US3919941A

US3919941A - Liquid timing device

Info

Publication number: US3919941A
Application number: US400557A
Authority: US
Inventors: David S Breed; Torbjorn Thuen; Allen K Breed
Original assignee: Individual
Current assignee: Individual
Priority date: 1973-09-25
Filing date: 1973-09-25
Publication date: 1975-11-18
Anticipated expiration: 1992-11-18

Abstract

The fuzing device of this invention, comprises a hermetically sealed housing filled with liquid and containing a detonator, a sensing mass, and a spring loaded firing pin, in such an arrangement that when the fuzing device is subjected to the proper acceleration stimuli the detonator becomes aligned with an output lead and the firing pin is released which initiates the detonator which in turn initiates the output lead.

Description

Boonton Township, NJ. 07005; Torbjorn Thuen, 12 Ahern Way, Roseland, NJ. 07068; Allen K. Breed, 153 Farber Hill Road, Boonton Township, NJ. 07005 [22] Filed: Sept. 25, 1973 [21] Appl. No.: 400,557

'[52] US. Cl 102/78; 102/81 [51] Int. Cl. F42C 15/24 [58] Field of'Search 102/73, 74, 75, 76, 77,

[56] References Cited UNITED STATES PATENTS 1,309,768 7/1919 Newall 102/75 Umted States Patent [191 [11] 3,919,941 Breed et a1. Nov. 18, 1975 LIQUID TIMING DEVICE 1,309,773 7/1919 Newall 102/73 R W61 Davids-BMW HillcrestRoad, 1233831 11133? ?5??..?1331111i3i1311 58/144 Primary Examiner-Ver1in R. Pendegrass Attorney, Agent, or Firm--Kane, Dalsirner, Kane, Sullivan and Kurucz [57] ABSTRACT The fuzing device of this invention, comprises a hermetically sealed housing filled with liquid and containing a detonator, a sensing mass, and a spring loaded firing pin, in such an arrangement that when the fuzing device is subjected to the proper acceleration stimuli the detonator becomes aligned with an output lead and the firing pin is released which initiates the detonator which in turn initiates the output lead.

13 Claims, 5 Drawing Figures DAVID S. BREED, TORBJORN THUEN ALLEN K. BREED INVENTQR N DALSIMEI?,KANE, SULLIVAN AND KL/FUCZ ATTORNEY US. Patent Nov. 18, 1975 Sheet2of5 3,919,941

DAVID S. BREED,TOI?BJOEN THUEN ALLEN .BREED INVENTOR KANE. DA! QJMEP. KANE\ SULLIVAN AND KUPUCZ TORNEY U.S. Patent Nov. 18,1975 Sheet30f5 3,919,941

IOI

FIG

DAWD s. BREED, TORBJOEN THUEN ALLEN K. BREED INVENTOR KANE, DALSIME'E, KANE, SULLIVAN AND KLIEUCZ ATTORNEY U.S. Patent Nov. 18,1975 Sheet4 0f5 3,919,941

I55 I5I I I57 I56 I59 DAVID S.B EED,TORBJORN THUEN 6;. ALLEN K. BREED INVENTOR KANE, DALSIMER KANE SULLIVAN AND KUEUCZ ATTORNEY DAVID S.BI?EED,TORBJORN THUEN 15 ALLEN K. BREE D INVENTOR ANE,DAL$|MEI?, KANE, SULLIVAN AND KUEUCZ R EY LIQUID TIMING DEVICE BACKGROUND OF THE INVENTION The fuzing device of the present invention has application to solving munitionfuzin'g problems, acceleration sensing problems, such as crash sensors, as well as other timing and integrating problems.

In recent years the fuzing for munitions such as rockets, bombs, mortars and artillery has been increasing in complexity. This has been brought about by the desire for greater safety against possible malfunctions, a desire for greater reliability to prevent dud ammunition, and to increase the effectiveness of the munition against special targets. These requirements have tended to be somewhat incompatible and have increased the complexity and the cost of fuzes.

The timing device of the present invention in most applications results in a dramatic increase in fuze safety, provides all of the options currently available on standard fuzing, plus numerous options heretofore unavailable, simultaneously results in a dramatic decrease in fuze costs.

For most applications all fuze components are contained in a hermetically sealed cylinder less than threequarters of an inch in diameter and 1% inches long which is completely filled with a low viscosity liquid. The fuzing device has universal application to rockets, mortars, artillery, projected grenades and bombs. The options available in this fuzing device consist of the following:

l. A setback integration system which accurately differentiates between a 40 foot drop onto any surface and zero increment mortar firing.

2. Constant distance arming for rockets.

3. Constant time arming for mortars.

4. Constant distance arming for artillery.

5. Spin sensing for artillery.

6. Impact deceleration integration causing detonation resulting in capability of canopy penetration or as a dud elimination backup to point detonation system. I

7. Highly sensitive graze sensitivity.

8. Fixed time delay detonation after impact;

9. Void sensing for bunker penetration.

l0. Detonation a fixed time after launching.

l 1. Point detonation. I 7

l2. Retardation sensing for retarded bombs.

13. Fail safety.

Other fluid fuzes using dashpot principles have been applied successfully to solving particular munition fuze timing problems. Most of these parts, necessitating selective assembly or unusual gaging techniques. For most applications of the timing device of the present invention all of the parts can be produced on standard high volume production metalworking machines.

In contrast to most fuzes currently produced the fuzing device of the present invention is usually entirely hermetically sealed permitting unprotected storage in such adverse conditions as submerged under 100 feet of water. The hermetically sealed envelope is entirely filled with a damping fluid and thus all fuze components are unaffected by rough handling or vibrations at any frequency. In addition, for many applications there is no restriction as to the location of the fuze within the munition. This feature, plus the small size'permits the use of multiple fuzing devices in a single munition even 2 buried within the main explosive charge if extreme reliability is desired.

Safety against unintended detonator initiation is significantly superior to current fuzing. Detonator initiation can occur only if the fuze experiences the exact acceleration time function characteristic of a normal launch followed by an arming period wherein the fuze must experience the proper acceleration stimulus of non-spin, free-flight (mortars), spin, free-flight (artillery, projected grenade) or rocket motor acceleration, and finally followed by the target impact deceleration time function chosen to cause round detonation.

The total immersion of all fuze components in an inert liquid assures that no degradation of fuze safety or performance over prolonged storage in corrosive environments or extended exposure to severe vibrations or rough handling will take place. Rupture of the hermetic seal and loss of the liquid results in a fail safe condition.

Prior art devices consist of US. Pats. No. 3,425,354-Feb. 4, i969, to D. Carlson and US. Pat. No. 3,296,969Jan. 10, 1967 to J. W. Mueller et al. The Carlson patent relates to a centrifugally armed fuze, wherein a portion of the fuzing mechanism is totally immersed in fluid. Initiation of the fuze however, requires a physical displacement of the firing pin which is external to the arming mechanism and not immersed in fluid. Thus the fuze cannot be arbitrarily located in the projectile since a physical means must be present to displace the firing pin. Also, since the firing pin mechanism is not immersed in fluid it is subject to being degraded by vibration, and, unless the fuze is hermetically sealed, the fuze cannot be stored in adverse environments. The fuze of the present invention is totally sealed with all parts necessary for arming and functioning of the device contained in the liquid filled housing. The Mueller patent is concerned with a time delay initiator. No provision is made for keeping the sensitive ex plosive primer out of alignment with the main explosive charge which is a basic requirement of all munition fuzes.

In addition, the firing pin is part of the sensing mass thus the sensing mass must obtain sufficient velocity and kinetic energy to initiate the primer. In most cases this requires a much larger sensing mass than in the case of the present invention where the sensing mass is used to release a much larger amount of stored energy. With the firing pin energy stored in the firing pin spring, much smaller kinetic energy is required in the sensing mass and thus the sensing mass can be considerably smaller. In addition, the direction of motion of the sensing mass can be arbitrary. It can be in the same direction, perpendicular, or in the opposite direction to the motion of the firing pin. All other prior art devices of which the applicant is aware are variations of simple dashpot mechanisms and do not realize the many advantages obtained through practicing this invention.

Many of the same advantages listed above apply to the use of this fuzing device as an integrating accelerometer used in conjunction with inflatable safety bags for sensing automobile and airplane crashes. Most crash sensors currently available are mass spring systems which are comparatively slow integrators. In addition, their output is the closing of an electrical switch which requires an auxillary power source to protect against malfunctioning of the primary power source, as well as monitoring circuitry. The fuzing device of the present invention has an explosive output eliminating the need for either auxillary power or monitoring cir- 3 cuitry.

Thus, the fuzing device of the present invention has been eminently successful in eliminating the drawbacks of the prior art in both fields of munition fuzing and crash sensing.

SUMMARY OF THE INVENTION The fuzing device of the present invention comprises a liquid filled housing containing one or more timers or integrators wherein the time delays are accomplished through the displacement of the liquid. The housing also generally contains an explosive element which is initially held out of alignment with an explosive lead which aligns and is initiated at the conclusion ofa delay or upon the occurence of a prescribed stimulus and when initiated explodes through a wall of the housing to initiate a desired action external to the housing.

The housing also contains a sensing mass and spring loaded firing pin wherein the sensing mass under the proper external stimuli moves to release the spring loaded firing pin.

One of the primary objects of this invention is to provide for an extremely safe munition fuze.

Another object of this invention is to provide for an exceptionally reliable munition fuze.

Still another object of this invention is to provide for an exceedingly inexpensive munition fuze.

An additional object of this invention is to provide for a hermetically sealed munition fuze.

Another object of this invention is to provide for a munition fuze which is not degraded by vibration.

A further object of this invention is to provide for a munition fuze which can be stored in adverse environments.

Still another object of this invention is to provide for a small selfcontained munition fuzing element which permits its dedundant use within the munition.

An additional object of this invention is to provide for a munition fuze capable of differentiating between a 40 foot drop onto any surface and a minimum acceleration mortar firing.

Another object of this invention is to provide a liquid fuze capable of giving constant distance arming for rockets.

Still another object of this invention is to provide a liquid fuze capable of giving constant time arming for mortars.

An additional object of this invention is to provide for a munition fuze whose detonation occurs a fixed time after impact.

An additional object of this invention is to provide a fuze which will ignite a fixed time delay after launching.

Another object of this invention is to provide for a fuze which will fail safe in the event the hermetic seal has been ruptured.

A further object of this invention is to provide for a non-electrical crash sensor.

Still another object of this invention is to provide for a crash sensor whose response is extremely fast.

Other objects and advantages of this invention will become apparent as the description progresses.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings in which five of various embodiments of the present invention are illustrated:

FIG. 1 is a cross-sectional view of the teachings of the present invention applied to gun ammunition;

FIG. 2 is a cross-sectional view of a crash sensor;

FIG. 3 is a cross-sectional view of a mortar fuze showing the setback integration and fail safety features of the teachings of the present invention;

FIG. 4 is a partially sectioned view of a rocket fuze having constant distance arming; and

FIG. 5 is a partially sectioned view of a mechanism which delays detonation for a fixed time after impact;

DESCRIPTION OF THE PREFERRED EMBODIMENTS A fuze used for gun ammunition, such as 20mm., constructed in accordance with the teachings of this invention is shown generally at 50 in FIG. 1. The housing comprises an upper portion 51 and a base portion 52 hermetically joined together at 53. All voids within the housing are filled with fluid and a small amount of fluid vapor 54. Upon experiencing spin comparable to a true firing condition balls 55 move radially outward due to centrifugal forces. This action puts a upward force on firing pin 56 and when balls 55 have reached their outermost radial position, firing pin point 57 is removed from a position where it was locking ball rotor 58 permitting it to rotate in such a manner as to align detonator 59 with the firing pin point 57. Upon target impact firing pin 56 is driven into detonator 59 igniting lead 60 which blows through a thin portion 61 of housing base 52 igniting lead 62.

Apparatus constructed in accordance with the teachings of this invention for use as a crash sensor for the deployment of inflatable vehicle safety bags is shown generally at in FIG. 2. A housing 81 having all of its voids filled with fluid 82 and hermetically sealed by sealing disc 83 contains a sensing mass 84. Upon a sudden deceleration in the upward direction in FIG. 2 sensing mass 84 begins moving upward and creates a high pressure in the volume 85 above piston 87. As a result of the restricted liquid passages below volume 85, this pressure is maintained and acts on end 86 of piston 87 causing piston 87 to move from its illustrated position engaging nib 97 downward aligning detonator 88 with lead 89. Simultaneously, pin 90 is forced into opening 91 by tab 92 on firing pin 93 releasing firing pin 93 which is propelled into detonator 88 by spring 94. The motion of piston 87 downward is resisted by the flow of fluid 82 through orifice 96. Through the proper choice of fluid kinematic viscosity, orifice diameter, the dimensions of the various parts, etcetera, an integrating accelerometer can be designed to respond to a 30 mile per hour automobile crash, for example, and yet not respond to a crash at 10mph. The required calculations can be easily performed by those skilled in the art. Upon experiencing the proper crash environment, lead 89 ignites gas generating equipment not shown which inflates the safety bag.

Apparatus constructed according to the teachings of this invention for use as a mortar fuze is shown generally at in FIG. 3. A housing 101 is sealed to a top 102 by gasket 103 in the conventional manner common to the tin can industry. Similarly, bellows 104 is solder sealed to top 102. All voids within housing 101 are filled with fluid 105. When the mortar shell is fired setback acceleration acting on weight 106 urges it downward. Upon reaching bottom 107, ball 108 is permitted to move into the volume above mass106 releasing piston 109 which begins moving downward powered by spring 110. When piston 109 reaches bottom 111, detonator l12 is aligned with lead 1 13. By this time weight 106 has returned to its neutral position. Also at this time, pin 113 has been forced into hole 114 by virtue of a force exerted on it by conical section 115 of firing pin 116. Upon impact with a target, weight 106 moves upward due to impact deceleration and upon reaching top 117, pin 113 is permitted to move to the right unlocking firing pin 116 frompiston .109. Spring 110 then propels firing pin 116 into detonator 112 setting off the detonator which explodes through bottom 111 and ignites lead 113 which carries the explosion to the booster (not shown) which ignites the main explosion.

Each of the functions described in the preceding paragraph has associated with it a timing or integrating delay. In order to provide a clear understanding of the operation of this embodiment of the invention each of these delays will now be analyzed in more detail.

Each of the timers and integrators used in this embodiment of the invention is based on the Sharp Edge Orifice Dashpot technology as disclosed'in D. Breed U.S. Pat. No. 3,563,024, filed Aug. 27, 1969. The simplest embodiment of the dashpot consists of a piston having a sharp edge orifice traveling in a cylinder in such a manner that the predominant fluid flow occurs through the sharp edge orifice with flow in the clearance between the piston and cylinder being negligible.

In addition, flow in the orifice must be at sufficiently large Reynolds numbers so that viscous effects in the orifice can be neglected. In all cases the resistance to the motion of the piston arises from the inertial flow of the fluid through the orifice and the piston arises from the inertial flow of the fluid through the orifice and the dynamics of the piston can be neglected. To assure inertial flow, the fluid kinematic viscosity will in most cases be less than.l0 centistokes.

Bernoullis equation for this case becomes simply:

P V l p T v 2 Therefore, V 2P/p and, Q KBV KB 2P/p Also,

. Q KB 2P giving Where:

I time delay (sec.)

L length of piston travel (in.)

A area of piston cross section (in B area of orifice (in p density (lbs/sec in K experimental orifice constant (approximately .7)

F= force (lbs) V velocity of fluid in orifice (in/sec) X velocity of piston (in/sec) Q volume flow rate (in /sec) For equation (3) to be accurate the flow through the clearance must be negligible over the entire temperature range of operation. In addition, viscous effects in the orifice must be negligible which implies that the 6 Reynolds number must be significantly greater than 1 and that the ratio of the length to diameter of the orifice should be small.

The time delay as expressed in equation (3) is not dependent on the viscosity of the fluid and thus will be practically independent of temperature. The time delay is. also inversely proportional to the square root of the applied force which, as will be shown, renders the dashpot an ideal distance integrator.

For all safety and arming devices and particularly for non-spin projectiles, it is mandatory that the arming delay be initiated only after a true firing and not after an accidental drop. A sharp edge orifice dashpot designed for such a purpose comprises weight 106. During an upward acceleration weight 106 is subjected to a force equal to its effective mass times the magnitude of the acceleration. The motion of weight 106 is restricted, however, by the requirement that the fluid must flow from'the volume 118 beneath this piston through the sharp edge annular .slit 119 to the increasing volume 120. If the acceleration is of a sufficient magnitude and duration, such as experienced in a true firing, the weight 106 will travel downward far enough to permit lock ball 108 to enter volume 118 initiating the arming delay. If the acceleration is not of sufficient magnitude and duration the mass will return to its initial position.

In order for arming to actually be initiated in a partic ular configuration, other circumstances must be present such as continuous fluid pressure beneath the weight to verify that the fuze in in fact entirely filled with fluid, and round spin the case of a similar design used for artillery.

In one considers constant acceleration pulses (step functions) the time delay for this dashpot becomes, from equation (3):

LA p KB 28/111 Where:

h length of the mass (in) a acceleration (in/sec p m density of the mass (lb./sec in This can be rewritten as:

a C where,

LA p C- 2 h constant (5) g acceleration of gravity (ft/sec 7 X drop height Thus a setback sensor must differentiate between a firing resulting in a muzzle velocity of, for the case of a minimum mortar firing, 160 ft/sec and 80.4 ft/sec for the case of a 100 foot drop. This can be accomplished by using a bias spring. The equation for the time delay then becomes:

Y=C' (61-11 (9) Where:

I KB 26h c When Y L, the arming delay is initiated.

For a given muzzle velocity (or given impact velocity for a drop) a constant acceleration (or deceleration) will give the maximum value ofY. Assuming a constant l V/a Therefore 2 a2 constant Differentiating to find the maximum:

Therefore:

Substituting (2.2.7) and (2.2.8) into (2.2.6) gives:

Thus if the spring force is chosen such that a is just sufficient for Y L for the minimum velocity firing, the mass displacement under a drop will be proportional to the velocity ratio. Since the minimum mortar muzzle velocity is more than twice the maximum drop impact velocity when dropped from 100 feet, the mass under the 100 foot drop would move only one-half the distance required to initiate arming.

Firing and drop pulses are of course not step pulses and a time step simulation computer program has been written to take actual firing pulses as well as step drop pulses. The particular design analyzed consisted of a weight an ID. of 0.375 inches, a CD. of 0.525 inches and a length of 0.625 inches, The clearance required to maintain the flow through the clearance to within about 1 percent of the flow through the orifice was 0.002 inches. The orifice clearance was 0.008 inches. In each firing case the mass reached the extent of its travel (0.200 inches) in ample time to initiate arming before the end. of the acceleration pulse. When dropped from 40 feet and striking the target with a g deceleration the mass moved less than half of the required distance. In addition the-Reynolds numbers are higher by at least an order of magnitude than needed to assure inertial flow dominance thus assuring complete temperature independent operation.

Once the lock ball 108 has released the piston 109 the detonator begins traveling toward alignment with the lead. This piston is also a piston ofa sharp edge orifice dashpot and thus by varying the orifice diameter, and the driving spring force, the time delay can be varied from milliseconds to a minute or more. For the case shown in FIG/3 a 3 second time delay corresponding to conventional mortar fuzing requirements was chosen.

A typical set of design parameters consists of an orifice diameter of 0.0064 inches which yields a time delay of 3 seconds with 8 percent of the flow passing through the 0.001 inch clearance between the piston and cylinder. The maximum variation in time delay over the temperature range of 65F to F for a 0.0064 inch orifice is 14 percent. Thus, if the time delay is 3 seconds at 65F it would decrease to 2.6 seconds at 160F. This variation over temperature could easily be eliminated through the use of a smaller clearance, However, since this variation is well within the arming time tolerance permitted for mortar fuzes, a 0.001 inch clearance can be used permitting low cost manufacturing tolerances and assembly.

The weight 106 can also be used to assure detonation of the projectile regardless of the target. During impact the weight moves upward permitting one or more detent pins to release the firing pin initiating the round. The distance traveled by the projectile from the instant of impact until round initiation for the case of constant deceleration is:

From equation (6):

A a! C Thus,

Where,

V= shell impact velocity ft/sec a deceleration (ft/sec c 4,6828: constant (ft) Since for most cases it is desired to detonate the shell r 9 Thus the distance travelc d. is inversely proportional to the square root of the deceleration. lfthe deceleration is large as in a hard target the shell will fire practically on impact. For low deceleration. targets such as water, brush, or small graze angles the shellwill travel somewhat further. 5

The sensitivity can beset by the dashpot parameters and the bias spring. If the bias spring is omitted it. will be impossible to stop the shell without detonating it. A stronger bias spring might be used if canopy penetration is desired. Since the distance traveled is proportional to the inverse square root of the deceleration, it effectively amplifies the effect of soft targets eliminating duds which result from low decelerations such as in the case of rockets getting caught in canopy, low graze angles or impact into marsh.

A constant distance arming rocket fuze constructed in accordance with the teachings of the present invention is shown generally at 150 in FIG. 4. In Equation 6 the ability of the sharp edge orifice dashpot to act as a distance integrator was demonstrated. This can be converted to a constant distance arming fuze by the addition of bias mass 151. At the required bias level, such as 25 gs, the bias mass 151 rapidly moves to bottom 152 of cylinder 153. The arming mass 154 begins moving downward due to the acceleration of the rocket and its position is a convenient measure of the distance the rocket has traveled. If the rocket motor acceleration continues until the rocket has reached the desired safe separation distance, lock ball 155 will be released permitting detonator assembly 156 to rapidly move downward aligning detonator 157 with lead 158. If the acceleration is of insufficient magnitude and duration, the bias spring 159 returns the bias mass 151 and arming mass 154 to their starting positions. All voids within the housing 160 are of course filled with fluid 161.

For cases where detonation, a fixed time after impact, is desired, the firing pin itself can become a sharp edge orifice dashpot piston as shown in FIG. 5. Here the leading edge 220 of firing pin 221 forms a restriction with cylinder wall 222. After moving a short distance during which time the delay is achieved, leading edge 220 reaches an expanded portion 223 of cylinder 222, permitting relatively free motion of the firing pin the remaining distance to the detonator 224. The resistance to fluid flow between the cylinder 222 and the rear portion of the firing pin 225, would be maintained small throughholes and axial grooves or a reduced diameter on that portion on the firing pin.

Since all of the time delays and acceleration integrating features of the apparatus described herein depend for their operation on the housing being substantially filled with fluid, malfunctioning will occur if fluid is not present. Although quality control checks are envisioned during manufacture and the seals illustrated have been perfected to the point that failures are virtually unknown, nevertheless, the precaution can be taken in the basic design to fail safe if sufficient fluid is not present. The operation of this system can be seen in FIG. 3.

Prior to setback, the locking ball 108 prevents the arming piston 109 from moving rearward. During setback, the impact-setback piston 106 begins moving rearward and creates a pressure below the piston 109 if sufficient fluid is present. This pressure acts on the piston through the cylinder orifice 400 raising it slightly and permitting the arming piston 109 to urge the locking ball outward. If, just prior to completion of its travel, .fluid pressure still exists and is sufficient to maintain the arming piston in the forward position, the locking ball 108 will be forced outward into the volume forward of the setback mass. Thus, at the cessation of setback, alignment of the detonator will commence. This system assures that the volume below the piston must be entirely filled with fluid at the time that the arming piston is released. If fluid pressure is not present at the beginning of the motion of the impact-setback piston, then the arming piston 109 will not move forward and the lock ball 108 will not be urged into the unlock position. If for some reason the fluid pressure was present at the beginning but absent at the end of the travel of the impact-setback piston, then once again, the arming piston containing the detonator will not be released to commence the arming delay.

In order to provide for expansion and contraction of the fluid due to temperature changes, a bellows 104 has been provided in the upper portion of the fuze. This bellows also expands to permit the rapid forward motion of the arming piston in response to the pressure created beneath the arming piston during setback.

As an alternate for some applications, a gas or preferably fluid vapor bubble could be used to provide for expansion and contraction of the fluid with temperature. In the case of a vapor bubble, fail safety would still work since the acceleration forces would place the bubble at the top of the housing.

For the purposes herein primer means any explosive element including detonators which can be initiated by a firing pin.

Thus the numerous aforementioned objects and advantages among others are most effectively obtained, although several preferred embodiments and applications have been described, discussed and illustrated above, it should be understood that this invention in no sense limited thereby but its scope is to be determined by that of the appended claims.

We claim:

1. A fuzing device comprising a liquid tight sealed housing containing a liquid having a kinematic viscosity less than 10 centistokes; a primer in the liquid adapted to move from a first position relative to an output lead to a second position relative to the output lead; means for causing the movement of the primer to the second position after sensing a predetermined external stimulus, said means including the liquid and a movable sensing mass in the liquid, the liquid acting to offer resistance to movement of the mass; a firing pin in the liquid and a release means in the liquid cooperating with said firing pin to release said firing pin following a predetermined motion of said sensing mass against resistance offered by the liquid upon sensing a predetermined external stimulus.

2. The invention in accordance with claim 1, wherein the means including the liquid and the mass provides at least one time delay to delay the motion of the primer to the second position which involves liquid flow at sufficiently high Reynolds numbers that inertial forces dominate over viscous forces.

3. The invention in accordance with claim 2 wherein said mass is so designed as to initiate an action when subjected to an acceleration characteristic of a normal projectile launch environment, and to fail to initiate said action when subjected to an acceleration characteristic of a 40 foot drop condition.

4. The invention in accordance with claim 2, wherein said mass is so designed as to give substantially constant 1 1 distance arming when used in a rocket fuze.

5. The invention in accordance with claim 2 wherein means are provided to achieve approximately constant time arming for mortars.

6. The invention in accordance with claim 2 wherein said time delay involves a mechanism comprising a mass and a spring which prevents initiation of an action unless a certain threshold deceleration is experienced by the projectile containing the timing device.

7. The invention in accordance with claim 2 wherein the fuzing device includes at least one time delay means for providing an action at a predetermined time after impact of the projectile.

8. The invention in accordance with claim 2 wherein means are provided to initiate an action a fixed time delay after launching of a projectile containing said timing device.

9. The invention in accordance with claim 2 wherein the means varies the length of a time delay as a function of the deceleration of the vehicle containing the timing device.

10. The invention in accordance with claim 1 wherein means are provided to adapt the fuzing device to a projectile.

11. The invention in accordance with claim 1 wherein means are provided to adapt said fuzing device to act as a crash sensor.

12. The invention in accordance with claim 1 wherein means are provided to adapt the fuzing device to gun ammunition.

13. The invention in accordance with claim 2 containing a passage means defining a passage in the housing and being so designed that under normal operation, a liquid flows in the inertial regime where the Reynolds number is large and greater than 1 in that portion of the passage having the greater resistance to flow, so that viscous effects in the passage may be neglected and the said one time delay is governed by the flow of the liquid through the passage; the said one time delay being relatively independent of the viscosity of the liquid and consequently somewhat independent of temperature.

Claims

4. The invention in accordance with claim 2, wherein said mass is so designed as to give substantially constant distance arming when used in a rocket fuze.