Abstract:
A measuring device for measuring the concentricity of cartridges ( 30, 31 ), more particularly rifle cartridges, is essentially composed of a main body ( 1 ) provided with chambers ( 2 ) for cartridges of one or a plurality of calibers. The cartridges are radially retained in the chambers by so-called diameter compensators ( 9 ) but rotatable about their longitudinal axis. In the area of the point ( 39 ) of the projectile, an access for a measuring means ( 3 ) is provided, e.g., a dial gauge, the latter indicating the deviation of the projectile from perfect concentricity by the magnitude of its deflection variation when the cartridge ( 30, 31 ) is rotated. An aligning device ( 4 ) that is preferably also provided allows to exert a lateral pressure on the projectile in order to obtain an improved concentricity.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS  
       [0001]    This application is a continuation-in-part of U.S. patent application Ser. No. 10/158,043, filed May 28, 2002, to which the benefit of priority is claimed. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The invention refers to a device for measuring the concentricity of a projectile with respect to the case body of a cartridge, more particularly of a rifle cartridge.  
           [0003]    According to the latest findings confirmed by bench rest firing tests, an eccentricity of the projectile with respect to the case exceeding 0.025 mm will cause a deterioration of the firing precision that increases with the eccentricity. In this context, the eccentricity is defined as the angle between the longitudinal axis of the projectile and the case. Ideally, i.e. in the case of perfect concentricity, this angle is equal to zero.  
         BACKGROUND OF THE INVENTION  
         [0004]    The reduced precision resulting from the eccentricity not only affects the marksman in bench rest shooting. On the contrary, the various types of ammunition, all those applications are concerned where an absolute precision is an indispensable condition for the marksman, such as precision sports shooting, especially medium or long distance, as well as applications in public or private security or in hunting.  
           [0005]    Known apparatus for controlling and correcting the concentricity of a cartridge, i.e. essentially for aligning the projectile with respect to the case, only allow a rudimentary concentricity control and do not take account of the actual position of the cartridge in the cartridge chamber of a firearm.  
         SUMMARY OF THE INVENTION  
         [0006]    It is an object of the invention to provide a device allowing the measurement and preferably also the alignment of the projectile of a cartridge in order to achieve an improved firing accuracy.  
           [0007]    This is accomplished by a device wherein the device comprises a main body having at least one chamber for the cartridge, the chamber includes means for retaining the cartridge by pressing it against a wall of the chamber such that the cartridge remains rotatable, and an access is provided through which a measuring means is capable of contacting the projectile of the cartridge, such that the concentricity of the projectile with respect to the case body is measurable in rotating of the cartridge. Preferred embodiments are described in the remaining claims.  
           [0008]    Accordingly, the device essentially imitates the positioning of a rifle cartridge in the cartridge chamber in order to detect concentricity errors of the projectile of the cartridge with respect to its case. In a preferred embodiment, excessive concentricity errors can be corrected by a correcting device.  
           [0009]    According to a preferred embodiment, the device is small and inexpensive in manufacture, thus making it suitable for universal applications and easy transport by the marksman. Most preferably the device is in the form of a hand-held tool.  
           [0010]    Other preferred embodiments are defined in the claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    The invention will be further explained by way of example with reference to a preferred embodiment illustrated in the figures.  
         [0012]    [0012]FIG. 1 shows the main body of a device according to the invention in a longitudinal section;  
         [0013]    [0013]FIG. 2 shows a top view of the device of FIG. 1;  
         [0014]    [0014]FIG. 3 shows a side view of an improved aligning point;  
         [0015]    [0015]FIG. 4 shows a view of the push piece according to arrow  51  in FIG. 3;  
         [0016]    FIGS.  5 - 7  shows target diagrams; and  
         [0017]    [0017]FIG. 8 is a sectional view of a device according to an alternate embodiment of the present invention, wherein a portion of the main body includes an additional clearance for the cartridge. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]    The cylindrical main body  1  of the device is preferably made of a shock-resistant plastics material having good sliding properties. Two cartridge chamber imitations  2  of different calibers are provided in the main body in the form of central longitudinal bores.  
         [0019]    The cartridge chamber imitations  2  are so designed that cartridges  30  (smaller caliber) and  31  (larger caliber) inserted for concentricity control and adjustment project from the front sides of the main body  1  by a distance  33  that allows the manual rotation of the cartridges  30 ,  31  required for measuring and adjusting purposes.  
         [0020]    A location bore  6  for a commercially available dial gauge  3  is provided in the main body  1  and extends transversally to the cartridge chamber imitations  2 . Due to a close fit, the dial gauge  3  is self-adhesive in the location bore  6  but freely displaceable and freely rotatable in order to allow optimum readability. Aligning device  4  includes a threaded bore  35  intended for aligning screw  37  is disposed coaxially opposite the location bore  6  of the dial gauge  3 , the aligning screw  37  essentially consisting of handle portion  15  and a threaded spindle.  
         [0021]    The position of the dial gauge  3  and of the aligning screw  37  in the main body  1  is such that the inserted cartridge  31  can be measured (measuring point  7  of the dial gauge  3 ) and aligned (spindle point  8 ) in the area of projectile point  39 .  
         [0022]    In the context of the present invention, the difference between the minimum and the maximum reading of the dial gauge  3  during rotation of the cartridge  30 ,  31  will be used as a measure of the concentricity error. Since the dial gauge  3  measures the excursion of projectile  16  near its point, this value is approximately equal to the diameter of the circle described by the projectile point  39  during rotation of the cartridge  30 ,  31  around the longitudinal axis of the case.  
         [0023]    In order to compensate for existing differences in the diameters of the cartridge  30 ,  31 , the cartridge chamber imitations  2  in the main body  1  are designed with larger diameters than the respective cartridge, namely 1 to 2% larger than the theoretical case body diameter in area  13  of case body  73  and approx. 10% larger than theoretical case neck diameter B in area  14 . Throat  40 , located between areas  13  and  14 , serves as a rest for cartridge shoulder  71  and thus as a stop when inserting the cartridge  30 ,  31  in the cartridge chamber imitation  2 .  
         [0024]    By means of diameter compensators provided in the main body  1  on the side of the aligning screw  37  and in the center of the cartridge chamber imitations  2 , and composed of end cap  12 , spring  11 , and sliding piece  10 , the cartridges  30 ,  31  are maintained in the chambers  2  in such a manner that the cartridges  30 ,  31  are manually rotatable in the cartridge chamber imitations  2  under an even and adjustable tension. Stepped bores  42  for compensators  9  are preferably provided on the side of the aligning screw  37  between the respective rear end of the cartridge chamber imitation  2  and the throat  40 .  
         [0025]    An opening, in the present example in the form of a blind bore  5 , extending towards the center of the main body  1  and located at the same height as the bores for the dial gauge  3  and the aligning screw  37 , however offset therefrom, serves as a viewing window and allows an additional, but not indispensable, visual control of the measuring and aligning operations.  
         [0026]    Especially in the case of larger calibers, e.g. ammunition of caliber 10.3×60R, depending on the case structure, greater aligning forces are required. These may cause a slight deformation of the projectile  16  at the contact surface between the aligning point and the projectile  16 . The resulting rotational eccentricity affects the firing precision. In particular, this may be the case with projectiles where a relatively soft core is enclosed in a think jacket.  
         [0027]    This problem is solved by the embodiment illustrated in FIGS. 3 and 4.  
         [0028]    Aligning point  8  contains a seat  53  for a ball  55  to which a thrust plate  57  is affixed. FIG. 4 shows a projection of the ball  55  and the plate  57  according to arrow  51  (FIG. 3). It is visible that the thrust plate  57  comprises an approximately cylindrical depression  59 . In particular, the depression  59  may also be precisely adapted to the surface of the projectile  16  in the contact zone.  
         [0029]    Otherwise, the measuring and aligning device  1  corresponds to the previously described embodiment.  
         [0030]    The thrust plate  57  thus provides an enlarged engaging surface for the transmission of the aligning force to the projectile  16 . Practical tests have shown that a deformation of the projectile  16  is excluded when this thrust point is used.  
         [0031]    A further advantage of this embodiment of the aligning point consists in that the rotational movement now occurs between the ball  55  and the seat  53  in the aligning point, whereas the point rolls on the projectile surface in the simple embodiment.  
         [0032]    A measuring and aligning procedure will be described in the following: The aligning device allows exertion of a lateral pressure on the projectile  16  in order to improve concentricity. The cartridge  31  is inserted in the cartridge chamber imitation  2  of the corresponding caliber. The dial gauge  3  is inserted in the bore  6  until the measuring point  7  contacts the point  39  of the projectile  16 . The projecting end  41  of the cartridge  31  is seized between thumb and index finger and rotated at least 360°, meanwhile determining the total deflection of the dial gauge  3 , i.e., the difference between the minimum and the maximum reading of the measuring gauge. The cartridge  31  is further rotated until the dial gauge  3  reaches the minimum reading that corresponds to the maximum deflection of the projectile point towards the aligning point  8 .  
         [0033]    Rotation of the aligning point  8  by means of the knob  15  will result in a pressure acting on the point  39  of the projectile  16 , thereby deflecting it to such an extent that the point  39  of the projectile  16  remains laterally deflected from its original position by half of the total deflection of the dial gauge  3  when the aligning point  8  is lifted off. The aligning operation is then completed.  
         [0034]    It will further be noted that the device of the invention also allows the user to detect and single out cartridges whose case is deformed or damaged or whose total length excessively deviates from the ideal value due to a different setting depth.  
         [0035]    The target diagrams of FIGS.  5  to  7  illustrate the effect of the alignment of the cartridges  30 ,  31  by means of the device  1  of the invention. The illustrations correspond to target diagrams obtained by firing a rifle fixed in a holding device on a distance of 300 m. The inner target circle had a diameter of 50 mm. FIG. 5 shows the diagram obtained with the cartridges  30 ,  31  having a concentricity error of 0.1 to 0.18 mm, FIG. 6 shows the target diagram obtained with a concentricity error of less than 0.1 mm, and FIG. 7 shows the target diagram in the case of a concentricity error of no more than 0.03 mm. The comparison of FIGS. 5 and 6 already shows a noticeable concentration of the hits in the target center, while FIG. 7 shows a distinct improvement of the firing accuracy. It will be understood that a concentricity error of no more than 0.03 mm, as in the case of the cartridges  30 ,  31  used for target diagram FIG. 7, can only be achieved by aligning the cartridges  30 ,  31  in the device  1  of the invention, while the cartridges  30 ,  31  having concentricity error of up to 0.1 mm may still be obtained by measuring and singling them out, for which purpose the cartridge measuring device  1  of the invention is advantageous as well.  
         [0036]    In an alternative embodiment of the invention and as shown in FIG. 8, the throat  40  of the device  1  comprises a shoulder insert  61  and a groove  60  positioned within the device. The groove  60  is manufactured with an enlarged diameter. The enlarged diameter of the groove  60  permits the shoulder insert  61  to freely move radially within the device  1 . The contact point of the shoulder  71  of the case body  73  is centered upon the shoulder insert  61  through the existing radial play of the shoulder insert  61 . Digressions in the total length of the cartridge  31  due to divergent projectile insertion depths can therefore be immediately identified through the readings from the dial gauge  3  and can be promptly sorted out from other cartridges.  
         [0037]    As shown in FIG. 8 and in order to improve the preciseness of the measurement of a cartridge with an uneven cartridge case, the profile of the cartridge chamber imitation  2  within the device  1  is arranged such that the cartridge  31  inserted within the device  1 , when pressed inward from the side by a compensator  9 , only rests against the walls of the cartridge chamber imitation  2  within zones L 1  and L 3 , with additional clearance in the L 2  zone.  
         [0038]    Modifications with respect to the preceding description are accessible to those skilled in the art without departing from the scope of protection of the invention as defined by the claims. For example, it is possible to position the aligning device and/or the measuring device in a location such that either device may contact and/or exert a lateral pressure on any portion of the projectile. Other conceivable options include:  
         [0039]    manufacturing the bore without including a clearance zone L 2  or by using a different arrangement in zones L 1  and L 3 ;  
         [0040]    manufacturing the bore and the throat without a groove and without a shoulder insert;  
         [0041]    manufacturing the groove with a diameter to correspond with the precise outside diameter of the shoulder ring, resulting in a relative lack of axial play of the shoulder ring within the groove;  
         [0042]    manufacturing the bore with the contact points of the cartridge case located in other sections of the bore, such as the neck or the shoulder regions of the cartridge case;  
         [0043]    manufacturing the main body of a material other than plastics material;  
         [0044]    manufacturing a different shape of the main body, e.g. an essentially parallelepipedic shape;  
         [0045]    incorporating more than one viewing window into the device;  
         [0046]    incorporating viewing windows in the form of a through-going bore, thereby allowing an observation from both sides of the tool;  
         [0047]    not incorporating a viewing window at all;  
         [0048]    providing the device with a different number of cartridge chamber imitations, particularly also only one;  
         [0049]    providing the diameter compensators in a different place than in the center of the section receiving the case body or in a different position than opposite the dial gauge;  
         [0050]    incorporating a cross-section of the cartridge chamber imitations other than circular, e.g. a V-shaped cross-section with the point of the V opposite the compensator;  
         [0051]    incorporating more than one diameter compensator per cartridge chamber imitation in the device;  
         [0052]    incorporating a different deviation of the cartridge chamber diameters from the nominal diameter of the cartridges;  
         [0053]    incorporating a cartridge chamber imitation in the form of an insert in the main body, the use of different inserts allowing the adaptation to different calibers;  
         [0054]    using a measuring device other than a mechanical dial gauge, e.g., a gauge having a digital display and/or a signal or data output, e.g., for connection to a computer controlled measuring device;  
         [0055]    using a motor-driven form of the aligning device  4 , particularly in conjunction with a measuring device having a signal or data output, thereby allowing a nearly entirely automatic operation, e.g., according to the following sequence:  
         [0056]    Insertion of cartridge;  
         [0057]    Start of measuring operation;  
         [0058]    Rotation of cartridge by at least a full turn in order to determine concentricity error;  
         [0059]    Stop of measuring operation, rotational positioning;  
         [0060]    Rotation of cartridge, possibly according to instructions from the measuring and aligning device, until position of maximum deviation of projectile towards aligning device is attained;  
         [0061]    Stop of rotational positioning, start of aligning operation;  
         [0062]    Advance of the aligning device  4  and deflection of projectile until measuring device detects a predetermined deflection, under control of measuring and aligning device;  
         [0063]    Verification of concentricity error essentially by repeating the measuring procedure; and  
         [0064]    Motorized device for effecting the rotation of the cartridge (preferable if the measuring and aligning device is designed for automatic operation).