Patent Publication Number: US-9404701-B2

Title: Trigger assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 14/348,760, filed Mar. 31, 2014, the content of which is incorporated fully herein by reference. 
    
    
     FIELD 
     The present invention relates to a trigger assembly for activating a firing mechanism. 
     BACKGROUND 
     Many known devices include a firing mechanism activatable by movement of a trigger. The devices are typically for firing or launching a projectile. Typically, the trigger is moved by imposing a trigger pull load on the trigger, to cause the trigger to move from a loaded position, at which the firing mechanism is activatable, to a released position, at which the firing mechanism is activated. Activation of the firing mechanism is conventionally effected in various ways, e.g., via release of an element of the firing mechanism, or otherwise initiating movement of an element of the firing mechanism. As is well known in the art, for various reasons, it is desirable that the trigger pull load be predictable, i.e., consistent for the user. For instance, the device can be more accurately aimed upon firing if the trigger pull load is consistent for the user. Also, in general, a trigger that requires a more consistent trigger pull load is more safely operated. 
     There are competing factors to be taken into account in determining the trigger pull load required to move the trigger. If the trigger pull load required is relatively large, then an inadvertent activation of the firing mechanism is unlikely. However, it is also desirable that the trigger pull load be relatively small, to make activating the firing mechanism relatively easy. This is generally thought to be desirable because if facilitates maintaining an accurate aim of the device when the trigger is pulled. 
     Those skilled in the art would be aware of various devices including firing mechanisms activatable by movement of a trigger. One example of a device including a firing mechanism activatable by a trigger is a crossbow, i.e., a high-powered weapon designed to shoot arrows (or bolts) at a target. As is well known in the art, the crossbow may include, for example, a stock with a bow mounted transversely on it. A bowstring across the bow is pulled taut, and the bolt is positioned to be propelled by the bowstring upon the bowstring&#39;s release. Typically, the taut bowstring is held in a cocked position by the firing mechanism, which is activatable by moving the trigger in a trigger mechanism to the released position thereof. However, the typical trigger mechanism has a number of deficiencies. 
     Typical draw forces for a crossbow vary from 100 to 250 lbs. As is well known in the art, it is desirable that such high loads should be dealt with by the trigger mechanism at relatively low trigger efforts (i.e., relatively low trigger pull loads), for shooting accuracy. However, known triggers rely on friction between the ticker (or trigger) and sear surfaces and as a result they have relatively high trigger pull efforts or loads, e.g., in the range of approximately 2.5 lbs. to approximately 9 lbs. (approximately 1.134 kg. to approximately 4.082 kg.). 
     In the prior art, to lower the coefficient of friction, certain techniques are employed (e.g., ticker and sear surfaces are polished, and/or lubrication is applied) in order to mitigate the relatively high trigger pull efforts. However, at best, the coefficient of friction is not lower than 0.1 in the conventional trigger mechanism. Even with those low values, however, the effort (load) required for trigger pull typically is not less than 2.5 lbs. (approximately 1.134 kg.). 
     Some manufacturers have attempted to use leverage (i.e., by changing the geometry of the conventional trigger mechanism) to lower forces between ticker and sear, but trigger effort still remains relatively high in the prior art. Also, in the prior art, the trigger pull effort can be inconsistent (i.e., unpredictable) due to wear of the polished surfaces, poor lubrication, or lack of lubricant. 
     As is well known in the art, similar issues concerning the desirability of decreasing the trigger pull effort and the predictability of the trigger pull effort required for activation of the firing mechanism are raised in connection with other devices including firing mechanisms that are activated by pulling the trigger, e.g., firearms. 
     SUMMARY 
     For the foregoing reasons, there is a need for a trigger assembly that overcomes or mitigates one or more of the deficiencies of the prior art. 
     In its broad aspect, the invention provides a trigger assembly for activating a firing mechanism. The trigger assembly is mountable in a housing. The trigger assembly includes a trigger pivotally mounted on a trigger pivot pin, the trigger including an elongate trigger arm extending between a top end proximal to the trigger pivot pin and a bottom end distal to the trigger pivot pin and a sear arm positioned transverse to the trigger arm, the sear arm having a first sear surface. The trigger assembly also includes a firing element pivotably mounted on a firing element pivot pin, the firing element including a body portion having a second sear surface, and an engagement portion for engagement with at least, a portion of the firing mechanism, for activating the firing mechanism. A guide is connected to one of the sear arm or the firing element. The guide defines a pair of apertures adjacent to one of the first and second sear surfaces. In addition, the trigger assembly includes a captured roller positioned for engagement with the first and second sear surfaces. The captured roller at least partially positioned in the pair of apertures of the guide. The trigger is pivotable about the trigger pivot pin between a load position, in which the captured roller is held between the first and second sear surfaces, and a release position, in which the second sear surface is disengaged from the captured roller and the firing element is released. The firing element is pivotable about the firing element pivot pin between a first position, in which the firing element is held by the engagement of the second sear surface with the captured roller when the trigger is in the load position thereof and the siring mechanism is activatable by the engagement portion, and a second position, in which the firing element is disengaged from the captured roller and the firing mechanism is activated by the engagement portion, the firing element being movable to the second position upon the trigger moving to the release position thereof. 
     In another aspect, the captured roller is elongate and at least partially defines a central axis thereof. The captured roller is mounted in the housing for rotation of the captured roller about the central axis and for movement of the captured roller substantially transverse to the central axis as the trigger moves from the load position to the release position to provide substantially consistent frictional resistance to movement of the first and second sear surfaces relative to each other. In particular, the captured roller provides roiling frictional resistance to movement of the first and second sear surfaces relative to each other. 
     In another aspect, the first and second sear surfaces cooperate to permit the trigger to be movable from the load position toward the release position upon application of a first trigger pull load on the trigger until the trigger reaches a transition position, and the first and second sear surfaces cooperate to permit the trigger to be movable from the transition position toward the release position upon application of a second trigger pull load on the trigger. 
     In yet another aspect, the second trigger pull load exceeds the first trigger pull load, to hinder or impede activation of the firing mechanism. 
     In another of its aspects, the invention provides a trigger assembly for mounting in a housing in a crossbow, the housing having an opening at a forward side thereof in which a bowstring is at least partially positionable in a drawn position thereof. The trigger assembly includes a trigger pivotably mounted on a trigger pivot pin supported in the housing. The trigger includes an elongate trigger arm extending between a top end proximal to the trigger pivot pin and a bottom end distal thereto, and a sear arm positioned transverse to the trigger arm, the sear arm having a first sear surface. The trigger assembly also includes a firing element pivotably mounted on a firing element pivot pin supported in the housing. The firing element includes a body portion having a second sear surface and a hook portion. In addition, the trigger assembly includes a captured roller positioned for engagement with the first and second sear surfaces. The trigger is pivotable about the trigger pivot pin between a load position, in which the captured roller is held between the first and second sear surfaces, and a release position, in which the second sear surface is disengaged from the captured roller and the firing element is released. The firing element is pivotable about the firing element pivot pin between a hooked position and an open position. In the hooked position, the firing element is held by the engagement of the second sear surface with the captured roller when the trigger is in the load position thereof and the firing mechanism is activatable by the engagement portion, the bowstring being retainable by the hook portion when the firing element is in the hooked position, in the open position the firing element is disengaged from the captured roller and the bowstring is releasable from the firing element, the firing element being movable to the open position upon the trigger moving to the release position thereof. 
     In another aspect, the captured roller is elongate and at least partially defines a central axis thereof. The captured roller is mounted in the housing for rotation of the captured roller about the central axis and for movement of the captured roller in at least one direction substantially transverse to the central axis as the trigger moves from the load position to the release position to provide substantially consistent frictional resistance to movement of the first and second sear surfaces relative to each other. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood with reference to the attached drawings, in which: 
         FIG. 1A  is an isometric view of an embodiment of a trigger assembly of the invention; 
         FIG. 1B  is an isometric view of an embodiment of a crossbow including the trigger assembly of the invention, drawn at a smaller scale; 
         FIG. 1C  is an isometric view of an embodiment of a roller of the invention, drawn at a larger scale; 
         FIG. 1D  is a cross-section of an embodiment of a housing of the invention showing the roller of  FIG. 1C  captured in a slot in the housing, drawn at a larger scale; 
         FIG. 2  is a side view of the trigger assembly of  FIG. 1A , in which a trigger is in a loaded position, and a catch is in a hooked position retaining a bowstring, drawn at a smaller scale; 
         FIG. 3  is a side view of the trigger assembly of  FIG. 1A , in which a safety element is disengaged from the trigger, permitting the trigger to move toward a released position; 
         FIG. 4  is a side view of the trigger assembly of  FIG. 1A , in which the trigger is moved further toward the released position; 
         FIG. 5  is a side view of the trigger assembly of  FIG. 1A , in which the trigger is moved further toward the released position; 
         FIG. 6  is a side view of the trigger assembly of  FIG. 1A , in which the trigger is in the released position and the catch is in the open position; 
         FIG. 7A  is a side view of the trigger assembly of  FIG. 1A , in which the trigger is in the released position and the catch is in the open position: 
         FIG. 7B  is a side view of the trigger assembly of  FIG. 1A , in which the trigger is in the released position and the catch is in the open position; 
         FIG. 8  is a side view of a portion of an embodiment of a trigger assembly of the invention, drawn at a larger scale; 
         FIG. 2  is a side view of a portion of an alternative embodiment of the trigger assembly of the invention; 
         FIG. 10A  is a side view of a portion of another alternative embodiment of the trigger assembly of the invention; 
         FIG. 10B  is a portion of the embodiment illustrated in  FIG. 10A , drawn at a larger scale; 
         FIG. 11  is a graphic representation showing trigger effort as a function of trigger rotation, for a variety of trigger assemblies; 
         FIG. 12  is a side view of another alternative embodiment of the trigger assembly of the invention, drawn at a smaller scale; 
         FIG. 13A  is an isometric view of an alternative embodiment of the trigger assembly of the invention, drawn at a smaller scale; 
         FIG. 13B  is a side view of the trigger assembly of  FIG. 13A ; 
         FIG. 13C  is a side view of the trigger assembly of  FIG. 13A , showing the trigger thereof in a load position and another, intermediate, position; 
         FIG. 13D  is a side view of the trigger assembly of  FIG. 13A  in which the trigger is in a release position; 
         FIG. 14A  is an isometric view of another alternative embodiment of the trigger assembly of the invention, drawn at a smaller scale; 
         FIG. 14B  is a side view of the trigger assembly of  FIG. 14A ; 
         FIG. 14C  is a side view of the trigger assembly of  FIG. 14A , showing the trigger thereof in a load position and another, intermediate, position; 
         FIG. 14D  is a side view of the trigger assembly of  FIG. 14A  showing the trigger in a release position; 
         FIG. 15  is an isometric view of an embodiment of a firearm of the invention including the trigger assembly of the invention, drawn at a smaller scale; 
         FIG. 16  is an isometric view of another embodiment of a trigger assembly of the invention; 
         FIG. 17  is a side view of the trigger assembly of  FIG. 16 , in which the trigger is in the released position and the catch is in the open position; and 
         FIG. 18  is a side view of the trigger assembly of  FIG. 16 , in which the trigger is in the released position and the catch is in the open position. 
     
    
    
     DETAILED DESCRIPTION 
     In the attached drawings, like reference numerals designate corresponding elements throughout. Reference is first made to  FIGS. 1A-11  to describe an embodiment, of a trigger assembly of the invention referred to generally by the reference numeral  20 . As will be described, the trigger assembly  20  is for activating a firing mechanism  22 . Preferably, the trigger assembly  20  is mountable in a housing  24 . In one embodiment, the trigger assembly  20  preferably includes a trigger  26  pivotably mounted on a trigger pivot pin  28 . It is preferred that the trigger  26  includes an elongate trigger arm  30  extending between a top end  32  proximal to the trigger pivot pin  28 , and a bottom end  34  distal to the trigger pivot pin  28 . The trigger  26  preferably also includes a sear arm  36  positioned transverse to the trigger arm  30 , the sear arm  36  having a first sear surface  38  ( FIGS. 3, 8 ). As can be seen in  FIGS. 1A and 2-7B , the trigger assembly  20  preferably also includes a firing element  40  pivotally mounted on a firing element pivot pin  42 . In one embodiment, the firing element  40  preferably includes a body portion  44  with a second sear surface  46  ( FIGS. 3, 8 ), and an engagement portion  48  for engagement with at least a portion of the firing mechanism  22 , for activating the firing mechanism  22 . It is also preferred that the trigger assembly  20  includes a captured roller  50  positioned for engagement with the first and second sear surfaces  38 ,  46 , as will also be described. Preferably, the trigger  26  is pivotable about the trigger pivot pin  28  between a load position ( FIGS. 1A, 2 ), in which the captured roller  50  is held between the first and second sear surfaces  38 ,  46 , and a release position ( FIG. 7B ), in which the second sear surface  46  is disengaged from the captured roller  50  and the firing element  40  is released, it is also preferred that the firing element  40  is pivotable about the firing element pivot pin  42  between a first position ( FIGS. 1A, 2 ), in which the firing element  40  is held by the engagement of the second sear surface  46  with the captured roller  50  when the trigger  26  is in the load position thereof and the firing mechanism  22  is activatable by the engagement portion  48 , and a second position ( FIG. 7B ), in which the firing element  40  is disengaged from the captured roller  50  and the firing mechanism  22  is activated by the engagement portion  48 , the firing element  40  being movable to the second position upon the trigger  26  moving to the release position thereof. 
     It will be understood that the housing  24  is only partially illustrated in  FIGS. 1A, 1D, and 2-7B , for clarity of illustration. Those skilled in the art would be aware that the housing  24  is designed to support the trigger assembly  20  in a body  52  of a device  54  ( FIG. 1B ). As will be described, the device  54  preferably is for firing or launching a projectile. Those skilled in the art would also be aware that the device in which the trigger assembly of the invention and the firing mechanism activated thereby are mounted may be one of various devices. As illustrated in  FIG. 1B , for example, in one embodiment, the device  54  may be a crossbow. In  FIGS. 1A  and  2 - 7 B, the bowstring  56  is the only part of the device&#39;s firing mechanism  22  that is shown. The balance of the device&#39;s firing mechanism is omitted from  FIGS. 1A and 2-7B  for clarity of illustration, in one embodiment, it is preferred that the trigger assembly  20  is mounted in the housing  24  in the crossbow  54 . The housing  24  has an opening “O” at a toward side thereof in which the bowstring  58  is at least partially positionable in a drawn position thereof, as shown in  FIG. 1A . 
     As is well known in the art, the activation of the firing mechanism may be achieved in various ways, depending on the firing mechanism. For instance, in some conventional firing mechanisms, the trigger assembly  20  activates the firing mechanism by releasing an element of the firing mechanism. An example of this is illustrated in  FIGS. 2-7B , in which a bowstring is a pert of the firing mechanism of the crossbow, and the firing mechanism of the crossbow is activated when the bowstring is released by the trigger assembly, as will be described. 
     Additional examples are provided by the conventional firing mechanisms of firearms. As is well known in the art, such firing mechanisms may be activated by release of an element of the firing mechanism, or they may alternatively be activated by striking or otherwise pushing or pulling an element of the firing mechanism. For example, the firing mechanism may include a firing pin, and the firing mechanism may be activated by an element of the trigger assembly striking an element of the firing mechanism. For example, in  FIGS. 13D and 14D , a hammer in embodiments of the trigger assembly of the invention activates the firing mechanism of a firearm by striking a firing pin thereof. 
     As can be seen in  FIGS. 1A and 2 , when the crossbow  54  is loaded, a bowstring  56  is urged in the direction indicated by arrow “A”, due to the energy stored in the bowstring  56 . The bowstring  56  preferably is restrained by the firing element  40 , when the firing element  40  is in the first position. Also, and as shown in  FIGS. 1A and 2 , when a user (not shown) wishes to release the bowstring (i.e., to launch the projectile (a bolt (not shown) engaged endwise with the bowstring  56 ), the user exerts pressure on the trigger  26  as indicated by arrow “B”, i.e., the user imposes at least a trigger pull load on the trigger  26 . For example, the user may impose the trigger pull load on the trigger via en index finger. The user moves the trigger  26  from the load position ( FIGS. 1A and 2 ) to the release position ( FIG. 7B ) by rotating the trigger  26  through a relatively small arc  58  ( FIG. 7B ) centered on the trigger pivot pin  28 , by maintaining at least the trigger pull load against or on the trigger  26  in the direction indicated by arrow “B”. When the trigger  26  has moved through the entire arc  58 , it reaches the release position ( FIG. 7B ). As will be described, once the trigger  26  reaches the release position, the firing element  40  is virtually instantaneously moved to its second position. 
     Referring to  FIGS. 2-7B , it can be seen that the firing element is pivotable about the firing element pivot pin between the first position (or the hooked position) and the second position (or the open position). When the firing element is in the hooked position ( FIGS. 1A and 2-7A ), the firing element is held by the engagement of the second sear surface with the captured roller when the trigger is in the load position thereof, and the firing mechanism is activatable by the engagement portion of the firing element. The bowstring  56  is retainable by the engagement (or hook) portion  48  when the firing element is in the hooked position, as can be seen in  FIGS. 1A and 2-7A . When the firing element is in the open position ( FIG. 7B ), the firing element is disengaged from the captured roller and the bowstring is releasable from or by the firing element. The firing element moves to the open position upon the trigger moving to the release position thereof. 
     The invention herein reduces the trigger pull load (i.e., the load required to be imposed on the trigger in the direction indicated by arrow “B” in  FIGS. 1A and 2  to move the trigger  26  from the load position to the release position), as compared to the trigger pull effort required with conventional trigger mechanisms. This is achieved by utilizing a structure in which frictional resistance is reduced, in one embodiment, the trigger assembly  20  preferably also provides a consistent resistance to the movement of the trigger  26  from the load position to the release position. Accordingly, the trigger assembly  20  enables the user to maintain the device in position so that it is accurately aimed when the trigger is pulled. 
     Preferably, the trigger pivot pin  28  is supported in the housing  24 . In  FIG. 2 , a substantially planar reference surface  60  on the housing  24  is identified. For illustrative clarity, the reference surface  80  is formed and positioned so that, when the trigger  26  is in the loaded position, the surface  60  is substantially parallel with a front surface  62  of the trigger  26 . At this point, as can be seen in  FIG. 2 , the trigger rotation is 0°, i.e., the front surface  62  of the trigger  26  is parallel with the reference surface  60 . 
     As can be seen in  FIGS. 2-7B , to move the trigger  26  from the load position ( FIGS. 1A, 2 ) to the release position ( FIG. 7B ), the trigger  26  is rotated about the trigger pivot pin  28  through the arc  58 , i.e., in the direction indicated by arrow “C” in  FIGS. 2-7A . As illustrated in  FIGS. 2-7B , the trigger  26  is moved from the load position ( FIG. 2 ), in which the captured refer  50  is held between the first and second sear surfaces  38 ,  48 , to the release position ( FIG. 7B ), in which the second sear surface  46  is disengaged from the captured roller  50 . 
     As can be seen in  FIGS. 7A and 7B , it is preferred that the first sear surface  38  remains engaged with the captured roller  50  while the trigger  26  moves through the arc  58 , and also when the trigger  26  is in the release position. For Instance, as shown in  FIG. 3 , when the trigger  26  has rotated approximately 2° in the direction indicated by arrow “C”, the sear arm  36  is pivoted downwardly relative to the body portion  44  (i.e., also in the direction indicated by arrow “C”) to a corresponding extent. The progressive rotational movement of the trigger  26  through the arc  58 , i.e., generally from the load position to the release position, can be seen in  FIGS. 4  (approximately 4°),  5  (approximately 5°),  6  (approximately 6°), and  7 A (approximately 8°). 
     As can be seen in  FIG. 1C , in one embodiment, the captured roller  50  preferably is elongate and at least partially defines a central axis  84  thereof. Preferably, the captured roller  50  is mounted in the housing  24  for rotation of the captured roller  50  about the central axis  64  and for movement of the captured roller  50  substantially transverse to the central axis  84  as the trigger  26  moves from the load position to the release position to provide substantially consistent frictional resistance to movement of the first and second sear surfaces  38 ,  48  relative to each other. In particular, the captured roller provides roiling frictional resistance to movement of the first and second sear surfaces relative to each other. 
     It is also preferred that the captured roller  50  is substantially in the form of a right cylinder, and extends between ends  66 ,  68  thereof. As can be seen in  FIG. 10 , the captured roller  50  preferably is positioned in the housing  24  with its ends  66 ,  68  located in apertures  70 ,  72  on each side of a slot  74  formed in the housing  24 . Those skilled in the art will appreciate that the captured roller  50  preferably is retained relatively loosely in the apertures  70 ,  72  to permit the captured roller  50  to rotate, and also to move substantially transversely to the central axis  64 , as will be described. Because of this, the frictional resistance to movement of the first and second sear surfaces relative to each other is at least primarily rolling frictional resistance, i.e., because the roller  50  rotates about its central axis. However, because the roller is also movable in the apertures  70 ,  72  in directions substantially transverse to the central axis  84 , the roller  50  is also movable to accommodate the movement of the first and second sear surfaces relative to each other as the trigger is pulled. It will be understood that a number of elements are omitted from  FIG. 1D  for clarity of illustration. 
     Those skilled in the art would appreciate that the apertures  70 ,  72  preferably are somewhat elongate. For example, as show in  FIG. 7B , the aperture  70  preferably has an oblong outline, to permit substantial movement of the captured roller  50  in directions that are substantially transverse to the central axis  64  of the captured roller  50 . Accordingly, the captured roller  50  is at least partially positioned in the pair of apertures  70 ,  72  formed in the housing  24 , to permit limited transverse movement of the captured roller  50 , i.e., movement transverse to the central axis  64 . 
     In one embodiment, the firing element  40  preferably is biased to the second position, it is preferred that the trigger assembly  20  also includes a biasing element  78  supported in the housing  24  and engaged to the firing element  40 , for biasing the firing element  40  to the second position thereof. Preferably, the biasing element  76  is positioned to urge the firing element  40  to rotate about the firing element pivot pin  42  substantially in the direction indicated by arrow “D” in  FIG. 7B . Those skilled in the art would be aware of suitable biasing elements. In one embodiment, the biasing means  76  preferably is a compression spring, as shown in  FIGS. 1A and 2-7B . 
     As can be seen in  FIG. 7B , once the second sear surface  46  is disengaged from the captured roller  50 , the body portion  44  is free to pivot about the firing element pivot pin  42  in the direction indicated by arrow “D”, resulting in corresponding rotational movement of the engagement portion  48 . As illustrated in  FIG. 7B , when the engagement portion (or hook portion)  48  pivots sufficiently far in the direction indicated by arrow “D”, the bowstring  56  is released, and a bolt (not shown) is launched, propelled by the energy that has been stored in the bowstring  56 . Those skilled in the art would appreciate that the movement of the released bowstring  56  is in the direction indicated by arrow “A” in  FIG. 7B , and the bolt is launched in the direction indicated by arrow “A”. 
     Devices typically include safety catches, to prevent inadvertent discharge. In one embodiment the trigger assembly  20  preferably also includes a safety element  78  pivotably mounted about a safety element pivot pin  80 . Preferably, the safety element  78  includes a safety element engagement surface  82  ( FIG. 3 ). Also, and as can be seen in  FIGS. 1A and 2 , if is preferred that the trigger  26  additionally includes a safety arm  84  extending substantially transversely relative to the trigger arm  30 , the safety arm  84  having a safety arm engagement surface  86  ( FIG. 3 ). As can also be seen in  FIGS. 1A and 2 , when the trigger  26  is in the loaded position, the safety element  78  preferably is positioned for engagement of the safety element engagement surface  82  and the safety arm engagement surface  88 , to lock the trigger  26  in the load position. 
     INDUSTRIAL APPLICABILITY 
     In use, when the trigger  26  is in the load position and the user wishes to release the bowstring  56 , the safety element  78  is first released by the user. As can be seen in  FIG. 3 , to release the safety element  78 , the safety element  78  is pivoted about the safety element pivot pin  80  in the direction indicated by arrow “E” in  FIG. 3 . This pivoting movement disengages the safety element engagement surface  82  from the safety arm engagement surface  86 . Due to such disengagement, the trigger  26  is permitted to rotate in the direction indicated by arrow “C” about the trigger pivot pin  28  ( FIG. 3 ). 
     It can be seen from  FIGS. 2-7B  that, after the safety element  78  has been released, when the user presses the trigger arm  30  in the direction indicated by arrow “B”, the trigger  26  pivots about the trigger pivot point  28  in the direction indicated by arrow “C” ( FIG. 2 ). 
     As can be seen in  FIGS. 3-7B , the captured roller  50  remains engaged with the first sear surface  38  as the first sear surface  38  is pivoted generally downwardly (i.e., in the direction indicated by arrow “C” in  FIG. 7A ) relative to the body portion  44  as the trigger  26  is pivoted in the direction indicated by arrow “E” about the trigger pivot point  28 . As can be seen in  FIGS. 3-7B , ultimately, the second sear surface  46  is disengaged from the captured roller  50 , and the firing element  40 , urged to do so by the resilient element  76 , pivots about the catch pivot point  46  in the direction indicated by arrow “D”. Due to the engagement portion  48  pivoting sufficiently upwardly, the bowstring  56  is released at this point. 
     It will be understood that, the firing element  40  moves to the second position thereof substantially immediately upon the firing element  40  disengaging from the captured roller  50 . 
     From the foregoing, it can be seen that, as the trigger  26  is moved from the load position to the release position, each of the first and second sear surfaces  38 ,  46  engages the captured roller  50 , and together the first and second sear surfaces  38 ,  46  cause the captured roller  50  to rotate about the central axis  64  thereof, and also cause the captured roller to move transversely relative to the central axis  64 . Accordingly, and as shown in  FIGS. 2A-7B , the engagement of the first and second sear surfaces  38 ,  46  with the captured roller  50  involves rolling friction. When the trigger  26  is pressed, the sear arm  36  pivots downwardly (i.e., in a clockwise direction, as shown in  FIGS. 2-7B ) while the body portion  44  remains substantially stationary relative to the housing  24 , causing the captured roller  50  to rotate about its central axis  64  in the clockwise direction (as shown in the drawings). 
     Accordingly, because the trigger assembly  20  of the invention includes the captured roller  50  held between the first and second sear surfaces  38 ,  46 , the first and second sear surfaces  38 ,  46  do not engage each other, i.e., they do not slide against, each other, unlike trigger mechanisms of the prior art, instead, they engage the captured roller, resulting in significantly less frictional resistance to movement of the trigger  26  from the load position to the release position, as compared to the frictional resistance encountered in conventional trigger mechanisms. 
     Those skilled in the art would appreciate that the movement of the captured roller  50  relative to the first and second sear surfaces  38 ,  46  due to the trigger  26  being pulled tends to be consistent every time the trigger is pulled, due to the relatively low rolling friction, resulting in the captured roller  50  and the first and second sear surfaces  28 ,  46  being subjected to less wear than the sear surfaces in sliding engagement, in conventional trigger mechanisms. 
     It has been determined that, in the trigger assembly  20  of the invention, the amount of pull required (i.e., the load required to be directed onto the trigger  30 ) is relatively small. This is because, as described above, the trigger assembly  20  of the invention involves rolling friction, not sliding friction. It has also been determined that changes in the first and second sear surfaces  38 ,  46  can materially affect the relevant characteristics of the trigger assembly  20 , as will be described. 
     It will be understood that the details of the arc  58  (i.e., the position of the trigger  26  relative to the reference surface  80 ) as shown in  FIGS. 2-7B  are dependent on the specific configurations of the parts of the trigger assembly  20 . In particular, the measurements of the position of the trigger on the arc  58  as provided in  FIG. 11  (i.e., along the x axis thereof) are representative and exemplary only, and are not based on the trigger assembly  20  as illustrated in  FIGS. 1A and 2-7B , which is not drawn to scale. 
     In one embodiment, the first and second sear surfaces  38 ,  46  are at least partially planar ( FIG. 8 ). As can be seen in  FIG. 11 , in this embodiment (identified in  FIG. 11  as “Embodiment (1)”), the trigger pull load required to move the trigger through the arc  58  is relatively modest, and gradually increases until the bowstring is released. As illustrated in  FIG. 11 , compared to the load required to release the bowstring in the typical prior art trigger, far less load (i.e., far less pressure on the trigger) is needed in this embodiment to achieve release. 
     As can be seen in  FIG. 8 , when the trigger is squeezed, a moment of force is generated, with a line of action (“L A ”) directed to a point “P” offset from the trigger arm pivot point “T P ” by a moment arm “M A ”. Due to this, the pressure exerted on the trigger  26  gradually increases as the trigger moves from the loaded position to the released position. 
     As can be seen, e.g., in  FIG. 6 , as the trigger  26  is pulled from the load position to the release position, the first sear surface is moved downwardly (as illustrated in  FIGS. 1A, 2-7B, and 8-10B ) relative to the second sear surface and the captured roller  50 . 
     Because the captured roller  50  is held between the first and second sear surfaces, the downward movement of the first sear surface results in the first sear surface also moving downward relative to the captured roller. As the trigger approaches the release position (e.g., as shown in  FIGS. 4-7A ), the captured roller engages parts of the first sear surface that are in an upper region “U” of the first sear surface ( FIG. 8 ). 
     In one embodiment, either or both of the first and second sear surfaces  38 ′,  46 ′ preferably is at least partially concave. The results for this embodiment of the trigger assembly of the invention are graphically represented in the curve identified as “Embodiment (2)— FIG. 9 ” in  FIG. 11 . As can be seen in  FIG. 9 , in one embodiment of the trigger assembly, the first and second sear surfaces  38 ′,  46 ′ are at least partially concave. Preferably, the first and second sear surfaces  38 ′,  46 ′ preferably are both defined by respective radii “R 1 ”, “R 2 ” from the trigger arm pivot point “T P ” so that the curvature of each of the sear surfaces  38 ′,  46 ′ is substantially the same. As can be seen in  FIG. 9 , the radii “R 1 ”, “R 2 ” define arcs that are generally parallel to the arc defined by the downward pivoting of the sear arm  36  when the trigger  26  is pulled. Such arc is generally indicated by arrow “C” in  FIG. 9 . Accordingly, substantially no moment is generated in the operation of this embodiment. As can be seen in  FIG. 11 , as a result, the trigger pull load required to move the trigger front the load position to the release position is substantially the same throughout. 
     In another embodiment of the trigger assembly shown in part in  FIGS. 10A and 10B , the first and second sear surfaces are formed to cooperate to provide preselected roiling frictional resistance to movement of the trigger. As shown in FIGS,  10 A and  10 B, the first sear surface  38 ″ preferably includes two or more substantially planar first and second surfaces  88 ,  90  defining an obtuse angle “θ” therebetween. In this embodiment, the second sear surface  46  preferably is substantially planar. 
     When the trigger is initially moved from the load position, the captured roller  50  is held between the first surface  88  and the second sear surface  46 . As noted above, as the trigger moves toward its release position, the first sear surface moves downwardly relative to the second sear surface and the captured roller. Based on the foregoing, therefore, those skilled in the art would appreciate that as the trigger approaches the release position, the captured roller  50  is engaged by the second surface  90 . Because the second surface  00  is slanted toward the second sear surface  45 , the captured roller  50  is squeezed more tightly between the first and second sear surfaces  38 ″,  46  when the roller  50  engages the second surface  90  than when the captured roller  50  is between the first surface  88  and the second sear surface. Those skilled in the art would also appreciate that, when the captured roller  50  is held between the second surface  90  and the second sear surface  46 , because the captured roller  50  is more tightly held therebetween than between the first surface  88  and the second sear surface  46 , more rolling frictional resistance is offered by the roller  60  to movement of the second sear surface  46  relative to the first sear surface  38 ″. Accordingly, after the captured roller  50  engages the second surface  90 , the trigger  26  is required to be squeezed harder in order to enable the firing element  40  to clear the captured roller  50 . 
     The result of the configuration of the first sear surface  38 ″ and the second sear surface  46  is represented in  FIG. 11 . As can be seen in the curve identified as “Embodiment (3)— FIGS. 10A, 10B ”, due to the positioning of the first and second surfaces  88 ,  90 , a distinctly higher trigger pull load is required to be applied in order to release the bowstring after the trigger has reached a transition position, after a gradually increasing (but significantly lower) load is applied to move the trigger  26  over most of the arc  58 . When the captured roller  50  first engages the second surface  90 , the trigger  26  is at the transition position. 
     As shown in the example provided in  FIG. 11 , to move the trigger over most of the arc  58 , a gradually increasing load of between about 0.7 and 0.8 pounds is applied. However, once the trigger  26  has reached the transition position (identified as “X” on the curve for “Embodiment (3)” in  FIG. 11 ), in order to move the trigger through the last part of its arc to the release position, a load of approximately 1.0 pound is required to be applied. 
     In practice, this embodiment is advantageous because the user can pull the trigger through the arc to the transition position with confidence that the bowstring is not to be released until the transition position has been passed. Release is then accomplished by squeezing the trigger  26  to cause if to move through the final portion of the arc, i.e., from the transition position to its release position. 
     As can be seen in  FIG. 11 , squeezing the trigger  26 , once the trigger  26  is at the transition position “X” in the arc  58 , involves pivoting the trigger  26  through a very small portion of the arc  58 , e.g., about 0.25°. It can be seen, therefore, that the trigger  26  can quickly be squeezed by the user for prompt release without applying significant force. However, the force required to move the trigger past the transition position “X” preferably is significantly greater than the force required to move the trigger to the transition position, as illustrated in  FIG. 11 . 
     In summary, and based on the foregoing, the first and second sear surfaces  38 ″,  46  cooperate to permit the trigger  26  to be movable from the load position toward the release position upon application of a first trigger pull load on the trigger until the trigger reaches the transition position. The first and second sear surfaces  38 ″,  46  also cooperate to permit the trigger  26  to be movable from the transition position toward the release position upon application of a second trigger pull load on the trigger. The captured roller is  50  is mounted in the housing  24  for rotation of the captured roller  50  about the central axis  64  and for movement of the captured roller  50  substantially transverse to the central axis  84  as the trigger  26  moves from the load position to the transition position to provide e substantially consistent first (rolling) frictional resistance to movement of the first and second sear surfaces  38 ″,  46  relative to each other, and to provide a substantially consistent second (rolling) frictional resistance to movement of the first and second sear surfaces  38 ″,  46  relative to each other as the trigger  26  moves from the transition position to the release position. 
     As described above, it is preferred that the second trigger putt load exceeds the first trigger pull load, to hinder activation of the firing mechanism. In particular, because the second pull load exceeds the first pull load, inadvertent activation of the firing mechanism is thereby hindered, 
     In summary, based on  FIGS. 8-10B , it will be appreciated by those skilled in the art that the first and second sear surfaces may be formed in a number of ways in order to result in such trigger effort profile (i.e., trigger effort as a function of trigger rotation, as illustrated in  FIG. 11 ) as is desired. For example, the first and second sear surfaces may be defined by arcs which may or may not have a common center point. As another example, one of the first and second sear surfaces may be defined by an arc, and the other may be defined by one or more planes. 
     Another embodiment of the trigger assembly  120  of the invention is illustrated in  FIG. 12 . Preferably, the trigger assembly  120  additionally includes a biasing means  192  for biasing a trigger  126  to the load position thereof, it is also preferred that the biasing means  192  is adjustable, to adjust a minimum trigger pull load for moving the trigger  126  from the load position and toward the release position. 
     The biasing means  192  preferably provides a way to “tune” the responsiveness of the trigger  126  to pressure from the user&#39;s finger. In one embodiment, and as illustrated in  FIG. 12 , the biasing means  192  preferably is a torsion spring positioned in a cavity  193  therefor in a housing  124 . Preferably, an end  194  of the biasing means  192  is secured in a front end  195  of a sear arm  136  of the trigger  126 . For instance, as illustrated in the exemplary embodiment of  FIG. 12 , the front end  195  preferably includes an aperture  198  in which the end  194  of the torsion spring  192  is positionable. 
     As can be seen in  FIG. 12 , the result is that the biasing means  192  urges the sear arm  136  to pivot generally upwardly, i.e., as indicated by arrow “F” in  FIG. 12 . It will be appreciated by those skilled in the art that, by modifying the relevant characteristics of the biasing means  192 , the amount of force required to move the trigger  126  from the load position to the release position is correspondingly modified. 
     In one embodiment, the invention provides an embodiment of the device  54  ( FIG. 1B ) preferably including the trigger assembly  20 . The device of the invention preferably also includes the trigger assembly  120 , described above. For instance, the invention includes a crossbow including the trigger assembly of the invention. Alternatively, the invention includes a firearm including the trigger assembly of the invention. 
     As indicated above, the device of the invention may be any device including a firing mechanism activatable by movement of a trigger, and generally, the device is for firing or launching a projectile. An alternative embodiment of the trigger assembly  220  of the invention is shown in FIGS,  13 A- 13 D. As will be described, the trigger assembly  220  is for use with a firing mechanism  222  ( FIG. 13D ) in a firearm  254  ( FIG. 15 ). Preferably, the trigger assembly  220  includes a trigger  226  pivotably mounted on a trigger pivot pin  228  between a load position ( FIGS. 13A, 13B ) to a release position ( FIG. 13D ). The trigger  226  preferably includes a trigger arm  230  extending between a fop end  232  and a bottom end  234 . The trigger  226  preferably also includes a sear arm  236  including a first sear surface  238 . In addition, the trigger assembly  220  preferably also includes a firing element  240  (i.e., a hammer) pivotably mounted on a firing element pivot pin  242 . As can be seen in  FIG. 13B , the trigger  226  preferably is pivotable in the direction indicated by arrow “G” in  FIG. 13B . It is also preferred that the firing element  240  is biased in the direction indicated by arrow “H” in  FIG. 13B  by biasing means (not shown). Preferably, the firing element  240  includes a second sear surface  248 . It is also preferred that a captured roller  250  is held between the first and second sear surfaces  238 ,  246  until the trigger  236  reaches the release position. The firing element  240  is pivotable between a first position (FIGS,  13 A,  13 B) in which the firing element  240  is held by the trigger  226 , and a second position ( FIG. 13D ), in which the firing element  240  activates the firing mechanism  222 . 
     When the user applies a trigger pull load on the trigger  226 , the trigger pivots in the direction indicated by arrow “G”. in  FIG. 13C , the pivoting movement of the trigger  226  from the load position in the direction indicated by arrow “G” is shown by the dashed outline of the trigger  226 , in which the trigger  226  is shown in an intermediate position. For clarity of illustration, the trigger, when located in the intermediate position ( FIG. 13C ), is identified by the reference numeral  226 A. 
     Also, in  FIG. 13D , the trigger  226  is shown in dashed outline in its release position. When located in the release position ( FIG. 13D ), the trigger is identified by the reference numeral  226 B. 
     When the trigger  226  reaches the release position, the second sear surface  248  on the firing element  240  disengages from the captured roller  250 , and urged by its biasing means, the firing element  240  pivots in the direction indicated by arrow “H” to its second position, where it activates the firing mechanism  222 . 
     It will be understood that, for clarity of illustration, only a small portion of the firing mechanism  222  is shown in  FIG. 13D . For instance, the part of the firing mechanism shown as being engaged by the firing element  240  is a firing pin of the device  254 . The firing pin as shown in  FIG. 13D  is exemplary only. As noted above, the trigger assembly may activate the firing mechanism in various ways, depending on the firing mechanism. For instance, instead of activation by striking the firing pin (as shown in  FIG. 13D ), the firing mechanism may be activated by release of the firing pin. 
     It will also be understood that the trigger assembly  220  may have any of the features described above in connection with other embodiments of the trigger assembly. For instance, although the sear surfaces  238 ,  246  are shown as being substantially planar, it will be understood that the sear surfaces in the trigger assembly included in firearms may have various configurations (e.g., as shown in FIGS,  9 ,  10 A, and  10 B). 
     An alternative embodiment of the trigger assembly  220 ′ is illustrated in FIGS,  14 A- 14 D. As will be described, the trigger assembly  220 ′ is for use with a firing mechanism  222 ′ ( FIG. 14D ) in the firearm  254  ( FIG. 15 ). Preferably, the trigger assembly  220 ′ includes a trigger  226 ′ pivotably mounted on a trigger pivot pin  228 ′ between a bad position ( FIGS. 14A, 14B ) to a release position ( FIG. 14D ). The trigger  226 ′ preferably includes a trigger arm  230 ′ extending between a top end  232 ′ and a bottom end  234 ′. The trigger  226 ′ preferably also includes a sear arm  236 ′ including a first sear surface  238 ′. In addition, the trigger assembly  220 ′ preferably also includes a firing element  240 ″ (i.e., a hammer) pivotably mounted on a firing element pivot pin  242 ′. As can be seen in  FIG. 14B , the trigger  226 ′ preferably is pivotable in the direction indicated by arrow “J” in  FIG. 148 , when a trigger pull load is applied to the trigger. It is also preferred that the firing element  240 ′ is biased in the direction indicated by arrow “K” in  FIG. 14B  by biasing means (not shown). Preferably, the firing element  240 ′ includes a second sear surface  246 ′. It is also preferred that a captured roller  250 ′ is held between the first and second sear surfaces  238 ′,  246 ′ until the trigger  238 ′ reaches the release position. The firing element  240 ′ is pivotable between a first position ( FIGS. 14A, 148 ) in which the firing element  240 ′ is held by the trigger  226 ′, and a second position ( FIG. 14D ), in which the firing element  240 ′ activates the firing mechanism  222 ′. 
     When the user applies a trigger pull load on the trigger  226 ′, the trigger pivots in the direction indicated by arrow “J”. In  FIG. 14C , the pivoting movement of the trigger  226 ′ from the load position in the direction indicated by arrow “J” is shown by the dashed outline of the trigger  226 ′, in which the trigger  226 ′ is shown in an intermediate position. For convenience, the trigger, when located in the intermediate position ( FIG. 14C ), is identified by the reference numeral  226 ′A. 
     Also, in  FIG. 14D , the trigger  226 ′ is shown in dashed outline in its release position. When located in the release position ( FIG. 14D ), the trigger is identified by the reference numeral  226 ′B. 
     When the trigger  226 ′ reaches the release position, the second sear surface  246 ′ on the firing element  240 ′ disengages from the captured roller  250 ′, and urged by its biasing means, the firing element  240 ′ pivots in the direction indicated by arrow “K” to its second position, where it activates the firing mechanism  222 . 
     It will be understood that, for clarity of illustration, only a small portion of the firing mechanism  222 ′ is shown in  FIG. 14D . For instance, the part of the firing mechanism shown as being engaged by the firing element  240 ′ is a firing pin of the device  254 . The firing pin as shown in  FIG. 14D  is exemplary only. As noted above, the trigger assembly may activate the firing mechanism in various ways, depending on the firing mechanism. For instance, instead of activation by striking the firing pin (as shown in  FIG. 14D ), the firing mechanism may be activated by release of the firing pin. 
     It will also be understood that the trigger assembly  220 ′ may have any of the features described above in connection with other embodiments of the trigger assembly. For instance, although the sear surfaces  238 ′,  246 ′ are shown as being substantially planar, it will be understood that the sear surfaces in the trigger assembly included in firearms may have various configurations (e.g., as shown in  FIGS. 9, 10A, and 10B ). 
     Although in embodiments described above the captured roller  50  is described as being positioned in the housing  24  with its ends  66 ,  88  located in apertures  70 ,  72  on each side of a slot  74  formed in the housing  24 , those skilled in the art will appreciate that alternatives are available. For example, in another embodiment it may not be desirable to have apertures formed in the housing. Turning now to  FIGS. 16 to 18 , another embodiment of the trigger assembly is shown and is referred to generally by the reference numeral  200 . As can been seen, (rigger assembly  200  is generally similar to trigger assembly  20  with the following exceptions. In this embodiment, the sear arm  36  comprises a guide  260  positioned adjacent to the first sear surface  38 . In this embodiment, the guide comprises a protuberance  265   a  extending laterally in a direction from a position adjacent to the first sear surface  38  and a second protuberance  265   b  extending in an opposite direction from a position adjacent to the first sear surface  38 . The protuberances  265   a ,  265   b  are generally oblong-shaped and define apertures  270 ,  272 , respectively, in this embodiment, the captured roller  50  is positioned with its ends  66 ,  68  located in apertures  270 ,  272 . Similar to trigger assembly  20 , the apertures  270 ,  272  are dimensioned to permit the captured roller  50  to be retained relatively loosely therewithin, to permit the captured roller  50  to rotate and to move substantially transversely to the central axis  64 , as described above. 
     The operation of trigger assembly  200  is generally similar to that of trigger assembly  20  and as such the specifics will not be described. 
     Further, although in the above embodiment the guide is described as pad of the sear arm, those skilled in the art will appreciate that in another embodiment the guide may form part, of the firing element, rather than the sear arm. 
     It will be appreciated by those skilled in the art that the invention can take many forms, and that such forms are within the scope of the invention as described above. The foregoing descriptions are exemplary, and their scope should not be limited to the preferred versions provided therein.