Abstract:
A magazine add-on comprising a platelet arranged to replace the bottom platelet of the magazine and allow measuring the distance, e.g., via an aperture in the platelet, to the magazine&#39;s spring-loaded follower either mechanically by an elastic strap, optically by a rangefinder or by measuring the pressure applied by the spring on the platelet. The add-on further displays a number of bullets left in the magazine in a window, either mechanically by numbers on the back of the strap, or electronically on a display attached to the window and connected to the optical or pressure sensor. The add-on is reusable and may be separated and re-attached to various magazines.

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to the field of weaponry, and more particularly, to counting bullets in a magazine. 
     2. Discussion of Related Art 
     Weapon magazines usually lack indications of the remaining number of bullet, which may be very important and even crucial to the soldier. 
     WIPO publication No. 2008132739, which is incorporated herein by reference in its entirety, discloses a magazine status indicator. 
     BRIEF SUMMARY 
     Embodiments of the present invention provide an apparatus comprising: a housing attachable to a bottom of a magazine having a spring-loaded follower, the housing having a window; a platelet arranged to replace a bottom platelet of the magazine and comprising a connector connectable to the spring, and an aperture; means for measuring, through the aperture, a distance between the follower and a point in the housing, the means for measuring integrated within the housing; and means for displaying a number of bullets left in the magazine, through the window, according to the measured distance, wherein the apparatus is arranged to be added on the magazine and display the number of bullets left in the magazine. 
     These, additional, and/or other aspects and/or advantages of the present invention are: set forth in the detailed description which follows; possibly inferable from the detailed description; and/or learnable by practice of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be more readily understood from the detailed description of embodiments thereof made in conjunction with the accompanying drawings of which: 
         FIG. 1  is a high level schematic block diagram of an add-on apparatus and a magazine having a spring-loaded follower, according to some embodiments of the invention. 
         FIG. 2  is a schematic illustration of the apparatus, according to some embodiments of the invention; and 
         FIGS. 3A ,  3 B,  4 A and  4 B are schematic illustrations of the magazine with the apparatus, according to some embodiments of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is applicable to other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting. 
       FIG. 1  is a high level schematic block diagram of an add-on apparatus  100  and a magazine  90  having a spring-loaded follower  96 , according to some embodiments of the invention.  FIG. 2  is a schematic illustration of apparatus  100 , according to some embodiments of the invention. Apparatus  100  is arranged to be added on magazine  90  having spring-loaded follower  96  (see  FIGS. 3A through 4B ) and display the number of bullets left in magazine  90 . Apparatus  100  comprises a housing  110  attachable to a bottom of a magazine (by clips or other connector types), and a platelet  120  arranged to replace a bottom platelet of magazine  90  and comprises a connector (not shown) connectable to spring  93 . Platelet  120  has an aperture  125  through which a distance  99  between follower  96  and a point in housing  110  is measured by means for measuring  130  integrated within housing  110 . Apparatus  100  further comprises means  140  for displaying a number of bullets left in magazine  90 , through a window  112  in housing  110 , according to measured distance  99 . 
     Measuring distance  99  may be carried out mechanically by an extendable strap  150 , or by sensors ( 160 ,  170 ) as illustrated in the following figures. 
       FIGS. 3A and 3B  are schematic illustrations of magazine  90  with apparatus  100 , according to some embodiments of the invention. 
     Means for measuring  130  may comprise a coiled elastic strap  150  having an inner end  151  fixated within housing  110  and an outer end  159  stretching through aperture  125  and engaged in an impermanent connection  155  with follower  96 . Impermanent connection  155  is arranged to allow disconnecting apparatus  100  from magazine  90  and reusing apparatus  100  with a different magazine. 
     Means for displaying  140  the number of bullets left in magazine  90  may comprise numbers  141  on a side of coiled elastic strap  150  that faces window  112  from inside housing  110 , the numbers increasing towards inner end  151 . The numbers may be printed, engraved or attached to strap  150 . The displayed area of strap  150 , i.e., the area facing window  112 , may be variously situated in respect to the coiled part of strap  150 —it may be in the back of the coiled part or along straight parts of strap  150  between inner end  151  and outer end  159 . Numbers  141  may have contrasting colors in respect to the back of the coiled part, or include other visibility enhancers such as phosphorous markings. 
     Outer end  159  of strap  150  is arranged to move together with follower  96  such as to uncoil coiled strap  150  and present higher numbers in front of window  112  upon an upward motion of follower  96 , and such as to allow coiled strap  150  to elastically re-coil and present lower numbers in front of window  112  upon a downward motion of follower  96 . (The directions are in respect to the Top and Bottom markings on  FIG. 1 .) 
     The relative positions of window  112  and strap  150  may vary. Strap  150  may be arranged to extend along various paths. For example, window  112  may be positioned on a first narrow edge  101  of apparatus  100  and inner end  151  is fixated in a corresponding first side  102  of apparatus  100 , while aperture  125  may be positioned at an opposite narrow edge  108  of apparatus  100  and outer end  159  extend over opposite side  107  through aperture  125  to connect to follower  96  at the opposite narrow side in respect to window  112 . 
     Apparatus  100  may further comprises a support  153  positioned within housing  110  at a lower portion of opposite side  107 , and arranged to support extended elastic strap  150 . 
     Alternatively, outer end  159  may extend through a middle  156  of apparatus  100 , aperture  125  may be positioned in the middle of platelet  120 , and outer end  159  may pass through an inner space  157  of spring  93  and is connected to the middle of follower  96 . 
     Impermanent connection  155  may comprise a connection by a clip (not shown) connected to outer end  159  of strap  150  and operatively attached to follower  96 . 
     Impermanent connection  155  may comprise a magnetic connection between a magnet  152  connected to outer end  159  of strap  150  and follower  96 . 
       FIGS. 4A and 4B  are schematic illustrations of magazine  90  with apparatus  100 , according to some embodiments of the invention. 
     Means for measuring  130  may comprise a rangefinder  160  positioned in housing  110  and arranged to optically measure distance  99  to follower  96  through aperture  125 . Means for displaying  140  the number of bullets left in magazine  90  may comprise a display  145 , and apparatus  100  may further comprise a controller  147 A (e.g., a printed circuit board—PCB) arranged to receive the distance measurement, calculate the number of bullets left in magazine  90  therefrom, and display the number on display  145 . 
     Means for measuring  130  may comprise a pressure sensor  170  such as a piezoelectric sensor, connecting platelet  120  to spring  93  and arranged to measure a pressure applied by spring  93  thereupon. Means for displaying  140  the number of bullets left in magazine  90  may be display  145 , and apparatus  100  may further comprise controller  147 B arranged to receive the pressure measurement, calculate the number of bullets left in magazine  90  therefrom, and display the number on display  145 . 
     Display  145  may comprise a white on black display for good night visibility, e.g., an OLED (Organic Light Emitting Diode) display. Other types of contrast may be implemented in display  145  to enhance visibility, e.g. phosphorous markings 
     In the above description, an embodiment is an example or implementation of the invention. The various appearances of “one embodiment”, “an embodiment” or “some embodiments” do not necessarily all refer to the same embodiments. 
     Although various features of the invention may be described in the context of a single embodiment, the features may also be provided separately or in any suitable combination. Conversely, although the invention may be described herein in the context of separate embodiments for clarity, the invention may also be implemented in a single embodiment. 
     Furthermore, it is to be understood that the invention can be carried out or practiced in various ways and that the invention can be implemented in embodiments other than the ones outlined in the description above. 
     The invention is not limited to those diagrams or to the corresponding descriptions. For example, flow need not move through each illustrated box or state, or in exactly the same order as illustrated and described. 
     Meanings of technical and scientific terms used herein are to be commonly understood as by one of ordinary skill in the art to which the invention belongs, unless otherwise defined. 
     While the invention has been described with respect to a limited number of embodiments, these should not be construed as limitations on the scope of the invention, but rather as exemplifications of some of the preferred embodiments. Other possible variations, modifications, and applications are also within the scope of the invention. Accordingly, the scope of the invention should not be limited by what has thus far been described, but by the appended claims and their legal equivalents.