Patent Publication Number: US-6336283-B1

Title: Rifle sighting apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an apparatus for effecting the sighting of a rifle to accurately align the sights provided on the rifle with the normal eye position of the user when firing the rifle, and particularly to a mechanism for eliminating the effects of trigger jerking on the accuracy of the sighting. 
     2. Description of the Related Art 
     A necessary step in the utilization of any new rifle by its purchaser is to adjust the sights of the rifle, particularly the rear sights thereof, to permit the accurate firing of the rifle by its new user. As is well known, the physical contour ii and dimensional location of the eyes of individuals vary substantially, so it is quite important that the rifle be sighted in by the particular user. Resighting is also required if any change in ammunition is effected. 
     Such sighting is generally accomplished with the barrel of the rifle resting on a support, such as a rail fence, and the stock of the rifle positioned against a fixed support adjacent the shoulder of the user in substantially the same position that the user would expect to assume during all subsequent firing of the rifle. The precaution of resting the barrel and stock of the rifle on fixed supports does not, however, eliminate the adverse effects of an improper trigger squeeze or jerking of the trigger. This is the most common fault encountered not only in the firing of the rifle, but also in the sighting of it, and a jerking of the trigger, however slight, will disturb the accuracy of the sighting. There is a need, therefore, for an apparatus which will permit the sighting of the rifle to be accomplished without utilization of the user&#39;s finger to depress the trigger. 
     SUMMARY OF THE INVENTION 
     In accordance with this invention, a trigger operating apparatus is provided which is clampable on the rifle by two plates respectively positioned on opposite sides of the trigger guard commonly found on every rifle. In one embodiment of the present invention, a spacer block is secured to one of the plates, disposed within the trigger guard and abutting the forward portion of the trigger guard. The spacer block receives one or more clamping bolts which traverse the other plate. A shaft is rotatably mounted in one of the plates and has an inner end portion lying within the trigger guard and adjacent to the trigger in its unfired position. The outer end of the shaft projects exteriorly of the mounting plate and mounts a manually graspable knob. On the inwardly projecting portion of the shaft, a cam is formed which, by rotation of the shaft, engages the trigger and depresses the trigger to its firing position. Preferably, the shaft is slowly rotated by the user of the rifle and the trigger is cammed rearwardly with a substantially continuous motion. Even if the shaft is rotated at a higher than recommended speed, no jerking of the trigger will result because the cam action moves the trigger smoothly from its inactive position to its firing position. 
     In another embodiment of the present invention, a trigger operating apparatus is provided which is clampable on the rifle by two plates designed for use by either a right-handed or left-handed user. Those plates are respectively positioned on opposite sides of the trigger guard. The one plate has a recessed area on its periphery to engage the interior surfaces of the trigger guard on either the right or left side. The two mounting plates are secured together by one or more clamping bolts. A cam mounting shaft traverses the mounting plates and extends outwardly from one of the mounting plates for mounting of a manually graspable knob. A rotary cam is secured to the shaft for co-rotation in a selected direction, which rotation is opposed and limited by a helical spring mounted between the cam and the one mounting plate. Preferably, the right-handed user will slowly rotate, either clockwise or counter-clockwise, depending on the cam design, the manual knob which is on the right side of the trigger guard, thereby camming the trigger rearwardly with a substantially continuous motion. For left-handed firing, the mounting plates are reversed in position and the manually operable knob is on the left side of the trigger guard. The cam operation, however, is the same as in the right-handed configuration. Thus, accurate sighting for either a right-handed or left-handed user of the rifle may be accomplished by the elimination of trigger jerking. 
     In yet another embodiment of the present invention, a trigger operating apparatus with a lock and key feature is secured on the rifle by two clampable plates respectively positioned on opposite sides of the trigger guard. A shaft is rotatably mounted in one of the clampable plates, and an inner end portion of the shaft lies within the trigger guard and adjacent to the trigger in its unfired position. The outer end of the shaft projects exteriorly of the mounting plate and passes through a spring keeper cylinder and is positioned inside a key housing. A bolt aligns the key housing with the spring keeper cylinder. The key housing, which is fitted with the shaft and spring keeper cylinder, is secured to the mounting plate with housing retainer screws. Preferably, the shaft is slowly rotated and the trigger is cammed rearwardly by inserting a key into the key housing and turning with substantially continuous motion. Even if the shaft is rotated at a higher than recommended speed, no jerking of the trigger will result since the cam action moves the trigger smoothly from its inactive position to its firing position. 
     Still another embodiment of this invention comprises a mounting plate with one or more plug portions extending from the mounting plate. A shaft is rotatably mounted in the mounting plate and a cam is attached to the shaft for engagement with the trigger as in the above-described embodiments, and the apparatus is secured to the trigger guard by pressing the plug portions into the trigger guard. Alternatively, a mounting plate having one or more clamping plates extending therefrom may be used to mount the apparatus to the trigger guard. 
     Further objects and advantages of the present invention will be readily apparent to those skilled in the art from the following detailed description taken in conjunction with the annexed sheets of drawings, which illustrate several preferred embodiments of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic perspective view illustrating the sighting of a rifle incorporating this invention. 
     FIG. 2 is an enlarged scale side elevational view of the trigger guard portion of the rifle of FIG. 1 with a trigger actuating mechanism embodying this invention assembled thereto. 
     FIG. 3 is an exploded perspective view of FIG.  2 . 
     FIG. 4 is an exploded perspective view illustrating the mounting of the spring which opposes and limits the turning movement of the operating knob. 
     FIG. 5 is an enlarged scale, exploded perspective view of the trigger guard portion of the rifle of FIG. 1 with an alternative trigger actuating mechanism embodiment assembled thereto for right-handed operation. 
     FIG. 6 is an enlarged scale, exploded perspective view of the trigger guard portion of the rifle of FIG. 1 with an alternative trigger actuating mechanism embodiment assembled thereto for left-handed operation. 
     FIG. 7 is an enlarged scale front elevational view of the cam utilized in FIGS. 5 and 6. 
     FIG. 8 is a side elevational view of the cam of FIG.  7 . 
     FIG. 9 is rear elevational view of the cam of FIG.  7 . 
     FIG. 10 is an exploded perspective view illustrating another alternative embodiment of the present invention having a lock and key apparatus. 
     FIG. 11 is a perspective view of the key of FIG. 10 as viewed from the opposite direction as FIG.  10 . 
     FIG. 12 is a front elevational view of the lock of FIG.  10 . 
     FIG. 13 is a sectional view of the lock housing of FIG.  10 . 
     FIG. 14 is a perspective view of an alternative cam in accordance with the present invention. 
     FIG. 15 is an exploded perspective view illustrating yet another alternative embodiment of the present invention. 
     FIG. 16 is an exploded perspective view illustrating still another alternative embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to FIG  1 , it is customary to sight in a new by positioning the rifle R against the shoulder of the user and supporting the barrel of the rifle on an appropriate support post P 1 . The stock may also be supported by a post P 2 . In accordance with this invention, the trigger of the rifle is actuated by turning knob  7  which drives an actuating element for the trigger. 
     Referring now to FIGS. 2-4 of the drawings, the trigger actuating mechanism  1  embodying this invention for a right-handed shooter comprises a generally oval shaped shaft mounting plate  2   b  and an opposing plate  2   a  which are adapted to engage the sides of the trigger guard TG which normally surrounds the trigger T. Preferably, a spacer block  3  is formed on one of the plates, preferably plate  2   a  for right-handed users, and is machined to a thickness such that when plate  2   b  is brought into engagement or near engagement with spacer block  3 , the two plates  2   a  and  2   b  will snugly engage the sides of trigger guard TG. Plate  2   a  preferably has a portion of its periphery cut away to define a shoulder  2   c  which engages the side wall of trigger guard TG and also defines a wall portion  2   d  which engages the inner surface of the rear portion of trigger guard TG. Spacer block  3  has an end surface  3   a  engagable with the inner surface of the front portion of trigger guard TG. Thus, plate  2   a  is secured against displacement relative to trigger guard TG. Plates  2   a  and  2   b  are snugly secured together by one or more fasteners such as screws or bolts  4 . Preferably, bolt  4  traverses a hole  2   e  provided in plate  2   b  and engages a tapped hole  3   b  in spacer block  3 . Alternatively, spacer block  3  could be eliminated and plates  2   a  and  2   b  could be secured to trigger guard TG by two bolts. If it is desired to use only a single bolt, then a pair of dowel pins  5  are preferably press fitted into face  3   c  of spacer block  3  and cooperate with holes  2   k  provided in plate  2   b , thereby preventing relative angular displacement of plates  2   a  and  2   b.    
     A trigger actuating shaft  6  is rotatably mounted within a hole  2   g  provided in plate  2   b . The outer end portion of shaft  6  may be enlarged to form a manually operable knob  7 . Alternatively, knob  7  may be separately formed and then press fitted onto the outer end portion of shaft  6 . The inwardly projecting end of actuating shaft  6  mounts a cam  8  with screw  10  which screws into a tapped hole (not shown) in the inwardly projecting end of shaft  6 . Cam  8  is positioned closely adjacent to trigger T in its inactive or nonfiring position when plates  2   a  and  2   b  are clamped together around trigger guard TG by bolt  4 . Cam  8  is designed to effect a rearward displacement of trigger T by rotation of knob  7 . Whether this rotation is clockwise or counter-clockwise depends solely on the preference of the user of the trigger operating mechanism. In either event, rotation of knob  7  effects rotation of cam  8  and in turn produces a gradual rearward movement of trigger T to its firing position. This arrangement substantially eliminates jerking of trigger T because any speed of manual rotation of knob  7  still results in a smooth rearward displacement of trigger T. 
     Cam  8  is preferably hollow to provide a mounting notch  8   a  for a torsion spring  9 . One end  9   a  of spring  9  is anchored to notch  8   a  of cam  8  while the other end  9   b  engages in a slot  2   h  formed on the inner side of plate  2   b  immediately adjacent hole  2   g . Slot  2   h  is shown only by dotted lines in FIG.  4 . From its neutral position, spring  9  permits only a limited rotational movement of knob  7 , shaft  6 , and cam  8  in the direction required to produce movement of trigger T. When knob  7  is rotated in the selected direction to produce firing of trigger T, such movement is resisted by spring  9 , resulting in a winding up of spring  9  on shaft  6  to a collapsed or limiting position after cam  8  reaches the trigger firing position. Spring  9  thus serves as a resilient rotation limiter. This function of spring  9  is very important because it insures that knob  7  must be released to return to its neutral position before the trigger can again be actuated. In other words, the actuation of knob  7  only results in successive single shot firings of the rifle R. Since many modern hunting rifles are of the semi-automatic type, the trigger actuating mechanism embodying this invention is primarily useful in the initial sighting of the rifle or in the sighting of the rifle when changes in ammunition are desired by the user. It is not contemplated that this invention will be utilized to fire the rifle in target competition or in game hunting because the rotation of the knob  7 , when the front end of the rifle R is not firmly supported, will produce an undesirable movement of the rifle R during the trigger actuating process. In the sighting operation, the forward end of the rifle R is firmly supported and held against the support posts P 1  and P 2  by the user, hence the rotational movement of the knob  7  does not produce any displacement of the barrel of the rifle R from the desired line of sight. 
     Referring now to FIGS. 5-9 of the drawings, there is shown an alternate trigger actuating mechanism  12  which may be utilized for right-handed or left-handed firing. This embodiment of the invention comprises a generally oval shaped mounting plate  14   b  and an opposing plate  14   a  which are adapted to engage the sides of the trigger guard TG which normally surrounds the trigger T. Preferably, plates  14   a  and  14   b  are machined to a configuration so that the two plates will snugly engage the opposite sides of the trigger guard TG. Mounting plate  14   b  preferably has a portion of its periphery cut away to define a shoulder  14   c  which engages the inner surface of the front portion of the trigger guard TG and also defines a wall portion  14   d  which engages the inner surface of the rear portion of trigger guard TG. Thus, mounting plate  14   b  is secured against displacement relative to the trigger guard TG. The two plates  14   a  and  14   b  are snugly secured together by one or more fasteners, such as screw or bolt  16 . Preferably, bolt  16  traverses a hole  14   e  provided in plate  14   a  and engages a tapped hole  14   f  in plate  14   b . In FIG. 5, plates  14   a  and  14   b  are assembled to trigger guard TG for right-handed firing. In FIG. 6, plates  14   a  and  14   b  are assembled to trigger guard TG for left-handed firing. In either position, trigger actuating shaft  18  is rotatably mounted within a hole  14 g provided in mounting plate  14   b . The outer end portion of shaft  18  may be enlarged to form a manually operable knob  20 . Alternatively, knob  20  may be separately formed and then press fitted onto the outer end portion of shaft  18 . The inner end of shaft  18  may be internally tapped to receive threaded screw  24 . 
     The inwardly projecting end of shaft  18  mounts a cam  26  which is co-rotatably secured thereto by screw  24 . Cam  26  is positioned closely adjacent to the trigger T in its inactive or nonfiring (neutral) position when plates  14   a  and  14   b  are secured together around trigger guard TG by bolt  16 . Cam  26  has a cam surface  26   h  designed to effect a rearward displacement of the trigger T by rotation of shaft  18  with knob  20 . Whether this rotation is clockwise or counter-clockwise depends solely on the preference of the user of the trigger operating mechanism and appropriate design of cam surface  26   h . In either event, rotation of knob  20  in the selected direction effects rotation of cam  26  and in turn produces a gradual rearward movement of the trigger T to its firing position. Again, this arrangement substantially eliminates jerking of the trigger T because any speed of manual rotation of knob  20  still results in a smooth rearward displacement of trigger T. A helical spring  28  is mounted on shaft  18  between cam  26  and the inner surface  14   k  of mounting plate  14   b . Spring  28  opposes and limits rotary movement of cam  26 . Referring to FIGS. 7-9, one end face  26   a  of cam  26  (FIG. 7) has a hollow portion and angularly spaced generally tangential slots  26   b - 26   g  for receiving one end  28   a  of spring  28 . The other end face of cam  26  has a recess  26   k  to receive the head  24   a  of screw  24 . For right-handed shooters, one of three slots  26   b ,  26   c , or  26   d  may be selectively utilized to receive end  28   a  of spring  28  to oppose clockwise rotation of cam  26  with different torsional resistances. For left-handed shooters, one of slots  26   e ,  26   f , or  26   g  selectively receives end  28   a  of spring  28 . The other end  28   b  of spring  28  selectively engages one of slots  14   h  or  14   j  formed on the inner face  14   k  of plate  14   b  immediately adjacent to hole  14   g . The selection of different slots to engage the ends of spring  28  permits the selection of a desired positioning of cam  26  relative to the trigger T and a desired resistance to rotation of knob  20 . In its normal inactive (neutral) position, the spring  28  permits only a limited rotational movement of knob  20  in the direction required to produce firing of the trigger T. When knob  20  is rotated in the direction to produce firing of trigger T, such movement is resisted by spring  28 , resulting in a winding up of spring  28  until cam  26  reaches the trigger firing position. Spring  28  thus serves as a resilient rotation limiter. Once again, this function of spring  28  is very important in either the right-handed or left-handed assembly of the present invention because knob  20  must be released to return to its neutral position before the trigger can again be actuated. Thus, the actuation of knob  20  only results in successive single shot firings of the rifle R. 
     Referring to FIG. 10, another alternative embodiment  100  of the present invention contains a lock and key apparatus for improved safety and security. This alternative embodiment  100  contains a mounting plate  30  that is similar to mounting plate  14   b  of FIGS. 5 and 6, except that mounting plate  30  has one or more holes  30   e  for attaching a lock housing  60 , as further described below. Mounting plate  30 , which cooperates with an opposing plate  14   a  (not shown in FIG. 10) as in FIGS. 5 and 6, has a tapped hole  30   f  for receiving bolt  16  (not shown in FIG. 10) as in FIGS. 5 and 6. Mounting plate  30  also has slots  30   c  and  30   d  in the surface opposite surface  30   b  similar to slots  14   h  and  14   j  as in FIGS. 5 and 6 for receiving end  28   b  of spring  28 . End  28   a  of spring  28  engages cam  26  as previously described in connection with FIGS. 5 and 6. As shown in FIG. 10, the lock mechanism of this embodiment comprises a lock shaft  50  having a cylindrical portion  50   a  on one end for insertion through hole  40   a  of a spring keeper cylinder  40  and through hole  30   a  of mounting plate  30 . Spring keeper cylinder  40  has a plurality of blind holes  40   b  extending partially into cylinder  40  from face  40   c . Blind holes  40   b , which are preferably of uniform depth, receive a matching plurality of pin springs  42  followed by a matching plurality of locking pins  44 . When assembled, pin springs  42  are recessed in blind holes  40   b , and locking pins  44  slightly protrude from face  40   c . Lock shaft  50  has an enlarged portion with a matching plurality of through holes  50   b  for receiving a matching plurality of push pins  52 . Unlike locking pins  44 , which are preferably of equal length, push pins  52  are of varying lengths for cooperation with recesses  70 b of key  70  as will be described below. For the sake of clarity, only one each of pin springs  42 , locking pins  44 , and push pins  52  are shown in FIG.  10 . End  50   g  of lock shaft  50  has a groove  50   d  for cooperation with key  70  as will be described below. A generally cylindrical lock housing  60  fits over lock shaft  50  and spring keeper cylinder  40 . Lock housing  60  has a tapped hole  60   g  for receiving a set screw  64 . The outer end of lock housing  60  has a hole  60   a  with a slot  60   d  for receiving key  70 . Holes  60   c  in lock housing GO receive stop pins  62  and  63  which limit rotation of key  70  as described below. 
     When rifle sighting apparatus  100  is assembled, spring keeper cylinder  40  abuts face  30   b  of mounting plate  30 , portion  50   a  of lock shaft  50  extends through hole  30   a  of mounting plate  30 , portion  50   e  of lock shaft  50  resides inside hole  40   a  of spring keeper cylinder  40 , and base  60   b  of lock housing  60  abuts face  30   b  of mounting plate  30 . Lock housing  60  is secured to mounting plate  30  by inserting screws  32  through holes  30   e  and into tapped holes  60   e  (shown in FIG. 12) in base  60   b  of lock housing  60 . Edge  50   f  of lock pin  50  abuts ridge  60   f  (shown in FIG. 13) of lock housing  60 . Cam  26  is fastened to lock shaft  50  by installing screw  24  into a tapped hole (not shown) in the end of portion  50   a . Set screw  64  engages outer surface  40   d  of spring keeper cylinder  40  and thereby immobilizes spring keeper cylinder  40 . But for the action of locking pins  44  as described below, lock shaft  50  is rotatable with respect to spring keeper cylinder  40 . In the locked position, groove  50   d  of lock shaft  50  is aligned with slot  60   d  of lock housing  60 , as shown in FIG. 12, and pin springs  42  cause locking pins  44  to protrude slightly into holes  50   b  of lock shaft  50 , which prevents lock shaft  50  from rotating. Cam  26 , which is fastened to lock shaft  50 , is positioned adjacent the rifle trigger (not shown) in the unfired position as discussed above in connection with FIGS. 3-6. Push pins  52 , which abut locking pins  44  inside holes  50   b  of lock shaft  50 , protrude outwardly from holes  50   b  in varying amounts because of their varying lengths. As illustrated in FIG. 12, push pins  52  are partially visible through the annulus formed between portion  50   g  of lock shaft  50  and the edge of hole  60   a  in lock housing  60 . Referring to FIGS. 12 and 13, surface  50   g  of lock shaft  50  is generally flush with surface  60   h  of lock housing  60 . 
     To rotate lock shaft  50  and thereby rotate cam  26  into engagement with the rifle trigger in order to fire the rifle, a proper key  70  is required. As shown in FIGS. 10 and 11, key  70  has a handle  70   f  attached to a key cylinder  70   e . Key cylinder  70   e  has a plurality of recesses  70   b  formed in its outer surface at its leading edge, and recesses  70   b  are bounded by shoulders  70   d . The lengths of recesses  70   b  are respectively selected to mate with push pins  52 . An inner nub  70   c  protrudes inwardly from key cylinder  70   e , and an outer nub  70   a  protrudes outwardly from key cylinder  70   e . To insert key  70  into lock housing  60 , nubs  70   a  and  70   c  are aligned with slot  60   d  and groove  50   d , respectively, and key cylinder  70   e  is inserted through hole  60   a  and over portion  50   g  of lock shaft  50 . As key  70  is inserted, shoulders  70   d  eventually engage push pins  52 , which abut locking pins  44 , which in turn are biased toward push pins  52  by pin springs  42 . Upon further insertion of key  70 , shoulders  70   d  depress push pins  52  which in turn depress locking pins  44  by compressing pin springs  42 . Edge  50   c  of lock shaft  50  abuts edge  40   c  of spring keeper cylinder  40  to form a shear plane. If recesses  70   b  properly match push pins  52 , the interfaces of push pins  52  with locking pins  44  eventually will simultaneously arrive at the shear plane. At that point, locking pins  44  are no longer protruding into holes  50   b , and lock shaft  50  is then free to rotate relative to spring keeper cylinder  40 , except as limited by stop pins  62  and  63  which engage outer nub  70   a  of key  70 . As key  70  is rotated, inner nub  70   c  of key  70  engages groove  50   d  of lock shaft  50  and thereby rotates lock shaft  50 , which in turn rotates cam  26  into engagement with the rifle trigger to depress the trigger to the firing position. In the embodiment shown in FIG. 12, which is designed for clockwise rotation of lock shaft  50 , stop pin  62  prevents counterclockwise rotation of key  70 , and stop pin  63  limits the degree of clockwise rotation to that which is necessary to rotate cam  26  sufficiently to depress the rifle trigger to the firing position. Stop pins  62  and  63  could be placed in different locations to allow counterclockwise rotation or a different degree of rotation, whether clockwise or counterclockwise, depending on the particular cam design and the desired direction of rotation. As with the other embodiments discussed above, sighting apparatus  100  substantially eliminates jerking of the trigger because any speed of manual rotation of key  70  results in a smooth rearward displacement of the trigger. 
     The lock and key apparatus described above and illustrated in FIGS. 10-13 is preferably made from a conventional cam lock such as those available from Fort Lock Corp., 3000 N. River Rd., River Grove, Ill. 60171. However, persons skilled in the art will recognize that other suitable locks and keys may also be used, with the objective being to provide a device to which the cam may be attached that will not rotate unless actuated with a proper key. It will also be apparent that the lock and key apparatus could be installed on either side of the rifle, as desired, for either a right-handed user or a left-handed user. Additionally, it will be apparent to those skilled in the art that the cam may have any desired number of slots for receiving end  28   a  of spring  28  in order to provide the desired amount of torsional resistance and degree of cam rotation required to fire the rifle, depending on the particular trigger configuration and the preference of the user. For example, FIG. 14 illustrates a cam  80  having eight slots  80   a  through  80   h . In cooperation with slots  30   c  and  30   d  on mounting plate  30 , slots  80   a  through  80   h  provide sixteen different positions for cam  80 . Similarly, mounting plate  30  may have any desirable number of slots for receiving end  28   b  of spring  28  to increase the adjustability of the cam. The same is true for the other embodiments disclosed herein. 
     FIG. 15 illustrates yet another embodiment  200  of this invention. Rather than a pair of plates for engaging the sides of the trigger guard TG, embodiment  200  comprises a mounting body  210  that is adapted for insertion into trigger guard TG. Mounting body  210  comprises a generally planar mounting plate  212  from which one or more plug portions  214  and  216  extend. Plug portions  214  and  216 , which are preferably made from a resilient material, are shaped to mate with the interior surface of trigger guard TG and are preferably slightly larger than the opening of trigger guard TG such that the edges  218  of plug portions  214  and  216  snugly engage the interior surface of trigger guard TG. Edges  218  of plug portions  214  and  216  may be beveled to help hold mounting body  210  in place. Mounting body  210  has a hole  220  for mounting a trigger actuating shaft  6 , the outer end of which preferably has a manually operable knob  7 . The inwardly projecting end of actuating shaft  6  mounts a cam  26  with screw  24  which screws into a tapped hole in the inwardly projecting end of shaft  6 . Spring  28  is mounted on shaft  6  between cam  26  and mounting body  210 , which has one or more slots  222   a  and  222   b  adjacent hole  220  for receiving end  28   b  of spring  28 . End  28   a  of spring  28  engages a slot on cam  26  as discussed above in connection with FIGS. 5-9. When installed, cam  26  is positioned closely adjacent trigger T in its inactive or nonfiring (neutral) position. As discussed above, rotation of shaft  6  using knob  7  causes cam  26  to effect a gradual rearward displacement of trigger T to its firing position. Once again, this embodiment substantially eliminates jerking of trigger T because any speed of manual rotation of knob  7  still results in a smooth rearward displacement of trigger T. Of course, embodiment  200  may be made for either a right-handed or a left-handed user. 
     FIG. 16 illustrates still another embodiment  300  of this invention which clamps to the trigger guard TG. Clamp  310  comprises a mounting plate  312  having a hole  320  for rotatably mounting a trigger actuating shaft  6 , which preferably has a knob  7  on its outer end. Clamp  310  preferably has a pair of clamping plates  314  and  316  for sandwiching the bottom portion TG b  of trigger guard TG. Clamp  310  is preferably installed on the bottom portion TG b  of trigger guard TG because that portion is generally planar. However, clamp  310  may be provided with suitable clamping plates that are specially adapted for clamping to other portions of trigger guard TG, if desired. Alternatively, one or more holes may be drilled and tapped in trigger guard TG and a single clamping plate with matching holes may be secured to trigger guard TG with one or more screws. After clamping plates  314  and  316  are installed on a suitable portion of trigger guard TG, a screw  324  is installed into holes  318  and  319  of clamping plates  314  and  316  to securely fasten clamp  310  to trigger guard TG. Spring  28  and cam  26  are installed on shaft  6  using screw  24 . Mounting plate  312  has one or more slots  322   a  and  322   b  adjacent hole  320  for receiving end  28   b  of spring  28 . End  28   a  of spring  28  engages a slot on cam  26  as discussed above in connection with FIGS. 5-9. As with other embodiments discussed above, cam  26  is positioned closely adjacent trigger T in the neutral position. As discussed above, rotation of shaft  6  using knob  7  causes cam  26  to effect a gradual rearward displacement of trigger T to its firing position. Once again, this device substantially eliminates jerking of trigger T because any speed of manual rotation of knob  7  still results in a smooth rearward displacement of trigger T. Embodiment  300  may be made for either a right-handed or a left-handed user. 
     Although the foregoing specific details describe preferred embodiments of this invention, persons reasonably skilled in the art will recognize that various changes may be made in the details of the apparatus of this invention without departing from the spirit and scope of the invention as defined in the appended claims. Therefore, it should be understood that this invention is not to be limited to the specific details shown and described herein.