Abstract:
A propellant charge batch for an explosion-operated setting tool includes a socket member ( 10 ) in an inner space which there are provided a first chamber ( 11 ) filled with a nitrocellulose propellant charge ( 13 ), and a second chamber ( 12 ) filled with an ammoniumnitrate powder ( 14 ), with at least the second chamber ( 12 ) being closed medium tightly; and at least one ignition element ( 15 ) for igniting the propellant charge.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a propellant charge batch for explosion-operated setting tool and including a socket member the inner space of which is filled with a propellant charge, and at least one ignition element.  
           [0003]    2. Summary of the Invention  
           [0004]    The propellant charge batches of the type described above are formed, e.g., as cartridges or blisters filled with a powdered propellant charge.  
           [0005]    The propellant charge batches of the above-described type are used in, e.g., bolt setting tools and serve as drive means for the tool drive piston.  
           [0006]    A propellant charge batch of the above-described type is disclosed, e.g., in a German Publication DE-39 10 392 A1. In the disclosed batch, the propellant charge is located in a hollow space of a cartridge-shaped receptacle, with the ignition element being located in a sidewise recess formed in the receptacle.  
           [0007]    It is desirable to use in the propellant charge batches, a propellant charge powder which is free of harmful substances to a most possible extent. The powder, which is used presently, is, however, relatively expensive and produces slag which is highly undesirable in contemporary bolt setting tools and which cannot be removed.  
           [0008]    From the environmental point of view, the most favorable propellant charge component is ammoniumnitrate which, after being consumed in the setting tool, does not release any toxins and releases only gaseous reaction products. The drawback of the ammoniumnitrate consists in that it is highly hygroscopic.  
           [0009]    U.S. Pat. No. 3,753,810 discloses a shelled propellant powder on basis of nitrocellulose and ammoniumnitrate. With this propellant powder, the grains or granules are provided, for protection against moisture, with a nitrocellulose outer coating containing at least aluminum in a powder form. The method of manufacturing such a propellant charge is very expensive, which makes the powder very expensive.  
           [0010]    Further, with strong temperature variations during charging, because of a phase change, the aluminum coat becomes lost.  
           [0011]    Accordingly, an object of the present invention is to provide a propellant charge batch of the type discussed above, e.g., such as a cartridge in which the drawbacks of the prior art are eliminated.  
         SUMMARY OF THE INVENTION  
         [0012]    This and other objects of the present invention, which will become apparent hereinafter, are achieved by providing a propellant charge batch having a socket member in an inner space of which there are provided a first chamber filled with a nitrocellulose propellant charge, and a second chamber filled with ammoniumnitrate powder, with at least the second chamber being closed medium tightly, and ignition means for igniting the propellant charge.  
           [0013]    According to the invention, the nitrocellulose propellant can be in a pasty, granular, powder, fiber or the like form and can include or not include different additives such as, e.g., nitroglycerine.  
           [0014]    The nitrocellulose propellant, which is contained in the propellant charge batch or cartridge is easily ignited, and its amount is so adapted to the ammoniumnitrate powder that, advantageously, a neutral oxygen balance is achieved. This is energetically advantageous and prevents an eventual corrosion of the tool which could result from an excess of oxygen. Because the ammoniumnitrate powder is separated from the nitrocellulose propellant, the ignition of the nitrocellulose powder is not affected by an undefined distribution of the ammoniumnitrate powder in the nitrocellulose propellant. Further, the separation of the ammoniumnitrate powder from the nitrocellulose propellant insures a predetermined filling of the propellant charge batch or the cartridge during manufacturing. Still further, the change of the volume of the ammoniumnitrate as a result of a phase change becomes irrelevant because the grains of the nitrocellulose are not affected due to the separation of the ammoniumnitrate and the nitrocellulose propellant. Further, the separation of the ammoniumnitrate and the nitrocellulose propellant provides for a complete water-tight packing of the ammoniumnitrate. As a result, the harmful hygroscopicity of the ammoniumnitrate also becomes irrelevant. Thus, there is provided a propellant charge batch which is environment-friendly and is characterized by a high propelling power.  
           [0015]    According to an advantageous embodiment of the present invention, both chambers are arranged one after another in the axial direction of the socket member. Advantageously, the ignition means is arranged in the region of the bottom of the propellant charge batch, with the nitrocellulose propellant being located in the chamber which is adjacent to the ignition means, and ammoniumnitrate powder being located in the frontmost chamber remote from the ignition means. With such an arrangement, the ignition means, the nitrocellulose propellant, and the ammoniumnitrate form an ignition chain. The ignition condition for the ammoniumnitrate are particular good for ammoniumnitrate with the present invention. 200 J of an ignition energy provide for a temperature of about 2,500° C., a pressure of about 100 bar, and a high flow velocity. After ignition, e.g., in a setting tool, the mixture of a combusting nitrocellulose propellant and ammoniumnitrate is intermixed during the combustion for a long time, e.g., in a swirl chamber. An extended intermixing favorably influences the combustion process. Advantageously, during the combustion process, the combustion volume is maintained substantially constant. The combustion with a substantially constant volume and a high propellant density is very favorable for conversion of the entire propellant charge.  
           [0016]    According to a further advantageous embodiment of the present invention, the two chambers are separated from each other by a separating element. This simplifies the manufacturing process and, thus, facilitate the production of the inventive propellant charge batch.  
           [0017]    According to another advantageous embodiment of the present invention, the separating element is formed as a disc-shaped element of a nitrocellulose board. Because the nitrocellulose board is combustible, no problem associate with a possible residue of the separation element exists.  
           [0018]    According to a still further advantageous embodiment of the present invention, the propellant charge batch is formed as a blister or a blister cartridge, i.e., the socket member is formed of a blister film or foil. The formation of the batch of the blister film insures a cost-effective manufacturing of the batches. Another advantage of using a blister film consists in that the film is easily opened by the propellant upon combustion.  
           [0019]    According to yet another advantageous embodiment of the present invention, the separation element is formed as a cup-shaped element of a film material, e.g., a blister film or foil. This separation element is particularly suitable for use in a blister cartridge, as the socket member and the separating element can be welded or glued to each other in their end regions, which insures a proper sealing of the two chambers relative to each other.  
           [0020]    The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiments, when read with reference to the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS:  
       [0021]    The drawing show:  
         [0022]    [0022]FIG. 1 a longitudinal cross-sectional view of a first embodiment of a propellant charge batch according to the present invention; and  
         [0023]    [0023]FIG. 2 a longitudinal cross-sectional view of a second embodiment of a propellant charge batch according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]    A propellant charge batch according the present invention, which is shown in FIG. 1, is formed as a socket member  10  the inner space of which is divided in two chambers  11 ,  12 . A propellant charge, which is contained in the propellant charge batch, consists of nitrocellulose means  13 , e.g., a nitrocellulose powder, which is located in the chamber  11 , and an ammoniumnitrate powder  14  which is located in the chamber  12 . The chambers  11  and  12  are arranged one after another in an axial direction  20 , with the chamber  11  being limited by the bottom  17  of the propellant charge batch. At the bottom  17 , the socket member  10  is closed, preferably, by a medium/liquid tight cover  18 . In the embodiment shown in FIG. 1., both the socket  10  and the socket cover  18  are formed of a plastic material. However, they also can be formed of metal or any other suitable material. It should be understood that the graininess of the ammoniumnitrate can vary from fine-grained to coarse-grained.  
         [0025]    In the region of the bottom  17 , the socket member  10  is provided with a salient edge region  19  with which the propellant charge batch can be supported on flanks of a cartridge support of a setting tool (not shown). In the empty space of the salient edge region, ignition means  15  is located.  
         [0026]    The two chambers  11 ,  12  are separated from each other, in the embodiment shown in the drawing, by a medium tight separating element  16 . 1  formed, in the embodiment shown in FIG. 1, as a plate cut out from a nitrocellulose board.  
         [0027]    Upon ignition of the propellant charge batch with the ignition means  15  which is ignited by an ignition device of the setting tool, firstly, the nitrocellulose propellant means  13  is ignited. With the ignition of the nitrocellulose propellant means  13 , the separating plate  16 . 1  is teared open and is pressed back. The separating plate  16 . 1  takes part in the combustion and is completely consumed, so that no residue remains. As a result of the pressure of combustion, the propellant charge batch or cartridge opens in its front region, so that the ammoniumnitrate powder  14  becomes mixed with a remaining nitrocellulose propellant means  13 , which results in an optimal combustion of the propellant charge. The intermixing of the ammoniumnitrate powder  14  with the remaining portion of the nitrocellulose propellant means  13  is enhanced by providing in the setting tool, downstream of the cartridge support, of a swirl chamber. The combustion is effected without release of toxic substances and without formation of slag.  
         [0028]    During filling of the chamber  12 , the ammoniumnitrate powder  14  is protected from penetration of moisture as a result of the chamber  12  being closed.  
         [0029]    The propellant charge batch shown in FIG. 2 differs from that of FIG. 1, in that the socket member  10  is formed of a rigid plastic film (blister foil). The socket cover  18  is formed of a thin foil that can be, optionally, metal-plated. The separating element  16 . 2 , which separates the chamber  11  with the nitrocellulose propellant means  13  and the chamber  12  with the ammoniumnitrate powder  14 , is formed of a cup-shaped blister foil having an edge region that overlaps the edge region  19  of the socket member  10  and is welded or glued thereto. The ignition means  15  is located separately. Upon ignition of the propellant charge batch, the ignited nitrocellulose bursts the films, which form the separating element  16 . 2  and the socket member  10 , in the front region of the chamber  11 . As it was described above, the nitrocellulose propellant means  13  intermixes subsequently with the ammoniumnitrate powder  14 , with the mixture having been completely combusted, without leaving any toxic reaction products.  
         [0030]    When the propellant charge batches are arranged in a magazine, the edge regions  19  of the adjacent propellant charge batches are connected with each other forming a magazine strip. A cartridge according to the present invention can be also formed as a one-piece element, with the socket member having an integral bottom and with the front socket opening of the cartridge being closed and sealed.  
         [0031]    Though the present invention was shown and described with references to the preferred embodiments, such are merely illustrative of the present invention and are not to be construed as a limitation thereof and various modifications of the present invention will be apparent to those skilled in the art. It is, therefore, not intended that the present invention be limited to the disclosed embodiments or details thereof, and the present invention includes all variations and/or alternative embodiments within the spirit and scope of the present invention as defined by the appended claims.