Abstract:
A pyrotechnic display device configured to ignite solid pyrotechnic compositions or aerial shells within a launch tube prior to propelling them on a desired arc. A smokeless pyrotechnic propelling charge is disposed within the launch tube below the solid pyrotechnic compositions, and separated therefrom. An ignition source is disposed in operative relationship to the pyrotechnic compositions or aerial shells, which are ignited prior to ignition of the smokeless pyrotechnic propelling charge.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   The present application is related to, and claims priority from, U.S. Provisional Patent Application Ser. No. 60/448,304 filed on Feb. 19, 2003. 

   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
   Not Applicable. 
   BACKGROUND OF THE INVENTION 
   The present invention relates generally to pyrotechnic display devices commonly referred to as fireworks, and in particular, to a pyrotechnic display device configured to produce an aerial shell, comet, or mine which, when ignited, smokelessly expels either non-burning body containing a burst charge and stars, or a solid pyrotechnic color or effect, to generate a reduced smoke aerial display, comet display, or star display. 
   Traditionally, black power is used in the majority of pyrotechnic display devices for igniting and propelling solid pyrotechnic compositions such as star or comet displays from a launch tube. Black powder offer the advantages of rapid and hot combustion, thereby propelling the solid pyrotechnic compositions from the launch tubes to a desired apex while simultaneously providing sufficient heat to ignite the composition, a prime explosive, or a delay fuse on an aerial shell. 
   It is known however, that black powder propellant produces a large volume of smoke during combustion. This is particularly troublesome for pyrotechnic display devices intended for use within a building interior, such as an enclosed arena or stadium, or for use outside if the pyrotechnic display devices or aerial shells are discharged in close proximity to spectators, exhibitors, or other activities which would be obscured or impeded by the significant smoke produced during combustion. 
   A smokeless propellant which is commonly utilized in firearms is to provide an expelling force for a projectile is nitrocellulose. However, the use of nitrocellulose in entertainment pyrotechnic display devices is not common because nitrocellulose combustion occurs at a relatively low temperature. Low temperature combustion of nitrocellulose provides sufficient force to propel solid pyrotechnic compositions from a launch tube to a desired apex, but lacks a sufficient heat of combustion to ignite the compositions, their primes, or the delay fuses on aerial shells. Traditionally, nitrocellulose use in display pyrotechnic devices is limited to expelling non-burning items such as confetti, or it is utilized as a noise maker in party poppers and novelty devices. 
   Accordingly, there is a need in the industry for a display pyrotechnic device which is capable of both igniting solid pyrotechnic compositions, their primes, or aerial delay fuses and propelling the burning composition or aerial shell on a desired arc from a launch tube with a minimum amount of smoke. 
   BRIEF SUMMARY OF THE INVENTION 
   Briefly stated, a first embodiment the present invention provides a pyrotechnic display device configured to ignite solid pyrotechnic compositions within a launch tube prior to propelling them on a desired arc. A propelling charge of nitrocellulose is disposed within the launch tube below the solid pyrotechnic compositions, and separated therefrom by a gas-sealing disk. The an upper surface of the gas-sealing disk, adjacent the solid pyrotechnic compositions is optionally coated with a pyrotechnic prime compositions to facilitate rapid and uniform ignition of the solid pyrotechnic compositions. A combustion delay material disposed over an axial bore in the gas-sealing disk ensures ignition of the solid pyrotechnic compositions prior to combustion of the nitrocellulose propelling charge. A plurality of optional radial gas ports or vents are disposed in the launch tube adjacent the mouth or bore opening through which the ignited solid pyrotechnic compositions are expelled by the propellant. 
   A second embodiment the present invention provides a pyrotechnic aerial shell device configured to ignite a delay fuse associated with a non-burning body containing a burst charge or pyrotechnic stars within a launch tube prior to propelling the non-burning body on a desired arc. A propelling charge of nitrocellulose is disposed within the launch tube below the non-burning body, and separated therefrom by a gas-sealing disk. The an upper surface of the gas-sealing disk, adjacent the non-burning body is optionally coated with a pyrotechnic prime compositions to facilitate rapid ignition of the delay fuse. A combustion delay material disposed over an axial bore in the gas-sealing disk ensures ignition of the delay fuse prior to combustion of the nitrocellulose propelling charge. A plurality of optional radial gas ports or vents are disposed in the launch tube adjacent the mouth or bore opening through which the non-burning body and ignited delay fuse are expelled by the propellant. 
   A method of the present invention provides for assembling a pyrotechnic display device capable of propelling an ignited solid pyrotechnic composition with a minimal discharge of smoke. A launch tube having a closed base and an open bore is loaded with a nitrocellulose propellant charge. A gas sealing and lifting disk having an axial bore is installed within the open bore, enclosing the nitrocellulose propellant charge. A combustion delay component, such as a Styrofoam disk is dispose over the axial bore of the gas sealing and lifting disk. At least one solid pyrotechnic composition is placed in the open bore, on the upper surface of the gas sealing and lifting disk, and a paper cap or burst disk is utilized to retain the at least one slid pyrotechnic composition and components within the open bore. One or more electrical igniters or fuses or placed in operative relation to the at least one solid pyrotechnic composition. 
   A method of the present invention for igniting a smokeless pyrotechnic device includes the steps of igniting, within a launch tube, a pyrotechnic prime material in proximity to a fast burning cored pressed pyrotechnic composition. Upon propagation of flame about the surface of the cored pressed pyrotechnic composition, igniting a smokeless propellant charge disposed below the cored pressed pyrotechnic composition within the launch tube, thereby expelling the ignited pyrotechnic composition from the launch tube along a desired arc. 
   An alternate method of the present invention for igniting a smokeless aerial shell pyrotechnic display device includes the steps of igniting, within a launch tube, a delay fuse associated with a burst charge or plurality of pyrotechnic stars contained with a non-burning body. Upon ignition of the delay fuse, a smokeless propellant charge disposed below the non-burning body within the launch tube is ignited, thereby expelling the ignited aerial shell from the launch tube along a desired arc. 
   The foregoing and other objects, features, and advantages of the invention as well as presently preferred embodiments thereof will become more apparent from the reading of the following description in connection with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     In the accompanying drawings which form part of the specification: 
       FIG. 1  is an exploded sectional view of the components of a first embodiment of a smokeless pyrotechnic display device of the present invention; and 
       FIG. 2  is a sectional view of the assembled components of a the smokeless pyrotechnic display device of  FIG. 1 ; 
       FIG. 3  is an exploded sectional view of the components of a second embodiment of a smokeless pyrotechnic display device of the present invention; and 
       FIG. 4  is a sectional view of the assembled components of a the smokeless pyrotechnic display device of  FIG. 3 ; and 
       FIG. 5  is a sectional view of an aerial shell embodiment of the present invention. 
   

   Corresponding reference numerals indicate corresponding parts throughout the several figures of the drawings. 
   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   The following detailed description illustrates the invention by way of example and not by way of limitation. The description clearly enables one skilled in the art to make and use the invention, describes several embodiments, adaptations, variations, alternatives, and uses of the invention, including what is presently believed to be the best mode of carrying out the invention. 
   As used herein, the term smokeless is intended to describe pyrotechnic applications which generate significantly less visible smoke than found in traditional black-powder pyrotechnic applications. The term is not intended to be limiting to only pyrotechnic applications which produce no visible smoke. 
   To achieve the intended purpose of the present invention, i.e. to provide a smokeless pyrotechnic display device or aerial shell, it is necessary to utilize a launch tube configured to create sufficient pressure from the combustion of a smokeless pyrotechnic propellant to launch a previously ignited pyrotechnic composition or a non-burning body with a previously ignited delay fuse to a desired altitude, while simultaneously avoiding premature extinguishment of the pyrotechnic composition or aerial shell delay fuse from high velocity lift gasses or surrounding airflow. 
   Turning to  FIG. 1  and  FIG. 2 , a first embodiment of the pyrotechnic display device  100  of the present invention is illustrated. The pyrotechnic display device  100  consists of a launch tube or barrel  102  having a generally cylindrical configuration and an enclosed base  104  The launch tube or barrel  102  preferably formed from spiral wound paper having an open discharge end  106 , but may consist of any of a wide variety of materials having sufficient strength to maintain a shape during ignition and combustion of the pyrotechnic display device  100 . Optional radial gas vents  107  may be disposed adjacent the open discharge end  106 . The enclosed base  104  is preferably formed from a molded plastic, defining a open-ended combustion chamber  108 , and is configured for attachment to the launch tube or barrel  102 , opposite the open discharge end  106 . 
   As illustrated in  FIGS. 1 and 2 , the enclosed base  104  is generally cylindrical, having a uniform inner radial dimension R 1 , and a uniform outer radial dimension R 2 . An annular recessed region  110  is provided adjacent an open end  112  of the combustion chamber  108 . The annular recessed region  110  maintains the uniform inner radial dimension R 1 , but has a reduced uniform outer radial dimension R 3 , sized to receive the inner cylindrical surface  114  of the launch tube or barrel  102 , having an inner radial dimension R 4 , in an interference fit, abutting an annular ridge  116  on the outer surface  118  of the enclosed base  104 . 
   Those of ordinary skill in the art will recognize that the enclosed base  104  may optionally be constructed integrally with the launch tube or barrel  102 , or coupled thereto in a variety of different manners, and may consist of any of a variety of shapes and sizes, depending upon the particular application for which the pyrotechnic device  100  is to be utilized. 
   A smokeless lift charge or pyrotechnic propellant  120 , preferably nitrocellulose, is placed within combustion chamber  108  of the enclosed base  104 . The quantity of smokeless pyrotechnic propellant  120  is selected in a conventional manner, based upon the combustion characteristics of the smokeless pyrotechnic propellant  120  and the particular loads which are intended to be ejected from the launch tube or barrel  102 . 
   Disposed above the level of the smokeless pyrotechnic propellant  120  within the combustion chamber  108  of the enclosed base  104 , a radially inward projecting shoulder  122  supports a gas sealing disk  124 . The gas sealing disk  124  includes an axial bore or passage  126 , and is sized to fit securely within the combustion chamber  108  when seated on the shoulder  122 . Optionally, a conventional pyrotechnic prime composition  127  is deposited on an upper surface  128  of the gas sealing disk, opposite from the smokeless pyrotechnic propellant  120 . A combustion delay component  130  is disposed within the combustion chamber  108 , above the gas sealing disk  124 , and in axial alignment with the axial bore or passage  126 . The combustion delay component  130  preferably is formed from Styrofoam or a similar combustion delay material. 
   Next, one or more pyrotechnic compositions  132  are disposed within the combustion chamber  108 , with the initial pyrotechnic composition  132  seated on the upper surface  128  of the gas sealing disk. Each pyrotechnic composition  132  is preferably formed as a pressed solid, and includes a open central core  134 . The outer radial dimensions of each pyrotechnic composition  132  is selected to be smaller than the inner radial dimension R 4  of the launch tube or barrel  102 , thereby providing a combustion facilitating air-gap  136  between the sides of each pyrotechnic composition  132  and the launch tube or barrel  102 . The specific chemical structure of each pyrotechnic composition  132  is selected based on conventional parameters such as desired combustion color, effects, or combustion duration. 
   One or more ignition sources  140 , such as an electric igniter or primer cord are passed through a igniter passage  142  in the enclosed base  102 , preferable disposed above the shoulder  122  and gas sealing disk  124 , and adjacent an outer surface of the pyrotechnic composition  132  and optional pyrotechnic prime composition  127  disposed on the gas sealing disk upper surface  128 . Additional ignitions sources may optionally be similarly disposed adjacent the outer surfaces of each additional pyrotechnic composition  132  present in the combustion chamber  108 . 
   Finally, a closure cap or burst disk  144 , preferably composed of paper, is fittingly seated within the launch tube or barrel  102 , between the uppermost pyrotechnic composition  132  and the open discharge end  106 , thereby retaining the installed components within the launch tube or barrel  102  during storage and transportation. 
   During use, the previously described components are assembled within the enclosed base  104  and launch tube or barrel  102  in a logical and sequential manner, as dictated by the manner in which the components are to be propelled from the open discharge end  106 . 
   To discharge the smokeless pyrotechnic display device  100  of the present invention, the one or more ignition sources  140  are utilized to igniting the pyrotechnic compositions  132  and optional prime composition  127  within the combustion chamber  108 . The optional pyrotechnic prime composition  127  is disposed in combustion proximity to the pyrotechnic composition  132  facilitating propagation of flame over the exposed surfaces of the adjacent pyrotechnic composition  132  within the combustion chamber  108 . 
   Following flame propagation over the surfaces of the pyrotechnic compositions  132 , the combustion delay component  130  separating the pyrotechnic composition  132  from the smokeless pyrotechnic propellant  120  burns through. Continued combustion of the pyrotechnic compositions  132  results in the igniting of the smokeless pyrotechnic propellant  120  through the now-exposed axial bore or passage  126  in the gas sealing disk  124 , and the expelling of the ignited pyrotechnic compositions  132  from the discharge end  106  of the launch tube or barrel  102 . 
   Turning to  FIG. 3  and  FIG. 4 , a second embodiment of the pyrotechnic display device  200  of the present invention is illustrated. The pyrotechnic display device  200  consists of a launch tube or barrel  202  having a generally cylindrical configuration and an enclosed base  204 . The launch tube or barrel  202  preferably formed from spiral wound paper having an open discharge end  206 , but may consist of any of a wide variety of materials having sufficient strength to maintain a shape during ignition and combustion of the pyrotechnic display device  200 . The enclosed base  204  is preferably formed from a molded plastic, defining a open-ended combustion chamber  208 , and is configured for attachment to the launch tube or barrel  202 , opposite the open discharge end  206 . 
   As illustrated in  FIGS. 3 and 4 , the enclosed base  204  is generally cylindrical, having a uniform inner radial dimension RA, and a uniform outer radial dimension RB. An annular recessed region  210  is provided adjacent an open end  212  of the combustion chamber  208 . The annular recessed region  210  maintains the uniform inner radial dimension R1, but has a reduced uniform outer radial dimension R3, sized to receive the inner cylindrical surface  214  of the launch tube or barrel  202 , having an inner radial dimension R4, in an interference fit, abutting an annular ridge  216  on the outer surface  218  of the enclosed base  204 . 
   Those of ordinary skill in the art will recognize that the enclosed base  204  may optionally be constructed integrally with the launch tube or barrel  202 , or coupled thereto in a variety of different manners, and may consist of any of a variety of shapes and sizes, depending upon the particular application for which the pyrotechnic device  200  is to be utilized. 
   A smokeless lift charge or pyrotechnic propellant  220 , preferably nitrocellulose, is placed within combustion chamber  208  of the enclosed base  204 . The quantity of smokeless pyrotechnic propellant  220  is selected in a conventional manner, based upon the combustion characteristics of the smokeless pyrotechnic propellant  220  and the particular loads which are intended to be ejected from the launch tube or barrel  202 . 
   Disposed above the level of the smokeless pyrotechnic propellant  120  within the combustion chamber  208  of the enclosed base  204 , a radially inward projecting shoulder  222  supports a gas sealing disk  224 . The gas sealing disk  224  is sized to fit securely within the combustion chamber  208  when seated on the shoulder  222 . Optionally, a conventional pyrotechnic prime composition  127  is deposited on an upper surface  226  of the gas sealing disk, opposite from the smokeless pyrotechnic propellant  220 . 
   Next, one or more pyrotechnic compositions  228  are disposed within the combustion chamber  208 , with the initial pyrotechnic composition  228  seated on the upper surface  226  of the gas sealing disk  224 . Each pyrotechnic composition  228  is preferably formed as a pressed solid, and includes a open central core  230 . The outer radial dimensions of each pyrotechnic composition  228  is selected to be smaller than the inner radial dimension Rd of the launch tube or barrel  202 , thereby providing a combustion facilitating air-gap  232  between the sides of each pyrotechnic composition  228  and the launch tube or barrel  202 . The specific chemical structure of each pyrotechnic composition  228  is selected based on conventional parameters such as desired combustion color, effects, or combustion duration. 
   Two or more ignition sources  234 , such as an electric igniter or primer cord are passed through associated igniter passages  236  in the enclosed base  202 . One ignition source  234  and associated igniter passage  236  is disposed below the shoulder  222  and gas sealing disk  224 , in proximity to the smokeless pyrotechnic propellant  122 . At least a second ignition source  234  and associated igniter passage  236  is disposed above the shoulder  222  and gas sealing disk  224 , adjacent an outer surface of the lowest pyrotechnic composition  228  and optional pyrotechnic prime composition  127  disposed on the gas sealing disk upper surface  226 . Additional ignitions sources may optionally be similarly disposed adjacent the outer surfaces of each additional pyrotechnic composition  228  present in the combustion chamber  208 . 
   Finally, a closure cap or burst disk  238 , preferably composed of paper, is fittingly seated within the launch tube or barrel  202 , between the uppermost pyrotechnic composition  228  and the open discharge end  206 , thereby retaining the installed components within the launch tube or barrel  202  during storage and transportation. 
   During use, the previously described components are assembled within the enclosed base  204  and launch tube or barrel  202  in a logical and sequential manner, as dictated by the manner in which the components are to be propelled from the open discharge end  206 . 
   To discharge the smokeless pyrotechnic display device  200  of the present invention, the one or more ignition sources  234  disposed above the gas sealing disk  224  are utilized to igniting the pyrotechnic compositions  228  and optional prime composition  127  within the combustion chamber  208 . The optional pyrotechnic prime composition  127  is disposed in combustion proximity to the lowest pyrotechnic composition  228  facilitating propagation of flame over the exposed surfaces of the adjacent pyrotechnic composition  228  within the combustion chamber  208 . 
   Following flame propagation over the surfaces of the pyrotechnic compositions  228 , or after a predetermined time delay, the ignition source  234  disposed below the gas sealing disk  224  and in proximity to the smokeless pyrotechnic propellant  220  is utilized to ignite the smokeless pyrotechnic propellant  220 . Combustion of the smokeless pyrotechnic propellant  220  results in the expelling of the ignited pyrotechnic compositions  228  from the discharge end  206  of the launch tube or barrel  202 . Utilization of the ignition source  234  disposed below the gas sealing disk  224  allows for precision timing in the launching of the device  200 , and does not rely on the potentially random combustion of priming compositions or delay elements. 
   In an alternate embodiment of the present invention, the pyrotechnic compositions  132  and  228  may be replaced with aerial shells  300 , such as shown in  FIG. 5 . An aerial shell  300  preferably consists of a non-burning body  302 , formed from plastic or paper materials, defining a hollow chamber  304  within which are disposed one or more burst charges or pyrotechnic stars  306 . A delay fuse  308  protrudes through the non-burning body  302 . During use or discharge, the delay fuse  308  of the aerial shell  300  is ignited first, followed by ignition of the smokeless pyrotechnic propellant  120 ,  220  as previously described either from burn-through of a combustion delay element  130  or a separate igniter  234 . The resulting combustion of the smokeless pyrotechnic propellant  120 ,  220  launches the aerial shell  300 . Preferably, the delay fuse  308  is selected to ignite the burst charges or pyrotechnic stars  306  at the apex of the aerial shell flight path, bursting the non-burning body  302  either along frangible lines, or by detaching a removable cap  310 , providing the desired pyrotechnic display. 
   In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results are obtained. As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.