Abstract:
According to the present invention, a backstrap module is utilized in conjunction with a firearm having a security apparatus and a firing apparatus. The security apparatus authorizes operation of the firearm and generation of an electronic firing signal which is communicated to a firing probe of the firing apparatus. The backstrap module includes a molded shell which removably affixes the backstrap module to a frame of the firearm and houses the security apparatus. The backstrap module further includes a device for communicating the firing signal to the firing probe and provides for the energizing of the security apparatus and the firing apparatus.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     Some of the material disclosed herein is disclosed and claimed in the following pending U.S. patent application Ser. No. 09/205,391, filed Dec. 4, 1998, entitled: “FIRING CONTROL SYSTEM FOR NON-IMPACT FIRED AMMUNITION”; pending U.S. patent application Ser. No. 09/206,013, filed Dec. 4, 1998, entitled: “FIREARM HAVING AN INTELLIGENT CONTROLLER”; pending U.S. patent application Ser. No. 09/629745 filed Jul. 31, 2000 entitled: “A SECURITY APPARATUS FOR USE IN A FIREARM”; pending U.S. patent application Ser. No. 09/642753 filed Aug. 21, 2000 entitled: “AN ELECTRIC FIRING PROBE FOR DETONATING ELECTRICALLY-FIRED AMMUNITION IN A FIREARM”; pending U.S. patent application Ser. No. 09/642269 filed Aug. 18,2000 entitled: “A SLIDE ASSEMBLY FOR A FIREARM”; pending U.S. patent application Ser. No. 09/629531 filed Jul. 31, 2000 entitled: “A TRIGGER ASSEMBLY FOR USE IN A FIREARM HAVING A SECURITY APPARATUS”; pending U.S. patent application Ser. No. 09/629532 filed Jul. 31,2000 entitled: “A BACKSTRAP MODULE CONFIGURED TO RECEIVE COMPONENTS AND CIRCUITRY OF A FIREARM CAPABLE OF FIRING NON-IMPACT FIRED AMMUNITION”; pending U.S. patent application Ser. No. 09/643024 filed Aug. 21,2000 entitled: “A METHOD OF ASSEMBLING A FIREARM HAVING A SECURITY APPARATUS”; pending U.S. patent application Ser. No. 09/629534 filed Jul. 31, 2000 entitled: “AN AMMUNITION MAGAZINE FOR USE IN A FIREARM ADAPTED FOR FIRING NON-IMPACT DETONATED CARTRIDGES”; pending U.S. patent application Ser. No. 09/616722 filed Jul. 14, 2000 entitled: “AN ELECTRONICALLY FIRED REVOLVER UTILIZING PERCUSSIVELY ACTUATED CARTRIDGES”; pending U.S. patent application Ser. No. 09/616696 filed Jul. 14,2000 entitled: “AN ELECTRONIC SIGHT ASSEMBLY FOR USE WITH A FIREARM”; pending U.S. patent application Ser. No. 09/616709 filed Jul. 14, 2000 entitled: “A FIRING MECHANISM FOR USE IN A FIREARM HAVING AN ELECTRONIC FIRING PROBE FOR DISCHARGING NON-IMPACT FIRED AMMUNITION”; pending U.S. patent application Ser. No. 09/616739 filed Jul. 14, 2000 entitled: “A FIRING PROBE FOR USE IN A NON-IMPACT FIREARM”; and pending U.S. patent application Ser. No. 09/616837 filed Jul. 14, 2000 entitled: “A SECURITY APPARATUS FOR AUTHORIZING USE OF A NON-IMPACT FIREARM”, which are hereby incorporated by reference as part of the present disclosure. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to firearms and, more particularly, to a backstrap module which mounts and protects a firing apparatus and security apparatus which authorize, produce, and deliver a firing signal to an electronically-discharged ammunition cartridge. 
     BACKGROUND OF THE INVENTION 
     Revolvers have been produced for over a century and, although many components in their firing mechanism have remained relatively unchanged in function and design, continuous efforts have led to improvements in safety, manufacturing, and operation of revolvers. In recent decades, the evolution of improved electronics technology and capabilities has prompted efforts to incorporate electronics into firearms to further improve the cost, manufacturability, and performance of the firearms. For example, a mechanical trigger is displaced by an electronic solenoid in U.S. Pat. No. 4,793,085, entitled “ELECTRONIC FIRING SYSTEM FOR TARGET PISTOL”. U.S. Pat. No. 5,704,153, entitled “FIREARM BATTERY AND CONTROL MODULE”, incorporates a processor into its ignition system to fire conventional percussion primers. 
     Electronics have also been incorporated into ignition systems for firearms that use non-conventional primers and cartridges. An “ELECTRONIC IGNITION SYSTEM FOR FIREARMS”, U.S. Pat. No. 3,650,174, describes an electronic control system for firing electronically-primed ammunition. The electronic control of the &#39;174 Patent, however, is hard-wired and lacks the multiple sensor interfaces of the programmable central processing unit that is found with the present invention. A “GUN WITH ELECTRICALLY-FIRED CARTRIDGE”, U.S. Pat. No. 5,625,972, describes an electrically-fired gun in which a heat-sensitive primer is ignited by voltage induced across a fuse wire extending through the primer. A “COMBINED CARTRIDGE MAGAZINE AND POWER SUPPLY FOR A FIREARM”, U.S. Pat. No. 5,272,828, shows a laser ignited primer in which an optically transparent plug or window is centered in the case of the cartridge to permit laser ignition of the primer. Power requirements to energize the laser, as well as availability of fused and/or laser-ignited primers are problematic however. An “ELECTRONIC FIREARM AND PROCESS FOR CONTROLLING AN ELECTRONIC FIREARM”, U.S. Pat. No. 5,755,056, shows a firearm for firing electrically activated ammunition having a cartridge sensor and a bolt position sensor. The technology of the &#39;056 Patent, however, is limited to a firearm with a bolt action. None of the prior art to date fully integrates an electronic control system into a revolver for consistently and effectively firing a non-impact ammunition primer. The present invention is directed to such a revolver. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     One object of the present invention is to provide a backstrap module that encloses, protects and integrates a security apparatus and a firing apparatus into a revolver. 
     It is another object of the present invention to provide a backstrap module that secures an arrangement of sensors that communicate with the security apparatus and the firing mechanism. 
     According to the present invention, a backstrap module is utilized in conjunction with a firearm having a security apparatus and a firing apparatus. The security apparatus authorizes operation of the firearm and generation of an electronic firing signal which is communicated to a firing probe of the firing apparatus. The backstrap module includes a molded shell which removably affixes the backstrap module to a frame of the firearm and houses the security apparatus. The backstrap module further includes a device for communicating the firing signal to the firing probe and provides for the energizing of the security apparatus and the firing apparatus. 
     One advantage of the present invention is that the backstrap module is self contained and easily removable from the frame of the revolver. 
     These and other objects, features and advantages of the present invention will become more apparent in the light of the following detailed description of best mode embodiments thereof as illustrated in the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a rear perspective of a revolver according to the present invention showing a backstrap module and a sight assembly as assembled on a frame; 
     FIG. 2 is a somewhat reduced exploded perspective view of the revolver of FIG. 1 showing the backstrap module, sight assembly, and a finger grip attachment removed from the frame, and a side plate cut away to partially illustrate a firing mechanism; 
     FIG. 3 is a somewhat enlarged fragmentary perspective view of the revolver of FIG. 1 shown with the backstrap module separated from the frame; 
     FIG. 4 is a frontal perspective view of the backstrap module of FIG. 3; 
     FIG. 5 is a rear perspective view of the backstrap module of FIG. 3; 
     FIG. 6 is an enlarged rear perspective view of the finger grip attachment of FIG. 2; 
     FIG. 7 is a plan view of a circuit board arrangement adapted to mount within the backstrap module of FIG. 2; 
     FIG. 8 is an schematic side view of the circuit board arrangement of FIG. 7 shown with an array of electronics mounted thereto and installed in the backstrap module; 
     FIG. 9 is an enlarged, fragmented and exploded perspective view of the frame shown in FIG. 2 illustrating a disassembled firing probe assembly removed from a firing probe bore; 
     FIG. 10 is an enlarged, fragmented plan view of the frame of FIG. 2 shown with a small portion of the backstrap module in phantom cut away to illustrate the firing mechanism in a recovered position; 
     FIG. 11 is a somewhat reduced, exploded frontal perspective view of the firing mechanism of FIG. 10; 
     FIG. 12 is a somewhat reduced, exploded rear perspective view of the firing mechanism of FIG. 10; 
     FIG. 13 is a plan view similar to that of FIG. 10 except shown with the firing mechanism in a partially-cocked position; 
     FIG. 14 is a plan view similar to that of FIG. 10 except shown with the firing mechanism at a let-off position and the transfer bar fragmented to illustrate the hammer foot; 
     FIG. 15 is a plan view similar to that of FIG. 10 except shown with the firing mechanism at a fired position; 
     FIG. 16 is a plan view similar to that of FIG. 10 except shown with the firing mechanism at a partially recovered position; 
     FIG. 17 is an enlarged perspective view of the sight assembly of FIG. 2; 
     FIG. 18 is a fragmented perspective view of the sight assembly of FIG. 17 illustrating an arrangement of front and rear optical fibers and light gathering guides; 
     FIG. 19 is an enlarged perspective view of the underside of the sight assembly shown in FIG. 17; and 
     FIG. 20 is a schematic side view of an electrically fired revolver utilizing percussively actuated cartridges. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIGS. 1 and 2, a revolver  10  with a muzzle end shown to the left in FIG. 1, and a rear end to the right, includes a barrel  12  having a bore  13  and received in a barrel shroud  14  mounted on a frame  16 . The frame  16  has a generally rectangular opening  18  therethrough which receives a cylinder  20  rotationally hung on a yolk  21  that swings at a right angle to the frame  16 . A trigger  220  is pivotally supported on the frame  16  by a pivot pin, while a ratchet arm is pivotally attached to the trigger  220  and configured conventionally to index a plurality of cylinder chambers  24  into axial alignment with the bore  13  in a known manner. For a discussion of the function and purpose of the yoke, cylinder, and ratchet, reference is made to U.S. Pat. No. 517,152, issued to Daniel B. Wesson on Mar. 27, 1894, for a “SWINGING CYLINDER AND TRIGGER LOCK FOR REVOLVERS”, which is hereby incorporated as part of the present disclosure. The right side of the frame  16  defines an inner cavity  26  which mounts and protects an arrangement of mechanical components which cock and fire the revolver  10 , collectively referred to as a firing mechanism  27 . Conventional screws are used to attach a side plate  28  to the frame  16  to enclose the cavity  26  and prevent entry of debris into the cavity  26 . Therefore, as the revolver is held in its sighting position, the left side of the revolver is that shown in FIG. 1, and the right side shown as disassembled in FIG.  2 . 
     The revolver  10  of the present invention includes many mechanical components having functions understood well in the industry. However, as the revolver  10  is configured to discharge electrically-fired ammunition, such as developed by Remington Arms Company and referred to as the Conductive Primer Mix described in U.S. Pat. No. 5,646,367, many of the well-known mechanical components have been modified, eliminated, or replaced as needed. 
     A backstrap module  30  is configured to contain and protect most of the electronics, including a battery  31 , and the module  30  mates with the rear end of the revolver  10  in a direction indicated by arrow  32 . An ergonomically-designed finger grip attachment  34  is moved in a direction generally indicated by arrow  36  to engage the backstrap module  30  and a frame post  37 , thereby forming a conventional handgrip  38  which depends from the rear of the frame  16 . The frame post  37  has parallel, opposed side surfaces  39  and a contoured front surface  40  which are contacted by complimentary surfaces of the finger grip attachment  34  during assembly of the revolver  10 . Once the backstrap module  30  and finger grip attachment  34  are positioned onto the frame  16 , a lower mount screw  41  is inserted through the finger grip attachment  34  to secure the handgrip  38 . 
     A sight assembly  42  is received within a top edge  46  of the frame  16  and the barrel shroud  14 , and includes a lower housing  48  and a pair of longitudinal dovetails  50  which are oriented parallel to the top edge  46  when installed on the revolver  10 . The frame  16  has a dovetail receiver  52  concealed within the top edge  46  of the frame  16  and shroud  14  to engage the dovetails  50 . During assembly, the dovetails  50  are moved forwardly into the shroud  14  until the lower housing  48  of the slide assembly  42  is positioned over an associated housing receiver  54  in the frame  16 . The lower housing  48  is then pressed downwardly into the housing receiver  54  of the frame  16  and secured with a sight assembly mount screw  58 . 
     Referring to FIGS. 3-6, the backstrap module  30  includes upper and lower keys  60 ,  62  which face forwardly to engage upper and lower key slots  64 ,  66  of the frame  16 . The finger grip attachment  34  has parallel edges  68 , which engage associated slots  72  of the backstrap module  30 , preventing the frame  16  from releasing or disengaging from the lower portion of the module  30 . A U-shaped channel with parallel sides  78  and a forward face  80  mates against the parallel sides  39  and front surface  40  of the frame post  37  to prevent lateral movement of the finger grip attachment  34  on the frame  16 . 
     The backstrap module  30  includes left and right housing halves  86 , 88  which are molded from plastic and sealed together after the electronic components are arranged and mounted within the housing. The housing halves  86 , 88  are preferably injection molded from a rigid dielectric material such as Nylon or plastic which is capable of enduring the hostile environment of the revolver during normal use. The halves  86 ,  88  include known types of interior features, which effectively retain and mount the electronic components. 
     An outer seal  90  is molded from soft-touch plastic and includes five buttons  91  configured to actuate a complimentary array of dome switches positioned underneath, as discussed in detail below, the dome switches are used by the operator to perform various operational functions prior to firing the revolver  10 , as discussed in detail below. A metallic firing probe  95  is insert molded in position during fabrication of the housing halves  86 ,  88  in an orientation which will be discussed below. Two transfer bar guides  96  are located and configured to engage, support, and guide the firing mechanism  27  during later stages of its actuation. A battery holder  97  defines a generally-cylindrical, elongated blind bore sized to receive the battery  31  which energizes the circuitry in the revolver. The battery is a model DL123ABU manufactured by Duracell, but other comparable battery types are readily available. 
     Referring to FIGS. 7-8, a circuitboard arrangement  100  is configured for mounting within the backstrap module  30  to organize and mount the electronic components collectively referred to as a circuit assembly  101 . The circuit assembly  101  receives electronic and mechanical inputs from the operator and produces a firing signal having a minimum of 130-volt once the firing mechanism  27  has been successfully actuated. 
     The circuit assembly  101  is divided into two collections of components, which are referred to as a security apparatus and a firing apparatus. Each apparatus has distinct function in the overall operation of the revolver  10 . The security apparatus has the broadly defined function of authorizing the firing apparatus to produce the firing signal. Before the security apparatus authorizes the firing apparatus to produce the firing signal, a plurality of input signals must be received by the security apparatus, which are indicative of compliance with operational parameters of the revolver. 
     The operational parameters include: a properly entered personal identification number of a firearm operator; a signal indicating the firearm is being held properly; a signal from the firing mechanism indicating its movement toward its firing position; and a signal indicative of the firing probe contacting a properly-loaded ammunition cartridge. Each of the signals, and the specific sequence in which they are produced, is discussed in detail below. 
     Once the required plurality of operational parameters is received by the security apparatus, a discharge authorization signal is produced and sent to the firing apparatus. The high-voltage firing signal is produced by the firing apparatus and transmitted to the cartridge via hardware discussed in detail below. The firing apparatus includes a fly-back circuit which uses energy from the 3-volt battery to generate the high-volt firing signal using known capacitive discharge techniques. 
     A rigid main circuitboard  102  mounts a majority of the components, which comprise the circuit assembly  101 , and is of the general type known in the electronics industry for surface-mounting or post-mounting components. An arrangement of flexible circuitboard portions is integrated with the rigid circuitboard  102  and are configured to arrange various components in specific orientations which efficiently utilize space which is available within the module. Each flexible circuitboard portion is merely an extension of the main circuitboard but imbedded in flexible resin to maintain a flexibility that allows components to be manipulated into desired configurations and/or orientations within the backstrap module. 
     The circuitboard arrangement  100  includes: the main circuitboard  102 ; a first flexible portion  104 , second and third flexible portions  106 ,  108 ; an input device  110 ; a high voltage mountboard  112 ; and a liquid crystal display (LCD) mountboard  114 . The first flexible portion  104  extends between the main circuitboard  102  and the input device  110 . The second flexible portion  106  extends between the main circuitboard  102  and the high-voltage mountboard  112 , and the third flexible portion  108  extends between the high-voltage mountboard  112  and the LCD mountboard  114 . 
     A ground strap  118  extends forwardly from the main circuitboard  102  and through the backstrap module housing to engage and electrically ground the frame  16  to the circuitboard arrangement  100 . The input device  110  is incorporated directly into the conductive elements of the arrangement  100 , and includes the dome switches  120  which are located in the handgrip  38  so that a high percentage of users is able to actuate any of the switches  120  while gripping the revolver  10  under normal operating conditions. 
     The high-voltage mountboard  112  mounts an arrangement of inductors, one of which is indicated by numeral  126 , a capacitor  128 , the firing probe  95 , a three-volt battery  131 , and a hammer terminal  132 . The inductor  126  is included in a “fly-back” circuit, which is energized by the battery to produce the firing signal, or energy pulse, that is stored temporarily in the capacitor  128 . The firing probe  95  includes an anchor post  134 , which is used to solder the probe  95  to the high-voltage mountboard  112 . The hammer terminal  132  is a flexible metal strip that is contacted by the firing mechanism to close an electrical input circuit in the processor. 
     The third flexible portion  108  extends between the high-voltage mountboard  112  and a LCD mountboard  114 . A LCD  140  is mounted to the LCD mountboard  114  and is positioned centrally between the backstrap module housing halves  86 . 88  to display electronic information for the operator in the form of readable text and/or symbols. A plurality of signals and/or information can be programmed for display on the LCD  140 , including whether or not the firearm has been authorized for use or is in the condition to be fired, and whether or not the hand grip is being grasped properly by the user. Additional information, which can be displayed includes the level of energy stored within the battery, and whether the firearm is on or is in a standby mode. 
     A light emitting diode (LED)  144  and photosensor circuitboard  146  are attached to the LCD mountboard  114  via a mount post  150 , and configured for use with the sight assembly  42  (seen in FIG. 2) to illuminate the front and rear sights for the revolver operator. A photosensitive cell  152  is incorporated into the photosensor circuitboard  146  to receive ambient light received from the sight assembly  42  and produce an electronic signal for the ciruitboard  146  which corresponds to the level of ambient light surrounding the revolver at any given time. Details of the circuitry within the circuitboard  146  are considered within the grasp of an individual skilled in the applicable art and will not be discussed further. 
     The photosensitive cell  152  is a cadmium sulfide ambient light cell manufactured by Clairex and is capable of measuring levels of ambient light and translating the levels into light corresponding signals for transmission to the processor. A high-intensity LED that has been used successfully in the revolver is a model TLGE160 manufactured by Toshiba. 
     An external terminal connection  156  is positioned in the handgrip  38  to receive a complimentary connector of an external device (not shown) used to communicate with the processor. The external device can be one of any number of components used for tasks such as entering an authorization code using a separate biometric or other similar device, interrogating and/or changing programmed code in the processor, changing an authorization code and/or factory serial code, determining and/or changing control parameters of certain components. 
     Referring to FIG. 9, a firing probe assembly  160  is assembled and engaged between the frame  16  and backstrap module  30 , and includes the firing probe  95  and a probe tip  162  biased forwardly by a probe spring  164 . An actuator bushing  168  defines a tip bore  167  with a countersunk rear end that slidably receives the probe tip  162 , the probe spring  164 , and the firing probe  95 . The actuator bushing  168  is slidably disposed within a frame bore  170  defined on the bore axis. An actuator spring  169  is captured within an annular space formed between the actuator bushing  168  and the frame bore  170 . 
     The firing probe  95  includes the anchor post  134 , a shank portion  172  and a tube  173 . As shown in FIG. 8, the anchor post  134  is soldered to the high voltage mountboard  112  in the backstrap module  30 . The tube  173  defines a blind bore  174  that loosely receives the probe spring  164 . 
     The probe tip  162  is pressed forward by the probe spring  164  into electrical contact with a cartridge in the cylinder, and includes a rounded front end and a conical rear lip  176 . The contour of the front end compliments a dimple in the primer of the cartridge so that the probe tip  162  consistently centers itself against the cartridge. The rear lip  176  is configured to be captured by a complimentary conical seat  178  defined in the tip bore  167  of the actuator bushing  168 . The probe tip  162  has a flat rear surface which bears rearwardly against the probe spring  164  at all times and against the tube  173  when the firing mechanism is recovered. Once firing probe assembly  160  is installed in the frame  16 , the probe tip  162  protrudes through the bore  167  of the actuator bushing  168 , and the rear lip  176  is captured between the conical seat  178  of the actuator bushing  168  and the tube  173  of the firing probe  95 . The probe spring  164  is selected to provide a force that is able to move the probe tip rapidly in response to actuation of the firing mechanism  27 . 
     The actuator bushing  168  is defined by cylindrical front and rear portions  186 ,  188  having dissimilar outer diameters that form a step  190  therebetween. The counterbored tip bore  167  slidably receives the firing probe  95 , and the seat  178  retains the lip  176  of the probe tip  162 . Thus, once assembled, axial movement of the probe tip  162  in the forward direction is governed by the axial location of the seat  178  of the actuator bushing  168 . The bushing  168  has an annular drive surface  196  facing rearwardly, which is contacted by the firing mechanism as discussed in detail below. 
     The rear end of the frame bore  170  is double-counterbored and the front end of the bore  170  has a single counterbore  206 . The double rear counterbore forms first and second annular seats  202 ,  204  which receive, respectively, the step  190  of the actuator bushing  168  and the actuator spring  169 . The actuator spring  169  fits over the front cylindrical portion  186  of the actuator bushing  168  and bears rearwardly against the step  190  of the bushing  168  and forwardly against the second seat  204  of the bore  170 . The first seat  202  of the bore  170  governs maximum forward travel of the actuator bushing  168  by engaging the step  190  of the bushing  168 . 
     The front counterbore  206  of the bore  170  has a diameter and depth which are selected to tightly receive an annular recoil plate bushing  210  which, with the frame  16 , forms a recoil plate  212 . The recoil plate bushing  210  defines a probe tip bore  214  aligned on the barrel axis which is configured to slidably receive the probe tip  162  that moves into and out of electrical engagement with the cartridge on the barrel axis. The bushing  210  is molded from a high-strength Zirconia ceramic material to withstand highly repetitive revolver firing forces and electrically insulate the frame  16  from the probe tip  162 . The bushing  210  has a front surface with a slightly convexed or crowned shape so that cartridges are smoothly indexed into their firing positions and axial play of any cartridge in the cylinder is taken up by the bushing  210 . 
     In operation, when the firing mechanism  27  is actuated with an intent to fire the revolver  10 , the drive surface  196  of the transfer bar is impacted by the firing mechanism, thereby driving the actuator bushing  168  in the forward direction. Forward movement of the actuator bushing  168  compresses the actuator spring  169  against the second seat  204  of the frame bore  170 . Accordingly, the conical seat  178  of the actuator bushing  168  is also moved forward, thereby allowing the probe tip  162  to move forward under force of the probe spring  164 . 
     The probe tip  162  has a low mass compared to the spring constant of the probe spring  164 , and the probe spring  164  is therefore able to move the probe tip  162  in rapid response to the axial movement of the actuator bushing  168 . 
     When the firing mechanism is recovered, rearward displacement of the actuator bushing, and hence the probe tip  162 , is governed or limited by the axial location of the tube  173  of the firing probe  95 . The tube  173  is located to allow the probe tip to retract a distance of approximately 0.003 inches (three thousandths of an inch) within the front surface of the bushing  210 . 
     Now turning to FIGS. 10 and 11, the firing mechanism  27  of the present invention differs substantially from known revolvers in both function and design, and the individual components will therefore be introduced in detail before discussing the mechanical cooperation which ultimately fires the revolver. The firing mechanism includes a trigger  220 , a hammer  222 , a sear  224 , a transfer bar  226 , a rebound  228 , a main spring  229 , a stirrup  230 , and a link  232 . A connector link  233  is coupled between the trigger  220  and the rebound  228  to compress the main spring  229 . 
     A rotator arm  234 , or ratchet arm, has a configuration and function known well in the industry to index the cylinder and its assembly and operation with the trigger  220  are described in detail in U.S. Pat. No. 520,468, issued to Daniel B. Wesson for “A REVOLVER LOCK MECHANISM”, and hereby incorporated by reference as part of the present disclosure. 
     Movement of the entire firing mechanism  27  is governed predominantly by three pivot pins which mount and secure the firing mechanism  27  in the cavity of the frame  16 . The stirrup  230  is pivotally mounted by a stirrup pin  235 , the hammer  222  is pivotally mounted by a hammer pin  236 , and the trigger is pivotally mounted by a trigger pin  237 . The frame  16  has a contoured cam surface  238  located and shaped within the cavity  26  to guide the transfer bar  226  during early stages of firing mechanism  27  actuation described below. 
     The trigger  220  includes a trigger post  239  with a flat upper surface, which bears generally vertically against the sear  224  during early stages of firing mechanism actuation. The trigger post  239  partially defines a trigger pocket  240  that receives the transfer bar  226  throughout the entire cycle of firing mechanism  27  actuation. The connector link  233  has a forward end pivotally attached to the trigger  220 , and a ball  241  at its rear end, which is received in a socket  242  of the rebound  228 . 
     The rebound  228  has an underside and lateral outer surfaces which are generally flat to allow the rebound  228  to slide freely within the cavity of the frame  16  during actuation of the firing mechanism  27 . Accordingly, the frame  16  and the side plate  28  have associated inner surfaces, which slidably retain the rebound  228 . A hammer stop  243  extends upwardly from the top side of the rebound  228  to engage the hammer  222  during recovery of the firing mechanism  27 . The rear end of the rebound  228  defines a blind bore  244 , which receives the front end of the main spring  229 . The rear end of the main spring  229  is captured within the stirrup  230 . 
     Referring to FIGS. 11-12, the hammer  222  includes a central core  245 , and upper and lower narrowed portions  246 ,  247  straddled by upper and lower pairs of contoured cam surfaces  248 ,  250 . The core  245  defines a transverse bore  252  through the hammer  222 , which receives the hammer pin  237 . The upper narrowed portion  246  has a thickness, which is less than the distance between the transfer bar guides  96  of the backstrap module  30  (shown in FIG.  6 ), so that movement of the hammer  222  is not obstructed by the backstrap module  30 . A substantially flat striker surface  256  functions as the modern counterpart to the pointed hammer portion, or firing pin, of a conventional hammer which uses inertia to ignite a conventional percussion cartridge. An upper abutment  258  extends perpendicularly from the right side of the hammer  222  and is configured to contact, or electrically engage, the hammer terminal  132  mounted to the backstrap module  30  (shown in FIG. 8) during actuation of the firing mechanism  27 . The upper cam surfaces  248  are configured to cooperate with two parallel spring members  259  of the transfer bar  226  in maintaining proper alignment and position of the transfer bar  226  with respect to the firing axis during actuation of the firing mechanism  27 . 
     The lower narrowed portion  246  corresponds in thickness to the upper narrowed portion  246 , and includes the lower cam surfaces  250 , a rebound abutment  262  and a hammer foot  264 . The rebound abutment  262  extends downwardly to rest against the rebound  228  when the firing mechanism is recovered. The cam surfaces  250  are configured, spaced apart, and oriented to function as rearward bearing surfaces for a pair of heels  268  of the transfer bar  226  during early stages of firing mechanism actuation. The hammer foot  264  extends generally forwardly and is configured to engage within the trigger pocket  240  of the trigger  220  during the later stages of firing mechanism actuation. 
     The hammer  222  also defines a sear pocket  270  configured to retain and control movement of the sear  224 . A pivot point  272  of the sear  224  rests in a corner  276  of the sear pocket  270 , and a lip  278  of the sear  224  engages a complimentary edge  280  of the sear pocket  270 , thereby effectively defining the range of angular motion of the sear  224  within the sear pocket  270 . A sear spring  284  is disposed between the sear  224  and sear pocket  270  to bias the sear  224  outwardly into engagement with the hammer trigger post  239 . 
     A link pocket  288  is defined on the underside of the hammer  222  to receive and pivotally retain a forward hook  290  of the link  232 . The link pocket  088  is partially enclosed on its left and right sides so that the link  232  remains centered within the link pocket  288  during firing mechanism actuation. The link  232  includes a rear hook  294  configured with a shape similar to that of the forward hook  290  to pivotally engage the stirrup  230 . 
     The front side of the stirrup  230  defines a blind, tapered bore  298 , and a transverse link pin  299  is molded into an upper end of the stirrup during fabrication. The link pin  299  pivotally receives the rear hook  294  of the link  232 , and the blind bore  298  receives the main spring  229 . The aforementioned taper in the bore  298  prevents the stirrup  230  from binding the main spring  229  during firing mechanism actuation. 
     The transfer bar  226  is configured to be moved by the trigger  220  into and out of engagement with the actuator bushing  168 , and includes the spring members  259 , left and right legs  310 , and a forked upper end  312 . The legs  310  are spaced apart from one another to loosely straddle the sear  224  and lower narrowed portion  247  of the hammer  222 , and each leg  310  includes a heel  268  and a foot  314 . Each foot  314  extends forwardly into the trigger pocket  240  of the trigger  220 , and each heel  268  bears rearwardly against one of the lower cam surfaces  250  of the hammer  222  during initial stages of firing mechanism actuation. 
     The forked upper end  312  includes left and right driver surfaces  315 , which straddle the firing probe assembly and rest against the actuator bushing when the transfer bar is in its firing position. A flat yoke  316  faces rearwardly to receive a hammer blow when the firing mechanism is actuation. In other words, when the transfer bar is in its firing position, the yoke  316  is aligned in the rotational path of the striker surface  256  of the hammer  222 . In the firing position, the front side of the upper end  312  rests against the annular drive surface  196  of the actuator bushing  168  on diametrically opposed sides of the bore  167 . The transfer bar  226  is molded from nylon or other dielectric material capable of withstanding highly repetitive impact forces from the hammer  222  during normal use of the revolver. 
     During initial stages of firing mechanism  27  actuation, the transfer bar  226  bears against the contoured cam surface  238  of the frame  16  while moving upwardly in the aforementioned camming action toward the firing probe assembly  160 . When moved further toward the firing position by the trigger  220 , the upper end  312  of the transfer bar  226  bears rearwardly against the transfer bar guides  96  of the backstrap module  30 . The guides  96  ensure that the transfer bar  226  is aligned properly with the actuator bushing  168  before being struck by the hammer  222 . Proper transfer bar alignment ensures that the impact force of the hammer  222  is transmitted properly and smoothly along the barrel axis without jamming or cocking the actuator bushing  168  in the frame  16 . 
     The spring members  259  extend from the rear side of the transfer bar  226  generally in the downward direction to straddle the upper narrowed portion  246  of the hammer  222  and bear against the upper cam surfaces  248  during initial actuation stages of the firing mechanism  27 . The spring members  259  act in unison to assist alignment between the transfer bar  226  and the firing probe assembly  160 . 
     Operation of the firing mechanism  27  is best explained with reference to several known stages of actuation, including: a recovered position shown in FIG. 10; a partially-cocked position shown in FIG. 13, where the trigger is being pulled by the operator; a “let-off” position shown in FIG. 14, beyond which point the trigger disengages from the sear and allows the hammer to fall; a fired position shown in FIG. 15, where the hammer has fallen and impacted the actuator bushing; and a partially-recovered position shown in FIG. 16, where the operator has partially released the trigger toward the recovered position to complete a cycle of the firing mechanism. 
     Referring back to FIG. 10, the trigger post  239  of the trigger  220  is not loaded against the sear  224  when the firing mechanism is in the recovered position. Instead, the hammer  222  is resting against the hammer stop  243  of the rebound  228 . The foot  210  of the transfer bar  226  is captured within the trigger pocket  240 , and the spring members  259  of the transfer bar  226  are unloaded by the hammer  222 . 
     When the trigger  220  is pulled, as shown in FIG. 13, the trigger post  239  rotates upwardly into contact with the sear  224  and the sear  224  forces the hammer  222  into a counterclockwise rotation. Rotation of the hammer  222  forces the stirrup  230 , via the link  232 , to rotate in a clockwise direction. It is apparent, then, that when the trigger  220  is pulled, the rebound  228  is pushed rearwardly and compresses the main spring  229 . Simultaneously, however, because the trigger  220  rotates the stirrup  230  via the hammer and link, the mainspring  229  is compressed further from the rear. 
     In this early stage of actuation, the spring members  259  bear against the upper cam surface of the hammer  222 . Accordingly, the transfer bar  226  is pushed generally forwardly and into the camming action against the contoured surface  238  of the frame  16 . 
     As the hammer  222  is rotated by the sear  224 , the contour of the upper cam surfaces  248  effectively moves the cam surfaces  248  away from the spring members  259  as the hammer rotates. The transfer bar  226  is simultaneously pushed upwardly and engaged against the transfer bar guides  96  of the backstrap module  30  (seen in FIG.  3 ). Eventually, the sear  224  reaches a point where it can no longer remain engaged with the trigger post  239  of the trigger  220 . At this point, the foot  264  of the hammer  222  is configured to engage itself within the trigger pocket  240  of the trigger  220 . Accordingly, the hammer  222  is rotated further in the counterclockwise direction and the main spring  229  is compressed further at its front and rear ends. 
     Referring to FIG. 14, the “let-off” point (point just prior to let-off is indicated by arrow  255 ) is reached when the foot  264  of the hammer  222  can no longer remain engaged within the trigger pocket  240  with continued rotation of the trigger  220 . At this point, the main spring  229  is fully compressed and the transfer bar  226  has reached the firing position at rest against the annular drive surface  196  actuator bushing  168  (the forked upper end  266  is seen from its side in the reference figure). Once the hammer  222  disengages from the trigger  220 , as seen in FIG. 15, the hammer rotates immediately toward the transfer bar  226  under force of the compressed main spring  229 . Just before striking the transfer bar  226 , the hammer  222  engages the hammer terminal  132  hanging from the backstrap module  30 , thereby closing an input circuit in the processor. The closed firing circuit signals the processor that let-off has occurred and that the hammer is about to strike the transfer bar  226 . 
     Referring to FIG. 16, as the trigger  220  is released, or recovered, by the operator, counterclockwise rotation of the trigger moves the trigger post  239  downwardly along the sear  224 . The sear  224  is forced to pivot within the sear pocket of the hammer  222  and against the sear spring until the trigger post  239  is rotated beyond mechanical engagement with the sear  224 . The sear is then pushed outwardly away from the hammer  222  by the sear spring and is therefore prepared to be engaged by the trigger post  239  in a subsequent actuation of the firing mechanism  27 . 
     Forward movement of the connector link  232  allows the rebound  228  to be pushed by the main spring  229  in a forward direction within the frame  16 , thereby moving the hammer stop  243  into engagement with the lower abutment  262  of the hammer  222 . Once the rebound  228  engages the lower abutment  262  of the hammer  222 , the hammer  222  is forced to rotate slightly in the counterclockwise direction, until the trigger reaches the fully-recovered position. Throughout the recovery action, the transfer bar  226  remains engaged within the trigger pocket  240  of the trigger  220  and is pulled downwardly with counterclockwise trigger rotation. 
     Referring to FIGS. 17-19, the sight assembly  42  is configured with front and rear sights, which illuminate according to the level of ambient light surrounding the revolver. In particular, the sight assembly gathers and projects the ambient light toward the photosensitive cell  152  of the backstrap module  30  (seen in FIG. 8) and, in turn, receives and projects toward the firearm operator an amount of high intensity light emitted from the LED  144 . The sight assembly  42  includes a molded plastic sight frame  340 , a single front optical fiber  342 , a pair of rear optical fibers  344  and front and rear ambient light guides  346 ,  347 . 
     The sight frame  340  includes the pair of parallel dovetails  50  introduced in FIG.  2  and front and rear sight housings  348 , 350  formed at opposite ends of an elongated, flexible body portion  352 . The dovetails  50  (only one of the two is shown in FIG. 17) extend rearwardly from the front end of the sight frame  340  and are short enough to be concealed entirely within the shroud  14  when the revolver  10  is assembled. A front fiber channel  354  secures and protects the front fiber  342  and is configured to aim a terminal end  356  of the front optical fiber  342  toward the rear of the revolver  10 . A pair of rear fiber channels  360  secure and protect the rear fibers  344 , and aim terminal ends  364  of the rear optical fiber  344  toward the rear of the revolver  10 . 
     The three channels  354 ,  360  meet and join together at a rearwardly facing interface panel  366  depending from the underside of the rear sight housing  350 . The interface panel  366  defines an aperture  370 , which bundles the optical fibers  342 ,  344  in the channel  354 ,  360  and aims the fibers toward the LED  144  of the backstrap module  30 . 
     The rear sight housing  350  defines a notch  374  between the terminal ends  364  of the rear sight fibers  344  to provide the operator with a line of sight of the front optical fiber  342  when the revolver is held in a normal sighting position. Therefore, if desired during use, the operator can visually align the front fiber  342  between the two rear optical fibers  344 . In other words, the notch  374  prevents the rear sight housing  350  from obstructing the view of the front fiber  342 . 
     The front and rear ambient light gathering guides  346 ,  347  are insert-molded into the rear sight housing  350  of the sight frame  340  to receive ambient light, respectively, from areas generally fore and aft of the revolver  10 . The guides  346 ,  347  curve downwardly and join together at a horizontal interface  382  to project the gathered light collectively upon the photosensor  152  introduced in FIG.  8 . The interface  382  defines an aperture  383 , which is configured to bundle and aim the front and rear ambient light guides  346 ,  347  downwardly at the photosensor  152  in the backstrap module  30 . The horizontal interface  382  is purposely oriented perpendicular to the interface panel  366  so that light emitted from the LED does not inadvertently enter the photosensor  152  and adversely effect operation of the sight assembly. 
     As seen in FIG. 19, the lower housing  48  of the sight frame  340  is formed by the interface panel  366  and opposed side walls  384 , 386 . Each side wall has an laterally-facing key  388  which is received within the receiver  54  of the frame  16  (seen in FIG.  3 ). 
     A metallic cylindrical sleeve  391  is insert molded into the frame  340  to receive the mount screw  58  (seen in FIG. 2) without damaging the material of the sight frame  340 . The interior of the lower housing  48  is filled with a potting material such as silicon rubber after the light fibers are installed. 
     The sight assembly  42  cooperates with electronics within the backstrap module to illuminate the front and rear sights and assist the operator in sighting the revolver under various lighting conditions. The sights are configured so that the light emitted from them can be detected by a firearm operator holding the revolver in a normal sighting position. The brightness with which the sights are illuminated varies automatically depending on the level of ambient light surrounding the revolver  10 . For instance, in certain ambient conditions where the front and rear sights are not easily discerned by the operator, the sights are illuminated brightly to improve contrast between the sights and the surrounding environment. On the other hand, brightly illuminated sights are not required, and may in fact hinder the sighting process, in a dark environment. 
     The sight assembly operates by projecting gathered light upon the photosensor  152  mounted in the backstrap module  30 . The photosensor  152  converts the light to an associated signal, and circuitry within the photosensor circuitboard  146  uses the signal to calculate an appropriate level of illumination for the front and rear sights. The LED is then provided with enough energy to illuminate the front and rear sights. 
     Turning now to a discussion of details of operation of the revolver shown in FIGS. 1-19, the security apparatus is programmed with three operational modes: a sleep mode, an awake mode, and an authorized or “intent-to-fire” mode. There is no “on/off” switch for the revolver, so one of the three operational modes is always active. The least active of the modes is the sleep mode, which deactivates the LCD when the revolver is left alone for more than three (3) minutes. This mode is related to a feature known as a “slow grip,” where the security apparatus automatically reverts to the sleep mode from any other mode to save battery energy when the revolver has not been handled for the predetermined amount of time. The slow grip also deactivates the revolver an prevents unauthorized use in the event that the operator neglects to deactivate the revolver himself or herself. The awake mode is activated by actuating any of the input switches on the hand grip. Hence, the first method in which the input switches can be used is to wake the revolver from the sleep mode. 
     Once the awake mode has been activated, the security apparatus is prepared to receive entry of an authorization code from the operator. Additionally, the awake mode activates the LCD screen, which indicates the various forms of information discussed above. The input switches on the handgrip are used by the operator to enter his or her authorization code by depressing a personalized sequence of switches. However, when the revolver is initially purchased from a dealership or the factory, the operator must enter a manufacturing code set at the factory which corresponds to the serial number of the revolver frame. Once the operator enters the proper manufacturing code, the security apparatus will then accept entry of his or her own personalized authorization code. After the manufacturing code has been changed, the personalized authorization code is the only code needed to operate the revolver. It is apparent that the security apparatus can be programmed with an algorithm, which allows the operator to change the authorization code if desired. 
     The security apparatus uses two mechanisms to inform the operator when the authorization code has been properly entered. A signal is displayed on the LCD, and the front and rear sights are “blinked on”, or illuminated, for a time period of 300 milliseconds. Proper entry of the authorization code activates the “intent-to-fire” mode in the security apparatus and the revolver is capable of being discharged provided the remainder of the input signals are received by the security apparatus. 
     The input switches provide one of the remaining input signals by signaling the security apparatus when the revolver is being gripped by the operator in a manner deemed sufficient and consistent with an intent to fire the revolver. Experiments have shown that the average operator can consistently and simultaneously depress any two of the five input switches. Accordingly, the security apparatus will not authorize a discharge of the revolver unless at least two of the five input switches are depressed. The LCD can include a signal, which informs the operator that the handgrip is being grasped properly. The proper grip is also the mechanism which activates the illuminated sight assembly. As long as the proper grip is maintained, the front and rear sights are illuminated automatically at an intensity level which corresponds to the level of ambient light. 
     In the event that the operator wishes to deactivate the intent-to-fire mode, the input switches can be used to enter a cancellation code, which re-activates the awake mode of the security apparatus. Without the cancellation code, the revolver could be fired, for instance, by an unauthorized individual after being put down by the authorized operator for a time period that is less than that associated with the slow grip feature discussed above. The cancellation code is obviously a function, which can be personalized, but a representative code is three consecutive actuations of the bottom input switch. 
     Once the security apparatus receives a valid authorization code and senses that the revolver is being gripped properly, the security apparatus signals the firing apparatus to provide the firing probe with a low-voltage check signal. Because the probe tip does not contact the cartridge until the firing mechanism has been actuated, the check signal is not conducted further than the probe tip and is not registered by the security apparatus. When the probe tip contacts the cartridge after the firing mechanism has been actuated, the check signal from the firing apparatus is sensed by the security apparatus, thereby informing the security apparatus that a cartridge is positioned properly for discharge. 
     Once the operator is properly authorized, the revolver can be discharged by cycling the firing mechanism, or pulling the trigger beyond the let-off position, provided the security apparatus receives the last two signals: the check signal and the firing mechanism signal. When the hammer falls after cycling the firing mechanism, the hammer strap is contacted by the hammer, thereby signaling the security apparatus that the firing mechanism has been actuated. Almost instantaneously after the hammer strap is contacted, the probe tip is moved into contact with the cartridge, thereby signaling the security apparatus that a cartridge is properly loaded. If so, the security apparatus authorizes the firing apparatus to produce and communicate the 150-volt firing signal to firing probe to discharge the cartridge. 
     The revolver cannot be discharged successively without cycling the firing mechanism beyond the let-off position. First, the security apparatus is programmed with circuitry that can only be reset by releasing the hammer from engagement with the hammer strap. The hammer can only be reset by recovering the trigger after firearm discharge, and cycling the firing mechanism again. 
     Another feature of the revolver which precludes inadvertent discharges results from the configuration of the firing mechanism and transfer bar. After the firearm is discharged, the transfer bar remains at its firing position until the trigger is recovered, thereby pulling the transfer bar out of contact with the actuator bushing. The transfer bar cannot be returned to its firing position against the actuator bushing unless the firing mechanism is cycled to the let-off position. Therefore, even assuming an unfired cartridge is positioned for discharge, a firing signal will not be authorized, much less produced, for instance by dropping the revolver, because the transfer bar is not in the position to move the probe tip into contact with the cartridge. 
     Referring to FIG. 20, a revolver  10 ′ is configured to discharge conventional, percussively primed cartridges, and includes a backstrap module  30 ′ and means  31 ′ adapted to actuate a mechanical firing pin such as that shown and disclosed in U.S. Pat. No. 4,793,085, which is hereby incorporated by reference into the present invention. It is considered within the grasp of a person skilled in the art to adapt the security apparatus of the present invention to supply an electronic signal which is utilized to initiate movement of a solenoid or similar device to convert the electrical signal into mechanical movement which is sufficient to detonate a conventional percussive cartridge primer. 
     While preferred embodiments have been shown and described above, various modifications and substitutions may be made without departing from the spirit and scope of the invention. For example, various other forms of information can be displayed on the LCD display screen for the operator, including an indication of cartridges in any of the cylinder chambers. In addition, different arrangements of electronics within the backstrap module is considered within the scope of the present invention to accommodate various revolver configurations. For instance, smaller revolver sizes may require different component arrangements to avoid effecting operator comfort. Still further, it is considered within the scope of the present invention to replace the mechanically-actuated trigger with other known types of switches for releasing the firing mechanism. 
     Still even further, the backstrap module may assume various other configurations which allow for modifications or improvements to manufacturing procedures, such as forming the backstrap module from front and rear housing halves instead of left and right housing halves. With such a configuration, it may be found more advantageous and economical to assemble and mount the circuitboards to a front housing half and permanently mate the front and rear housing halves once circuitry is secured. 
     It is also considered within the scope of the present invention to provide alternate configurations of the firing probe assembly, which facilitate and economize production and assembly procedures. For instance, the firing probe may include a hollow bore adapted to receive an elongated wire extending from the rear of the probe spring. The elongated wire is inserted through the firing probe and soldered directly to the high-voltage mountboard, thereby obviating the need to solder the firing probe to the mountboard while ensuring proper alignment of the probe, actuator bushing, and probe tip. 
     Still even further, it is considered within the scope of a person skilled in the art of electromechanical design to adapt the security apparatus for use in firing percussively discharged cartridges. Such an integration would involve fitting apparatus to a conventional firing pin which would accept an electronic signal from the security apparatus which is indicative of an intent to fire the revolver. For instance, the security apparatus can provide an appropriate signal to a solenoid of sorts, which solenoid can release the firing pin to impact the cartridge. 
     Yet even further, it is considered within the scope of the present invention to provide a security apparatus which utilizes an alternate method of authorizing an operator, such as with a system which recognizes the voice or biometrics of the operator, a specific sound, or even a certain radio signal. 
     Accordingly, it is to be understood that the present invention has been described by way of illustration and not by way of limitation.