Patent Publication Number: US-7591098-B2

Title: Accessory devices for firearms

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application is a continuation-in-part of U.S. patent application Ser. No. 10/819,535, filed Apr. 6, 2004 now U.S. Pat. No. 7,117,624, incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   This invention relates to accessory devices for being mounted to a firearm, and more particularly to a light beam generator for being mounted to a firearm including a handgun. 
   Accessory devices including light beam generators, such as flashlights and laser aiming devices, have long been adapted for being secured to firearms as target illuminators and laser sights. As particularly relating to handguns, such accessory devices may utilize a longitudinal rail carried by the frame of the handgun and forwardly of the trigger guard, which rail may be integral with the frame as disclosed in U.S. Pat. No. 6,276,088, or such rail may be provided as a separate structure removably attachable to the handgun as disclosed in U.S. Pat. No. 6,378,237, both patents issued to John W. Matthews and Paul Y. Kim and assigned to the assignee of the present invention, which patents are incorporated herein by reference. 
   Handgun manufacturers have introduced various handgun models having a longitudinal rail along the handgun&#39;s frame, below the barrel and forwardly of the trigger guard, such rail being configured with two longitudinal grooves, one along each side of the rail, and further configured with a transverse slot in the bottom surface of the rail. As is well known, such rails are intended for cooperating with accessories such as a light beam generator having a housing configured with a pair of longitudinal tongues complementing the longitudinal grooves for slidably retaining the light beam generator on the rail. A latch on the light beam generator housing co-acts with the transverse slot in the rail for releasably preventing further longitudinal movement of the light beam generator along the rail when the light beam generator is at a predetermined longitudinal position. 
   The longitudinal rails of handguns of some manufacturers may be of different configuration than the longitudinal rails of handguns of other manufacturers. For example, some handguns include a longitudinal rail commonly known as a Universal rail, while other handguns include a rail commonly known as a Picatinny rail. The slot width of the Universal rail is substantially less than the slot width of the Picatinny rail. Until the present inventions, an accessory device securable to one type of rail was not securable to another type of rail. 
   SUMMARY OF THE INVENTION 
   The present invention provides an accessory device that is adapted to accommodate handguns and other firearms carrying longitudinal rails of different configurations. For example, the accessory device of the present invention may be secured to a longitudinal rail carried by a firearm having a slot width different than the slot width of another longitudinal rail carried by a firearm. In a particular example, the accessory device of the present invention accommodates a Universal rail as well as a Picatinny rail. 
   A preferred embodiment of the accessory device of the present invention comprises a light beam generator, such as a target illuminator or a laser sight, that includes a removably attachable switch device for being replaced by or interchanged with another switch device having a different or modified switch configuration. 
   The aforementioned parent application Ser. No. 10/819,535 discloses, according to one aspect of that invention, an accessory device for a firearm including a frame, a longitudinal barrel, a longitudinal rail carried by the frame, and a depression in the rail, the accessory device comprising: a housing; elongate members removably secured to the housing, the elongate members complementing the rail for enabling the housing to be retainably slid along the rail; and a plate pivotally secured to the housing about a transverse axis and having a free end biased away from the housing, the plate including a protuberance in the vicinity of the free end, the protuberance receivable by the depression for stopping sliding of the housing along the rail. The plate is captured to the housing by the elongate members secured to the housing, and the plate is removable from its securement about the transverse axis when the elongate members are removed from the housing. 
   The plate preferably includes transversely extending arms through the housing, which arms are captured to the housing by the elongate members when secured to the housing, and the arms are adapted to be urged by an operator for pivoting the plate about the transverse axis toward the housing. 
   In a preferred embodiment disclosed in the parent application, as well as in the present application, the accessory device is a light beam generator. The light beam generator of the parent application preferably comprises: a housing; elongate members removably secured to the housing, the elongate members complementing the rail for enabling the housing to be retainably slid along the rail; a plate pivotally secured to the housing about a transverse axis and having a free end biased away from the housing, the plate including a protuberance in the vicinity of the free end, the plate receivable by the depression for stopping sliding of the housing along the rail; a light emitter assembly carried by the housing; a battery carried by the housing in circuit for energizing the light emitter assembly when switch actuated; and a switch device including a switch actuator for the battery. The switch device preferably comprises a tail cap switch pivotally secured to the housing about a pivot axis, the tail cap switch preferably removable from its pivotal securement. The switch actuator is preferably operable by either hand of an operator when the housing is installed on the rail for placing the switch device in a CONSTANT ON or OFF position, and operable by either hand of the operator when the housing is installed on the rail for placing the switch device in a MOMENTARY ON position. A remote switch actuator may be provided for communicating with the switch device for remotely actuating the switch device to a MOMENTARY ON position. 
   According to a further aspect of the invention disclosed in the parent application, a method is provided of assembling an accessory device for installation on a first rail having a depression and carried by a firearm, comprising: providing the accessory device including a housing; providing elongate members complementing the rail; providing a plate having a protuberance in the vicinity of an end thereof, the protuberance sized for being received by the depression; pivotally securing the plate to the housing with such end biased away from the housing; and removably securing the elongate members to the housing with the elongate members capturing the plate to the housing and enabling the housing to be retainably slid along the rail. The method may further include: removing the elongate members from the housing; removing the plate from the housing; providing a second plate having a protuberance in the vicinity of an end thereof, the protuberance of the second plate sized for being received by a depression in a second rail carried by a firearm, the protuberance of the second plate being of a different size than the protuberance in the first plate; pivotally securing the second plate to the housing with such second plate end biased away from the housing; and removably securing the elongate members to the housing with the elongate members capturing the second plate to the housing and enabling the housing to be retainably slid along the second rail. 
   According to yet another aspect of that invention, there is provided a method of adapting an accessory device normally installable on a first rail carried by a firearm and having a depression, for installation on a second rail carried by a firearm and having a depression of a different size than the depression of the first rail, comprising: providing the accessory device including a housing, a first plate having a protuberance in the vicinity of an end thereof, the protuberance of the first plate sized for being received by the depression in the first rail, the plate being removably pivotally secured to the housing along a transverse axis with such end thereof biased away from the housing, and elongate members complementing the first rail and removably secured to the housing and capturing the plate to the housing, the elongate members enabling the housing to be retainably slid along the first or second rails; removing the elongate members from the housing; removing the first plate from the housing; providing a second plate having a protuberance in the vicinity of an end thereof sized for being received by the depression in the second rail; removably pivotally securing the second plate to the housing along a transverse axis with such end of the second plate biased away from the housing; and removably securing elongate members complementing the second rail to the housing and capturing the second plate to the housing and enabling the housing to be retainably slid along the second rail. In the elongate members securing step, the elongate members being secured may be the same elongate members removed in the elongate members removing step. 
   According to one aspect of the invention of the present application, there is provided an accessory device for a firearm carrying a longitudinal rail including a transverse slot, the accessory device comprising: a housing; elongate members secured to the housing and complementing the rail for enabling the housing to be retainably slid along the rail; a generally U-shaped plate including two resilient legs longitudinally extending from a base pivotally (and preferably removably) secured to the housing about a transverse axis, each of the legs having a free end and an upstanding protuberance in the vicinity of the free end, the legs transversely urgable for resiliently displacing the legs&#39; free ends toward one another; and the housing adapted for releasably retaining the free ends in a first vertical position with the upstanding protuberances non-receivable in the slot when the housing is applied to the rail with the free ends resiliently displaced toward one another and the plate downwardly pivoted, the housing adapted for supporting the free ends in a second vertical position with the upstanding protuberances receivable in the slot. The plate preferably includes two arms transversely extending from the legs respectively, the arms urgable by a user for resiliently displacing the free ends toward each other and for pivoting the plate. 
   In a preferred embodiment of the generally U-shaped plate, each of the legs includes a forward protuberance at its free end; the housing includes two spaced-apart supports engageable with the forward protuberances for supporting the undisplaced free ends in the second vertical position; and the housing includes two depressions adjacent to the supports for respectively receiving the forward protuberances with the free ends in the first vertical position when the legs are transversely urged and the plate is downwardly pivoted. 
   The depressions of the preferred housing embodiment are configured for releasably retaining the forward protuberances resiliently biased by the legs. For example, each of the depressions may include a wall for being laterally engaged by the forward protuberances resiliently biased by the legs with the free ends transversely displaced toward one another. 
   According to another aspect of the present invention, there is provided a method of assembling an accessory device for installation on a longitudinal rail carried by a firearm, the rail including a transverse slot therein, the method comprising: providing the accessory device including a housing; providing elongate members complementing the rail; providing a latch plate including at least one upstanding protuberance sized for being received by the slot in the rail; pivotally securing the plate to the housing with the at least upstanding protuberance in the vicinity of at least one free end of the plate; and removably securing the elongate members to the housing with the elongate members capturing the plate to the housing and enabling the housing to be retainable slid along the rail. In the pivotally securing step, the plate is preferably removably secured to the housing about a transverse axis. 
   In a preferred manner of practicing the method, the provided plate is generally U-shaped having two resilient legs longitudinally extending from a base, each of the legs having a free end with an upstanding protuberance in the vicinity of the free end; the provided housing is adapted for releasably retaining the free ends of the legs in a first vertical position, and for supporting the free ends of the legs in a second vertical position; and during the pivotally securing step, the base of the plate is removably pivotally secured to the housing about a transverse axis. 
   According to yet another aspect of the present invention, there is provided a method of installing an accessory device to a longitudinal rail including a transverse slot therein, the method comprising: providing an accessory device slidable along the rail and including a housing, a generally U-shaped plate having two resilient legs longitudinally extending from a base pivotally secured to the housing about a transverse axis, each of the legs having a free end and an upstanding protuberance in the vicinity of the free end, the housing adapted for releasably retaining the free ends in a first vertical position with the upstanding protuberances non-receivable in the slot, the housing adapted for supporting the free ends in a second vertical position with the upstanding protuberances receivable in the slot; transversely urging the legs to displace the free ends toward one another while downwardly pivoting the plate to place the free ends in the first vertical position in the housing; sliding the accessory device along the rail until the upstanding protuberances are positioned beneath the slot; and upwardly pivoting the plate to release the free ends from the first vertical position and to be supported by the housing in the second vertical position with the upstanding protuberances received in the slot. For removing the accessory device from the rail, the method continues by transversely urging the legs to displace the free ends toward one another while downwardly pivoting the plate to place the free ends in the first vertical position with the upstanding protuberances removed from the slot; and sliding the accessory device along the rail until removed therefrom. 
   The present invention further provides a method of adapting an accessory device normally installable on a first longitudinal rail including a transverse slot, for installation on a second longitudinal rail including a transverse slot of a different size than the slot in the first rail, the method comprising: providing an accessory device including a housing, a generally U-shaped first plate having two resilient legs longitudinally extending from a base removably pivotally secured to the housing about a transverse axis, each of the legs having a free end and an upstanding protuberance in the vicinity of the free end, the upstanding protuberances of the first plate sized for being received by the slot in the first rail, and elongate members complementing the first rail and removably secured to the housing and capturing the plate to the housing, the elongate members enabling the housing to be retainably slid along the first rail; removing the elongate members from the housing; removing the first plate from the housing; providing a generally U-shaped second plate having two resilient legs longitudinally extending from a base removably pivotally securable to the housing about a transverse axis, each of the legs having a free end and an upstanding protuberance in the vicinity of the free end, the upstanding protuberances of the second plate sized for being received by the slot in the second rail; removably pivotally securing the second plate to the housing; and removably securing elongate members complementing the second rail to the housing and capturing the second plate to the housing and enabling the housing to be retainably slid along the second rail. In the elongate members securing step, the elongate members being secured may be (but need not be) the same elongate members removed in the elongate members removing step. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features believed to be characteristic of the inventions, together with further advantages thereof, will be better understood from the following description considered in connection with the accompanying drawings in which preferred embodiments of the inventions are illustrated by way of example. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention. 
       FIG. 1  is a side elevation view of a firearm having a longitudinal rail structure to which may be removably secured an accessory device according to both the present invention and the invention disclosed in the aforementioned parent application Ser. No. 10/819,535; 
       FIG. 2  is a side elevation view of a preferred embodiment of an accessory device according to the parent application, specifically a preferred embodiment of a light beam generator, removably secured to the rail structure of the firearm of  FIG. 1  (in increased scale); 
       FIG. 3  is a front elevation view of the firearm and secured light beam generator of  FIG. 2 ; 
       FIG. 4  is an exploded side/rear perspective view of the light beam generator of  FIGS. 2 and 3 , illustrated during assembly of various components thereof; 
       FIG. 5  is a longitudinal cross-sectional view of the assembled light beam generator of  FIG. 4  (in further increased scale), taken along a vertical plane along the light beam generator&#39;s longitudinal axis a′ (the line  5 - 5  of  FIG. 4 ) and viewed in the direction of the appended arrows; 
       FIG. 6  is a top plan view of a preferred embodiment of a replaceable lever latch plate (in same scale as in  FIG. 5 ) included in the preferred embodiment of the accessory device or light beam generator of  FIGS. 2-5 ; 
       FIG. 7  is a bottom plan view of the lever latch plate of  FIG. 6 ; 
       FIG. 8  is a side elevation view of the lever latch plate of  FIG. 6 ; 
       FIG. 9  is a fragmentary, part cross-sectional elevation view of an example of a rail interface member secured to the accessory device housing according to the preferred embodiment; 
       FIG. 10  is a cross-sectional view of the preferred embodiment of a replaceable tail cap switch assembly shown in  FIG. 4 , taken along a transverse plane along the longitudinal axis a′ (the line  10 - 10  of  FIG. 4 ) and viewed in the direction of the appended arrows; 
       FIG. 11  is a front elevation view of the tail cap switch assembly, which view includes the front surface of the switch circuit board with battery rear terminal contacts; 
       FIG. 12  is a rear view of the tail cap switch assembly circuit board of  FIG. 11 ; 
       FIG. 13  is a side elevation view of the tail cap switch assembly circuit board of  FIGS. 11 and 12 ; 
       FIG. 14  is a rear elevation view of the tail cap broken away to show structure of a preferred switch actuator mechanism; 
       FIG. 15  is a front elevation view of a tail cap insert included in the tail cap switch actuator mechanism; 
       FIG. 16  is a rear elevation view of an actuator arm included in the tail cap switch actuator mechanism; 
       FIG. 17  is a left side view of the actuator arm of  FIG. 16 ; 
       FIG. 18  is a cross-sectional view of a replaceable tail cap switch assembly similar to the tail cap switch assembly shown in  FIG. 5  but further including a pressure tape switch; 
       FIG. 19  is a rear view of the switch assembly circuit board of  FIG. 18 ; 
       FIG. 20  is a top plan view of a second preferred embodiment of a replaceable lever latch plate included in the preferred embodiment of the accessory device or light beam generator of  FIGS. 2-5 ; 
       FIG. 21  is a perspective view of a firearm to which is attached a conventional accessory rail mount structure to which is mounted the preferred embodiment of the accessory device or light beam generator of the invention disclosed in the parent application or of the present invention; 
       FIG. 22  is a side elevation view of a fragment of the front portion of the accessory rail mount exemplified in  FIG. 21 ; 
       FIG. 23  is a front elevation view of the accessory rail mount of  FIG. 22  to which is mounted a light beam generator according to the invention disclosed in the parent application; 
       FIG. 24  is side elevation view of a preferred embodiment of an accessory device according to the present invention, specifically a preferred embodiment of a light beam generator, removably secured to the rail structure of the firearm in  FIG. 1  (in increased scale); 
       FIG. 25  is a front elevation view of the firearm and secured light beam generator of  FIG. 24 ; 
       FIG. 26  is a front elevation view of the accessory rail mount of  FIG. 22  to which is mounted the light beam generator of  FIG. 24 ; 
       FIG. 27  is an exploded side/rear perspective view of the light beam generator of  FIGS. 24-26 , illustrated during assembly of various components thereof; 
       FIG. 28  is a longitudinal cross-sectional view of the assembled light beam generator of  FIG. 27 , taken along a vertical plane along the light beam generator&#39;s longitudinal axis a″ (the line  28 - 28 ) of  FIG. 27  and viewed in the direction of the appended arrows; 
       FIG. 29  is a top plan view of a preferred embodiment of a latch plate (in the same scale as  FIG. 28 ) included in the preferred embodiment of the accessory device or light beam generator of  FIGS. 27 and 28 ; 
       FIG. 30  is a bottom plan view of the latch plate of  FIG. 29 ; 
       FIG. 31  is a cross-sectional view of the latch plate of  FIG. 29 , taken along the line  31 - 31  and viewed in the direction of the appended arrows; 
       FIG. 32  is a front elevation view of the latch plate of  FIG. 29 ; 
       FIG. 33  is a top plan view of the battery housing of the light beam generator shown in  FIGS. 27 and 28 ; 
       FIG. 34  is a cross-sectional view of the housing of  FIG. 33  taken along the line  34 - 34  and viewed in the direction of the appended arrows; 
       FIG. 35  is a top view of the latch plate of  FIGS. 29-32  installed to the battery housing of  FIGS. 33 and 34  (shown with the elongate rail interface members removed for clarity of description), with the latch shown in its latching position; 
       FIG. 36  is a fragmentary cross-sectional view of the latch plate/housing combination of  FIG. 35 , taken along the line  36 - 36  and viewed in the direction of the appended arrows; 
       FIG. 37  is the same view as in  FIG. 35 , with the latch plate shown in its unlatching position; 
       FIG. 38  is a fragmentary cross-sectional view of the latch plate/housing shown in  FIG. 37 , taken along the line  38 - 38  and viewed in the direction of the appended arrows; and 
       FIG. 39  is a top plan view of a second preferred embodiment of a latch plate included in the preferred embodiment of the accessory device or light beam generator of  FIGS. 27 and 28 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Turning first to  FIG. 1 , there is illustrated an example of a firearm  20 , specifically a handgun including a barrel  22  extending along a longitudinal axis a from the handgun&#39;s frame  24 . The handgun  20  includes a trigger guard  26  in front of the handgun&#39;s trigger  28 . 
   As used herein, “longitudinal” describes a direction along or parallel to the longitudinal axis a of the firearm&#39;s barrel, or along or parallel to the longitudinal axis a′ of the light beam generator  36  (see  FIGS. 2 ,  4  and  5 ), or along or parallel to the longitudinal axis a″ of the light beam generator  236  (see  FIGS. 24 ,  27  and  28 ), or along or parallel to the longitudinal axis b of the latch plate  316  (see  FIG. 29 ), or along or parallel to the longitudinal axis b′ of the battery housing  240  (see  FIG. 33 ), which axes a′, a″, b and b′ are parallel to the axis a when the light beam generator  36  or  236  is installed on the firearm; “transverse” describes a horizontal direction perpendicular to the axis a (or axis a′, a″, b or b′) when the barrel  22  (or light beam generator  36  or  236 ) is horizontally positioned; “above” means vertically above and “upward” means vertically upward when the firearm barrel  22  (or light beam generator  36  or  236 ) is horizontally positioned; “below” or “beneath” means vertically below and “downward” means vertically downward when the firearm barrel  22  (or light beam generator  36  or  236 ) is horizontally positioned; “front” or “forward” describes the longitudinal direction toward the muzzle of the barrel  22  or the light emitter assembly  46  (i.e., to the right as shown in  FIGS. 1 ,  2 ,  4 ,  24 ,  27 ,  29 - 31 ,  33  and  35 - 39 , and to the left as shown in  FIGS. 5 and 28 ); and “rear” or “rearward” describes the longitudinal direction opposite the front or forward direction (i.e., to the left as shown in  FIGS. 1 ,  2 ,  4 ,  24 ,  27 ,  29 - 31 ,  33  and  35 - 39 , and to the right as shown in  FIGS. 5 and 28 ). 
   The handgun  20  includes a longitudinal rail  30  along the frame  24 , below the barrel  22  and forwardly of the trigger guard  26 . Such rails are well known in the handgun art, for mounting accessories thereto such as a light beam generator. The rail  30  is configured with two longitudinal grooves  32 , one along each side of the rail  30 , and is further configured with a transverse slot  34  in the bottom surface  35  of the rail  30 . As is well known, such rails are intended for cooperating with accessories such as a light beam generator having a housing configured with a pair of longitudinal tongues (in this respect, see the tongues  38  and  238  of the preferred light beam generators  36  and  236 , respectively, of the present inventions as represented in  FIGS. 3 and 25 ), with such tongues  38  or  238  complementing the longitudinal grooves  32  for slidably retaining such light beam generator on the rail  30 . A latch on the light beam generator housing co-acts with the transverse slot  34  in the rail  30  for releasably preventing further longitudinal movement of the light beam generator along the rail  30  when the light beam generator  36  or  236  is at a predetermined position along the rail  30 . 
   Although the rail  30  is represented in  FIG. 1  as being integral with the frame  24  of the handgun  20 , the rail  30  may also be provided as a separate structure that may be removably attached to the handgun beneath the barrel and forwardly of the trigger guard. As previously noted, such rails for handguns, both integral to the frame and removably attachable to the handgun, as well as light beam generators adapted for being removably attached to such rails as discussed above, are disclosed in the aforementioned U.S. Pat. Nos. 6,276,088 and 6,378,237 incorporated herein by reference. 
   Handgun manufacturers have introduced various handgun models with integral rails having longitudinal grooves of the type shown in  FIGS. 1-3 . Although such longitudinal grooves among manufacturers have been of substantially similar dimensions, the transverse slots in the rails of handguns of some manufacturers are of different width than the transverse slot in the rails of handguns of other manufacturers. Specifically, the rails of some handguns include a transverse slot of one predetermined width while the rails of other handguns include a transverse slot of another predetermined width. For example, some handguns include a rail commonly known as a Universal rail, while other handguns include a rail commonly known as a Picatinny rail; the slot width of the Universal rail is substantially less than the slot width of the Picatinny rail. The accessory device or light beam generator  36  or  236  of the present invention accommodates both types of rails. 
   The light beam generator  36  or  236  further includes a removably attachable switch device, for being replaced by or interchanged with another switch device having a different or modified switch configuration. 
   Turning also to  FIGS. 4-8 , the light beam generator  36  includes a housing  40  in which is contained a power source such as a battery  42  of one or more battery cells  44  (for example, two 3-volt lithium battery cells  44 ). A light emitter assembly  46  is carried by the housing  40  forwardly of the battery  42  and in circuit with a positive front terminal of one of the battery cells  44  and a negative front terminal of another of the battery cells  44 . A switch device  48  preferably situated at the rear of the housing  40  in and including a tail cap  50 , includes a switch actuator assembly  49  for selectively completing and opening the light emitter energization circuit. In the embodiment shown, this is accomplished by the switch actuator assembly  49  establishing a conductive path between the rear positive terminal  43  of one of the battery cells  44  and the rear negative terminal  45  of the other of the battery cells  44  for placing the switch device  48  in an ON position for causing the battery  42  to energize the light emitter assembly  46 , and by opening such conductive path for placing the switch in an OFF position where the battery  42  does not energize the light emitter assembly  46 . 
   As shown in  FIG. 5 , a preferred light emitter assembly  46  may include a light emitter  52  such as a light emitting diode (LED), preferably a high luminous flux LED such as a 3-watt or 5-watt LED manufactured by Lumileds Lighting, LLC (of San Jose, Calif.) and marketed under the trademark LUXEON including such LEDs marketed under the LUXEON STAR trademark. 
   With such an LED as the light emitter  52 , the emitted light may be directed by a lens system contained in the light emitter assembly  46  including a totally internal reflective (TIR) lens  54  (as represented in  FIG. 5 ), or by a parabolic reflector system as disclosed in U.S. patent application Ser. No. 10/346,537 of Paul Y. Kim and William A. Hunt, assigned to the assignee of the present invention, which patent application is incorporated herein by reference. The light emitter assembly  46  may alternatively include an incandescent lamp as the light emitter  52 , such as a high intensity tungsten light bulb, with the emitted light preferably directed by a parabolic reflector. 
   In either case, the light emitter assembly  46  may further include a controller  56  for regulating the power to the light emitter for providing light output of constant brightness with decreasing battery voltage over time. The use of such controllers is discussed in the aforesaid patent application Ser. No. 10/346,537 incorporated herein by reference. 
   The preferred embodiment of the housing  40  of the light beam generator  36  includes a substantially flat upwardly facing surface  58  with two upstanding first wall segments  60  longitudinally extending forwardly along opposite sides of the surface  58  from the vicinity of the housing&#39;s rear end  62 , and two upstanding second wall segments  64  forwardly of the respective first wall segments  60 . The forward generally vertical ends  66  of the respective first wall segments are transversely aligned, and the rear generally vertical ends  68  of the respective second wall segments  64  are transversely aligned and spaced from the second wall segments&#39; forward ends  68  by a predetermined distance d. 
   A transversely disposed pin  70  is secured to the housing  40  in the vicinity of its rear end  62  and above the housing&#39;s flat surface  58 . As shown in  FIG. 4 , the transverse pin  70  is secured to the first wall segments  60  in the vicinity of their rear ends and above the flat surface  58 . The pin  70  additionally extends through apertures in two upstanding protuberances or partitions  72  from the flat surface  58 . The two partitions  72  are laterally spaced so as to divide the transverse pin into three exposed segments  74 ,  76 ,  78  which may be of substantially equal lengths. 
   The light beam generator  36  includes a latch lever plate  80  having a generally U-shaped rear end  82  configured for receiving the middle segment  76  of the transverse pin  70 . One leg (preferably the upper leg  83 ) of the U may curve over a portion of the generally rearwardly facing opening of the U, and the plate  80  is preferably made of a material such that the legs are somewhat resilient. As illustrated in  FIG. 4 , the latch plate  80  is installed to the housing  36  by placing the opening of the latch plate&#39;s rear end  82  to the transverse pin segment  76 , and the installer urging the rear end  82  to snap onto the pin segment  76 . The latch plate  80  accordingly is hinged at its rear end  82  about the transverse hinge pin  70 , specifically about the hinge pin segment  76 ; i.e., the plate  80  is pivotally secured to the housing  40  about a transverse axis t along the pin  70 . 
   The top surface of the plate  80  includes an upstanding protuberance, preferably a transversely disposed elongate protuberance  84 , in the vicinity of the plate&#39;s front end  86 , the elongate projection  84  having a width w (along the longitudinal direction) slightly less than the slot  34  of the firearm&#39;s rail  30  for being received therein. Lateral arms  88  transversely extend outwardly from opposite sides of the plate  80 , the arms  88  situated in the vicinity of the plate&#39;s front end  86  and being of a width d′ (along the longitudinal direction) slightly less the distance d between the forward ends  66  of the first wall segments  60  and the respective rear ends  68  of the second wall segments  64  (see  FIG. 4 ) such that the arms  88  are received between such ends  66  and  68 . The vertical height of the end portions  66  and  68  is preferably greater than the sum of the vertical thickness of the plate  80  and the vertical height of the protuberance  84 . 
   During installation of the plate  80  to the housing  40 , after being hinged to the hinge pin segment  76  the plate  80  is pivoted toward the housing&#39;s upwardly facing surface  58  (i.e., in the clockwise direction as viewed in  FIG. 4 ) with a wave spring  90  held by an annular groove  92  in the underside of the plate  80  (see also  FIGS. 5 and 7 ) in the longitudinal vicinity of the protuberance  84  and the lateral arms  88 , until the spring  90  contacts the flat upwardly facing surface  58  of the housing  40  while the lateral arms  88  of the plate  80  are caused to enter the space between the wall surfaces  66  and  68 . 
   The accessory device or light beam generator  36  includes two elongate members  94  removably secured to the housing  40 , for interfacing with the firearm rail  30  to enable the housing  40  to be retainably slid along the rail  30  (see, in particular,  FIGS. 1-5 ). Each elongate member  94  includes an inwardly directed tongue  38  longitudinally extending along such member  94 ; i.e., such elongate rail interface members  94  are installed to the housing  40  with the longitudinal tongue  38  of one of the members  94  facing the longitudinal tongue  38  of the other of the members  94 , the tongues  38  complementing the firearm&#39;s longitudinal grooves  32  for slidably cooperating with the firearm&#39;s longitudinal grooves  32  while being vertically retained by the rail  30  as shown in  FIGS. 2 and 3 . 
   The elongate rail interface members  94  are installed to the housing  40  after the latch plate  80  has been hinged to the hinge pin segment  76  and pivoted with its lateral arms  88  in the space between the upstanding wall segment ends  66  and  68  as discussed above. Each member  94  includes a flat bottom surface  96  for contacting the top surfaces  98  and  100  of the housing&#39;s respective wall segments  60  and  64 . The members  94  include bores  102  therethrough aligned with internally threaded blind vertical bores  104  in the top surfaces  98 ,  100  of the housing&#39;s wall segments  60 ,  64 , preferably forwardly of the wall segment ends  68  and rearwardly of the wall segment ends  66 , the members  94  being removably secured to the wall segments  60 ,  64  by headed screws  106  respectively extending into the bores  102  through the member  94  and threaded into the respectively aligned threaded bores  104  in the housing  40 . With the elongate members  94  so installed, their bottom surfaces  96 —which contact and extend along the top surfaces  98 ,  100  of the wall segments  60 ,  64 —bridge the wall segments  60 ,  64  and provide a ceiling to the space between the wall ends  66 ,  68 . Such bridge or ceiling upwardly captures the lateral arms  88  within such space, while the wall ends  66 ,  68  longitudinally captures the lateral arms  88  within such space, resulting in the hinged latch plate  80  being captured to the housing  40  as well. 
   The elongate rail interface members  94  may be removed from the housing  40  by unscrewing the screws  106 , and if desired the elongate rail interface members  94  may be replaced by other or different elongate rail interface members which are similarly removably securable to the housing  40 . It may be appreciated that when the rail interface members  94  have been removed from the housing  40 , the lateral arms  88  of the hinged latch plate  80  are no longer upwardly blocked or captured by the members  94 , so that the latch plate  80  may be pivoted about the hinge pin  70  away from the surface  58  of the housing  40  and pulled away from the hinge pin segment  76 . In such manner, the latch plate  80  may be removed from the housing  40  and another or different latch plate  80 , which is similarly removably securable to the housing  40 , may be hinged to the hinge pin  70  and upwardly captured by reinstalling the rail interface members  94 . 
   Another feature of the preferred embodiment of the light beam generator  36  of the present invention comprises the tail cap switch device  48  which functions both as a battery cover permitting the battery cells  44  to be installed and retained in the housing  40  and as a switch for actuating the battery  42  to selectively energize the light emitter of the light emitter assembly  46 . The preferred embodiment of the tail cap switch  48  is removably securable to the rear end  62  of the housing  40 . 
   The switch device  48  includes a tail cap  50  which is hinged to the transverse hinge pin  70  by two transversely spaced-apart forward projections  108  each having a generally U-shaped end portion, one leg of the U preferably curving over a portion of the generally upwardly and rearwardly facing opening of the U. The projections  108  are preferably somewhat resilient and, as illustrated in  FIG. 4 , the switch device  48  is installed to the housing  36  by placing the openings of the cap&#39;s projections  108  to the transverse pin outer segments  74  and  78 , the installer urging the projections  108  to snap onto the pin segments  74 ,  78 . The tail cap  50  accordingly is hinged about the transverse hinge pin  70 , specifically about the hinge pin segments  74 ,  78 ; i.e., the tail cap switch is pivotally secured to the housing  40  about a pivot axis, preferably the transverse axis t. 
   The installer thereupon rotates the tail cap  50  toward the housing&#39;s open rear end  62  (i.e., counterclockwise as viewed in  FIG. 4 ) until the rear opening of the housing  40  is closed and the tail cap  50  is locked into place by cooperation of a catch  110  along the lower edge of the tail cap  50  with a spring-biased latch  112  on the housing  40  ( FIGS. 4 and 5 ). When the tail cap  50  is in its latched position, the forwardly facing battery contacts  114 ,  116  on the switch device circuit board  118  are in conductive contact with the respective rear battery terminals  43 ,  45 . 
   The switch device  48  may be removed from the housing  40  by manually unlatching the latch  112 , pivoting the tail cap  50  upwardly about the hinge pin  70  away from the housing&#39;s rear opening (for example, to the position generally illustrated in  FIG. 4 ) and pulling the switch device  48  away from the hinge pin segments  74  and  78 . In such manner, the switch device  48  may be removed from the housing  40  and another or different switch device, which is similarly removably securable to the housing  40 , may be hinged to the hinge pin  70  and locked to the rear end  62  of the housing  40  by operation of the latch  112 . 
   When the light beam generator  36  is in its assembled condition (i.e., with the tail cap switch  48 , latch plate  80  and rail interface members  94  installed to the housing  40  as described above), the assembled light beam generator  36  may be removably installed to the firearm  20 . The light beam generator  36  is placed to the firearm  20  with the rear ends of the tongues  38  of the rail interface members  94  respectively engaging the forward ends of the grooves  32  of the rail  30  carried by the firearm  20 . The light beam generator  36  is thereupon rearwardly urged, thereby sliding the housing  40  along the rail  30  while the housing  40  is being vertically retained by the rail  30 . When the transverse upstanding protuberance  84  of the latch plate  80  contacts the bottom surface of the rail  30  (which may be facilitated by a swept-back profile of the forward portion of the rail  30  illustrated in  FIGS. 1 and 2 , preferably of a height at least as great as the height of the protuberance  84 ), the latch plate is thereby urged to pivot about the hinge pin  70  against the bias of the spring  90 , until the transverse protuberance  84  enters the transverse slot  34  as the spring  90  urges the plate  80  to pivot about the hinge pin segment  76 . 
   As earlier noted, the width w of the protuberance  84  is slightly less than the width of the slot  34  such that the protuberance  84  just fits into the slot  34 . The engagement of the protuberance  84  with the slot  34  stops further longitudinal movement of the housing  40  along the rail  30 , longitudinally latching the housing  40  in this position. The longitudinal positions of the slot  34  and of the protuberance  84  are preferably predetermined such that the rear end of the tail cap  50  is situated just forwardly of the handgun&#39;s trigger guard  26  when the protuberance  84  engages the slot  34 . 
   Because the dimensional tolerances of rails  30  may differ among firearm manufacturers, and even among firearms manufactured by the same manufacturer, the rail interface members  94  may be configured to accommodate such differences. In a preferred embodiment of the rail interface members  94  for accommodating such differences, the bores  102  and the counterbores  103  in the rail interface members  94  may be slightly greater in at least the transverse direction than the respective diameters of the threaded shaft  107  and head  109  of the screws  106 , for providing a loose fit in at least the transverse direction between the screws  106  and the bore  102 /counterbore  103  combinations. For example, the diameters of the screw-head  109  and threaded shaft  107  may be slightly greater than the diameters of the counterbore  103  and bore  102 , respectively. 
   During installation of the light beam generator  36  to a particular firearm rail  30 , if the engagement of rail interface members  94  to the rail  30  is too loose, the installer may simply loosen the screws  106 , move the rail interface members  94  inwardly (transversely toward each other) and thereupon tighten the screws  106  with the screw-heads  109  urged against the peripheral floor annular ledge  105  of the counterbores  103 . If the engagement between the rail interface members  94  and the rail  30  is too tight, the installer may loosen the screws  106 , move the rail interface members  94  outwardly (transversely away from each other), and tighten the screws  106  with the bottom surface  111  of the screw-heads  109  urged against the peripheral floor or annular ledge  105  of the counterbores  103 . 
   To remove the accessory device  36  from the firearm  20 , the operator downwardly urges the laterally protruding handles  120  on the ends of the lateral arms  88 , causing the plate  80  to pivot about the hinge pin  70 , against the bias of the spring  90 , until the protuberance  84  is disengaged from the transverse slot  34 . The operator thereupon forwardly urges the accessory device  36  to slide along the rail  30  until the accessory device  36  is removed therefrom. 
   A preferred embodiment of the tail cap switch device  48  of the present invention permits ambidextrous actuation of the switch device  48  for energizing the light emitter  52  in a CONSTANT ON/OFF mode as well as in a MOMENTARY ON mode. The switch mechanism for implementing such operation is shown in  FIGS. 10-17 . 
   A switch actuator arm  122  (e.g. fabricated of stainless steel) is affixed to an actuator disk  124  (e.g. fabricated of a polymeric material) rotatable about a circular protuberance  125  along the longitudinal axis a′. The actuator disk  124  is also rotatable about an elastomeric washer  127  (e.g. fabricated of rubber) rearwardly projecting from the tail cap insert  130  and having a rearwardly facing annular rim  128  adjacent to the forward surface of the actuator disk  124 . 
   The actuator disk  124  is rotatable with the actuator arm  122  about the longitudinal axis a′. The disk  124  includes peripheral notches  126  engaged by ends of a latching spring  129  secured to the tail cap insert  130 , for latching the disk  124  and hence the actuator arm  122  in a first rotational position where the arm  122  is transversely oriented ( FIG. 14 ), a second rotational position where the arm  122  is rotated clockwise by a predetermined angle (say, approximately 20°), and a third rotational position where the arm  122  is rotated counterclockwise by a predetermined angle (say, approximately 20°). An operator may selectively rotate the arm into these three alternative latched positions by manipulating up or down either one of the handles  132  attached to the ends of the actuator arm  122 . 
   The tail cap insert  130  includes a plate  134  (preferably of a plastic material such as polypropylene), having two rearwardly projecting nubs  136  at the free ends of flexible fingers  138  formed by cuts  140  through the insert plate  134 . The end portions  142  of the actuator arm  122  are situated just to the rear of the rearwardly projecting nubs  136 . Angularly extending from each of the actuator arm end portions  142  is a forwardly stepped tab  144 . The end portions  142  of the actuator arm  122  are normally situated longitudinally just to the rear of the rearwardly projecting nubs  136  when the actuator arm  122  is in its latched first or transverse position. However, when the actuator arm  122  is in either of its latched second or third rotated positions, one of the forwardly stepped tabs  144  contacts one of the nubs  136  and urges such contacted nub  136  to be forwardly displaced. When the operator rotatably replaces the actuator arm  122  to its latched first or transverse position, the corresponding resilient finger  138  replaces the affected nub  136  to its normal or unactuated position. 
   When the switch actuator arm  122  is in its latched first rotational or transverse position, the operator may push either of the handles  132  in the forward direction, causing the actuator arm  122  to compress a peripheral portion of the elastomeric rimmed washer  127 , rocking the actuator arm  122  so that its pushed end portion  142  is caused to be forwardly displaced. Such end portion  142  contacts and forwardly urges the correspondingly situated nub  136  for such time that the handle  132  is forwardly urged by the operator. When the operator releases the handle  132 , the resiliency of the washer  127  replaces the actuator arm  122  end portion  142  to its normal undepressed position thereby permitting the resilient finger  138  of the affected nub  136  to replace such nub  136  in its normal unactuated position. 
   It may be appreciated that the forward displacement of the actuator arm ends, and their resilient replacement, may be implemented by other mechanisms, for example by increasing the longitudinal elasticity of the actuator arm itself. 
   The forward face of the insert plate  134  is covered with a non-conductive elastomeric sheet, such as a rubber membrane  146  secured to the plate  134 . The tail cap insert  130  is mounted within the tail cap  50  by screw  148 , with the rubber membrane  146  obverse and in proximity to the rear face  150  of the tail cap battery terminal circuit board  118  also secured to the tail cap  50  by the screw  148 . The respective free end portions  151 ,  153  of the resilient contacts  152 ,  154  secured to the tail cap circuit board&#39;s rear face  150  are situated directly forwardly of the nubs  136  with the rubber membrane  146  interposed therebetween. When a nub  136  is forwardly displaced, such nub  136  presses (through the interposed rubber membrane  146 ) the corresponding resilient contact&#39;s end portion  151  or  153  into contact engagement with the circuit board&#39;s rear face  150 . 
   When the tail cap  50  is installed and latched to the housing  40 , the battery contacts  114 ,  116  secured to the circuit board&#39;s forward face  156  are in contact engagement with the respective battery cell terminals  43 ,  45 ; i.e., the battery contact  114  is in contact engagement with the positive terminal  43  of one of the battery cells  44 , and the battery contact  116  is in contact engagement with the negative terminal  45  of the other of the battery cells  44 . 
   The positive battery contact  114  ( FIG. 11 ) conductively communicates with a first conductive area  158  ( FIG. 12 ) on the rear surface  150  of the circuit board  118 , while the negative battery contact  116  conductively communicates with a second conductive area  160  on the rear face  150  of the circuit board  118  to which the resilient contact  154  is conductively secured. When the free end  153  of resilient contact  154  on the circuit board&#39;s rear face  150  is urged into contact engagement with the first conductive area  158 , there is established a conductive path between the negative battery terminal contact  116  and the positive battery terminal contact  114  (and hence between the negative and positive battery terminals  45 ,  43 ), thereby placing the switch device  48  in an ON position completing the electrical circuit between the battery  42  and the light emitter assembly  46 . 
   The positive battery contact  114  is conductively secured to a third conductive area  162  ( FIG. 11 ) on the forward face  156  of the circuit board  118 , while the resilient contact  152  on the circuit board&#39;s rear face  150  (but which is normally electrically isolated from the conductive areas on the circuit board&#39;s rear face  150 ) conductively communicates with the conductive area  162  on the circuit board&#39;s forward face  156 . When the free end  151  of the resilient contact  152  is urged into contact engagement with the second conductive area  160  on the circuit board&#39;s rear face  150 , there is established a conductive path between the positive battery terminal contact  114  and the negative battery terminal contact  116  (and hence between the positive and negative battery terminals  43 ,  45 ), thereby placing the switch device  48  in an ON position completing the electrical circuit between the battery  42  and the light emitter assembly  46 . 
   The switch device  48  is in an OFF position when the actuator arm  122  is in its normal position, i.e. in its first latched or transverse position and with neither of its end portions  142  forwardly depressed. It may be appreciated that when an operator manually urges either one of the handles  132  either downwardly or upwardly, the actuator arm  122  is rotated into either one of its latched second or third positions thereby placing the switch  48  in a CONSTANT ON position. The switch  48  remains in such CONSTANT ON position until the operator manually urges either one of the actuator arm handles  132  to effect a reverse rotation of the actuator arm  122  for causing the actuator arm  122  to be replaced in its latched first or transverse position, in which position the switch  48  is placed and maintained in its normal OFF position until further actuation by the operator. 
   It may be appreciated, as well, that the switch  48  may be actuated from an OFF position to a MOMENTARY ON position. When the actuator arm  122  is in its latched first or transverse position, the operator may manually forwardly urge or depress either one of the actuator arm handles  132 , placing the switch  48  in its ON position for only as long as the operator continues to depress the handle  132 . When the operator releases the handle  132 , the switch  48  resumes its normal OFF position. 
   An important feature of the preferred embodiment of the switch  48  is its ability to be actuated by either hand of the operator, in placing the switch  48  in its CONSTANT ON position and back to its normal OFF position, as well as for placing the switch  48  in its MOMENTARY ON position. 
   A second preferred tail cap switch embodiment  48 ′ is shown in  FIGS. 18 and 19 . This second embodiment  48 ′ is substantially the same as the first switch embodiment  48  except that, in addition to the CONSTANT ON/OFF and MOMENTARY ON switch operations actuable upon manipulation of either of the handles  132  at the ends of the switch actuator arm  122 , the second switch embodiment  48 ′ further includes a MOMENTARY ON remote switching capability provided by a type of switch commonly known as a slimline or tape switch  164 . Tape switches are well known in the art, and their construction typically includes spaced electrodes in a flexible enclosure to which pressure may be manually applied by an operator for squeezing the electrodes together thereby bringing them into electrical contact with each other. The electrodes resume their spaced condition when the operator discontinues the application of such pressure. Tape switches used with illumination apparatus removably attachable to handguns are described in U.S. Pat. No. 5,654,594 issued to Bernie E. Bjornsen, III, Peter Hauk and John W. Matthews and assigned to the assignee of the present invention, and in U.S. Pat. No. 6,276,088 issued to John W. Matthews and Paul Y. Kim and assigned to the assignee of the present invention, which patents are incorporated herein by reference. 
   The tape switch  164  which may be utilized in connection with the second preferred embodiment  48 ′ of the tail cap switch device includes two electrically conductive leads  166 ,  168  insulated from each other and extending from the tail cap  50 ′ to a pressure sensitive switch actuator  170  remote from the tail cap  50 ′. The switch actuator  170  may be positioned under the trigger guard  26  (as shown in phantom in  FIG. 2 ), or the switch actuator  170  may be of a type which horseshoes about the handgun grip as shown in the aforementioned U.S. Pat. Nos. 5,654,594 and 6,276,088 . 
   The tail cap-situated ends of the conductive leads  166 ,  168  are conductively secured to the tail cap circuit board  118  for conductively communicating with the positive and negative battery cell contacts  114 ,  116 . As shown in  FIG. 19 , the tape switch lead  166  is conductively secured to the first conductive area  158  of the circuit board&#39;s rear face  150 , which conductive area  158  conductively communicates with the positive battery contact  114  on the circuit board&#39;s forward face  156  as previously described. The tape switch lead  168  is conductively secured to the conductive area  160  on the circuit board&#39;s rear face  150 , which conductive area  160  conductively communicates with the battery cell negative terminal contact  116  on the circuit board&#39;s forward face  156  as previously described. Accordingly, when the circuit of the tape switch  164  is closed upon the application of pressure to the tape switch actuator  170 , the battery cell positive terminal  43  is conductively connected to the battery cell negative terminal  45  during such time that actuating pressure is continued to be applied to the tape switch actuator  170 . 
   It should be noted that, like the two switching modes of the tail cap switch  48  permitted by the switch actuator arm  122 , the remotely situated tape switch actuator  170  (whether situated under the trigger guard or horseshoed about the front of the handgun grip) may be operated with either of the operator&#39;s hands and, in addition, the tape switch actuator  170  may be operated by the same hand used for pulling the handgun&#39;s trigger. 
   It has been noted that the latch plate  80 , described in connection with  FIG. 6 , includes a transversely disposed elongate protuberance  84  having a width w slightly less than the slot  34  of the firearm&#39;s rail  30  for being received therein. Different firearm rails may have different slot widths, and indeed two well-known types of rails (namely, a Universal rail and a Picatinny rail) have slots of respectively different standardized widths. In order to accommodate both types of rails, the preferred embodiment of the accessory device  36  of the present invention may be provided with two types of replaceable latch plates. For example, the accessory device  36  may be provided with a latch plate  80  having a protuberance width w of approximately 0.125 inch for accommodating the transverse slot in a Universal rail, while another latch plate  80 ′ (shown in  FIG. 20 ) may be provided having a width w′ of its transversely disposed elongate protuberance  84 ′ of approximately 0.205 inch for accommodating the transverse slot of a Picatinny rail. Except for the differences in the width of the transverse protuberance shown as examples of the latch plate  80  and the latch plate  80 ′, the two latch plates  80 ,  80 ′ are substantially identical and one may be substituted for the other in the accessory device  36  according to the invention. 
   Accessory devices according to the invention, including the preferred embodiment  36  thereof, may be removably secured to firearms other than handguns, as well as to other types of firearms that do not have integral rails but are adapted for having accessory rail mount system devices secured thereto. Such rail mount system devices are well known in the firearms art, and may be of the type  172  (see  FIG. 21 ) comprising a series of longitudinally spaced-apart ribs  174  separated by transverse slots  176 , such as a Picatinny rail specified in MIL-STD-1913 incorporated herein by reference. 
   Such rail mount structures  172  may be secured to long arms, for example to a rifle or shotgun  176  illustrated in  FIG. 21  and as further disclosed in U.S. Pat. No. 6, 655,069 issued to Paul Y. Kim and incorporated herein by reference. Other examples of rail structures  172 , including Picatinny rails, on other types of firearms are disclosed in U.S. Pat. Nos. 6,508,027 and 6,622,416, both issued to Paul Y. Kim and incorporated herein by reference; and in U.S. patent application Ser. No. 10/447,874 of Paul Y. Kim and John W. Matthews, assigned to the assignee of the present invention and incorporated herein by reference. 
   As shown in  FIGS. 21 and 23 , the accessory device or light beam generator  36  may be removably secured to such rail structures  172  secured to firearms other than hand weapons. Where such rail structure  172  is of a type having Picatinny rails, the latch plate  80 ′ shown in  FIG. 20  would be installed in the accessory device  36 , with the transverse protrusion  34 ′ having a width w′ for matingly engaging any one of the Picatinny rail slots  176 . The accessory device  36  may be removably secured to the rail structure  172  in substantially the same way as the accessory device  36  may be removably secured to the rail  30  carried by the handgun  20 . The operator may adjust the longitudinal position of the accessory device  36  on the rail by depressing the handles  120  until a selected slot  176  has been encountered by the protuberance  34 . 
   As shown in  FIG. 21 , a handgrip  180  may be secured to the rail structure  172 , rearwardly of the light beam generator  36  but in proximity with the tail cap for permitting the operator to conveniently operate the tail cap switch device. In addition,  FIG. 21  shows a tape switch  164  connected to the tail cap and having an actuator horseshoed about the front of the handgrip  180 . In such configuration, and if both the accessory device  36  and the handgrip  180  are secured to the bottom rail  172  (as illustrated in  FIG. 23 ), the tail cap switch  48  may be actuated in both the CONSTANT ON/OFF and MOMENTARY ON modes with either hand. 
   The accessory device or light beam generator  36 , and in particular the housing  40 , elongate members  94 , pivot plate  80  and tail cap  50  may be manufactured using fabrication methods well-known in the art, of well known materials typically used in the art of making such components including rigid and durable materials such as polymeric materials as well as light weight aluminum alloys. 
   Although a target illuminator embodiment of the light beam generator  36  is described above in detail, laser aiming devices securable to rails carried by firearms are included within the scope of light beam generators according to the invention of the parent application. 
   The preferred embodiment of the accessory device according to the present invention, specifically the preferred embodiment of the light beam generator  236 , is shown with reference to  FIGS. 24-39 . Turning specifically to  FIGS. 27-39  (wherein primed reference numerals indicate components similar to components in  FIGS. 4-19  shown with corresponding reference numerals), the light beam generator  236  includes a housing  240  in which is contained a power source such as a battery  42 ′ of one or more battery cells  44 ′ (for example, two 3-volt lithium battery cells  44 ′) similarly to the power source described above with respect to the light beam generator  36 . Also similarly to the light beam generator  36 , a light emitter assembly  46 ′ is carried by the light beam generator housing  240  forwardly of the battery  42 ′ and in circuit with a positive front terminal of one of the battery cells  44 ′ and a negative front terminal of another of the battery cells  44 ′. The switch device  48 ′ (similar to the switch device  48  previously described) is preferably situated at the rear of the housing  240  in and including a tail cap  50 ′, the switch device  48 ′ including a switch actuator assembly  49 ′ for selectively completing and opening the light emitter energization circuit. In the embodiment shown, this is accomplished by the switch actuator assembly  49 ′ establishing a conductive path between the rear positive terminal  43 ′ of one of the battery cells  44 ′ and the rear negative terminal  45 ′ of the other of the battery cells  44 ′ for placing the switch device  48 ′ in an ON position causing the battery  42 ′ to energize the light emitter assembly  46 ′, and by opening such conductive path for placing the switch in an OFF position where the battery  42 ′ does not energize the light emitter assembly  46 ′. 
   The preferred light emitter assembly  46 ′ shown in  FIG. 28 , as well as alternative embodiments thereof, are described above in connection with the light emitter assembly  46  shown in  FIG. 5 . Similarly, the structure and operation of the switch device  48 ′ and tail cap  50 ′ of the enhanced light beam generator  236 , shown in  FIGS. 27 and 28 , are described above in connection with the switch device  48  and tail cap  50  shown in  FIGS. 4 ,  5  and  10 - 19 . 
   Considering  FIGS. 27 and 33 , the preferred embodiment of the housing  240  of the light beam generator  236  of the present invention includes a substantially flat upwardly facing or top surface  300 . Two upstanding first wall segments  302  longitudinally extend forwardly along opposite sides of the top surface  300  from the vicinity of the housing&#39;s rear end  303 , two upstanding second wall segments  304  longitudinally extend forwardly of the respective first wall segments  302 , and two upstanding third wall segments  306  longitudinally extend forwardly of the respective second wall segments  304 . The forward generally vertical ends  308  of the respective first wall segments  302  are transversely aligned, and the rearward generally vertical ends  310  of the respective second wall segments  304  are transversely aligned and longitudinally spaced from the second wall segments&#39; forward ends  308  by a predetermined distance f. The forward generally vertical ends  312  of the respective second wall segments  304  are transversely aligned and longitudinally spaced from the rearwardly facing transversely aligned generally vertical ends  314  of the third upstanding wall segments  306  by a predetermined distance g. 
   A transversely disposed pin  70 ′ is secured to the housing  240  in the vicinity of its rear end  303  and above the housing&#39;s top surface  300 . The transverse pin  70 ′ is secured to the first wall segments  302  in the vicinity of their rear ends and above the top surface  300 . The pin  70 ′ additionally extends through apertures in two upstanding protuberances or partitions  72 ′ from the top surface  300 . The two partitions  72 ′ are laterally spaced so as to divide the transverse pin  70 ′ into three exposed segments  74 ′,  76 ′,  78 ′ which may be of substantially equal lengths. 
   The light beam generator  236  includes a latch plate  316  in cooperative engagement with and preferably removably secured to the housing  240 . Similarly to the latch plate  80  shown in  FIGS. 4-8 , the latch plate  316  shown in  FIGS. 27-32  includes a generally U-shaped rear end  82 ′ configured for receiving the middle segment  76 ′ of the transverse pin  70 ′. One leg (preferably the upper leg  83 ′) of the U may curve over a portion of the generally rearwardly facing opening of the U, and the plate  316  is preferably made of a material such that the legs are somewhat resilient. As illustrated in  FIG. 27 , the latch plate  316  is installed to the housing  240  by placing the opening of the latch plate&#39;s rear end  82 ′ to the transverse pin segment  76 ′, and the installer urging the rear end  82 ′ to snap onto the pin segment  76 ′. The latch plate  316  accordingly is hinged at its rear end  82 ′ about the transverse hinge pin  70 ′, specifically about the hinge pin segment  76 ′; i.e., the latch plate  316  is pivotally secured to the housing  240  about a transverse axis t along the pin  70 ′ (see also  FIG. 33 ). 
   As shown in  FIGS. 29-32 , the preferred embodiment of the latch plate  316  is configured as a generally U-shaped plate including two legs  318  extending along opposite sides of a longitudinal axis b, with the base  320  of the U rearwardly extending to the plate&#39;s rear end  82 ′. The legs  318  are transversely (preferably equally) spaced from the plate&#39;s longitudinal axis b, and extend from an opening  322  through the plate  316  preferably having a transverse dimension greater than the distance separating the two legs  318 . In the illustrated plate embodiment, the opening  322  is generally circular with a diameter greater than the transverse distance separating the two legs  318 , as shown in  FIG. 29 . The plate  316  is fabricated of a material (such as nylon) having sufficient resiliency for permitting the free ends  324  of the legs  318  to be transversely displaced toward one another when forces are transversely applied simultaneously to the legs  318  toward the longitudinal axis b, and for resiliently tending to return the free ends  324  of the legs  318  to their normally spaced-apart position (as shown in  FIG. 29 ) when the applied forces are removed. 
   Each of the legs  318  includes an upstanding protuberance  326 , preferably a transversely disposed elongate protuberance  326 , in the vicinity of the legs&#39; free ends  324 , the elongate upstanding protuberance  326  having a width w (along the longitudinal direction) slightly less than the width of the slot  34  in the firearm&#39;s rail  30  for being received therein. In the illustrated embodiment, lateral arms  328  transversely extend outwardly from the respective legs  318 , the arms  328  extending from the vicinity of the legs&#39; free ends  324  and being of a width (along the longitudinal direction) slightly less than the distance between the rear ends  314  of the third wall segments  306  and the forward ends  308  of the housing&#39;s first wall segments  302 , each of the arms  328  having a cutout section  330  for receiving the second wall segments  304  when the latch plate  316  is installed to the housing  240 . The arms  328  terminate with longitudinal handles  332  laterally extending from the housing  240  when the latch plate  312  is installed to the housing (see, for example,  FIGS. 25 and 35 ). 
   When the assembled light beam generator  236  is installed to the firearm rail  30  (as shown in  FIGS. 24 and 25 ), the latch plate  316  co-acts with the housing  240  such that the free ends  324  of the legs  318  may be caused to assume a first vertical position in which the latch plate&#39;s upstanding protuberances  326  are lower than and therefore not receivable in the rail slot  34  ( FIGS. 37 and 38 ), and alternatively the free ends  324  of the legs  318  may be caused to be supported by the housing  240  in a second vertical position in which the upstanding protuberances  326  are receivable in the rail slot  34  ( FIGS. 35 and 36 ). In the illustrated embodiment, each of the plate&#39;s legs  318  includes a protuberance  334  forwardly extending from the legs&#39; free ends  324  and preferably slightly depending therefrom. The forward protuberances  334  are transversely (preferably equally) spaced from the plate&#39;s longitudinal axis b and are configured to be respectively supported by two upwardly facing support surfaces  336  of the battery housing  240 . The support surfaces  336  are situated just inwardly of the third wall segments  306  and forwardly of the third segment&#39;s rear ends  314 , the two support surfaces  336  being transversely (preferably equally) spaced from the housing&#39;s longitudinal axis b′ (which is directly beneath the plate&#39;s longitudinal axis b when the plate is installed to the housing). The two support surfaces  336  are at a height above the housing&#39;s upwardly facing flat surface  300  such that the free ends  324  of the legs  318  are in the second vertical position with the upstanding protuberances  326  of the installed latch plate  316  at a height for being received by the rail slot  34  when the light beam generator is installed to the rail  30 . 
   The inner boundary of each raised support  336  defines an outwardly lateral wall  338  of respective depressions  340  for receiving the forward protuberances  334  when a user applies inwardly directed forces to the handles  332  and downwardly pivots the latch plate  316  about the transverse axis t, i.e. about the pivot pin  70 ′. As shown in  FIGS. 37 and 38 , such application of forces (represented by force arrows  346 ) inwardly urge the two resilient legs  318  such that their free ends  324  are displaced toward one another, and along with the downward pivoting of the latch plate  316 , causes the forward protuberances  334  to enter the depressions  340  until the bottom surface  342  of the depressions engage the respective floors  344  of the depressions  340  (which floors  344  may be continuations of the housing&#39;s upwardly facing surface  300 ,  FIG. 38 ). When the applied force is removed by the user, the resiliency of the legs  318  causes the forward protuberances  334  to be outwardly biased against the respective depression walls  338 , thereby retaining the forward protuberances  334  in the depressions  340 . The height of the depression floors  340  is such that the free ends  324  of the legs  318  are in the first vertical position with the upstanding protuberances  326  of the installed latch plate  316  at a height below the rail  30  and therefore not receivable in the rail slot  34 . 
   As shown in  FIGS. 34 and 32 , the wall  338  of each of the depressions  340  may be inwardly sloped by an angle α (e.g. 5 degrees from vertical), and the outer sides of the forward protuberances  334  may be complementarily sloped, for assisting the releasable retention of the forward protuberances  334  within the depressions  340 . 
   The latch plate  316 , described in connection with  FIGS. 29-32 , includes upstanding transverse elongate protuberances  326  having a width w slightly less than the slot  34  of the firearm&#39;s rail  30  for being received therein. As previously noted, different firearm rails have different slot widths, including two well known types of rails (namely, a Universal rail and a Picatinny rail) having slots of respectively different standardized widths. In order to accommodate both types of rails, the preferred embodiment of the accessory device  236  of the present invention may be provided with two types of replaceable latch plates. For example, the accessory device  236  may be provided with a latch plate  316  having an upstanding protuberance width w of approximately 0.125 inch for accommodating the transverse slot in a Universal rail, while another latch plate  316 ′ (shown in  FIG. 39 ) may be provided with its transversely disposed upstanding elongate protuberances  326 ′ having a width w′ of approximately 0.205 inch for accommodating the transverse slot of a Picatinny rail. Except for the differences in the width of the upstanding protuberances shown as examples of the latch plate  316  and the latch plate  316 ′, the two latch plates  316 ,  316 ′ are substantially similar and one may be substituted for the other in the accessory device  236 . 
   Similarly, accessory devices according to the present invention, including the preferred embodiment  236  thereof, may be removably secured to firearms other than handguns, as well as to other types of firearms that do not have integral rails and are adapted for having accessory rail mount system devices secured thereto. Such rail mount system devices are well known in the firearms art, including the Picatinny rail  172  described above in connection with  FIGS. 21 and 22 . As shown in  FIG. 26 , the accessory device or light beam generator  236  may be removably secured to such rail structures  172 , which rail structures may be secured to firearms other than handguns as previously discussed in connection with  FIGS. 21-23 . 
   The accessory device or light beam generator  236  includes two elongate members  294 ,  295  removably secured to the housing  240 , for interfacing with the firearm rail  30  to enable the housing  240  to be retainably slid along the rail  30  or  172  (see, in particular, FIGS.  1  and  24 - 28 ). Each elongate member  294 ,  295  includes an inwardly directed tongue  238  longitudinally extending along such member  294 ,  295 ; i.e., the elongate rail interface members  294 ,  295  are installed to the housing  240  with the longitudinal tongue  238  of one of the members  294 ,  295  facing the longitudinal tongue  238  of the other of the members  294 ,  295 , the tongues  238  complementing the firearm rail&#39;s longitudinal grooves  32  for slidably cooperating with the rail&#39;s longitudinal grooves  32  while being vertically retained by the rail  30  (or the rail  172 ) as shown in  FIGS. 25 and 26 . 
   The elongate rail interface members  294 ,  295  are installed to the housing  240  after the latch plate  316  has been placed to the housing  240  as previously described. Each member  294 ,  295  includes a flat bottom surface  296 ,  297 , respectively, for contacting the top surfaces of the first, second and third wall segments  302 ,  304 ,  306 . The members  294 ,  295  include bores  370  therethrough aligned with internally threaded blind vertical bores  372  in the wall segments  302 ,  304 ,  306 , the members  294 ,  295  being removably secured to the walls by headed screws  374  respectively extending into the bores  370  through the members  294 ,  295  and threaded into the respectively aligned threaded bores  372  in the housing  240 . 
   With the elongate members  294 ,  295  so installed, their bottom surfaces  296 ,  297 —which contact and extend along the top surface of the wall segments  302 ,  304 ,  306 —bridge those wall segments and provide a ceiling to the spaces between them. Such bridges or ceilings upwardly capture the lateral arms  328  within such spaces, while the wall ends  308 ,  310  and  312 ,  314  longitudinally capture the lateral arms  328  within such spaces, resulting in the hinged latch plate  316  being captured to the housing  240  as well. 
   The elongate rail interface members  294 ,  295  may be removed from the housing  240  by unscrewing the screws  374 , and if desired the elongate rail interface members  294 ,  295  may be replaced by other or different elongate rail interface members which are similarly removably securable to the housing  240 . It may be appreciated that when the rail interface members  294 ,  295  have been removed from the housing  240 , the lateral arms  328  of the hinged latch plate  240  are no longer upwardly blocked or captured by the members  294 ,  295 , so that the latch plate  240  may be pivoted about the hinge pin  70 ′ away from the surface  300  of the housing  240  and pulled away from the hinge pin  70 ′. In such manner, the latch plate  316  may be removed from the housing  240 , and a replacement latch plate  316  or a different latch plate (such as the latch plate  316 ′), which is similarly removably securable to the housing  240 , may be hinged to the hinge pin  70 ′ and captured to the housing  240  by reinstalling the rail interface members  295 ,  295 . 
   When the light beam generator  236  is in its assembled condition (i.e., with the tail cap switch  48 ′, light emitter assembly  46 ′, latch plate  316  and rail interface members  294 ,  295  installed to the housing  240  as described above), the assembled light beam generator  236  may be removably installed to the firearm rail  30  (or  172 ). The user typically holds the light beam generator  236  in one hand and transversely urges the handles  332  inwardly (i.e. applies transverse inwardly directed forces to the handles  332 ) such as with his/her thumb and index finger, while downwardly urging the handles  332  (such as with the same thumb and index finger). Such maneuver causes the resilient legs  318  to be squeezed toward one another at their free ends  324  while being downwardly pivoted, causing the forward protuberances  334  at the legs&#39; free ends  324  to transversely inwardly slide from their respective support surfaces  336  and into the respective depressions  340 . The user may release the inwardly transverse and downward urging, whereupon the resilient legs  318  bias the forward projections  334  laterally against the generally lateral substantially vertical walls  338  of the depressions  340 . The free ends  324  of the legs  318  are thereby releasably retained in their first vertical position with the upstanding protuberances  326  at a height where they are unable to be received in the slot  34  of the rail  30  when the light beam generator  236  is applied to the rail  30 . The light beam generator  236  is then placed to the rail  30  with the rear ends of the tongues  238  (see  FIG. 25 ) of the rail interface members respectively engaging the forward ends of the grooves  32  of the rail  30  carried by the firearm  20 . The light beam generator  236  is thereupon rearwardly urged by the user, thereby sliding the housing  240  along the rail  30  while the housing  240  is being vertically retained by the rail  30 . 
   When the light beam generator  236  has been rearwardly slid along the rail  30  until the latch plate&#39;s upstanding protrusions  326  are vertically aligned beneath the rail slot  34 , the user upwardly urges the latch plates&#39; handles  332 , which action causes the latch plate  316  to be upwardly pivoted about the hinge pin  70 ′, causing the latch plate&#39;s forward protuberances  234  to be upwardly removed from their respective depressions  340 . The resiliency of the latch plate&#39;s legs  318  outwardly urges the forward protuberances  334  to engage and be supported by their respective support surfaces  336 . Consequently, the free ends  324  of the latch plate legs  318  are supported in the second vertical position with the upstanding protuberances  326  received in the rail slot  34 . 
   As earlier noted, the width w of the upstanding protuberances  326  is slightly less than the width of the slot  34  such that the upstanding protuberances  326  just fit into the slot  34 . The engagement of the upstanding protuberances  326  with the slot  34  stops further longitudinal movement of the housing  240  along the rail  30 , longitudinally latching the housing  240  in this position. The longitudinal positions of the slot  34  and of the upstanding protuberances  326  are preferably predetermined such that the rear end of the tail cap  50 ′ is situated just forwardly of or in contact with the handgun&#39;s trigger guard  26  when the upstanding protuberances  326  are received in the slot  34 . 
   To remove the accessory device or light beam generator  236  from the firearm rail  30 , the user transversely inwardly and downwardly urges the laterally protruding handles  332 , causing the legs  318  of the plate  316  to be squeezed together and the latch plate  316  to be downwardly pivoted about the hinge pin  70 ′. As previously described, this action results in the forward protuberances  334  being removed from their respective support surfaces  336  and received by their respective depressions  340 . The user&#39;s release of such inward and downward urging results in the forward protuberances  334  being resiliently urged against the depressions&#39; outer walls  336 , thereby releasably retaining the latch plate legs&#39; free ends  324  in their first vertical position with the upstanding protuberances  326  removed from the slot  34 . The user thereupon forwardly urges the light beam generator  236  to slide along the rail  30  until the light beam generator  236  is removed therefrom. 
   The rail interface members  294 ,  295  may be configured to accommodate differences in the dimensional tolerances of firearm rails  30  manufactured by different manufacturers, and even among firearm rails manufactured by the same manufacturer. In a preferred embodiment of the rail interface members  294 ,  295  for accommodating such differences, the bores  370  and counterbores in the rail interface members  294 ,  295  may be configured similarly as the bores  102  and the counterbores  103  in the rail interface members  94  as previously described (see  FIG. 9 ). During installation of the light beam generator  236  to a particular firearm rail  30 , if the engagement of the rail interface members  294 ,  295  to the rail  30  is too loose, the user may simply loosen the screws  374 , move the rail interface members  294 ,  295  inwardly (transversely toward each other) and thereupon tighten the screws  374 . If the engagement between the rail interface members  294 ,  295  and the rail  30  is too tight, the user may loosen the screws  374 , move the rail interface members  294 ,  295  outwardly (transversely away from each other) and tighten the screws  374 . In either event, the adjustment assists in the prevention of transverse movement of the accessory device  236  with respect to the rail  30  which may be caused, for example, upon discharge of the firearm. 
   The accessory device or light beam generator  236  may be manufactured using fabrication methods well-known in the art, of well-known materials typically used in the art of making such components including rigid and durable materials such as polymeric materials as well as lightweight aluminum alloys, and resilient materials such as nylon materials. In an example of the preferred embodiment of the light beam generator  236 , the housing  240  may be fabricated of an aluminum alloy; and the latch plate  316  and the elongate members  294 ,  295  may be fabricated of a nylon material. 
   Although a target illuminator embodiment of the light beam generator  236  is described above in detail, laser aiming devices securable to rails carried by firearms are included within the scope of light beam generators according to the present invention. 
   Thus, there has been described a preferred embodiment of an accessory device which is removably securable to a longitudinal rail carried by a firearm, which accommodates longitudinal rails of different configurations carried by firearms, and which includes a removably securable latching device. The light beam generator of the preferred embodiment includes a removable tail cap switch actuable by either hand of an operator for placing the switch in CONSTANT ON/OFF positions and in a MOMENTARY ON position, as well as for remote actuation by either hand to a MOMENTARY ON position. Other embodiments of the present invention, and variations of the embodiments presented herein, may be developed without departing from the essential characteristics thereof. Accordingly, the invention should be limited only by the scope of the claims listed below.