Patent Description:
Tracers are projectiles that, when fired, provide a visible trajectory to enable the flight path of the projectile to be determined. The visible trajectory thus enables a user to visualise the path of the projectile, and to make ballistic alterations so as to correct the flight path and thus ultimately the end impact point of the projectile. A tracer round will typically comprise a pyrotechnic composition that is ignited when the round is fired. The composition is such that the visible trajectory can be seen by the naked eye in daylight as well as night-time.

<CIT> discloses an electronic tracer munition.

<CIT> discloses a tracer set for tracer ammunition that can be fired from a gun.

<CIT> discloses a propellant gas operation/initiation of a non-pyrotechnic projectile tracer.

According to an example, there is provided a non-incendiary tracer projectile structure housing an electrically powered illumination source, the tracer projectile structure comprising a jacket comprising a generally pointed forward end and a generally blunt rearward end defining a rear opening, an internal retaining structure disposed towards the rearward end of the jacket to support a protective window that is transparent to a selected electromagnetic wavelength, wherein a portion of the rearward end of the jacket tapers in a radially inward direction whereby to define a circumferential narrowing of the rear opening so configured as to mechanically protect the internal retaining structure. The internal retaining structure can comprise a circumferentially continuous collar on an internal surface of the jacket. The internal retaining structure can comprise multiple radially inwardly projecting protrusions.

The internal retaining structure can comprise a circumferential channel in an internal surface of the jacket. The internal retaining structure can comprise multiple circumferential channel portions in an internal surface of the jacket. The multiple circumferential channel portions can be arranged in the same plane.

In an example, the non-incendiary tracer projectile structure can comprise a second internal retaining structure disposed towards the rearward end of the jacket, the second internal retaining structure being axially displaced from the internal retaining structure whereby to define a channel to receive the protective window. The second internal retaining structure can comprise a circumferentially continuous collar on an internal surface of the jacket. The second internal retaining structure can comprise multiple radially inwardly projecting protrusions. The second internal retaining structure can comprise a circumferential channel in an internal surface of the jacket. The second internal retaining structure can comprise multiple circumferential channel portions in an internal surface of the jacket. The multiple circumferential channel portions can be arranged in the same plane. The second internal retaining structure can be displaced, in an axial direction, from the internal retaining structure towards the forward end of the jacket. The second internal retaining structure can be displaced, in an axial direction, from the internal retaining structure towards the rear opening. The internal retaining structure can be disposed on the portion of the rearward end of the jacket. The internal retaining structure can be disposed above, in an axial direction, the portion of the rearward end of the jacket. The second internal retaining structure can be disposed on the portion of the rearward end of the jacket.

According to an example, there is provided a tracer projectile comprising a non-incendiary tracer projectile structure as provided herein, in which the non-incendiary tracer projectile structure is partially provided in a cartridge configured to store a pyrotechnic composition.

Embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which <FIG> are schematic representations of a non-incendiary tracer projectile structure according to examples.

Example embodiments are described below in sufficient detail to enable those of ordinary skill in the art to embody and implement the systems and processes herein described.

Accordingly, while embodiments can be modified in various ways and take on various alternative forms, specific embodiments thereof are shown in the drawings and described in detail below as examples. There is no intent to limit to the particular forms disclosed. On the contrary, all modifications, equivalents, and alternatives falling within the scope of the appended claims should be included. Elements of the example embodiments are consistently denoted by the same reference numerals throughout the drawings and detailed description where appropriate.

The use of pyrotechnic compositions in incendiary tracers means that the location of the shooter can easily be determined by simple visual inspection of the starting point of the visible path that has been caused by ignition of the pyrotechnic agent in question. This can be detrimental to a user if there are hostile observers in the vicinity. Furthermore, since the pyrotechnic composition is gradually exhausted as the tracer is in flight, the trajectory will alter in a manner that is different to that of non-tracer projectiles. The reliability of pyrotechnic tracers can be lowered due to tolerances and environmental factors when creating/processing pyrotechnic chemical ingredients during manufacture, and also when stored and operated in environments with higher humidity (i.e. delayed chemical reaction or in some cases none at all when fired). Furthermore, use of pyrotechnic tracers in hot operational environments can create unintentional fires, causing collateral damage.

Non-incendiary tracers can use a rearwardly directed illumination source that is configured to emit light as the tracer is in flight. The extreme conditions present at the point that the tracer is fired mean that enormous stresses are placed on the light source and associated electronics and power source. There is also an increased risk of failure because exhaust gases present at the point of firing can exert massive pressures on the part of the tracer housing the light source.

According to an example, there is provided a non-incendiary tracer projectile structure housing an electrically powered illumination source. The tracer projectile structure comprises a jacket comprising a generally pointed forward end and a generally blunt rearward end defining a rear opening. The rear opening can define an aperture which enables the illumination source to emit light from the structure. In an example, an internal retaining structure is disposed towards the rearward end of the jacket to support a protective window that is transparent to a selected electromagnetic wavelength. That is, a protective window can be provided in or near the aperture. The window can be transparent to a selected wavelength that corresponds to the wavelength of light emitted by the illumination source. For example, the illumination source may be configured to emit in the infra-red region of the EM spectrum. Accordingly, a material for the window can be selected to enable transmission of infra-red at the selected wavelength. The material may substantially block (that is, not transmit) other wavelengths, such as those in the visible region of the EM spectrum for example. A portion of the rearward end of the jacket tapers in a radially inward direction whereby to define a circumferential narrowing of the rear opening so configured as to mechanically protect the internal retaining structure.

<FIG> is a schematic representation of a non-incendiary tracer projectile structure according to an example. In the example of <FIG>, the comprises a jacket <NUM> comprising a generally pointed forward end <NUM> and a generally blunt rearward end <NUM>. As noted above, the rearward end <NUM> defines a rear opening <NUM>. An internal retaining structure <NUM> is disposed towards the rearward end <NUM> of the jacket <NUM> to support a protective window <NUM> that is transparent to a selected electromagnetic wavelength. A portion <NUM> of the rearward end <NUM> of the jacket <NUM> tapers in a radially inward direction (D) whereby to define a circumferential narrowing of the rear opening <NUM> so configured as to mechanically protect the internal retaining bead <NUM>. In an example, the protective window <NUM> may comprise Polycarbonate, Sapphire, Fused Quartz, Laminated Toughened Glass.

<FIG> is a schematic representation of a non-incendiary tracer projectile structure according to an example. In the example of <FIG>, the structure as described with reference to <FIG> is shown in combination with a cartridge <NUM>. The cartridge is used to house a propellant and a primer that are used to eject the tracer projectile structure from a firing apparatus (such as a gun for example). The cartridge <NUM> does not form part of the present projectile structure but is described with reference to <FIG> in order to explain a function of the circumferential narrowing of the rear opening <NUM>. During manufacture, the bottom cartridge <NUM> of the tracer (encompassing the propellant and primer) covers the majority of the tracer up to approximately the horizontal line <NUM> at the base of the nose <NUM>. During firing, the cartridge <NUM> will be expelled, leaving the tracer and nothing obstructing the window <NUM> during flight. In combination, the tracer projectile structure and cartridge form a tracer projectile.

The circumferential narrowing <NUM> of the rear opening <NUM> forms a 'boat-tail' feature. Exhaust gases that are produced as a by-product of the firing of a tracer are produced as the primer ignites the propellant. That is, as the propellant burns it generates gases - the sudden, high pressure of this gas that is produced ejects the tracer projectile from the end <NUM> of the cartridge <NUM>. It is forced down e.g. the barrel of the firing apparatus at high speed (of the order of several hundred m/s). The cartridge <NUM> remains in the firing apparatus for ejection. The boat-tail feature <NUM> of the tracer projectile structure protects the internal retaining structure <NUM>, along with the window <NUM> and any components in the internal section <NUM> of the jacket <NUM> from the action of the exhaust gases. It also protects any sealing mechanism used in conjunction with the internal retaining structure <NUM>. For example, adhesive may be used to seal the window to the internal retaining structure <NUM>. Such a seal may fail under normal circumstances as a result of the action of the exhaust gases. The boat-tail feature provides protection by deflecting a proportion of the exhaust gases towards the outside surface <NUM> of the projectile structure. For example, with reference to <FIG>, exhaust gases moving in direction E are deflected around the boat-tail feature of the structure towards a region defined by the outer surface <NUM> of the rearward end <NUM> of the structure and the internal surface <NUM> of the cartridge <NUM>. As the pressure increases as a result of the buildup in the amount of gas produced by the propellant, the frangible connection <NUM> between cartridge and the projectile structure is broken and the tracer is ejected. The continuing action of the exhaust gas as the tracer is in an ejection phase, and specifically its effect on the retaining structure, is mitigated by the boat-tail feature as the tracer is ejected from the firing apparatus.

<FIG> is a schematic representation of a non-incendiary tracer projectile structure according to an example. In the example of <FIG>, an internal retaining structure <NUM> is depicted in greater detail in a side on cut away view. In the example of <FIG>, the retaining structure <NUM> comprises a circumferentially continuous collar <NUM> on an internal surface <NUM> of the jacket <NUM>. The window <NUM> can be provided on the collar, and a seal <NUM> may be provided to adhere/seal the window to an inner surface of the jacket <NUM>. In the example of <FIG>, the seal <NUM> is provided above the window <NUM>, but may be provided below such as at the interface between the window I I I and the retaining collar <NUM>, or in both locations.

<FIG> is a schematic representation of a non-incendiary tracer projectile structure according to an example. In the example of <FIG>, an internal retaining structure <NUM> is depicted in greater detail in plan view. In the example of <FIG>, the retaining structure <NUM> comprises multiple radially inwardly projecting protrusions <NUM>. The window <NUM> can be provided on the protrusions <NUM>, and a seal <NUM> may be provided to adhere/seal the window to an inner surface of the jacket <NUM>.

<FIG> is a schematic representation of a non-incendiary tracer projectile structure according to an example. In the example of <FIG>, an internal retaining structure <NUM> is depicted in greater detail in a cut away side view. In the example of <FIG>, the retaining structure <NUM> comprises a circumferential channel <NUM> in an internal surface <NUM> of the jacket <NUM>. The window <NUM> can be provided in the channel <NUM>, and a seal <NUM> (or seals) may be provided to adhere/seal the window to an inner surface of the jacket <NUM>.

<FIG> is a schematic representation of a non-incendiary tracer projectile structure according to an example. In the example of <FIG>, the internal retaining structure comprises multiple circumferential channel portions <NUM> in an internal surface of the jacket. The portions <NUM> may be arranged in the same plane or in different planes. That is, multiple circumferential rows of channels may be provided, each row being offset, in an axial direction, from one another. The window may have multiple circumferential protrusions arranged to complement the multiple channels. That is, the protrusions of the window may be so arranged as to engage into channels in the jacket whereby to enable the window to be fixedly mounted within the jacket.

According to an example, the non-incendiary tracer projectile structure can further comprise a second internal retaining structure disposed towards the rearward end of the jacket.

<FIG> is a schematic representation of a non-incendiary tracer projectile structure according to an example. In the example of <FIG>, the second internal retaining structure <NUM> is axially displaced from the internal retaining structure <NUM> whereby to define a channel <NUM> to receive the protective window. The channel in the example of <FIG> is defined by way of the retaining structures rather than being provided within the inner wall of the jacket as in the example of <FIG> for example. The second internal retaining structure <NUM> may comprise a circumferentially continuous collar on an internal surface of the jacket, or may be composed of multiple radially inwardly projecting protrusions, similarly to other examples described above. Alternatively, the second internal retaining structure <NUM> may comprise a circumferential channel in an internal surface of the jacket, or multiple circumferential channel portions in an internal surface of the jacket. The multiple circumferential channel portions can be arranged in the same plane such that they form an annular band of channel portions, or in different planes (in an axial direction) from one another, thereby forming more than one annular band of channel portions.

In an example, the second internal retaining structure may be displaced, in an axial direction, relative to the internal retaining structure towards the forward or rearward end of the jacket, that is away from or towards the rear opening. The internal retaining structure can be disposed on the portion of the rearward end of the jacket. That is, the internal retaining structure can be disposed on the portion of the jacket that narrows to form the boat-tail feature. Alternatively, the internal retaining structure can be disposed above, in an axial direction, that (narrowing) portion of the rearward end of the jacket. Similarly, the second internal retaining structure can be disposed on the narrowing portion of the rearward end of the jacket.

Claim 1:
A non-incendiary tracer projectile structure housing an electrically powered illumination source, the tracer projectile structure comprising:
a jacket (<NUM>) comprising a generally pointed forward end (<NUM>) and a generally blunt rearward end (<NUM>) defining a rear opening (<NUM>);
an internal retaining structure (<NUM>) disposed towards the rearward end (<NUM>) of the jacket (<NUM>) to support a protective window (<NUM>) that is transparent to a selected electromagnetic wavelength, wherein a portion (<NUM>) of the rearward end (<NUM>) of the jacket (<NUM>) tapers in a radially inward direction (D) whereby to define a circumferential narrowing of the rear opening (<NUM>) so configured as to mechanically protect the internal retaining structure (<NUM>).