invention is,

however, not limited to the utliization of non-conductive material for connecting the parts together in this manner, but, when conductive material is utilized for this purpose, it is desirable to tuck the terminal portions of the lead wires, including the binding 2% into the interior of spool 4, in contrast to the exterior position shown in Figure 4. Moreover, when the tie is of conductive material, it is unnecessary to hold the bared sections of wire in physical contact with each other.

When it is desired to connect the blasting cap into its firing circuit, the binding 20 may be gripped between the thumb and forefinger of one hand, while the main portions of the lead wires are gripped in the other hand, and the two drawn apart, thus concurrently stripping the lead wires 2 and 3 not only of the binding 21), but of the terminal portions of insulation 7 and 3. Thus in both embodiments the outer ends of the lead wires are protected by the overhanging insulation, the bared increments are electrically connected together, and the latter are protected from contact with live electrical members either by being enclosed within the spool 4, or by being wrapped with non-conductive material 20.

From the foregoing description those skilled in the art should readily understand the construction, operation, and advantages of the invention. piete embodiments have been disclosed in detail and other alternatives suggested, it is not to be understood that the invention is limited to the details described. On the contrary, it is to be distinctly understood that the foregoing disclosure is merely for illustrative purposes, and

that such modifications and variations thereof as do not depart from the spirit of the invention are contemplated by and within the scope of the appended claim.

Having thus described the invention, what is claimed and desired to be secured by Letters Patent is:

The method of protecting electric blasting caps having insulated lead wires which comprises making a cut through the insulation on the lead wires to separate the insulation on the terminal portions of the lead wires from the insulation on the remainder of the wires, slipping the separated terminal section of insulation endwise of the wires to bare a short increment of wire, all without removing the insulation from the wires, and, with the separated section of insulation overlapping the ends of the wires, electrically short-circuiting the bared increments of the lead wires, and packing the caps with the short-circuited increments enclosed by non-conductive material.

References Cited in the file of this patent UNITED STATES PATENTS 1,983,141 McFarland Dec. 4, 1934 2,062,189 Olin et a1 Nov. 24, 1936 2,218,170 Hunt Oct. 15, 1940 2,649,735 Feild Aug. 25, l953 FOREIGN PATENTS 336,423 Great Britain Oct. 16, 1930 While two com-