BACKGROUND OF THE INVENTION

&null;0001&null; a. Field of the Invention

&null;0002&null; This invention relates to a new type of sparkler of the type used for pyrotechnical displays for amusement and holiday celebrations, such as the Fourth of July.

&null;0003&null; b. Description of the Prior Art

(I) SUMMARY OF THE INVENTION

&null;0004&null; Sparklers are non-explosive, pyrotechnic devices which have been enjoyed for many years by both children and adults. The basic form of these devices is well-known. A rod, usually made of wire, has a coating pyrotechnic composition which extends part of the way along the length of the rod. The sparkler is used by igniting the coating of the pyrotechnic composition. Ignition results in the composition burning with a bright light, which may be of various colors depending upon the materials used in the composition. The ignition also gives off streamers of sparks, producing a pleasurable visual experience, and explaining the common name &null;sparkler&null; for these devices. The sparkling display lasts until all the pyrotechnic composition has been exhausted through the burning process. The uncoated portion of the rod functions as a handle, which allows the user to hold the sparkler while the ignition is ongoing, or even to move the sparkler through the air creating visual designs. Alternatively, the uncoated handle can be pushed into the ground or another suitable surface for a stationary display.

&null;0005&null; Heretofore, the biggest drawback to the use of sparklers has been the difficulty in igniting them. Typically, the user will attempt to light the sparkler with a flame from some external source such as a match or lighter. Anyone who has attempted to do so can attest that this is often a frustrating and hazardous task. Despite the fact that the pyrotechnic composition burns with a bright light and showers of sparks once it has ignited, it is surprisingly difficult to start the ignition process in the sparklers which have been available prior to the present invention. The user often has to keep the match or lighter applied to the sparkler for many seconds before ignition occurs. This often results in the user's finger being burned from proximity to the flame while ignition is being attempted. The difficulty in igniting the pyrotechnic composition appears to be the result of the hard crust on the pyrotechnic composition coating. Aside from safety concerns caused by the need to apply a flame to the sparkler for an extended period before ignition occurs, an additional drawback is simply the inconvenience caused by the delay. Since sparklers are often used for the entertainment of children, even such a seemingly minor delay can be magnified to the point of being a major inconvenience.

&null;0006&null; Accordingly, it is an object of the present invention to provide a new type of sparkler which can be ignited quickly, easily, and safely with no need to provide an external source of flame. It is a further object of the invention to provide a sparkler which contains an integral ignition mechanism in the form of a match head composition tip which will allow the sparkler to be struck like a match, thereby easily and quickly igniting the coating of pyrotechnic composition.

&null;0007&null; A further object of the present invention is to provide a method for producing a self-igniting sparkler.

(ii) BRIEF DESCRIPTION OF THE DRAWINGS

&null;0008&null; FIG. 1 shows a perspective view of a self-igniting sparkler according to the invention;

&null;0009&null; FIG. 2 shows a cut-away plan view of a self-igniting sparkler according to the invention;

&null;0010&null; FIG. 3 shows the use of a self-igniting sparkler according to the invention.

(iii) DESCRIPTION OF THE PREFERRED EMBODIMENT

&null;0011&null; As shown in FIG. 1, the sparkler comprises a rod 12, one end of which is a handle 14. Adjacent to the handle 14 on the rod 12 and extending generally along the remaining length of the rod 12 is a pyrotechnic composition coating 16. Bonded to the pyrotechnic composition coating 16 at a point furthest from the handle 14 is a self-igniting match head tip 18. The rod 12 is generally thin and elongated. It can be made of a number of materials, most commonly metal wire. Another material which can be used for the rod 12 is wood. Another material which can be used for the rod 12 is a paper-related product such as compressed cardboard. Still other materials which could be suitable for use as the rod 12 include synthetics or flour-based solids such as are commonly used for pasta products. It can thus be seen that any solid material which can be formed into a thin, elongated shape, and which is either non-combustible, or not quickly combustible, is potentially suitable for use as a rod 12.

&null;0012&null; In addition to acting as a carrier for the pyrotechnic composition coating 16, the rod 12 is important for other reasons. Experimentation has shown that the choice of material for the rod 12 also has an effect on the sparkler's rate of burn and the pyrotechnic display created. For instance, the rod 12 can provide fuel for the burning reaction, including a source of sparks. The iron in commonly used wire is heavily eroded during burning of the sparkler and provides up to 20% of the total number of sparks produced. A rod 12 made of wire can also regulate the propagation of burning. The wire absorbs energy which warms it, removing heat from the reaction and preventing a runaway reaction. The heated wire, however, then transmits heat to the unburned portion of the pyrotechnic composition coating 16, promoting smoother ignition. The rate of heat transmission depends on the thermal mass of the wire, so that all else being equal a thinner wire used as a rod 12 will allow for a more rapid burn.

&null;0013&null; When non-metallic materials are used for the rod 12 they will generally not contribute significantly to spark production unless specially formulated to do so. These non-metallic materials also are usually poorer heat transmitters, resulting in a slower burn rate.

&null;0014&null; The handle 14 is simply a portion of the rod 12 which is left clear of any pyrotechnic composition coating 16 to allow the user to safely grasp the sparkler and hold it while it is burning. The handle 14 can also be inserted into the ground or into some other suitable place to hold the sparkler in a stationary position if it is desired to have it burn without being held by a person.

&null;0015&null; The pyrotechnic composition coating 16 is made by dipping the rod 12 up to the desired point into a container of a suspension of pyrotechnic composition. When the rod 12 is withdrawn from the suspension, some of the suspension adheres to the rod 12. This is allowed to dry to a solid, thereby forming the pyrotechnic composition coating 16. This dipping process can be done once or repeated multiple times to build the pyrotechnic composition coating 16 to the desired thickness. As will be discussed further below, there are many varieties of pyrotechnic composition which have been used in making sparklers. The selection of the particular variety of pyrotechnic composition, the number of dips, and changing the pyrotechnic composition for each dip can each affect the resultant performance properties of the sparkler. The actual working of a sparkler can now be discussed.

&null;0016&null; The pyrotechnic composition of a sparkler serves at least three (3) functions, although individual chemicals often serve dual purposes. First, there is the pyrotechnic reaction itself, which consists of an oxidizer and a fuel. The burning of the fuel by the oxygen released by the oxidizer releases heat. Some of this heat is used to decompose the oxidizer, and to warm the composition to the ignition temperature. The remainder of the heat is available for the generation of light, sound, and sparks which the pyrotechnic reaction generally also produces. Secondly, there is the spark generating system. This is a chemical or combination of chemicals which will create sparks when heated by the pyrotechnic reaction. Third, there is the binder, which binds the composition together, and holds it on the 12. The binder is often an organic compound, such as animal glue, shellac, or dextrin, and may serve as a fuel as well. Finally, if a colored flame is desired, then a fourth component&null;a color generation system must be included.

&null;0017&null; The pyrotechnic composition used in any embodiment of the invention is of the typical kind as is commonly used in sparklers. These pyrotechnic compositions include an oxidizer or combination of oxidizers, including, but not limited to, potassium nitrate, potassium perchlorate, potassium chlorate, barium nitrate, ammonia perchlorate, bismuth oxide, bismuth nitrate, or strontium nitrate. These pyrotechnic compositions also include a fuel, including, but not limited to charcoal, lampblack, red gum, lactose, cellulose, dextrine, hexamine, sulphur or antimony trisulphide. The oxidizer and fuel together produce the fundamental pyrotechnic reaction. As is well known, the fuel is a material which reacts vigorously with oxygen, in this case contained in the oxidizer, to produce heat and often various gasses, liquid, or solid by-products.

&null;0018&null; The second important function of a pyrotechnic composition is spark generation. Metallic additives are usually added to the composition to generate sparks, to function as an additional fuel, or to do both. Common metallic additives include iron, magnalium, aluminum, titanium, ferroaluminum, ferrotitanium, zircalium, copper, copper-magnesium, and others.

&null;0019&null; A simple spark consists of a fuel particle which burns as it falls through the air. The spark can consist of finely divided charcoal, a metal dust, various inorganic salts, or mixtures of various chemicals. The spark particle must be ejected from the burning mass of the composition, which means that the base pyrotechnic reaction must be &null;gassy&null;. Thus, reactions high in charcoal, sulfur, or other fuels that generate a lot of gaseous products are very useful. In addition, the spark particle must be heated above it's ignition temperature before leaving the flame envelope. The ignition temperatures for some common fuels are given below in Table 1. It can be seen that the metal fuels require a higher temperature than the organic fuels.

1

TABLE 1

Fuel

Ignition Temp (C. &null;)

Sulfur

220

Charcoal

335

Magnesium

540

Aluminum

785

&null;0020&null; The spark emits light through black-body radiation, and the color of the spark is completely determined by the temperature. It is possible for small particles to emit light by other means, but it is then called a &null;micro star&null;, and the typical light-emitting chemistry governs the color of the light. Table 2 gives the relation between black body temperature and color. Note that brightness is also controlled by temperature.

2

TABLE 2

Temp (C. &null;)

Color

Brightness

500

red

dim

850

red-orange

low

1500

orange

medium

2200

yellow

high

3000

white

very high

&null;0021&null;

3

TABLE 3

Table 3 gives the colors of common fuels.

Material

Color

Charcoal

Orange

Iron

Yellow

Aluminum

Yellow to white

Titanium

Pale yellow to white

Zirconium

White

Magnesium

White

&null;0022&null; Metal fuel particles are very small, typically ranging from 12 to 30 microns (millionths of a meter) in diameter. A particle of this size can burn completely in a very short time (less than hundredths of a second) if the burning rate is not slowed by some mechanism. This can be accomplished by utilizing a pyrotechnic reaction that creates a dross that partially coats the fuel, slowing the access of atmospheric oxygen to the fuel surface.

&null;0023&null; A complex spark is one in which there is more than one chemical reaction, which leads to a secondary &null;explosion&null; of sparks. This is often referred to as &null;glitter&null;. One simple material which gives a glitter-like effect is magnalium alloy. This is a 50:50 mixture of Magnesium and Aluminum. As a hot magnalium particle falls through the air, the magnesium burns, thus raising the temperature of the particle. When the temperature reaches the kindling point of aluminum, the particle explodes in small shower of micro-sparks.

&null;0024&null; A third function of a pyrotechnic composition is binding, for which binders are added to the composition to bind or join the various materials together and to the rod 12. Fortunately these binders can generally be chosen to fulfill more than one function. Binders such as dextrin, shellac, or red gum are also fuels. Some chlorinated compounds such as chlorinated rubber (parlon), PVC, and saran resins are both weak fuels and good chlorine donors. The chlorine donors are needed for the production of colored light. Some formulations utilize nitrocellulose (the basis of smokeless powder) as a binder. Composite rocket builders often use polymers which not only bind the fuel and oxidizer into a single grain, but which are more chemically consistent and uniform than some of the natural fuels (e.g. red gum).

&null;0025&null; The binder needs to be partially dissolved in a solvent before it begins to bind the components together. The choice of solvent is determined not only by the binder, but also by the other components in the composition. For example, a water/dextrin system cannot be used with unprotected magnesium metal because the water would react with and destroy the magnesium. When a magnesium fuel is utilized then an acetone-based solvent system must be used (acetone with PVC, parlon, saran or nitrocellulose), or the magnesium needs to be coated with a water-impervious barrier.

&null;0026&null; Acetone has several problems as a solvent&null;it is highly flammable, narcotic and toxic when inhaled, and evaporates quickly. Methyl vinyl ketone reduces some of the problem, since it is less volatile, but it evaporates more slowly, thus causing problems with processing time. When using any volatile organic solvent one must work in a vapor cabinet or with special ventilation systems. This will protect the lungs, but it can cause problems because of increased evaporation. The rapid evaporation will cause a drop in temperature which can cause condensation. Condensation can be a significant problem if the composition is water sensitive. Acetone can be used with care, but one must be ready to address all of these problems.

&null;0027&null; Besides acetone-based systems, there are water/ethanol based binder systems. Some binders are activated by water alone. These include carbohydrates such as dextrin, sucrose, and lactose. On the other hand, red gum is impervious to water but is activated by alcohol. However, neither binder alone would normally be activated with either pure water or pure alcohol. Pure water may give problems since it has a high surface tension and it evaporates slowly. Alcohol may be added to water to help the solvent wet the surfaces of components (such as sulfur) and to promote more rapid drying. The optimum ratio varies with the specific mixture, but 25% alcohol in water is a good starting point when optimizing formulations.

&null;0028&null; In addition, various plant gums, such as gum arabic, gum guar, and gum tragacanth can be used. These may be acidic (arabic), expensive, or may show problems with microbial attack upon storage. However, they have certain properties, such as a higher degree of flexibility, that may make them appropriate for certain processes.

&null;0029&null; Animal glues can be used for certain processes, and are often used for matchmaking. This is due to the favorable strength/viscosity properties, where the viscosity of the mixture is critical. However, animal glues can have undesirable odors upon burning. This can be advantageous if the manufacturer wishes to discourage breathing of the fumes, especially if they contain barium, chromium, etc. Perfumes, such as cinammic acid, etc., can be added to partially offset the bad odors.

&null;0030&null; An additional material which is sometimes added to the pyrotechnic composition is a burn regulator, i.e., a substance which will moderate, enhance, or otherwise regulate the burning rate of the composition. Among the substances used as burn regulators are copper, copper salts, chromium salts, vanadium salts, titanium salts, manganese salts, cellulose, and guanidine salts. Finally, to the pyrotechnic composition is sometimes added other materials to generate secondary effects while the composition is burning, including such effects as one or more of the following: color addition, color enhancement, glitter, strobing, and crackling microstars. Glitter-producing materials include barium, sodium, antimony, lithium, bismuth sulfate, strontium sulfate, carbonates, oxides, hydroxides, and oxalates. Color-producing materials include copper, barium, strontium, and chlorine donors. Additives which induce strobing are generally granulated compounds consisting of combinations of oxidizers, fuels, and burn rate regulators. Crackling microstar additives are granulated compounds comprised of an oxidizer, a fuel, and a binder.

&null;0031&null; Keeping the above principles in mind, it should be apparent that there are many possibilities for satisfactory pyrotechnical composition. The pertinent literature describes numerous combinations which have been used as a pyrotechnic composition for a sparkler. Listed below in Table 4 are some representative pyrotechnic compositions for use in sparklers as described in the literature.

4

TABLE 4

&null;1

&null;2

&null;3

&null;4

&null;5

&null;6

&null;7

&null;8

&null;9

10

KNO3

47

38

64

50

KClO4

29

50

&null;3

40

Ba (ClO3)2

Ba (NO3)2

18

15

52

49

Sr (NO3)2

80

Charcoal

14

10

&null;5

Sulfur

&null;9

10

18

10

Dextrin

10

10

15

13

14

12

Shellac

&null;9

15

Iron filings

57

19

26

28

22

Aluminum

&null;5

&null;2

&null;5

35

&null;6

25

&null;8

&null;7

14

Sb2S3

10

red gum

&null;4

10

MnO2

&null;2

&null;1

&null;2

1 Weingart, Pyrotechnics, Chemical Publishing Company, New York 1947 at page 189

2Best of AFTN III, Jack Drews, Editor, American Fireworks News, P.O. Box 30, Dingmans Ferry, PA 18328, page 31

3 Weingart, ibid

4 Weingart, ibid

5 Tenney L. Davis, Chemistry of Powder and Explosives, 1943 at page 117

6 Davis, ibid at page 118

7 Davis, ibid at page 118

8 David, ibid at page 118

9 A. Kelsey, Amateur Fireworks (self-published available through Skylighters), page 22

10 Davis, ibid at page 120

&null;0032&null; Table 4 is not meant to be exhaustive. There are numerous pyrotechnic compositions which can be used to create a sparkling effect using the general approach of oxidizer, plus fuel, plus binder, plus burn regulator, plus the option of additional additives, all as described above.

&null;0033&null; Discussion may now turn to the match head tip 18 which provides the self-igniting feature that chiefly distinguishes the present invention from other sparklers. The match head tip 18, like the pyrotechnic composition, is a combination of materials and is not in itself novel. The composition of the match head tip 18 includes an oxidizer or a mixture of oxidizers in the form of a chlorate such as potassium chlorate, barium chlorate, lithium chlorate, or sodium chlorate. The match head tip 18 composition further includes a fuel such as antimony trisulphide, phosphorous, sesquisulfide or sulphur. To this mixture is added a neutralizer, including, but not limited to the carbonates, bicarbonates, or oxides of zinc, strontium, barium, or potassium, and one or more binders including but not limited to dextrin, starch, plant gums or animal glues, and burn rate catalysts including but not limited to potassium dichromate, potassium chromate, bismuth oxide, or banatium oxide. Finally, the match head tip 18 may also include a friction inducing material such as ground glass.

&null;0034&null; As with the pyrotechnic composition, there is no specific formula claimed here for the match head tip composition, many formulae of which are well known and are described in the literature. See, for example, Radkowski, U.S. Pat. No. 5,009,729.

&null;0035&null; Generally speaking, matches come in two basic types: strike any where (SAW) and safety matches. In each of these two types of matches the basic reaction depends on the friction sensitivity of chlorate/phosphorous mixtures combined with the ignition sensitivity of chlorate/sulfur mixtures. The SAW match combines all components in a single match head, while the safety match divides the components, with a chlorate/fuel mixture on the match head, and a red phosphorous-containing mixture on the striking surface. The friction of the striking action is increased by mixing in a substantial amount of ground glass. The match head generally contains a chlorate/sulfur or chlorate/sulfide mixture, which can oxidize to form sulfur-based acids. These acids can react with the chlorates to give chloric acid, which can spontaneously ignite or burn. Thus an ant-acid, such as a carbonate or metal oxide must be added to prevent this reaction. In addition, burn rate catalysts, such as chromium, lead, or bismuth salts are added. Finally, a binder must be added to hold the entire mixture in place.

&null;0036&null; The chlorate chosen is generally potassium chlorate, due to lack of hygroscopicity, toxicity, and low cost. The sulfur is provided in the form of elemental sulfur, or of a sulfide such as antimony trisulfide or phosphorous sequisulfide. The sulfur not only acts to help promote and continue the small reaction instigated between the chlorate and phosphorous, but it also acts as a type of &null;perfume&null;.

&null;0037&null; The binder may be dextrin, starch, plant gums or animal glue. The advantage to animal glue is that it has not only a &null;drying reaction&null;, wherein the material hardens upon the evaporation of the solvent (water), but there is also a &null;gelling reaction&null;, wherein the material stiffens as it cools past a well-defined temperature. This allows the use of a current of cool dry air to &null;freeze&null; the composition in place, affording greater control over shape. A typical value for this setting point is around 29&null; C., or 85&null; F. The match head tip 18 of the invention is obtained much like the pyrotechnic composition coating 16, i.e. by dipping the rod 12 into a suitable suspension of match head tip composition, withdrawing the rod 12, and allowing the resulting coating to dry. Additional cycles of dipping can be performed if necessary.

&null;0038&null; The action of the self-igniting sparkler of the present invention can now be appreciated. After the sparkler is removed from its packaging, the user can simply strike the match head composition tip 18 on a suitable surface, whether a special striking surface as with a safety match, or on any friction producing surface of the saw-type match head. The friction created by this striking action will cause the match head composition tip 18 to ignite, and the heat and flame thereby generated will in turn cause the pyrotechnic composition coating 16 to ignite, initiating the sparkler's display.

&null;0039&null; The present invention further discloses a method of manufacturing self-igniting sparklers. The basic process for manufacturing sparklers is well-known. A trough is filled with a suspension of pyrotechnic composition. A device capable of firmly holding a large number of rods 12 extending vertically downward from the holder is positioned over the trough. One embodiment of this device, often called a dipping board, is a length of wood with numerous small grooves cut along its length perpendicular to the boards longitudinal axis. A hole is drilled through the length of the wood so that it passes through the lands between the grooves. A threaded rod is passed through this hole, and a washer and wing nut are supplied for each end. The handle 14 portions of the rods 12 to be dipped are inserted into the grooves, and the wing nuts are then tightened, resulting in a clamping action which securely holds the rods 12.

&null;0040&null; The dipping board is then lowered slowly into the trough, and as the pyrotechnic composition in suspension flows around the rods 12 it coats them. When the rods 12 are withdrawn, possibly after being stirred, the pyrotechnic composition in suspension thickens sufficiently so that a built-up layer adheres to the rods 12. The coating is then permitted to dry until it becomes solid. This process can be done once, or can be repeated multiple times, until the desired final pyrotechnic composition body is achieved.

&null;0041&null; In the present invention, the final step would be a dip into a trough containing match head composition. In general, this can be much thicker than the pyrotechnic composition suspension, and the dip itself will be much shallower, so that only the tip of the rod or pyrotechnic composition coating is coated with match head composition.