US2954735A - Pyrotechnic timers - Google Patents

Description

Oct. 4, 1960 H. ELLERN EIAL PYROTECHNIC TIMERS 2 Sheets-Sheet 1 Filed July 14, 1958 HG. 5 23 INVENTORS.

HERBERT ELLERN DONALD E. OLANDER ATT' Oct. 4, 1960 H. ELLERN ETAL PYROTECHNIC TIMERS 2 Sheets-Sheet 2 Filed July 14, 1958 Ill INVENTORS. HERBERT ELLERN BY DONALD E OLANDER ATTY.

2,954,735 Patented Oct. 4, 1960' PYRGTECHNIC TMERS Herbert Ellern, Ferguson, and Donald E. Olander, Florissant, Mo., assignors to Universal Match Corporation, Ferguson, Mo., a corporation of Delaware Filed July 14, 1953, Ser. No. 748,227

Claims. (Cl. l0285) This invention relates in general to ordnance devices and, more particularly, to certain new and useful improvements in pyrotechnic timers.

In order to time a series of events for pyrotechnic or explosive purposes in an interval exceeding several seconds and to include the one to five minute range, it is customary to employ delay trains which usually consist of either a tubular cord having a core of modified black powder, or a powder-impregnated string. These delay trains provide a linearly advancing flame and are fabricated in lengths of several hundred feet so that delay times ranging from a few seconds to many minutes can be achieved, depending upon the length of cord or string used. However, fuses of this character are particularly vulnerable to moisture, and are also greatly dependent upon ambient gas pressure, including the relatively large quantities of gases chemically created during burning. Consequently, fuses of this type are generally unsuitable for packaged items and especially for the relative precision and reliability needed in military applications. Moreover, for delay times within the range of several seconds to several minutes, the length of the fuse becomes excessive and since, in military pyrotechnical devices, the packaging and space requirements are limited, the arrangement of the fuse becomes a serious problem due to the necessity of preventing pressure build-up within the delay powder-column and also the need for adequate dissipation of heat as the delay train is consumed. Therefore, if the delay train is packaged in a relatively small amount of space, the heat and gas pressure gencrated may speed up the pyrotechnica-l reaction to a multiple of its normal rate. Compressed powdercolumns of low-gassing powder mixtures are equally unsuitable if columns exceeding a few inches in length are employed. These problems have, thus, up to now, remained unsolved, particularly in view of the additional requirement that the entire delay system must be hermetically sealed for purposes of surveillance, as well as to achieve unvarying function at all atmospheric pressures and to prevent excessiveheat-accumulation within the delay system and the adjoining components in association with which the delay system is used.

It is, therefore, the primary object of the present invention to provide a pyrotechnic timer which is completely enclosed and hermetically sealed to the outside and which will function reliably throughout a relatively wide temperature range and over an extended time-interval.

It is also an object of the present invention to provide a pyrotechnic timer of the type stated which is relatively small in volumeand at the same time will prevent speedup of the pyrotechnical reaction due to excessive gas pressure build-up or heat.

It is an additional object of the present invention to provide a pyrotechnic timer of the type stated which will furnish relatively long delay times notwithstanding that the device is of relatively small volume.

It is a further object of the present invention to provide a pyrotechnic timer of the type stated which permits a selection of operating delay times.

It is another object of the present invention to provide a pyrotechnic timer of the type stated which is relatively simple in construction and is extremely reliable in operation.

With the above and other objects in view, my invention resides in the novel features of form, construction, arrangement, and combination of parts presently described and pointed out in the claims.

In the accompanying drawings (two sheets)- Fig. 1. is a perspective view of a pyrotechnic timer constructed in accordance with and embodying the present invention;

Fig. 2 is a top plan view thereof;

Fig. 3 is a sectional view taken along line 3-3 of Fig. 1, the device being shown unfilled in order that the interior construction may be more clearly illustrated;

Fig. 4 is a sectional view taken along line 4--4 of Fig 3;

Fig. 5 is a sectional view taken along line 55 of Fig. 2;

Fig. 6 is a front elevational view partly broken away and in section, and showing the device as it appears when filled wit-h pyrotechnic composition and noncombustible fibrous material;

Fig. 7 is a sectional view taken along line 77 of Fig. 6;

Fig. 8 is an exploded fragmentary perspective view illustrating the construction of the bottom or terminal end of the pyrotechnic timer; and

Fig. 9 is a diagrammatic view of a modified form of pyrotechnic timer.

Referring now in more detail by reference characters to the drawings which illustrate a practical embodiment of the present invention, A designates a pyrotechnic timer comprising a hollow cylindrical canister 1 provided on its opposite ends with. snug-fitting top and bottom cover discs 2, 3. Interposed between the cover disks 2, 3, and canister 1 are annular sealing rings 4, 5, so as to form an hermetically sealed container, and the cover disks 2, 3, are centrally recessed and provided with aligned holes 6, 7, for receiving an elongated bolt 8 having a nut 8' thereon by which the cover disks 2, 3, are held snugly against the canister 1. Formed in the inside face of the top cover disk are three recesses 9, 10, and 11, the recesses 10, 11 comunicating with each other by means of a connecting groove 12. Similarly formed in the inside face of the bottom cover disk 3 are recesses 13, 14, and 15, which are, respectively, axially aligned with the recesses 9, 10, 11, and the recesses 13, 14, communicate with each other through a groove 16.

Secured at its opposite ends in the recesses 9, 13 and extending between the cover disks 2, 3 is a tube 17, preferably of copper, and provided on its upper or starting end with a series of vent holes 18. Adjacent the upper end of the tube 17 the cover disk 2 is provided with a hole 19 for receiving a potted squib 20 which is sealed in place by a superimposed barrier disk 21, and extending outwardly from the squib 20 and through the barrier disk 21 are electrical starter wires 22. While the squib 2G is illustrated as being electrically initiated, it should be understood that a percussion or heat-sensitive primer may also be used. Mounted in the recesses 13, 14 and groove 16 is a plate-like combustible pyrotechnic crosslink 23 which is disposed across the bottom end of the tube 17 and also across hte bottom or starting end of a tube 24, similar to the tube 17 previously described, and provided at its bottom end with a plurality of vent holes 25. The tube 24 is positioned within the recesses 14, 10 and extends in spaced parallel relation to the tube 17.

' 3 and disposed across the upper or terminal end of the tube 24 is a pyrotechnic cross-link 26, the latter being mounted in the recesses 10, 11 and groove 12. The cover disk 2 is provided with a tapped hole 27 for receiving a threaded plug 28 for allowing fire tra-nSfe'r to the outside and for purposes presently and more fully appearing. Mounted in the recess 11 and endwise across the pyrotechnic cross-link 26 is a third tube 29, similar to the tubes 17,24, and provided at its upper or starting end with a plurality of vent holes 30. The tube 29, furthermore, extends downwardly into the recess 15, and the cover disc3 is bored for receiving a sleeve 31 which is adtures. The cross-links 23, 26, are formed of a low gass ing first-fire composition. In this connection, it should be noted thatsuch powder mixtures are well known, as shown in United States Patents Nos. 2,450,892, 2,457,860, and 2,696,429, and are, therefore, not described in detail. Moreover, the present invention does not reside in the 'use of any specific chemical composition or compositions,

but, rather, resides in the mechanical arrangement and utilizations of mixtures of the general type specified.

The space surrounding the tubes 17, 24, 29, is preferably filled with noncombustible flufiy fibrous material 34, such as mineral wool or expanded mica. The tubes 17, 24, 29, are of smaller diameter than the recesses 9, 19, 111, 13, 14, 15, and the spaces between the'tubes 17, 24, 29, and the walls of the recesses 9, 10, 11, 13, 14, 15, are also packed with fine metal wool 35 or other noncombustible material. Inwardly of and adjacent the barrier disk 32, the sleeve 31 may be filled with a gaseous propellant type material 36 which, when ignited, will blow out the barrier disk 32. Alternatively, if desired, the terminal fire-transfer from the tube 29 may be eliected by means of a permanently sealed disk having a hot pyrotechnic composition of the so-called first fire type on the inside and a similar composition or heat sensitive primer on the outside.

In use, the squib 20 is fired from a suitable source of current (not shown) which is connected to the wires 22. so as to ignite the composition 33 which progressively burnswithin the tube 17; As the flame or glow front reaches the end of the tube 17, it will ignite the pyrotechnic cross-link 23 which will, in turn, burn and ignite the composition 33 at the lower or starting end of the tube 24. Thus, the pyrotechnic cross-link 26 provides lateral flame and glow transfer between the terminal end of the tube 17 and starting end of the tube 24. The glow front then progressively advances through the tube 24 to its terminal end, then laterally across the pyrotechnic cross-link 26, and thereafter downwardly through the tube 29 so as to ignite the composition 36 and blow out the barrier disk 32. The composition 36 will, of course, provide fire-transfer to the outside for purposes of igniting a suitable rnain charge.

- The presence of the holes 18, 25, 30, at the starting ends of the tubes 17, 24, 29, permits venting of the reaction-gases into the'main cavity of the canister 1 and, therefore, prevents build-up of excess gas pressure within the tubes and allows steady progression of the reaction without undue acceleration. 'The packing material 35 prevents false fire-transfer between vent holes since it will cool escaping gas as well as entrap hot or ignited solid particles which may be emitted from the vent holes as the reaction in the tubes proceed. Sincethe're is a significant amount of radiation and convection of heat lflrom tube-to-tube, the material 34 will reflect and absorb eat.

fluffy, it occupies a relatively small volume and thus 1 into which the reaction gases can expand;

At the same time, however, since the material is If desired, the plug 28 may be removed to allow firetransfer to the outside at the terminal end of the tube 24, thus providing a choiceof two periods of delay.

Furthermore, if desired, upon removal of the plug 23,

a suitable squib containing a gaseous, propellant composition may be inserted into the hole 27. It will be apparent, however, that plugs or similar sealing members may be secured within the cover disks 2, 3, at the terminal end of each tube/17, 24, 29 so that various delay periods maybe selected. Moreover, while the canister 1 is illustrated as containing three tubes or delay columns,

it will be obvious that. a greater or lesser number of tubes can be employed therein. v 4 7 It is also possible to arrange several complete delay trains within a single'canister .37.which are parallel connected, as diagrammatically illustrated in Fig. 9. The tubes 38, 39, 40, 41, 42, 43, are mounted in the canister 37 in the same manner as the tubes 17,24, 29, previously described, and the upper or starting'end of the tube 38 is connected to the upper ends of the tubes 39, 42 by pyrotechnic cross-links 44, 45. At its lower or terminal end the tube 38 is closed oif by a suitable,

plug or disk 46 for optionally permitting fire transfer to the outside of canister 37. The lower end of the tube 39 is connected to the lower end of the tube 40 by a pyrotechnic cross-link 47, and, similarly, the upper end of the tube 40 is connected to the upper end of the tube 41 by a pyrotechnic cross-link 48. The terminal end of the tube 41 is closed off by a plug or disk 49 similar to the plug 46. The lower ends of the tubes 42, 43 are connected by a pyrotechnic cross-link 50 and the upper end of the tube 43 closed by a plug 51. The initiation of the delay trains may be eiiected by a squib 52, similar to the squib 20. Upon firing of the squib 52, the crosslinks 44, 45 and powder in the tube 38 will ignite and advance the glow front in each train. Since the plugs 46, 49, 5-1 close 01f the terminal points of each delay train, any preselected plug may be removed to allow fire transfer to the outside, depending upon the delay time desired.

Pyrotechnic timers of the foregoing type will function reliably at temperatures between 100. F. and +200 F. and will furnish delay times of as much as five minutes, depending upon the powder'used. At the same time, the delay trains can be housed in a sealed container of relatively small volume. Furthermore, while there is no specific maximum limit to the delay time furnished by the present pyrotechnic timers, it has been found that for delay times considerably in excess of five minutes, the size of the canister 1 is necessarily quite large and bulky. g

It should be understood that changes and modifications in the form, construction, arrangement, and combination of the several parts of the pyrotechnic timer may be made and substituted for those herein shown and described without departing from the nature and principle of our invention.

Having thus described our invention, what we claim i and desire to secure by-Letters Patent is:

l. A pyrotechnic timer comprising a closed canister having rigid walls of sufi'icient strength to withstandthe expansive forces generated by the pyrotechnic reaction when initiated, 'a plurality of spaced tubes permanently and rigidly mounted within said canister and each containing a pyrotechnic delay composition, said tubes collectively occupying substantially less than the total space within the container, each said tube being vented atone end to'the interior of the canister, and pyrotechnic flametransfer means connecting the ends of said tubes in such a manner as to form at least one continuous pyrotechnic delay train. i

2. A pyrotechnic timer comprising a closed canister having rigid walls of 'sufiicient strength to withstand the expansive forces generated by the pyrotechnic reaction when initiated, a'plurality of'spaced tubes mounted 'permanently and rigidly within said canister and each containing a pyrotechnic delay composition, each said tube being vented at one end to the interior of the canister, and a pyrotechnic cross-link disposed across the ends of the tubes in such a manner as to form at least one continuous pyrotechnic delay train.

3. A pyrotechnic timer comprising a closed canister having rigid Walls of sufiicient strength to Withstand the expansive forces generated by the pyrotechnic reaction when initiated, a plurality of spaced tubes mounted permanently and rigidly within said canister and each containing a pyrotechnic delay composition, each said tube being vented at one end to the interior of the canister, a noncombustible fluffy material disposed in said canister in the space surrounding said tubes, and a pyrotechnic cross-link positioned across the ends of the tubes in such a manner as to form at least one continuous pyrotechnic delay train.

4. A pyrotechnic timer comprising a closed canister having rigid Walls of sufficient strength to withstand the expansive forces generated by the pyrotechnic reaction when initiated, at least one tube mounted permanently and rigidly within said canister and containing a pyrotechnic delay composition, said tube being vented at one end to the interior of the container, a noncombustible fluffy material disposed in and substantially filling said canister, and means for igniting said pyrotechnic delay composition.

5. A pyrotechnic timer comprising a closed canister, a plurality of spaced tubes mounted within said canister and each containing a pyrotechnic delay composition, each said tube being vented at one end to the interior of the container, a noncombustible fluify material disposed in said canister in the space surrounding said tubes, a pyrotechnic cross-link positioned across the ends of said tubes in such a manner as to form at least one continuous pyrotechnic delay train having an initial and terminal end, means for effecting fire transfer from said terminal end to the exterior of the canister, and a closure member on said canister for optionally permitting fire transfer to the exterior of said canister intermediate the initial and terminal end of the delay train.

6. A pyrotechnic timer comprising a closed canister provided with end-closure disks, said disks being provided with a plurality of recesses presented toward the interior of said canister, groove means connecting said recesses, a plurality of spaced tubes mounted within said canister and having their opposite ends projecting into said recesses, each tube containing a pyrotechnic delay composition and each being vented at one end to the interior of the container, a plurality of pyrotechnic crosslinks positioned in said recesses and grooves and disposed across the ends of said tubes in such a manner as to form at least one continuous pyrotechnic delay train having an initial and terminal end, means at said initial end for igniting said delay train, and means at said terminal end for effecting fire transfer to the exterior of the canister.

7. A pyrotechnic timer comprising a closed canister provided with end-closure disks, said disks being provided With a plurality of recesses presented toward the interior of said canister, groove means connecting said recesses, a plurality of spaced tubes mounted Within said canister and having their opposite ends projecting into said recesses, each tube containing a pyrotechnic delay composition and each being vented at one end to the interior of the container, a noncombustible material filling said canister in the space surrounding said tubes, a plurality of pyrotechnic cross-links positioned in said recesses and grooves and disposed across the ends of said tubes in such a manner as to form at least one continuous pyrotechnic delay train having an initial and terminal end, means at said initial end for igniting said delay train, and means at said terminal end for effecting fire transfer to the exterior of the canister.

8. A pyrotechnic timer comprising a closed canister having rigid walls of sufficient strength to Withstand the expansive forces generated by the pyrotechnic reaction when initiated, a plurality of spaced tubes mounted permanently and rigidly within said canister and each containing a pyrotechnic delay composition, each said tube being vented at one end to the interior of the canister, loosely packed steel wool disposed in said canister in the space surrounding said tubes, a pyrotechnic crosslink positioned across the ends of the tubes in such a manner as to form at least one continuous pyrotechnic delay train.

9. A pyrotechnic timer comprising a closed canister having rigid walls of sufficient strength to Withstand the expansive forces generated by the pyrotechnic reaction when initiated, a plurality of spaced tubes mounted permanently and rigidly within said canister and each containing a pyrotechnic delay composition, each said tube being vented at one end to the interior of the canister, a body of loosely packed material of the class consisting of mineral wool, metal wool, and expanded mica, said body of material being disposed in said canister in the space surrounding said tubes, and a pyrotechnic crosslink positioned across the ends of the tubes in such a manner as to form at least one continuous pyrotechnic delay train.

10. A pyrotechnic timer comprising a closed canister having rigid Walls of sufficient strength to withstand the expansive forces generated by the pyrotechnic reaction when initiated, at least one rigid-Walled tube mounted permanently and rigidly within the said canister and containing a pyrotechnic delay composition, said tube being vented at one end to the interior of the container, a noncombustible fluffy fibrous material disposed in and substantially filling said canister while providing a substantial amount of interstitial space into which the gases of combustion may expand as the pyrotechnic reaction pro gresses, and means for igniting said pyrotechnic delay composition.

References Cited in the file of this patent UNITED STATES PATENTS 39,682 Schenkl Aug. 25, 1863 617,539 Pain Jan. 10, 1899 1,237,816 Rimailho Aug. 21, 1917 1,346,454 Holt July 13, 1920 1,481,677 Blashill Jan. 212, 1924 1,770,921 Hitt July 22, 1930 1,847,268 Schladt Mar. 1, 1932 2,359,777 Moore Oct. 10, 1944 2,757,566 Towell Aug. 7, 1956 FOREIGN PATENTS 4,179 Great Britain 1905 5,654 Great Britain 1909 22,321 Great Britain 1911 439,023 France Mar. 29, 1912

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