Abstract:
A two-piece reusable shell for use with launching systems. The launcher shell has a top tube portion that screws onto a base portion, which houses an ignition source and a propellant. The reusable shell allows for efficient access to all portions of the shell and for easy interchangeability between tubes of differing lengths and one standard base unit.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    Previously filed Provisional Application No. 61/345,871 on May 18, 2010 . 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable. 
       REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISC APPENDIX 
       [0003]    Not Applicable. 
       BACKGROUND OP THE INVENTION 
       [0004]    The present invention relates to ammunition and explosives. More specifically, it relates to a cartridge case for thirty-seven millimeter launchers. Thirty-seven millimeter (37 mm) launchers have been in use for nearly a century. These devices have found a multitude of uses, ranging from flare launching to destructive device launching. Playing a prominent role in both the first and second World Wars, 37 mm launchers have been proven capable of taking out tanks and aircraft. While the power and destructive capacity of 37 mm launchers is undeniable, there are a large number of applications for these launchers that do not involve destruction. These launchers are often used to propel smoke rounds, flares, fireworks or noise effect rounds. Given the large variety of uses for a 37 mm launcher, there is a large hobbyist following. 
         [0005]    Under the National Firearms Act, 37 mm launchers are only classified as “destructive devices” if the launchers dispense rounds capable of causing destruction (for example, any projectile that could shatter and dispense shrapnel). If used for activities such as launching smoke rounds or noise effects, they are not considered “destructive devices” and avoid the requirement of being registered with the federal government. 
         [0006]    Thirty-seven millimeter launchers come in a variety of configurations, ranging from stand-alone launchers to under barrel attachments for rifles. Regardless of the launcher configuration, operation is the same. A shell must be inserted, fired, and then discarded before another shell can be inserted and fired. Many 37 mm launcher system users reuse fired shells time and again. The current process for the preparation and reloading of the spent shells is tedious and painstaking. The present invention addresses the shortcomings of the current shell reuse process. 
       BRIEF SUMMARY OF THE INVENTION 
       [0007]    Thirty-seven millimeter launching systems are capable of launching shells of differing heights. Most commonly, shells are seen in heights of 2.25″, 3.75″ and 5″, but can reach heights of up to 8.5″. Because the shell housing is typically not damaged in the firing of the shell&#39;s payload, they are often reused repeatedly. The differing heights of the shells make it difficult to use a single uniform tool set to remove the spent primer (or blank), insert a new primer (or blank), insert the propellant (typically black powder or a black powder equivalent), insert the fused payload tube and payload, and seal the tube and shell. 
         [0008]    The difficulty in the process arises from the fact that the shells are of a single, unibody design and shape. The current shells do not give easy access to the primer or blank ammo for replacement and do not give easy access to the lift charge. Current 37 mm shells are long, requiring the use of a thin punch to remove the primer or blank for replacement. It is difficult and time consuming to get the punch directly over the ignition source before applying pressure. The shell is not comprised of multiple pieces, each of which could be dismantled for ease of access during the reloading process. The present invention, unlike the prior art, is comprised of a two-piece shell system. The present invention has a detachable threaded base that will screw into a shell cylinder of any desired height. With the detachable thread base, it is possible to remove the spent primer with the same tool each time, as the height of the shell cylinder is no longer a factor. The method for adding the propellant is also improved, as the propellant can be added directly to the base, without the need for a funnel to convey the propellant to the base, as in conventional shells. With the present invention, it is also possible to verify the proper contact of the payload tube fuse with the propellant, if needed. The two-piece shell reduces the complexity of reusing and reloading of previously fired 37 mm launcher shells, while adding the additional capability of using the same base with any desired height shell cylinder. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0009]      FIG. 1 . Top View of Threaded Shell Base. 
           [0010]      FIG. 2 . Side View of Threaded Shell Base. 
           [0011]      FIG. 3 . Bottom View of Threaded Shell Base. 
           [0012]      FIG. 4 . Cross Section of Threaded Shell Base. 
           [0013]      FIG. 5 . Exploded Perspective View of Shell Assembly. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]    The present invention, a 37 mm screw apart shell, is an improvement on existing 37 mm launcher shells. The same improvement also applies to 40 mm launcher shells. The present invention is comprised of two items: a circular threaded base and a 37 mm tube that is threaded on one end to accept the threaded base. 
         [0015]    The threaded base is comprised of three components: the opening to house an ignition source such as a blank or a primer, a bowl to house propellant such as black powder or a black powder equivalent, and a threaded portion to mate with the tube. 
         [0016]    The ignition source for a 37 mm shell is typically a 209 shotgun primer. The 209 shotgun primer is commercially available and is an industry standard primer used in many applications. The threaded base of the present invention has a circular opening in the center of the bottom face of the base. The circular opening is of such a diameter that a 209 shotgun primer can be inserted and press-fit into the opening remaining in place after insertion. In an alternative embodiment of the present invention, a blank cartridge may be substituted for a 209 shotgun primer (diameter of bottom face opening would be such that the blank cartridge would fit and remain in place after insertion). The opening in the bottom face of the base terminates at the propellant bowl. 
         [0017]    The propellant bowl is a revolved “u”-shaped depression in the threaded base. The walls of the chamber are smooth and without striations. At the center of the bottom of the bowl is the opening where an ignition source would be housed. The bowl is of such size that it will hold 50 grains of black powder (FFFG Grade). If desired, a cover disk can be inserted atop the black powder inside the bowl to provide a greater propulsive force. 
         [0018]    The threaded portion of the base is on the outside edge of the propellant bowl chamber. The threads are on the exterior face (male portion) designed such that engagement with the tube threads (female portion) will result in a uniform outer diameter extending the full length of the tube and base, up to the base flange. The threads are machined as a part of the base unit. 
         [0019]    The 37 mm launcher screw apart shell base threads into the shell tube. The tube may be of varied length, depending on the desired shell application. The walls of the tube are of a constant thickness and are of a smooth, non-bored consistency, with the exception of the threading on the lower portion of the tube. The interior face of the bottom of the tube is threaded to mate with the exterior face of the shell base in such a manner that when assembled, the interior of the tube has a smooth and clean finish, not interfering with the launching of the payload. 
         [0020]    When assembling the present invention, the ensuing methods should be followed. The two-piece assembly should be unscrewed in such a manner that the user is left with a base separately detached from the tube. The base and tube should be inspected for damage prior to use. If damage is noted, shell should not be used. Once inspected, a new 209 shotgun primer should be inserted into the base and pressure applied until primer is lodged inside base. Once the primer is secure, black powder or black powder equivalent (i.e., Pyrodex) is measured and poured into propellant bowl. If desired, propellant bowl should be sealed with a base disk, which is lodged into inside edge of propellant bowl. Tube is screwed onto base tightly. Once shell is formed in its entirety, the payload tube and payload can be inserted into the shell and prepared for launch. Upon firing, shell is removed from launcher and the two portions of shell should be unscrewed. Pressure should be applied to previously fired 209 shotgun primer from the inside of the propellant bowl until primer becomes dislodged from base. Both portions of shell should be inspected for damage. If no damage is noted base should be thoroughly cleaned before continuing. Once clean, procedure for assembly is repeated as detailed above. 
         [0021]    The preferred embodiment of the present invention uses 6061-T6 aluminum for all portions of the shell. However, alternative embodiments could be formed from a variety of materials (including, but, not limited to, other metals, metal alloys, composites, or plastic). The tube is manufactured from either thick-wall tubing or solid cylindrical stock. The base is formed out of solid cylindrical stock. Both pieces are individually shaped and formed on a lathe, and assembled upon completion of forming. 
         [0022]    As many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing form the scope thereof, 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 limited sense. 
         [0023]    It is also to be understood that the language used in the claims is intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention, which, as a matter of language, might be said to fall therebetween.