Patent Publication Number: US-7908971-B2

Title: Propellant charge for recoilless gun

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to European patent application 07117803.2 filed 3 Oct. 2007. 
     BACKGROUND OF THE INVENTION 
     1. Technical Field of the Invention 
     The present invention relates to a propellant charge for a recoilless gun. More particularly, the invention relates to a propellant charge which is mainly adapted for a round of a reloadable support weapon, as the M3 Carl Gustaf, in order to prevent the charge from breaking into peaces and powder grains from moving around in the combustion chamber during transport, handling and firing of the rounds. 
     2. Description of Related Art 
     In conventional rounds of the initially mentioned kind the propellant charge might consist of powder grains or strips which are loosely applied with no support in the combustion chamber of the casing of the round. 
     Hence, a propellant charge comprising loosely applied powder grains or strips with no support might be broken, divided into pieces, dispersed and/or moved around in the combustion system of the round during transport and handling. 
     Further, during the combustion powder fragments might be transported between different parts of the combustion system, which makes it uncertain where and when the combustion takes place. 
     Consequently, the process of combustion would not be predictable and a uniform process of combustion not guarantied, which might result in residual powder fouling of barrel being thrown out together with the combustion gases. 
     Hitherto, several attempts have been made to keep the strips in place by means of rubber bands or similar devices. Further, for example the document U.S. Pat. No. 3,967,558 discloses a support structure for supporting perforated strips in a radial cylindrical configuration by support rings. Unfortunately, the charge- and combustion chambers of said round, to which the propellant charge according to the present invention be adapted, is formed as a relatively thin cylindrical slot, which means there is too little space for the use of perforated strips supported in a radial cylindrical configuration by support rings, e.g. as is described in U.S. Pat. No. 3,967,558. 
     Therefore, so far the results of said attempts have been unsatisfactory and up till now the related technical field lacks a suitable solution to this problem. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an improved propellant charge solution which does not suffer from the drawbacks in the related art. 
     For this purpose, a propellant charge according to the present invention, is characterized in that said propellant charge is cylindrically shaped and adapted for loading into a combustion chamber formed between an inner casing and an outer casing of said round. 
     Further objects, improvements and developments appear from the dependent claims and the description with reference to the accompanying schematic drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view depicting an example of a propellant charge embodied by a tubular formed powder sheet and elements of its holding fixture as adapted to fit with the inner casing of the casing assembly, the outer casing be excluded, 
         FIG. 2  is a view as  FIG. 1  depicting said powder sheet attached to the inner casing by means of the holding fixture, 
         FIG. 3  is a longitudinal section of the casing assembly completed with the outer casing enclosing the powder sheet and sealing off the charge- and combustion chambers, 
         FIG. 4  is an enlarged, non-proportional section cut through lines A-B of the casing assembly in  FIG. 3 , 
         FIG. 5  is a view like  FIG. 4  which discloses a development of the propellant charge. 
     
    
    
     DESCRIPTION OF EMBODIMENT OF THE INVENTION 
     In stead of loose powder grains the charge according to the invention is made in the form of a solid propellant charge, which is stationary arranged in a casing assembly of a round. 
       FIG. 1  is an exploded perspective view depicting an example of an inner casing  2  and a propellant charge  4  embodied by a cylindrical cartridge configured by a tubular formed powder sheet  4  and a holding fixture  6  for said powder sheet as adapted to fit with said inner casing  2  of said assembly. It is desirable the charge be configured from at least one sheet  4  of powder in correspondence with the actual size of the available space or clearance in the assembly. Hereby, said sheet of powder can be pushed into, and simultaneously bent into the desired configuration to fit with, said holding fixture  6 . The sheet  4  is hereby arranged to be extended over essentially the entire circumference of the inner casing  2 , which means a holding grip can be exerted by the holding fixture in both radial and longitudinal directions of the so configured powder sheet  4 , which will be described in more detail in the following. 
     Therefore, in the present case the charge  4  might be configured according to a first embodiment by just one thickness of powder sheet as a single layer tubular formed powder sheet  4 , as disclosed in  FIGS. 1 ,  2  and  4 , or a plurality of coaxially arranged layers according to a second embodiment, which will be described in more detail later. For this purpose, in the embodiments first and second fastening elements  8 ,  10  and spacer elements  12  might be provided, for making up said holding fixture  6 , which will also be described in more detail later. The inner casing  2  is of a conventional design used in e.g. a reloadable, recoilless support weapon as the M3 Carl Gustaf, and is therefore not described further here. Said powder sheet  4  can be initiated by an ignition device conventionally used in this kind of weapons. A prior art recoilless weapon of this kind is for example described in U.S. Pat. No. 6,971,299. 
       FIG. 2  is a view similar to  FIG. 1  disclosing said first embodiment and depicting said powder sheet  4  attached to the inner casing  2  by means of said first fastening elements  8 , here anchor pins  8  and said second fastening elements  10 , here braces  10 . It appears that the powder sheet  4  is arrested by means of said braces  10 , which are bent around the powder sheet  4  and extended over longitudinal pieces of its envelope surface. The anchor pins  8  are extended in through bores of the braces  10  and firmly connected, e.g. riveted or bolted, to the inner casing  2 . 
       FIG. 3  is a longitudinal section of the casing assembly, the inner casing  2  completed with an outer casing  14  enclosing the powder sheet  4 . Further, it appears that a charge chamber  16  widens into a combustion chamber  18 , which both are enclosed and sealed off relative to the inner casing  2  by said outer casing  14 . Furthermore, the powder sheet  4  can be seen, located in the charge chamber  16  and in a holding grip of its holding fixture  6 . Said combustion chamber  18  is conventionally associated with the inside of the inner casing  2  by means of nozzles  20 . 
       FIG. 4  is an enlarged, non-proportional section cut through lines A-B of the casing assembly in  FIG. 3 . It appears that the tubular formed powder sheet  4 , by means of each anchor pin  8  and each brace  10 , is arrested in position in the charge chamber  16 , formed between the inner casing  2  and the outer casing  14 . It is also evident that the charge chamber  16  mergers into the combustion chamber  18 , and is associated with the inside of the inner case by said nozzles  20 , one of which is disclosed. The powder sheet  4  is shown with a relatively large thickness, however it might be varied appropriately to meet different demands of pressure, within the limits given by the available space in said chambers. 
       FIG. 5  discloses a view similar to  FIG. 4  of a second embodiment of the present invention. In addition to the first and second fastening means  8  (anchor pins) and  10  (braces) respectively, in the second embodiment even the spacer elements  12  are used to make up the holding fixture  6 . Accordingly, in said second embodiment a combined propellant charge  22  might be configured by a plurality of coaxially arranged powder sheets  4 , each comprising a single layer tubular formed powder sheet and fitting close upon each other. 
     For this purpose, in this embodiment three powder sheets are combined to make up said charge  22 , an outer powder sheet  4 ′, a middle powder sheet  4 ″ and an inner powder sheet  4 ′″ are shown with a relatively narrow thickness. The outer sheet  4 ′″ is spaced from the middle sheet  4 ″ and the middle sheet  4 ″ from the inner sheet  4 ′″ by means of a spacer element  12  each. The spacer elements  12  and each brace  10  are attached to the inner casing  2  by means of the anchor pins  8 . It appears that the combined charge  22  is arrested by means of said braces  10 , as bent around all of the powder sheets  4 ′,  4 ″ and  4 ′″ and extended over longitudinal pieces of their envelope surfaces. Even in this embodiment, the anchor pins  8  are extended in through bores of the braces  10  and spacer elements  12  and firmly connected, e.g. riveted or bolted, to the inner casing  2 . 
     Hence, by means of the spacer elements  12 , which might be of an appropriate thickness to facilitate uniform ignition of the powder tubes by means of a conventional ignition system, it is achievable that less powder residues are let out to the environment. 
     It is noted, that the combined charge  22  can be adapted by varying the number and thickness of powder sheets  4 ′,  4 ″,  4 ′″ even if they are shown with a relatively small thickness at a number of three. However, even in this embodiment consideration must be done to ensure any adaptation would be appropriate to meet different demands of pressure, within the limits given by the available space in said chambers.