US2603970A - Apparatus for testing projectile fuse safety devices - Google Patents

Description

July 22, 1952 s. J. METZLER EI'AL APPARATUS FOR TESTING PROJECTILE FUSE SAFETY DEVICES 2 SHEETS-SHEET 1 Filed April 11, 1949 FIG.!

FIG.4

INVENTORS. SILAS J. METZLER BY -Fi'OBEFnT H. THAYER ,m, 69%

July 22, 1952 s. J. METZLER ETAL 2,603,970

APPARATUS FOR TESTING PROJECTILE FUSE SAFETY DEVICES Filed April 11, 1949 2 SHEETS-SHEET 2 'II wmmwmgw F I G. 8

INVENTORS. SILAS J. METZLER 89 ROBERT H. THAYER j 19am Patented July 22, 1952 APPARATUS FOR TESTING PROJECTILE FUSE SAFETY DEVICES Silas J. Metzler and Robert H. Thayer, Belmont,

Mass., assignors to the United States of America as represented by the Secretary of the Navy Application April 11, 1949, Serial No. 86,656

Claims.

The present invention relates to an apparatus for testing safety devices as employed in conjunction with fuzes and associated controlling means for projectiles.

More specifically the invention relates to the testing of inertia operated safety devices, such as described in the pending application of Philip S. Williams, Serial Number 534,785, filed May 9, 1944, for a Safety Device, wherein said safety devices are designed to interrupt the ignitionconveying train between an explosive squib and the booster charge in an auxiliary detonator, thereby serving as a safety means for preventing premature explosion of a projectile carrying said auxiliary detonator While in, or still close to, the barrel of a gun.

The above-mentioned safety device is controlled by the rotational and linear positive accelerations of the projectile when fired from a gun, which accelerations continue from the time the propelling charge is fired until the projectile has traveled slightly beyond the muzzle of the gun to a point where the propelling efiect of the blast is lost. The safety device is designed to keep the ignition train of the fuze in an interrupted state, or in its safe or unarmed condition during this period. However, an improperly assembled safety device might operate imperfectly and thus be unsafe, or allow the fuze to become armed prematurely.

Heretofore it has been customary to detect faulty assemblies by testing samples of each production lot by actual firing of a complete fuze. The procedure has been to fire the fuze through a target set up within the intended safe distance in front of the gun muzzle, that is, the distance within which it is designed to remain unarmed. If the fuze detonates within this distance, it is an indication that the safety device within the auxiliary detonator has failed and, therefore, was defective.

This method of testing has been used successfully, but it is slow since it requires the installation of a new target for each shot fired. Accordingly, the present process and apparatus have been developed to permit more rapid testing and to eliminate the need for using the complete fuze in performing said tests.

A further object of the present invention is to provide means for testing the complete operation of the safety device of an auxiliary detonator.

An incidental object of the present invention is to provide means for arming fuzes after the projectiles have been fired from the gun.

Other objects and many of the attendantadvantages of this invention will be readily appreciated as the same becomes understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: Y

Fig. l is an axial sectionof a test projectile according to the inventiomthe incorporated electrical circuit being shown diagrammatically;

Fig. 2 is an axial section of the fixed portion of the test equipment, showing the energizing coil mounted on and in front of the gun barrel,.a portion 'of said barrel'being broken away to show the test projectile'therein;

Fig. 3 is a front view of the device illustrated in Fig. 2, with the energizing coil and its protective fairing partially broken away;

Fig. 4 is an elevation, partially in longitudinal section, of an alternate form of energizer, namely. a tubular permanent magnet;

Fig. 5 is a diagrammatic view, similar to Fig. 1, but illustrating a modified embodiment of the test projectile capable of testing the safety device of an auxiliary detonator in both armed and unarmed conditions;

Figs. 6 and 7 are circuit diagrams illustrating means for utilizing the invention for arming the electrical circuits of projectile fuzes, and r Fig. 8 is a sectional viewof a safety gate employed in projectile fuzes', the energizing circuit used for arming said safety gate being shown diagrammatically.

Referring first to Fig. 1, a test projectile I0 is shown with the safety device II which is to be tested secured in an axialbore in the mounting block l2 at the forward end of a shell body 13, said body being provided with a colored smoke charge 14 in its rear end portion and with smoke exhausting orifices, 15. A nonconducting, nonmagnetic nose portion |6 is screwed on the shell body i3 at H, and contains an iron-cored pick-up coil [8 which is electrically connected by conductors .l9 and 20 to an electric detonator 2|, said detonator being secured within an axial bore. 22- in the mounting block l2 adjacent to, and cooperating with, the safety device I l.

Th-e'pick-u'p coil l8 and the detonator 2| are made inoperative during handling by a set-back switch 23 and a centrifugally actuated spinswitch 24, each being of such construction that it will operate by the forces of acceleration due to the firing of the projectile through a gun barrel. Both of said switches 23 and 24 are normally closed, and are shunted across the conductors I9 and 20 by the conductors 25 and26 respectively. A delayed action igniter 21 is imbedded in the rear end of the smoke charge l4 and extends through the rear wall 28 of the shell body l3.

The solenoid 3|] is positioned by saidbrackets to aline it coaxially with the gun muzzle 34 and is separated from it by a distance less than that throughout which the safety device I I is supposed to remain safe or unarmed. The cylindricallyshaped fairing 33 is preferably fabricated from a nonmagnetic material of such toughness as to 4 a voltage in the pick-up coil I8 in the test projectile.

The above-described apparatus provides a test for the safety device II in its unarmed condition. To test the device in its armed condition, modified equipment is required and this is shown in Fig. 5. .In.this.apparatus, the mounting block I2 of the embodiment of Fig. 1 is replaced by a holder 42 with an axial chamber 43 in its rear and to house the safety device I I, said holder being pierced by a'diagonal bore 44 directed toward, and inter- I secting, the chamber 43 at its center. A lon tudinal bore 45 having a rearwardly constricted make it capable of withstanding the forces pro-. v

while still subject to the positive acceleration of the muzzle blast, passes through the saidsolenoid. As the test projectile passes through the field of the solenoid 30, a voltage is induced'in the'pickup coil I8 in the nose of the projectile Illand is applied, through the conductors I9 and 20, to the electric detonator 2| to fire the same. The safety switches 23 and 24 in the shunt conductors 25 and 26 are opened. simultaneously with the firing of the projectile by the set-back and centrifugal force respectively, of the said projectile.

If the safety device II under test is'in proper mechanical condition when the detonator 2| is fired, said device will be in an unarmed condition; that is, with its ignition train misalinedso that the blast from the detonator 2| will not be transmitted to the smoke charge I4- If, on theother hand, the safety device is mechanically imperfect, the explosive train through it may not be sufliciently misalined and on firing the detonator 2| the flame then will carry through to the smoke charge I4, igniting the same, with the resulting smoke signal discharge escaping through the ori-' fices I5 in the shell body I3. The cloud thus formed by this discharge is distinguishable fromthat of the muzzle blast by its color.

The delayed-action igniter 21, the operation-o which is initiated by the fiame'from the propelling charge of the gun, is provided to cause burning of the smoke charge I4 at a considerable distance from the gun muzzle, this burning being an indication that said charge was ignitable and'that either the safety device I I had remained unarmed, as intended, or the electric detonatorv 2| 1 had not fired. I

Referring now to Fig.1 4, illustrating an alternative embodiment of' the. solenoid described above and shown in Fig. 2, a permanent magnet 4|] having the same generally cylindrical shape as the faired'solenoid 30 here replaces said solenoid-in advance of the muzzle of the gun and is positioned in place and secured-in any suitable way, as by welding, by the brackets 4|. This magnet acts" in; the same'manner asjthe solenoid 30 to induce portion 46 intersects said diagonal bore 44 near ';its .point of entry into the chamber 43. The forward, or nose, portion of the projectile accommodates the pick-up coil I8, electrically connected by the conductors I9 and 20 to'the electric detonator 2| inserted in the forward end of the longitudinal bore 45 of the mounting holder 42.

p The coil I8 and the detonator 2 I are made inoperative during handling by the set-back switch 23' and the spin switch 24 each operating similarly to those provided in Fig. 1.. Both of said switches are shunted across the conductors I9 and 20 by the conductors 25' and 26' respectively. This nose portion also contains a battery 4'! connected in series with an inertia-operated, normally open, delayed-action switch 48 by the leads 4:9.and 50 of an electric detonator 5|, said detonator .being inserted in the forward end of' the diagonal bore 44, As in the embodiment of Fig. 1, a smoke charge I4 is placed in the shellbody I3, rearwardly of the holder 42 and cooperating'with the chamber 43, said body being also provided with smoke exhausting orifices I5. The delayed action igniter 21 is imbedded in the rear end of the smoke charge and extends'throug h the rear wall 28. As in the embodiment of Fig. 1, a soft iron cap 29 is also provided here for protection during pro-fire handling. 1, v

In use, the detonator 2| is fired by passageof the shell through the magnetic'fieId at the muzzle of the gun, as previously described, thereby testingthe safety device for properoperation in its safe or unarmed position. L EXpIOSiQD; of the detonator 2| does not affect the detonator 5| since the constriction 46 in the bore 45 directs the effect of the blast against the safety device I I, the enlarged bore 44, because of its comparatively increased cross-section, nullifyin the effector the back pressure resulting from said explosion.

Set-back, upon firing of the projectile from the gun, initiates operation of the delayed-action switch 48', which then closes the circuit containblast through to the-smoke charge I 4', ignitingthe'same and producing a cloud at a considerable distance from the muzzle of th'egun.

"On the other hand, if the safety device is not operating correctly, namely, is unarmed when the detonator 5| explodes,'the smoke chargewill not be ignited. Of course, if the magnetically initiated detonator 2|" had prematurely fired the smoke charge I4, due to a-fa'ulty safety device,

the ffiringof the sp eens! detonator 5| would have no visible efiject upon the projectile. As was the case in the embodiment of Fig. 1', if the safety device remained unarmed during the exploding of bothdetonators the smoke charge would eventually be ignited by the firing of the delayed action igniter 21.

It may readily be seen that the system above described may also be employed to arm a fuze after its associated projectile hasleft the muzzle of a gun. Figs. 6 and 7 show possible arrangements of such a device, schematically.

Referring to Fig. 6, an electric fuze circuit includes a battery-52 and conductors 53 and 53a therefrom. Conductors 54 and 55 from a pickup coil 56, which would be located in the nose of the projectile, are short-circuited by a set-back 51 and a spin-switch 58 shunted across the conductors 54 and 55 by conductors 58 and E58 respectively. The conductors 54 and 55 are connected, at their ends remote from the pick-up coil 55, to a winding SI of a locking relay 62. This relay includes a movablecontact arm 68 and a fixed contact (it which are introduced into the fuze. circuit conductor 53, tomaintain this circuit, which is not fully shown, normally open.

Operation of the device described, and shown in Fig. 6, is similar to that of the testing device hereinabove described, Passage of the projectile, incorporating said device, through either the solenoid winding 32 of Fig. 2 or the permanent magnet 48 of Fig. 4 induces a voltage in the'pickup coil 56. This voltage is applied to the winding SI of the locking relay 62, causing the contact arm 53 to close with the fixed contact 64- and there become locked, closing the fuze circuit through the battery 52; thus arming the complementary fuze circuit of the projectile.

Safety during handling is provided, as in the embodiments illustrated in Figs. 1 and 5, by the set-back switch 57 and the spin-switch 58 each of which will independently provide a short-circuitin the piok-up coil circuit until after the firing of the projectile. A soft iron cap similar to the cap 29 should be applied over the nose of the projectile as an additional precaution'against premature arming of said projectile.

Another embodiment of a control for an electric fuze having a battery 65 and conductors 66 and 6 7 therefrom is shown in Fig. '7. In this form the conductors 68 and 68 from the pick-up coil 18 are connected to a squib II in a chamber 12 of a mounting block 13. As previously shown and described, a set-back switch 14 and a spin-switch 15 are shunted across the conductors 68 and 69 by the conductors l6 and l! respectively. A metallic plunger 78 is located in the chamber 12 adjacent to the squib Tl. A pair of spaced contacts 18 in line with the chamber 12 and located at the end thereof remote from the squib H, interrupt the conductor 6'! from the battery 65. In use, a current due to the voltage induced in the pick-up coil 18 explodes the squib H to drive the .plunger 18 up the chamber 12 and between the contacts 19 and there locks said plunger to maintain closed the fuze circuit through the battery 65, thereby arming the fuze.

Referring now to Fig. 8 there is shown an embodiment of the, invention to be employed in a projectile having a non-electric type fuze. Here is shown ,a safety gate 88 with its ignition train misalined, or in, an unarmedcondition. Movable gates 8| and am with an explosive pellet 82 dis posed therebetween are located in a chamber 83 between the alined sections 84 and .85 of said ignition train. ,The pellet 82 is normally secured out of alinement with .the sections 84 and 85 by action-50f a conventional detent 86, shown as a spring-pressed ball riding in a circumferential groove in the wall of chamber83. An electric squib 8-1, connected to the conductors 88 and 88 from th pick-up coil 90, is installed in the chamber 83 adjacent to the gate 8|. For safety a setback switch el and a spin-switch 92, with conductors 93 and 94 respectively, areshunted across the conductors 88 and 89, thus providing a short circuit between the squib 81 and the pick-up coil 98. I 1

Explosion of the squib 81, caused by a. current due to the voltage induced in the pick-up coil 90 on passing through the solenoid winding 32 of Fig; 2 or the permanent magnet 48 of Fig. 4 shifts the gate 8| in the chamber 83, overcoming the resistance of the detent 86 to aline the pellet 82 with sections 84 and 85 of the explosive train, for completing the same. The gate is held in this position by a second detent 93 similar to that shown at 86. In this position the ignition train is alined and the projectile is thus armed for detonation.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

We claim:

1. In a system for testing inertia-operated safety devices for projectiles, the combination with a gun for test-firing projectiles containing said safety devices, a source of magnetic flux fixed in proximity to the muzzle of the gun, and a projectile to receive the safety device to be tested, a pick-up coil in the projectile, an electric detonator connectedto said coil, and a smokeproducing charge, said safety device being located between said detonator and said charge; passage of the projectile through the magnetic flux inducing an electromotive force in the pickup coil to explode the detonator during positive acceleration of said projectile, and failure of the safety device permitting transmission of the explosion to and ignition of the smoke-producing charge to indicate said failure.

2.'In a system for testing inertia-operated safety devices for projectiles, the combination with a gun for test-firing projectiles containing said safety devices, a source of magnetic flux fixed in alinement with and ahead of the muzzle of the gun, a projectile to receive the safety device to be tested, a nonmagnetic, nonconducting nose on the projectile, a pick-up coil in said nose, an electric detonator connected to said coil, and a smoke-producing charge, said safety device being located between said detonator and said charge; passageof the projectile through the magnetic flux inducing an electromotive force in the pickup coil to explode the detonator during positive acceleration of said projectile, and failure of the safety device permitting transmission of the explosion to and ignition of the smoke-producing charge to indicate said failure.

3. Ina system for testing inertia-operated safety devices for projectiles, the combination with a gun for test-firing projectiles containing said safety devices, a source of magnetic flux fixed in alinement with and ahead of the muzzle of the gun, a projectile to receive the safety device to be tested, a nonmagnetic, nonconducting nose on the projectile, a pick-up coil in said nose, an electric detonator connected to said coil, an

inertia-operated setback-switch normally shortcircuiting the detonator, an inertia-operated spin switch normally short-circuiting the detonator, and a smoke-producing charge, the safety device to be tested being interposed between the detonator and the smoke-producing charge; passage of the projectile through the magnetic flux inducing an electromotive force in the pick-up coil to explode the -detonator during positive acceleration of said projectile, and failure of the safety device permitting transmission of the explosion to and ignition of the smoke-producing charge to indicate said failure.

4. In "a system for testing inertia-operated safety devices for projectiles,- the combination with a gun for test-firing projectiles containing said safety devices, an electrically energized coil fixediin'alinernent with andahead of the muzzle of the gun asa source of magnetic flux, a projectile to receive the safety device-to be tested, a nonmagnetic, nonconducti-ng noseon the projectile', a pick-up coil in said nose, an electric detonator connected to said coil, an inertia-operated setback switch normally short-circuiting the detonator, an inertia-operated sp-i-n switch normally short-circuiting the detonator, and a smoke-producing charge, said safety device being located between said detonator andsaid charge; passage of the projectile through the magnetic field of the fixed coil inducing an electromotive force in the pick-up coil to explode the detonator during positive acceleration of said projectile, and failure of the safety device permitting transmissionof the explosion to and ignition of the smoke-producing charge to indicate said failure,

5. In a system for testing inertia-operated safety devices for projectiles, the combination with a gun for test-firing projectiles containing said safety devices, an annular permanent magnet nxed in alinment with and ahead of the muzzle of the gun, a projectile to receive the safety device; to be tested, a nonmagnetic,.non conducting nose on the projectile, a' pick-up coil in said nose, an electric detonator connected to said coil, aninertia-op'erated setback switch nor mally short-circuiting' the detonator,- an inertia-- operated spin switch normally,short-circuiting the detonator, and a smoke producin'g charge, the, safety device to be tested being interposed between the detonatorj and; the smoke-producing. charge; passage of the projectile through-the field ,of' the permanent magnet inducing an electromotive force in the'pick-up coil to explode the detonator during positive acceleration ofv said projectile. and failure of the safety device permitting transmission of the explosion to and ignition of the smoke-producing charge to, indi cate said failure;

6'. In1 a system for testing inertia-operated safety devices for projectiles, the combination with a" gun for test-firing projectiles containing said safety devices, a source of magnetic flux 'fixed in'alinement with and ahead of the muzzle: of the gun, and" including. axcoi'l form having, an. inner diameter: greater than the bore: of the gum a coil of wire woundthereon, at fairedcylindrical: blast-proof housingforthe coil form and. coil, brackets for mounting the housing and coil on the muzzle of the gun, and a source of D. C. power for energizing the-coil.

'7. In asystem for testing.- inertia operated' safety" devices for projectiles; the combination with. a for test-firing. projectilesacontaining said: safety devices, :a source of magnetic flux 8 of the gun, said source consisting of a cylinder of magnetically retentive material with an inner diameter greater than the bore of the gun and having faired ends to reduce the force of muzzle blast; said cylinder being longitudinally magnetized.

8. In a system for testing inertia-operated safety devices forprojectiles, the combination with a g-u'n'for test-firing projectiles containing said safety devices, a source of magnetic flux fixed in alinement-with and ahead of the muzzle of the gun, a projectile to receive the safety device to be tested, a nonmagnetic, nonconduct ing nose on the projectile, a pick-up coil in said nose, at first electricdetonator connected to said coil, an inertia-operated setback switch normally short-circuiting said first detonator, an inertiaoperated spin switch also normally short-circuiting said detonator, a second electric detonator, a battery, a slow-closing, normally open, inertia-operated" switch, said battery being connected' to said second detonator through said switch, and asmoke-producing charge, the safety device to be tested being interposed between the smoke-producing charge and the first and second detonators; passage of the projectile through the annular source of magnetic flux inducing an electromotive force in the pick-up coil to explode the first detonator during positiveacceleration of said projectile, and failure of the safety device permitting transmission of the explosion to and ignition of the smoke-producing charge as indication of said failure, and proper operation of the safety device preventing such transmission and ignition upon explosion of said first detonator and permitting same upon later explosion of the second detonator, proper or improper performance of the safety device being indicated by the position along the trajectory of the shell of the" smoke puff produced by ignition of the charge.

9. Ina system for testing inertia-operated safety devices for projectiles, the combination with: a gun for test-firing projectiles containing said safety devices, a source of magnetic flux fixed in alignment with and ahead of the muzzle of. the gun and Within the area of positive acceleration of a projectile fired from the gun, anda test projectile including a projectile body, a charge of smoke producing material in a portion of said body, a plurality of sequentially act-- ing. detonators in said projectile, a partition between said charge and said detonators, said partition having a passage through which detona tion of said detonator is transmitted to said charge, an inertia-operated safety device secured in saidpassag'e and operative to close said passage durin'gintervals of positive acceleration of said projectile and to open the passage after cessation of positive acceleration, a pick-up coil carried by said projectile, connections from saidcoil'. to one of said detonators, a plurality of safety switches normally closed to short circuit said coil and prevent detonation of said detona-' tors by accidental ener'gization of said coil, one of said safety switches being actuated to open position by po'stive acceleration of the projectile in a; forward direction, anotller of saidsafety switches being. actuated to open position-by rota-- tion of' said; projectile about its axis, a source of electric", energy in said; projectile, connections including a normally-open inertia-operated delayed operation switch responsive to positive acceleratiorr to" connect said source to the second fixed alinement wi-th andxahead o'fi the muzzle of said. detonators" after cessation of positive 9 r acceleration, and altime' delay detonator actuated by the application of the propelling flash to said projectiles passage for ,th projectile through theIjmagneticflux inducing an electromotive force in 'theilpickup coil to explode the first detonator during positive acceleration of the projectile, failurenf; the safety device permitting transmission of the detonation to, the charge,

and proper operation of said safety device preventing such transmission upon detonation of said first detonator and 'perrnitting transmission upon later detonation of the second detonator, proper or improper performance of the safety device being indicated by the position along the trajectory of the projectile of the signal produced by ignition of the charge. i c

10. A testing system for inertia-operated safety devices for projectiles, comprising a test projectile, a charge of smoke producing material in said projectile, a plurality of detonator devices in said projectile, a partition between said charge and said detonators, said partition having a passage through which detonation of said detonators is transmitted to said charge, an inertiaoperated safety device located in said passage and operative to close said passage during intervals of positive acceleration of said projectile and to open the passage after cessation of positive acceleration, a gun for propelling said projectile, a source of magnetic flux fixed adjacent the muzzle of said gun and within the area of positive acceleration of the projectile, a coil carried by said projectile, said coil traversing said magnetic flux to generate a potential in said coil to detonate the first of said detonator devices during positive acceleration of said projectile whereby failure of said safety device transmits the detonation to said charge, a second source of electric energy in said projectile, and an inertia-operated normally open delayed-action switch connecting said second source to detonate the second of said detonators after cessation of positive acceleraton of said projectile whereby normal operation of said safety device transmits said detonation to said charge.

11. A testing system for inertia-operated safety devices for projectiles, comprising a test projectile, a charge of smoke producing material in said projectile, a detonator device in said projectile, a passage between said detonator and said charge, a safety device for test being secured in said passage and operative, during positive acceleraton of said projectile in a forward direction, to close said passage, a gun for propelling said projectlle, a source of magnetic flux fixed adjacent the muzzle of said gun and within the area of positive acceleration of the projectile, a coil carried by said projectile, said coil traversing said magnetic flux to generate a potential in said coil to detonate said detonator device during positive acceleration of said projectile whereby failure of said safety device transmits the detonation to said charge.

12. A testing system for inertia-operated safety devices for projectiles, comprising a test projectile, a charge of smoke producing material in said projectile, a plurality of detonator, devices in said projectile, a channel conducting said detonation to said charge for igniting the same, a safety device for test located in said channel and operative to close said channel during positive acceleration of said projectile and to open said passage after cessation of positive acceleration, a gun for propelling said projectile, a source of magnetic flux fixed adjacent the muzzle of c l0 v said gun} and within the area of positiveac'celeration of the projectile, a coil carried by said projectile, said coil traversing said magnetic flux to 'generateapotential in said coil to detonate thev first of said detonator devices during positive acceleration whereby failure of said safety device: transmits the detonation of said first detonatorto said'charge, asecond source of'electric energy insaid projectile and aninertia-operated normally open delayed action switch: connecting said second-source to detonate the second of said detonators after cessation of positive acceleration of said projectile whereby normal operationo'f said safety device transmits said detonationto said charge, and a delayed action detonator testing said charge upon'failure of said f rst or second detonators to detonate said charge.

13; A testprojectile for testing an inertia-operated safety device, comprising a projectile body, a charge of smoke producing material in a portion of said body, a test detonator in said projectile, a partition between said charge and said detonator, said partition having a passage through which detonation of said detonator is transmitted to ignite said charge, an inertia-operated safety device in said passage and operative to close said passage during intervals of positive acceleration of said projectile and to open the passage after cessation of positive acceleration, a pick-up coil carried by said projectile, connections from said coil to said detonator, a plurality of safety switches normally closed to short circuit said coil and prevent detonation of said detonator by ac cidental energization of said coil, one of said safety switches being actuated to open position by positive acceleration of the projectile in a forward direction, another of said safety switches being actuated to open position by rotation of said projectile about its axis.

14. A test projectile for testing an inertiaoperated safety device, comprising a projectile body, a charge of smoke producing material in a portion of said body, a plurality of detonators in said projectile, a partition between said charge and said detonators, said partition having a passage through which detonation of said detonators is transmitted to said charge, an inertiaoperated safety device in said passage and operative to close said passage during intervals of positive acceleration of said projectile and to open the passage after cessation of positive acceleration, a pick-up coil carried by said projectile, connections from said coil to one of said detonators, a plurality of safety switches normally closed to short circuit said coil and prevent detonation of said detonator by accidental energization of said coil, one of said safety switches being actuated to open position by positive acceleration of the projectile in a forward direction, another of said safety switches being actuated to open position by rotation of said projectile about its axis, a source of electric energy in said projectile, connections including a normally open inertia-operated delayed-action switch responsive to positive acceleration to connect said source to another of said detonators after cessation of positive acceleration.

15. A test projectile for testing an inertia-operated safety device comprising a projectile body, a charge of smoke producing material in a portion of said body, a plurality of sequentially acting detonators in said projectile, a partition between said charge and said detonator, said partition having a passage through which detonation of said detonator is transmitted to said 11 charge, an inertia-operated safety device secured in. said :passa'g'e and operative to "close said passage duringintervals .of positive acceleration "of said; projectile and" to open thepassage after icessation of .positive acceleration; a pick-up cougar.- r'ied by said projectile;connecti'onsfrom.said coil to one of said .detonators,a pluraiityof safety Y switches normally closed to short -circuit said coil and prevent detonation of said detonators by accidental en'ergization vof said .coil, one of said safety switchesbeing'actuated to open position by positive acceleration *ofthe projectile in a forward direction, another of said safetytswitchesbeing actuated to open position by. rotation of said projectiierabout its'axis,.a source oi electric energy saidhpro jectile, connections including a normallyopen:inertia-operated'delayed operation switchresponsiveto positive acceleration to con- 12 nect saiclsonr-ce to the second of said detonators after, cessation of positive acceleration, and a time delay detonator a'ctuated by the application of then-propelling flash toisaid projectile.

' SILAS J. ME'IZLER.

ROBERTH. THAYER.

REFERENCES CITED Theiollowing references are of record in the file Df-this patent:

UNITED STATES PATENTS Golden July 5, 1949

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