Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.


  1. Advanced Patent Search
Publication numberUS2315823 A
Publication typeGrant
Publication dateApr 6, 1943
Filing dateNov 26, 1938
Priority dateNov 26, 1938
Publication numberUS 2315823 A, US 2315823A, US-A-2315823, US2315823 A, US2315823A
InventorsSmith Roscoe B
Original AssigneeHercules Powder Co Ltd
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Shunt for electric blasting caps
US 2315823 A
Abstract  available in
Previous page
Next page
Claims  available in
Description  (OCR text may contain errors)

APi"il 6, 1943' R. B. SMITH 2,315,823v


FlGrl FIGrVZ www gm@ lN/VENTOR av .maw

ATTORNEY Patented Apr. 6, 1943 UNITE Fi-CE 2,315,823 snUNr ron ELECTRIC BLASTING cars Roscoe B. smith, Wilmington; no1., assignor to Hercules Powder Company; Wilmington, Del., a corporation of Delaware Application November 26, iosa-serial No. 242,466

(o1. 1oz-f2s) 1 Claim.

My invention relates to improvement in blasting caps and other electrical ring devices for explosives. More particularly it relates to the provision of means whereby the accidentalkflring of a blasting cap or other electrical firing device through contact of the lead wires with a source of current will be positively avoided. Y

As is well known electric blasting caps comprise a container which holds a detonating charge, for example, diazodinitrophenol. Within said container is provided a firing assembly which includes a bridge wire embedded within the detonating charge itself or within a more readily red ignition charge. From the bridge wireA extend two insulated lead wires of such a. convenient length that they may be attached to a. source of electric current for the purpose of ring the said electric blasting cap. To facilitate the connection of these insulated lead wires to the source of current it has been the accepted practice cf the prior art to furnish about two to about three inches of bare wire at the ends of said insulated lead wires.

It has been well recognized that the uninsulated portion of the lead wires constitute a hazard in that they afford an opportunity for the accidental discharge of the cap by coming into contact with an electric current. This accidental discharge is easily possible since, for example, in a mine the lead wires are frequently trailed and are likely to come into contact with a live circuit or a stray current as, for example, a trolley line or a charged rail. To prevent the possibility of premature explosions, Various means of shunting the lead wires have beenfsuggested, but have been for many reasons found unsatisfactory.

The methods of shunting now in use such as twisting the wires together or bridging the wires with various types of metal shunts, have not been entirely satisfactory since in all cases the shunted wires are hard to separate without considerable distortion or damage. This distortion of the bare ends of the lead wires makes their use diiiicuit as tight electrical connections are harder to obtain.

The object of this invention is to provide means whereby the difficulties of protecting electrical firing devices with metallic shunts are overcome.

A further object of this invention is to provide a shunting device for the lead wires of electric ring devices that may be used and removed without distorting or damaging the bare ends of the lead wires.

Still a further object of this invention is the provision of a. metallic shunt that may be removed from and replaced on the bare ends of the lead wires of electric firing devices when it is desired to test the ring device before connection into the ring circuit. Other objects will appear hereinafter.

metallic spring clip of this invention provides due to its design positive contact between the uninsulated portions of the two lead wires of any'ring-device and thus prevents the accidental discharge of the device from contact of the lead wires with a strap currentv or a live circuit. Further this metallic spring clip is very easy to place in -position on the lead wires and is equally easy to remove from the lead wires. The removal of the spring clip is carried out in such amanner that the uninsulated portions of the lead wires are not damaged or distorted in any way. The design of the clip aids the operator in placing the clip on the bare ends of the wire at a point adjacent to the end of the insulated portion of the lead wires and further the design of the clip prevents the operator from placing the shunt on the insulated portion of the lead wires. A shunt to be effective should be placed closely to the end of the insulated portions of the lead wire but must not be on the insulation; therefore, the clip shunt of this invention has been so designed as hereinafter will be described to provide these requirements of eectiveness.

Having now indicated in a general way the nature and purpose oi this invention there follows a more detailed description of preferred embodiments thereof as shown 'by the accompanying drawing in which:

Figure l shows an electric ring device in which the uninsulated end portions of the bundled lead wires are shunted by the metallic spring clip of this invention.

Figure 2 shows a perspective view of the rnetallic spring clip shunt of this invention, this perspective view being an enlargement of the metallic spring clip shunt shown positioned on the wires of the firing device depicted in Figure l.

Figure 1 shows an electric blasting cap l from which extends a pair of lead wires of any common and well known size 2 that have their uninsulated end portions 3 protected by the metallic spring clip shunt 4. The clip shunt 4 is so placed on the lead wires that the bare ends 3 are held in close contact. The rclip shunt of Figure l is shown in Figure 2 by a perspective View and is made of any metal that when formed as shown will have suicient spring to tend to maintain the open shape depicted. The form of the shunt 4 provides two holes 5 and 6 which, preferably, have a tear-drop outline to insure maximum contact with the wires due to pressure and wedging. The holes 5 and 6 may be, however, of any desirable size and shape. An insulation-stop hole "l, situated on lug 8, is of sufficient diameter to allow the insertion of the uninsulatedends 3 of the pair of lead wires 2, but is large enough-'to permit the passage, of the insulated portion ofthe leadwires 2. The@ hole 9 situated at the bend of the clip 4 is ot such size and shape that the lead wires 2 may be inserted through it with ease. This hole 9 is provided to allow the lead Wires of a firing device to pass completely through the shunt-thereby preventing the kinking of the wires. f

A modification of the design of the spring `clip shunt of this invention omits the lug 8 with hole 'I thus removing the insulation-stop. This modication, therefore, necessitates the design and size of hole 6 to be so changed that the diameter 'will permit the passage of the uninsulated portions 'of the lead wires butwill act as a stop to vthe insulated portions of the wires. This modificat'ion further necessitates that the lead wires- '2 of the .device will' be threaded' through-fthey shunt `from the `end containing -hole1 9. It will be appreciated that I may, if so desired, design hole 9 to act asthe insulation stop. Now in the event of desiring 'to thread the lead -Wires 2 through the shunt from the opposite end, that is through hole rst, the hole 5 will necessarily become the insulation-stop hole which will therebynecessitate a| change in the `diameter of hole 5.

It will be appreciated by'those skilled in the ar't vthat the design of this metallic clip shunt in respect to which hole is to be used as an insuf lation-stop depends upon the method of threadl `the clip shown in the attached drawings is parabolic, the spring section may be of any suitable design that gives the necessary spring action to the slip.

The metallic clip shunt in accordance with this invention presents severalv very distinct advantages over the shunts of the prior art.

The insulation-stop hole presents an advantage since this hole provides the means whereby an operator is aided in correctly locating the shunt on the bare ends of the lead wires thereby ,preventing the improper application f of the shunt. The shunts of the prior art were placed in position entirely by the skill of the operator and often a shunt was located partly or entirely onthe insulated portions of the-lead wires. A shunt so located is rendered useless and becomes a hazard as the tiring device is left unprotected.

` A further advantage is the design of the clip shunt which prevents the accidental removal of the device' as'its spring action provides positive l gripping of the wires and its slightly streamlined ,shape` prevents removal by any brushing action."y The removal of shunt while dirlicult by accident is'v'eryeasy by an operator since a slight pressure on the sides of the shunt relieves all e gripping action' of the spring.

` v.Another advantage possessed by the shunt of this invention over any shunt of the prior art is the fact that this shunt may be replaced on the lead wires after its rst removal and still afford 'the same efficient shunting action. This advantage is highly desirable since one of the common practices in blasting is the removal of the shunt some time before the actual firing of the device to allow testing of the firing device by a blasting galvanometer or circuit tester. Thus, from the time of testing to the time of tiring there may elapse considerable time and during the interval the' iiring device is unprotected. The use of a shunt capable of being replaced removes the necessity of leaving ring devices unprotected.

The use of the clip shunt is also advantageous due to the condition in which this shunt leaves the wires of the firing device. The removal of the clip shunt from'the uninsulated portions of i the lead wires leaves the wires in an undamaged and undistorted condition, and further during removal the clip shunt may also be allowed to exert'v a scraping action on the lead wires and so provide clean, bright lead wire ends. Therefore,

lthe clip shunt of my invention aids materially in theI preparation of positive electrical connections to the firing circuit.

It will be understood that the metallic clip shunt in accordance with this invention may be used as a protecting device on any of the electric ring devices known to the art, for example electric blasting caps, delay electric blasting caps, electric squibs, or any -other commercial electric firing devices.,

It will furtherbe understood that the details and-examples given hereinbefore are illustrative -Ionly and in no way limiting on my invention as broadly described hereinbefore and in the ap- Vpended claim. Y

What I claim and desire to prot-ect by Letters Patent is:

For use with an electric detonator and its pair of lead wires, where said lead Wires are of a size commonly used in electric detonators and being bare for a portion of their length at the outer ends and being insulated yfor the remainder of their length inwardly to the detonator, a portable shunt consisting of resilient conductive ma.- terial for short-circuiting said lead Wires and adapted to be positioned on said bare Wire portions immediately adjacent said insulated wire portions, said shunt comprising a resilient arcuately curved base portion having a perforation at the vortex thereof diametrically suiilcient to permit passage therethrough of said insulated wire portions, diametrically opposed resilient arms extending outwardly from said base portion in spaced relation to each other and being held in biased relationship relative to each other by means of said resilient base portion, the outer ends of each of said arms being bent at substantially right angles inwardly toward each other to form a gripping element, the gripping elements being positioned in overlapping relation with each other, a lug struck inwardly from one of said arms and positioned between and in substantially parallel relation to said base portion and gripping elements, said lug and each of said gripping'elements having a wire receiving aperture, the apertures being alignable in axial relation with said perforation to receive said pair of bare wire portions, said apertures being of a diameter to permit passage of said pair of bare wire portions and prevent passage of said pair of insulated wire portions thereby permitting automatic and positive positioning of said shunt immediately adjacent said insulated wire portions on said bare wire portions.


Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2725544 *Dec 18, 1951Nov 29, 1955Tinnerman Products IncElectrical terminal clip
US2968786 *Dec 5, 1957Jan 17, 1961United Carr Fastener CorpElectrical assembly
US3645445 *Feb 18, 1970Feb 29, 1972Tyco Ind IncTrack for model vehicles
US4206960 *Apr 5, 1978Jun 10, 1980Component Manufacturing Service, Inc.Electrical connector
US4639060 *Apr 30, 1984Jan 27, 1987Raychem CorporationHeat recoverable connector
US6874424 *Apr 8, 2003Apr 5, 2005Samuel Walters BaileyLow voltage pyrotechnic igniter assembly
U.S. Classification102/202.3, 439/387, 102/202.12
International ClassificationF42B3/00, H01R4/48, F42B3/182
Cooperative ClassificationF42B3/182, H01R4/4845
European ClassificationF42B3/182, H01R4/48B4