US 2532770 A
Description (OCR text may contain errors)
Dec. 5, 1950 D. D. HUYETT ASSEMBLY OF ELECTRIC EXPLOSION mrrmons Filed May 10, 1946 Fig.5
Daniel D. Huyen,
IN V EN TOR. B
Patented Dec. 5, 1 950 ASSEMBLY OF ELECTRIC EXPLOSION INITIATORS Daniel D. Huyett, Wilmington, Del., assignor to Atlas Powder Company, Wilmington, Del., a
corporation of Delaware Application May 10, 1946, Serial No. 668,979
This application relates to electric explosion initiators.
An object of the invention is the provision of an improved method for manufacturing leg wire and plu assemblies for electric explosion initiators.
Another object of the invention is the provision of a method for manufacturing highly waterresistant leg wire and plug assemblies for electric explosion initiators.
A further object of the invention is the provision of a method for manufacturing highly water-resistant electric explosion initiators.
Other objects will appear from the following description.
Electric explosion initiators such as electric detonators and electric squibs are usually made in the form of tubular shells closed integrally on one end, charged with explosive, and closed on the other end by means of plugs through which run leg wires. To provide adequate protection forv the explosive it is important that the plugs be water-resistant and that they join the shell walls and embrace the leg wires in sealing engagement.
While closure plugs have been made from many different substances, rubber like materials have found cons'derable application for this purpose largely because of the ease with which they may be crimped into initiator shell mouths to provide water-proof shell-to-plug seals.
Several different methods have been proposed for sealing leg wires into rubber-like plugs. According to one method, wires coated with a sealing material such as rubber cement are threaded through bored plugs. It has been found difficult, however, to obtain seals of adequate ef' fectiveness with this method. According to another method the rubber-like plugs are molded or vulcanized directly around the leg wires. This method often provides a good seal, but it suffers from the disadvantage of requiring a cumbersome molding and vulcanizing operation for each individual plug.
The present invention provides a readily manufactured plug and leg wire assembly which when combined in an electric explosion initiator produces an assembly of highly water-proof character.
According to the present invention, a bore through a rubber-like plug is held in expanded condition by means of a hollow needle containing a leg wire larger than the normal size of the bore, and the needle and the plug are then disengaged permitting the plug bore to shrink and grip the leg wire. The elastic nature of the plug provides an exceedingly tight seal. The plug and leg wire assembly so produced is then preferably crimped to a metal initiator shell.
The invention will be more specifically described in connection with the drawing which sets forth a preferred embodiment and in which Figure 1 is a longitudinal view, partly in section, of a plug.
Figure 2 is a longitudinal view, partly in section,. of two needles held in a base member.
Figure 3 is a longitudinal sectional view of a plug held in expanded condition by the two needles of Figure 2.
Figure 4 is a longitudinal view, partly in section, of the completed leg wire and plug assembly, and
Figure 5 is a longitudinal view, partly in section, of a completed electric detonator.
Figure 1 of the drawing shows a cylindrical neoprene plug about 0.255 inch in diameter, about s inch long, and provided with two 1ongitudinal bores l3 and [5 each about 0.022 inch in diameter and spaced about inch apart, center-to-center.
In Figure 2 are shown two needles l1 and I9 provided with hollow portions 2| and 23, respectively, and held in upright position by support member 25 containing pins 2! and 29 which fit inside respective hollow portions 2| and 23. Needles I! and I 9 are each 0.072 inch in outside diameter along their shank portions and hollow portions 2| and 23 are each 0.054 inch inside diameter.
In the manufacture of the plug and leg wire assembly, neoprene plug member ll is placed on needles I! and I9 so that the points of the needles enter bores l3 and I5, and plug II is then forced down over needles I! and l 9 until it reaches support 25. Since needles I! and I9 are larger in diameter than bores l3 and |5, it is readily seen that bores l3 and I5 are forced into expanded condition. The points onneedles l7 and I9 are rounded as shown on the drawing, for it has been found that rounded points assist greatly in entering the needles in the plug bores.
After plug H has been brought down to the bottom of the shanks'of needles l1 and I9, support member v25 bearing pins 21 and 29 is removed from the needles and leg wires 3| and 33 hearing insulation 35 and 31, respectively, are inserted into hollow portions 2| and 23 of the needles I! and I 9. Wires 3| and 33 are 0.025 inch in diameter and insulation 35 and 31 is in each case 0.049 inch in outside diameter. Afterwires 3| and 33 have been inserted into hollow portions 2| and .23, needles I! and I9 are withdrawn from plug H. Needles l1 and [9 are provided with indented portions 39 and 4|, respectively, to rovide an easy means for gripping them to pull them fromplug ll. Since bores l3 and I5 are normally much smaller than either wires 3| and 33 or insulation 35 and 31, it may be seen that as needles l1 and 19 are withdrawn from, and the ends of their shanks pas through, plug ll, bores l3 and I5 spring back and contract tightly around the leg wires and their insulation. The final leg wire and plug assembly is shown in Figure 4.
Figure 5 shows a finished detonator. Electric match 55 is soldered to leg wires 3| and'33. The resulting plug, leg wire, and match assembly is inserted intocharged gilding metal initiator shell 63 containing the conventional base charge 49, primary charge 5| and flash charge 53. As a final step, shell 43' is. crimped into plug H by means of crimps. 45 and 41 to complete the assembly. Crimps; 45 and 41 not only hold plug I l in shell 43 and provide a shell. closure between plug and shell, but they also greatly increase the tenacity with which wires 3! and 33 are held in plug ll.
Detonatcrs closed as just described have been found to be water-proof under 250 pounds per square inch of water pressure held for sixteen hours at 125 F. and under 50 poundsv per square inchof water pressure: held for four hours at 32- F.
It will often be found desirable to moisten theplugs and needles with glycerine or other lubricant to permit; easier expansion. of the. bores. It is also often advantageous to dip the wires in sealing material such as rubber solvent or rubber cement prior to inserting them in the hollow portions of the needles. It is found that when cement is placed on the wires in this manner it tends to seal the joint between the insulation and the wire when the plug bore contracts a. joint where lack of water-resistance. has often been evidenced heretofore.
While neoprene is a preferred plug material, other rubber-like substances may be used with entirely satisfactory results. Natural rubber or various. synthetic rubbers such as buna and butyl rubber, for example, may be. used in the invention.
Plugmaterial is readily supplied in long lengths extruded so asto provide the desired bores. When plug material is obtained in this form it is con,- venientl'y but to the desired plug length after the needles. have been partially inserted into the bores.
Plug and wireassembliesof the invention may be used with ignition means of various types. In addition to the match type, bridge plug or head types may be employed, for example.
It is usually preferred to employ insulated wire in the assemblies of the invention, but the invention will also be found applicable to usefwith bare wires. When insulated wire is employed, the insulation may: extend right through the plug or only part-way: through as shown in the specific embodiment described above,
Insulation may be of many difierent types. As examples may be listed ethyl cellulose, vinyl halide, nylon compositions, and fabric or enamel insulations of various sorts.
Many different shell materials may be employed in the manufactureof initia-torsaccording to the invention. Usually: gilding metal or aluminum 4 shells are preferred, but other metal or plastic materials may be used. Any effective number or forms of crimps may be used in accordance with the invention.
The invention may be performed equally well if the plug is moved over the needles or the needles are moved through the plug. Also it is not imperative that two needles be employed. The wires may be inserted separately, or a single hole plug may be supplied with a single or a bifilar wire in accordance with the invention.
What is claimed is:
l. A process for making a plug and leg wire assembly for electric explosion initiators which comprises providing a rubber-like plug having a bore smaller than the diameter of a flexible leg wire, expanding said bore with a hollow needle, the hollow portion of which is large enough to containsaid leg wire, providing that said leg wire extends in said hollow needle sufficiently far that it also extends through said plug, then holding said plug and said leg wire stationary relative to one another, and moving said plug and said needle relative to one another and in the same relative direction as was employed in expanding said bore whereby the passage of said needle through said plug is completed and said plug bore shrinks and grips saidleg wire.
2. A process according to claim 1 wherein said plug is neoprene.
3. A process according to claim 1 wherein said leg wire is insulated and it is provided that said insulation extends at least part way through said plug.
' 4. A process according to claim 1 wherein said leg wire is insulated, it is provided that said insulation extends part way through said plug, and said wire is coated with sealing material prior to being gripped by said plug.
5. A process for makin an electric explosion initiator which comprises making a plug and leg wire assembly according to the process of claim 1, inserting said plug and leg wire assembly in the mouth of the initiator shell and crimping the walls of said shell into said plug. 6. A process for making an electric explosion initiator which comprises making a plug and leg wire assembly according to the process of claim 1 wherein said plug is neoprene, inserting said plug and leg wire assembly in the mouth of the initiator shell and crimping the walls of said shell into said plug.
'1. A process for'makin an electric explosion initiator which comprises making a plug and leg wire, assembly according to the process of claim 1 wherein said, leg wire is insulated and it is provided' that said insulation extends at least part way through said plug, inserting said plug and leg wire assembly in the mouth of the initiator 5111611 and crimping the walls of said shell into said 1) ug.
8. A process .for making an electric explosion initiator which comprises making a plug and leg wire assembly according to the process of claim 1 wherein said leg wire is insulated, it is provided that said insulation extends part way through said plug and said wire is coated with sealing ma-- terial prior to being gripped by said plug, inserting said plug and leg wire assembly in the mouth of the initiator shell and crimping the walls of said shell into said plug.
9. A process for making an electric explosion initiator which comprises providing a rubber-like plug having two bores; providing two flexible insulatedleg wires. each of said bores being smaller than the diameter of said leg wires, expanding each of said bores with a separate hollow needle, the hollow portion of each needle being large enough to contain one of said leg wires, coating each of said leg wires with sealing material, inserting each of said leg wires separately into one of said hollow needles sufiiciently far that each leg wire extends through said plug and the insulation on each leg wire extends part way through said plug, then holding said plug and said leg pleted and said plug bores shrink and grip said leg wires, inserting the plug and leg wire assembly, so produced, in the mouth of an initiator shell, and crimping the walls of said shell into said plug.
DANIEL D. HUYE'IT.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 46,464 Grant Feb. 21, 1865 54,651 Robbins May 8, 1866 829,595 McEachern Aug. 28, 1906 1,605,688 Olin Nov. 2, 1926 2,314,606 Ashcroft Mar, 23, 1943 2,399,034 Huyett et a1 Apr. 23, 1946