GB2266135A - Hand-thrown munition fuze - Google Patents

Abstract

The hand-thrown munition fuze improves the safety and usefulness of hand-thrown munitions by: Ensuring that a pre-set launch velocity is reached before the timing function can operate e.g. by means of a 3-dimensional accelerometer and integrating circuit. The time delay can be adjusted and the launch velocity threshold can be removed to facilitate the use of the munition in non hand thrown modes. The munition can be sterilized/neutralized at a limited time after arming.

Description

TVT HAND-THROWN MUNITION FUZE This invention improves the safety of hand-thrown munitions.

NATO agreements (eg STANAG 4187) require that explosive munitions be fitted with two independent safety features, each having its own distinct action and sensing different environments, to prevent premature functioning (ie detonation before a safe separation distance is achieved following the deliberate action of an operator to use the munition). To date, the fuzes of hand-thrown munitions have not complied with this requirement, as they have been fitted with only one safety feature (the fly-off lever with a time delay). This does not prevent hazardous functioning when dropped, or otherwise released, before throwing.

The TVT hand-thrown munition fuze incorporates a second, independent, safety feature to prevent premature function, and additional features are introduced to assist the user and improve safety. These are achieved by: a. The embodiment of a 3-dimensional accelerometer and suitably programmed micro-processor controlled integrator ensures that the munition reaches a specified launch velocity before the timing device can commence to operate on the release of the thrower's hand.

b. It also contains a switch to allow the operator to vary the time delay and release velocity threshold to facilitate the use of the munition in secondary modes (such as booby-trap).

c. Battery storage life is preserved by disconnecting all power until the system is armed by the removal of the safety pin.

d. Neutralization/sterilization of the fuze, after arming, is provided by the limited capacity of the battery to provide power when connected to the fuze.

Figure 1 is a schematic logic diagram of the design of existing handthrown munition fuzes. Basic safety is provided by a fly-off lever which is locked in position by a safety pin. Manual operations thereafter, are: a. When being prepared for throwing, the munition and its fly off lever are grasped, the latter being retained in the safe position by the hand once the safety pin is removed.

b. When thrown, the fly-off lever is released and a timing device is initiated.

c. The timing device initiates the munition on the expiry of the time set.

NOTE: If the fly-off lever is released, for any reason, before the munition is thrown, then it is inevitable that the timing sequence begins and the munition explode.

Figure 2 illustrates the principle mode of operation of a TVT handthrown munition fuze, once the munition has been armed by the removal of the safety pin. The sequence is as follows: a. The output of a 3-dimensional accelerometer is integrated to give velocity (compensated for the effects of gravity). This is fed to one input of the logic 'AND' gate.

b. The signal from the fly-off lever is fed to the other input of the logic 'AND' gate.

c. The thresholds of the 'AND' gate are set to ensure that no output is present unless the velocity input is greater than, say lOmis, before the signal from the fly-off lever is received.

Only if the correct sequence of inputs are present will an output be produced.

d. The output from the 'AND' gate, commences the timing sequence; which, once complete, detonates the munition.

Additional features are provided by: a. The battery being disconnected from the fuze, thus ensuring that the fuze remains inert, until the safety-pin is removed from the munition; see Figure 3 below.

b. The battery being again disconnected, returning the fuze to the inert state, if the safety-pin is replaced.

c. Battery life being limited, rendering the complete munition safe (sterilized/neutralized) if the safety-pin is removed for longer than a desired period.

d. A small change-over switch, to set logic tolerances, may be incorporated to: (1) Allow selection of various time delays.

(2) Reduce and/or remove the velocity threshold, to allow the munition to be used in a non-thrown role (ie booby trap).

Claims (7)

1. Claim 1. The TVT hand-thrown munition fuze incorporates a device for measuring velocity of throw to prevent premature functioning of the munition.
2. Claim 2. The TVT hand-thrown munition fuze, as claimed in Claim 1, contains a 3-dimensional accelerometer and integrating circuit to determine the velocity of the munition.
3. Claim 3. The TVT hand-thrown munition fuze, as claimed in Claim 1 or Claim 2, contains an accelerometer and integratingcircuits which compensate for the effects of gravity.
4. Claim 4. The TVT hand-thrown munition fuze, as claimed in Claim 1, contains a device which disconnects the battery whenever the safety pin is in place.
5. Claim 5. The TVT hand-thrown munition fuze, as claimed in Claim 1 or Claim 4, contains a device to allow the user to adjust the time delay before functioning.
6. Claim 6. The TVT hand-thrown munition fuze, as claimed in Claim 1 or Claim 2 or Claim 3 or Claim 5, contains a device to allow the user to alter and/or remove the velocity threshold to facilitate the use of the munition in nonhand-thrown modes.
7. claim 7. The TVT hand-thrown munition fuze, as claimed in Claim 1 or Claim 2 or Claim 3 or Claim 4 or Claim 5 or Claim 6, is fitted with a battery having a limited life when connected to the device, so as to ensure that the munition is rendered safe (sterilised/neutralised) after a set period of being armed.