A pyrotechnic device

Abstract

A pyrotechnic device 100 comprises a housing 101 having a sidewall 110 that defines a cavity 105. The sidewall 110 comprises an upper end 111 and a lower end 112. A bottom wall 115 is arranged to clos

Description

Field of the Disclosure The present disclosure relates generally to a pyrotechnic device and a method of manufacturing a pyrotechnic device, and finds particular, although not exclusive, utility in providing a pyrotechnic device with improved stability and consistency with a reduced environmental impact. Background A pyrotechnic device typically includes a mixture of combustible materials and pyrotechnic stars. When the combustible material is ignited, the pyrotechnic stars are propelled from the device into the air and burn to produce colours and spark effects. One common application of pyrotechnic devices can be seen in the entertainment industry due to their ability to generate aesthetic displays of colours and light, thus contributing to the visual display at concerts, festivals, and theatrical events. Some pyrotechnic devices can reach an altitude ranging from 15 - 100 m. The shape / pattern formed by the pyrotechnic stars ejected from the housing of a pyrotechnic device is partially determined by their configuration within the housing prior to ignition. For example, when pyrotechnic stars are arranged in a circular pattern, they may be propelled radially to form a circle in the sky. If the pyrotechnic stars are packed in a specific configuration, the pyrotechnic device may produce any desired effect such as a “smiley face” or a “flower” when it explodes. In other configurations, the pyrotechnic stars are configured to produce a burst effect. Typical pyrotechnic devices suffer from significant inconsistencies, leading to performance issues that impact the visual display. For example, two of the same pyrotechnic devices may launch their pyrotechnic stars to varying heights, creating an unpredictable visual effect. The spread of pyrotechnic stars can often be inconsistent as the pyrotechnic stars can deviate significantly from the intended distribution, affecting the overall symmetry of the display. Additionally, some pyrotechnic stars may fail to ignite or burn completely, leaving unburned particles and diminishing the intended effect. Many factors contribute to the inconsistencies in the height and the spread of the pyrotechnic stars. The venting of gases upon ignition of the combustible material often leads to an unstable pressure change within the housing of the pyrotechnic device, which may lead to the device failing to reach the intended target altitude. If the pressure within the housing exceeds a threshold limit, components such as a housing of the device may be damaged which may pose a safety risk to the audience, performers or others in the surrounding environment. Accordingly, it is desirable to provide a pyrotechnic device to alleviate these problems with existing pyrotechnic devices. Aspects of the present disclosure provide such a pyrotechnic device. Summary According to a first aspect, there is provided a pyrotechnic device comprising: a housing comprising: a sidewall that defines a cavity, wherein the sidewall comprises an upper end and a lower end; and a bottom wall arranged to close the lower end of the sidewall; wherein a width of an upper end of the cavity is larger than a width of a lower end of the cavity; and wherein the sidewall and the bottom wall are monolithic; and an igniter, an explosive, and pyrotechnic stars arranged within the cavity. In this way, the sidewall and the bottom wall are configured as a one-piece housing to accommodate the igniter, the explosive, and pyrotechnic stars. As the sidewall and the bottom wall form a monolithic housing, there is no join between the sidewall and the bottom wall. The join between components of the housing of prior known devices has been found to be a significant source of inconsistency as the join may fail upon ignition of the device, allowing expanding gases to escape. Providing a one-piece pyrotechnic device removes joins between housing components and eliminates the possible areas for expanding gasses to vent undesirably. An internal wall of the housing may provide a smooth, continuous surface to achieve more consistent laminar central gas flow from the point of ignition to the top of the housing. The internal wall may be the wall facing the cavity. The width of an upper end of the cavity is larger than a width of a lower end of the cavity. The upper end of the cavity may be adjacent to the upper end of the sidewall, and the lower end of cavity may be adjacent to the lower end of the sidewall. Arranging the housing in this way has been found to significantly increase the consistency of operation of the pyrotechnic device. The increasing cross-sectional area of the cavity may act to stabilise the flow of gases along the cavity by reducing turbulence in the flow. A diameter of the cavity at the upper end of the sidewall may be in the range of 27.0 - 35.0 mm and a diameter of the cavity at the lower end of the sidewall may be in the range of 20.0 - 28.0 mm. In this way, a pyrotechnic device suitable in size for a concert or other show may be provided. The internal width of the housing may enable sufficient space to accommodate the pyrotechnic stars to lie in a single layer, reducing the variation in the pyrotechnic stars pattern that is caused by their arrangement and stacking within the housing prior to ignition. Alternatively, the pyrotechnic stars may be stacked in more than one layer or may be provided loosely in the cavity. The pyrotechnic device may be a stage mine. A stage mine may produce a shower of pyrotechnic stars, creating a directional explosion of colour and other visual effects. The housing may be a container that is configured to provide space for storing contents. The housing being monolithic may mean that the housing is formed of a single continuous piece. A monolithic housing may be one-piece, meaning the housing is made or consists of a single continuous structure. The housing may be injection moulded. A one-piece injection moulded housing has been found to reduce the total injection moulding steps by 50% compared to previously known stage mines, thereby reducing the manufacturing time and energy consumption. The igniter may be a device used to produce a spark, a flame, heat, or otherwise be able to ignite the explosive. The igniter may be a device used to initiate combustion. Pyrotechnic stars may be a mixture of chemicals and materials that produce colours and sparks when ignited. Pyrotechnic stars may comprise metal salts, oxidisers, and / or fuel. Pyrotechnic stars may burn in mid-air or otherwise outside of the housing. The explosive may be a chemical compound or mixture that is intended to produce a relatively large amount of gas rapidly upon combustion. An explosive may be a propellant that is configured to propel the contents situated within the cavity out of the housing. A rate of change in the width of the cavity from the lower end to the upper end may be constant. As such, a width of the cavity may increase at a constant rate from the lower end of the cavity to the upper end of the cavity. A rate of change in the width of the sidewall from the lower end to the upper end may be constant. The sidewall may have a constant wall thickness such that the width of the cavity changes according to the change in width of the sidewall. The sidewall may be angled relative to a longitudinal axis of the housing at an angle in the range of 0.1 - 0.3 degrees. The sidewall may be angled relative to the longitudinal axis of the housing at an angle of 0.2 degrees or approximately 0.2 degrees. The longitudinal axis of the housing may be an axis perpendicular to the bottom wall and pass through a centre of the bottom wall. The above-mentioned angle has been found to provide a significant improvement in consistency. The housing may further comprise an opening at the upper end. The opening may be an aperture with the same diameter as the cavity at the upper end of the sidewall. The diameter of the opening may be in the range of 27 - 35 mm. In this way, the components situated within the housing may be ejected outwards from the opening of the housing. The opening at the top of the housing may ensure that the pyrotechnic stars are propelled upwards as desired. The opening may be sized to allow for the rapid expansion of gases, thus facilitating the ejection of the components from within the housing. The pyrotechnic device may further comprise a cap configured to cover the opening. The cap may seal the opening to prevent environmental damage related to moisture ingress and may help to prevent the components arranged within the housing being moved or tampered with. The cap may protect the components situated within the housing from weather conditions, as humidity and heat may affect their performance. The cap may improve the operational lifetime of the pyrotechnic device across all environments, contributing to a net reduction in environmental waste. The cap may protect the structural integrity of the device. The cap may comprise plastic materials. The cap may comprise waterproof materials. The cap may comprise a sticker with a sticky surface configured to attach the sticker to the upper end of the housing and cover the opening. The cap may increase the pressure within the pyrotechnic device during operation, thereby helping to achieve maximum performance. The sidewall may further comprise at least one aperture. The at least one aperture may be located proximate to the lower end of the sidewall. The at least one aperture may be configured to accommodate a portion of the igniter. The igniter may comprise at least one cable and an igniter head. The igniter head may be at least partially retained within the aperture. Alternatively or additionally, the at least one cable of the igniter may be arranged to pass through the at least one aperture. The at least one aperture may be covered. An adhesive tape may be provided to cover the aperture. The adhesive tape may be reinforced. The adhesive tape may secure the igniter in the desired position within the aperture. The adhesive tape may also seal the aperture, preventing humidity or other environmental factors from degrading the components inside the housing, thereby extending the operational lifetime of the pyrotechnic device. The at least one aperture may be rectangular or substantially rectangular in shape. The at least one aperture may have a rounded rectangular shape, wherein the shape is rectangular with rounded corners. The at least one aperture may be substantially circular in shape. The at least one aperture may be of any desired geometrical shape. In this way, the at least one aperture may be provided consistently in each pyrotechnic device and may allow for a consistent venting of expanding gases through the aperture following ignition of the explosive. This arrangement may optimise pressure control, thereby ensuring uniform launch height and proper pyrotechnic star dispersion. The igniter may be positioned proximate to the lower end of the sidewall. The explosive may be positioned between the igniter and the pyrotechnic stars. In this way, the igniter may ignite the explosive which may propel the pyrotechnic stars out of the housing. The pyrotechnic device may further comprise a flash paper dish associated with the explosive. The flash paper dish may be a highly flammable paper. The flash paper dish may ignite and burn upon contact with heat or spark, producing little smoke and / or particulates. The flash paper dish associated with the explosive may be positioned between the explosive and the pyrotechnic stars. In this way, the flash paper dish may be positioned on top of the explosive, such as a black powder, and may provide a consistent supporting surface for the pyrotechnic stars so that the pyrotechnic stars may be positioned accurately and consistently during the manufacture of the pyrotechnic device. The flash paper dish may aid in the ignition of pyrotechnic stars, ensuring the pyrotechnic stars are burned properly. The pyrotechnic device may further comprise a mine sponge. The mine sponge may be a sponge configured to fit within the cavity of the housing of a pyrotechnic device. The mine sponge may enable controlled dispersion of the pyrotechnic stars. The mine sponge may enable a consistent degree of confinement of the combustible materials. The pyrotechnic stars may be positioned between the mine sponge and the explosive. The mine sponge may act as a separator and may help to hold the components of the pyrotechnic device in their desired position within the cavity. As such, the need for conventional confinement means, such as saran or other polymer films, may be removed. The pyrotechnic device may further comprise a flash paper dish associated with the mine sponge. The mine sponge may be positioned between the flash paper dish associated with the mine sponge and the pyrotechnic stars. In this way, the flash paper dish associated with the mine sponge may help to secure and burn the mine sponge positioned below, thereby improving consistency in the operation of the device. In some examples, the flash paper dish associated with the explosive and the flash paper dish associated with the mine sponge may be square pieces of flash paper. The flash paper dish associated with the explosive and the flash paper dish associated with the mine sponge may be of the same size. Any of the aforementioned features, individually or in combination, may contribute to a net reduction of explosive content, thereby reducing environmentally damaging smoke particles, pollutants and residues generated upon the ignition of the pyrotechnic device. The bottom wall may comprise a recess centrally located on a surface of the bottom wall facing the cavity. At least a portion of the igniter may be arranged within the recess. For example, the igniter head, or a portion of the igniter head, may be positioned within the recess. The recess may keep the igniter in the desired position within the cavity to maintain consistency, thereby preventing ignition failures and ensuring the igniter can reliably ignite the explosive to achieve complete combustion. The igniter may comprise an electric match. An electric match may be configured to ignite the explosive upon receiving an electronic signal. In this way, a user may control the ignition electronically and remotely. The electric match may allow the user to ignite the pyrotechnic device at a safe distance, minimising the risks of injury to the user. The electric match may allow the user to control the timing of the ignition in a precise way, for example with a computer program. A surface of the bottom wall opposite the cavity may comprise at least one indentation. The at least one indentation may be on a surface of the bottom wall that is spaced from the cavity. The bottom wall may have a substantially constant wall thickness. The at least one indentation may allow the bottom wall to be cured within a shorter timespan than an indentation-less bottom wall. The at least one indentation may enable the bottom wall to be cooled at a constant rate during moulding, thereby allowing the bottom wall to be fully cooled by the time it is removed from the mould. The bottom wall being fully cooled may prevent molten bottom wall material becoming deformed if it is taken out of the mould before the bottom wall is fully cured. This may ensure the walls of the housing are correctly shaped and uniform, allowing the housing to maintain its structural integrity under pressure, thereby preventing fracture in use. Each of the pyrotechnic stars may have a minimum dimension of at least 2 mm. Each of the pyrotechnic stars may have a maximum dimension of no more than 8 mm. Each of the pyrotechnic stars may be cylindrical. Each of the pyrotechnic stars may have a dimension of 3.5 x 6.0 mm. Each of the pyrotechnic stars may have a dimension of 4.0 x 4.0 mm. Each of the pyrotechnic stars may have a constant size and / or shape. Alternatively, one or some of the pyrotechnic stars may have a first shape and / or size different to another or other pyrotechnic stars. Consistently sized pyrotechnic stars may provide a consistent visual effect. Varied sizes of the pyrotechnic stars may produce a variety of visual effects to achieve an alternative pattern or visual effect. The explosive may comprise black powder. The explosive may comprise 4FA and / or 5FA black powder. In this way, the explosive may be sufficiently safe and stable whilst also allowing for a sufficiently consistent, quick and powerful explosion to propel the pyrotechnic stars. According to a second aspect, there is provided a method of manufacturing a pyrotechnic device, the method comprising: providing a housing, the housing comprising: a sidewall that defines a cavity, wherein the sidewall comprises an upper end and a lower end; and a bottom wall arranged to close the lower end of the sidewall; wherein a width of an upper end of the cavity is larger than a width of a lower end of the cavity; and wherein the sidewall and the bottom wall are monolithic; and providing an igniter, pyrotechnic stars, and an explosive within the cavity. In this way, a pyrotechnic device with a one-piece housing, such as the pyrotechnic device of the first aspect, may be manufactured. The method may provide a housing wherein a rate of change in the width of the cavity from the lower end to the upper end is constant. The upper end of the sidewall may be larger than the lower end of the sidewall. In this way, a pyrotechnic device with a one-piece inverted truncated cone shape may be manufactured. The method may further comprise moulding the housing as a single piece. In this way, a housing without joins or other potential weakened areas is provided. The method may further comprise forming the housing such that a diameter of the cavity at the upper end of the sidewall in the range of 27.0 - 35.0 mm, and a diameter of the cavity at the lower end of the sidewall in the range of 20.0 - 28.0 mm. In this way, a pyrotechnic device suitable in size for a concert or other show may be provided. The internal width of the housing may enable sufficient space to accommodate the pyrotechnic stars to lie in a single layer, reducing the variation in the pyrotechnic stars pattern that is caused by their arrangement and stacking within the housing prior to ignition. The housing may comprise an opening at the upper end of the sidewall. In this way, a pyrotechnic device with an opening may be manufactured. An opening may be an aperture with the same diameter as the cavity at the upper end of the sidewall. The diameter of the opening may be in the range of 27 - 35 mm. In this way, the components situated within the housing may be ejected outwards from the opening of the housing. The opening at the top of the housing may ensure that the pyrotechnic stars are propelled upwards as desired. The opening may be sized to allow for the rapid expansion of gases thus facilitating the ejection of the components from within the housing. The method may further comprise providing a cap to cover the opening. The cap may be configured to cover the opening. The cap may seal the opening to prevent environmental damage related to moisture ingress and may help to prevent the components arranged within the housing being moved or tampered with. The cap may protect the components situated within the housing from weather conditions, as humidity and heat may affect their performance. The cap may protect the structural integrity of the device. The cap may comprise plastic materials. The cap may comprise waterproof materials. The cap may comprise a sticker with a sticky surface configured to attach the sticker to the housing and cover the opening. The cap may increase the pressure within the pyrotechnic device during operation, thereby helping to achieve maximum performance. The method may further comprise providing at least one aperture in the sidewall to accommodate a portion of the igniter. The at least one aperture may be located proximate to the lower end of the sidewall. In this way, a pyrotechnic device with an aperture may be manufactured. The at least one aperture may be consistent and may allow for a consistent venting of expanding gases through the aperture following ignition. This may optimise pressure control, thereby ensuring uniform launch height and proper pyrotechnic star dispersion. The method may further comprise: positioning the igniter proximate to the bottom wall; positioning the explosive between the igniter and the pyrotechnic stars; positioning a first flash paper dish between the explosive and the pyrotechnic stars; positioning a mine sponge such that the pyrotechnic stars are between the mine sponge and the first flash paper dish, and positioning a second flash paper dish such that the mine sponge is between the second flash paper dish and the pyrotechnic stars. The first flash paper dish may provide a consistent supporting surface for the pyrotechnic stars so that the pyrotechnic stars may be positioned accurately and consistently during the manufacture of the pyrotechnic device. The mine sponge may enable controlled dispersion of the pyrotechnic stars. The mine sponge may enable a consistent degree of confinement of the combustible materials. The second flash paper dish may help to secure the mine sponge positioned below, thereby improving consistency in the operation of the device. In this way, a pyrotechnic device with consistent operations may be manufactured. The method may further comprise forming a recess centrally located on a surface of the bottom wall facing the cavity to receive the igniter; and forming at least one indentation on a surface of the bottom wall opposite the cavity, wherein the bottom wall has a substantially constant wall thickness. In this way, a pyrotechnic device with constant wall thickness may be manufactured. Any feature described with reference to the first aspect may be provided with the second aspect. Any feature described with reference to the second aspect may be provided with the first aspect. Brief Description of the Drawings Figure 1 is a schematic side cross-sectional view of a pyrotechnic device; Figure 2 is a first schematic side cross-sectional view of the housing of the pyrotechnic device of Figure 1; Figure 3 is a second schematic side cross-sectional view of the housing of the pyrotechnic device of Figure 1; Figure 4 is a schematic side view of the pyrotechnic device of Figure 1; and Figure 5 is a method diagram showing the steps of a pyrotechnic device manufacturing method. Throughout the drawings, identical reference characters and descriptions indicate similar, but not necessarily identical, elements. While the aspects described herein are susceptible to various modifications and alternative forms, specific examples have been shown in the drawings and will be described in detail herein. However, the scope of the present invention is not intended to be limited to the particular forms disclosed. Rather, the present disclosure covers all modifications, equivalents, and alternatives falling within the scope of the appended claims. Detailed Description The following detailed description presents various examples and, together with the drawings, serves to explain principles of the disclosure. However, the scope of the invention is not intended to be limited to the precise details of the examples, since variations will be apparent to a skilled person, and the scope is defined in the following set of claims. Terms for components used herein should be given a broad interpretation that also encompasses equivalent functions and features. In some cases, alternative terms for structural features may be provided but such terms are not intended to be exhaustive. Descriptive terms should also be given the broadest possible interpretation; e.g. the term "comprising" as used in this specification means "consisting at least in part of" such that interpreting each statement in this specification that includes the term "comprising", features other than that or those prefaced by the term may also be present. Related terms such as "comprise" and "comprises" are to be interpreted in the same manner. Directional terms such as “vertical”, “horizontal”, “up”, “down”, “top”, “bottom”, “upper” and “lower” are used for convenience of explanation usually with reference to the illustrations and are not intended to be ultimately limiting if an equivalent function can be achieved with an alternative dimension, orientation and / or direction. The description herein refers to examples and embodiments with particular combinations of features, however, it is envisaged that further combinations and cross-combinations of compatible features between examples and embodiments will be possible. Indeed, isolated features may function independently as an invention from other features and not necessarily require implementation as a complete combination. Figure 1 is a schematic side cross-sectional view of a pyrotechnic device 100. The housing 101 of the pyrotechnic device 100 is formed by a sidewall 110 and a bottom wall 115. The housing 101 defines a cavity 105. The housing 101 is configured to hold pyrotechnic components within the cavity 105 as discussed herein. The sidewall 110 comprises an upper end 111 and a lower end 112. The bottom wall 115 encloses the lower end 112 of the sidewall 110. The sidewall 110 and the bottom wall 115 are integrally formed, without a join between the sidewall 110 and the bottom wall 115, such that the housing 101 is monolithic. The pyrotechnic device 100 includes an igniter 120 which comprises an igniter head 120Aand a cable 120B. The sidewall 110 includes an aperture 145 arranged to allow the igniter head 120A to pass through and to accommodate the cable 120B. The aperture 145 is configured to vent the gases produced from the ignition of the explosive out of the housing 101 at a consistent rate. The cavity 105 houses an explosive 125, a flash paper dish associated with the explosive 150 positioned above the explosive 125, pyrotechnic stars 130 positioned above the flash paper dish associated with the explosive 150, a mine sponge 155 positioned above the pyrotechnic stars 130, and a flash paper dish associated with the mine sponge 160 positioned above the mine sponge 155. The housing 101 comprises an opening 135 at the upper end 111 of the sidewall 110. The pyrotechnic device 100 includes a cap 140 positioned over the opening 135, such that the cap 140 seals the opening 135. The cap 140 includes an adhesive sticker adhered to the upper end 111 of the sidewall 110. Upon ignition, the igniter 120 may ignite the explosive 125 positioned above. This may trigger the explosive 125 to combust and rapidly produce propellant gases, which propel the components above out of the housing 101 through the opening 135 of the housing 101. Ignition of the explosive 125 may result in the ignition and burning of the pyrotechnic stars 130. The flash paper dish associated with the explosive 150 may provide a flat support for the pyrotechnic stars 130 positioned above, allowing the pyrotechnic stars 130 to be evenly distributed and ignited. The mine sponge 155 may enable controlled dispersion of the pyrotechnic stars. The flash paper dish associated with the mine sponge 160 may further aid the ignition and dispersion of the pyrotechnic stars. The ignited pyrotechnic stars 130 may then be ejected from the housing 101 into the air above the pyrotechnic device 100 and burn to produce entertaining visual and audible effects. The housing 101 of the pyrotechnic device 100 is monolithic and consists of a single piece. The sidewall 110 and the bottom wall 115 form one continuous piece. The housing 101 of the pyrotechnic device 100 may be a tube with an inverted truncated cone shape. The upper end 111 has a width larger than a width of the lower end 112 (discussed in more detail with reference to Figure 2). The igniter 120 comprises an electric match. The explosive 125 comprises black powder. The pyrotechnic stars 130 are pellets of pyrotechnic composition that are arranged in two stacked layers. Other arrangements of the pyrotechnic stars 130, such as a single layer or more than two layers, is envisaged. The flash paper dish associated with the explosive 150 and the flash paper dish associated with the mine sponge 155 are pieces of flash paper configured to separate the respective components and ensure the components are ignited and burned. The mine sponge 155 is a piece of cylindrical sponge. The flash paper dish associated with the explosive 150, the flash paper dish associated with the mine sponge 160 and the mine sponge 155 each cover an entire cross-sectional area of the cavity 105. Figure 2 is a first schematic side cross-sectional view of the housing 101 of the pyrotechnic device shown in Figure 1. The housing 101 is symmetrical about a longitudinal axis 102 of the housing 101. The upper end 111 of the sidewall 110 has a width that is larger than a width of the lower end 112 of the sidewall 110. The sidewall 110 has a constant wall thickness such that the width of the cavity 105 changes according to the change in width of the sidewall 110. A rate of change in the width of the sidewall 110 from the lower end 112 to the upper end 111 is constant. As shown in Figure 2, the sidewall 110 and the cavity 105 have an inverted truncated cone shape with a constant rate of change in the width from the respective lower end to the respective upper end. The inverted truncated cone shape means that, upon ignition, the increasing cross-sectional area of the cavity 105 may act to stabilise the flow of gases along the cavity 105 by reducing turbulence in the flow. The bottom wall 115 includes a recess 116 centrally located on a surface of the bottom wall 115 facing the cavity 105. When a portion of an igniter is positioned within the recess 116, as shown in Figure 1, the recess 116 may ensure the igniter is held in the desired position within the cavity 105. In the example shown in Figure 2, the width of the upper end of the cavity 105 is approximately 30.7 mm. The width of the lower end of the cavity 105 is approximately 28.4 mm. The recess 116 has an upper end and a lower end, wherein the upper end has a width of approximately 23.5 mm and the lower end has a width of approximately 23.2 mm. Figure 3 is a second schematic side cross-sectional view of the housing 101 of the pyrotechnic device shown in Figure 1. The cavity 105 is symmetrical about a longitudinal axis 102 of the housing 101. The housing 101 has a total length of approximately 140 mm. The recess 116 is centrally located on a surface of the bottom wall 115 facing the cavity 105 and has a length of approximately 4.8 mm. The recess 116 is at a height of approximately 4mm above the lower end of the sidewall 110. The aperture 145 has a length of approximately 6.4 mm. The bottom wall comprises a single indentation 117 formed on a surface of the bottom wall 115 opposite the cavity 105. In this way, the indentation 117 may allow the bottom wall 115 to have a constant thickness and be correctly shaped and uniform during moulding, allowing the housing 101 to maintain its structural integrity under pressure, thereby preventing fracture in use. Figure 4 is a schematic side-view of the housing 101 of the pyrotechnic device shown in Figure 1. The housing 101 is symmetrical about the longitudinal axis 102. The aperture 145 is substantially rectangular. The aperture 145 has a length of approximately 4 mm and a width of approximately 3.5 mm. Figure 5 is a method diagram showing the steps of a pyrotechnic device manufacturing method 200. The method starts with the preparation of the components. First, a monolithic housing is provided 210. The monolithic housing provides the casing and support for the device.The housing comprises a sidewall that defines a cavity. The sidewall comprises an upper end and a lower end. The housing comprises a bottom wall arranged to close the lower end of the sidewall. A width of the upper end of the cavity is larger than a width of a lower end of the cavity. The housing may therefore be as described herein, with reference to Figures 1 to 4. Next, an igniter, pyrotechnic stars, and an explosive are provided within the cavity 215. In some examples, the housing may be provided with an opening 220. In some examples, the housing may be provided with a cap to cover the opening 225. In some examples, the housing may be provided with an aperture in the sidewall 230. In some examples, the igniter may be positioned proximate to the bottom wall 235; and the explosive may be positioned between the igniter and the pyrotechnic stars 240; a first flash paper dish may be positioned between the explosive and the pyrotechnic stars 245; a mine sponge may be positioned above the pyrotechnic stars 250; and a second flash paper dish may be positioned above the mine sponge 255. In some examples, a recess may be formed centrally on a surface of the bottom wall facing the cavity to receive at least a portion of the igniter; and at least one indentation may be formed on a surface of the bottom wall opposite the cavity.

Claims

1. A pyrotechnic device, comprising:a housing comprising:a sidewall that defines a cavity, wherein the sidewall comprises an upper end and a lower end; anda bottom wall arranged to close the lower end of the sidewall;wherein a width of an upper end of the cavity is larger than a width of a lower end of the cavity; andwherein the sidewall and the bottom wall are monolithic;an igniter, an explosive, and pyrotechnic stars arranged within the cavity; and a flash paper dish associated with the explosive, wherein the flash paper dish associated with the explosive is positioned between the explosive and the pyrotechnic stars.

2. The pyrotechnic device according to claim 1, wherein a rate of change in the width of the cavity from the lower end to the upper end is constant.

3. The pyrotechnic device according to any preceding claim, wherein the sidewall further comprises at least one aperture.

4. The pyrotechnic device according to claim 3, wherein the at least one aperture is located proximate to the lower end of the sidewall.

5. The pyrotechnic device according to claim 3 or claim 4, wherein the at least one aperture of the sidewall is configured to accommodate a portion of the igniter.

6. The pyrotechnic device according to any preceding claim, wherein the igniter is positioned proximate to the lower end of the sidewall and the explosive is positioned between the igniter and the pyrotechnic stars.

7. The pyrotechnic device according to any preceding claim, further comprising a mine sponge, wherein the pyrotechnic stars are positioned between the mine sponge and the explosive.

8. The pyrotechnic device according to claim 7, further comprising a flash paper dish associated with the mine sponge, wherein the mine sponge is positioned between the flash paper dish associated with the mine sponge and the pyrotechnic stars.

9. The pyrotechnic device according to any preceding claim, wherein the bottom wall comprises a recess centrally located on a surface of the bottom wall facing the cavity, wherein at least a portion of the igniter is arranged within the recess.

10. The pyrotechnic device according to any preceding claim, wherein the igniter comprises an electric match.

11. The pyrotechnic device according to any preceding claim, wherein a surface of the bottom wall opposite the cavity comprises at least one indentation, and the bottom wall has a substantially constant wall thickness.

12. The pyrotechnic device according to any preceding claim, wherein each of the pyrotechnic stars has a minimum dimension of at least 2 mm and a maximum dimension of no more than 8 mm.

13. The pyrotechnic device according to any preceding claim, wherein the explosive comprises black powder.

14. A method of manufacturing a pyrotechnic device, the method comprising: providing a housing, the housing comprising:a sidewall that defines a cavity, wherein the sidewall comprises an upper end and a lower end; anda bottom wall arranged to close the lower end of the sidewall;wherein a width of an upper end of the cavity is larger than a width of a lower end of the cavity, andwherein the sidewall and the bottom wall are monolithic;providing an igniter, pyrotechnic stars, and an explosive within the cavity; and positioning a first flash paper dish between the explosive and the pyrotechnic stars.

15. The method of claim 14, wherein:a rate of change in the width of the cavity from the lower end to the upper end is constant.

16. The method of claim 14 or 15, further comprising moulding the housing as a single piece.

17. The method of any of claims 14 to 16, wherein the method further comprises: providing at least one aperture in the sidewall to accommodate a portion of the igniter, wherein the at least one aperture is located proximate to the lower end of the sidewall.

18. The method of any of claims 14 to 17, further comprising:positioning the igniter proximate to the bottom wall;positioning the explosive between the igniter and the pyrotechnic stars;;positioning a mine sponge such that the pyrotechnic stars are between the mine sponge and the first flash paper dish; andpositioning a second flash paper dish such that the mine sponge is between the second flash paper dish and the pyrotechnic stars.

19. The method of any of claims 14 to 18, further comprising:forming a recess centrally located on a surface of the bottom wall facing the cavity to receive the igniter; andforming at least one indentation on a surface of the bottom wall opposite the cavity, wherein the bottom wall has a substantially constant wall thickness.T +44(0)30 0300 2000A

Images