GB2160954A - Mortars - Google Patents

Abstract

A mortar for providing an aerial infra-red or other display comprises electric timing means for determining the interval between launch of the mortar and initiation of the infra-red display or other dispensing operation. A high-frequency clock generator starts to drive counting means when the mortar is launched, the counting means providing an output to initiate the operation after expiry of a predetermined time delay which is dependent upon the frequency of the generator.

Description

SPECIFICATION Improvements relating to mortars This invention relates to mortars and relates more especially but not exclusively to mortars for use in heat-seeking missile decoy systems.

In such heat-seeking missile decoy systems, the mortars are designed to deploy after a predetermined interval from launch, an infrared radiation display which serves to attract heat-seeking missiles away from a potential missile target (e.g. ship). The predetermined time interval referred to has hitherto been provided by means of a pyrotechnic fuse which is located within the mortar and which is arranged to be ignited at launch of the mortar and designed to ignite infra-red radiation producing material carried within the mortar after the expiration of the aforesaid predetermined time interval.

Such missile decoy systems may be designed to fire a number of mortars in rapid succession from common mortar launching means with the pyrotechnic fuses of the respective mortars being designed to provide an interval between launch and generation of the infra-red display that progressively increases for successive mortars. In this way, the progressive development of the infra-red display as a whole will draw heat-seeking missiles away from the mortar launching position on the potential missile target.

According to the present invention there is provided a mortar, eminently suitable for use in missile decoy systems of the kind described, in which a number of mortars are fired in rapid succession, in which the mortar is provided with simple electric timing means for predetermining the interval between launch of the mortar and initiation of an infrared display or other dispensing operation.

The electric timing means may comprise a high frequency clock generator which starts to drive counting means when the mortar is launched, the counting means providing an output for effecting initiation of the infra-red display or other dispensing operation after the expiration of a predetermined time delay which is dependent upon the frequency of the high frequency clock generator.

The high frequency clock generator may be started into operation by the operation of a launch actuated switch (e.g. a switch carried by the mortar which can operate as the mortar leaves the normal launching barrel).

The electric timing means may be operated by means of a small battery arranged to be connected to the timing means through the launch actuated switch referred to.

The frequency of the high frequency clock generator may be varied in respect of timing arrangements for mortars to be fired in rapid succession to produce a moving IR display.

By way of example, an embodiment of the present invention will now be described with reference to the accompanying single-figure drawing which shows the circuit diagram of a timing circuit arrangement for incorporation in a mortar for producing an infra-red missile decoy display.

Referring to the drawing, the timing circuit arrangement is arranged to be connected to a DC supply PS (e.g. battery) through a switch SW when the contacts thereof are closed consequent upon the launch of the mortar within which the timing circuit arrangement is embodied from the barrel of mortar launching means.

The DC power supply is stabilised by means of a linear voltage regulator comprising a zener diode D1 connected to the base of a transistor TR1 and a resistor R1 connected between the base and collector of the transistor TR1.

The voltage applied to the base of transistor TR 1 causes the transistor to conduct and a pulse is accordingly generated at the junction of capacitor charging circuit comprising capacitor C1 and resistor R2. This pulse is applied to one input of a two input NAND gate IC1 and the other input of this gate IC1 is derived from the emitter of the conducting transistor TR 1. A consequential pulse output from the gate IC1 is transmitted over a reset line RL to reset a multi-stage (e.g. 14 stage) binary ripple counter or divider IC3.

At the same time as the transistor TR1 conducts the stabilised DC output from the transistor causes an astable multi-vibrator defining a high frequency clock generator IC2 to commence oscillating at a frequency dependent upon the Ohmic value of a resistor R3 and the capacitance of a capacitor C2 connected to the clock generator IC2. Since the clock generator IC2 operates at a high frequency [ > 1 Khz] the components of the timing circuit arrangement can be kept very small thereby meeting the very stringent internal space availability conditions appertaining to infra-red mortars.

The output from the clock generator IC2 drives the binary ripple counter IC3 over line IP until the counter produces an output on the line OT. This output causes a field effect transistor TR2 to conduct and thereby connect an igniter IGN across the DC supply. This igniter IGN in the present example is arranged to produce ignition of a readily combustible infra-red payload within the mortar to generate an infra-red display for missile-decoy purposes.

As will readily be apparent from the foregoing description, the time interval or delay between the launch of the mortar when the launch switch SW will be actuated and the ignition of the mortar payload will be determined by the frequency of the clock generator IC2 which in turn is dependent on the ohmic value of the resistor R3. Thus the value of this resistor R3 may be varied for the timing circuit arrangements appertaining to the respective mortars of a group of mortars to be fired in rapid succession thereby producing an infra-red radiation display which effectively moves progressively away from the potential missile target (e.g. ship) from which the mortar will usually be launched. As is fully described in our co-pending Patent Application No. (84 11977) such a group of mortars may be embodied in a unitary multi-mortar pack having common electric sequential mortar firing control means and which may be dropped into the barrel of launching means and the mortars thereafter fired individually in sequence by the application of firing pulses to the mortars through an inductive coupling arrangement.

The present invention provides a very compact variable timing arrangement which provides an extremely reliable alternative to pyrotechnic timing fuses.

Claims (6)

1. A mortar for providing an aerial infrared or other display comprising electric timing means for determining the interval between launch of the mortar and initiation of the infrared display or other dispensing operation.

2. A mortar as claimed in claim 1, in which the electric timing means comprises a high frequency clock generator which starts to drive counting means when the mortar is launched, the counting means providing an output for effecting initation of the infra-red display or other dispensing operation after the expiration of a predetermined time delay which is dependent upon the frequency of the high frequency clock generator.

3. A mortar as claimed in claim 2, in which the high frequency generator is started into operation by the operation of a launch actuated switch.

4. A mortar as claimed in claim 3, in which the electric timing means is operated by a small battery arranged to be connected to the timing means through the launch actuated switch.

5. A missile decoy system comprising a plurality of mortars according to any preceding claim arranged to be launched in rapid succession from a common launching barrel.

6. A mortar substantially as hereinbefore described with reference to the accompanying drawing.