US2733659A

US2733659A - booth

Info

Publication number: US2733659A
Authority: US
Publication date: 1956-02-07
Anticipated expiration: 1973-02-07

Description

Feb. 7', 1956 s. w. BOOTH 2,733,659

DELAYED ARMING FUZE FOR A PROJECTILE Filed Aug. 5, 1949 meets-Sheet l FIG.1.

, 59 PEG. 8.

' 57 I I4 64 F IG. 9

RATE OF SPIN 0F BALLS ABOUT I 79 THE AXIS OF THE FUZE.

Feb. 7. 1956 s. w. BOOTH 2,733,659

DELAYED ARMING FUZE FOR A PROJECTILE Filed Aug. 5, 1949 2 Sheets-Sheet 2 F 6 F. M.

66 w 67 as 14 {35 Elma/MM 4.1 m s SETH w. 00TH $5 United States Patent DELAYED G FUZE FOR A PROJECTILE Seth W. Booth, University Park, Md. Application August 5, 1949, Serial No. 108,833 12 Claims. (Cl. 102-79) (Granted under Title 35, U. S. Code (1952), see. 266) This invention relates to a fuze for a projectile, or the like, adapted to be fired from a gun and exploded upon impact with a target or in the vicinity of a target, in which new and improved means are employed for preventing the premature arming of the explosive or bursting charge until the shell has traveled a safe distance beyond the muzzle of the gun. More specifically, the invention relates to a new and improved means for maintaining the fuze in a safe condition until the speed of rotation of a plurality of inertial devices has approached the speed of rotation of the projectile.

In accordance with the present invention a plurality of balls are arranged between a pair of conical surfaces formed on a movable and stationary member respectively and disposed within the fuze of a projectile whereby the speed of rotation of the balls as the projectile is fired from a gun is gradually increased until the force of acceleration of the projectile has diminished to a value corresponding to the force of acceleration acting on the projectile at a safe distance from the gun after the projectile has been fired therefrom until a predetermined speed of rotative movement of the balls is obtained. 7

When this occurs the fuze is armed.

This invention provides new and improved means for preventing the premature explosion of the shell or projectile in or within the vicinity of the gun as the gun is fired.

One of the objects of the present invention is the provision of a new and improved means for preventing the premature firing of an explosive charge arranged within a projectile during'the transportation, handling, loading, and firing of the projectile from a gun.

Another of the objects is the provision of a new and improved means for maintaining a fuze in a safe condition as the projectile is fired from a gun until the speed of rotation of a plurality of inertial balls arranged be tween a pair of conical members having the axes thereof in coincidence with theaxis of the projectile has reached apredetermined value.

Still another object is the provision of a fuze for a projectile having new and improved mechanical means for delaying the arming of the fuze as the projectile travels along a trajectory and to render the electrical firing mechanism effective when the centrifugal force produced by the spin of a plurality of balls has caused'movement of the arming mechanism of the projectile.

A further object is to provide a new and improvedfuze for an explosive projectile having means arranged therein for preventing arming and firing thereof until the projectile is clear of the gun which is economical to manufacture, reliable in operation, and which possesses the qualities of durability and safety during handling and transportation.

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

ice

Fig. 1 is a sectional view of the fuze of the present invention and a portion of a projectile or the like employed therewith, the fuze being in an unarmed condition;

Fig. 2 is a sectional view similar to Fig. 1 and showing the fuze in an armed condition;

Fig. 3 is a sectional view taken on the line 3-3 of Fig. 1;

Fig. 4 is an enlarged fragmentary view of the delayed arming device with the inertial elements thereof in an initial position;

Fig. 5 is a view similar to Fig. 4 and showing the position of the inertial element during movement of the armin g member toward an armed position;

Fig. 6 is a diagrammatic view of the firing circuit therefor; v

Fig. 7 is a graph illustrating in diagrammatic form the delay in the arming of the fuze after the projectile has been fired from a gun;

Fig. 8 is a fragmentary view of the device according to an alternative form thereof; and

Fig. 9 is a diagrammatic view of a firing system suitable for use with the device of Fig. 8.

Referring now to the drawings for a more complete understanding of the invention and more particularly to Fig. 1 thereof, there is shown thereon a fragmentary portion of a shell or projectile indicated by the reference character 10 and comprising a casing 11 having the usual explosive or bursting charge 12 disposed therein, as is Well known to those skilled in the art.

The fuze generally indicated by the reference character 13, comprises a nose portion 14 secured to the shell casing 11 in any suitable manner, preferably by an external screw threaded nipple 18 having threaded engagement with the shell casing 11. The nipple 18 is provided with an enlarged well 19 having a booster charge 24 arranged therein and composed of any explosive suitable for the purpose such, for example, as the type known in the trade as Tetyrl.

A reduced bore 25 is arranged within the nose 14 in communication with a well 19 and a lead-in explosive charge indicated by the reference character 26 is disposed therein,in engagement with the booster charge 24 to provide means for firing the booster charge when the fuze is functioned upon impact thereof with a target. The booster charge is sealed within the recess by a disc 27 composed of any material suitable for the purpose such, for example, as blotting paper or the like and a steel disc 31, the disc being clamped in position by a flange 32 formed on the magazine and crimped or rolled into clamping engagement with the disc.

A delayed arming device generally indicated by the reference character 33 is arranged within a recess 34 formed in the nose 14 with the axis thereof incoincidence with the spin axis of the projectile or missile. The arming device comprises a stationary member 35 and a movable member 36, the

members

35 and 36 having respectively formed thereon a pair of centrally disposed

parallel surfaces

37 and 38 and a pair of outwardly and downwardly

inclined surfaces

39 and 41. Disposed between the

members

35 and 36 and in engagement with the surfaces 37-38 when the projectile is in an unarmed condition are a plurality of balls 42, the balls being adapted to be moved radially by centrifugal force into engagement with the

inclined surfaces

39 and 41 thereby to move the member 36 longitudinally sufficiently to arm the fuze during the flight of the projectile toward a target.

As shown on Figs. 1 and 2 the member 36 has formed thereon a boss or extension 43, having secured thereto and movable therewith a substantially L-shaped bracket or support generally indicated by the reference numeral 44 and comprising a short leg 45 and a long leg 46, the long leg being secured to the boss 43 in any suitable manner such, for example, as by screws or the like.

The nose 14 has formed therein a recess or guide-way 47 having a plunger 48 releasably and slideably arranged therein. The plunger is normally locked and urged to an armed position, Fig. 2, by a spring 49 when the plunger has been released, whereupon a sensitive detonator 51 is brought into registration with the lead-in charge. 26. It will be understood, however, that the plunger is locked in a safe or unarmed condition, Fig. l, by the usual centrifugally actuated detents (not shown), the detents being adapted to be moved to a. release position in response to centrifugal force whereupon the plunger 48 is moved to an armed position by spring 49.

As shown on Figs. 1 and 2 nose 14. is provided with a bore or passageway 52 comprising a vertical portion 53 and an inclined portion 54. The vertical portion is in. communication with the recess 47 and has disposed therein a sensative detonator 55 in approximate spaced relation with respect to the plunger 43. and adapted to fire. the detonator 51 when the plunger is, in an armed position upon impact of the shell with a target. The inclined portion is in communication with a centrally disposed bore 56 and has disposed therein a flash primer 57 adapted to be fired by a firing pin 58 releaseably supported Within the bore 56 by a shear pin 59 as the pin is severed upon impact of the shell with a target.

Disposed within the inclined portion 54 of the bore 52 is a detent 61, the detent being normally urged into a safe position by a spring 62, Fig. 2, thereby to prevent, communication between the bore 56 and the inclined portion 54 until the detent has been actuated to an armed position in response to centrifugal force. When this occurs the detent 61 will be moved from the safe position sufficiently to permit communication between the aforesaid bores and thus permitting a flash from primer 57 when fired by the firing pin 58 to contact and fire the detonator 55.

As shown more clearly on Figs. 1 and 2 the member 36 is held against rotative movement by a plurality of rods 50 secured thereto in any suitable manner such, for example, as by having one end of each rod in threaded engagement with member 36, the other ends thereof being respectively disposed and slideably arranged within a plurality ofrecesses formed in the nose 14. By this arrangement the member 36' is moved longitudinally as the balls 42 are moved outwardly thereby assuring arming of the fuze. A spring 60 is arranged about each rod 50 having one end in engagement with the. member 26, the other end thereof being in engagement with the nose 14 and thus. restraining the member 36 until the force applied to the arming member by the. ballsv exceeds the force applied thereto by the springs.

The detent 61 is provided with an annular locking groove 63 having disposed therein one end of a pawl or latch generally indicated by the reference character 64, the other end thereof being rotatably supported on a, pivot pin 65. The; latch member 64 maintains the detent 61 locked in a safe, position until actuated to a released position by the movable member 36 as the member is moved longitudinally to an armed'position during the flight of the projectile. Furthermore, the movable member 36 is main tained immovable and locked until the pawl 64 is moved out of. engagement with. the leg 45 formed on the L-shaped member 44, Fig. 2. It will be understood, however, that as. the spin. of the projectile increases, rotative movement of the balls 42 disposed between the.

members

35 and 36 is gradually accelerated and thereby the balls develop sufficient centrifugal force to cause movement thereof outwardly into forcible engagement with the inclined surfaces 39- 41, whereupon the movable member 36 is moved longitudinally within the. fuze in. response. to the radial movement.v of the balls. When this occurs. the leg 45 moves. the latch, member 64 out. of engagement with the groove. 63 formed in detent 61. and thus the. detent is unlocked. for movement to, the aforesaid. armed position Within the bore 54. The member 36 is also adapted to disengage the pawl 64 from the leg 45 upon movement thereof.

The operation of the inertial balls 42 in arming the fuze will best be understood by reference to Figs. 4 and 5, on which is shown the balls in their initial position and before being moved outwardly into engagement with the annular cam surfaces 39 and 41 of the

members

35 and 36 and the position of the balls during movement of the arming member 36 toward the armed position thereof respectively. When the balls are in position as shown on Fig. 4 prior to movement of the arming member 36, the balls are in contact with the

surfaces

38 and 39 at two diametrically disposed points thereof by reason of the action of the springs 60. The balls at this time are not rotating at the same speed of rotation as the fuze by reason of the engagement of the balls between the

polished surfaces

37 and 38 of the

members

35 and 36 and the smooth polished surfaces of the balls with which they are engaged. It will be understood, therefore, that during the initial travel of the fuze the balls are continually slipping between the

surfaces

37 and 38 until the speed of rotation of the balls about the axis of the fuze has obtained sufficient proportion to cause movement of the member 36 from the initial unarmed position thereof.

When this occurs the balls 42 are no longer engaged by the

flat surfaces

37 and 33 but are in rolling contact with the smooth annular

inclined surfaces

39 and 41 at the points A and B, Fig. 5. The points of application of force to the balls 42 are thus transferred from the pair of diametrically disposed points of contact of the balls with the

surfaces

37 and 38 to a pair of points A and B displaced at a distance D from the axis of the balls whereby a moment is applied to each of the balls, causing the balls to spin about their axes as they roll along circular tracks on the.

inclined surfaces

39 and 41. The additional force required to impart rotative movement to the balls about, their axes causes the balls to accelerate more slowly in their rotative movement about the axis of the projectile than would otherwise be the case and thus an additional delay is obtained in moving the armed member 36 to the armed position. This condition is clearly made manifest on Fig. 7' of the drawings in which the initial spin of the balls about their axes is indicated at point 70 of the curve 77.

From the foregoing it will be, clearly apparent that the delay in arming the. fuze is achieved by a plurality of spherical inertial members frictionally engaged between complementary cam surfacesv in which the coefiicient of friction between the: spherical. surfaces and members is sufliciently small to. cause a considerable degree of slippage between the inertial members and the complementary surfaces. Movement of an arming member in response to the centrifugal force of these inertial spheres is, thus; delayed. until the spin missile has traveled a safe distance from the point of launching thereof. An additional and important feature of this delay feature resides in the spin. of the balls. about their axes upon fractional engagement of the balls withv the annular inclined cam surfaces which causes the. rate of acceleration of the balls in their rotative movement about the axis of the spin projectile to be retarded in proportion to the spin transmitted to the balls through their points of contact with the inclined surfaces aforesaid.

When the fuze has been armed, the detonator 51 is aligned with the lead-in charge 26 and also. brought in alignment with the primer 55, the detent 61 having been moved. outwardly sufficiently to permit an uninterrupted passageway between primer 5755. Upon impact of the shell with a target, the firing pin 58 is driven into firing engagement with the primer 57 with sufiicient force to cause firing thereof, the. flash therefrom being directed by way of. bores. 56,. 53', and 54 into firing engagement with primet 55; and thus initiating firing of the. detonator 51', leadin charge 26, and booster charge 24' in successive order.

The arming of the fuze is delayed by the specific construction and arrangement of the delayed arming mechanism 33, particularly the ball and cam arrangement thereof, for the reason when the projectile or missile is fired or launched, as the case may be, and rotates about its axis the balls 42 gradually accelerate rotatively. This acceleration develops suflicient centrifugal force to cause the balls to move outwardly into engagement with the

inclined surfaces

39 and 41, such outward movement of the balls along the inclined surfaces causing the movable member 36 to be moved longitudinally with respect to the stationary member 35 in predetermined time delayed relation with respect to the initial rotation of the missile as the missile is fired.

It will be understood, however, that when the member 36 has been moved longitudinally as heretofore described means may be employed therewith, if desired, for arming the fuze electrically.

As shown on Figs. 1 and 2 means are employed to arm the fuze by movement of the member 36 and to fire the fuze electrically, the means comprising a pair of normally closed contacts 66--67 and a pair of normally open contacts 6869, the

contacts

66 and 69 being electrically connected together and secured to the movable member 36. When the fuze is in an armed condition, a firing circuit is established from the firing mechanism 71, Fig. 6, of any well known type suitable for the purpose to the electroresponsive detonator 72 by way of conductor 73,

contacts

68 and 69, and conductor 74 to one terminal of the detonator 72, the other terminal of the detonator being connected to the firing mechanism by conductor 75. The fuze is maintained in a safe condition during handling and transportation by the detent 61 and latch 64 and also by the foregoing circuit arrangement whereby the electroresponsive detonator 72 is normally short circuited by contacts 6667 as clearly shown on Fig. 6.

The firing mechanism 71 may be of any type suitable for the purpose, such for example, as a radio controlled firing mechanism or the voltage generating device disclosed and claimed in the co-pending application of Harold J. 'Plumley, for a Magnetic Inertial Controlled Fuze, Serial No. 535,799 filed May 16, 1944.

By the foregoing arrangement it will be understood that a firing circuit will not be established from the firing mechanism to the electroresponsive detonator until the movable member 36 has been moved to an armed position in the aforesaid manner, thereby moving the member 36 sufiiciently to engage contacts 6869 and to disengage contacts 6667. It will be understood, however, that movement of the detent 61, Fig. 1, will not occur until the member 36 has moved a sufficient distance to disengage the latch member 64 therefrom and thus complete arming of the fuze will not occur until the shell has cleared the muzzle of the gun and traveled a predetermined distance therebeyond sufiicient to cause the balls within the

members

35 and 36 to spin at a rate at which the member 36 is moved thereby to an armed position.

The lag in the rateof spin of the balls with respect to the spin of the projectile and the delay in arming caused thereby will best be understood by reference to Fig. 7 on which it is shown by the curve 76 the rate of spinof the projectile as the projectile is fired from the gun and travels along a trajectory. The rate of spin of the balls about the axis of the projectile within the

members

35 and 36 is shown by the curve 77. The angular acceleration'of the balls from a state of rest to the rate of spin corre sponding to the spin of the projectile requires a much longer period of time to achieve than the time required for the shell to reach a state of maximum rate of spin by reason of slippage of the balls between the

elements

35 and 36 during the initial portion of the flight of the projectile. The dashed line 78 is employed to indicate the rate of spin of the balls required to generate centrifugal force sufiicient to move the balls outwardly and thus actuate the member 36 to the armed position. The intersection of the dashed line 78 with the curve 77 at point '6 79 occurs at a time T sufiicient for the projectile to be well clear of the gun before the member 36 is extended sufiiciently for contacts 6667 to be disengaged and contacts 6869 to be brought into mutual engagement and thereby close the firing circuit from the firing mechanism to the detonator 72.

From the foregoing it will be apparent that the firing mechanism and the circuit arrangement therefor is particularly well adapted to function the fuze electrically when the projectile strikes the target and the firing pin 58 is adapted to function the fuze mechanically when the projectile strikes the target a head-on blow in which event the fuze is fired by the firing pin.

As shown on Fig. 8 a cup-shaped member 81 is employed on the boss 43 in place of the L-shaped bracket 44 for releasing the latch member 64 as the member 36 is moved longitudinally thereby to arm the fuze as heretoi'ore described. The member 36 in accordance with this form of the invention is restrained by a pair of springs 82, one end of each spring being secured to the nose 14 as at 83, the other end thereof being in engagement with the member 36 as at 84. Secured to the boss 43 is a contact ring 85 normally in engagement with a contact spring 86 and in spaced relation with a contact spring 87, the contact. springs 86-87 being insulated from each other as at 88 and secured to the nose in any suitable manner whereby the contactring 85 is disengaged from contact 86 and brought into engagement with contact 87 as the member 36 moves into the armed position.

The fuze is maintained in a safe condition and premature firing of the detonator 72 will not occur for the reason that the detonator is normally short circuited by contacts 86-85, Fig. 9.

When the fuze is in an armed condition, the short circuit is removed from the detonator and a firing circuit is established from the firing mechanism 71 by way of conductor 89, spring contact 87, ring contact 85 and thence to grounded terminal of detonator 72, the other terminal of the detonator being connected to the firing mechanism by conductor 91.

By employing the arrangement'shown on Figs. 8 and 9 the arming member 36 is adapted to move both longitudinally and rotatively with respect to the shell while the shell is in flight, in contradistinction 'to the arrangement of Fig. 1 in which the arming member 36 is restrained from rotative movement with respect to the shell.

In operation as the shell is fired from a'gun sudden rotative movement is imparted to the member 35 secured integrally thereto and the inertial balls 42 rotate about the axis of spin of the shell with increasing rapidity, the rate of rotative movement of the balls about the spin axis of the projectile lagging the spin of the projectile. The member 36 is caused to spin about the aforesaid axis of rotation of the shell with a gradually increasing rotative speed'by reason of the moment applied thereto by the springs 82, contact spring 86, arm 64 and the friction between the element 36 and the support therefor. By reason of this construction a greater delay in the time required for the inertial balls to attain a rate of spin sufiicient to actuate the member 36 to an armed position may be obtained than with the arrangement of Fig. 1. It will be understood, however, that either of the devices of Fig. l or Fig. 8 may be employed to achieve the desired result.

Whereas the invention in accordance with a preferred embodiment thereof has, been described with particular reference to arming a projectile electrically by actuating electrical contacts as the member 36 is moved longitudinally, it is not so limited as, if desired, the member 36 may be employed to cause motion in a mechanical arming system sufiicient to move the components thereof into armed position as the member 36 is moved by the balls in response to the centrifugal force of the balls as the projectile rotates and the speed of rotation of the balls reaches a predetermined value during the flight of 7 the missile without departing from the spirit or scope of the invention. Furthermore, the member 36 may he provided with a restraining spring or the like for additionally retarding longitudinal movement of the member if desired.

Whereas the invention has been described in detail with respect to a projectile, it will be understood, that it may be advantageously employed, if desired, with a spin rocket or other missile which rotates during travel thereof toward a target.

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 specifically described.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

I. An arming device for a fuze comprising a rotatable casing, an arming member slideably arranged Within the casing, means including a plurality of inertial balls in frictional engagement with said member for actuating the member to an armed position as the speed of rotation of the balls about the axis of rotation of the casing approaches the speed of rotation of the member, and means including a bell-crank lever pivotally mounted on said casing, and operated by said member, for maintaining the fuze in a safe condition until the member is actuated to said armed position.

2. An arming device for a fuze comprising a rotatable casing, an arming member slideably arranged within said casing for movement along the axis of rotation thereof, means including a plurality of inertial balls in frictional engagement with said member for actuating the member to an armed position in time delayed relation with respect to the initial rotation of the casing as the speed of rotation of the balls approaches the speed of rotation of the casing, a normally locked detent slid ably arranged within said casing for maintaining the device in a safe condition until the detent is released and moved in response to the speed of rotation of the casing,

and a bell-crank lever in locking engagement with said detent and pivotally mounted on said casing for releasing the detent for sliding movement as the member is actuated to said armed position.

3. In an impact fuze for a spin missile, a casing, an explosive charge arranged within said casing, a movable member arranged within said fuze in coincidence with the axis of spin of the missile for arming the fuze when the member has been moved longitudinally, means including a plurality of inertial balls in frictional engagement with the member for moving the member longitudinally to an armed position in predetermined time delayed relation with respect to the initial spin of the missile when the balls are moved outwardly in response to centrifugal force as the spin of the balls approaches the spin of the member, means including a bell-crank lever pivotally mounted on said casing and actuated by the movement of the member for arming the fuze when the member has been moved longitudinally a predetermined amount, and means responsive to impact of the missile with a target for firing said explosive charge.

4. In an impact fuze for a spin missile, a casing, an explosive charge arranged within said casing, a movable member arranged within the fuze and constructed and arranged to be moved longitudinally in predetermined time delayed relation with respect to the initial spin of the missile, means including a plurality of balls in frictional engagement with the member and disposed about the axis of rotationthereof and responsive to movement of said bails caused by centrifugal force as the spin of the balls approaches the spin of the missile for moving the member a predetermined amount, means including. a bell-crank lever pivotally mounted on said casing in engagement with the member and operated thereby as the member is moved said predetermined amount for arming the fuze, and means responsive to impact of the missile with a target for firing said explosive charge;

5. In an impact fuze for a spin missile, a casing, an explosive charge arranged within said casing, a movable member arranged within said fuze and having a first annular inclined surface arranged thereon, a member arranged within the fuze and having a second annular inclined surface arranged thereon in opposition and spaced relation with respect to said first inclined surface, a plurality of balls disposed between said members and within said inclined surfaces for moving the movable member longitudinally as the balls are moved outwardly along said inclined surfaces in response to centrifugal force as the spin of the balls approaches the spin of the missile, means including a bell-crank lever pivotally mounted on said casing and responsive to the movement of the movable member for arming the fuze when the member has been moved longitudinally a predetermined amount, and means responsive to impact of the missile with a target for firing said explosive charge.

6. In a fuze for a spin missile, a casing, an explosive charge arranged within said casing, a movable member arranged within said fuze, means including a plurality of balls responsive to centrifugal force as the spin of the balls approaches the spin of the missile for moving the member longitudinally within the fuze, a normally open firing circuit arranged within the fuze, means responsive to movement of said member for closing the firing circuit as the member is moved by said balls, means including a bell-crank lever pivotally mounted on said casing and operated by said member for maintaining the fuze in a safe condition until said member has been moved by the balls and said firing circuit has been closed, a firing device ar ranged within said circuit for generating an electrical firing impulse as the missile moves into proximate relation with respect to a target, and an electroresponsive detonator included within the firing circuit and adapted to be fired in response to said electrical impulse.

7. In a fuze for a spin missile, a casing, an explosive charge arranged within said casing, a movable member arranged within said fuze, means including a plurality of balls in engagement with said movable member and responsive to centrifugal force as the spin of the balls approaches the spin of the missile for moving. the member longitudinally within the fuze, a normally open firing circuit arranged within the fuze, means responsive to movement of said member for closing the firing circuit as the member operates, means including a bell-crank lever pivotally mounted on said casing and operated by said member for maintaining the fuze in a safe condition until the member has been moved longitudinally a predetermined amount and said firing circuit has been closed, a firing device arranged within said circuit for generating an electrical firing impulse as the missile moves into close proximate relation with respect to a target, an electroresponsive detonator included within the firing circuit and adapted to be fired in response to said electrical impulse, and means on the member for short circuiting the detonator until the member has been moved longitudinally.

8. An arming device for a spin projectile comprising a movable arming element, means for normally maintaining the arming element in an initial unarmed postion, means including a pluralityof balls for moving the arming element to an armed position as the speed of rotation of the balls approaches the speed of rotation of the projectile, and means including a bell-crank lever pivotally mounted on said. device and operated by said element. for arming said device as" the element is moved to said armed position.

9; An arming device for a spinprojectile comprising arranged in spaced relation with respect to said first named member, means for normally maintaining the arming member in an initial unarmed position, means including a plurality of balls disposed between said members for moving the arming member to an armed position as the speed of rotation of the balls about the axis of the projectile approaches the speed of rotation of the projectile, and means including a bell-crank lever pivotally mounted on said device and operated by said member for arming the device as the member is moved to said armed position.

10. An arming device for a spin projectile comprising a movable arming element, means for normally maintaining the arming element in an initial unarmed position, a pair of inclined annular cam surfaces arranged within the arming device, a plurality of balls arranged between and normally out of engagement with said cam surfaces for moving the arming element longitudinally to an armed position as the balls are moved outwardly into engagement with said cam surfaces in response to centrifugal force, and means including a bell-crank lever pivotally mounted on said device and operated by said element for arming the device as the element is moved to said armed position.

11. An arming device for a spin projectile comprising a movable arming element, an inclined cam surface on said arming element, means for normally maintaining the arming element in an initial unarmed position, a stationary element in the arming device, a second inclined cam surface on said stationary element and spaced from said first named inclined cam surface, a plurality of balls disposed between said inclined surfaces and normally out of engagement therewith for moving the arming element to an armed position as the balls are moved into engagement with said cam surfaces in response to centrifugal force, a normally locked detent for maintaining the device in a safe condition until the element has been moved to said armed position, and a bell-crank lever pivotally mounted on said device in locking engagement with said 10 detent for releasing the detent as the element is moved to said armed position.

12. An arming device for a spin projectile comprising a movable arming element, means for supporting said element within the projectile for longitudinal and rotative movement with respect to the spin axis thereof, a complementary element secured within the arming device, a pair of frusto-conic cam surfaces respectively disposed on said elements in mutually matching spaced relation, a plurality of inertial balls disposed within said cam surfaces, means for yieldably urging said movable element into engagement with the balls whereby the balls are initially maintained within a predetermined circumferential area between said elements in contact with said surfaces when the movable arming element is in an unarmed position, said balls having sufiicient mass to move the arming element longitudinally to an armed position in time delayed relation with respect to the firing of the spin projectile from a gun when the speed ratios of rotative movement of the balls and the arming element with respect to the spin of the projectile has reached a predetermined value, a normally locked detent slidably arranged within said device for maintaining the device in a safe condition until the detent is released and moved a predetermined amount in response to the spin of said projectile, and a bell-crank lever in locking engagement with said detent and pivotally mounted on said device for releasing the detent as the element is moved to said armed position.

References Cited in the file of this patent UNITED STATES PATENTS 2,118,062 Woodberry May 24, 1938 2,167,197 Brandt July 25, 1939 FOREIGN PATENTS 125,649, Great Britain May 1, 1919 130,084 Great Britain July 31, 1919 573,621 Great Britain Nov. 29, 1945