Patent Publication Number: US-10322590-B2

Title: Method and device for marking ammunition for identification or tracking

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a National Stage Application of International Application No. PCT/EP2014/070215 filed Sep. 23, 2014, which published as WO 2015/040236 A1 on Mar. 26, 2015, the disclosures of which are expressly incorporated by reference herein in their entireties. Further, the present application claims the benefit of U.S. provisional application No. 61/881,168, filed Sep. 23, 2013, the disclosure of which is expressly incorporated by reference herein in its entirety. 
    
    
     BACKGROUND OF THE DISCLOSURE 
     1. Field of the Disclosure 
     The present disclosure relates to the field of marking of ammunition. In particular, the disclosure relates to a method of providing a mark to a case of a cartridge of ammunition, wherein the mark comprises at least one sub-mark and is suitable for identification or for tracking of the cartridge. Further, the disclosure relates to a device for providing such a mark to a cartridge of ammunition. 
     2. Background Description 
     Ammunition marking is an important tool for tracking of ammunition as well as for controlling the use of it. Further, it can be used for quality assurance and for ensuring proper use of ammunition by clearly identifying the sort of ammunition, in particular its type and caliber. In connection with the use of ammunition by military and law enforcement forces, marking of ammunition is important for stock pile management, transportation and record keeping. Particularly in the civil sector, marking ammunition potentially helps investigating crimes in which firearms are involved. 
     It is common that marks in the form of a stamp are applied to the bottom of a cartridge, also called round, of ammunition. However, due to the limited space available on the bottom of a cartridge, the amount of information which can be applied to the cartridge via such a marking is also very limited. There are techniques of applying a mark also to the lateral outer surface of a cartridge case. Marking the lateral outer surface of a cartridge case is, today, achieved by use of printing techniques. The usual technique of stamping, as it is applied to the bottom of the case of the cartridge, is much less suitable for application to the case in its lateral or radial direction. Thus, press stamping is not used for marking the lateral surface of the case. 
     It is known from U.S. Pat. No. 7,823,495 B2 to use laser engraving techniques for engraving the surface of a cartridge, in particular an extractor groove which is typically placed in the area near the bottom of the case. A particular drawback of this method is that the equipment needed for laser engraving is very complex and, thus, expensive, which is a decisive disadvantage for any manufacturer who wants to use the laser engraving method for marking cartridges of ammunition. 
     Other known techniques, namely press stamping and silk screen or similar printing techniques, have other disadvantages. As to the press stamping, in addition to the fact that this method cannot be applied to the lateral surface of a case of a cartridge, the costs for producing press stamping dies are also significant, similar to the laser engraving equipment. As to the printing techniques, the marks provided by these techniques tend to lose their readability after the cartridge has been fired and can easily be counterfeited. 
     Accordingly, there is a need for a less expensive method for marking ammunition that is capable of applying marks also to the lateral surface of an ammunition cartridge case so as to increase the maximum amount of information provided by the mark. 
     SUMMARY OF THE DISCLOSURE 
     It is an aim of the present disclosure to provide a method and a device which allow for efficiently marking ammunition by a durable and reliable mark that cannot easily be removed. 
     This problem is solved by the method and the device according to respective independent claims. Further preferred features of the method or device are recited in the dependent claims and detailed in the following description. 
     Throughout this text, the cartridge of ammunition is also referred to as a round of ammunition. The inventive method of providing a mark to a case of a cartridge of ammunition, or to a round of ammunition, the mark comprising at least one sub-mark and being suitable for identification or for tracking of the cartridge, makes use of at least one indenter, which selectively radially indents a circumferential surface of a bottom of the case, thereby forming the at least one sub-mark. The indenter is preferably present in the form of a finger, but the form of the embodiment for the indenter can be chosen depending on the space available next to the cartridge or round of ammunition. 
     A cartridge or round of ammunition usually comprises a case, a primer, a propellant and, optionally, one or more projectiles. The propellant usually is a chemical composition to be ignited by the primer, which then explodes and generates high pressure that can be used to propel a projectile. 
     Common names for propellants are “powder”, “gunpowder”, “smoke-less powder” and “black powder”. In order to ignite the propellant, the cartridge usually comprises the primer, which, upon impact of a firing pin, ignites the propellant. The primer can be provided with a separate casing enclosing a priming mixture. Further, at least the propellant, usually also the primer and, optionally, also a projectile are at least partially enclosed in a case, at least part of which forms at least part of an outer surface of the cartridge or round. If a projectile is provided, the projectile usually is at least partially enclosed in the case on the side of the propellant opposite to the primer. Projectiles are, however, not essential or required. 
     The case usually is cylindrical, conical, or bottle-shaped and has an axis of symmetry defining longitudinal, radial, and circumferential directions. In the longitudinal direction, which is parallel to the axis of symmetry, the propellant usually is located between a primer and a projectile or several projectiles. Radially, i.e. perpendicular to the axis of symmetry, the case usually forms the outer surface of the cartridge. 
     Most cartridges further have an extraction groove in the case. This is usually applied to the case in the vicinity of a bottom of the case. In the present application, the sub-marks can be applied both to the bottom of the case and to the extraction groove. In other words, the extraction groove is, in this context, to be considered to be part of the bottom of the case. 
     The mark to be applied to the case is meant to identify a cartridge. The mark can be used, for example, to individually identify a specific piece of ammunition or to more generally identify its type, such as its caliber. For example, the mark, which is possibly encoded, may be a lot number or a serial number of the cartridge. Hence, the mark in the present context is not merely an accidental or random mark on the surface of a case but an intentionally applied mark that can have the form of indentations that are sized and/or separated from each other in a recognizable manner so as to form a barcode or similar code. 
     At least one indenter is used to selectively radially indent a circumferential surface of a bottom of the case to thereby form the at least one sub-mark. Indenting the surface should be understood as the indenter being pressed into the surface of the case in the vicinity of its bottom, thereby deforming the case, in order to form a groove into the case. Pressing the indenter into the surface leads to locally stressing the surface of the case beyond its elastic limit so that an inelastic deformation is achieved. 
     The bottom of the case in the sense of the present disclosure is defined to comprise the portion of the case that extends from an extraction groove towards the end of the case opposite to any projectile. Preferably, the bottom of the case additionally includes the extraction groove. 
     In contrast to the prior art according to U.S. Pat. No. 7,823,495 B2, it is not necessary for the present disclosure to use expensive laser equipment for engraving a surface of the case of the cartridge. 
     Accordingly, the inventive method allows the application of marks to the circumferential surface of the bottom of the case of the cartridge of ammunition in an inexpensive way. The marks thus applied are not more easily removable or less durable than marks resulting from press stamping, laser engraving or printing. 
     Preferably, the mark comprises a plurality of sub-marks. By using a plurality of sub-marks it is possible to encode relatively complex information on the surface of the case. An example for a mark having a plurality of sub-marks is a barcode consisting of several indentations of different widths along the circumferential direction of the case. 
     In a preferred embodiment, the sub-mark is at least one of a material displacement, a deformation, a scratch, and a hole. The sub-mark preferably has a radial minimum depth for effectively protecting the sub-mark against wear or intentional removal of the sub-mark by an unauthorized person. A preferred minimum depth of the sub-mark is about 10% of the thickness of the case. Here, the thickness of the case should be understood as the thickness of the material, typically a metal, which radially and circumferentially encloses, e. g., the propellant. 
     Preferably, the mark provides information on the basis of at least one of an absolute position of the at least one sub-mark on the case, a relative position of the at least one sub-mark with respect to at least one further sub-mark, the existence or non-existence of the at least one sub-mark at a predetermined position, a depth of the at least one sub-mark on the case, a width of the at least one sub-mark, and a modulation in depth or width of the at least one sub-mark. 
     All of the above-mentioned features of the sub-mark can be used for encoding or decoding of information applied to the case via the sub-marks. The absolute position of the sub-mark should be understood as the position of the sub-mark in relation to the case, as opposed to a relative position of the sub-mark in relation to other sub-marks on the case. The depth and width of the sub-mark can be detected by a respective detector, as can the modulation in depth or width of the at least one sub-mark. 
     In a preferred embodiment, the at least one indenter comprises a material that is harder than a material of the case. It is preferred that the indenter is harder than the material of the case to ensure that the sub-marks are reliably indented in the surface of the case. A possible material for the indenter would, therefore, be diamond, diamond-like carbon, or similar materials. Alternatively, it is possible that the indenter is made of a metal or an alloy that preferably is harder than the material of the case. 
     In a preferred embodiment, the at least one indenter is moved by an actuator from an idle position to an active position for radially indenting into the circumferential surface of the bottom of the case. Using such an actuator allows for very precisely marking the case. 
     Further preferably, the active position of the indenter is variable and the depth of the at least one sub-mark on the case may be modulated by varying the active position of the indenter. Varying the depth of the sub-mark increases the degrees of freedom for encrypting information via the mark on the case. 
     The variable active position of the indenter can be understood to indicate a plurality of active positions or a continuously variable active position that can be controlled by the actuator. In any case, the amount and density of information that can be applied to the cartridge can be significantly increased. 
     In a preferred embodiment, a plurality of indenters selectively radially indent a circumferential surface of the bottom of the case. If the plurality of indenters is used, the method for marking the case can be made substantially more efficiently because several marks can simultaneously be applied to the case. 
     Further preferably, a computer system controls the at least one indenter, preferably the plurality indenters, and a position of the cartridge in order to generate a predetermined mark on the cartridge in accordance with the above mentioned methods. 
     A device according to the present disclosure for providing a mark to a case of a cartridge of ammunition, the mark comprising at least one sub-mark and being suitable for identification or for tracking of the cartridge, comprises at least one indenter. The indenter is configured for selectively radially indenting a circumferential surface of a bottom of the case for thereby forming the at least one sub-mark, the device preferably being configured for carrying out at least one of the above-outlined methods. 
     It is preferred that the device comprises an actuator which is configured for moving the at least one indenter between an idle position, in which the indenter does not interact with the case, and an active position, in which the indenter interacts with the case such that the at least one sub-mark is formed. The active position of the indenter is a position in which the indenter radially indents into the circumferential surface of the bottom of the case in order to form the sub-mark. 
     In a preferred embodiment, the active position of the indenter is variable. This can be understood as a plurality of active positions, which indicates a plurality of positions to which the indenter can be moved by the actuator and, in these positions, interacts with the case such that a sub-mark can be formed. Alternatively, the active position of the indenter being variable can also be understood as a continuous variation of the active position to indent a plurality of different depths of the sub-mark into the case. 
     In a preferred embodiment, the device comprises a plurality of indenters that are configured for selectively radially indenting a circumferential surface of the bottom of the case for thereby forming a plurality of sub-marks. The use of a plurality of indenters makes the device more efficient and allows marking of a case in less time because the plurality of sub-marks can be applied to the case simultaneously. 
     In a further preferred embodiment, the device comprises a computer system that is configured for controlling the at least one indenter, preferably a plurality of indenters, and for positioning the cartridge in order to allow for generating a predetermined mark on the cartridge. 
     The present method and device and their preferred embodiments as outlined above allow for solving the above-identified problem. In particular, marking a case of a cartridge of ammunition is made possible in a very efficient manner, it being possible to apply the mark to the lateral surface of the case with a high density of information. The mark cannot easily be removed from the cartridge and is resistant to wear. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a bottom view of a case of a cartridge of ammunition that illustrates a preferred method in accordance with aspects of the disclosure. 
         FIG. 2  is a side view of the case of the cartridge of  FIG. 1 , illustrating a portion of the case in accordance with aspects of the disclosure. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS OF THE DISCLOSURE 
       FIG. 1  illustrates a preferred method for providing a mark to a case  13  of a cartridge of ammunition. The mark comprises a plurality of sub-marks  12  which are applied to the case  13  by, in the illustrated embodiment, a plurality of indenters, e.g., compression fingers  10 , which are structured and arranged to selectively radially indent a circumferential surface of a bottom  20  of the case  13 . 
     The bottom view of the case  13  of  FIG. 1  shows the bottom surface of the case  13  by which the firing pin of a gun activates the primer in the case  13  to ignite the propellant and, optionally, fire the projectile. The bottom of the case  13  is located at the end of the cartridge opposite to any projectile. This bottom surface of the case  13  can, in addition to the marks of present disclosure, be marked by a head stamp in the usual manner, as known from the prior art. Such a head stamp is, however, not illustrated in  FIG. 1 . 
       FIG. 1  illustrates that a circumference of the bottom  20  forms a circle, if no indentation is applied. At certain positions along the circumference, compression fingers  10  are illustrated as indenting the circumferential surface of the bottom  20 , which surface cannot be seen in  FIG. 1 , to thereby form sub-marks  12 . In  FIG. 1 , eight equally circumferentially distanced compression fingers  10  are illustrated. However, the method can be carried out by use of a single compression finger  10  or almost any higher number of compression fingers  10  with regular or irregular, fixed or variable circumferential distances to each other. 
     As can be seen in  FIG. 1 , at selected positions along the circumference, sub-marks are applied or not-applied by the compression fingers  10 . In the example of  FIG. 1 , eight predetermined positions exist for forming a sub-mark or not, namely, the angular positions of the compression fingers  10 . Whether or not a sub-mark exists at these respective predetermined positions is used to encode information to the case  13  via the mark for identification and/or tracking of the cartridge. At the angular position  14  on the circumferential surface of the bottom  20 , a compression finger  10  is present and could indent the surface for forming a sub-mark. However, in the situation illustrated in  FIG. 1 , no sub-mark  12  is formed at this position  14  so that the non-existence of a sub-mark at this position can be detected by a respective detector. 
     By using predetermined positions for the sub-marks, it is possible to encode information, e.g. on the basis of the binary system, also on the basis of non-existing indentations at one or more of these positions. 
     However, in addition to simply detecting whether or not a sub-mark is present at a certain predetermined position on the surface of the case  13 , it is also possible to vary the shape of the sub-mark  12 , in particular the depth of the indentation, to thereby add further degrees of freedom in order to increase the information density of the mark. 
       FIG. 1  illustrates, of the compression fingers  10 , a plurality of (e.g., four) active compression fingers  11 . 1 , as well as a plurality of (e.g., three) idle compression fingers  11 . 2 . While the active compression fingers  11 . 1  are illustrated to indent and form a respective sub-mark  12 , the idle compression fingers  11 . 2  are not in contact with the case  13 . 
     A preferred device for carrying out the method illustrated in  FIG. 1  comprises a plurality of compression fingers  10 , which, by use of actuators  30  (only one of which is schematically depicted in  FIG. 1 ), can be moved between an idle position and at least one active position. In order to increase the number of degrees of freedom and, thereby, the information density of the mark, it is further preferred that the actuators are configured for moving the compression fingers  10  between an idle position and a variable active position. The variable active position can be a plurality of stepwise differing active positions or a continuously varying active position. 
     Preferably, the actuators of the compression fingers  10 , in particular if there is more than one compression finger  10  involved, are controlled by a computer system that is configured to coordinate the compression fingers and the position and orientation of the cartridge and its case  13 . Thereby, a preferred method can be realized in a very efficient way, wherein a plurality of sub-marks  12  can be applied to the case  13  simultaneously. 
       FIG. 2  is a side view of the case  13  and illustrates the bottom  20  of the case  13  as a portion of the case  13  and an extractor groove  21 . 
     This portion of the case  13  usually contains parts of the primer. However, in the context of the present disclosure, this portion of the cartridge, i.e. the bottom  20  and, preferably, also the extractor groove  21 , is considered to be the bottom  20  of the case  13 .