Abstract:
A venting system for ordnance or rocket motors comprising a casing having at least one hole and a plug, the plug being formed from a plug slug swaged into the at least one hole. A method to fill a vent hole in a casing comprising transforming a plug slug positioned within the vent hole into a plug.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    Not Applicable 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
       [0002]    The U.S. Government has a paid-up license in this invention and the right in limited circumstances to require the patent owner to license others on reasonable terms as provided for by the terms of Contract No. W15QKN-05-C-1171 awarded by the Department of the Army. 
       FIELD OF THE INVENTION 
       [0003]    This invention relates to the field of venting ordnance, rocket motors, and warheads. 
       BACKGROUND OF THE INVENTION 
       [0004]    Ordnance and rocket motors contain energetic materials such as explosives. These energetic materials can ignite in an unplanned manner due to internal pressure, excess heat, or other conditions. Venting of ordnance, rocket motors, and warheads can reduce the unplanned ignition of these energetic materials. 
       BRIEF SUMMARY OF THE INVENTION 
       [0005]    A venting system for ordnance, rocket motors, or warheads comprising a casing having at least one hole and a plug, the plug being formed from a plug slug swaged or crimped into the at least one hole. 
         [0006]    A method to fill a vent hole in a casing comprising transforming a plug slug positioned within the vent hole into a plug. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a perspective view of a casing with a hole. 
           [0008]      FIG. 2  is a cross-sectional view of an embodiment of a hole in a casing. 
           [0009]      FIG. 3  is a cross-sectional view of a plug in the hole shown in  FIG. 2 . 
           [0010]      FIG. 4  is a cross-sectional view of a plug in the hole shown in  FIG. 2 . 
           [0011]      FIG. 5  is a cross-sectional view of an embodiment of a hole in a casing with a plug therein. 
           [0012]      FIG. 6  is a cross-sectional view of an embodiment of a hole in a casing with a plug therein. 
           [0013]      FIG. 7  is a cross-sectional view of an embodiment of a hole in a casing with a plug therein. 
           [0014]      FIG. 8  is a cross-sectional view of a plug slug being swaged or crimped into the hole shown in  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]    While this invention may be embodied in many forms, there are described in detail herein specific embodiments of the invention. This description is an exemplification of the principles of the invention and is not intended to limit the invention to the particular embodiments illustrated. 
         [0016]    For the purposes of this disclosure, like reference numerals in the figures shall refer to like features unless otherwise indicated. 
         [0017]      FIG. 1  shows an example of a casing  2  that is configured to contain materials that can explode or ignite. Non-limiting examples of casings include an ordnance casing, a casing of a rocket motor, or a casing for a warhead. In one embodiment, the casing is the casing of a 120 mm XM 395 Precision Guided Mortar Munition warhead. 
         [0018]    As shown in  FIG. 2 , the casing  2  has a first surface  4 , a second surface  6 , and at least one hole  8 . In some embodiments, the first surface  4  is the outer surface of the casing and the second surface  6  is the inner surface of the casing. In other embodiments, the first surface  4  is the inner surface of the casing and the second surface  6  is the outer surface of the casing. It is within the scope of the invention for the casing  2  to have one, two, three, four, five, six, or more holes  8 . Each hole  8  extends from the first surface  4  of the casing  2  to the second surface  6  of the casing  2 . The hole  8  can be described as a venting area or vent hole. Although the hole  8  in  FIG. 1  is substantially round-shaped, it is within the scope of the invention for the hole  8  to have any shape, for example, square shaped or rectangular shaped. 
         [0019]    As shown in the cross-sectional view of  FIG. 2 , the hole  8  has a width (W H ) as measured across the hole, and a thickness (T H ) measured from the first surface  4  of the casing  2  to the second surface  6  of the casing  2 . The hole width (W H ) is about 6 mm to about 50 mm. The hole thickness (T H ) is about 3 mm to about 25 mm. 
         [0020]    Although  FIG. 2  shows a hole  8  with one groove  10 , it is within the scope of the invention for the hole  8  to have one, two, three, four, or more grooves  10 . It is also within the scope of the invention for the hole  8  to have no grooves, as shown in  FIG. 7 . An example of a hole with multiple grooves is the hole  8  shown in  FIG. 6  which has two grooves  10 . It is also within the scope of the invention for the groove(s)  10  to have any position(s) between the first and second surfaces  4 , 6  of the casing  2 . For example, the groove  10  in  FIG. 4  is substantially midway between the first and second surfaces  4 , 6  of the casing  2 , while the groove  10  shown in  FIG. 5  is adjacent to the first surface  4  of the casing  2 . In  FIG. 6 , the hole  8  has one groove  10  that is adjacent to the first surface  4  of the casing  2  and another groove  10  that is adjacent to the second surface  6  of the casing  2 . 
         [0021]    In at least one embodiment, the groove  10  extends about the entire perimeter of the hole  8 . In some embodiments, the groove  10  extends about only a portion of the perimeter of the hole  8 . In this embodiment, the groove  10  can be described as a notch groove. The hole  8  shown for example in  FIG. 2  may also be described as showing a cross-section of a hole with two notch grooves that are positioned opposite one another. It is within the scope of the invention for a hole to have grooves, notch grooves, and any combination thereof. 
         [0022]    Each groove  10  and each notch groove has a width. It is within the scope of the invention for a groove  10 , or a notch groove, to have any width. In the figures the width of a groove is indicated by W G . In at least one embodiment, the groove width (W G ) is greater than the hole width (W H ), as shown, for example, in  FIG. 2 . In some embodiments, the groove width (W G ) is about equal to the hole width (W H ) to about equal to the hole width+6 mm (W H +6 mm). In other embodiments, the groove width (W G ) is up to about 20% greater than the hole width (W H ). The width of a notch groove (W NG , not shown) is the distance from the side of the hole to the side of the notch groove. In this embodiment, the notch groove width (W NG ) is at most about 3 mm. If two notch grooves are positioned opposite one another, it is within the scope of the invention for the notch groove width (W NG ) of each notch groove to be the same width or to be different widths. 
         [0023]    Each groove  10  and each notch groove has a groove thickness (T G ). It is within the scope of the invention for a groove  10 , or a notch groove, to have any groove thickness (T G ). In at least one embodiment, the groove thickness (T G ) is less than the hole thickness (T H ). In some embodiments, the groove thickness (T G ) is about 1 mm to about 6 mm. In at least one embodiment, the groove thickness (T G ) is at most about 50% of the hole thickness (T H ). If the hole  8  has more than one groove  10 , the cumulative groove thickness is at most about 50% of the hole thickness (T H ). Thus, if the hole  8  has two grooves  10 , the cumulative groove thickness is equal to  TGI    plus  T G2 . 
         [0024]    Although the two grooves  10  in  FIG. 6  have substantially the same groove width (W G ) and groove thickness (T G ), it is within the scope of the invention for a hole  8  to have grooves with different widths, grooves with different thicknesses, notch grooves with different widths, notch grooves with different thicknesses, and any combination thereof. 
         [0025]    In at least one embodiment, the hole  8  has a plug  12  disposed therein, as shown for example in  FIG. 3 . In at least one embodiment, the plug  12  enables the ordnance to comply with insensitive munition requirements, such as are detailed in Mil-Std-2105C and in AOP-39. In some embodiments, the groove(s)  10 , or notch grooves, retains a plug  12  disposed in the hole  8 . 
         [0026]    As shown in the figures, the plug  12  has a first surface  14 , a second surface  16 , a width (W P , not shown), and a thickness (T P ). In some embodiments, the first surface  14  is the outer surface of the plug and the second surface  16  is the inner surface of the plug. In other embodiments, the first surface  14  is the inner surface of the plug and the second surface  16  is the outer surface of the plug. In some embodiments, the plug width (W P ) is variable because at least one portion of the plug  12  has a width that is either equal to the groove width (W G ) or to the hole width (W H ) plus the notch groove width (W NG ), and at least one portion of the plug  12  has a width equal to the hole width (W H ). In other embodiments, the plug width (W P ) is at most equal to the hole width (W H ), for example when the hole  8  does not have any grooves or notch grooves. 
         [0027]    In some embodiments, the plug thickness (T P ) is equal to the hole thickness (T H ), as shown, for example, in  FIG. 6 . In this embodiment, the first surface  14  of the plug  12  is flush with the first surface  4  of the casing  2  and the second surface  16  of the plug  12  is flush with the second surface  6  of the casing  2 . Thus, the plug  12  utilizes 100% of the venting area. As used in this application, the venting area is the area of the hole  8  plus the area of each groove  10  or notch groove, if present. 
         [0028]    In other embodiments, the plug thickness (T P ) is less than the hole thickness (T H ) so that at least one of the surfaces  14 , 16  of the plug  12  is below flush with at least one of the surfaces  4 , 6  of the casing  2 . An example of a plug  12  that has one surface that is below flush is shown in  FIG. 4 . In still other embodiments, the plug thickness (T P ) is greater than the hole thickness (T H ). The plug  12  shown, for example, in  FIG. 3  has a portion  17  that extends beyond the sides and beyond an opening of the hole  8 . The plug  12  in  FIG. 3  can be described as having a surface  16  that is “mushroomed”  17 . The mushroomed plug  12  can be described as having a first portion that is disposed against a portion of the second surface  6  of the casing  2 . A mushroomed surface  17  can also be described as a crimp cap. In some embodiments, the mushroomed surface/crimp cap  17  provides additional sealing of the hole  8 . In at least one embodiment, both surfaces  14 , 16  of the plug  12  are mushroomed  17   a , 17   b,  as shown in  FIG. 7 . In this embodiment the mushroomed surfaces  14 , 16  retain the plug  12  in a hole  8  that does not have any grooves or notch grooves. 
         [0029]    In at least one embodiment, a plug slug  18  is transformed into a plug  12  by a swaging or crimping process.  FIG. 8  shows a plug slug  18  disposed within the hole  8  prior to the swaging or crimping process. In at least one embodiment, the cooperative action of a ram  22  and an anvil  20  transforms the plug slug  18  into a plug  12 . In some embodiments, the plug slug  18  has a first configuration before the swaging or crimping process and a second configuration after the swaging or crimping process where the second configuration is different than the first configuration. 
         [0030]    As shown in  FIG. 8 , a ram  22  is positioned to press against the second surface  16  of the plug slug  18  and an anvil  20  is positioned against the first surface  14  of the plug slug  18 . To swage or crimp the plug slug  18  into the hole  8 , a plug slug is positioned within the hole  8 , an anvil  20  is positioned against the first surface  14  of the plug slug  18 , and a ram  22  presses against the second surface  16  of the plug slug  18 . It is also within the scope of the invention for the anvil  20  to be positioned against the second surface  16  of the plug slug  18  and for the ram  22  to press against the first surface  14  of the plug slug  18 . The action of the ram  22  against the plug slug  18  modifies the plug slug  18  into a plug  12  that has the same configuration as the hole  8 . 
         [0031]    The ram  22  has a width (W R ). In some embodiments, the ram width (W R ) is greater than the hole width (W H ), as shown for example in  FIG. 8 . In other embodiments, the ram width (W R ) is equal to the hole width (W H ). 
         [0032]    The anvil  20  has a width (W A ). It is within the scope of the invention for the anvil width (W A ) to be greater than, equal to, or less than, the hole width (W H ). For example, the anvil  20  shown in  FIG. 8 , has sides that are adjacent to the sides of the hole  8 , thus the anvil width (W A ) is at most equal to the hole width (W H ). In some embodiments, an anvil  20  with an anvil width (W A ) is at most equal to the hole width (W H ) is placed within hole  8  to produce a plug  12  that has a surface  14 , 16  that is not flush with a surface  4 , 6  of the casing  2 . In other embodiments, an anvil  20  with an anvil width (W A ) greater than the hole width (W H ) is used to produce a plug  12  that has a surface  14 , 16  that is flush with a surface  4 , 6  of the casing  2 . 
         [0033]    In at least one embodiment, the ram width (W R ), the anvil width (W A ), the size of the plug slug  18 , and combinations thereof, affect the attributes of the plug  12 . For example, a plug  12  that is mushroomed is made from a plug slug  18  having a greater size than a plug slug  18  used to make a plug  12  with surfaces  14 , 16  flush with the surfaces  4 , 6  of the casing  2 . 
         [0034]    The plug slug  18  has a thickness (T S ) and a width (W S , not shown). In at least one embodiment the plug slug thickness (T S ) is greater than the plug thickness (T P ). In some embodiments the plug slug  18  has a minimum plug slug thickness. A plug slug  18  with a minimum plug slug thickness forms a plug  12  that fills all portions/interfaces of the venting area (100% of the venting area) and that has surfaces  14 , 16  that are flush with the surfaces  4 , 6 , of the casing  2 , as shown for example in  FIG. 6 . Thus, the minimum plug slug thickness depends upon the venting area of the hole  8 . In other embodiments, the plug slug  18  has a plug slug thickness that is greater than the minimum plug slug thickness. In this embodiment, the plug slug  18  to form a plug  12  with at least one surface that is mushroomed  17 , as shown for example in  FIG. 3 . In still other embodiments, the plug slug  18  has a plug slug thickness that is less than the minimum plug slug thickness. In this embodiment, the plug slug  18  forms a plug  12  that has at least one surface  14 , 16  that is below flush, as shown in  FIG. 4 . 
         [0035]    In at least one embodiment, the width of the plug slug  18  is at most equal to the hole width (W H ). In some embodiments, the width of the plug slug  18  is less than the hole width (W H ), as shown, for example, in  FIG. 8 . In at least one embodiment, the width of the plug slug  18  is greater than the hole width (W H ). In this embodiment, the plug slug  18  is press-fitted into the hole  8  to form the plug  12 . 
         [0036]    Embodiments include one or more of the following advantages. In some embodiments, a plug  12  formed by the swaging process is not subject to creep, unlike plastic plugs. In other embodiments, a plug  12  formed by the swaging process does not loosen due to vibrations or temperature variations, unlike a plug with threads (threaded plugs). In at least one embodiment, the swaged in place plug  12  has a dimensionally controlled surface with excellent environmental sealing, in contrast to a melt-in-place plug which has an un-controllable surface with poor environmental sealing. In at least one embodiment, the plug  12  is used in a hole  8  that is too thin for a threaded plug to be used. Typically, a threaded plug with threads is used with a hole that is at least 8 mm thick. 
         [0037]    In some embodiments, the plug  12 /plug slug  18  is a metal alloy. In other embodiments, the plug  12 /plug slug  18  has a low melting temperature of about 115° C. to about 155° C. In some embodiments, the plug  12 /plug slug  18  is a low melt temperature eutectic metal alloy. In at least one embodiment, the plug  12 /plug slug  18  has a consistent melt out temperature with a low liquidus-solidus range of around 5° C. In some embodiments, the melt temperature of the plug  12 , allows the plug  12  to melt during cook-off environments. 
         [0038]    Materials that can be used to form the plug  12 /plug slug  18  include antimony, bismuth, cadmium, copper, gallium, indium, lead, silver, tin, zinc, and any compositions thereof. In some embodiments, the plug  12 /plug slug  18  is composed of bismuth, tin, and silver. In one embodiment, the plug  12 /plug slug  18  is composed of 57% bismuth, 42% tin, and 1% silver. One of ordinary skill in the art will recognize that the materials used to make the alloy affect the melt out temperature and therefore, the materials can be tailored so that a desired melt out temperature can be obtained. In some embodiments, the silver in the plug  12 /plug slug  18  makes the material forming the plug  12 /plug slug  18  more malleable and ductile so that the plug slug  18  can be swaged or crimped into the hole  8  without developing cracks.