Description Title of the invention: Device for controlling the positioning of a projectile in a tube of a weapon and control method implementing such a device.
The technical field of the invention is that of devices for controlling the positioning of a projectile in the tube of a weapon.
In large caliber weapon systems (caliber greater than
75mm), the projectile is usually separated from the propelling charge thereof.
During loading, the projectile is first inserted into a chamber of the weapon and pushed to a cone called forcing cone which is a zone where the diameter of the chamber is reduced to the diameter of the tube.
The projectile is pushed until it is wedged at the forcing cone by the band thereof or a bourrelet of the body thereof, and it then closes the tube of the weapon in a sealed way at that zone.
Such sealing guarantees a nominal rise in pressure of the propellant firing gases behind the projectile and the immobilisation of the projectile in the weapon before firing.
A device for checking the presence of a projectile in a weapon is known from patent DE19737078, which device includes sonic sensors coupled to a sound source and which determines by comparison with a reference sound signature whether the weapon is loaded or not.
The device as described by said patent does not detect, however, whether the projectile is correctly loaded, i.e. correctly wedged or hooked into the forcing cone of the weapon.
However, it is essential to be able to check the guality of the attachment of the projectile in the forcing cone before starting firing.
Indeed, if the projectile would detach from the forcing cone, it would fall towards the chamber of the weapon, and all the more so when the weapon is aimed with a positive elevation.
As a result, the projectile might fall out of the weapon if the breech is open, or else fall on the propellant charge elements.
Even if the projectile does not detach but if the quality of the positioning is insufficient, leaks of propellant gas are to be feared due to a defect of sealing between the projectile and the tube.
All such events are highly detrimental to the safety of surrounding property and persons.
The invention proposes to solve the safety problem by providing a control of the quality of the positioning of the projectile in the forcing cone of the weapon.
The invention thus relates to a device for controlling the positioning of a projectile in a tube of a weapon including a forcing cone intended to wedge a projectile radially, the device including at least one sensor intended to be placed against the tube of the weapon, which sensor is connected to a computer intended to process a signal originating from the sensor (s), the device being characterised in that the sensor includes a set of piezoelectric elements generating ultrasound waves, which sensor is intended to be arranged so as to deliver at least one ultrasound wavefront that is directed radially towards the longitudinal axis of the weapon and that is centered longitudinally opposite the forcing cone, the sensor being chosen such that the wavefront can extend inside the tube of the weapon over a width greater than the width of the forcing cone, the sensor being also able to receive at least one reflected echo of the emitted wavefront and to transmit this echo to the computer as an electrical signal.
Advantageously, the device includes at least two sensors each oriented along directions radial to the tube of the weapon and which are perpendicular to each other.
The invention also relates to a method for controlling the positioning of a projectile in the tube of a weapon, which method implements a device according to one of the preceding features and characterised in that:
— the sensor emits at least one wavefront and receives at least one echo in return;
— the sensor transmits a signal representative of the echo to the computer;
— the computer analyzes the echo relative to a reference echo, then supplies information relative to the compliant or noncompliant positioning of the projectile.
Advantageously, the method can be activated following an information that the projectile has been positioned.
Advantageously, the method can be deactivated after firing, thus allowing verification that the projectile has been fired, or else after unloading of the projectile.
The invention will be better understood upon reading the following description, description made with reference to the enclosed drawings wherein:
[Fig. 1] shows a schematic longitudinal view of a device according to one embodiment of the invention.
[Fig. 21 shows a cross-sectional view of a device according to a variant of embodiment of the invention.
According to Figure 1, a device 1 for securing the loading of a weapon is attached to a tube of a weapon tube with a caliber greater than 75 mm.
The weapon tube 10 has a bore 11 which is separated into two parts, on the one hand a chamber 12 intended for receiving a projectile 100 and a propellant charge 101, and on the other hand, a rifled part 13 intended for imparting a gyroscopic movement to the projectile 100 fired by the tube 10.
The chamber 12 has an internal diameter D2 greater than the internal diameter D1 of the rifled part 13. The progressive connection of the two diameters D1 and D2 between the chamber 12 and the rifled part 13 takes place in a zone called a forcing cone 14.
The forcing cone 14 enables a band 102 of the projectile 100, situated between a base 103 and an ogive 104, to provide sealing against propellant gases coming from the initiation of the load 101.
The band 102 consists e.g. of a malleable metal alloy apt to be conformed by creep to the profile of the tube, in particular by occupying the grooves of the rifled part 13.
If the projectile does not include a band, it could include one or a plurality of bourrelets having satisfactory dimensional and material features for providing a sealing between the forcing cone and the projectile 100.
The device 1 according to one embodiment of the invention includes at least one sensor 2 of a particular type, called electro-magnetic-acoustic sensor, as described hereinafter.
Such type of sensor, which is commercially available, is able to emit first an ultrasound wavefront 20 (arrows in Figure 2) into a substrate (herein the weapon tube) onto which the sensor is attached.
Secondly, the sensor can receive and convert the waves reflected as echoes 21 by the substrate,
into an electric signal which can be analyzed by processing electronics (such as a computer 200). The sensor includes a set of piezoelectric elements 2b (generally several tens of elements) which are able to generate ultrasound waves 20 when they are controlled by an electrical signal and which conversely can also generate another electrical signal as a result of the prompting thereof by incident ultrasound waves.
In the present case, the sensor 2 is attached to the tube 10 opposite the forcing cone 14. An acoustic coupling medium 2a conducive to the propagation of the ultrasound waves 20,
such as e.g. grease, is placed between the tube 10 and the sensor 2 so as to provide a perfect acoustic connection.
The zone of the tube 10 wherein the wave and echo fronts 21 move is represented in Figures 1 and 2 by a grayed out zone 2c.
5 The sensor 2 is arranged in such a way that the waves 20 which it generates travel radially through the material of the tube 10 and the material of the band 102 if a projectile 100 is positioned, i.e. wedged into the forcing cone 14.
It should be noted that the greater the contact pressure between the band of the projectile and the tube, the better the propagation of waves between the two elements.
In the case where the projectile 100 is not positioned, or else when the wedging is not locally sealed, an air gap is present between the forcing cone 114 and the band 102. This air gap hinders the passage of the ultrasound 20 and in return modifies the echo 21 detected by the sensor 2.
The sensor 2 is electrically connected to a computer 200 to which it transmits a signal representative of the echo 21 detected by the sensor.
The computer 200 is able to interpret the nature of the echoes collected by the sensor 2. The computer 200 thereby compares the echo received with reference echoes which have been determined by experiment.
It is then possible to provide a user with information on the compliance of the positioning via an interface (interface not shown), such as a screen or indicator lights.
The positioning will be compliant if the sealing is satisfactory (no air gap or presence of an air gap the thickness of which is below a predefined threshold).
It will be noncompliant (sealing defect) if the echo corresponds to the presence of an air gap the thickness of which is above the predefined threshold.
It will also be noncompliant if the projectile is unhooked or if the echo corresponds to an absence of band.
The device 1 will provide a continuous monitoring of the state of the positioning. The monitoring will start with information on the positioning of the projectile 100, given e.g. by a fire-control of the weapon or by the system controlling the loading of the projectile. The monitoring could stop after firing, thereby making it possible to check that the projectile left, or the monitoring could be stopped after the possible unloading of projectile 100 in the chamber. In addition to the display of the information on noncompliancy, the detection of a noncompliant positioning could also command the prohibition of firing. The sensor 2 will be chosen so that the wavefronts 20 that the sensor emits and the echoes 21 the sensor receives cover a zone with width L1 greater than the width L2 of the forcing cone 14 and up to twice the width L2 of the cone 14. Such extended coverage makes it possible to take account of the dispersion of the longitudinal positioning of the projectile 100 in the tube 10. Such dispersion can result from wear of the forcing cone 14, from a variation in the positioning force of the projectile 100 or from dimensional variations of the band 102. Such sources of dispersion can obviously be cumulated, hence the importance of monitoring a zone of the tube which is larger than the forcing cone 14 but while remaining centered on the forcing cone 14. For even greater safety, it is preferable to use a plurality of sensors 2 oriented along directions radial to the tube 10 of the weapon and which are perpendicular to each other and perpendicular to the longitudinal axis X of the tube
10. The signals coming from the two sensors will be combined at the computer 200, the correct positioning being confirmed only if the two sensors provide an information of correct positioning.
It should be noted that the device according to the invention is non-intrusive with respect to the weapon since the sensors are positioned against the tube 10 without any machining being necessary.
The invention can be thus adapted to existing equipment without heavy modifications.