Abstract:
A dry fire prevention safety mechanism for crossbows having a trigger mechanism which releases a bowstring to discharge an arrow. A spring-loaded catch arm is pivotally connected to the crossbow and has a hook at one end and a ramp portion at the opposite end which extends into an arrow seating well. When an arrow is positioned to be discharged, the ramp portion is abutted by the arrow which disengages the hook from the trigger and enables operation of the crossbow.

Description:
BACKGROUND OF THE INVENTION 
     The field of the invention pertains to crossbows and crossbow trigger mechanisms. The invention relates more particularly to an anti-dry fire mechanism for crossbows, wherein an arrow contacting surface operates a hook-type catch to engage and prevent operation of a trigger mechanism. 
     Various types of trigger mechanisms have been specifically developed for use in crossbows. Many, if not most, of these crossbow trigger mechanisms are designed with built-in safety mechanisms which prevent accidental discharge of an arrow. However, these conventional safety mechanisms are typically not designed for preventing the release of a cocked but unloaded bowstring, i.e. when an arrow is not positioned for discharge. This situation, commonly known as “dry fire”, can cause damage to the crossbow or be potentially hazardous to the user. In an effort to prevent the occurrence of dry fire situations, various dry fire prevention devices have been developed for crossbows which disable operation of the crossbow trigger mechanism while an arrow is not positioned to be discharged. 
     For example, in U.S. Pat. No. 5,085,200 a self-actuating, dry-fire prevention safety device for a crossbow is shown having a stop block  30  which pivotally operates to block forward movement of a safety assembly block plate  22  when an arrow is not positioned to be discharged. It does so by abutting a blocking portion  34  of the stop block  30  against a rounded operating pin  24  of the safety assembly block plate  22 . The disadvantage of this arrangement is the limited efficacy and unreliability of a blocking impedance as opposed to impedance by catch-engagement. While exact alignment of the blocking component  34  with the operating pin  24  would effectively prevent dry fire (FIG.  5 ), the slightest variation in pivot angle of the stop block  30  may cause the blocking engagement to slip and thereby enable dry fire. 
     And in U.S. Pat. No. 5,598,829 a crossbow dry fire prevention device is shown having a string catch member with an arrow contacting surface which cause the string catch member to be moved out of the string catching position when an arrow is placed in the firing position. When the bowstring is cocked but an arrow is not in place, the string catch member is urged into the release path of the bowstring. In this manner, the string catch member functions to catch the inadvertently released bowstring to prevent dry fire. However, this arrangement does not operate to inhibit operation of the trigger mechanism. Notwithstanding the absence of an arrow, actuation of the trigger mechanism will release the cocked bowstring from the sear, only to be caught by the string catching member. 
     Similar to the 839 patent, a crossbow is shown in U.S. Pat. No. 5,884,614 also having a dry fire prevention mechanism which operates to block the release passage of a bowstring when an arrow is not in place. In particular, a safety latch positioned above the release passage is urged downward into the release passage by means of a safety latch spring. This arrangement, however, also does not inhibit operation of the trigger mechanism. While inadvertent release of the unloaded bowstring will not dry fire, the bowstring must be cocked again and reset onto the sear before successful operation may take place. 
     In summary, it is therefore desirable to provide a dry fire prevention safety mechanism for use on crossbows which not only blocks movement of the trigger mechanism, but directly catches a part of the trigger mechanism to prevent operation of the crossbow trigger mechanism when no arrow is positioned for discharge. Moreover, a dry fire prevention mechanism having a minimal number of moving parts, e.g. a single moving arm, would provide simplified operation, as well as reduce manufacturing costs compared to complex, multi-link dry fire prevention safety systems. 
     BRIEF SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a reliable dry fire prevention mechanism for crossbows wherein the crossbow trigger mechanism is made inoperable while an arrow is not positioned for discharge. 
     It is a further object of the present invention to provide a simple and efficient dry fire mechanism for crossbows having a one-piece catch arm which directly catch-engages the trigger without any wasted movement or the need for additional links or intermediate components. 
     It is a still further object of the present invention to provide a dry fire mechanism for crossbows which may be manufactured in a cost-effective manner by conventional manufacturing methods. 
     The present invention is for a safety mechanism for preventing dry fire of a crossbow. The crossbow is of the type having a bow mounted on a crossbow stock and a trigger mechanism which releases a bowstring to discharge an arrow. The safety mechanism comprises a catch arm which is pivotally connected to the crossbow stock. The catch arm has a first catch element, such as a hook, at one end for releasably engaging a second catch element, such as a catch pin, of the trigger mechanism. Additionally, the catch arm has an arrow contacting surface which pivots the first catch element out of engagement with the second catch element when an arrow is positioned to be discharged. And finally the safety mechanism comprises resiliently biasing means for urging the first catch element to releasably engage the second catch element of the trigger mechanism when no arrow is positioned to be discharged, thereby preventing dry fire while an arrow is not in place. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a crossbow of the present invention. 
     FIG. 2 is a top view of the crossbow in FIG. 1, illustrating deflection of the bow and bowstring when in a cocked position. 
     FIG. 3A is a schematic view of the crossbow stock upon cocking and releasably locking the nocking member and bowstring, but prior to loading of an arrow. 
     FIG. 3B is an enlarged view of Circle  3 B in FIG. 3A showing in detail the engagement of the primary safety mechanism. 
     FIG. 4A is a schematic view of the crossbow stock following FIG. 3A wherein an arrow is now loaded, and the safety device is disengaged. 
     FIG. 4B is an enlarged view of Circle  4 B in FIG. 4A showing in detail the disengagement of the primary safety mechanism, and closure of the electrical circuit. 
     FIG. 5 is a schematic view of the crossbow stock following FIG. 4A, wherein the trigger mechanism is actuated, the bowstring and nocking member released, and the arrow discharged. 
     FIG. 6A is a cross-sectional view of the bowstring release mechanism taken along line  6 A of FIG. 3A, and shown in the closed position. 
     FIG. 6B is a cross-sectional view of the bowstring release mechanism following FIG. 6A, and shown in the open position to release the nocking member and bowstring. 
     FIG. 7 is an enlarged perspective view of the slider component of the safety mechanism. 
     FIG. 8 is a partially cut-away schematic view of the crossbow stock illustrating the electric circuit for the laser. 
     FIG. 9 is a skeletal schematic view of a second preferred embodiment of the crossbow, having a rifle configuration. 
     FIG. 10 is a detailed view of the rifle type crossbow of FIG. 9, shown in a closed position with a cocked nocking member positioned to be discharged. 
     FIG. 11 is a detailed view of the rifle type crossbow following FIG. 10, shown in the open position after discharging an arrow. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, FIGS. 1-8 show a first preferred embodiment of a crossbow having a hand-held pistol type configuration, generally indicated at reference character  10 . The crossbow  10  is designed to receive, engage, and discharge an arrow, generally indicated at reference character  24 , having a leading end  25  and a tail end  26  with a nock portion  27 . As can be seen in FIGS. 1 and 2, the crossbow  10  includes a bow, generally indicated at reference character  11 , which is mounted on a crossbow stock, generally indicated at reference character  17 . In particular, a riser portion  12  of the bow  11  is mounted at a forward portion  19  of a barrel  18  of the crossbow stock  17 . A rearward portion  20  of the barrel  18  is connected to a handle portion  21  of the crossbow stock  17  which is used for grasping and handling of the crossbow  10 . The bow  11  has a pair of bow limbs  13  connected at their distal ends by a bowstring  14 . A nocking member  15  is centrally mounted on the bowstring  14  for engaging the nock portion  27  of an arrow  24 . In this regard, the nock portion  27  has a recess  28  (FIGS. 3A,  4 A, and  5 ) suitably adapted to releasably engage the nocking member  15 , as will be discussed in detail below. 
     One important feature of the crossbow  10  is a bowstring release mechanism and system, shown in FIGS. 3-6B, which operates to hold and release the bowstring  14  by way of the nocking member  15 . The bowstring release mechanism and system is generally comprised of upper and lower catch surfaces,  64  and  64 ′ respectively (see FIGS.  6 A and  6 B), positioned at the rearward portion  20  of the crossbow stock  17  in vertical relation to each other. A release passage  82  is formed between the catch surfaces  64 ,  64 ′. The release passage  82  leads into a retaining area  82 ′ where a cocked nocking member  15  (along with the bowstring  14 ) is held prior to being discharged through the release passage  82 . Preferably, the upper and lower catch surfaces  64 ,  64 ′ are the curvilinear contact surfaces of upper and lower rollers  60 ,  62  which are adapted to spin freely about rotational axes  61 ,  63  respectively. The upper end lower catch surfaces  64 ,  64 ′ are thus preferably continuous rolling surfaces having circular cross-sections as shown in FIGS. 3A,  4 A, and  5 . Alternatively, however, it is appreciated that the upper and lower catch surfaces  64 ,  64 ′ may be rigidly fixed to prevent any movement, rotational or otherwise. 
     Furthermore, as can be seen in FIGS. 6A and 6B showing a cross-sectional view taken along line  6 A of FIG. 3A, each of the upper and lower rollers  60 ,  62  has a substantially hourglass configuration with a hyperbolic cross-section, i.e. the center portion has a narrower width than the opposing ends. Thus the upper catch surface  64  of the upper roller  60  and the adjacent lower catch surface  64 ′ of the lower roller  62  are concave relative to each other when viewed along a longitudinal axis (not shown) of the barrel  18 . Moreover, the concave configuration of each of the catch surfaces  64 ,  64 ′ is adapted to contour to the particular shape of the nocking member  15 . As shown in the figures, the nocking member  15  preferably has a substantially ball-shaped configuration with a bore  16  through which the bowstring  14  extends. Thus the recess  28  of the nock portion  27  of an arrow  24  has a semi-spherically concave configuration which seats the ball-shaped nocking member  15 . Alternatively, however, it is appreciated that the nocking member  15  may also have various non-spherical, curvilinear shapes, with correspondingly contoured upper catch surface, lower catch surface, and nocking portion recess  28 . 
     Additionally, the bowstring release mechanism and system comprises actuating means for vertically moving the upper and lower catch surfaces  64 ,  64 ′ relative to each other between a closed position (FIGS.  3 A and  4 A), and an open position (FIG.  5 ), thereby narrowing or widening the release passage  82 , respectively. Preferably, as can be seen in the figures, the upper catch surface  64  (of the upper roller  60 ) is mounted on a front limb  42  of a sear arm  41  which is pivotally connected to the crossbow stock  17  at a sear arm pivot joint  44 . As can be seen in the figures, the upper catch surface  64  is preferably positioned away from the tip of the front limb  42 , to enable a abutment surface  45  to clamp down an inserted arrow  24  by pressing it against an opposite brace surface connected to the crossbow stock  17 . The sear arm pivot joint  44  is positioned between the front limb  42  and a rear limb  43  extending opposite the front limb  42  of the sear arm  41 . The sear arm  41  is thus configured to rock about the sear arm pivot joint  44  by applying an upward locking force or an opposite downward unlocking force on the rear limb  43 . 
     To produce the upward locking and downward unlocking forces which actuate the sear arm  31 , the rear limb  43  is pivotally connected to a coupler link  36  at a rear pivot joint  37 . The coupler link  36  is in turn pivotally connected to a trigger link  33  at an upper trigger link joint  35 , and the trigger link  33  is pivotally connected to the crossbow stock  17  at a lower trigger link pivot joint  34 . Furthermore, a resiliently biasing means, such as a coil spring  46 , is positioned above the rear limb  43  which exerts the downward unlocking force against the rear limb  43 . It is notable that due to the downward unlocking force exerted by the coil spring  46  on the rear limb  43  of the sear arm  41 , alignment of the upper trigger link pivot joint  35  along the alignment axis  47  is inherently unstable, with the upper trigger link pivot joint  35  having a tendency to push away from the axis  47 . It is further notable that because the rear pivot joint  37  and upper trigger link pivot joint  35  are not pivotally connected to the crossbow stock  17 , these joints are capable of being translationally displaced relative to the crossbow stock  17 . 
     In this manner, the relative position of the upper trigger link pivot joint  35  with respect to the alignment axis  47  will ultimately determine the open or closed positioning of the sear arm  31 . The rear limb  43  of the sear arm  41  will reach its highest point when the upper trigger link pivot joint  35  is collinear with the rear pivot joint  37  and the lower trigger link pivot joint  34  along an alignment axis  47 . And consequently, the front limb  42  of the sear arm  41 , together with the upper catch surface  64 , will be simultaneously lowered to the closed position, as shown in FIG.  4 A. In providing the upward locking force necessary to pivot the sear arm  31  to the closed position, a pressure plate  38  is connected to the coupler link  36  for actuating the coupler link  36 . By pushing against the pressure plate  38 , the trigger link  33  pivots about the lower trigger link pivot joint  34  such that the upper trigger link pivot joint  35  crosses the alignment axis  47 . This consequently raises pivot point  37  of the coupler link  33 . As can be seen in FIG. 4A when in the ready position, the upper trigger link pivot joint  35  is positioned slightly forward of the alignment axis  47  and is stabilized and prevented from further movement by means of a trigger  29  which abuts the trigger link  33  along an abutting end  32 . 
     Once in the releasably locked position, actuation of the trigger  29  causes the abutting end  32  to urge the trigger link  33  rearward past the alignment axis  47 . As the upper trigger link pivot joint  35  moves rearward past the alignment axis  47 , the compressed sear arm spring  46  provides the necessary momentum to accelerate the upper trigger link far past the alignment axis  47 . This movement lowers the rear limb  43  of the sear arm  41  and consequently raises the front limb  42 . 
     Generally, when the upper and lower rollers  60 ,  62  are in the closed position, as shown in FIG. 6A, the upper and lower catch surfaces  64 ,  64 ′ block passage of a cocked nocking member  15  through the release passage  82 . They do so by abutting a frontal portion of the cocked nocking member  15  to keep it contained within the retaining area  82 ′. It is notable that because only the forward section of the ball-shaped nocking member  15  abuts against the catch surfaces, the nocking member  15  is not seized by the upper and lower catch surfaces  64 ,  64 ′. It is appreciated that the term “blocking” is defined and used herein to mean preventing movement in one or more predetermined directions, whereas the term “seizing” is defined and used herein as preventing movement in all directions by a pair of equal and opposite forces, i.e. complete relative immobility with respect to the seizing instrument or object. 
     When in the open position, as shown in FIG. 6B, the upper and lower catch surfaces  64 ,  64 ′ are sufficiently separated to enable the cock nocking member  15  to pass through the release passage  82 . As can be seen in the figures, the use of upper and lower rollers  60 ,  62  minimizes or altogether eliminates slip between the nocking member  15  and the rolling catch surfaces  64 ,  64 ′. Alternatively, however, where the catch surfaces  64 ,  64 ′ are rigidly fixed to the crossbow stock  17 , the nocking member  15  must pass through the release passage  82  by sliding against the catch surfaces  64 ,  64 ′. It is appreciated that wear caused by slip friction between the surfaces is effectively reduced for repeated use cycles due to the curved and contoured catch surfaces  64 ,  64 ′ which provide relatively even pressure distribution along the contact and separation points between the nocking member  15  and the catch surfaces  64 ,  64 ′. In this manner, the ball-shaped nocking member  15  may separate smoothly and evenly from the catch surfaces  64 ,  64 ′ to propel the arrow  24  much more accurately. 
     Another important feature of the crossbow  10  is a dry fire prevention mechanism which operates to disable operation of the trigger  29  while an arrow  24  is not positioned to be discharged. As can be seen in the figures, the dry fire prevention mechanism is preferably a catch arm  65  which is pivotally connected to the crossbow stock  17  at a catch arm pivot joint  66 . The catch arm  65  has a top end  67  adjacent the lower roller  62  and a bottom end  68  having a first catch element  69  which is preferably a hook  69 . The catch arm pivot joint  66  is preferably intermediately positioned between the top and bottom ends  67 ,  68 . Resiliently biasing means  71 , such as a coil spring  71 , is provided to urge the hook  69  of the catch arm  65  into releasable engagement with a second catch element  31  of the trigger mechanism  29  when no arrow  24  is positioned to be discharged. As shown in the figures, the second catch element is preferably a catch pin  31 . Furthermore, an arrow contacting surface  70  is located at the top end  67  of the catch arm  65 , which is preferably positively inclined towards the rear of the crossbow  10 . 
     Operation of the dry fire prevention mechanism can be best seen in FIGS. 3A,  4 A, and  5  which illustrate the progression of loading and firing an arrow  24 . Prior to insertion of the arrow  24 , the catch arm  65  preferably abuts against a stopper block  72  and the hook  69  is releasably engaged to catch pin  31  such that the trigger mechanism  29  may not be actuated and the crossbow  10  is non-operational. As can be seen in FIG. 4A upon the insertion of an arrow  24  adjacent the abutment surface  45 , the tail end  26  of arrow  24  presses against the arrow contacting surface  70  to thereby pivot the catch arm  65  about catch arm pivot pin  66 . Consequently, the resulting pivoting action of the catch arm  65  is sufficient to disengage and clear the hook  69  from the pin  31 . As can be seen in FIG. 5, upon release of the nocking member  15 , the arrow contacting surface  70  returns to its unpivoted position and the catch arm  65  once again abuts the stopper block  72 . Furthermore, as can be seen in FIGS. 3A,  4 A,  5 , the catch arm  65  has means for manually overriding engagement of the first and second catch elements. This is preferably an override actuator arm  68 ′ transversely extending from the catch arm  65  and accessible by the user. 
     A third important feature of the crossbow  10  is a laser circuit activation system which utilizes a safety component of the trigger mechanism  29  to activate a laser generating means, generally indicated by reference character  73 . FIG. 8 generally shows a schematic view of an electrical circuit of the laser generating means  73 , generally indicated by reference character  74 . The electrical circuit  74  comprises an energy source, such as a battery  75 , connected by electrical wiring  76  to a primary switch  77  positioned adjacent a trigger safety device. The trigger safety device comprises a slider component  48  best shown in FIG.  7 . The slider component  48  has a reset shoe  53  connected to a reset extension arm  54 . And the reset extension arm  54  is connected to a cam  51  having a reversed incline surface  52 . The cam  51  connects to a thumb switch  49  by means of a neck  50 . As shown in FIG. 7, the slider component  48  is seated along a planer slide surface  22  of a top end of the handle portion  21 . Furthermore, the trigger safety device has a leaf spring  55  having a fixed end  56  and a movable end  57 . A latch portion is connected to the movable end  57  which engages a safety aperture  39  located on the pressure plate  38  to releasably lock the trigger mechanism  29 . 
     As shown in FIGS. 3B and 4B, the trigger safety device may be disengaged when the thumb switch  49  is urged forward such that the reverse inclined surface  52  contacts and steps over step surface  59  of the leaf spring  55 . This causes the leaf spring  55  to bias sufficiently downward such that the latch portion  58  is disengaged from the safety aperture  39 . Consequently, and simultaneously, the movable end  57  of the leaf spring  55  depresses a switch actuator arm  80  of the primary switch  77 . This action bridges the positive terminal  78  with a negative terminal  79  to complete the electrical circuit  74  of the laser generating means  73 . 
     In this manner, when the safety device is disengaged to enable discharge of an arrow  24 , the laser means  73  is simultaneously activated to produce a laser beam (not shown). And upon discharging the arrow  24  from the crossbow  10 , the pivoting movement of the trigger link  33  causes the trigger link  33  to abuttingly urge the reset shoe  53  rearward. This in turn moves the slider component  48  back to the safety position which releases the leaf spring  55  and automatically resets the safety device to prevent accidental discharge. Consequently, the leaf spring  55  also releases the switch actuator arm  80  to thereby open the electrical circuit  74  and turn off the laser  73 . This helps conserve energy needed to power the laser means  73  by supplying power only immediately prior to discharging the crossbow  10 , i.e. when the safety is disengaged. Furthermore, a secondary switch  81  may be provided as a manual override for turning the laser  73  on and off. 
     A second preferred embodiment of the cross bow is shown in FIGS. 9-11, having a crossbow stock with a rifle-type configuration, generally indicated by reference character  100 . Similar to the pistol-type crossbow  10  of the first preferred embodiment, the rifle crossbow stock  100  has an elongated barrel  101  with a front portion  102  and a rear portion  103 . Additionally, a shoulder rest  105  extends to the rear of the handle portion  104 . 
     As can be best seen in FIG. 10, the rifle crossbow stock  100  also preferably incorporates a bowstring release mechanism and system having an upper roller  127  and a lower roller  129 . Upper roller  127  is also rotatably connected to a sear arm  120  having a front portion  121  and an oppositely directed rear portion  122 , with a sear arm  120  pivoting about a sear arm pivot axis  123 . While the trigger mechanism shown in FIG. 10 differs from that of the pistol-type crossbow  10  in FIGS. 1-8, the bowstring release mechanism and system operate in essentially the same manner. Likewise, the rifle-type crossbow  100  also has a safety mechanism for preventing dry fire which utilizes a catch arm  131  pivotally connected at a catch arm pivot joint  132  to the crossbow stock  100 . An arrow contacting surface  137  similarly extends from a top end of the catch arm  131  into the path of an arrow for pivoting the catch arm  131  about the catch arm pivot joint  132 . And the catch arm  131  has a hook  136  which engages a catch pin  108  of the trigger mechanism  106 . In this embodiment, however, the engagement pin  108  is a pivoting joint between a cocking lever  115 , having an upper end  116  and a pivot axis  117 , and a connecting safety arm  119 . In this second embodiment, the safety arm  119  has an analogous function to the pressure plate  38  of the first preferred embodiment. Thus, the safety arm  119  connects to a pivot joint  112  connecting to a coupler link  113  and a trigger link  110 . The trigger link  113  is pivotally connected to the rear limb  122  of the sear arm  120  at a rear pivot joint  114 . Similar to the alignment axis  47  of the first preferred embodiment, the alignment axis  126  of the second preferred embodiment is the equilibrium threshold which must be overcome to cross between the open and closed positions. 
     The present embodiments of this invention are thus to be considered in all respects as illustrative and restrictive; the scope of the invention being indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.