GB2141528A - Firework - Google Patents

Abstract

A method of manufacturing a pyrotechnic device comprises filling a tube formed of a shrinkable material with a pyrotechnic composition and then causing the tube to shrink so as to compress the pyrotechnic composition therein. The shrinkable material is suitably a plastics material having a plastic "memory" such that on heating it reverts to smaller dimensions than the initial dimensions before heating. The method is suitable for manufacturing fireworks such as catherine wheels where a long tube of pyrotechnic composition is formed into a spiral.

Description

SPECIFICATION Firework This invention relates to a method of manufacturing a pyrotechnic device such as a firework.

Traditionally, ffreworks are manufactured by filling a tubular paper or cardboard case with a pyrotechnic mixture, and then consolidating the filling mechanically by, e.g. tamping, pressing or vibrating. These techniques have the disadvantage of being time consuming, and it is difficult to produce a consistent degree of consolidation, especially when the length of the tube is great in comparison with its diameter, as in the case with fireworks such as lances, portfires and catherine wheels.

According to the present invention, a method of manufacturing a pyrotechnic device comprises filling a tube formed of a shinkable material with a pyrotechnic composition and then causing the tube to shrink, thereby compressing the pyrotechnic composition therein.

The shrinkable material is preferably a plastics material having a plastic "memory" such that the application of heat causes the material to revert to dimensions smaller than the initial dimensions before heating. Such materials may be poly(vinyl chloride), cross-linked polyolefins, chlorinated elastomers, poly(vinylidene fluoride) derivatives, and polytetrafluoroethylene, for example, the materials being treated during moulding into a tube to be heat-shrinkable.

Preferably, one end of the tube is closed before filling, either by welding or plugging, and a seal, which may be a fuze, is used to close the other end before the tube is heated.

Heat may be applied by any technique known for shrinking such tube, for example by blowing heated air over the tube.

The tubing can be selected to be consumed as the firework burns or to retain its integrity.

The dimensions and the degree of compaction achieved in the completed device may be controlled by selection of suitable tubing materials having the appropriate degree of shrinkage.

The method of the invention permits pyrotechnic devices to be manufactured quicker and more reliably than with existing techniques, and, since the compaction obtained is more consistent, the performance of the devices is also more consistent. A further advantage is that the method permits the manufacture of some pyrotechnic devices to be at least partially automated, whereas fireworks are typically produced entirely or mainly by hand.

The tube may be elongate and may be formed into any desired shape after composition, for example into a spiral to form a catherine wheel.

1. A method of manufacturing a pyrotechnic device, comprising filling a tube formed of a shrinkable material with a pyrotechnic composition, and then causing the tube to shrink, thereby compressing the pyrotechnic composition therein.

2. A method according to Claim 1, wherein the shrinkable material is a plastics material having a plastic memory such that application of heat causes the material to revert to dimensions smaller than the initial dimensions before heating, and the method comprises heating the filled tube.

3. A method according to Claim 2, wherein the tube is heated by blowing heated air over the tube.

4. A method according to Claim 1, 2 or 3, comprising closing one end of the tube before filling and the other end of the tube before the tube is heated.

5. A method according to Claim 4, wherein the one end of the tube is closed by welding or plugging.

6. A method according to Claim 4 or 5, wherein a seal comprising a fuze is used to closed the other end of the tube.

7. A method according to any preceding claim, wherein the shrinkable material is selected to burn with the pyrotechnic composition.

8. A method according to any of Claims 1 to 6, wherein the shrinkable material is selected to retain its integrity during burning of the pyrotechnic composition.

9. A method according to any preceding claim; which comprises the step of. forming the filled tube into a predetermined configuration and securing the tube in the configuration.

10. A method of manufacturing a pyrotechnic device, substantially as described.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (10)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Firework This invention relates to a method of manufacturing a pyrotechnic device such as a firework. Traditionally, ffreworks are manufactured by filling a tubular paper or cardboard case with a pyrotechnic mixture, and then consolidating the filling mechanically by, e.g. tamping, pressing or vibrating. These techniques have the disadvantage of being time consuming, and it is difficult to produce a consistent degree of consolidation, especially when the length of the tube is great in comparison with its diameter, as in the case with fireworks such as lances, portfires and catherine wheels. According to the present invention, a method of manufacturing a pyrotechnic device comprises filling a tube formed of a shinkable material with a pyrotechnic composition and then causing the tube to shrink, thereby compressing the pyrotechnic composition therein. The shrinkable material is preferably a plastics material having a plastic "memory" such that the application of heat causes the material to revert to dimensions smaller than the initial dimensions before heating. Such materials may be poly(vinyl chloride), cross-linked polyolefins, chlorinated elastomers, poly(vinylidene fluoride) derivatives, and polytetrafluoroethylene, for example, the materials being treated during moulding into a tube to be heat-shrinkable. Preferably, one end of the tube is closed before filling, either by welding or plugging, and a seal, which may be a fuze, is used to close the other end before the tube is heated. Heat may be applied by any technique known for shrinking such tube, for example by blowing heated air over the tube. The tubing can be selected to be consumed as the firework burns or to retain its integrity. The dimensions and the degree of compaction achieved in the completed device may be controlled by selection of suitable tubing materials having the appropriate degree of shrinkage. The method of the invention permits pyrotechnic devices to be manufactured quicker and more reliably than with existing techniques, and, since the compaction obtained is more consistent, the performance of the devices is also more consistent. A further advantage is that the method permits the manufacture of some pyrotechnic devices to be at least partially automated, whereas fireworks are typically produced entirely or mainly by hand. The tube may be elongate and may be formed into any desired shape after composition, for example into a spiral to form a catherine wheel. CLAIMS

1. A method of manufacturing a pyrotechnic device, comprising filling a tube formed of a shrinkable material with a pyrotechnic composition, and then causing the tube to shrink, thereby compressing the pyrotechnic composition therein.

2. A method according to Claim 1, wherein the shrinkable material is a plastics material having a plastic memory such that application of heat causes the material to revert to dimensions smaller than the initial dimensions before heating, and the method comprises heating the filled tube.

3. A method according to Claim 2, wherein the tube is heated by blowing heated air over the tube.

4. A method according to Claim 1, 2 or 3, comprising closing one end of the tube before filling and the other end of the tube before the tube is heated.

5. A method according to Claim 4, wherein the one end of the tube is closed by welding or plugging.

6. A method according to Claim 4 or 5, wherein a seal comprising a fuze is used to closed the other end of the tube.

7. A method according to any preceding claim, wherein the shrinkable material is selected to burn with the pyrotechnic composition.

8. A method according to any of Claims 1 to 6, wherein the shrinkable material is selected to retain its integrity during burning of the pyrotechnic composition.

9. A method according to any preceding claim; which comprises the step of. forming the filled tube into a predetermined configuration and securing the tube in the configuration.

10. A method of manufacturing a pyrotechnic device, substantially as described.