Twin electrical lead and connector assembly

A length of leg wire comprising a pair of electrical leads is coiled into a conical helix. An electrical connector is attached at one or both ends. The electrical connector is characterized as capable of maintaining the ends of the two electrical leads in non-conductive and preferably also water-resistant condition. The connector further may also be characterized as permitting a water-resistant, high tensile strength splicing of the ends of the leg wire with another pair of similar electrical leads without the use of splicing tools. The other end of the leg wire may be clean cut or connected to another electrical connector. The coiled portion is flexible but shape sustaining and therefore collapses and expands in the coiled arrangement. The assembly is packaged in the collapsed configuration. When removed from the package, the coiled portion of the leg wire expands but retains the coiled configuration. The coiled leg wire is much easier to work with in the field as the coil expands and retracts readily without tangling. Moreover, the coil configuration allows the wire to rest on its side in the expanded form so that it can be fed down the blast hole easily without the wire becoming tangled. Further, the coiled portion can be retrieved quickly by simply regathering the coiled portion with one hand.

FIELD OF THE INVENTION 
The present invention relates generally to wiring for electric detonation 
devices for explosives. 
SUMMARY OF THE INVENTION 
The present invention is directed to an assembly comprising a leg wire 
including a pair of electrical leads of equal length. The leg wire has a 
first end and a second end and a portion therebetween coiled into a 
conical helix. The coiled portion is characterized as flexible but shape 
sustaining. An electrical connector is connected to the first end of the 
leg wire. The electrical connector is characterized as capable of 
maintaining the ends of the two electrical leads in the leg wire in 
non-conductive condition.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Electric and electronic detonators typically comprise a small charge of 
explosive contained in a metal casing. The detonators are equipped with 
twin electrical leads referred to as "leg wires." Detonators are 
commercially available with leg wires of assorted lengths, such as 16 
feet, 24 feet, 50 feet, and so forth. The shorter lengths of wire are 
gathered in a "figure eight" configuration and secured by a tie of some 
sort. Lengths of leg wire in excess of about 50 feet typically are mounted 
on a spool. 
Detonators are also manufactured with different delay periods, such as 25 
milliseconds, 50 milliseconds, and so forth. Given the specific leg wire 
lengths and delay periods of conventional detonator products, detailed 
planning of a particular blasting project is required so that the 
activation of the detonators can be controlled from a remote control site. 
Such planning includes an analysis of the number of blast holes, the depth 
of each hole and the required delay period for each detonator. Then, the 
operator must purchase the correct number of detonators, ensuring that 
there is a sufficient number of detonator combinations of each delay 
period and leg wire length. 
To utilize a detonator which has the desired delay period but which has an 
inadequate length of leg wire, an additional length of leg wire may be 
attached by splicing it to the ends of the leg wire on the detonator. 
Industry standards presently require that the ends of the leg wires on 
detonators be shunted by stripping the insulation jacket for a few inches, 
twisting the bare conductive core portions of the leads together, and 
covering the stripped portions of the wire with a non-conductive 
protective sleeve. This is done to reduce the likelihood that a stray 
electrical charge will activate the detonator. 
To splice on additional leg wire, the ends of the extra leg wire are 
stripped and joined to the stripped ends of the leg wire from the 
detonator by twisting the ends together or using a crimping tool. While 
effective, this splicing procedure is time consuming and inconvenient at 
the blast site. Moreover, such connections do not provide sufficient 
tensile strength to withstand the strain of lowering a charge into a blast 
hole. If the connection breaks and the charge is dropped to the bottom of 
the hole the retrieval process is hazardous and expensive. 
The present invention provides a leg wire assembly comprising a length of 
leg wire configured in a coil in the form of a conical helix. One end of 
the leg wire is attached to an electrical connector. The other end of the 
leg wire may be left bluntly cut or "clean cut" for use with another 
electrical connector in the field. Alternately, another electrical 
connector may be attached to the other end. 
The leg wire will retain the coiled shape when removed from the package. 
This makes the assembly easier to use in the field. The wire can be 
expanded and stretched across a surface so that it is available for 
feeding the wire doom a blast hole without tangling. Further, the coiled 
configuration can be easily gathered up with one hand to retrieve the 
unused portion of the leg wire or to retrieve the leg wire after discharge 
of the explosive. 
Still further, it will be appreciated that the leg wire assembly of this 
invention will in most instances reduce the cost of materials for a blast 
job. This is because detonator assemblies with different leg wire lengths 
(but the same delay period) are interchangeable by using leg wire 
assemblies of this invention as extensions. Thus, the leg wire assembly of 
this invention permits the operator to purchase detonators simply by delay 
periods, rather than the delay period and the leg wire length. This 
simplifies the planning and execution of a blast job, as all detonators 
with equal delay periods are made interchangeable. These and other 
advantages of the present invention will become apparent from the 
following description. 
With reference now to the drawings in general and to FIG. 1 in particular, 
there is shown therein a leg wire assembly in accordance with the present 
invention and designated generally by the reference numeral 10. The 
assembly 10 includes a pair of electrical wires referred to herein 
collective as the "leg wire" 12. Each electric wire in the leg wire 12 
comprises an internal conductive core surrounded by an external insulating 
jacket. The pair of electrical wires may be two separate insulated wires 
(as shown) or a pair of wires joined in an integral insulating jacket. 
The leg wire 12 has a first end 14 and a second end 16 and a coiled portion 
18. The coiled portion generally is in the form of a conical helix, that 
is, a spiral in which the diameter of the loops gradually decreases from 
the first end 14 to the second end 16. The coiled portion illustrated in 
FIG. 1 is partially expanded to better illustrate the configuration of the 
coil. It will be understood that for packaging, storage and shipping, the 
coiled portion will be more completely collapsed to minimize the space 
occupied by the assembly 10. 
An electrical connector 20 is attached to the first end 14 of the leg wire 
12. The electrical connector 20 is characterized as capable of maintaining 
the ends of two electrical leads in non-conductive and preferably also a 
water-resistant condition. Even more preferably, the electrical connector 
20 permits a water-resistant, high tensile strength splicing of the leads 
with another pair of similar electrical leads without the use of splicing 
tools. 
A preferred electrical connector for this purpose is marketed under the 
name ClipMate.TM. by ClipMate Corporation (Oklahoma City, Okla.). This 
electrical connector is described in detail in U.S. Pat. No. 4,952,167, 
issued Aug. 20, 1990, and the contents of this patent are incorporated 
herein by reference. A connector of this type is attached to a leg wire by 
simply inserting the two ends of the leads into the holes 22 and 24 and 
pulling back until the connector grips the leads. 
The second end 16 of the leg wire 12 may be clean cut in a conventional 
manner, as shown in FIG. 1. Alternately, the second end 16 of the leg wire 
12 may be connected to another electrical connector. 
Turning now to FIG. 2, the use of the assembly 10 will be described. The 
assembly 10 is removed from the package (not shown), placed on its side on 
a surface 28 and loosely expanded across the surface as shown in FIG. 2. 
In the preferred use of the assembly 10, the clean cut second end 16 of 
the leg wire 12 is connected to the leg wire of a detonator assembly 
comprising a detonator with an attached electrical connector similar to 
the electrical connector 20. Such a detonator assembly is shown and 
described in detail in U.S. Pat. No. 5,392,712, issued Feb. 28, 1995, 
entitled ELECTRIC DETONATOR AND LEAD CONNECTOR ASSEMBLY, filed 
concurrently herewith, and the contents of that application are 
incorporated herein by reference. This product is marketed under the brand 
name ROS-DET.TM. by ClipMate Corporation (Oklahoma City, Okla.). However, 
it will be appreciated that end 16 of the leg wire 12 of the assembly 10 
of this invention also may be spliced to another leg wire in the 
conventional manner. 
In the expanded position illustrated in FIG. 2, the coiled portion 18 of 
the leg wire 12 may be conveniently extended or retracted without becoming 
tangled. Unused leg wire may be retrieved by simply scooping up the free 
standing coils with one hand. Similarly, the entire assembly 10 can be 
retrieved by regathering the coiled portion 18, as the leg wire readily 
reassumes its coiled configuration. 
While in the preferred embodiment, a connector 20 is attached to the first 
end 14 of the leg wire 12 and the second end 16 is clean cut, it will be 
appreciated that leg wire assemblies comprising a second connector on the 
second end 16 also are within the scope of the present invention. 
Changes may be made in the combination and arrangement of the various 
parts, elements, steps and procedures described herein without departing 
from the spirit and scope of the invention as defined in the following 
claims.