US3119338A - Delay detonators for priming devices - Google Patents

Description

Jan. 28, 1964 A. R. PISSACROIA 3,119,338

DELAY DETONATORS FOR PRIMING DEVICES Filed July 22. 1960 INVENTOR. ANGELO R, PISSHCRO/A WMMZZ M W United States Patent DELAY DETONATORS FOR PRIMING DEVItIES Angelo Rali'aeie Pissacroia, Colleferro, Italy, assignor to Bomhrini Parodi-Delfino Societa per Azioni, Rome,

Italy, a company of Italy Filed July 22, 1960, Ser. No. 44,797 Claims priority, application Italy Oct. 13, 1959 2 Claims. (Cl. 102-ss The present invention relates to an improvement in delay detonators for priming devices.

It is known that these delay detonators are an essential component of the fuses for those particular types of ammunition where it is required that the explosion will occur after a pre-established time after the projectile has struck its target.

It is known that the common delay detonators use labyrinth paths tending exclusively to increase the transmission time of the explosive wave or particular mixtures having a slowed down detonation speed.

According to the present invention, on the contrary, a thermo-chemical phenomenon is exploited, which involves the projection of incandescent residues of the combustion of the sensitive priming capsule in combination with the complementary action due to the eifect of the flame acting through restricting orifices and the speed of which is adjusted by outer vent holes.

The range of variation of the delays which may be obtained by the detonator according to this invention, which although it is structurally a single type is capable of giving different performances with only a change of certain explosive or dimensional compositions, range from a minimum delay on the order of the ten-thousandth of one second up to values reaching 6 hundreds of a second.

Therefore the improvement of the present invention provides a detonator which has a constant delay time, even if the thickness and material forming the target changes, and even for changes of the impact speed of the fuse within the full range of the speed of the projectile.

Another object achieved by this invention is a minimum size of the detonator within limits which heretofore were not obtainable and particularly a detonator having a diameter of about 4 mm. and which is 12 mm. long or less; therefore this detonator can be used in ammunition of many sizes and calibers.

A further advantage offered by this invention is that the delay time will not change during storage because stable and non-corrosive explosives can be used.

The improvement according to this invention will be further described in one preferred embodiment with reference to the single figure herewith attached showing an axial cross-sectional view of the device.

With reference to the drawing, the device comprises an igniting capsule 1, contained in the hollow substantially cylindrical body of the detonator proper. Said igniting capsule contains the styphnate priming mixture 3 which is impact sensitive and the capsule is provided with two holes 4 and 4' in register with a central aperture 5 in the fore end of the body 2. Between the priming mixture 3 and the anvil 6 whereon rests the mixture is located the paper seal disc 7. The anvil 6 is made of steel and is provided with the transmission holes 8 and 8 which are inclined to the longitudinal axis of the cylindrical body and which each consists of two portions, the portions 8 and 8' having a larger diameter and the portions 14 and 14 having a smaller diameter, the portions 14 and 14 being toward the expansionchamber 13.

Also within the body 2 of the detonator which for instance may be made of tinned brass, is contained the temperature sensitive styphnate transmission charge 9, as well as the detonating explosive charge 10. On the end of the charge 10 is applied a tetryl booster explosive charge 11 which is surrounded by the closure member 12.

The feature of the device which has been thus briefly described in its component parts, resides in that instead of relying upon the explosive Wave of the priming charge 3, the detonation brought about by the combination of the thermal effect of the action of the gas which contacts the igniting surface of the detonator charge 9 and of the mechanical and thermal effect due to the projection of incandescent residues from the combustion of the charge 3, through the two holes 8 and 8' against the heat sensitive mixture 9.

The delay time is mainly a function of the outlet speed of the burned gas from the capsule 3 and of the impact energy of the solid residues from said'capsule which are produced at the moment when it is ignited.

The control of the pressures due to the priming action of the sensitive mixture 9 of the igniting capsule, in the restricted room afforded by the expansion chamber 13 overlying the detonating mixture proper 919 is obtained, according to this invention, by causing on one hand a remarkable decrease of the pressure by venting the products of the primer combustion through the holes 4 and 4' provided in the flat surface of the capsule and providing a restricting action on the passage of the gas from the larger diameter duct portions 8 and 8' into smaller diameter duct portions as shown at 14 and 14".

In the dynamics of the sequence of the ignition phenomena, particular features are required for the detonating mixture 9li0 compressed in the detonator proper. According to this invention said mixture must be such that in the first portion 9 exposed to the combustion products from the capsule 3, through the ducts the priming feature due to the temperature effect will be enhanced, while both sensitivities due to attrition and explosive wave effects are small. Further, in case of longer delays, the variation of the deflagration speed of the initial status of the detonating charge as a function of the variation of the pressure should be a minimum, so that in correct combination with the features adopted for the capsule, for these values of delay, the results will also be very constant.

The efiect of decreasing the diameter of the portion 14 and 14' of the ducts which are closer to the expansion chamber is that this reduced diameter acts as a choke to reduce the time in which sufiicient gases will pass through the duct to ignite the thermally sensitive explosive 9. Reference to any standard handbook will show that the weight of a gas discharged from an orifice is proportional to the coefiicient of discharge of the orifice, the area of the orifice and the pressure of the gas. Where other conditions are the same, the weight discharged will be proportional to the area. It is the weight of gas which is determinative of the time at which the thermally sensitive explosive 9 will be ignited. This is because it takes a given amount of heat to ignite this explosive, which given amount of heat will be conveyed by a given amount of gases from the explosive primer 3. Since the primer 3 remains the same, the pressure upstream of the duct portions 14 and 14' will be generally the same, so that reducing the area of the orifices will reduce the amount of gas discharged therethrough. This of course is the amount discharged per unit of time, so that in order to discharge a sufficient amount to ignite the thermally sensitive explosive 9, the smaller the area of the duct portions 14 and 14', the longer the time to discharge the required amount of gas. Thus the relative amounts of gas passing through the ducts and the orifices can be controlled by the relative sizes of the ducts and the orifices to control the delay time of the detonator.

The present invention has been illustrated and described in one preferred embodiment, it being understood however that constructive changes may be practically adopted without departing from the scope of the appended claims.

I claim:

1. A delay detonator for priming devices, consisting essentially of a hollow cylindrical body open at the rear end and provided with a central aperture at the fore end, an igniting capsule located in the fore part of the hollow body and just inside the said central aperture, said ignit-v ing capsule having a priming mixture therein, an explosive mixture contained in the rear part of the hollow body, said igniting capsule and said explosive mixture being spaced along the hollow body to leave an expansion chamber between them, said igniting capsule having the end facing said aperture provided with holes in register with the said central aperture of the hollow body, and an anvil located in the fore part of the hollow body between the igniting capsule and said explosive mixture and extending into the said igniting capsule on the opposite end to the end having said holes therein and abutting said priming mixture, said anvil having holes between said igniting capsule and the said expansion chamber inclined to the longitudinal axis of said cylindrical body and connecting said igniting capsule with said expansion chamber, said inclined holes each consisting of two portions, one having a larger diameter and the other having a smaller diameter with the portion on the end toward the expansion chamber having the smaller diameter for enabling control of the speed of the flow of the gas generated by the priming mixture through said inclined holes into the expansion chamber, whereby when said priming mixture is ignited it discharges a portion of the gases generated by the priming mixture into the atmosphere through said holes made in the end of the igniting capsule facing said aperture and said central bore and conveys the remaining gas toward the expansion chamber through said inclined holes and the relative amounts of gas can be controlled by the relative sizes of the holes in the capsule and said inclined holes.

2. A delay detonator as claimed in claim 1, in which the said explosive mixture contained in the rear part of the hollow body comprises a front portion of an explosive sensitive to the thermal action of the gases coming from the priming mixture and to the thermal-mechanical action due to the projection of the incandescent residues from the said priming mixture, and a detonating rear portion, there being further provided a booster charge adjacent to the said detonating portion and a cap containing said booster charge and closing the rear end of the hollow body.

References Cited in the file of this patent UNITED STATES PATENTS 547,852 Hathaway Oct. 15, 1895 953,850 Loeble Apr. 15, 1910 1,313,801 Doran Aug. 19, 1919 1,821,608 Babbit Sept. 1, 1931 2,381,900 Graumann et al. Aug. 14, 1945 2,912,934 Baker Nov. 17, 1959 2,926,607 Muller Mar. 1, 1960 FOREIGN PATENTS 20,467 Great Britain 1902 251,874 Great Britain May 13, 1926 286,137 Italy June 2, 193]

Claims (1)

1. A DELAY DETONATOR FOR PRIMING DEVICES, CONSISTING ESSENTIALLY OF A HOLLOW CYLINDRICAL BODY OPEN AT THE REAR END AND PROVIDED WITH A CENTRAL APERTURE AT THE FORE END, AN IGNITING CAPSULE LOCATED IN THE FORE PART OF THE HOLLOW BODY AND JUST INSIDE THE SAID CENTRAL APERTURE, SAID IGNITING CAPSULE HAVING A PRIMING MIXTURE THEREIN, AND EXPLOSIVE MIXTURE CONTAINED IN THE REAR PART OF THE HOLLOW BODY, SAID IGNITING CAPSULE AND SAID EXPLOSIVE MIXTURE BEING SPACED ALONG THE HOLLOW BODY TO LEAVE AN EXPANSION CHAMBER BETWEEN THEM, SAID IGNITING CAPSULE HAVING THE END FACING SAID APERTURE PROVIDED WITH HOLES IN REGISTER WITH THE SAID CENTRAL APERTURE OF THE HOLLOW BODY, AND AN ANVIL LOCATED IN THE FORE PART OF THE HOLLOW BODY BETWEEN THE IGNITING CAPSULE AND SAID EXPLOSIVE MIXTURE AND EXTENDING INTO THE SAID IGNITING CAPSULE ON THE OPPOSITE END TO THE END HAVING SAID HOLES THEREIN AND ABUTTING SAID PRIMING MIXTURE, SAID ANVIL HAVING HOLES BETWEEN SAID IGNITING CAPSULE AND THE SAID EXPANSION CHAMBER INCLINED

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