Abstract:
An electro-mechanical firearm trigger mechanism for controlling the rate of fire for a firearm in automatic firing mode. The controlling being achieved through the use of a solenoid directed by a computer processor. The computer processor being connected to multiple sensors to instruct the solenoid on a rate of fire or to disengage automatic fire if needed.

Description:
FIELD OF THE INVENTION 
       [0001]    Embodiments of the invention relate generally to firearms. More particularly, embodiments of the invention relate to an electro-mechanical trigger mechanism for an automatic firearm. 
       BACKGROUND OF THE INVENTION 
       [0002]    It is known that firearms that have purely mechanical automatic trigger mechanisms, such as the type disclosed in U.S. Pat. No. 3,045,555 to Stoner, can operate with excessively high firing rates in an automatic firing mode. M16 type firearms using purely mechanical automatic trigger mechanisms can have rates of fire well in excess of 600 rounds per minute, particularly in models with shorter barrels. These high rates of fire may be problematic, as they can, among other things, affect the control and accuracy of the firearm, increase the accumulation of heat in the barrel, or result in unnecessary wastage of ammunition. 
         [0003]    High rates of fire affect the control and accuracy of the firearm due to muzzle climb, as there is insufficient time between consecutive discharges to allow the operator to return the firearm to its original point of aim. This is compounded by a desire to increase the portability and maneuverability of firearms by reducing weight and size, which respectively contribute to decreased stability and further increased rates of fire. 
         [0004]    In addition, the accumulation of heat in the barrel may contribute to erosion and wear in the barrel, and can further impact the accuracy of the firearm. 
         [0005]    It is, therefore, desirable to provide an electro-mechanical trigger mechanism for an automatic firearm to provide a controlled rate of fire when the firearm is operated in an automatic firing mode. 
       SUMMARY OF THE INVENTION 
       [0006]    In a first aspect, there is provided an electro-mechanical trigger mechanism for controlling automatic firing of a firearm, the electro mechanical trigger mechanism comprising a solenoid operatively connected to a sear disconnect of the firearm; and a processor, for controlling the solenoid; wherein, based on inputs to the processor, the processor controls a flow of current to the solenoid to control the automatic firing of the firearm. 
         [0007]    In a further aspect, there is provided a method of controlling an automatic firing mode for a firearm by controlling a rate of fire using an electro-mechanical trigger mechanism comprising determining that the firearm is in the automatic firing mode; and supplying a flow of current to a solenoid to control the rate of fire via a sear disconnect connected to the solenoid. 
         [0008]    Other aspects and features of embodiments will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    Embodiments of the invention will now be described, by way of example only, with reference to the attached Figures, wherein: 
           [0010]      FIG. 1  is a cross-sectional view of a portion of a firearm incorporating an electro-mechanical trigger mechanism; and 
           [0011]      FIG. 2  is a flow chart of a method of using an electro-mechanical trigger mechanism for controlling a firearm. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    In this disclosure, an embodiment of an electro-mechanical trigger mechanism and a method for using such a mechanism to control a firearm are disclosed. Embodiments of the invention may be applied to a wide variety of firearms, but is shown here in an embodiment with an automatic firearm, such as an AR-15, M16 or U.S. Pat. No. 3,045,555 (Stoner) type. 
         [0013]      FIG. 1  shows a first cross sectional view of a firearm  10  incorporating an electro-mechanical trigger mechanism. In one embodiment the electro-mechanical trigger mechanism  40  resides within a hand grip  12 . 
         [0014]    The electro-mechanical trigger mechanism  40  comprises a solenoid  26  which is in communication with, and controlled by, a processor  28 , such as a central processing unit (CPU) and is also connected to a hammer  20  and a trigger  22  via a sear disconnect  24 . 
         [0015]    A firing mode selector  14  provides an apparatus for switching operation of the firearm  10  between a safe mode, a semi-automatic mode, and an automatic mode as determined, or required, by a user of the firearm  10 . 
         [0016]    The solenoid  26  is also connected to a plunger  32  which extends between the solenoid  26  and the sear disconnect  24 . In one embodiment, the solenoid plunger  32  can be biased towards the sear disconnect  24  by a coil spring or an elastic member. 
         [0017]    The hammer  20  includes a primary sear abutment  56  and a secondary sear abutment  54 , and is pivotally mounted by a transversely oriented pivot pin  35 . 
         [0018]    The sear disconnect  24  includes a secondary sear  46  and is moveable between a catch position and a release position. In the catch position the secondary sear  46  engages the secondary sear abutment  54  and the hammer  20  is held in a cocked position. In the release position the secondary sear  46  is pivoted such that the secondary sear  46  disengages the secondary sear abutment  54  so that the hammer  20  is not retained by the secondary sear  46 . 
         [0019]    The sear disconnect  24  further includes a slotted opening  42  operative with pin  44  connected to the solenoid plunger  32 . This configuration connects the sear disconnect  24  and the solenoid  26 . In use, this configuration allows the solenoid  26  to engage the sear disconnect  24 , thus releasing it from the secondary sear  46  and allowing for automatic firing, when necessary. 
         [0020]    The CPU  28  is operatively connected to a power source, in the form of a battery  48 , a trigger sensor  50  which is used for sensing whether or not the trigger  22  is pulled, a firing mode sensor  52  which is used for sensing the position of the firing mode selector  14  and a timer  55  which is used to determine the rate of fire by the firearm  10 . It will be understood that the location of the CPU  28 , the battery  48 , the trigger sensor  50 , the firing mode sensor  52  and the timer  55  may be anywhere within the firearm  10  and not simply at the locations outlined in  FIG. 1 . In operation, the CPU  28  controls the supply of current from the battery  48  to the solenoid  26 , and includes circuitry or software instructions to apply a current pulse to the solenoid  26  for a pre-determined number of times, corresponding to a number of rounds to be fired to provide a burst fire mode. This is based on inputs which are received by the processor  28  from the various sensors located throughout the firearm  10 . Furthermore, a temperature sensor  58  is located within a barrel  57  of the firearm to provide temperature information to the CPU  28  so that the CPU can control the solenoid  26  based on this information. In alternative embodiments, the CPU  28  can receive other information which can assist in controlling the solenoid  26 . This other information can be in the form of a user input or could be information which is received from a firearm sighting system. 
         [0021]    In semi-automatic operation of the firearm, the firing mode selector  14  is set to semi-automatic and the electro-mechanical trigger mechanism  40  operates in a purely mechanical manner whereby the solenoid  26  is not used. In this situation, the CPU  28  may not be fully powered in order to conserve the battery  48 . When the firing mode sensor  52  transmits a signal to the processor that the semi-automatic mode has been selected, the processor does not allow current to be supplied to the solenoid  26 . 
         [0022]    In order to initiate the semi-automatic firing mode, the hammer  20  is cocked either from a previous use or through the user physically pulling back the bolt (not shown). The hammer  20  is held by the engagement between the primary sear abutment  56  and the primary sear  36 . 
         [0023]    When the trigger  22  is pulled, the hammer  20  is released, and engages a firing pin (not shown) to fire a round from the firearm and to cock the hammer  20 , which is caught and held by the engagement of the secondary sear abutment  54  and the secondary sear  46 . 
         [0024]    When the trigger  22  is released, the secondary sear  46  is released, but the hammer  20  remains cocked by the engagement of the primary sear abutment  36  and the primary sear  56  and this completes one cycle of ammunition firing in the semi-automatic firing mode. 
         [0025]    In automatic firing mode operation of the firearm, the firing mode selector  14  is set to automatic and the electro-mechanical trigger mechanism  10  operates in an electro-mechanical manner. The CPU  28  may be activated by the firing mode sensor  52  which transmits a signal to the CPU  28  indicating that the firing mode selector  14  has been set to automatic and the CPU  28  provides current to the solenoid  26  to control the firing of the firearm. 
         [0026]    In order to initiate the automatic firing mode, the hammer  20  is cocked either from previous use or by physically pulling back the bolt to cock the hammer  20 . The hammer  20  is held by the engagement of the primary sear abutment  56  and the primary sear  36 . 
         [0027]    When the trigger  22  is pulled, the hammer  20  is released, and engages a firing pin to fire a round from the firearm and cock the hammer  20 , which is caught and held by the engagement of the secondary sear abutment  54  and the secondary sear  46 . 
         [0028]    However, unlike semi-automatic mode, if the firing mode selector  14  is set to automatic and the trigger  22  is held in place, the CPU  28  provides current to cycle the solenoid  26  in accordance with a selected control methodology. Therefore, the CPU continues to control the necessary current to the solenoid  26  so that the firearm can continue to operate in the automatic firing mode. The trigger sensor  50  detects whether the trigger is pulled or released and provides that information to the CPU  28  so that the CPU recognizes that the solenoid  26  is to continually receive current to assist in controlling the firing rate of the firearm in that the CPU can control the flow of current to the solenoid  26  which directly affects the firing rate, or rate of fire 
         [0029]    In one embodiment, the control methodology may include setting or limiting a rate of fire based on signals received from the timer  55 , the barrel temperature sensor  58  or both. As long as the trigger  22  (detected by the trigger sensor  50 ) is held in place, the CPU  28  will operate the solenoid  26  to trip the sear disconnect  24  causing the secondary sear  46  to release the hammer  20 , and continuously engage the firing pin to fire a round from the firearm and re-cock the hammer  20 . The hammer  20  is caught and held by the engagement of the secondary sear abutment  54  and the secondary sear  46 , until the solenoid  26  cycles or the trigger  22  is released. If the trigger  22  remains held, the solenoid  26  cycles again allowing another round to be fired. 
         [0030]    When the trigger  22  is released, the hammer  20  is caught by the engagement of the primary sear abutment  56  and the primary sear  36  and held in the cocked position, and this competes one cycle of operation in automatic mode. In one embodiment, once the trigger sensor senses release of the trigger, a signal is transmitted to the processor to stop the flow of current to deactivate the solenoid. 
         [0031]    Referring now to  FIG. 2  a flow chart of a method for use of an electro-mechanical trigger mechanism in controlling a firearm is shown generally as  100 . Although this is shown as a sequential process, one skilled in the art will recognize that many of the steps may run in parallel and interrupt the stream to provide data, examples being at steps  114 ,  116  and  120 . 
         [0032]    Beginning at step  102 , a test is made by the processor  28  to determine the position or status of the firing mode selector  14 . In one embodiment, this can be performed by having the processor  28  communicating with or accessing the firing mode sensor  52  to retrieve the mode selector information. At step  104 , a test is made to determine if the safety of the firearm is on or if the firing mode selector has been set to safe mode. If the safety is on or the firing mode selector  14  is set to safe mode, the firearm is unable to fire (step  106 ) and processing returns back to step  102  to monitor the firing mode selected by the firing mode selector. At step  108 , a test is made to determine if the firing mode selector is set at semi-automatic by having the processor communicate with the firing mode sensor. If so the firearm is considered active and may operate in semi-automatic mode until the status or position of the selector  14  is changed. This is continually checked in step  102 . Should the test at step  108  indicate that the firearm is not semi-automatic, then it is fully automatic as can be confirmed by the processor and processing moves to step  114 . As discussed above, the processor continually checks the firing mode sensor to determine the selected firing mode. At step  114  a test is made to determine or control the rate of fire. In one embodiment, the CPU  28  obtains data from timer  55  which provides data on how quickly the firearm is discharging rounds. Processing then moves to step  116  where the barrel temperature is tested by barrel temperature sensor  58 . The barrel temperature is then transmitted to the processor so that the processor can further control the rate of fire, if necessary. At step  118 , if the barrel temperature is within an acceptable range for the firearm, processing moves to step  122  where a test is made to determine if the trigger  22  has been released by having the processor communicate with the trigger sensor, otherwise the firearm can continue to be used in automatic mode and the temperature of the barrel continued to be monitored (step  116 ). If the temperature is determined to be too hot, in one embodiment, the CPU can lower the rate of fire to reduce the amount of heat generated by controlling the current flow being supplied to the solenoid. In another embodiment, a signal may be transmitted from the CPU processor to the solenoid to power down the solenoid so that the firearm returns to the release position and therefore no longer in the automatic firing mode. At step  122 , if the trigger has been released, processing returns to step  102  until the firearm is be used again. 
         [0033]    While in automatic firing mode, steps  116 ,  118  and  122  can be cycled to determine if automatic firing should be disabled or the rate of fire reduced due to temperature (step  118 ) or by the release of the trigger (step  122 ). 
         [0034]    In the preceding description, for purposes of explanation, numerous details are set forth in order to provide a thorough understanding of the embodiments of the invention. However, it will be apparent to one skilled in the art that these specific details are not required in order to practice the invention. In other instances, well-known electrical structures and circuits are shown in block diagram form in order not to obscure the invention. 
         [0035]    The above-described embodiments of the invention are intended to be examples only. Alterations, modifications and variations can be effected to the particular embodiments by those of skill in the art without departing from the scope of the invention, which is defined solely by the claims appended hereto.