US3612748A - Explosion connector - Google Patents

Abstract

A method of connecting wires, cables and the like including the steps of placing the wires inside a deformable shell, placing an explosive on the outside of the deformable shell, confining the explosive by a generally nondeformable outer shell, and igniting the explosive to deform the deformable shell into contact with the wires and the wires into contact with one another. A connector for joining wires, cables and the like including inner and outer shells and an explosive located between the shells, the explosive functioning, upon ignition, to deform the inner shell into crimping engagement with wires placed therein and the wires into crimping engagement with one another.

Description

United States Patent David 'I. James [72] Inventor De Kalb, Ill. [21] Appl. No. 827,130 [22] Filed May 21, 1969 [45] Patented May 12, 1971 [73] Assignee Ideal Industries, Inc.

Sycamore, Ill. Continuation of application Ser. No. 612,655, Jan. 30, 1967, now abandoned.

[54] EXPLOSION CONNECTOR 3 Claims, 16 Drawing Figs.

[52] U.S. Cl 174/94, 29/628, 102/21, 102/24 R, 102/28 R, 174/87, 339/276 E [51] Int. Cl H02g 15/08 [50] Field of Search 174/84.1, 90, 94; 339/276 E, 275 E; 85/37; 102/28, 70.2; 89/101; 29/427 E, 628

[56] References Cited UNITED STATES PATENTS 2,387,742 10/1945 Burrows 174/94 X Primary Examiner-Darrell L. Clay Attorney-Parker, Carter & Markey ABSTRACT: A method of connecting wires, cables and the like including the steps of placing the wires inside a deformable shell, placing an explosive on the outside of the deformable shell, confining the explosive by a generally nondeformable outer shell, and igniting the explosive to deform the deformable shell into contact with the wires and the wires into contact with one another.

A connector for joining wires, cables and the like including inner and outer shells and an explosive located between the shells, the explosive functioning, upon ignition, to deform the inner shell into crimping engagement with wires placed therein and the wires into crimping engagement with one another.

III,-IIIIIJIIIII IIIIIIII EXPLOSION CONNECTOR This is a continuation of application'Ser. No. 6l2,655, filed Jan. 30, I967, and now abandoned.

SUMMARY OF THE INVENTION This invention is concerned with a method and apparatus for connecting wires, cables and the like and more specifically to such a method and apparatus utilizing an explosive charge.

Another object is a method of connectingwires by inwardly deforming a defonnable member into crimping contact with the wires by means of a confined explosive charge.

Another object of this invention is a method of connecting at least two wires by crimping them together through the use of a shell deformed by a charge of an explosive.

Another object is an apparatus for connecting at least one cable or wire to an end fitting by means of a confined explosive charge.

Another object is a method and an apparatus for effecting a low electrical resistance connection between conductors including even such ordinarily difficult combinations as aluminum-to-aluminum and aluminum-to-copper where the readily oxidizable surface of at least one of the conductors normally inhibits good connections.

Another object is a method and apparatus for forming a contact between electrical conductors that is not subject to interface corrosion.

Another object is a self-contained device which utilizes an explosive charge for joining wires.

Another object is an explosive actuated device for joining wires in which the force exerted to join the wires will increase automatically as the combined cross-sectional area of the wires increases.

Another object is a device for joining wires having a deformable crimping member which may be selectively preweakened.

Another object is an explosive-actuated wire-connectingdevice having an outer insulating cover.

Another object is a primer containing a deflagrating or a detonating explosive.

Another object is a primer actuatable by a low-voltage source of electricity.

Another object is a method and apparatus for joining electrical conductors that causes less reduction in conductor cross sections and less localized cold flow of metal than mechanical crimping methods exerting a similar amount of force.

Another object is a holder for supporting a connector during joinder of the wires which has a self-contained source of electrical power.

Another object is an explosion connector in which a deflagrating explosive charge will be self-quenching upon ignition if the connector is appreciably overcharged with deflagrating explosive.

Other objects will be found in the following specifications, claims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is illustrated more or less diagrammatically in the following drawings wherein:

FIG. 1 is a longitudinal cross-sectional view through an embodiment of the invention of this application;

FIG. 2 is a view similar to FIG. 1, but showing a pair of wires installed in the connector and an electrical circuit for actuating the explosive primer;

FIG. 3 is a cross-sectional view similar to FIG. 2, showing the connector crimping the wires together;

FIG. 4 is a transverse cross-sectional view through a connector showing the wires crimped together;

FIG. 5 is a plan view of a modified fonn of connector;

FIG. 6 is a cross-sectional view of a holder and source of electrical power for actuating the connector of FIG. 1;

FIG. 7 is an enlarged view of a primer;

FIG. 8 is a cross-sectional view of the primer of FIG. 7;

FIG. 9 is a longitudinal cross-sectional view through the modified form of the connector shownin FIG. 5 withzthe insulating cap removed;

FIG. 10 is a cross-sectional view taken along line l0-l0 of FIG. 9;

FIG. 1 1 is a cross-sectional view similar to FIG. 9, but showing the connector and wires after actuation of the explosive charge. The products of combustion, largely gaseous in nature, are not shown;

FIG. 12 is a cross-sectional view taken along line 12-12 of FIG. 11;

FIG. 13 is a longitudinal cross-sectional view of another modified form of connector;

FIG. 14 is a cross-sectional view of amodified holder and source of electrical power for actuating a modified connector;

FIG. 15 is a longitudinalv cross-sectional view through another modified form of connector showing a part of the probe contactor of the type used with the holder of FIG. 14; and

FIG. 16 is a plan view of yet another modified form of connector.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, FIG. 1 shows a longitudinal cross-sectional view of a connector 11 of this invention intended for joining two or more wires, rods or cables or the like together in like or unlike combinations in a crimping relationship. The connector 11 includes a cap 13 of insulating material such as plastic having a generally central bore 15 closed at one end by a wall 17 and having an opening 19 at the opposite end thereof. The cap includes an integral diverging funnelshaped member 21 leading to the opening 19. Positioned inside the bore 15 of cap 13 is a metal shell 23 having a central bore 25 which may be closed at one end by a wall 27 and has an opening 29 at the opposite end thereof with the walls and openings of the cap and shell respectively positioned adjacent one another. Whereas, the outer shell is shown as a circular cylinder, it should be understood that it may be made in other shapes. For example, the shell may be formed with a square or rectangular cross section.

A second shell 31, preferably more deformable than the first shell, is positioned inside the bore 25 of the first shell. The second shell may be made more deformable than the first shell through the use of a material having a lower elastic limit than the material of the first shell, or through the use of a thinner material, or through the use of a material having a configuration more conductive to defonnation. For some situations it will be desirable to design the connector 11 so that the exterior shell 23 is also deformable as in cases where extreme lightness of the resultant assembly is required and adequate provisions for safety are made to replace the provision of excess strength. In such a case the shell 23 will be designed to expand in the plastic range at a stress somewhere between its yield and its ultimate stress.

The second shell also is formed with a central bore 32 which is open at least at one end thereof with this opening 33 being positioned adjacent the opening 29 of the outer shell 23. The bore 32 is made sufficiently large in cross section to receive wires 34 and 35, shown in FIG. 2, positioned side by side. The opposite end of shell 31 may be closed by a wall 36. At least a portion of shell 31 is spaced inwardly of shell 23 to provide a chamber or cavity 37 between the shells. This chamber or cavity is sealed adjacent the openings of the shells at 38. Sealing of the chamber may be accomplished as shown in the drawings by overlapping shell 23 and shell 31 as at 41.

An explosive 43 is placed in the chamber 37 between the outer shell 23 and the inner shell 31. This explosive is preferably of the deflagrating type and may be gunpowder of the "double base" type, which contains nitrocellulose and nitroglycerine, or may be straight nitrocellulose. This type of explosive is readily ignited by a spark or a flame or other source of heat but not by an ordinary shock, as would be produced by dropping a connector on a hard surface such as a floor. A detonating type of explosive may also be used but would require a thicker external shell 23 fee the same amount of defonnation of the inner and outer shells. The explosive may be selected to be detonated by shock, spark, flame, heat, friction or electricity to suit a specific design purpose. Explosive combinations which include detonating, deflagrating, and priming mixtures in various proportions, or any two of the foregoing, may be used as the end use, commercial considera- 'tions and manufacturing case may dictate. The amount of the explosive charge may be varied depending on the cross-sectional areas of the wires to be connected, but it should be sufficient, upon explosion, to deform the inner shell 31 into wire crimping contact with the smallest combined cross-sectional area of wires proposed to be connected.

A primer 45 for igniting the explosive 43 is located in the chamber 37 in contact with the explosive. Conductors 47 and 49 may be provided to extend from the primer to the exterior of the connector 11 through openings (not shown) in the shell 31 or through the joint at the open end 33 of the shell 31. A chemical such as sodium thiosuflate 50 may be provided as a thin layer at the interface between the cap 13 and the metal shell 23 to dissipate heat passing through or generated in the metal shell 23 when the explosive is burned, thereby allowing the use of a less heat-resistant material for the cap 13. The conductors 47 and 49 may be connected respectively to a source of electrical energy such as a battery 55. The circuit may be closed by a switch 57 to ignite the primer.

The battery 55 may be located in a holder 59, as shown in FIG. 6, equipped with a chamber 61 adapted to receive and hold a connector 11. The switch 57 may be located in the housing for actuation by a slidebutton 63. The conductors 47 and 49 of the connector 11 may attach to electrical circuit 64 leading to the battery and to the switch 57 by means of clips 65 and 67 mounted on the holder 59.

The primer 45, shown in FIGS. 7 and 8, connects to the ends of the conductors 47 and 49 which are opposite to the ends thereof connected to the clips 65 and 67. This primer includes a high resistance conductor 81 which spans and is connected to the spaced ends of conductors 47 and 49 as by soldering. A deflagrating explosive such as smokeless powder 83 surround the high resistance conductor 81. A heat-initiated detonating explosive primer compound might be used as an alternate. The high resistance conductor 81 is constructed so that upon the passage of current from a dry cell battery it will heat to incandescence before melting or burning through and thereby ignite the smokeless powder 83. It is also possible to use the heated wire alone to initiate the explosion of the main explosive charge. To increase its ignition-initiating effectiveness, the high-resistance wire 81 and the bare portions of conductors 47 and 49 to which it is soldered may be lightly coated with a deflagrating compound such as may be made by dissolving smokeless powder in a solvent. The coating may be applied by dipping or with a brush. This coating acts to promote ignition effectiveness by continuing to burn and produce heat and flame after the wire 81 has burned through. The smokeless powder is contained in a combustible and burstable wrapper 85 which is sealed and secured to the insulation 87 and 89 of the conductors 47 and 49 by binding material at 91 and 93. The binding material may be thread or very fine wire. The wrapper also acts as an electrical insulator.

Other types of primers, in addition to the primer 45, may be used with a connector 11 of the type shown in FIG. 1. For example, a percussion primer of the type used in rifle cartridges could be installed in the outer shell 23. If this is done, it would be advisable to eliminate the insulated cap 13. An electrically fired detonating type might be used. Also a heat source applied to either the inside of the inner shell 31 or the outside of the outer shell 23 or both can be used to bring at least a portion of the explosive charge 43 to the temperature necessary for initiating the explosion, in the cases where the charge is a heat-initiated type. Such that may also be supplied by high frequency heating of magnetic shells, or, in the case of nonmagnetic shells, by the addition of a magnetic element between shells in contact with the charge and heated variable magnetic flux.

A modified form of connector for joining wires end to end in the manner of a splice is shown in FIG. 5. This connector 111 is similar to connector 11 but differs in that it is equipped with openings at both ends thereof similar to the opening in one end of connector 11 to permit wires to be inserted from opposite sides for overlapping connection of the wires in a splicelike manner. It should be apparent that a connector having a screw threaded stud, and eyelet, a hook, or an electrical terminal type connector could be constructed in accordance with the teachings of this invention for mechanically attaching one or more conductors, cables or rods to a structure.

A longitudinal cross-sectional view through the modified connector 111 of FIG. 5 with the insulating cap 113 removed is shown in FIG. 9. This connector includes a tubular metal outer or first shell 115, which may be annealed seamless steel tubing, having a central bore 117 with openings 119 and 121 at opposite ends thereof. An inner or second tubular shell 123, which may be of a material more deformable than the first shell, aluminum being an example, is positioned inside the bore 117 of the first shell. It should be noted that in the construction where the primer does not need a metallic shell, either or both of the shells might be made of nonmetallic materials such as a glass fiber filament reinforced plastic outer shell and an inner shell made of a plastic which is plastically deformable at ordinary temperatures such as certain modified vinyls which are plastically defonnable at room temperature. The second shell may also be made more deformable than the first shell through the use of a material having a lower elastic limit than the material of the first shell, through the use of a thinner material, or through the use of a material having a configuration more conductive to deformation than that of the first shell. It is, of course, well known that a plain cylindrical shell is, by nature, a less stable structure under external pressure than under internal pressure. Aside from this natural instability other effects may be employed to make the inner shell more deformable than the outer shell. Relatively simply fabricated forms for inducing more ready collapse under pressure than a circular cross section are elliptical, square, triangular or other polygonal cross section. Indentations such as pointed, rounded, or elongated indentations will supply a preweakened condition at selected locations along the length and around the periphery of a shell. Incisions such as die-stamped patterns will supply preweakened areas in the neighborhood of which collapse under pressure will start. Variable cross-sectional thickness may be employed to place selected thin sections at desirable locations for initiation of the collapse pattern. Such selective collapse will in general provide a lower collapse pressure where a limited pressure short of that needed to substantially completely close the inner shell is sufficient for the grip required in a given application.

The second shell is formed with a central bore 125 which has openings 127 and 129 at the opposite ends. The bore 125 is formed of sufiicient cross section to receive wires 131 and 133 positioned side by side in overlapping relationship as shown in FIG. 10. While in this case and others herein described, the side-by-side relationship of wires, cables, rods or the like is referred to since it is the simplest case to assemble from the standpoint of preparation of the joint and is found in some other types of connectors to be a particularly difficult arrangement to connect, nevertheless, this connector will accept and connect pretwisted wires and the like.

At least a portion of the inner shell 123 is shaped so that it is spaced away from the shell 115 when the shells are assembled so as to provide a chamber or cavity 135 between the shells. The chamber or cavity is sealed adjacent the openings of the shells by overlapping the walls of the shells 115 and 123 as at 137 and 139. The overlapping portions and the portions of the shells which are not separated by the chamber are electrically separated by insulating coatings or pieces of plastic films 141 and 143. These coatings may be applied to the ends of the shells 1 or 123 and if plastic films are used, they may be inserted between the ends of the shells before the shells are overlapped. Polyvinyl chloride film and polyester film have been found to be suitable for this purpose.

Before the ends of the shells 115 and 123 are sealed, an explosive 43 is placed in the chamber 135. A deflagrating explosive of the type previously described may be used. An ignitor, which may be a deformed wire 145 of relatively high electrical resistance, is placed in the chamber 135 in contact with the explosive 43. This wire is deformed so that it will always contact the inner and outer shells to conduct a current between these shells. A single turn of music wire has been found to function satisfactorily as an ignitor. An electrical current may be passed through the ignitor by applying a difference of electrical potential across the shells l 15 and 123.

It should be noted that although conductive materials are usually assumed to be metals, it is possible to employ other materials such as conductive plastics for the shells 115 and 123 in certain applications where their other properties are suitable. Alternatively, there will be connectors made where the inner shell is made of a highly conductive material so that it joins the inserted wires to become a part of the electrical circuit itself. For example, if a connector such as that shown in FIG. 11 or that in FIG. 16 were used to connect two electrical conductors placed in abutting rather than side-by-side relationship, the resulting assembly would result in good connections between the inner shell and each of the conductors but not ordinarily between the conductors themselves. In this case, the shell itself would be a part of the circuit and would normally need to be a material of relatively good electrical conductivity. Additionally, in the case of connectors used for this abutting relationship, if it were desirable to minimize the diameter of a joint, such connectors might be made longer for a better grip on each conductor. Then too, it might be desirable to provide a transverse partition at a selected location along the length of the inner shell to regulate the depth of insertion of the conductors and thereby properly proportion the grip between them. This partition might be located midway or at any suitable ratio of length from one end where it seemed most desirable for the combinations proposed to be joined. Note that more than one conductor might be inserted in either or each end of the connector.

A similar effect could be had by positioning two inner shells, like shell 31 of FIG. 1, in closed end to closed end relationship, within one outer shell such as shell 115 of FIG. 9 with the added provisions that the lip of the outer shell must in this assembly be turned in around the lips of the inner shells in the manner of the assembly shown in FIG. 1. In this case, for an electrical application, if the inner shells do not contact each other both the inner and outer shells must be conductive and not electrically isolated from each other as by the insulating coatings 141 and 143. While this abutting connection can, as described use a conductive shell or shells for electrical connections, it may also be used with various relatively poorly electrically conductive materials for mechanical applications which do not form a part of an electrical circuit.

Another modified form of connector is shown in FIG. 13. Connector 147 is similar to connector 11 differing in that a portion 149 of its outer tubular shell 151 bulges outwardly to form a chamber 153 between shell 151 and inner tubular shell 155. Additionally, a modified insulating cap 157 fits over the connector to close the opening 159 at one end of the bore 161 of the inner tubular shell 155. The cap has an opening 163 located outwardly of the opening 165 of the bore 161. An internal step or rib 166 is formed as part of the insulating cap and is adapted to seat in the annular groove 167 formed between the turned end of the inner shell 155 and the bulge 149 of the outer shell 151 to retain the cap on the connector. The insulating cap may be of any suitable insulating plastic of any desirable degree of rigidity from relatively stiff to relatively flexible to suit the purpose of the user and to be adaptable to the manufacturing processes employed. An explosive charge 43 and an ignitor wire 145 may be positioned in the chamber 153.

A modified form of holder utilized to ignite connectors of the type containing a primer of the deformed wire type is shown in FIG. 14. This holder includes a housing 171 having a chamber 173 adapted to receive a connector 175 for joining wires 177 and 179. A probe contactor 181 which is adapted to deliver electrical current to the inner and outer shells of a connector is mounted for movement in and out of a well 183 formed in the housing.

The probe 181 has contact 185 which engages the inner shell 187 of connector 175 and contact 189 which engages the outer shell 191 of this connector in the manner shown in FIG. 15. When the probe 181 is moved into contact with the inner and outer shells of the connector, it moves the insulated cap 193 of the connector to one side and bulges it outwardly as shown in FIG. 15. For ease of insertion of the probe, the insulated cap 193 may be formed with a partial bulge as shown at 195 in FIG. 15. As in the previously described modified forms of the connector, the inner and outer shells are separated by insulating material such as shown at 197. The insulating material may be plastic or rubber. A chamber 199 is provided between the inner and outer shells to receive an explosive 201 and an ignitor or primer wire 203. The wire 203 contacts the explosive and the inner and outer shells to conduct electrical current applied to the shells by the probe. The current heats the wire and ignites the explosive.

An alternative method of heating the primer wire in a connector in which both the inner and outer shells are formed of nonmagnetic material is to subject the connector to a highfrequency magnetic field. This may be the preferred method of heating the primer wire in connectors used by manufacturers. In such a connector it would not be necessary for the primer wire to contact the inner and outer shells of the connector since it does not conduct electric current between these shells. However, the primer wire should contact the explosive so that it will ignite the explosive when heated. When ignition is accomplished in this manner, the electrical insulating qualities of seals 197 are not required and they may be retained as pressure gaskets or omitted and a self seal of the inner and outer shells against each other may be used.

Where the connectors are used for structural applications in which an external insulating cap is not required, the ignition of the explosive may be brought about by applying heat directly to the external shell of the connector Of course, this will require the use of an explosive sensitive to heat. When such an explosive is used, various chemical, electrical and mechanical means may be used to raise the temperature of all or part of the explosive to its ignition temperature. Other means, for example, friction, hammer action or electrically initiated detonating primers may be used and in some instances may be preferred to the apparatus shown herein.

It should be noted that the insulated cap 193 has a thickened portion 205 at one end which closes one opening into the connector. This thickened portion resists accidental puncture of the insulating cap by the wires being inserted therein. A circumferential rib 207 is provided on the inside of the insulating cap 193 to engage the turned portion 209 of the inner shell to prevent the insulating cap from being dislodged from the connector shells.

The contacts 185 and 189 of the probe 181 connect respectively to wires 211 and 213 which lead to contacts 215 and 217 at the base of the probe. When the probe is completely seated in the connector in the manner shown in FIG. 14, the contacts 215 and 217 respectively engage spring contacts 219 and 221 at the base of the well 183. The spring contacts are connected by wires 223 and 225 to a battery 227. Wire 223 is interrupted by a switch 229 which can be used to make and break the circuit between the battery and the contacts 185 and 189.

FIG. 16 shows a modified connector 231 of the type shown in FIG. 15 adapted for use as a straight through connector and having an insulated cap 233 with two open skirted ends 235. This connector may be used to join wires in an end-to-end relationship in the manner of the connector 111 shown in FIG. 5. The skirted ends 233 of the insulating cap diverge outor the use of power operated tools. Additionally, the explosion I crimping method of thisinvention, by distributing pressure will depend upon the configuration of the inner shell of the connector, its thickness and the material of which it is made,

as well as the'size and number of wires to be connected. It is important to prevent overcharging of the chamber of the con- I nector with explosive since this may result in rupture of the outer shell and injury to the user thereof. It has been found that a deflagrating explosive requires at least a'minimum clearance between its buming'surface and the'walls of its chamber in order to continue burning after ignition, especially if the walls constitute a good heat sink. Also, more reliable continuity of ignition is obtained if the ratio of surface area of a deflagrating explosive to its mass is large. As a consequence, it has been determined that by reducing the ratio of the surface area of the explosive to its mass and by reducing the clearance between'the burning surface of the explosive and the wall of the 'chambena self-quenching action of the explosive will be obtained. Therefore, by designingthe chamber volume and dimensions to accommodate'no more'than the I required charge of explosive, any accidental overcharging of the explosive will reduce the ratio of the surface area of the explosive to its mass and will reduce the clearance between the burning surface of the explosive and walls of the chamber.

Therefore, it can be said that the continuity of ignition of a deflagrating explosive can be controlled by proportioning the. volume of the chamber'in which it is burned. For example, by

using sheets of a deflagrating explosive laid one upon the other or wrapped around the inner shell, the ratioof surface area of the explosive to its mass will be reduced by squeezing layers snugly together if an overcharge of explosive is insertedin the chamber. Therefore, overcharging of the chamber'with explosive'will provide a self-quenching action upon ignition of the explosive. Compacting of a granular charge also provides a self-quenching action. I

In an experiment'conducted at ambient temperatures and utilizing a nitrocellulose material made of rice paper nitrated about 13.1 percent with the pieces of paper being approximately 0.005 inch thick and three-eighths of an inch wide, it was found that reliable and continued initiation of deflagration was obtained with four thicknesses of paper in a chamber of a metal quench test fixture having a 0.035-inch space between the walls. Increasing the explosive charge to six thicknesses of nitrated paper resulted in a charge that was selfquenching upon ignition. This was apparently due to the reduction in the ratio of surface area to mass and reduction of the clearance between the explosive and the walls of the chamber. it should be understood that as the temperature of the deflagrating material is increased, the amount of clearance and the ratio of surface area to mass required for continuous combustion may be decreased.

The use, operation and function of this invention are as follows:

The method and apparatus of this invention are particularly adapted to the connection of wires, either stranded or solid or a combination thereof, and especially wires used as part of electrical circuits or systems. However, the invention should not be limited to the connecting of electrical wires since it is also adaptable to connecting other types of wires as well as cables, rods and the like. The invention may also be used to connect a single wire or cable to a terminal connector in electrical or nonelectrical applications.

The invention in one of its forms is particularly useful in mechanically crimping two or more electrical conductors into physical contact with one another. Present methods of mechanically connecting electrical wires involve the use of manual or power driven devices to deform and crimp the conductors into physical contact with each other. This invention permits the physical deformation and crimping of the electrical conductors without the need for exertion of manual force over a greater area, produces less cold flow of the metal of the conductors at any selected section than is produced by mechanical crimping at its minimum section especially less longitudinal flow. This results in a joint having a greater minimum cross-sectional area than is obtained by mechanical crimping with the same amount of force. I

The explosive method of this invention, which mutual deformation and contact interface between the conductors being connected, also has the advantage of producing a connection with lower electrical resistance than is obtained by mechanical squeezing. This is especially true with conduc- I tors, such as aluminum, which rapidly corrode upon exposure to air to form a surface film having a higher electrical re- I sistancethen that of the unoxidized conductor material. For

example, I have found that a mechanically crimped connection of a pair of 010 gauge aluminum conductors has an initial resistance of about 0.003 ohms with a 7 ampere current flowing while a'connection made by the explosive method of this invention has a resistance of about 0.0003 ohms withthe same current flowing. This reduced resistance is believed to be due to the fact that a highly interlocked interface between the conductors is produced by thesudden'applicationof force caused I by the explosion which does not allow the interface surfaces to creep and stretch in accommodating themselves to each, other as apparently happens in the case where mechanically crimping pressures are more slowly applied. In the case of mechanical crimping, the oxidized surfaces of high electrical resistance I on the exterior of each conductor would maintain continuity during crimping. However, in the case of the connection made by an explosion, the many asperities on the surfacesof each conductor would, without lateral displacement, pierce the matching relatively plane surface on the other conductor, mu-

tually breaking theoxidized film on, the plane surfaces and.

shearing the film from the sides of the asperities to produce large numbers of intimate contacts between unoxidized metal interfaces of lowerelectrical resistance. Thus, it might be said that the use of an explosive force rapidly applied to two conductors results in cold welds'to produce a contact not subject to interface corrosion. While this experiment was conducted with aluminum conductors, similar results should also be obtained with other types of conductors which readily corrode upon exposure to air and produce corroded surfaces having a higher electrical resistance than that of the basic material of the conductors. While it is not thought to account for a major portion of the resistance reduction, the fact that the explosive method tends to produce a relatively large contact area between conductors at the same time that it is retaining a relatively large cross-sectional area is felt to create a portion of the improved conductivity of the joint.

The method and apparatus of this invention utilize an inwardly deformable member to receive the conductors to be joined together and a confined explosive charge located exteriorly of the deformable member so that ignition of the explosive charge will force the deformable member inwardly into engagement with the conductors. The conductors may be arranged so that the deformable member will mutually deform and at least partially unite the conductors into contact with one another to form one conductive mass. With some forms of the invention, especially with the straight-through connectors of the type shown in FIGS. 9 to 13, and 16, it may be desirable to arrange the wires so that they are not deformed into physical contact with one another. in such cases, the deformable member will be forced into physical contact with each of the wires to make the connection. If the connector is used in an electrical circuit, it will be necessary that the deformable member be formed of a conductive material.

In the embodiment shown in FIGS. 1 through 4, the deformable member is a shell 31 having a bore 32 with an exterior opening 33 at one thereof. The opening 33 and bore 32 are sufficiently large to receive the conductors to be joined together in side by side relationship. An outer and generally produces a nondeformable shell 23, surrounds the deformable shell 31 and at least a portion thereof is spaced form the deformable shell to provide a chamber 37 to receive an explosive 43. Ignition of this explosive, which may be accomplished through means of an electrically actuated primer 45, will generate gases, the pressure of which will deform the inner shell 31 into crimping engagement with the conductors 34 and 35 to drive the surfaces of the conductors into a mutually plastically deformed electrically conducting interface.

The deformation of the shell 31 can be controlled by preindenting, preflattening or otherwise selectively deforming or weakening portions of the shell, especially those adjacent the explosive charge 43. The explosion will also tend to maintain the outer shell 23 in its normal configuration since the forces produced by the explosion will be acting on the inside of this shell. Escape of the products of combustion from the chamber 37 is prevented by the seal formed by the overlap of the portion 41 of the shell 23 and the shell 31.

The size of the explosive charge 43 may be varied in accordance with the total cross-sectional area of the conductors to be joined. However, due to the inherent characteristics of this invention, a fixed amount of explosive will be capable of joining connectors of varying total cross-sectional areas within predetermined maximum and minimum limits. This inherent characteristic is due to the fact that the amount of pressure developed by an explosion varies inversely as the volume which is available for the expansion of the gases produced. Therefore, with conductors having greater total cross-sectional area, which normally will require greater mechanical crimping force to effect a good connection, the space available for deformation of the inner shell 31 and thus for expansion of the explosive gases will be less and the pressure exerted by the explosion will be greater. In the event that larger explosive charges are used, it may be necessary to vary the material or increase the thickness of the outer nondeformable shell 23.

The shells 23 and 31 may be covered by an insulating material in the form of a cap 13. This cap is preferably of plastic of a heat-resistant type. A heat absorbing chemical compound such as sodium thiosulfate may be provided as a thin layer 50 at the interface between the cap 13 and the metal shell 23 to dissipate the heat passing through shell 23 when the explosive is burned, thereby permitting the use of a less heatresistant material for the cap 13. To facilitate insertion of the conductors into the bore of the inner shell, the cap 13 may be provided with an integral diverging funnel-shaped member 21 which extends beyond the opening 33 and leads into the bore of the shell 31.

A holder 59 having chambers to hold a battery 55 and a connector 11 during ignition of the explosive is also provided. Through the use of this holder, the ignition of the explosive and the joining of the wires in the connectors may be carried out with maximum efficiency. The holder is utilized by inserting the connector in which the conductors 34 and 55 have already been inserted into the chamber 61. The primer conductors 47 and 49 are connected to the battery circuit 64 at the spring clip connections 65 and 67. The slidebutton 63 is operated to close the switch 57 and complete the electrical circuit 64 igniting the primer 45 firing the explosive. After the burning of the explosive, the primer conductors 47 and 49 are pulled loose from the connector and the attachment of the wires is completed.

The primer 45 is characterized by its insensitivity to heat, shock and static electricity coupled with its ability to be actuated by use of a low-voltage and low-wattage source of power such as a dry cell battery. This primer is particularly intended for igniting a deflagrating type of an explosive rather than a detonating type. The primer utilizes a high electrical resistance member that melts and burns under the application of a small current to ignite a smokeless powder charge surrounding the high resistance member. The ignition effectiveness of the high electrical resistance member can be improved by coating the member and the wires leading to it with a deflagrating compound of smokeless powder dissolved in solvent. The burning of the smokeless powder ignites the burstable and combustible wrapper which together with the flame and heat from the smokeless powder will ignite the deflagrating explosive in which the primer is inserted. This primer also conserves electrical energy because the ignition and burning of the high-resistance member also breaks the electrical circuit to the battery.

The modified connector assembly 111 shown in FIGS. 5 and 9 through 12, inclusive, is primarily intended for connecting wires or cables in an end to end overlapping relationship in the nature of a splice. Wires 131 and 133 may be inserted into the bore of the inner or second shell 123 through the openings 127 and 129 and arranged side by side in overlapping relationship as shown in FIGS. 9 and 10. A difference of potential may then be applied across the shells 115 and 123 to pass an electrical current through the ignitor wire 145 which is located in the chamber in contact with the inner and outer shells and with an explosive 43. The difference of potential may be applied to the shells by contacting the shells with probes connected to wires of different electrical potential. Upon passage of a current through wire it will heat and ignite the explosive charge 43 to compress the inner shell 123 thus forcing the wires 131 and 133 into contact with each other in the manner shown in FIGS. 11 and 12. It should be understood that the number of wires which may be joined by such a connector is not limited to the two shown, but may be any convenient number. Also, the wires need not be the same The connector 147 of FIG. 13 is especially adapted for making pigtail connections. The wires to be connected would be inserted into the bore 161 of the connector through opening 165. After the wires are in place in the bore, the explosive charge 43 may be ignited in the manner previously described for connector 111.

The holder 171 shown in FIG. 14 is intended for use primarily in activating connectors of the type shown in FIGS. 9 through 15 which utilize a primer wire. This holder utilizes a probe contactor 181 which is adapted to engage both the inner and outer shells of a connector such as inner shell 187 and outer shell 191 of the connector 175 shown in FIG. 15. In order to engage the outer shell 191, it is necessary to spread the insulating cap 193. To facilitate this spreading the cap may be bulged outwardly as at 195 in FIG. 15.

When the contactor probe 181 is inserted in contact with the inner and outer shells of a connector as shown in FIG. 15, (the wires which are to be joined having been omitted for clarity of illustration) a current passing through these contacts will heat the wire 203 to ignite the explosive 201 and deform the inner shell 187 into contact with the wires. Before current can be passed through to the contacts and 189 it is necessary that the probe 181 be fully seated in the well 183 with its bottom contacts 215 and 217 engaging the spring contacts 219 and 221 located in the base of the well. With these contacts closed and with the switch 229 operated, current from the battery 227 will heat the ignitor wire 203 to ignite the explosive. The provision of the spring contact switches at the bottom of the probe well acts as a safety feature to prevent ignition of the explosive in the connector until the probe is fully seated both in the connector and in the well and the connecter 175 is fully contained in chamber 173.

Although the connector 175 is shown with an insulated cap 193 which is bulged outwardly at 195 to provide access for the probe 181, the provision of such a bulge or expanded portion is not necessary in all insulating caps. For example, the insulating cap shown in FIG. 13 could also be used in this type of a holder if the material from which it is made is sufficiently flexible to permit the probe to be moved in between the cap and the outer shell a sufficient distance for the contact 189 to engage the outer shell 149 of the connector 147 shown in FIG. 13.

While the preferred form and several variations of the invention have been described herein, it should be understood that suitable other additions, alterations and variations may be made without departing from the inventions fundamental theme.

I claim:

1. A connector for attachment to at least one wire or the like including:

a deformable member having a central bore adapted to receive at least one wire or the like,

at least one opening into said bore,

a generally nondeformable member enclosing and spaced from at least a portion of said deformable member to form a chamber therebetween,

a heat-sensitive explosive located in said chamber and of sufficient quantity, when exploded, to deform said deformable member into physical contact with said wire,

said deformable and nondeformable members being formed of electrically conductive materials and electrically insulated from each other, and

an explosive ignition means including an electrical conductor contacting said deformable and nondeformable members,

said conductor being located in operative contact with said explosive and having such resistance as to heat sufficiently upon passage of a small amount of current therethrough to ignite said explosive.

2. The structure of claim 1 further characterized in that said electrical conductor is a wire deformed to contact both said deformable member and said nondeformable member when positioned in said chamber.

3. The structure of claim 1 further characterized in that said electrical conductor is a turn of thin wire of sufficient diameter to contact both said deformable member and said nondeformable member when positioned in said chamber.

Claims (3)

1. A connector for attachment to at least one wire or the like including: a deformable member having a central bore adapted to receive at least one wire or the like, at least one opening into said bore, a generally nondeformable member enclosing and spaced from at least a portion of said deformable member to form a chamber therebetween, a heat-sensitive explosive located in said chamber and of sufficient quantity, when exploded, to deform said deformable member into physical contact with said wire, said deformable and nondeformable members being formed of electrically conductive materials and electrically insulated from each other, and an explosive ignition means including an electrical conductor contacting said deformable and nondeformable members, said conductor being located in operative contact with said explosive and having such resistance as to heat sufficiently upon passage of a small amount of current therethrough to ignite said explosive.

2. The structure of claim 1 further characterized in that said electrical conductor is a wire deformed to contact both said deformable member and said nondeformable member when positioned in said chamber.

3. The structure of claim 1 further characterized in that said electrical conductor is a turn of thin wire of sufficient diameter to contact both said deformable member and said nondeformable member when positioned in said chamber.

Images