US2545474A - Delayed detonating means for projectiles - Google Patents

Description

March 20, 1951 J. J. KURLAND ETAL 2,545,474

DELAYED DETONATING MEANS FOR PROJECTILES e Sheets-Sheet 1 Filed Aug. 12, 1943 INVENTORS .kr'ome JKZZ rlaizd March 20, 1951 J. J. KURLAND ETAL 2,545,474

I DELAYED DETONATING MEANS FOR PROJECTILES 6 Sheets-Sheet 2 Filed Aug. 12, 1943 INVENTORS I Jeram e .Zfiill ldlld BY Jos pk .ZKuI-Jand March 20, 1951 J KURLAND ETAL 2,545,474

DELAYED DETONATING MEANS FOR PROJECTILES Filed Aug. 12, 1943 6 Sheets-Sheet 3 INVENTORS .ferome .Zfinrlazzd BY fisgplz .l jf urland March 20, 1951 J. J. KURLAND ETAL 2,545,474

DELAYED DETONATING MEANS' FOR PROJECTILES Filed Aug. 12, 1943 6 Sheets-Sheet 5 INVENTORS filom Harland BY .7059]: JKzzrJand March 20, 1951 Filed Aug. 12, 1943 J. J. KURLAND EI'AL DELAYED DETONATING MEANS FOR PROJECTILES 6 Sheets-Sheet 6 4/ 4 fi/A 05 5 //44 /96 /42 47 ban-5,4144 77m Scale Z/ Z/Z I f Z05 Z/O .Z/ Z06 Z/7 L I I I I I I I I I I I I I Cal/braked 77me Scale 0 INVENTORS .ferome Jfiizrland Joe gr]: .1. I urland Patented Mar. 20, 1951 UNITED STATES OFFICE DELAYED DETONATING MEANS FOR PROJECTILES Jerome J. Kurland and Joseph J. Kurland, Chicago, 111.

3 Claims.

Our invention relates to the detonation of ex plosive projectiles with controlled time delay and is directed to the use of what may be termed a condenser circuit for delayed action in fuses. Such a condenser circuit is charged at some initial potential distribution and is designed for progressive change in that distributilon in such manner as to apply an efiective potential to suitable igniting means after a predetermined time interval.

One of the important problems in designing a time fuse incorporating a condenser circuit is to provide a thoroughly reliable and foolproof safeguard against accidental or premature detonation. It is especially difficult to avoid serious hazard in th act of intially charging the fuse with the necessary potential.

Various safety expedients are known to the art. It has been suggested, for example, that a generator be built into the fuse for operation after the projectile is released, thereby to delay charging of the condenser circuit. Other suggestions have involved mechanical expedients for use during the charging operation or special mechanical relationships between the fuse and the cooperating charging device.

One object of our invention is to meet this safety problem with complete success by simple structural means confined to the projectile and the associated holding means for the projectile. An important advantage of such an arrangement is that a simple and rudimentary charging device, free of complicated safety features, may be employed.

Many of the prior art suggestions may be used for projectiles of relatively large size which afford ample room for elaborate circuit arrangements and for moving parts, but such suggestions cannot in practice he used for projectiles of relatively small caliber, 20 mm. shells, for example. A further object of our invention is to provide a safe and highly efiicient fuse construction'especially suitable for small caliber projectiles, a construction involving no moving parts whatsoever and lending itself to compact design. In this regard, a feature of our invention is the use of cerain safety shunts designed to be opened automatically upon release of the projectile. Various practices of our inventions are based on various novel concepts of how such automatic action may be insured by simple expedients.

In a certain practice of our invention, we have the two-fold object, first, of employing a relatively low charging potential to achieve a relatively high ultimate potential and, second, of

avoiding hazard in the charging operation by employing an igniter that is non-responsive to the initial relatively low potential applied by the charging device.

In designing condenser circuits for the present purpose, it is not difiicult to arrange for accurate delay periods within a narrow range of time periods, especially within a range of relatively short time periods. It is difficult, however, to achieve suflicient accuracy over wide ranges and especially for relatively long time delays. One object of certain practices of our invention is to achieve accuracy over wide ranges of time values by novel arrangements involving the use of two or more variable charging potentials. In one of these practices, it is our purpose to employ one or more auxiliary or modifying condensers for the desired flexibility in time delay. In another teaching, we propose to achieve the desired accuracy and range by a novel form of charging device in which the relative values of two charging potentials are varied automatically for different time adjustments in a succession of time ranges.

More specific objects and advantages of our invention will be apparent in the following description taken with the accompanying drawings.

In the drawings, which are to be considered as illustrative only:

Fig. 1 is a wiring diagram of one arrangement under our concept that may be employed for the delayed detonation of explosive projectiles;

Fig. 2 shows the same diagram modified for elimination of moving parts and for adaptability to small caliber projectiles;

Fig. 3 is a diagrammatic view in cross section of an explosive shell incorporating the electrical arrangement of Fig. 2;

Fig. 4 is a wiring diagram of one of our arrangements involving the use of two safety shunts;

Fig. 5 is a diagrammatic view in cross section of an explosive shell incorporating the arrangement indicated in Fig. 4;

Fig. 6 is a wiring diagram of one of our electrical arrangements involving the use of two different charging potentials with a safety shunt;

Fig. 7 is a modification of the diagram of Fig. 6;

Fig. 8 is a diagrammatic view in cross section showing an explosive shell incorporating the elec trical arrangement shown in Fig. 7;

Fig. 8a is a view similar to Fig. 8 showing a second structural arrangement for incorporating the principles illustrated by Fig. 7;

Fig. 9 is a wiring diagram of another diiferentially charged circuit incorporating a safety shunt;

Fig. 10 is a diagrammatic view in cross section a u of an explosive shell incorporating the electrical arrangements shown in Fig. 9;

Fig. 10a is a view similar to Fig. 10 of another structural arrangement based on Fig. 9.

Fig. 11 is a wiring diagram indicating how one or more modifying condensers may be added to the basic circuit;

Fig. 12 is the wiring diagram of Fig. 11 modified to permit independent charging of the additional condenser;

Fig. 13 is a wiring diagram illustrating our concept of initially charging a fuse nom'a low" potential source and subsequently automatically increasing the potential after the projectile is released;

Figs. 14, 15, 16 and 17 are graphs explaining certain relationships involved in certain practices of our invention;

Fig. 18 is a diagram indicating the construction of an adjustable charging "device based on relationships shown in Figs. 16 and 17.

Fig. 19 is a graph indicating relationships involved' in a second'form of adjustable charging device; and

Fig; 20 is a diagram indicating the construction of this second form of adjustable charging device.

It is to be understood that our invention is widely" applicable to: projectiles, the invention having'utility not only forexplosive shells dis-' charged from guns, but also for such explosive projectiles as aerial bombs, mines of various types, torpedoes andgrenades. The term projectile as used hereinafter covers any of such explosive devices or the like.

In'many practices-of our invention aholding means for a projectile has a special cooperativerelationship with the timing circuits employed for delayeddetonation. The term"holding means may refer to various devices in various practices of our invention and is therefore to be broadly construed; For example, ifthe projectile is shot from a gun, either the shell case or the gun, or both,- may be regarded as the holding means.

If the projectile is an" aerial bomb; the holding means may be a bomb rack or any part of aircraft from which the" bomb is released. It will be apparent that the invention is applicable even to hand grenadessince the'throwers hand or some device-retained in the throwers hand may be the holding means under our concept.

In thesimple'form of our invention illustrated byFig: 1, tank: condenser or ignition condenser 20 is in series with what may be termed a timing condenser'2 l, the two condensers being mutually opposed and beingconnected to a'common ground 22. Interconnecting the potential or chargereceiving terminals of the twocondensers are an igniter 23 and acurrent-blocking means 25 arranged in series. The timing condenser 2| is shunted by a suitable resistance 26 serving a a current-leakage means and may also be shunted by" a wire 2'! controlled by an impact switch 28. For the purpose of charging the condenser circuit, a charging contact 39 is connected to the potential side'of the-condenser 29 by a wire 3! and is connected to the potential side of the condenser 2| by a wire 32, there being a normally closed safety switch 33 controlling" current flow through the wir 32. The safety switch 33 is designed to open automatically'whenever' the projectile is released; In a shell, for example, wemay use an inertia switchthat snapsopen in response to acceleration This actuation of of the shell in the gun barrel. a safety protective device, which, prior to'such actuation, will'normally prevent any current from 4 flowing through the igniter, is referred to as arming of the projectile.

In preparation for release of the projectile, a suitable charging means is applied to the described circuit. In the practice of the invention exemplified by Fig. 1, it is contemplated that the charging means will be in continuous communication with the condenser circuit up to the moment the projectile is released. In Fig. l the charging means is shown as including a charging contact 35 connected to a grounded battery 3?. If the delayed action fuse is not grounded through the holding means for the projectile, the charging means may also include a grounding contact for the fuse circuit. 7 7

As soon as communication between the charging device and th'econdenser circuit is broken by release of the projectile, current leakage through the resistance 26 causes the charge on thetiming'cond'enser' 25 to decrease with a corresponding drop in'potential across the timingv condenser, the charge'on the tank condenser 2i}- meanwhile remaining constant in the absence of i any closed conducting path. As the voltage across the timing condenser decreases, an in-' creasing potential drop is established across the current-blocking means 25. When this potential difference across the currentblocking means reaches a predetermined value, a conducting path is established to permit flow of current from the tank condenser 20 to a lower potential level, such current flow causing the igniter 23 to be energized for detonation of the projectile.

The igniter 23' may be a conventional heat-" ing cap or detcnating. primer, or may be" a'suitable filament such as employed in flash bulbs. The current-blocking means'EE'may be' a gap means such as a gaseous tube'in which the gas closely related in function and may therefore be jointly covered by the term igniter or the term igniting means; in fact, the function of blocking current'and the function ofig'nition proper may conceivably be combined in one element by using an explosive dielectric to bridge'a-gap in the circuit. 7

Fig. 2 is identicalin most respects to Fig. 1, as indicated by the use of corresponding numerals to designate corresponding parts. In this second circuit, however, there is no switch along the wire 33 since it-is contemplatedthat some provision will be made for automatically breaking the wire 33 when the projectile is released. The wire 33 may be broken'at any point, for example, at the dotted line 'yy, or both the wire 33 and the wire 35 may be broken as indicated by the dotted line .rx. The arrangement is especially suitable for projectiles of relatively small caliber as illustrated by Fig. 3.

Fig. 3 shows'a projectile-or shell w'mounted in a case 4!, the projectile containing suitable explosive material and a fuse body 52. The nose of the projectile may'be'provid-ed with an im'- pact plunger fl3 to close the previously mentioned impact switch 28. The charging contact 3B for the fuse circuit'may be of any suitable construction and may be placed at any suitable location. Fig. 3, by way'of example, shows the-charging contact 30 in the form of a concentric metal ring in the base of the case 4|, the ring being suitably insulated from the metal material of the base. The previously mentioned wires 3! and 33 extend from the fuse body 42 through suitable apertures in the base of the shell 40 and are terminally connected to the annular charging contact 30, preferably at spaced points thereof as indicated.

To arm the shell shown in Fig. 3 for delayed detonation, a suitable charging means incorporated in the associated gun construction is automatically brought into communication with the annular charging contact 30, as indicated diagrammatically in "Fig: 3. projectile it is released following detonation of the primer id in the base of the case 4|, the movement of the projectile away from the case causes the two wires 3! and 33 to be broken thereby destroying the safety shunt and making the condenser circuit operative for delayed ignition of the projectile charge.

In the circuit shown in Fig. 4 a tank condenser 45 is connected to a charging contact 46 by a wire 4'1 and a timing condenser t8 shunted by a bleeder resistance 50 is connected to the same charging contact by a wire 5|. Current through the wire H is controlled by a normally closed safety switch 52. The potential sides of the two condensers A5 and t8 are also interconnected in series by a gaseous tube 53 or equivalent current-blocking means. The other sides of the two condensers t5 and 48 are connected to ground by wires 55 and 56 respectively, current through the wire 56 being controlled by a normally closed safety switch 51. The ground sides of the two condensers are interconnected in series by an igniter 58. For instantaneous firing, a wire 60 may connect the potential side of the condenser 45 with the ground side of the condenser 48, current flow through the wire being controlled by a normally open switch 6| designed to close when the projectile strikes an object.

If the circuit shown in Fig. 4 is employed in a projectile of large caliber, the two safety switches 52 and 51 may be inertia switches of a well known type designed to open when the projectile is initialy accelerated. Prior to the opening of the two switches, no operative potential difference can be established across the gaseous tube 53 and no eifective current can flow through the igniter 58. Prior to release of the projectile, a; complementary charging means in communication with the charging contact 46 maintains both of the condensers at the same potential with small current flow continuously through resistance 50 to ground. When the projectile is released thereby breaking communication with the complementary charging means and causing the two switches 52 and 5? to open, the circuit operates in the previously described manner to build up a potential across the gaseous tube 53 and ultimately cause detonation through the igniter 58.

In View of previous discussion, it will be readily apparent that the circuit shown in Fig. 4 may be adapted for small caliber projectiles by omitting the two switches and providing for breaking the shunt wires. Instead of arranging for wires to be broken to open the safety shunts, we may design the projectile for mechanical opening of the shunts incidental to release of the projectile from the holding means.

In Fig. 5, in which we illustrate this latter concept, we show a small caliber shell 62 mounted As soon as the 6 in a casing 63, there being a fuse body 55 inside the shell. At the end of the shell is shown an impact plunger 66 for actuating the previously mentioned impact switch 6!. Fig. 5 also shows how we may arrange the wires 41, El, 55 and 55 of the wiring diagram in Fig. 4. Wires 55, and 56 terminate in two contacts 61 and 63 respectively, these contacts being insulated from the material of the shell 62 but being positioned to touch the metal of the case 63 thereby to provide ground connections. Wires 4! and 5| terminate respectively in two contacts H1 and ll in a socket 12 formed in the bottom of the shell 62. Mounted in the case 63 is a rigid conductor 13 designed to enter the socket I2 and provide 'a conducting path from the two contacts iii and H to the previously mentioned charging contact 45. In this particular construction, the charging contact 46 is in the form of a metal ring mounted in the base of the case 53 with suitable insulation. Fig. 5 shows how the previously described charging means, including the contact 35 and the battery 3? may touch the charging contact 46 when the projectile is placed in a gun.

There are certain inherent limitations in circuits in which a single charging contact is employed for charging both the tank condenser and the timing condenser in the manner described above. Since the charging voltages applied to the two condensers are necessarily equal, time adjustment can be achieved only by varying the common charging voltage. This fact may be readily understood by referring to Fig. 14 in which the curve represents voltage decay across the timing condenser and or represents the striking voltage of the gaseous tube or other currentblocking means incorporated in the circuit. One limitation is that zero time delay can be obtained only by using an infinite initial charging voltage. Another limitation is that the charging voltage must be lowered to increase the time interval so that a relatively long delay period will require that the circuit be operated at a relatively low energy level.

These limitations can be eliminated by charging the two condensers diiferentially. For convenience, an arrangement wherein the condensers are charged equally may be referred to as a simplex circuit and an arrangement providing for differential charging may be referred to as a duplex circuit.

The advantages of a duplex circuit may be understood by referring to 15, in which E2 represents an unvarying voltage applied to the tank condenser in our circuit and the curve of voltage decay represents a range of potentials through which the timing condenser may be initially charged. It is apparent that zero time delay may be obtained simply by charging the time condenser initially with a voltage less than E2 by the amount 'Ut. For a relatively short delay period the initial charge on the timing condenser would be less than E2 by an amount slightly less than Ut. For relatively long delay periods the initial charge on the timing condenser would be higher than the voltage E2. It is clear that a duplex circuit provides a greater range of time adjustment than a simplex circuit without the necessity of dropping to an undesirably low energy level.

Fig. 6 shows a duplex circuit in which a charging contact 15 is connected to the potential side of a tank condenser 16 by a wire T1 and a second charging contact 18 is connected to the potential side of a timingcondenser- 811" by awire' 81, the timing condenser being shunted by a bleederresistancemii. A wire 83'interconnects a gaseous tube 34 and an igniter 85, the tube and igniter interconnecting the potential sides of the two condensers in series. Both of the condensers are grounded as shown. For percussion detonation, an impact switch 86 may controla wire 8'! that extends from the above mentioned wire83' to ground. Our safety shunt for this circuit isushown as a wire 88 from wire 83 to the charging contact 15, current through this shunt wire being controlled bya normally closed safety switch 90.

The mannerin which the circuit sho-wn'in Fig. 6 functions may be readily understood from our previous discussion. For relatively short time delays; the voltage E1. applied to the charging contact 78 is relatively low, this voltage being increased for longer delay periods. If the Cir-"- cuitis employed in a large caliber projectila the safety switch 9%! may be operated by inertia as heretofore suggested.

As heretofore stated, the igniter maybeoonsidered as the igniter 35 proper or the igniter 85 in combination with the gaseous tube 84. 'Accordingly, our safety shunt may straddle the igniter 8-5 alone as shown in 6 orm'ay by-pass both the igniter '85 and the gaseous tube 84 as shown in Fig. '7;

Fig. '7 is largely similar to Fig. 6 as indicated bythe use of corresponding numerals for corre' sponding parts. It will be noted that the safety shuntwire 89 in Fig. '7 is'connected with theterminalof the gaseous tubexB'd on the side towards the timing condenser 8E} and that a resistance 95 is introduced between the gaseoustube and. the timing condenser.

The advantage of the arrangement in Fig. '7" over the arrangement in Fig. 6 is that the potential E2 is applied-to both sideso'f the gaseous tube and therefore cannot cause the tube'to strike in course ofthe" charging procedure. The resistance 94 is introduced because'the d'ifierence in potential between E1 and E2 necessarily exists between the gaseous tube and thetiming condenser.

Either the circuit of Fig. 6 or the circuit of Fig. 7 may be incorporated in asmallcaliber projectile, the shunt switches being omitted and means being provided to break the shunt wires. Fig. 8, for example, shows how the circuit of Fig. 6 may be used in a small caliber shell.

Fig. 8 shows the usual shell 9i mounted in. a case 92. inside the shell 95 is a fuse body 93 and the above mentioned impact switch 86 positioned for actuation by an impact plunger 95. The charging contacts '55 and 18 of Fig. 7 may be mounted anywhere on the holding means or case 92. By way of example, Fig. 8 shows the two contacts 55 and is in the form of suitably insulated metal rings exposed on the periphery of the case 62. A wire at is shown connected to. the metal shell of the projectile St for the purpose of grounding the two condensers l6 and 80. Also shown in. Fig. 3 are wires i7, 8! and 88 of the. diagram in Fig. 7, wire 8i being connected to the ring-shaped contact l8 and wires Ti and 88 being connected to the other ring-shaped contact 15.

When the projectile shown in Fig.3. is'placed in a gun, a suitable charging means is automatically brought into electrical communication with the two ring-shaped contacts. T-andl8 asindicated diagrammatically in Fig. 8. When. the

pfoiiectile' is feleas'edby detonation -o e: material in'the ca'segztlie threewir's-fi, 8i rid se r'e 'automaueany broken. The f'rhanfier-in which the cirouitfurictions thereafter foddelayed deto'nation' is" apparent. I

*While Fig. 8 shows the twocnar'ging contacts 15-" and! 8 mounted on the case '92-, these charging-contacts maybe mounte'don the'projctile 9|. Fig. 8a indicates how the arrangement ih 8 rnay be modified to shift'the contacts from the'casef-to'theshell. Note that the case 9 in this fi'gure' is of conventional-constructionthere being no necessity for modifying the case many manner. 7 g p The projectile 98 in Fig. 8 a is provided with twodnsulatedi exterior rings toserv'e as contacts T5'and l8respectiv'ely. The'ground wire 96 from the fusebody 831s conn'cted as before to'the rh'aiter-iaro'f theprojeo'tile. Wire BI is connected to t-he npper ring '53 and wires 'lTand BBarebOhnected to the: lower ringv 75.

A feature of the arangement shown in Fig. 8a is the'concept-of makingthe wire 83 relatively longwso that the wire may be passed through suitableapertures in thebottom of the'projectil'e to-form-a loop mil in the interior of the case 97. The purpose of providing such a loop is to make thes'afety shunt wire 88 vulnerable to the ex"- plosion that propels the projectile. It is con templated that the explosion will de'stroya't least a portion of the wire formingthe loop H10 thereby opening the safety shunt; Whiienoiurther p'ro vision for' brea-king the shunt isnecessariy; some means may be provided onthecase Q'i to engage theloop insure mechanical severance of the Wire as the projectile -leavesthe:'case. For example, a pin or hook It! may be-mounted on the interior of the case 9"! to extend through th e loop [00.

Fig. 9; illustrating anotherarrangemen tof our duplexcircuit, shows;a charging contact I02 connected by awire N33 to the 'potential'sideof a tank condenser r and-"shows achargingv con tact: H18 connected tothe potential :side'of atimingcondenser it? by a wire M8; the timing condenser being shunted-by the usual bleeder resistance it. The potentialsides-of the two condensers are-connected in series with a gaseous tube: I] I and the ground sides of the two condensers. are interconnected in series by an igniter iii In this particular circuit our safety shunt is on the ground side ofthecondenser-s: By way ofe'xampl'e, weshow a wire i lt for grounding the tank condenser lile and a second 'wire H Sgrounding. the. timing condenser IU-l. A safety switch- We is. shown forbreaking currentthrough the wire H5 but obviously such a switch may be employed to control current through wire'l l3 instead. Forihstahtaneous detonation; we show a shunt across the condenser Hi1 controlled by an impact switch- H7.

It the circuitof'Fig. 9 is employed: in alargecaliber projectile, the safety switch may be 013-- elatedby inertia or in any other automatic man ner. On the other hand, if it is desirable to omitthe safety switch, provision may be made to break either or both of the two wires-l l3 and l l5.

The provision for breaking the wire or wires ofthe safety shunt on the ground side in Fig.9 may be in accord with any of the teachings exemplified by Figs. 3; 5, 8'ancl' 8a.. Thus, in Fig; 10 we show an arrangement inwhich both wires 3i and H5" are isolatedmechanically when the projectile is released. I m

Fig. 10 showsa projectile H8 mounted in a case H9 in the usual manner.

The projectile contains the usual fuse body I23, above which is shown an impact plunger I2I for closing the previously mentioned impact switch '1. The two grounding wires H3 and H5 terminate respectively in two insulated contacts I22 and I23 positioned on the periphery of the projectile II8 to touch the metal surface of the case H9. As heretofore suggested, the charging contacts I52 and I96 of the circuit in Fig. 9 may be placed anywhere on the case H9. In the present construction, the two charging contacts I62 and I06 comprise two insulated concentric metal rings in the base of the case I I9, one ring being connected to wire I63 and the other ring being connected to wire Hi8.

The manner in which the arrangement in Fig. 10 functions may be readily understood. When the proiectile H3 leaves the case N9, the two wires I83 and. WE are automatically broken, and

the ground connections shunting the igniter are opened by movement of the contacts I22 and I23 away from the case.

The purpose of Fig. 100: is to indicate how the arrangement in Fig. 10 may be modified to place both of the charging contacts on the projectile. The two charging contacts I02 and IE6 are in the form of insulated rings, wire I03 being connected to the ring I 02 and the wire I 68 being connected to the ring I06. Since the two rings I52 and I36 are insulated from each other, it is not necessary to break the wires I03 and I55. Both of the wires H3 and H5 are connected to the metal material of the projectile for grounding but at least one of the two wires is arranged for automatic severance. Thus Fig. 10a shows the wire H5 connected terminally to the projectile but passed through suitable a erture through the projectile to form a loop I25 in the interior of the case. As heretofore suggested, a pin or 'hook I26 may extend from the case through the loop I25 but it is not necessary.

The purpose of Fig. 11 is to exemplify our concept of incorporating in a duplex circuit one or more modifying condensers to affect the rate at which potential drops across the timing condenser thereby to vary the period of time delay. Those skilled in the art will rea ily understand that the addition of such modifying means affords additional flexibility in the operation of the circuit.

In Fig. 11, a charging contact I2! is connected by a wire I 2-8 to the potential side of the tank condenser I3!) and a second charging contact i3I is connected by a wire I32 to the potential side of a timing condenser I33, the timing condenser being shunted. by the usual bleerer resistance I35. A suitable gaseous tube I 35 is shown in series with the potential sides of the two condensers while an igniter I3! is shown in series with the ground sides of the condensers. Wires I45 and HH ground the tank and timing condensers respecively. The circuit as described to this point will be recognized as corresponding to Fig. 9.

We show only one auxiliary or modifying condenser I 42 in Fig. 11 but it will be understood that any number of such additional condensers may be employed. A wire I43 connects the potential side of the timing condenser i333 with the potential side of the modifying condenser I 42 and a suitable bleeder resistance I45 condenser connects the ground side of the modifying condenser with the ground side of the timing condenser. The ground side of the modifying condenser I42 is connected to ground through a wire I46.

It is apparent that the modifying condenser I42 will be initially charged with the same potential E1 as the timing condenser I33 and that the modifying condenser, like the timing condenser, will have its charge opposed to the charge on the tank condenser I30. If this circuit is incorporated in a projectile, some means is provided for cutting off the three condensers from each other, for example, by severance of the three wires I 40, I M, and I 45 along the line :r-.r by any of the various expedients heretofore suggested.

When the projectile having the circuit in Fig. 11 is released, thereby isolating the charging contacts I21 and I3I from each other and thereby breaking the three ground wires, current fiows through the resistance I to lower the potential difference across the timing condenser I33. The rate at which this potential difierence decreases, however, is modified by current flow through the bleeder resistance I from the modifying condenser I42. Ultimately the voltage opposing the charge on the tank condenser I30 decreases until detonation occurs.

Fig. 12 shows a variation of Fig. 11 corresponding parts being indicated by corresponding numerals. Fig. '12 differs from Fig. 11 in providing for independently charging a modifying condenser I4'I so that three different potentials may be employed for adjustably varying the period of time delay. In addition to the charging contacts I21 and I3I previously mentioned, the circu t includes a third charging contact I48 that is connected by a wire I50 to the potential side of the modifying condenser MI. The potential sides of the timing condenser I33 and the modifying condenser I 41 are interconnected by a bleeder resistance I 5| and the ground sides of the two condensers are interconnected by a wire I52. The manner in which the circuit functions may be understood without further explanation.

Fig. 13 illustrates our concept of how a relatively low charging potential may be employed in the field to provide a relatively high igniting potential after a projectile is released, the increase in potential being accomplished by shifting a plurality of condensers from parallel relation to series relation. Fig. 13 shows a plurality of ignition or tank condensers, there being, for example, three such condensers I53, I54 and I55. The potential side of the tank condenser I53 is connected by a wire I51 to a charging contact I58 and is connected by a wire I60 to one side of an igniter I6I. The tank condenser I54 is connected on its potential side to a charging contact I62 and a switch contact I63. In like manner, the tank condenser I 55 is connected on its potential side to a charging contact I65 and a switch contact I66.

The ground side of tank condenser I53 is connected to a switch member I61 that normally rests against a grounded contact I68 but is adapted to swing automatically against the switch contact I63 when the projectile is released from its holding means. In like manner, the ground side of the condenser I54 is connected to a switch member III that initially rests against a grounded contact III but subsequently swings automatically against switch contact I66. The third tank condenser I55 is permanently grounded. It is apparent that the arrangement provides for initial parallel charging circuits through the three tank condensers I53, I54 and I55.

To complete the final ignition circuit, the second side of the igniter I6I is connected by a Jilil -wire- H3 to-asuitable gaseous tube: I15 and-:the gaseous .tube is-connected linrturn by :a :wire: H6 1 to: the potential side of a: timing condenser Ill. .The timing condenser l'l'|,*which is: shunted-by the,,usua1 timing-resistance 1-80, is connected on .its,;potential siderto a charging contact WI: and connected to-ground one the otherside by -.a wire !82. Asafety switch -I83"may be employed connected so as to shunt the igniter 16!.

Fig. -'13 showsvdiagrammatically -a charging meansin which four :contacts corresponding to the (four charging-contacts 158,162,. [GS-and 18! of the circuit are all'energ-izedat-thesamepotentialby a common battery H2, the battery. affording a relativelyilow potential.

"of: our invention, however, the vario-uscondensers may bechargedatidifierent potentials.

'Whenthe projectile-is.released from. its. holding-:means, the four-chargingcontacts become isolated fromr-each other :and. the two switches ltliand H are operated by-inertiapr othenauto- "ma-tic i actiontoa-shift the; plurality ,-of tank condensers from parallel relation-to=series relation -therebytadding. :thecharges .to. produce-.- a relatively high potential across :ithecci-rcuit. opposed byuthecha-rge onazthetim-ing condenser Ill. As .has previously ,been described, they "release. .of .the -,projecti-1e.wi-1l o erateto'open the normallyclosed safety switc.h;l8,3,. onto-sever the igniter shunt ..wires along the line vs-+43, T thereby-serving to iarm the projectile. .The opposing -potent ial across the timing condenser ,progressively l -dewcreasesbecause of: current flow through. the resistance i803 and eventually the. high potential across the tank, condenser :becomes effective-to I lump-a across the gaseous tube l and, detonate .the igniter l BI.

,Fol'racclllafly instime measurement .by our du- -..plex circuit the-slope of-a curve of voltage values plotted {with respect to timeshould .be such-that -given voltage .di-fierences represent commensurate differences :inatime periods. Ifltheucur-ve -is too steep, a; given change. in potential represents .an .undesirablysrnall. change-,in time; :on the. other ..hand, .the same change; -in .potential along .a

flattened. curve 1 represents ..an excessively glarge change, in time.

We have found-that for accurate. time-control different relationships :between- E 1, the timingcondenser charge, and -;"E2, the tank; condenser .Chalge, .must :be employed in difierent time -ranges. .Thusi for-accuracyin.- an.-.initial, range .of relatively. short time periods, E2 must'be relativelyhigh, whereas over-.aa range of relatively longtime periods :52 must be relatively low. We ..have: 'further. discof/eredtthatv these tWot.-extr.eme ranges of time changes. may be correlated in such manner as to afford a smooth and graduali-proig-ression of [time values. Gnesmanner- -of ...corre- -lating the two extreme. ranges 10f time; changes .is by introducingra mid. range.

The graph in-Fig. lfirshows an initial range V of relatively-small timepriods in whichrEz is relatively; high. Itr-is assumedpbyway'of illus-- tration, that-in a.- .particular duplexcircuit the striking voltage 115 of the gaseous tube-is 400 volts and that E2. throughout the initial range is maintained atHQOO volts, E2 noinus we equalling 500 volts. .ln the: midrange-of time-values E2 substantially equals E1, both. diminishing progresrsivelyas indicated. Since, Ezis'constant over the initial= range and since E2 substantially equals E1 at the end or" the initial range, variation in time-overtheinitial range is produced by variation inthe value;-of:E1,-.E1-,being:relatively low. for

In some practices s12 sinstantaneous ignitioniand' rising to substantially eequaleEz at. the El'ldsOf this initial time range.

lathe final. range aof relatively long-timeperiods,;-E2 is again: held substantially constant at varelatively lowivalue (Ezminus mequalsj v.) .and variations inztime. are again produced by variationsin the value in'Ei. At the startoithis 11finalrange,- E1 substantially equals "E2 but; with increasing time values OVGI'ilJhB range, E1 31)]?0- 9gressively rises' above --E2.

Figs; 17 shows graphically .the. relation between the char-ging' -voltages- E1.- and 1E2 over the-three ranges of'timeF-adjustment.

;'In--F -ig. 118 we indicate diagrammatically how a rheostat; arrangement a-may-be :employedqin a charging device to apply potentialsiaEl and-E2 -select-ivel-y for any desiredvalue over the: three :ranges of time. A: control member shown in? dotted, lines carries a first brush or :wiper -l 86 that-is'connectedi toaa charging contactEcby-a .wire Island also carries a-second brush'orawiper lSiPthat; is connected by a wire I9B to ascha-rging contact E2. Movement of the control member S51with-referenceto a timescalelercausesgthe =-,wiperi 36 to: traverse arheostat-resistancergenerally designated +92:- and simultaneously causes the -wiper N38 to traverse a; second-rheostat resistance generally designated?! 93.

The rhecstat resistance r l 92:" for c.0ntro11ing;-po- .=.tential;-E1:.isdivided intoath-ree; ranges by: con- :nection with a low voltage-awire z 233 and ahigh voltagewire its; the ranges corresponding, to the previouslymentioned initial,- mid? andfinar -time ranges. The initial-time-rangeg is-defined iby a lowvoltage -connection-l95 and: a high voltage :connection' the' midrange is defined by the high voltage connection 1'98 1* and a secondlow Voltage connection; I 91'; and the final-time range =is:-defined:by the low voltage connection 191 and --t-hesecondihighvoltage-connection1 I98. lihus,

the potential E 1 rises progressively as the control member I85 movesgto-the right until azmaximum -valuewis reachedaat connection 196 whereupon potential -E1 drops progressively until contact lEi'lf'iS reached and finally 'thepotentialrrisesto the maximum' again at connection.- I 98.

"The" rheostatresistance 193. comprises a -con- ,tactzZddextending over the initial timerange -a resistance 2ll extending over the midrange, and arsecond contact 292 extending over @the final time range. The contact 290, the resistance 'zfll, and the contact 2:02. are in series; the contact 280 :being'connecte'd to the high-voltageiwire i 94' and the'contact' 2.52 being-connectedto the low. voltage wire:203. By virtue of thisarrangement; the "potential E2 varies'in the desired-manner asthe control member i85ismoved around the" time ,scale .lfil, the potential "E2 being-constant atva relatively; high voltage in the initial-time range, progressively decreasing in the: midrange and again'rernaining constant in thefinal range. It will .be noted that the described arrangement causes E1 to equal E2 in the midrangarbothvalues increasing or decreasing asynchronously with movement, of the control member gl 85.

The manner in which such a "charging :device :isemployed may be readily understood. The :op- .erator merely adjusts the-operating member I85 for whatever period oftime'delayindetonation is :desired, the operator being guided by referenceto the time scale 19!.

.Instead of employing a--m-idrange; between the two extreme ranges of time as described. above, We may in some practices of our invention omit the mi-drangesand provide; ion:directmorrelatio n 13 by arranging for the values E2 and E1 at the end of the initial range to equal the values of E2 and E1 at the beginning of the final range. The relationship may be understood by referring to Fig. 19. Note that E1 progressively rises towards the relatively high value of E2 over the initial range and that in the final time range E1 is substantially constant while E2 progressively decreases in value.

In Fig. we indicate diagrammatically how a rheostat arrangement may be incorporated in a charging device to supply potentials E1 and E2 over two time ranges correlated in the manner suggested by Fig. 19.

A control member 205 shown in dotted lines carries a first brush or. wiper 206 that. is connected to a charging contact E1 by a wire 201. The control member also carries a second brush or wiper 203 that is connected by a wire 210 to a charging contact E2. For cooperation with the contact 206 we show a rheostat means comprising a resistance 2| l and an elongated contact 2 I2 in series, the outer end of the resistance 2| I being connected to a low voltage lead 2l3 and the elongated contact being connected to a high voltage lead 2I5. For cooperation with the contact 208 we show a second rheostat means com-, prising an elongated contact 2 I 6 and a resistance 2i! in series, the elongated contact 2H6 being connected to the high voltage lead 215 and the outer end of the resistance 2|! being connected to the low voltage lead 2l3. It may be readily understood that movement of the control member 205 to adjust charges E1 and E2 for various time intervals will cause the voltages E1 and E2 to vary in value in accord with Fig. 19.

The specific embodiments of our invention set forth above for the purpose of disclosure will suggest to those skilled in the art various changes and substitutes under our basic concepts; we reserve the right to all such departures that lie within the scope of our appended claims.

We claim:

1. In an electric ignition device for delayed detonation of an explosive projectile after the projectile is released from a holding means, the combination of: condenser means in the projectile to hold an electric charge, an igniter in the projectile; charging means for electrical communication with said condenser means while said projectile remains on said holding means; means to apply the charge of the condenser means to said igniter with time delay after the projectile is released from said holding means; a normally closed safety shunt across said igniter to prevent flow of electric current therethrough; an electric conductor included in said shunt, said conductor being attached to said projectile; and means on the holding means engaging said conductor to sever the conductor and thereby open the shunt when said projectile moves away from said holding means.

2. In a delayed ignition device for a unit, which unit comprises an explosive projectile, holding means therefor, and a propelling charge, the combination of: a condenser circuit in the projectile; charging means for contact with said unit to establish a given potential distribution in said circuit prior to explosion of said propelling charge; means to progressively change the potential distribution in said condenser circuit over a period of time after the projectile is propelled from said holding means; an igniter responsive to the potential in said system at a predetermined point in said progressive change in distribution; and a shunt including a Wire across said igniter to prevent energization thereof, at least a portion of said wire being positioned outside of said projectile and int he area occupied by 'said propelling charge whereby the explosion of said propelling charge will destroy at least a portion of said wire and open said shunt.

3. In an electric ignition device for delayed detonation of an explosive projectile after the projectile is released from a holding means, the combination of condenser means in the projectile to hold an electric charge, an igniter in the projectile; charging means for electrical communication with said condenser means while said projectile remains on said holding means; means to apply the charge of the condenser means to said igniter with time delay after the projectile is released from said holding means; a normally closed safety shunt across said igniter to prevent flow of electric current therethrough; an electric conductor included in said shunt, said conductor being attached to said projectile and extending into the holdling means; and means associated with the holding means and including an explosive charge in the holding means for severing said conductor whenever the projectile is fired from the holding means by exploding said explosive charge.

JEROME J. KURLAND. JOSEPH J. KURLAND.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,623,475 Hammond Apr. 5, 1927 1,791,606 Ruhlemann Feb. 10, 1931 1,795,972 Ruhlemann Mar. 10, 1931 1,807,708 Ruhlemann June 2, 1931 1,907,279 Blomberg May 2, 1933 1,917,813 Ruhlemann July 11, 1933 1,917,814 Ruhlemann July 11, 1933 FOREIGN PATENTS Number Country Date 530,348 Germany July 28, 1931 581,491 Germany July 28, 1933 582,582 Germany 1933 91,592 Sweden Feb. 24, 1938 864.373 France 1941

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