Patent Publication Number: US-2019170463-A1

Title: Round counter for firearm

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15,602,449, filed May 23, 2017, which application claims priority to U.S. Provisional Patent Application No. 62/340,282, filed May 23, 2016, the entire content of each being hereby incorporated by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the magazine of a firearm. In particular, the present invention relates to a counter for determining the number of rounds remaining in the firearm magazine. 
     BACKGROUND OF THE INVENTION 
     Existing reciprocating bolt firearms, including carbines and rifles, such as the AR15/M16 among others, employ a magazine to store unfired rounds of ammunition in a queue to be fired by the rifle. For many applications, including competitive shooting, law enforcement combat and others, it is critical for the firearm shooter to know how many rounds remain in the magazine. However, many magazines as currently used give no indication of the remaining rounds. The shooter is forced to either keep a mental count of how many rounds have been fired or be prepared for the firearm to cease firing unpredictably, preventing the operator from reloading the firearm at a strategically advantageous time. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings. The figures identified here represent various features in accordance with embodiments of the present invention. 
         FIG. 1  is a cutaway schematic view of a firearm magazine. 
         FIG. 2  is a schematic view of a display assembly. 
         FIG. 3  is a schematic view of a firearm magazine and sensor. 
         FIG. 4  is a schematic view of an electronics compartment. 
         FIG. 5  is a view of the top of a firearm magazine. 
         FIG. 6  is a perspective view of a firearm magazine. 
         FIG. 7  is a view of the side of a firearm magazine. 
         FIG. 8  is a view of the rear of a firearm magazine. 
         FIG. 9  is an exploded, perspective view of a firearm magazine. 
         FIG. 10  is a view of the rear of a firearm magazine. 
         FIG. 11  is a cut-away view of a firearm magazine along the line B-B of  FIG. 10 . 
         FIG. 12  is a detail view of section C of  FIG. 11 . 
         FIG. 13  is a perspective view of a display assembly. 
         FIG. 14  is a cut-away, perspective view of a firearm magazine. 
         FIG. 15  is a cut-away view of the side of a firearm magazine. 
         FIG. 16  is a perspective view of a display assembly. 
         FIG. 17  is a cut-away, perspective view of a firearm magazine. 
         FIG. 18  is a cut-away view of the side of a firearm magazine. 
         FIG. 19  is an exploded, perspective view of membrane potentiometer. 
         FIG. 20  is a cross-sectional, schematic view of membrane potentiometer. 
     
    
    
     DETAILED DESCRIPTION 
     Throughout this application, the directional references, such as forward, rearward, left, right, bottom and top, will be used. These and other such references are relative to the firing direction of the firearm, which fires in a forward direction. Such references are used for ease in describing the present invention and should not be construed as limiting the scope of the invention. As used in the description herein and throughout the claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise: the meaning of “a,” “an,” and “the” includes plural reference, the meaning of “in” includes “in” and “on.” Also, reference designators shown herein in parenthesis indicate components shown in a figure other than the one being discussed. 
     This application may make reference to an AR-15 patterned rifle and include illustrations of magazine embodiments appropriate for use with such a rifle. However, it will be understood by one of ordinary skill in the art that the principles of the present invention are applicable to a broad range of firearms using round storing magazines, including rifles, handguns, shotguns, etc. The present invention should not be understood to be limited to use with an AR-15 patterned rifle or any other particular firearm. 
     The embodiments of the invention are designed to incorporate into a rifle&#39;s magazine, intended for use in the AR-15 patterned rifle. The basic function will read the follower&#39;s location inside the magazine body in order to calculate the number of cartridges in the magazine and display that information to the shooter, for example by means of a small LCD screen or some other appropriate display device. 
     This device uses a thinpot linear potentiometer affixed within the magazine body. The magazine follower contains a spring plunger to impart pressure to the linear potentiometer. The potentiometer is arranged vertically, against the rear interior wall of the magazine body. The spring plunger is oriented horizontally, at the rear of the follower, and protrudes beyond the follower&#39;s rear edge. Pressure applied to the potentiometer by the plunger creates a contact patch within the potentiometer&#39;s structure. This depression effectively changes measured resistance within the potentiometer. Thus, the location of that contact patch may be interpreted by the digital processor. The potentiometer directly produces analog data that is converted into a digital format by an analog/digital converter. 
     The magazine body contains a magnetic switch to control power supply to the onboard sensors and processors. The magnetic switch is located on the rear external surface of the mag body, that when the magazine is locked into the rifle, is adjacent to the trigger guard in the rifle receiver. The trigger guard contains a permanent magnet that closes the switch and “turns on” or provides an initiation signal to the electronic systems when the magazine is in place. 
     The analog converter, digital processor, and power source are housed within the floorplate structure of the magazine and are hard wired for power and data transmission within the magazine. The digital processor communicates with the user display by radio frequency (“RF”), Bluetooth or Wifi signal. 
       FIG. 1  shows a cut-away schematic view of a firearm magazine in accordance with embodiments of the present invention. The magazine  100  stores rounds  102  of ammunition for use in the firearm. A round follower  104  is positioned within the magazine below the rounds  102 . A magazine spring  106  is positioned below the round follower  104  and applies an upward spring force on the round follower such that as each round is loaded into, fired and ejected from the firearm, the following round is pushed upward into a position that it can be engaged and loaded into the firearm firing chamber. 
     A contact sensitive variable resistance sensor  108  is positioned within the magazine  100 . In the illustrative embodiment, the resistor extends vertically along a rear sidewall  110  of the magazine. The sensor  108  may be any appropriate variable resistance sensor. In embodiments, the sensor may be a potentiometer. In further embodiments, the sensor may be a linear potentiometer. For example, embodiments may use a membrane potentiometer such as ThinPot potentiometer manufactured by Spectra Symbol. 
     As shown in  FIGS. 19-20 , embodiments of the sensor  108  may be a membrane potentiometer  1080  may include a top circuit  1082 , a circuit spacer  1084 , a bottom circuit  1086  and a bottom adhesive layer  1088 . The potentiometer  1080  may be a three-wire system with two resistive output channels and an electrical collector channel. By pressing a wiper  1089  down onto the top circuit  1082  the potentiometer produces the desired electrical output. The wiper  1089  is a non-conductive mechanism that depresses the top circuit  1082  actuating the potentiometer from the outside of the element. 
     The top  1082  and bottom  1086  circuits are separated by a spacer  1084 . The spacer may comprise 0.15 mm (0.006″) of adhesive build-up. Contact between the circuits occurs by pressure from the wiper  1089  on the top circuit  1082 , pushing down until the top circuit connects with the bottom circuit  1086  to create a potentiometric output. The required pressure may be between 1-3 Newtons. The potentiometer  1080  may also include a layer of adhesive  1088  that allows the potentiometer to be adhered to a surface. 
     Returning to  FIG. 1 , the sensor  108  is adhered to an inner surface  112  of the rear sidewall  110  of the magazine  100 . A wiper  114  that may comprise a stylus or plunger extends from a rear portion of the round follower  104  and contacts the sensor  108  with sufficient pressure to activate the sensor. The wiper may be made of any appropriate material, including metal, plastic or other materials as would be apparent to one of ordinary skill in the art. The wiper may be spring loaded to provide the appropriate pressure to the sensor  108 . 
     The magazine  100  may also include electronics compartment  116  that encloses electronics components. The electronics compartment is shown positioned adjacent a bottom wall  117  of the magazine, but the compartment could be positioned in other locations within the magazine, for example: along a magazine side wall, within or attached to the round follower  104  or inside the spring  106  coil. 
     Magazine  100  may also include an identification tag  119 . The tag  119  may be encoded with a unique serial or identification number. The unique number may be used to identify the particular magazine for communications with the display assembly as described below. The tag  119  may be mounted on an exterior surface of the magazine, may be housed within the electronics compartment  116 , including being attached to or integrally formed with electronics components, may be embedded within the magazine body ( 170 ) or may be positioned in another location on the magazine. The tag may contain optically readable information, such as a barcode or 2D barcode. Alternatively, the tag may comprise active radio or other transmission, or the tag may comprise a passive RFID tag. Identifying information provided by the tag may be permanently or persistently stored or may be generated by components of the magazine as needed to enable identification of the magazine. 
       FIG. 3  shows a schematic view of the sensor  108  and wiper assembly  114 . As discussed above, the magazine includes a wiper assembly  114  that may comprise a spring loaded plunger or stylus  118 . The stylus  118  contacts the sensor  108 , which may be a position sensitive variable resistance sensor. The sensor may include various electric connections. A power connection  120  may provide an appropriate voltage to operate the sensor. A ground connection  122  may connect the sensor to ground, and an output signal connection  124  may provide for the sensor to send a signal containing information regarding the position of the wiper  114  relative to the sensor and therefor relative to the round follower&#39;s position within the magazine. These signals may include an analog electrical signal that is proportional to the position of the wiper. 
       FIG. 4  shows a schematic view of components that may be included in the electronics compartment  116 . The compartment may include an analog to digital converter (“ADC”)  126 . The converter may have an input connection  128  that receives signals provided on the output connection  124  of the sensor  108 . The ADC converts an analog signal received from the sensor  108  into digital information. The digital information can then be sent on an output connection  134  of the ADC. The ADC may also include a power connection  130  and a ground connection  132 . 
     The electronics compartment  116  may also contain a digital signal processor (“DSP”)  136 . The DSP receives the digital information output by the ADC and converts the information into a signal that is suitable for transmission to a display capable of being read by the shooter. The DSP then outputs the digital signal on an output connection  138 . The DSP may also include a power connection  140  and a ground connection  142 . 
     The electronics compartment  116  may also contain a transmitter  144 . The transmitter receives the signal from the DSP  136  and transmits it to a display capable of being read by the shooter. The transmitter may use any of a variety of appropriate transmission methods and may include the necessary circuitry for using those transmission methods. For example, the transmitter may be a low power radio frequency transmitter, or the transmitter may use other communications protocols, including Bluetooth, WiFi or infrared. Alternatively, the transmitter may employ near field communication, with the transmitter  144  being the non-powered/read side of communication protocol. The transmitter  144  may include an antenna  146  appropriate to the transmission protocol being used. The transmitter  144  may also include a power connection  148  and a ground connection  150 . 
     The electronics compartment  116  may further include a battery  152  or other power source that provides electrical power to the power connections  130 ,  140 ,  148  of the sensor  108 , ADC  126 , DSP  136 , transmitter  144  and other components. In the schematic view of  FIG. 4 , the components of the electronics compartment are shown positioned adjacent to one another. However, it will be understood the various components, while in electronic/electrical connection, may be positioned at different locations within the magazine or firearm. 
       FIG. 2  shows a schematic view of a display assembly  160  that may be used in embodiments of the present invention. The display assembly  160  may include a receiver  154  that receives information sent from the transmitter  144  of the magazine  100 . The receiver may include an antenna  156  appropriate to the transmission protocol being used. The display assembly  160  may further include a display driver  158  and a display  162  that is capable of being read by the shooter. The display assembly  160  may further comprise a battery (not shown) to provide electrical power to the components of the display assembly. 
     The display  162  may comprise any appropriate display mechanism. For example, the display may comprise an LCD or LED screen. Alternatively the display may comprise an seven-segment display. The display may numerically display the number of rounds remaining in the magazine or it may display a gauge, bar graph or the like indicating the absolute or relative number of rounds remaining. The display may be configured to convey additional information beyond the number of rounds in the magazine. 
     The display may be located anywhere on the firearm that is visible to the shooter. The display may be positioned adjacent to a sighting device of the firearm or it may be positioned on a surface of the firearm&#39;s action, grip, barrel, etc. The display may be a separate component attached to a surface of the firearm or it may be integrated into the body of the firearm. Alternatively, the display may project the information to be displayed into the sighting optics of the firearm in the manner of a heads-up display. 
     The components of the display assembly may be contained in a single enclosure, or they may be dispersed over various locations on the firearm. For example, the receiver  154 , display driver  158  and display  162  may be positioned together adjacent to a rear sight of the firearm while the battery is positioned in a grip or stock of the firearm. 
       FIGS. 5-9  show a firearm magazine in accordance with the present invention. The magazine  100  is inserted into the receiver of a firearm. A latch  172  engages the receiver and retains the magazine in connection with the firearm. The magazine includes a magazine body  170  with a rear sidewall  110 . Rounds of ammunition are inserted into an opening  174  at the top end of the magazine. As the rounds are inserted a round follower  104  is pushed downward within the magazine. The round follower comprises a plunger  118  that contacts a sensor  108 . The plunger  118  is held against the sensor by a spring  176 . 
     The sensor  108  is positioned inside the magazine against an inner surface of the rear sidewall  110  such that the plunger  118  is held in contact with different portions along the length of the sensor as the round follower  104  moves up and down within the magazine in response to loading the magazine and firing the firearm. The sensor includes a wiring lead  188  that may include connectors for power  120 , ground  122  and transmission  124 . 
     The magazine includes a bottom wall  117 . The magazine may include a groove  178  formed adjacent to the bottom wall of the magazine. The groove  178  may engage a finger or extension  180  formed adjacent to the top surface  182  of an electronics compartment  116  such that the electronics compartment can be slidably engaged with the magazine body  170 . The electronics compartment  116  may house a battery  152 , an ADC  126 , a DSP  136  and a transmitter  144 . These elements may comprise separate electronic components or two or more elements may be combined into a single electronic component. The electronics component may include a removable rear wall  184  that allows access to the components positioned within the electronics compartment  116 . 
     The magazine may further comprise a reed switch  186  that is positioned along the rear sidewall  110  of the magazine body  170 . The reed switch may serve as an interrupt that signals to the electronic components of the magazine when the magazine has been installed into a firearm. For example, a compatible firearm may have a permanent magnet, for example a rare earth magnet installed in a forward portion of the trigger guard such that the magnet is adjacent to the reed switch when the magazine is installed. When the magazine is installed, the reed switch is activated and a signal is sent to one or more electronic components of the magazine indicating that the magazine is in place in a firearm. Alternatively, the reed switch may be used to close a power circuit within the magazine, providing power to the electronic components. The reed switch may, for example, be an RA, RS or RM series reed switch manufactured by Soway Tech Limited. 
       FIGS. 10-12  show additional details of the wiper assembly  114 . A spring ( 106 ) applies an upward force on the round follower  104 . The round follower  104  presses against the ammunition round  102  held in the magazine, moving upward in the magazine body  170  as the rounds  102  are fired by the firearm. A sensor  108  is positioned against an inside surface  112  of the magazine rear sidewall  110 . The sensor extends linearly along the sidewall at least between the highest and lowest points through which the round follower  104  travels during operation of the magazine between empty and full. 
     In the embodiments illustrated in  FIGS. 10-12 , a cavity  190  is formed in the round follower  104  adjacent a lower surface  192  of the follower. The cavity  190  faces the sensor and may be a cylindrical bore. A spring  176  is placed into the cavity  190 , and a plunger  118  is placed into the cavity against the spring such that the plunger is held in contact with the sensor with sufficient pressure to activate the sensor. 
       FIGS. 13-15  illustrate embodiments of the present invention in which the magazine is loaded with three rounds  102 . Having three rounds in the magazine, the round follower  104  is pushed downward a certain distance from its topmost position, and the cavity  190  of the round follower lines up with a portion of the sensor such that the plunger ( 118 ) presses against the sensor  108  at a distance  192  from the top end of the sensor. Operation of the sensor provides a signal indicative of this distance to the electronic components of the electronics enclosure  116 . For example, if a membrane potentiometer is used, the sensor provides an analog electrical signal to the ADC that corresponds to the distance from the top end of the sensor. The position of the plunger corresponds to a specific linear distance indicative of the number of rounds remaining in the magazine, three in this example. The ADC converts this analog signal to a digital signal, and the DSP  136  converts the signal into information that is indicative of how many rounds remain in the magazine. This information is passed to the transmitter  144  that sends the information to the display assembly. The display  162  of the display assembly then presents the information in a manner that is readable by the shooter. In this example, the display  162  is a screen that shows the number 03, indicating that three rounds remain. 
       FIGS. 16-18  illustrate embodiments of the present invention in which the magazine is empty. The magazine being empty, the round follower  104  is at its topmost position, and the cavity  190  of the round follower lines up with a portion of the sensor such that the plunger ( 118 ) presses against the sensor  108  at a distance  194  from the top end of the sensor. This distance  194  is less than the distance ( 192 ) when three rounds were present in the magazine. As described with respect to  FIGS. 13-15 , Operation of the sensor provides a signal indicative of this distance to the electronic components of the electronics enclosure  116 . This signal is appropriately processed, and information is passed to the transmitter  144  that sends the information to the display assembly. The display  162  of the display assembly then presents the information in a manner that is readable by the shooter. In this example, the display  162  is a screen that shows the number 00, indicating that no round remains. 
     This application describes various exemplary embodiments having various electronic components. The components shown and described herein may include more or fewer components, and each of the referenced components may itself include a single, separate component, may include multiple or may include multiple components mounted together or integrally formed. Alternatively, a single electronic component may provide the functionality of multiple components described herein or a the functionality of a single component as describe may be performed by multiple components. 
     The firearms and components of the present invention have been described herein as having certain exemplary features. However, it is not intended that the invention be limited to these illustrative embodiments, and it is contemplated that the present invention may include any compatible feature or configuration as would be understood by one of ordinary skill in the art.