Patent Application
20110285088
This invention relates to a pyrotechnic cassette, in particular to a pyrotechnic cassette for a pyrotechnic shooting target.
One example of a traditional shooting target is a clay pigeon comprising a clay disc which shatters when hit by shot from a shotgun. However, it is sometimes difficult to discern whether a clay has been shot as the shattering is not particularly dramatic. Similarly when shooting stationary targets or targets on moving vehicles the indication that the target has been shot is not usually dramatic.
Accordingly, pyrotechnic shooting targets such as pyrotechnic clay pigeons have been proposed: in one example (WO/0235175) the clay pigeon is made from a disc shaped rigid plastic housing. The housing contains impact sensitive primers such as a mixture of red phosphorus and sodium chlorate as used in caps for cap guns, coated on a fibrous disc, and a pyrotechnic such as magnesium flash powder. The pyrotechnic can be made into a paste and pressed into the housing. One face of the disc shaped housing has an opening spanning most of its area. The opening is closed by a cardboard disc which is readily penetrated by shot.
Such a pyrotechnic clay pigeon is fired from a trap so that the face of the housing closed by the cardboard disc faces generally downward. Thus when hit, shot pierces the cardboard disc, travels through the pyrotechnic and impacts on the primer, so that the primer ignites and thereby ignites the pyrotechnic which explodes. The explosion of the pyrotechnic can produce a visible flash, a more prolonged burning, an audible noise or a combination of any of these.
A pyrotechnic clay pigeon as described above is disclosed in WO02/35175, from which it is clear that a clay pigeon need not be made of clay.
Use of pyrotechnic shooting targets such as the pyrotechnic clay pigeon of WO02/35175 has not become widespread owing to certain disadvantages or perceived disadvantages. In particular it is very difficult to provide a mixture of primer/pyrotechnic that will explode when shot but will not explode prematurely and it is not considered safe for the detonating primers to be in direct contact with the flash powder even when these are not in the same mixture. One embodiment of WO02/35175 shows a two-part design in which a release layer of double-sided adhesive tape is placed between the combustible material (i.e. the pyrotechnic) and the detonator, and the release layer is intended not to be removed until just prior to launching. However, there is still a period of time before the clay is shot, during which time the two layers are in direct contact, and during this time the clay undergoes the stresses of being launched from the trap, which can cause friction between the layers and lead to premature explosion, which is a serious safety risk. Also if the clay is not shot during flight it is liable to explode when it hits the ground.
Another very significant disadvantage with the pyrotechnic target of WO02/35175, is that it is intended to be shipped with the pyrotechnic and the primer in close proximity i.e. inside the housing beside each other, which is considered a safety risk, despite the possibility of the pyrotechnic and the primer not being in direct contact because of the release layer. In fact because of this disadvantage it is difficult to find shipping companies willing to transport the target.
It is an object of the invention to overcome one or more of the disadvantages mentioned above.
According to a first aspect of the invention, there is provided a cassette adapted to fit into a substantially rigid housing forming a shooting target; the cassette containing a pyrotechnic, and not containing ignition means.
By providing the pyrotechnic in a separate cassette, rather than pouring it into the housing of the shooting target, or making it into a paste and putting it in the housing, the cassettes can be shipped separately from the housing containing the ignition means and thus avoid the risk of accidental explosion during shipping. Furthermore, since the pyrotechnic is placed inside the housing within the cassette, the pyrotechnic will be separated from the ignition means by the wall of the cassette in use, only coming into contact with the primer when shot penetrates the cassette and impacts the ignition means.
A second aspect of the invention provides a cassette adapted to fit into a substantially rigid housing to form a shooting target; the cassette having an inner volume filled with (i) a pyrotechnic and optionally (ii) one or more non-shock-sensitive components only.
It is preferred that the inner volume is filled entirely with pyrotechnic, without any other components. However, provided they are not shock-sensitive (i.e. materials that do not decompose violently when struck or heated) other components may be used as filler, or to impart color to the explosion for example.
Preferably the cassette is readily penetrable by an inert projectile.
The fact that it is readily penetrable means that shot will easily pass through the cassette carrying enough momentum to set off an impact sensitive primer behind the cassette.
Preferably the cassette is made of thin card or paper.
Paper and card have the advantages of being readily available and readily penetrable by an inert projectile such as shot from a shotgun and combustible. The fact that the cassette is readily penetrable means that shot will easily pass through the cassette carrying enough momentum to set off an impact sensitive primer behind the cassette. The fact that paper is readily combustible will allow the pyrotechnic to easily burn through the cassette once ignited by the primer, and will minimise residue left in the housing.
Alternatively the cassette is made of metal foil such as aluminium foil.
Like paper and card, aluminium foil is readily penetrable by an inert projectile and readily available. However, metal foils are less combustible than paper, and in consequence it is thought that accidental ignition of a primer adjacent the cassette is less likely to set off the pyrotechnic because the ignition is less likely to perforate the foil.
Preferably the cassette is substantially disc shaped whereby it is adapted to fit inside an annular rim comprising part of the housing of the shooting target.
Users are used to shooting circular targets so an annular rim surrounding a circular target is familiar, furthermore where the target is a pyrotechnic clay pigeon, having a housing with an annular rim giving the clay pigeon good flying characteristics, therefore it is useful to have a clay pigeon of that shape, and it is useful for the cassette to be similar shaped so that it fits snugly within the housing.
Preferably the cassette has a radially outwardly extending flange arranged to overlap one end of the annular rim of the housing shooting target.
The flange overlapping the annular rim means allows the flange to be sandwiched between the rim and a lid holding the cassette in place.
Preferably the pyrotechnic comprises flash powder.
Flash powder is a mixture of a metal fuel and an oxidiser and when ignited produces a flash, a prolonged burning, a bang, or more than one of these.
Preferably the pyrotechnic comprises aluminium flash powder.
Aluminium flash powder uses aluminium as the metal fuel. The oxidiser can for example be potassium perchlorate and an exemplary composition is 70% aluminium powder and 30% potassium perchlorate.
Alternatively the pyrotechnic comprises black powder.
Black powder is a granular mixture of a nitrate (typically potassium nitrate) which supplies the reaction with oxygen, charcoal which provides carbon as fuel for the reaction and sulphur which is another fuel and serves a duel purpose, lowering the temperature of ignition and increasing the speed of combustion.
In another aspect of the invention there is provided a pyrotechnic shooting target comprising a substantially rigid housing containing a cassette of the type described above.
In a preferred pyrotechnic shooting target the housing further contains ignition means.
In a more preferred pyrotechnic shooting target the rigid housing comprises a tube closed at least one end.
In another preferred shooting target the cassette is spaced from the closed end of the tube by the ignition means.
This arrangement of layers means that an inert projectile, such as shot or a pellet, can penetrate the cassette, then impact on the ignition means and press the ignition means against the closed end of the rigid housing. This compressive force can ignite the ignition means and the flame can light the pyrotechnic through the perforated cassette
In a preferred pyrotechnic shooting target the ignition means comprises a disc shaped primer.
A disc shaped primer can fit neatly against the closed end of the tubular housing.
A preferred ignition means is a mixture of particulate red phosphorus and sodium chlorate.
It will of course be understood that a tube is not necessarily circular in cross section, but a circular cross section is preferred because of the familiarity to users and good flying characteristics described above in relation to the annular rim. The benefit to flying characteristics is in part due to the fact that clays are usually spun when released from the trap.
In yet another preferred pyrotechnic shooting target the housing further comprises a lid shaped to fit around the tube and at least partially close the open end of the tube.
The provision of a lid serves to keep the contents of the shooting target within the housing. This is particularly useful in the case of a moving target such as a clay pigeon or a target attached to a vehicle. However, it is not necessary that the lid remains in place when the contents explode. If the lid entirely closes the housing, it should be penetrable by an inert projectile so that the contents can be ignited.
However, in a preferred pyrotechnic shooting target the lid comprises an opening, whereby the pyrotechnic shooting target can be detonated by an inert projectile entering the housing through the opening, penetrating the cassette and impacting the ignition means causing the ignition means to ignite, thereby detonating the pyrotechnic.
In another aspect of the invention there is provided a kit of parts comprising a cassette of the type described, a rigid housing and ignition means.
In another aspect of the invention there is provided a movable target vehicle comprising a pyrotechnic shooting target as described above. Preferably, the vehicle is a radio controlled plane.
In yet another aspect of the invention there is provided a clay pigeon comprising a pyrotechnic shooting target as described above.
Certain non-limiting embodiments of the invention will be described in more detail below with reference to the accompanying drawings in which:
Referring to
The cassette 2 is located within a housing 6 which is in the shape of a tube closed at one end, having upstanding walls 8 at the periphery of a circular base 10. The housing is made of rigid plastic such as HDPE and is about 40 mm in diameter and 6 mm in height. The housing could be manufactured by injection moulding.
Ignition means in the form of disc 12 is provided in the housing 6 having a diameter slightly smaller than the inner diameter of the walls of the housing. The disc is made of two ply paper and contains a thin layer of particulate red phosphorus and sodium chlorate between the layers.
A plastic lid 14 made for example from HDPE is provided which is formed in the shape of a tube 16 of similar inner diameter to the outer diameter of the housing 10 with an inwardly extending flange 18 at the top thereof leaving an opening 20 over most of its outer face.
To assemble the pyrotechnic shooting target 1 the ignition means 12 is placed in the bottom of the housing 6 as shown and the cassette 2 is inserted above the ignition means 12. The lid 14 is then placed over the housing 6 to retain the contents of the housing 6. The lid should be an interference fit with the housing to avoid accidental detachment.
In use the assembled shooting target 1 can be hung in a shooting range such that the opening 20 faces the shooter. Thus when the shooting target 1 is shot, the projectile, such as shot enters the opening, penetrates the cassette 2 and impacts on the primer 12 causing it to ignite and set off the pyrotechnic 4. When the pyrotechnic is shot it emits a flash and a bang alerting the user that the shooting target has been shot.
In a second embodiment shown in
As an alternative to paper, the cassette 2 may be formed from foil such as aluminium foil.
The cassette 2 may also be formed from foil which is supported by a cardboard disc forming the upper circular end of the cylindrical cassette.
A cardboard disc may form the upper end of the cylindrical cassette 2 and extend radially beyond the tubular wall of the cassette 2 to form the flange 22.
The flash powder in the carrier could be replaced with black powder comprising 75% by weight potassium nitrate 15% by weight softwood charcoal and 10% by weight sulphur.
As yet another alternative to the pyrotechnic inside the cassette 2 may include magnesium flash powder instead of aluminium.
As an additional feature (not shown) the cassette 2 may be provided with dividers on its interior in the form of upwardly extending tubular walls separating the cassette 2 into compartments such as rings in order to avoid the powder being forced to the edges of the pyrotechnic shooting target 1 due to movement shaking the powder.
As an alternative to plastic the housing may be formed from metal for example aluminium.
According to another feature the housing 6 may be placed within a shell (not shown) in the shape of a traditional clay pigeon which can be made of clay. In this case the opening 20 in the shooting target 1 should be positioned downwardly so as to face the shooter when it is shot from a trap.
According to another feature, the shooting target 1 may be attached to a movable target vehicle, such as a radio controlled car, boat or plane and according to yet another feature the housing 6 may be formed as part of a movable target vehicle, for example as part of the underneath surface of the wing of a radio controlled plane.
