US3721195A - Liquid revolution counter for fuze arming - Google Patents

Abstract

A safing and arming apparatus for use in a spinning projectile in which after a predetermined number of revolutions of the projectile a rotor is unbalanced by the relocation of liquid within the rotor thus causing the rotor to rotate and bring a detonator in line with a firing train.

Description

United States Pateqt n 1 Egli et a1. I I

M lMarch 20, 1973 54] LIQUID REVOLUTION COUNTER FOR FUZE ARMING Inventors: Werner Hans Egli; Asbjorn M. Severson, both of Minneapolis, M inn.

[73] Assignee: Honeywell Inc., Minneapolis, Minn.

[22] Filed: June 1, 1971 [21] Appl. No.: 148,460

[52] U.S. Cl. ..I02/79, 102/78, 102/81 [51] -Int. Cl. ..F42c 15/26 [58] Field of Search ..l02/78, 79, 80, 70, 81

[56] I References Cited UNITED STATES PATENTS 2,641,186 6/1953 Apotheloz ..l02/79 2,331,633 Spooner ..l02/79 2,588,424 3/1952 Speaker 102/702 R 2,703,071 3/1955 Sooth 102/80 3,001,044 9/1961 Brown ....l02/70.2 R

3,075,465 1/1963 Craig ..102/80 X 3,425,354 2/1969 Carlson 102/79 Primary Examiner-Samuel W. Engle Attorney-Charles J. Ungemach, Albin Medved and Alan G. Carlson [57] ABSTRACT V W V A safing and arming apparatus for use in a spinning projectile in which after a predetermined number of revolutions of the projectile a rotor is unbalanced by the relocation of liquid within the rotor thus causing the rotor to rotate and bring a detonator in line with a firing train.

1 Claim, 7 Drawing Figures PIIIENIEDMARZO ma sum 1 OF 4 FIG. IA

SPIN

AXIS

INVENTORS M ATTORNEY PATENTEDMARZO ms 3.721.195

sum 2 a; 4

SPIN AXIS INVENTORS WERNER H. EGU

JORN sevsnson BY ATTORN v PATENTEU M820 I975 SHEET 3 0F 4 FIG; 3A

SPIN AXIS FIG. 38

PATENTEDHARZO ms 3. 721, 195 SHEET u 0F 4 INVENTORS WERNER H. EGLI ASBJORN M. SEVERSON ATTORNEY LIQUID REVOLUTION COUNTER FOR FUZE ARMING BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention pertains to ammunition and explosive devices and, more particularly, to fuzes utilizing the centrifugal force of a spinning projectile.

2. Description of the Prior Art The function of a safing and arming device is to ensure a safe condition in a projectile when it is handled, stored, and fired, and to reliably remove the safing feature and arm the projectile when it has reached a safe distance from the delivery vehicle. This is accomplished by a device designed to respond to forces in the environment of the projectile to remove a barrier or barriers to explosive train function.

Projectile ballistics start with setback forces within the projectile on, firing. The projectile quickly picks up spin as it moves over the rifling in the gun barrel. Then, as it leaves the barrel, setback forces abate and they are replaced by aerodynamic drag, which reduces the velocity, and to a lesser degree the spin, of the projectile.

Generally, sensing at least two environments, such as setback and spin, is required to arm the projectile. The conventional method of arming is to utilize mechanical means. Mechanical fuzes tend to be relatively complex due to the number of parts and the tolerances imposed by size requirements. The dual environment requirement satisfies a high safety factor, but reliability decreases and cost increases with complexity.

BRIEF SUMMARY OF THE INVENTION In accordance with the invention, a revolution counter for fuze arming is provided for counting the number of revolutions which a projectile has experienced subsequent to firing. The revolution counter consists of a liquid-containing rotor mounted within the projectile. The rotor has two compartments, one of which is near the nose of the projectiles and the other. This forward compartment has a portion located further from the spin axis than is the furthermost portion of the rearward compartment from the spin axis. Connecting the two compartments is a drainage vent which allows the liquid to move into the rearward compartment upon the projectile experiencing setback force. Also connecting the two compartments is a timing conduit which leads from a point within the rearward compartment further from the spin axis than is the drainage vent.

Upon furthest firing, the liquid will be forced into the rearward compartment, where, upon experiencing spin forces, the liquid will move to the portion of the rearward compartment which is furthest from the spin axis. The liquid will then begin to squirt out of the timing conduit. The total flow of liquid from the rearward compartment, through the conduit, and, into the forward compartment is dependent upon the number of turns of the projectile. After a predetermined number of turns, enough liquid has escaped from the rearward compartment and arrived at the forward compartment to change the center of gravity of the rotor and thus cause it to rotate.

Accordingly, an object of the present invention is to provide a solely liquidic-contained rotor for a safing and arming mechanism.

Similarly, it is an object of the present invention to provide a device whereby the liquid within the fuze does actual work as opposed to merely being provided to constitute a barrier.

It is an additional object to provide a safing and arming mechanism whereby the arming is dependent upon the number of revolutions of the projectile in which it is housed.

Another object of the invention is to provide a safe, highly reliable, and non-complex safing and arming mechanism.

Another object is to provide a fuze which receives its energy directly from ballistic environmental forces and, therefore, requires no stored energy.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A is an illustration of a preferred embodiment of the invention shown in a projectile head;

FIG. 1B is a view along AA ofFIG.1A;

FIG. 2 shows liquid rotating about an axis;

FIG. 3A is a second embodiment and is a view along B-B of FIG. 38;

FIG. 3B is the second embodiment and is a view along CC of FIG. 3A;

FIG. 4A is an illustration of a third embodiment of the invention; and

FIG. 4B is a top view of FIG. 4A.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1A, a rotor 11 is shown within a projectile head 12. FIG. 1B shows a view along AA of FIG. 1A and isolates rotor 11. Rotor 11 is discshaped and has a cylindrical internal forward compartment l3 (forward with respect to the projectile nose) and cylindrical internal rearward compartment 14 which compartments are separated by a wall 15. Compartment 13 has a portion 16 which is located further from the spin axis than is the furthermost portion 17 of compartment 14. Portion 16 must be large enough to hold enough liquid to unbalance the rotor. A portion 18 is provided to balance the rotor but is blocked from compartment 13 by a separator 19. Wall 15 has a drainage vent 20 connecting an aperture 21 within compartment 13 with an aperture 22 in compartment 14. Wall 15 also has a timing conduit 23 located near the furthermost portion 17 of compartment 14 and connecting an aperture 24 in the rearward compartment 14 with an aperture 25 in the forward compart ment 13. Aperture 24 is located further from the spin axis than is aperture 22 to ensure that centrifuged liquid exits through the timing conduit 23 rather than the drainage vent 20.

Centrifugal locks 26 are provided to restrain the rotor. The rotor rotates about pins 27 upon being unbalanced. A boss 28 rides in a groove 29 to restrain the total movement of the rotor 11.

Also shown is striker 30, which, upon experiencing ground impact, strikes the detonator 31 which in turn initiates booster 32. It is to be understood that the firing train arrangement is quite flexible. For instance, detonator 31 could be just a hole which either a striker or an explosive utilizes in order to reach an explosive located at booster 32.

A liquid 33 is shown centrifuged against the walls of compartment 14. The liquid to be used within the rotor should possess the properties of inviscidity, and high density, and in addition have low viscosity down to 65F and up to 160F. The properties of viscosity and high density vary greatly. The property of high density is needed since it causes a more significant change in the center of gravity of the rotor when it moves. Low viscosity is needed to ensure that viscosity forces are negligible as compared with inertial forces. Liquid Freon E3 sold under the trademark Freon by E. l. Du- Pont deNemours, having a density of 1.72 gm/cc and a viscosity of 1.35 cs at +77F, and liquid Halocarbon l5 sold under the trademark l-lalocarbon by Halocarbon Products Corporation, having a density of 2.75 gm/cc and a viscosity of 0.55 cs at 77F, will satisfy the above requirements.

In operation, setback forces all of liquid 33 down through vent and into compartment 14. As setback abates, due to the projectile leaving the gun barrel, and the spin speed reaches its terminal value, the liquid 33 becomes centrifuged against the walls of the compartment 14 forming a hollow cylinder pressing against the cylindrical walls of compartment 14. This can be seen in FIG. 1A.

However, there is now a radial pressure gradient in the liquid which causes the liquid 33 to flow out of the timing conduit 23 and be centrifuged into portion 16. The rotor geometry, liquid flow speed, and liquid viscosity are selected to ensure inviscid flow. It is important to note that even if aperture 24 is located at portion 17, prior to unbalancing the rotor, the timing conduit 23 cannot follow a path that takes the liquid 33 closer to the spin axis than the inside diameter of the centrifuged liquid within compartment 14, or else the liquid will not enter compartment 13 but will occupy compartment 14 and conduit 23 up to the point of force equilibrium. This is true for all embodiments of the invention.

With the spin rate sufficiently high, centrifugal locks 26 move outward. When a sufficient quantity of liquid has arrived at portion 16, the center of gravity of the rotor will have shifted sufficiently to rotate the rotor about pins 27 thus moving the detonator 31 in line with the striker 30 and the booster 32. It is to be noted that it is not necessary that the rotor rotate about a pivot. For example, the rotor could slide about an infinite radius to arm.

The unbalancing of the rotor is dependent upon the number of projectile turns and independent of the spin rate. Utilizing this fact, the rotor can be built which will arm after a predetermined number of turns. For example, it has been found that for most military projectiles 26 turns will ensure that the projectile is a safe distance from the launch site prior to arming. Reference to FIG. 2 will aid in understanding the dependence upon the number of projectile turns. FIG. 2 shows a quantity of liquid contained in a container spinning about an axis. For inviscid flow, Bernoullis Equation teaches that Where p is the fluid density and V is the exit velocity from the nozzle.

Also, it is known that the pressure difference c A,,) due to centrifugal force is eliminating A yields,

where w is the rate of rotation.

Also, the velocity Vcan be expressed as where Q is the quantity of fluid contained in the container and A is the nozzle area.

Also,

where 0 is the angle traversed about the projectile axis.

Substitution gives But since R, is a function of Q only, and since A and R are constants to be selected by the designer, upon integrating we get Q F(0).

The above analysis is valid only if the flow is inviscid. If flow is viscid, the A,, would be a function of the unsquared exit velocity so that the device would then be dependent upon spin speed.

In order to select the proper size for the revolution counter described in FIG. 1A and 1B, the following analysis can be made. Let the diameter of the cylinder be D let the diameter of the core of the hollow cylinder of liquid be D Then, the hydrostatic pressure difference across the timing conduit is:

(p(/( w 2 l( 1/ 2 l The quantity of liquid in the rearward compartment is:

Q 0/ r/ l Where L is the axial length of the lower chamber, to is the angular spin speed.

Also we have:

where V is the speed at which inviscid liquid squirts through the timing orifice.

But,

Where A is the orifice area, and (dQ)/dt is the rate of depletion of the fluid in the rearward compartment.

I herefore:

pa) 2 Q dt dQ A... 3 WE But since w=d0/dt, this reduces to This integrates to Hence, if arming is desired after N projectile revolutions, and if the value of Q for which the center of gravity displacement makes the device rotate and arm is EQ (0 s' E l), the device is designed so that:

i.e., E= I NA V'nLQ For example, arming will occur after 26 revolution arming with:

Q,,=0.0266 in L 0.5 in

A 0.0025 in The foregoinganalysis is valid only for the geometry cited, but can readily be modified for other geometries, giving the same general result:

Arming M0) In those cases where analysis is too difficult, experimentation will readily determine the values needed for the relevant parameters.

Referring describes to FIGS. 3A and 38, a second embodiment of the invention is shown. This embodiment is shown isolated from the projectile which must be a clockwise spinning projectile. This embodiment described a liquid filled rotor which upon becoming unbalanced rotates horizontally or, as seen relative to the projectile, around an axis parallel to the spin axis. FIG. 3A is a view along B-B of FIG. 3B, and FIG. 3B is a view along C-C of FIG. 3A.

Rotor 40 is shown upon a movable plate 41. Rotor 40 contains a forward compartment 42 and a rearward compartment 43, which compartments are separated by a wall 44. Compartment 42 has a portion 45 which is located further from the spin axis than the furthermost portion 46 of compartment 43. Portion 45 must be large enough to hold enough liquid to unbalance the rotor. Wall 44 has a drainage vent 47 and also two timing conduits 48 (shown in FIG. 3A, but by dotted line in FIG. 38) located near the furthermost portion 46 of compartment 43 and connecting an aperture 49 in the rearward compartment with an aperture 50 in the forward compartment. Drainage vent 47 connects an aperture 51 in compartment 43 with an aperture 52 in compartment 42. Aperture 49 is located further from the spin axis than is aperture 51.

Restrainer 53 prevents the rotor from rotating the plate 41 in a counter-clockwise direction (as seen in FIG. 3A) about a pivot 54. The rotor rotates about pivot 54 upon becoming unbalanced and causes plate 41 to rotate to a stop 55 and thus move detonator 56 in line with the remainder of the firing train.

In this embodiment a liquid 57 is contained and is shown in dotted line in FIG. 3A centrifuged within rearward compartment 43 as would occur upon sensing centrifugal force.

In operation, setback forces all of the liquid 57 down into compartment 43. As setback forces abate, and the spin speed reaches its terminal velocity, the liquid 57 will become centrifuged against the walls of the compartment 43 as shown in FIG. 3A. This distribution of the liquid mass in the lower'compartment causes a counterclockwise torque about the pivot 54 which holds the rotor against the restrainer 53.

However, the centrifugal pressure gradient within the liquid 57 causes it to flow through the timing conduit 48 and into the forward compartment 42. The liquid 57 flowing into the forward compartment 42 disposes itself in a hollow semi-cylinder located further from the spin axis than was the liquid when it was in the rearward compartment 43. When enough liquid has flowed into the forward compartment 42, the shift of the liquid mass distribution to the right side of the rotor will cause a clockwise torque about the pivot 54. This torque will rotate the entire rotor 41 about the pivot 54 and thus move detonator 56 in line. Once again it is not necessary that the rotor rotate about a pin. It could slide to a new position upon becoming unbalanced.

The same type of mathematical analysis as that used for the first embodiment can be used to design the second embodiment for arming after a predetermined number of revolutions.

Shown in FIGS. 4A and 4B is a third embodiment of the invention, isolated from a clockwise spinning projectile. FIG. 4B is a top view of FIG. 4A. A rotor 60 is shown containing a forward compartment 61 and a rearward compartment 62. It can be seen by examining FIG. 4A that the floor 63 of the rotor slants upward from the rearward compartment 62 to the forward compartment 61. Separating the two compartments is a wall 64. Compartment 61 has a portion 65 which is located further from the spin axis than is the furthermost portion 66 of compartment 62. Portion 65 must be large enough to hold enough liquid to unbalance the rotor. Wall 64 has a drainage vent 67, and also a timing conduit 68 located near the furthermost portion 66 of compartment 62 and connecting an aperture 69 in the rearward compartment to an aperture 70 in the forward compartment. Drainage vent 67 connects an aperture 71 in compartment 62 with an aperture 72 in compartment 61. Aperture 69 is located further from the spin axis than is aperture 71.

A restrainer 73 prevents the rotor from rotating counterclockwise about the pivot 74. A stop 75 is provided to restrain the total movement of the rotor in a clockwise direction. Also shown is a blocker plate 76 which blocks the output of a detonator (not shown) from the remainder of the firing train (not shown) until the rotor has rotated to its clockwise position.

A liquid 77 is shown centrifuged against the walls of compartment 62.

In operation, setback forces all of the liquid 77 down the rotor floor 63, through vent 67, and into compartment 62. As setback forces fade out and the spin speed reaches its terminal value, the liquid 77 becomes centrifuged against the walls of the compartment 62, and assumes the shape shown in FIG. 48.

However, there is now a radial pressure gradient in the liquid which causes the liquid to flow out of the timing conduit 68 and travel into the compartment 61. When a sufficient quantity of liquid has arrived at compartment 61 and assumed the furthermost portion 65 from the axis, the shift of the liquid mass distribution to the right side of the device will cause a clockwise torque about the pivot 74. This torque will rotate the entire rotor around the pivot 74 and thus move the blocker plate 76 out of line with the firing train.

While this invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and scope of the claims I claim as my invention:

1. In a projectile which rotates about an axis, a liquid-containing rotor for bringing a detonator in line with a booster and the means for initiating said detonator, comprising:

a rotor containing said detonator, said rotor defining a forward compartment and a rearward compartment, said forward compartment having a portion located further from said axis than is the furthermost portion of said rearward compartment from said axis, said portion of said forward compartment being large enough to hold enough liquid to unbalance the rotor, said rotor having a timing conduit leading from a first aperture near said furthermost portion of said rearward compartment to a first aperture in said forward compartment following a path that is not closer to said axis than centrifuging liquid within said rearward compartment prior to rotor unbalancing, said rotor also having a drainage vent leading from a second aperture in said rearward compartment, said second aperture in said rearward compartment being nearer said axis than is said first aperture in said rearward compartment; and

means restraining said rotor from rotating until a predetermined rotational speed of said projectile;

whereby said rotor is responsive to the movement of said liquid from said rearward compartment to said forward compartment, and thus the number of revolutions of said projectile, for rotating said rotor thus bringing said detonator in line.

Claims (1)

1. In a projectile which rotates about an axis, a liquidcontaining rotor for bringing a detonator in line with a booster and the means for initiating said detonator, comprising: a rotor containing said detonator, said rotor defining a forward compartment and a rearward compartment, said forward compartment having a portion located further from said axis than is the furthermost portion of said rearward compartment from said axis, said portion of said forward compartment being large enough to hold enough liquid to unbalance the rotor, said rotor having a timing conduit leading from a first aperture near said furthermost portion of said rearward compartment to a first aperture in said forward compartment following a path that is not closer to said axis than centrifuging liquid within said rearward compartment prior to rotor unbalancing, said rotor also having a drainage vent leading from a second aperture in said rearward compartment, said second aperture in said rearward compartment being nearer said axis than is said first aperture in said rearward compartment; and means restraining said rotor from rotating until a predetermined rotational speed of said projectile; whereby said rotor is responsive to the movement of said liquid from said rearward compartment to said forward compartment, and thus the number of revolutions of said projectile, for rotating said rotor thus bringing said detonator in line.

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