Mortar safety device

Abstract

A safety device for a front-loading weapon of the type comprising a mortar barrel having a closed breech end and an opposite open end for launching a mortar projectile. The device includes at least one sensor, configured for mounting adjacent the mortar barrel, for sensing a mortar projectile upon its insertion in the barrel and an electronic circuit, coupled to said sensor, for detecting movement of the mortar projectile past said sensor, thereby to detect the presence of the projectile in the barrel.

Claims

1. A safety device for a front-loading weapon comprising a mortar barrel having a closed breech end and an opposite open end for launching a mortar projectile, said safety device comprising, in combination: (a) at least one sensor, mounted on the mortar barrel, for sensing a mortar projectile when the projectile moves past the sensor within the barrel; (b) an electronic logic circuit, coupled to said sensor, for detecting the presence of the mortar projectile in the barrel as the projectile moves past said sensor, both when entering and exiting the barrel, and for determining when the mortar projectile remains inside the barrel longer than expected; and (c) a warning device, coupled to said electronic logic circuit, for providing at least one of a visual and audible warning when the mortar projectile remains in the barrel longer than expected and has thus failed to timely fire, whereby a weapon user is warned against inserting another mortar projectile into the barrel.

2. The safety device of claim 1, wherein said warning device produces at least one of an audible and a visual indication of the presence of the mortar projectile in said barrel.

3. The safety device of claim 1, wherein said sensor is mounted on the mortar barrel adjacent said open end of said barrel.

4. The safety device of claim 1, wherein said sensor is mounted on the mortar barrel substantially midway between said breech end and said open end of said barrel.

5. The safety device of claim 1, wherein said sensor is mounted on the mortar barrel adjacent said breech end of said barrel.

6. The safety device of claim 1, wherein said sensor includes a metal detector.

7. The safety device of claim 6, wherein said metal detector includes a coil of wire windings and said electronic circuit is operative to detect changes in an electric current in said coil caused by a movement of the projectile past said coil.

8. The safety device of claim 7, wherein said wire windings of said coil surround said barrel.

9. The safety device of claim 6, wherein said metal detector includes comprises a primary coil and a secondary coil, and wherein said electronic circuit is operative to pass an electric current through said primary coil and to detect changes in an electric current induced in a said secondary coil caused by a movement of the projectile past said secondary coil.

10. The safety device of claim 6, wherein said metal detector includes a permanent magnet and a coil of wire windings surrounding the barrel, and wherein said electronic circuit is operative to detect when a metal projectile passes through the barrel at the location of the wire windings, a resulting fluctuation in magnetic flux and current indicating that a metal projectile has transited through the barrel.

11. The safety device of claim 1, wherein said sensor includes a thermal sensor and said electronic circuit is operative to detect changes in temperature caused by hot propulsive gases produced by the projectile as it is launched from said barrel.

12. The safety device of claim 11, wherein said thermal sensor is configured for mounting on the mortar barrel adjacent said open end of said barrel.

13. The safety device of claim 1, wherein said sensor includes a radiation emitter and a radiation sensor disposed on opposite sides of said barrel and wherein said electronic circuit is operative to detect changes in radiation received by said radiation sensor caused by a movement of the projectile between said emitter and said sensor.

14. The safety device of claim 13, wherein said emitter and said sensor are configured for mounting on the mortar barrel adjacent said open end of said barrel.

15. The safety device of claim 13, wherein said radiation is visible light.

16. The safety device of claim 13, wherein said radiation is ultraviolet light.

17. The safety device of claim 13, wherein said emitter is a laser.

18. The safety device of claim 1, wherein said sensor includes a radiation detector and wherein said electronic circuit is operative to detect changes in radiation received by said radiation sensor from a pyrotechnic propellant of the projectile.

19. The safety device of claim 18, wherein said radiation detector is configured for mounting on the mortar barrel adjacent said open end of said barrel.

20. The safety device of claim 18, wherein said radiation is visible light.

21. The safety device of claim 18, wherein said radiation is ultraviolet light.

22. The safety device of claim 18, wherein said radiation is in the thermal radiation band.

23. The safety device of claim 1, further comprising a linear accelerometer configured for mounting on the mortar barrel, and a second electronic circuit, coupled to said accelerometer, for detecting changes in acceleration caused by the launch of the projectile from the barrel, thereby to determine the instant of launch.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a representational diagram of a mortar illustrating the double-loading hazard addressed by the present invention.

(2) FIGS. 2A and 2B are perspective views of a mortar showing an externally mounted/retrofitted metal detector type device at two different locations on the mortar barrel.

(3) FIGS. 3A and 3B are perspective views of a mortar showing a radiation sensor type device (FIG. 3b) located at an upper, open end of the barrel.

(4) FIG. 4A shows two schematic diagrams of a dual-coil magnetic detector type device with an adjacent projectile in different positions; FIG. 4B illustrates a frequency change due to passage of the projectile.

(5) FIG. 5 is a representational diagram showing the magnetic field lines associated with metal body mortars with a dual-array magnetic detector device.

(6) FIG. 6 is a representational diagram showing a mortar projectile passing through a mortar barrel with a magnet and coil winding configuration.

(7) FIG. 7 is a detailed representational diagram of a metal detector type device with a permanent magnet and a coil winding.

(8) FIG. 8 is a cut-away view of a mortar barrel and a projectile, illustrating how magnetic fields fluctuate when the projectile moves from one to the next of three successive positions.

(9) FIG. 9 is a representational diagram showing a projectile in a mortar barrel with an adjacent permanent magnet and a coil winding configuration of the type shown in FIG. 7.

(10) FIG. 10 is an FEM Mesh diagram of a mortar barrel with the magnet and coil configuration shown in FIGS. 7 and 9, illustrating the magnetic flux/field strength surrounding the projectile as it passes the magnet and coil.

(11) FIGS. 11A, 11B, 12A, 12B, 13A, 13B, 14A, 14B and 15 are representational diagrams illustrating the magnetic flux/field strength surrounding the projectile in a mortar barrel as it passes the magnet and coil configuration of FIG. 9 at successive points in time.

(12) FIG. 16 is a perspective view of a projectile detector device according to the invention, mounted on the mortar with an audible and visual warning alarm.

(13) FIGS. 17A and 17B are close-up and distant perspective views, respectively, illustrating a projectile detector device according to the invention, mounted on the muzzle break with an audible and visual alarm.

(14) FIG. 18 is a voltage/time diagram illustrating the voltage induced in the winding coil of the magnet/coil configuration of FIG. 9, with a projectile falling in the mortar tube (pre-setback) with a velocity of 3.13 m/sec.

(15) FIG. 19 is a magnetic flux/time diagram illustrating the flux induced in the winding coil of the magnet/coil configuration of FIG. 9 by traverse of a projectile in the mortar barrel.

(16) FIG. 20 is a voltage/time diagram illustrating the voltage induced in the winding coil of the magnet/coil configuration of FIG. 9, with a projectile under launch conditions traversing the mortar barrel at a velocity of 220 m/sec.

(17) FIG. 21 shows the mortar safety device according to the present invention comprising a metal sensor, an associated electronic circuit and an audible and/or visual warning device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(18) The preferred embodiments of the present invention will now be described with reference to FIGS. 1-21 of the drawings. Identical elements in the various figures are designated with the same reference numerals.

(19) FIG. 1 illustrates the problem to which the present invention is addressed. This diagram shows how a mortar is subject to a double projectile feed creating a detonation hazard. When a projectile is inserted in a mortar at the upper, open end of the barrel, drops down to the lower, breech end where it is ignited, either right away by its contact with a firing pin at the breech end or on demand in response to a trigger pull. If, due to a hang-fire or due to confusion during firing, a second projectile is inserted before the first projectile is launched, the first projectile will collide with the second, causing an explosive hazard that can result in injury or death of the attendant mortar men.

(20) FIG. 8 illustrates an externally mounted/retrofitted metal detector mounted on a mortar barrel approximately midway between the open, upper end and the lower, breech end mounted on the breech block. FIG. 5 shows two metal detector devices mounted on the mortar barrel near each end. The metal detectors include a sensor for sensing the metal jacket of a mortar projectile upon its insertion in the barrel and an electronic circuit, coupled to the sensor, for detecting movement of the mortar projectile past the sensor, thereby to detect the presence of the projectile in the barrel.

(21) FIG. 21 depicts a radiation sensor-type device on the muzzle of a mortar barrel (with a sensor not shown inside the muzzle break). The radiation sensor detects radiation (visible light, heat or ultraviolet) emanating from the base of the projectile as it is launched by the pyrotechnic propellant. FIG. 5 shows a radiation emitter and sensor located at the upper end of the barrel with a second metal detector positioned lower down on the barrel. Radiation produced by the emitter, which is preferably a laser, is continuously sensed by the radiation sensor unless and until it is interrupted or blocked by the passage of a projectile between the emitter and sensor.

(22) FIG. 5 illustrates a projectile passing through two wiring coils resulting in both a voltage and a frequency change that is sensed by an electronic circuit (not shown). One wiring coil has a voltage applied, creating a magnetic field, and the second coil encounters a fluctuation in frequency when the projectile passes between the coils, as is illustrated in FIG. 4B.

(23) FIG. 5 shows a dual-sensor design with the sensors located near the upper and lower ends of a mortar barrel. The diagram illustrates magnetic field lines associated with a metal jacket mortar projectile.

(24) FIG. 6 depicts a projectile entering and exiting a mortar barrel with a toroidal permanent magnet and a coil wiring.

(25) FIG. 7 is a representational diagram of a sensor device with a permanent magnet and coil winding surrounding a mortar barrel.

(26) FIG. 8 shows the sensor device of FIG. 7, illustrating how the magnetic field fluctuates when a projectile moves past the sensor inside the mortar barrel.

(27) FIG. 9 shows a mortar projectile, a permanent magnet and a coil winding surrounding a mortar barrel, forming the sensing device of FIG. 7. This configuration is used in the FEM Mesh illustration of FIG. 10 and the illustrations of field strength (field fluctuations) depicted in FIGS. 11-15.

(28) FIG. 10 shows an electromagnetic analysis FEM Mesh with a projectile in a mortar barrel shown in cross section.

(29) FIGS. 11-15 depict the magnetic flux adjacent one side of a mortar barrel produced by the sensor device of FIG. 7 having a permanent magnet and coil winding surrounding the barrel. These figures show the changes in magnetic flux at successive points in time as a projectile moves through the barrel past the magnet and coil.

(30) FIG. 16 shows a mortar safety device with an audible and visual warning according to the present invention.

(31) FIGS. 17A and 17B show a muzzle mounted safety device according to the present invention.

(32) FIG. 18 is a voltage/time diagram of the signal produced by the mortar safety device of FIG. 7 as a projectile is dropped down a mortar barrel (pre-setback) and passes the magnet and coil sensor with a velocity of 3.13 meters per second.

(33) FIG. 9 shows the flux linkage (W) produced by the mortar safety device of FIG. 7 versus projectile position (mm) as a projectile traverses the mortar barrel.

(34) FIG. 20 is a voltage/time diagram of the signal produced by the mortar safety device of FIG. 7 as the projectile passes the magnet and coil surrounding the barrel at 220 meters per second prior to exiting the mortar barrel.

(35) FIG. 21 shows the mortar safety device according to the invention comprising a metal sensor 16, an associated electronic circuit 7 and an audible and/or visual warning device 15. The metal sensor shown in this case comprises a single coil winding 8. Alternatively, the metal sensor may include both a primary coil and secondary coil as shown in FIG. 4a.

(36) The mortar barrel 1 is provided with a breechblock 2 carrying a firing pin 3 to ignite the propellant in the projectile 5. When the projectile 5 is dropped into the open, upper end of the barrel 1 and its igniter contacts the firing pin 3 and, upon firing, ignites the propellant.

(37) A driver 12 in the electronic circuit 7 passes current through the coil winding 8 and senses fluctuations in the signal caused by the passage of the projectile as it leaves the barrel. A microprocessor 14 keeps track of the entry and exit of projectiles to and from the mortar barrel and causes the warning device 15 to sound the alarm if a projectile remains in the barrel longer than expected.

(38) An acceleration sensor 4 is provided to determine the moment of launch of each projectile. This sensor is also connected to the electronic circuit 7 through a conductor 6. The circuit 7 includes an input amplifier 9, an analog-to-digital converter 10 and a digital frequency filter 11, in turn connected to the microprocessor 14.

(39) The frequency range of the digital filter 11 is selected such that only those frequency portions of the measuring signal are passed which are characteristic of the launch of a projectile. The digital signal values obtained at the output of the frequency filter 11 are thereafter passed to the microprocessor 14 which measures the time between the launch of the projectile and its exit from the mortar barrel (as sensed by the metal detector 15) and computes the exit velocity of the projectile.

(40) There has thus been shown and described a novel mortar safety device which fulfills all the objects and advantages sought therefor. Many changes, modifications, variations and other uses and applications of the subject invention will, however, become apparent to those skilled in the art after considering this specification and the accompanying drawings which disclose the preferred embodiments thereof. All such changes, modifications, variations and other uses and applications which do not depart from the spirit and scope of the invention are deemed to be covered by the invention, which is to be limited only by the claims which follow.