US1639906A - Safety blasting cap - Google Patents

Description

Aug. 23, 1927. 1,639,906

N. l. STEERS SAFETY BLASTING CAP Filed March 24; 1925 /Vf ske/1s, fnvenfor Patented Aug. 23, 1927.

UNITED STATES 1,639,966 PATENT oFFicE.

NEWTON I. STEERS, FlWILLIT'IIINGTON',l DELAWARE, ASSIGNOR T0 E. I. DU PONT DE NEMOURS & COMPANY, 0F WILMINGTON, DELAWARE, A COBIPOBATTON OF DELL- wann.

SAFETY BLASTING CAP.

Application mea umn 24, 1925. serial N6. 17,864.

This inventionis in the art of explosives and has particular relation to electric blasting caps. As is of course well understood in the art, such caps comprise a suitable shell loaded with a sensitive and violent explosive,- for example, ulminate of mercury, with suitable conductors leading into the shell, and permanently connected therewith, for conducting an e ectric current to the charge to explode the same. In use, the cap is placed in close relation to the blastin charge of high" explosive to be detonate and the exploding of the cap gives the shock and heat necessary to cause detonation of the charge.

The leads of a cap are generally of considerable length, say ive or six feet. That is to say, they are so long that when the' .cap is carried in the hand in theordinary way the exposed ends of the uncoiled leads are not in the immediate control of the workman, and may come into contact withy a chargedelectric conductor. It is a common practice for the workman to uncoil the leads at semey lace distant from the point where the cap 1s to be used and then to carry the cap to that point, with its wires dragging along the ground. There are often stray currents in the ground, or there are charged rails, or what not, and should the leads come in contact therewith, thel cap may be exploded', resulting in serious accidents and, indeed, death. There are, of course, many othei` circumstances under which accidental explosion due to exposed leads may occur. I have devised a cap with its leads so arranged that dan ers of the type indicated vare eliminated. t is the major ob]ect of the invention to provide such a cap. To this end, and also to improve generally upon devices of the character indicated, the invention consists in the various matters herein; after described and claimed.

.Without restricting the invention thereto, it is described with reference to the embodiment thereof illustrated in the accompanying drawing. In the drawing, Figure 1 is an elevational view of a cap with the leads broken out to economize space, and Figure 2 is an enlarged fragmental plan view showing the manner in which the leads arepreferably arran d in accordance with the 1nvvention. Re erring'nowto the drawing The illustrated cap designated generally as 1, comprises the 2, o

any pIOPel 1113.-

lengths outside the shell; but at their free ends are, for a short distance, without insulation so that they may be readily connected with the terminals of a current supplier, this, of course, being the usual practice.

Now, in accordance with the present in# vention, the leads are shorted at their free ends as indicated at 7. With this arrangement, should the shorted ends come into connection with a current, the current will not pass down the leads to explode the char e. Preferably, the shorting is accomplished y twisting the leads together, this being, I have found, much more satisfactory than interposing a brid e between the leads, both from the point o View of `makin an inexpensive and thorough short and rom the point of view of making a short which can be readily broken by the workman when he desires to use the cap. With the illustrated construction, too, the exposed leads canbe readily shorted throughoutV their exposed portions, it only being necessary to closely twist the leads together throughout such ortions except for the short tips 4", 5b. T us, there is no unshorted length between the short 7 and the insulation. Desirably, and as shown more particularly in Figure 2 at 8, the insulation is carried up a short distance beyond the short or, expressed somewhat differently, the twisting is carried along the insulated portions. This makes doubly sure that there shall be no unshorted portion between the short 7 andl the insulation. In twisting the leads, it is desirable that care be taken to twist them very closely, thereby to bring them into intimate close contact throughout the twisted length, thus to insure a hig ily effective short. When 'the workman wishes 'to operatively connect the cap with a source of current, he merel has toy untwist the leads, thus destroyin t e short, this operation, of course, not eing done until the cap has been placed in position for use.

With this arrangement, even thou h the workman does bring the exposed lea into tainer, said leads having uninsulated portions, with such portionsv twisted together through a substantial lengththereof.

2. In a blasting cap, an 'explosive container, and electric leads from said container, said leads having insulated and uninsulated portions with the uninsulated portions twisted together through a substantial length thereof, with the twisting extending along the insulated portions,

In testimony whereof I aix my signature.

NEWTON I. STEERS.

Images