Abstract:
A lobed projectile apparatus includes a body portion and a lobe extending radially away from a longitudinal axis of the body portion. The lobe substantially fills a gap width between two rails of a crossbow or is configured to contact an anti-dry-fire mechanism of a crossbow. The nock may be used to avoid thy fires of a crossbow by controlling an anti-dry fire mechanism and by securing a bowstring to the projectile.

Description:
RELATED APPLICATIONS 
       [0001]    This is a continuation of U.S. patent application Ser. No. 15/260,177, filed on 8 Sep. 2016, now pending, which is a continuation of U.S. patent application Ser. No. 14/814,783 filed on 31 Jul. 2015, now U.S. Pat. No. 9,441,925, issued on 13 Sep. 2016, the disclosures of which are incorporated, in their entireties, by this reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure generally relates to nocks for projectiles used in archery bows and crossbows and particularly relates to nocks with circumferentially spaced lobes for use in crossbows. 
       BACKGROUND 
       [0003]    Bow and crossbow archers constantly seek ways to improve the accuracy and reliability of their bows and crossbows. One way to improve accuracy and reliability is to control the orientation of the projectile (e.g., an arrow or bolt) when it is launched from the bow or crossbow. In an archery bow (e.g., a compound bow or recurve bow), the fletchings or vanes of the arrow should be oriented so that they have minimal interference with the cables, arrow rest, and riser as the arrow is launched. Similarly, in a crossbow the fletchings or vanes of the bolt must be properly oriented to avoid conflicting contact with the rails as the bolt is launched. 
         [0004]    The nock at the trailing end of an arrow or bolt may also affect the reliability of the bow. For example, it may be possible to dry fire a bow or crossbow (i.e., release the string without launching an arrow) if the bowstring is able to slip laterally around the trailing end of the arrow and move along the shaft of the projectile when the bowstring is released. When a dry fire occurs, the energy that otherwise would be transmitted to the projectile is absorbed by the bow or crossbow, which can cause undesirable consequences. 
         [0005]    The trailing end of an arrow or bolt for a crossbow, for example, most often includes a nock to help orient the projectile relative to the crossbow and to keep the bowstring secured to the projectile until it reaches the proper release position. A half moon nock, for example, may be attached to a bolt so that when a crossbow&#39;s bowstring extends across and within the half-moon shaped groove of the nock, an index vane of the bolt is properly oriented between rails of the crossbow, When the bowstring is released, the C-shaped or V-shaped groove at the end of the nock keeps the bowstring aligned directly with the longitudinal axis of the shaft of the bolt to avoid a situation where the bowstring slips to one side of the neck when the bolt is launched from the crossbow. The force of the bowstring is therefore efficiently and properly transferred to the projectile. 
         [0006]    However, some of these types of nocks have drawbacks, nocks and vanes are typically secured to the bolt shafts as part of an assembly process performed by manufacturers or by end-users. These processes are susceptible to imperfections and errors that can affect the nock&#39;s orientation and performance. If a vane or half-moon nock is not attached correctly to a bolt shaft, the index vane may not be oriented to the bowstring properly when loaded into a crossbow. As such, the vane may undesirably drag against the crossbow rails when the bowstring is released or the bowstring will not seat and engage the nock correctly. A misaligned nock may cause the bolt to be pushed to one side during the launch process, thereby affecting the bolt&#39;s flight and potentially causing a dry fire. Additionally, even if the nock is properly attached to the shaft, the archer load the bolt incorrectly (e.g., using the wrong vane as an index vane) and may thereby inhibit proper interaction between the nock and the bowstring. 
         [0007]    Some nock makers have engineered nocks with multiple rear groove shapes inorder to reduce the chance that a bolt is improperly loaded into the crossbow. These nocks are nevertheless still vulnerable to misalignment by the manufacturer or end user and may not provide enough grip to keep the bowstring seated against the bolt, so the potential for dry fires is still present. Crossbows conventionally use some kind of anti-dry fire (ADF) mechanism to prevent release of the bowstring unless a bolt is loaded onto the crossbow, but such devices do not determine the orientation (rotational or longitudinal) of the bolt relative to the crossbow, and thus an improperly loaded bolt may result in a dry fire. There is therefore a need for improvements to existing archery nocks and anti-dry fire devices. 
       SUMMARY 
       [0008]    One aspect of the present disclosure relates to a lobed nock for a projectile which may comprise a shaft having a leading end and a trailing end, a point positioned at the leading end, a plurality of circumferentially spaced apart vanes positioned on the shaft between the leading end and the trailing end, and a nock positioned at the trailing end. The nock may comprise a body portion attached to the shaft, wherein the body portion has a central axis, and a lobe on the outer surface of the body portion, wherein the lobe extends radially away from the central axis. 
         [0009]    In some embodiments, the lobe is longitudinally aligned with one of the plurality of circumferentially spaced apart vanes. The nock may comprise a plurality of lobes on the outer surface f the body portion and extend radially away from the central axis. The nock may include a plurality of bowstring seats, with each of the bowstring seats being formed by at least two of the lobes of the plurality of lobes. In some cases the bowstring seats each have a seat axis and the seat axes may collectively form a triangle relative to the body portion. Some embodiments of the projectile may comprise a bowstring seat having an at least partially cylindrical bowstring contact surface. 
         [0010]    The body portion of the nock may have a rear surface and the lobe may extend rearward from the body portion relative to the rear surface. The rear surface may be flat and/or recessed. The lobe may comprise a retaining surface facing the body portion. 
         [0011]    Another aspect of the disclosure relates to a nock for an archery arrow or bolt, which comprises a front end portion configured to be inserted into an arrow or bolt, with the front end portion having a longitudinal axis and a rear end portion configured to extend rearward from the arrow or bolt upon insertion of the front end portion into the arrow or bolt. A lobe may be attached to the rear end portion and may extend away from the rear end portion in a radial direction relative to the longitudinal axis. 
         [0012]    A plurality of lobes may be attached to the rear end portion and may radially extend away from the rear end portion relative to the longitudinal axis. The plurality of lobes may be circumferentially spaced apart around the rear end portion. One of the plurality of lobes may be configured to extend in a vertical direction away from the rear end portion and at least two other lobes of the plurality of lobes extend laterally relative to the vertical direction. The rear end portion may have a flat rear surface. The rear end portion may have a central portion and a peripheral portion, with the central portion being recessed relative to the peripheral portion. The lobe may extend rearward from the rear end portion and may have a curved rear surface. 
         [0013]    The rear end portion may have an at least partially cylindrical bowstring contact surface. The cylindrical bowstring contact surface may be positioned relative to the rear end portion such that a bowstring contacting the cylindrical bowstring contact surface intersects the longitudinal axis of the nock. The lobe may also have a flat or pointed outer surface facing radially away from the longitudinal axis. 
         [0014]    Yet another aspect of the disclosure relates to a nock-based bolt detection system for a crossbow. The system may comprise a crossbow bolt that is connected to a nock, with the nock having a lobe extending radially outward from the nock. The system may also include a crossbow having a front end and a rear end, two laterally-extending limbs, and a bowstring connected to the limbs. A string retaining member may be configured to retain the bowstring when the bowstring is under tension, with the string retaining member being configured to release the bowstring when shooting the crossbow. The system may also have a nock contact member having a first position relative to the crossbow wherein the nock contact member prevents release of the bowstring from the string retaining member and having a second position relative to the crossbow wherein the nock contact member does not prevent release of the bowstring from the string retaining member. The nock contact member may be configured to move between the first position and the second position by contacting the lobe of the bolt. 
         [0015]    Furthermore, the string retaining member may be biased to a bowstring retaining position. The nock contact member may be biased to a bowstring release prevention position. The nock may comprise at least one additional lobe positionable above the bowstring while the nock contact member is in the second position. The bowstring may comprise an outer surface having a cross-sectional profile, and the at least one additional lobe may comprise a surface having a shape following the cross-sectional profile of the bowstring. 
         [0016]    The bolt may also include a vane, with the lobe being longitudinally aligned with the vane. The crossbow may have rails, with the lobe being positioned between the rails. The nock contact member may be pivotable between the first and second positions. 
         [0017]    The above summary of the present invention is not intended to describe each embodiment or every implementation of the present invention. The Figures and the detailed description that follow more particularly exemplify one or more preferred embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The accompanying drawings and figures illustrate a number of exemplary embodiments and are part of the specification. Together with the present description, these drawings demonstrate and explain various principles of this disclosure. A further understanding of the nature and advantages of the present invention may be realized by reference to the following drawings. In the appended figures, similar components or features may have the same reference label. 
           [0019]      FIG. 1  shows a crossbow according to an embodiment the present disclosure. 
           [0020]      FIG. 2  shows a bolt according to an embodiment of the present disclosure. 
           [0021]      FIG. 3  shows an exploded view of the bolt of  FIG. 2 . 
           [0022]      FIG. 4A  shows a front perspective view of a nock according to an embodiment of the present disclosure. 
           [0023]      FIG. 4B  shows a rear perspective view of the nock of  FIG. 4A . 
           [0024]      FIG. 4C  is a front view of the nock of  FIG. 4A . 
           [0025]      FIG. 4D  is a rear view of the nock of  FIG. 4A . 
           [0026]      FIG. 5A  shows a front perspective view of a nock according to an embodiment of the present disclosure. 
           [0027]      FIG. 5B  shows a rear perspective view of the nock of  FIG. 5A . 
           [0028]      FIG. 5C  is a front view of the nock of  FIG. 5A . 
           [0029]      FIG. 5D  is a rear view of the nock of  FIG. 5A  shown relative to a set of crossbow rails and a bowstring. 
           [0030]      FIG. 6A  shows a front perspective view of a nock according to an embodiment of the present disclosure. 
           [0031]      FIG. 6B  shows a rear perspective view of the nock of  FIG. 6A . 
           [0032]      FIG. 6C  is a front view of the nock of  FIG. 6A . 
           [0033]      FIG. 6D  is a rear view of the nock of  FIG. 6A . 
           [0034]      FIG. 7A  shows a front perspective view of a nock according to an embodiment of the present disclosure. 
           [0035]      FIG. 7B  shows a rear perspective view of the nock of  FIG. 7A . 
           [0036]      FIG. 7C  is a front view of the nock of  FIG. 7A . 
           [0037]      FIG. 7D  is a rear view of the nock of  FIG. 7A . 
           [0038]      FIG. 8A  shows a front perspective view of a nock according to an embodiment of the present disclosure. 
           [0039]      FIG. 8B  shows a rear perspective view of the nock of  FIG. 8A . 
           [0040]      FIG. 8C  is a front view of the nock of  FIG. 8A . 
           [0041]      FIG. 8D  is a rear view of the nock of  FIG. 8A  and is shown relative to a plurality of bowstring positions. 
           [0042]      FIG. 9A  shows a front perspective view of a nock according to an embodiment of the present disclosure. 
           [0043]      FIG. 9B  shows a rear perspective view of the nock of  FIG. 9A . 
           [0044]      FIG. 9C  is a front view of the nock of  FIG. 9A . 
           [0045]      FIG. 9D  is a rear view of the nock of  FIG. 9A . 
           [0046]      FIG. 9E  shows a rear profile cross-section of the nock of  FIG. 9A  relative to a set of crossbow rails. 
           [0047]      FIG. 10A  shows a front perspective view of a nock according to an embodiment of the present disclosure. 
           [0048]      FIG. 10B  shows a rear perspective view of the nock of  FIG. 10A . 
           [0049]      FIG. 10C  is a front view of the nock of  FIG. 10A . 
           [0050]      FIG. 10D  is a rear view of the nock of FIG,  10 A. 
           [0051]      FIG. 10E  is a side view of the nock of  FIG. 10A  and shown relative to a bowstring. 
           [0052]      FIG. 11A  shows a front perspective view of a nock according to an embodiment of the present disclosure. 
           [0053]      FIG. 11B  shows a rear perspective view of the nock of  FIG. 11A . 
           [0054]      FIG. 11C  is a front view of the nock of  FIG. 11A . 
           [0055]      FIG. 11D  is a rear view of the nock of  FIG. 11A . 
           [0056]      FIG. 11E  is a side view of the nock of  FIG. 11A . 
           [0057]      FIGS. 12A-12K  show step-by-step views of the operation and parts of an anti-dry fire (ADF) and firing mechanism of a crossbow according to an embodiment of the present disclosure. 
       
    
    
       [0058]    While the embodiments described herein are susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. However, the exemplary embodiments described herein are not intended to be limited to the particular forms disclosed. Rather, the instant disclosure covers all modifications, equivalents, and alternatives falling within the scope of the appended claims. 
       DETAILED DESCRIPTION 
       [0059]    The present disclosure generally relates to nocks for projectiles used in archery bows and crossbows, but more particularly relates to necks with lobes for use with crossbows. In an exemplary embodiment, a bow projectile such as, for example, a crossbow bolt or an arrow, may have a nock positioned at its trailing end that has a body portion attached to the shaft of the projectile and one or more lobes radially extending from the body portion at circumferentially spaced apart positions. The positions of the lobes may correspond and align with the vanes or fletchings of the projectile. 
         [0060]    The lobes may extend radially away from the longitudinal axis of the body portion and thereby provide a broader rear surface of the nock. Due to having a broader rear surface, there is a broader surface against which the bowstring may contact and there is accordingly a reduced risk of dry fire due to the bowstring slipping past the nock. Additionally, some embodiments may have lobes that at least partially extend around the outer perimeter or circumference of the bowstring when the nock abuts the bowstring so that the bowstring is seated against both the rear surface of the nock and a contoured or curved surface of the lobe. This allows the nock to cradle the bowstring against multiple points on its outer surface, so there is a reduced chance that the bowstring will move relative to the nock when tension in the bowstring is applied to the nock. Additionally, the lobes may contact the bowstring on opposite lateral sides of the projectile (relative to the shaft), so the projectile has improved resistance to axial rotation while shooting. 
         [0061]    One or more of the lobes of the nock may also be configured to fit between rails of a crossbow. The lobe may have a width less than or equal to the width of the space between the rails, and thus the lobe may be positioned between the rails to help prevent the projectile from axially rotating relative to the crossbow by mechanical interference between the nock and the rails in addition to the mechanical contact between the lobes and the bowstring. Furthermore, the downward-positioned lobe that is positioned between the rails may provide additional height to the nock, so the nock makes the projectile more resistant to dry fires that involve the bowstring passing under the projectile. 
         [0062]    An anti-dry fire (ADF) system is also disclosed herein, wherein the lobe of a nock may be used as a contact surface for an ADF lever or other member. The lobe may extend radially away from the shaft or body portion of a bolt, so when a nock is loaded into the crossbow, the lobe may be the only part of the bolt that comes into contact with the ADF member. If a bolt is loaded without a lobed nock or if a bolt is loaded incorrectly (e.g., without a lobe pointing between the rails), the ADF member is not contacted and the bowstring cannot be released. This is because the ADF member is spaced radially away from the shaft of the bolt and therefore is not actuated or contacted by a conventional bolt shaft or nock that does not have a radially extending lobe. If a bolt with a lobed nock is loaded, however, the ADF member is contacted and the bolt is permitted to fire from the crossbow. As a result, the ADF mechanism may reduce the chance of dry fires related to improperly oriented bolts or dry fires that occur when no bolt or a wrong type of bolt is loaded. 
         [0063]    The present description provides examples, and is not limiting of the scope, applicability, or configuration set forth in the claims. Thus, it will be understood that changes may be made in the function and arrangement of elements discussed without departing from the spirit and scope of the disclosure, and various embodiments may omit, substitute, or add other procedures or components as appropriate. For instance, the methods described may be performed in an order different from that described, and various steps may be added, omitted, or combined. Also, features described with respect to certain embodiments may be combined in other embodiments. 
         [0064]    Turning now to the figures in detail,  FIG. 1  illustrates a crossbow  100  according to an embodiment of the present disclosure. The crossbow  100  may comprise a stock  102 , a trigger assembly  104 , a handgrip  106 , a flight groove  108 , and rails  110  on each side of the flight groove  108 . The crossbow  100  may have a front end  112  and a rear end  114 . A foot stirrup  116  and a plurality of limbs  118  may be attached at the front end  112 . A bowstring  120  may extend across the limbs  118  and may move along the stock  102  adjacent to the rails  110 . The crossbow  100  may also comprise sights  122 , a quiver  124  to hold extra bolts  126 , and other accessories. A bolt  200  is shown loaded on the crossbow  100 . 
         [0065]      FIGS. 2 and 3  show a projectile according to an embodiment of the present disclosure. Here, the projectile is a crossbow bolt  200 , but it could be an arrow or other comparable projectile. The bolt  200  may comprise an elongated shaft  202 , an arrow point  204 , a plurality of vanes or fletchings  206 , and a nock  208  insertable into an opening  214  in the rear of the shaft  202  (see  FIG. 3 ). A longitudinal axis may extend centrally through the elongated length of the shaft  202 . The arrow point  204  may be referred to as being at a front end portion  210  of the shaft  202 , and the nock  208  may be referred to as being at a rear end portion  212  of the shaft  202 .  FIG. 3  illustrates an exploded view of the bolt  200  of  FIG. 2 , showing that the arrow point  204 , vanes  206 , and nock  208  may be separate pieces assembled to construct the bolt  200 . In other embodiments, the arrow point  204 , vanes  206 , and/or nock  208  may be integrally formed with the shaft  202  to form a single piece. 
         [0066]    Bolts having the nock of the present disclosure may be shot from the crossbow  100  by cocking the crossbow  100  (thereby flexing the limbs  118  rearward where the bowstring  120  is connected to the limbs and positioning the center of the bowstring  120  toward the rear end  114  of the crossbow  100 , as shown in  FIG. 1 ), loading a bolt onto the rails  110  with an index vane within the flight groove  108 , and pulling the trigger of the trigger assembly  104 . The trigger causes the bowstring  120  to be released, thereby allowing the tension in the limbs  118  to forcefully straighten the bowstring  120  and move the center of the bowstring  120  toward the front end  112  of the crossbow  100 . This movement of the bowstring  120  causes the bowstring to push the bolt along the rails  110  while it contacts the nock and rapidly launch the bolt forward and off of the crossbow  100 . 
         [0067]    Embodiments of nocks of the present disclosure may beneficially reduce the chance of a dry fire of the bolt  200  from the crossbow  100  by (1) broadening the rear surface area of the bolt  200  that is configured to contact the bowstring  120  to help keep the bowstring from slipping around the nock and sliding above or below the shaft  202 , (2) at least partially extending around the bowstring to keep the nock in contact with the bowstring  120  (even if the bowstring  120  moves vertically to a small degree relative to the nock before or after shooting), (3) reducing the chance that the bolt  200  will be inappropriately loaded on the crossbow  100 , and/or (4) interacting with an anti-dry fire (ADF) mechanism. 
         [0068]      FIGS. 4A-11E  show various embodiments of nocks for projectiles such as bolt  200 . Each of these nooks  300 ,  302 ,  304 ,  306 ,  308 ,  310 ,  312 ,  314  has several features typical to all of the nocks, and these features are shown using common indicator numerals. For example, each nock  300 ,  302 ,  304 ,  306 ,  308 ,  310 ,  312 ,  314  comprises a body portion  316  having a front end portion  318  and a rear end portion  320 . The front end portions  318  are configured to be inserted into the opening  214  at the rear end of the shaft  202  of a bolt  200 . Typically, the front end portions  318  fit within the opening  214  using a friction or resilient snap fit that makes the front end portions  318  resist rotation relative to the shaft  202  or withdrawal from the opening  214 . Thus, once inserted into the shaft  202 , the front end portions  318  may remain secured to the shaft  202  under normal use during transportation and shooting the bolt  200 . In some configurations, the entire front end portion  318  may be received within the shaft  202 , and in other configurations, the front end portion  318  may only be inserted partially therein. In some embodiments, a front end portion  318  may also be removable from the shaft  202  when sufficient force is applied to pull the front end portion  318  out of the opening  214 . In order to facilitate the fit of the front end portion  318  in the shaft  202 , the front end portion  318  may comprise a plurality of circumferentially spaced ridges  322  that can be compressible into the opening  214 . In some embodiments, the front end portion  318  may be smooth and without ridges  322 . The front end portion  318  may also be hollowed out or formed with a hollow longitudinal chamber  324  to reduce weight and material costs of the nocks  300 ,  302 ,  304 ,  306 ,  308 ,  310 ,  312 ,  314 . In some embodiments the front end portions  318  may be secured to a shaft  202  using an adhesive, fastener, or other connection method known in the art. 
         [0069]    The rear end portions  320  of the nooks of  FIGS. 4A-11E  each comprise three lobes which each have different features that will be described in detail below in connection with each embodiment individually. Each of the lobes may be sized with a different width W (see  FIG. 4D ) configured to fit between the rails  110  and within the flight groove  108  of the crossbow  100 . Typically, the width W is less than the distance between the rails  110  so that the bolt  200  can slide freely along the groove  108  while the lobe is between the rails  110 . Some embodiments, discussed below, may have a width that tapers between the body of the nock and the radially external tip of the lobe. In those cases, the width W may be defined as the width of the lobe that is either at the base of the lobe or at the radial position on the lobe that aligns with the top of the rails  110  of the crossbow  100  when the bolt  200  is loaded. See, e.g., width W in  FIG. 5D , showing the width of lobe  500  at the top of rails  110 . The width W of the lobes may also be configured to reduce rattling or rotation of the bolt  200  relative to the rails  110  due to the lobe being close to the width of the flight groove  108 . 
         [0070]    Each of the lobes of the rear end portions  320  may have equal widths W, so any of the three lobes may be configured to point downward between the rails  110  of a crossbow  100 . The vane or fletching of the bolt  200  that lies between the rails  110  is conventionally referred to as the index vane, so any of the three lobes may be referred to as an “index lobe” of the nock. Because any of the three lobes may be the index lobe, a bolt  200  having one of the nocks of the present disclosure may be loaded in multiple orientations while still allowing the nock to retain the bowstring  120  in each orientation. By comparison, conventional bolts are only configurable with one vane extending downward as an index vane, so the bolts only have one nocked position. 
         [0071]    In other embodiments, the lobes of the rear end portions  320  may not all have equal widths. For example, a nock may comprise lobes wherein one of the lobes is narrower than the other lobes. The narrower lobe may be narrow enough to fit between the rails  110 , and the other lobes may be too wide to fit. Thus, in this manner the lobes may provide a “go/no-go” design wherein the bolt  200  clearly indicates to the user whether it is loaded properly since the lobe pointing downward on the bolt  200  will either fit between the rails and slide into place easily or the lobe will not fit between the rails and the bowstring  120  may visibly not align with the bolt  200  or the bolt  200  may be impossible to move into the loaded position due to interference of the nock with other parts of the crossbow. 
         [0072]    The nocks of  FIGS. 4A-11E  are pictured with two lobes appearing on the bottom half of the nock body and one lobe appearing on the top half. However, it will be understood by those having skill in the art and by reference to  FIGS. 12A-12K  that when these nocks  300 ,  302 ,  304 ,  306 ,  308 ,  310 ,  312 ,  314  are used with a bolt  200  in a crossbow  100 , one lobe will be pointing downward and the other two lobes will extend diagonally upward relative to the nock body and relative to the shaft  202  of the bolt. This orientation is shown, for example, in  FIGS. 5A-5D . Thus, the pictured nocks may be turned over relative to  FIGS. 4A-4D and 6A-11E  when they are loaded into a crossbow  100 . Typically, the lobes are arranged at 120 degrees of radial symmetry, but other arrangements may be used as well. 
         [0073]    Referring now to the nocks of  FIGS. 4A-11E  individually,  FIGS. 4A-4D  show an embodiment of a nock  300  wherein the lobes  400  each extend peripherally from a body portion  402  of the rear end portion  320  of the nock  300 . The lobes  400  and body portion  402  collectively form a flat rear surface  404 . The flat rear surface  404  has a surface area greater than the surface area of the rear of a shaft  202  of the bolt  200  to which the nock  300  is attached. FIG.  4 D indicates the perimeter of the rear profile A of the shaft  202  in broken lines for comparison with the rear surface  404  of the nock  300 . 
         [0074]    The flat rear surface  404  has a greater width and height than the rear profile A of the shaft  202 . This means that when the bowstring  120  is positioned behind the rear surface  404 , the bowstring  120  would need to vertically slip significantly farther from the longitudinal axis of the bolt  200  in order to slip around the lobes  400  than a traditional nock (e.g., a “flatback” nock) that has a width and height substantially equal to the rear profile A of the shaft  202 . Each of the nocks  302 ,  304 ,  306 ,  308 ,  310 ,  312 ,  314  described below also have a rear profile that is wider and taller than the rear profile A of the shaft  202 . 
         [0075]    The lobes  400  also each have a front surface  406  and two side surfaces  408 . The front surface  406  is broadest at the rear surface  404  and narrows as it extends forward along the rear end portion  320  of the nock  300 . This shape improves the aerodynamic properties of the nock  300  and may make it easier for the user to slide the lobes  400  between the rails  110  of the crossbow  100 . 
         [0076]    The lobes  400  also each have a tip surface  410  that is at the outermost radial distance from the longitudinal axis of the nock  300 . The tip surface  410  may be substantially flat. The tip surface  410  may be used as a contact surface for the anti-dry fire mechanism described below in connection with  FIGS. 12A-12K . 
         [0077]    In some embodiments, the lobes  400  may he of a size and configuration to function as vanes for the bolt  200 . Thus, in some cases there may be no need for vanes  206 , but rather the lobes  400  themselves may be sized and configured sufficient to function as vanes to stabilize the bolt  200 . The lobes  400  and rear end portion  320  of the nock  300  may be enlarged and/or elongated for this purpose. In such cases, the distal-most end of the bolt  200  (including the nock  300 ) may coincide with and be equivalently axially positioned as the distal ends of the lobes  404  in  FIG. 4B or 505  in  FIG. 5B ). Similarly, the lobe may have a highest profile point or highest radial distance from the lobe body portion (e.g.,  402 ), which may coincide with the distal-most end of the bolt  200 . For example, the tip surface  410  of nock  300 , which has the highest profile location/point or highest radial distance from the body portion  402  may coincide with the distal-most end of the bolt  200  to which the nock  300  is installed. In this case, the distal-most end would be the same as the rear surface  404 , and surface  410  is located at substantially the same axial position as rear surface  404 . 
         [0078]      FIGS. 5A-5D  show another embodiment of a nock  302  having lobes  500  and a body portion  502 . This nock  302  may have a concave rear surface  504  (see the recessed rear surfaces  504  in  FIGS. 5B and 5D ) and a plurality of flat rear surfaces  505 . When the bolt  200  having nock  302  is loaded onto the crossbow  100 , the bowstring  120  may contact the outer edges of the concave rear surface  504  in the general position of the bowstring  120  in  FIG. 5D . Thus, the bowstring  120  may contact the edges  506  of the body portion  502  and the edges  507  of two of the lobes  500  that are not being used as the index lobe. Because only the edges  506 ,  507  are in contact with the bowstring  120 , the bowstring  120  may be less likely to slide relative to the nock  302  while they remain in contact with each other. The curvature of these edges  507  may form a cylindrical bowstring contact surface, meaning they follow a cylindrical profile or may curve in a manner following the curvature of a cylindrical bowstring surface. 
         [0079]    When the bolt  200  is loaded, the flat rear surfaces  505  may be positioned rearward relative to the front-most surface of the bowstring  120  (e.g., the surface that contacts the nock  302 ). See also  FIGS. 10E, 12F, and 12I . Thus, the bowstring  120  may contact the edges  507  of the lobes  500  and may be held behind the nock  302  so that there is minimal verticalmovement of the bowstring  120  relative to the rear surface  504 . 
         [0080]    The lobes  500  of nock  302  may have side surfaces  508  that radially taper from the body portion  502  up to the radial tips  510  of the lobes  500 . Thus, the side surfaces  508  may be convex and may meet each other along a curved longitudinally-oriented edge  512 . These lobes  500  may therefore have a smoother aerodynamic profile and use less material than the lobes  400  of  FIGS. 4A-4D . The longitudinally-oriented edge  512  may also be used as a contact surface for the anti-dry fire mechanism of  FIGS. 12A-12K . 
         [0081]      FIGS. 6A-6D  show another embodiment of a nock  304  with lobes  600  and a body portion  602 . The rear surface  604  of the body portion  602  is flat, and the rear surfaces  605  of each of the lobes  600  are partially flat as well. Lofted, curved surfaces  606  on the rear of the nock  302  may connect the rear surface  604  of the body portion  602  to the flat rear surfaces  605  of the lobes  600 . When a bolt  200  with nock  304  is loaded next to a bowstring  120 , the bowstring  120  may extend into contact with the rear surface  604  of the body portion  602  and the edges  607  of the lofted, curved surfaces  606  on the lobes  600  that are not being used as the index lobe. Thus, the curvature of the lofted, curved surfaces  606  may be substantially a reverse of the outer curvature of the bowstring  120  that will be used with the nock  304  so that the outer surface of the bowstring  120  is cradled or captured by the curvature of the edges  607  when contacting the nock  304 . This may help provide a secure hold between the nock  304  and the bowstring  120  throughout a bolt launch process. In these embodiments, the bowstring may only be cradled by the curvature of the nock on a top side of the bowstring. 
         [0082]    The lobes  600  also each comprise a flat outer surface  610  that faces radially away from the body portion  602 . These outer surfaces  610  may be used as a contact surface for the anti-dry fire mechanism of  FIGS. 12A-12K . The lobes  600  may also have a smoothly curved front surface  608  that improves aerodynamics of the nock  304 . 
         [0083]      FIGS. 7A-7D  show yet another embodiment of a nock  306  having lobes  700  and a body portion  702 . In this embodiment, the rear surface  704  of the lobes  700  and body portion  702  is entirely flat, similar to the embodiment shown in  FIGS. 4A-4D . In this embodiment, however, the lobes  700  each have a flat outer surface  710  facing radially away from the body portion  702 . These outer surfaces  710  are similar to, and may serve the same purposes as, the outer surfaces  610  of nock  304 . The lobes  700  also have front surfaces  708  that are similar to, and may serve the same purposes as, the front surfaces  608  of nock  304 . 
         [0084]      FIGS. 8A-8D  show another embodiment of a nock  308  having lobes  800  extending from a body portion  802 . Here the rear surface  804  of the body portion  802  is flat and the rear surfaces  806  of the lobes  800  are curved. The rear surfaces  806  may be described as being concave. The lobes  800  may each also have outer surfaces  810  comparable in shape and function to the other outer surfaces  610 ,  710  and front surfaces  808  comparable in shape and function to the other front surfaces  608 ,  708  described previously herein. This nock  308  may have a reduced rear surface area, width, and height compared to nock  304  which may make nock  308  lighter and more aerodynamic than nock  304 . The reduced radial length of the lobes  800  may also help the lobes  800  fit within a loading slot of a crossbow  100  more readily than other embodiments that have greater width and height. 
         [0085]      FIG. 8D  shows a plurality of bowstrings  120   a ,  120   b ,  120   c  oriented in different positions relative to the neck  308 . Each of the bowstrings  120   a ,  120   b ,  120   c  represents a different way that a bowstring may contact the rear of the nock  308  while still allowing one of the lobes  800  to be an index lobe. For example, when a bowstring is positioned in the same position as bowstring  120   a , lobe  800   a  may be the index lobe positioned pointing downward into a flight groove  108 . Likewise, when the bowstring is positioned as bowstrings  120   b  or  120   c , respective lobes  800   b  or  800   c  may be the index lobe positioned in the flight groove  108 . In this manner, there are at least three possible bowstring orientations usable with the nock  308 . Each of these three orientations have longitudinal bowstring seat axes that form a triangle in a plane perpendicular to the longitudinal axis of the nock  308  (i.e., as indicated by the bowstrings  120   a ,  120   b ,  120   c  in  FIG. 8D ). The plurality of bowstring positions shown in  FIG. 8D  is possible in each of the nocks of  FIGS. 4A-11E . Thus, each of them provide at least three different bowstring orientations. 
         [0086]      FIG. 8D  also shows that the lobes  800  not used as the index lobe may contact the bowstring on opposite lateral sides of the projectile (relative to the shaft). For example, if the bowstring is positioned as bowstring  120   a , lobe  800   a  is the index lobe and lobes  800   b ,  800   c  are positioned on opposite lateral sides of the body portion  802  and the shaft  202  of the bolt  200  to which the nock  308  is attached. Because the lobes  800   b ,  800   c  abut the bowstring  120   a  on opposite sides of the shaft, the nock  308  helps prevent axial rotation of the bolt  200  before it separates from the bowstring  120   a . The lobes  800   b ,  800   c  may extend laterally relative to a vertical direction (e.g., at least partially to the left and to the right relative to the vertical direction) when the index lobe  800   a  extends along the vertical direction. For example, when lobe  800   a  is used as the index lobe and is positioned vertically between rails of a crossbow, the other two lobes  800   b ,  800   c  may extend at least partially laterally to the left and right of that vertical direction. 
         [0087]      FIGS. 9A-9D  show another embodiment of a nock  310  with lobes  900  extending from body portion  902 . This nock  310  also has a flat rear surface  904  for the body portion  902  and curved rear surfaces  906  for each of the lobes  900 . The lobes  900  in this embodiment have a radially-extending T-shape or cross-shape wherein a head portion  912  of each lobe  900  is linked to the body portion  902  of the nock  310  by a neck portion  914 . See  FIG. 9D , The head portion  912  of each lobe  900  may be broader than the nock portion  914  in a direction tangent to the outer surface of the body portion  902  or tangent to the outer surface of the shaft  202  of the bolt  200 . In other words, the head portions  912  may be broadened relative to the nock portions  914  in a direction perpendicular to a radial direction that extends from the longitudinal axis of the body portion  902 . Each lobe  900  therefore has an outer surface  910  facing radially away from the body portion  902  and at least one inner surface  916  facing radially inward toward the body portion  902 . The inner surfaces  916  may be referred to as retaining surfaces. The outer surfaces  910  may be at least partially flat and may be used as a contact surface in connection with an anti-dry fire mechanism, as described in further detail below in connection with  FIGS. 12A-12K . 
         [0088]    The spaces between the inner surfaces  916  and the body portion  902  may be configured to receive ridges  936  of the rails  930  of a crossbow  100 .  FIG. 9E  shows an example embodiment wherein a T-shaped lobe  900  is positioned between rails  930  with a keyway groove  932  extending therebetween. The keyway groove  932  may have notches or grooves  934  in which the lobe  900  is seated and may have ridges  936  that fit between the body portion  902  and the inner surfaces  902  of the nock  310 . In this manner, the rails  930  may be configured to interlock with the rails  110 . By receiving the lobes  900  in a keyway groove  932 , the nock  310  may help prevent the bolt  200  from moving vertically away from the rails  930  before or during launch. 
         [0089]    In the embodiment of  FIGS. 9A-9D , the head portion  912  of each lobe  900  is spaced away from the body portion  902  by the neck portion  914  at the rear of the nock  310  and connects to the body portion  902  at a more forward position on the body portion  902 . See  FIGS. 9A-9B . In other cases, the head portion  912  may be spaced away by a neck portion at the front end of the head portion  912  as well. 
         [0090]      FIGS. 10A-10E  show another nock  312  with lobes  1000  that extend from a body portion  1002 . This nock  312  is comparable to nock  302  in many ways, but has smaller lobes  1000  that decrease the height and weight of the nock  312  and may help the nock  312  more easily fit into the proximal end of a crossbow  100 . The rear surface  1004  of the body portion  1002  is also flat, unlike the concave rear surface  504  of nock  302 . The lobes  1000  each have an outer ridge  1010  that runs longitudinally along their front and outer surfaces. As described in further detail below, the outer ridges  1010  may be used as contact surfaces for the anti-dry fire mechanism of  FIGS. 12A-12K . 
         [0091]      FIG. 10E  in particular shows a side view of the nock  312  showing an exemplary placement of a bowstring  120  relative to the nock  312  when the nock  312  is loaded onto a crossbow  100 , This view shows, for example, how the bowstring  120  may contact edges  1007  of the lobes  1000  and the flat rear surface  1004  simultaneously and how the front surface  1003  of the bowstring  120  may be positioned further forward than the rear surfaces  1005  of the lobes  1000 . A bowstring  120  may be comparably positioned adjacent the other nocks disclosed herein. 
         [0092]      FIGS. 11A-11E  show yet another nock  314  for a bolt  200  that has three lobes  1100  extending circumferentially spaced around a body portion  1102 . The lobes  1100  of this nock  314  extend radially away from the body portion  1102  to a lesser distance than previous embodiments described herein, thereby improving aerodynamics of the nock  314  and making it have a smaller profile that can more easily be loaded between proximal slots of a typical crossbow  100 . The smaller lobes  1100  may also allow the nock  314  to be used with a wider variety of bolts  200 , such as, for example, bolls with short vanes. Smaller lobes  1100  also may decrease friction against the rails  110  or flight groove  108  of a crossbow  100 . 
         [0093]    The lobes  1100  extend rearward from a flat rear surface  1104  of the body portion  1102  and they have curved surfaces  1106  that are linked to the flat rear surface  1104 . The outer surfaces  1110  of the lobes  1100  are curved but may be used as contact surfaces for the anti-dry fire mechanism of  FIGS. 12A-12K . The outer surfaces  1110  are also notable for being smooth and without any sharp edges (e.g., the edge of radial tip  510  of nock  302 ) or ridges (e.g., the edge  409  between the front surface  406  and side surface  408  of nock  300 ). 
         [0094]    Nock  314  also has rounded rear edges  1107 ,  1109  that have higher curvature than the rear edges of other nock embodiments shown herein. The higher curvature may make the lobes  1100  more resistant to chipping or manufacturing flaws and may reduce the overall amount of material needed to construct the nock  314 . The higher curvature may also allow the nock  314  to better retain a bowstring with a large diameter due to forming an inner radius of the rear edges that is substantially the same as the diameter of the larger bowstring. 
         [0095]    Referring now to  FIGS. 12A-12K , an anti-dry fire (ADF) mechanism  1200  and bolt detection system is shown according to another embodiment of the present disclosure. The ADF mechanism  1200  may operate using any of the nocks of  FIGS. 4A-11E  described above. For illustrative purposes, however, the ADF mechanism  1200  is shown in these figures with a bolt  200  that is using nock  312  of  FIGS. 10A-10E . Thus, it will be understood that the principles described in connection with the ADF mechanism will apply to other nocks that have lobes as well as the one shown as an example in these figures. 
         [0096]    The ADF mechanism  1200  may be part of a firing mechanism of a crossbow (e.g., crossbow  100 ). In these figures, the stock or handle of the crossbow is not shown, but the firing mechanism may be housed within a handle or stock. The ADF mechanism  1200  may comprise a string retaining member  1202 , a release member  1204 , and an ADF member  1206  (i.e., a nock contact member). The string retaining member  1202 , release member  1204 , and ADF member  1206  may each be pivotally connected to the stock or handle of the crossbow by pivot points  1208 ,  1210 , and  1212 , respectively. 
         [0097]      FIGS. 12A-12K  each show a different step in a bolt detection and launching process. Starting in  FIG. 12A , the crossbow is unloaded and the bowstring  120  is not in a fully cocked position. Thus, the bowstring  120  and bolt  200  are entirely positioned forward of the string retaining member  1202 . The release member  1204  is in a first position wherein it is in contact with a holding surface  1214  on the string retaining member  1202 . The ADF member  1206  is also in a locked position wherein a holding surface  1216  on the ADF member  1206  is in contact with the release member  1204  and a contact portion  1218  of the ADF member  1206  is not in contact with the bolt  200 . 
         [0098]      FIG. 12B  shows the bowstring  120  partially loaded into the ADF mechanism  1200 . The string retaining member  1202  is rotated around pivot point  1208  to accommodate the rearward movement of the bowstring  120 . As the bowstring  120  continues to move rearward, the string retaining member  1202  will continue to rotate until the bowstring  120  passes over the string retaining member  1202 , at which point the string retaining member  1202  returns to its first position, the bowstring release prevention position, as shown in  FIG. 12C . To complete this process, the string retaining member  1202  may in some embodiments be spring loaded around the pivot point  1208  such that the string retaining member  1202  is biased back to its first position once the bowstring  120  passes over it. Once the bowstring  120  is in the position of  FIG. 12C , it is kept from moving forward (i.e., retained) by the string retaining member  1202  since the holding surface  1214  is in contact with the release member  1204 , which prevents further counterclockwise rotation of the string retaining member  1202 . At this point, the crossbow may be referred to as being cocked and ready for the bolt  200  to be loaded. 
         [0099]    In the position of  FIG. 12C , the holding surface  1216  of the ADF member  1206  stays in contact with the release member  1204  and thereby prevents rotation of the release member  1204  to a position out of contact with the holding surface  1214  of the string retaining member  1202 . Thus, the interference of the string retaining member  1202 , release member  1204 , and ADF member  1206  prevents the string retaining member  1202  from moving and allowing the bowstring  120  to be released without a bolt  200  being loaded (i.e., prevents a dry fire of the crossbow  100 ). 
         [0100]      FIGS. 12D-12F  illustrate the bolt  200  loading process. Between the positions of  FIGS. 12C and 12D , the bolt  200  moves rearward (e.g., by sliding on the rails  110 ) until the nock  312  comes into contact with the contact portion  1218  of the ADF member  1206 , as shown. in  FIG. 12D . The contact portion  1218  of the ADF member  1206  may have an angled or sloped surface  1220  that makes first contact with the lobe being used as the index lobe of the nock  312 . In  FIG. 12D , the ADF member  1206  has not yet rotated. 
         [0101]      FIG. 12E  shows the ADF mechanism  1200  after the bolt  200  has moved further rearward and partially through the string retaining member  1202 . The index lobe of the nock  312  has pressured the sloped surface  1220  of the ADF member  1206  enough to cause the ADF member  1206  to rotate around its pivot point  1212  and to give way to the nock  312  to allow the outer ridge  1010  of the nock to slide along a detection surface  1222  on the top of the ADF member  1206 . The rotation of the ADF member  1206  also causes the holding surface  1216  of the ADF member  1206  to move out of contact with the release member  1204 , but the bowstring  120  remains retained by the string retaining member  1202  due to contact of the holding surface  1214  of the string retaining member  1202  with the release member  1204 . 
         [0102]    The detection surface  1222  may be called a detection surface because while the index lobe of the nock  312  is in contact with the detection surface  1222 , the ADF mechanism  1200  detects the presence of a bolt  200  loaded into the crossbow  100 . If the bolt  200  is pulled forward and out of this position, the ADF member  1206  may rotate back into the position of  FIG. 12D  to prevent dry fire of the crossbow  100 . In some embodiments, the ADF member  1206  is biased toward that position in order to help automatically prevent dry fires. 
         [0103]    In some embodiments, the crossbow  100  may be designed so that the sloped surface  1220  and/or detection surface  1222  are positioned at a predetermined vertical distance below the top of the rails  110  and within the flight groove  108  of the crossbow  100 . This predetermined vertical distance may correspond with a height of an index lobe relative to the surface of the shaft  202  of the bolt  200 . Thus, a bolt loaded into the crossbow  100  would need to have an index lobe on its rear end in order for the crossbow  100  to launch the bolt since a conventional bolt nock would not extend downward that predetermined vertical distance and make contact with the ADF member  1206 . Consequentially, the lobe of the nock  312  also provides automatic longitudinal position detection of the bolt  200  since the bolt  200  would need to be in contact with the detection surface  1222  at a specific longitudinal position in order for the ADF mechanism  1200  to detect the bolt  200 . The crossbow  100  would not be able to shoot the bolt  200  without the ADF mechanism  1200  detecting the bolt  200 . 
         [0104]    In the position shown in  FIG. 12F , the bolt  200  is fully loaded. The nock  312  is in contact with the bowstring  120  and the ADF member  1206  is rotated with the holding surface  1216  out of the path of rotation of the release member  1204  (e.g., when the release member  1204  rotates around pivot point  1210 ). The bowstring  120  may be in contact with one or more of the rear surface  1004  and lobe edges  1007  of the nock  312 . The bowstring  120  and bolt  200  may remain in this loaded position with the ADF member  1206  unlocked until the trigger assembly  104  is actuated by the user. 
         [0105]      FIG. 12F  also illustrates how the lobe edges  1007  may interfere with movement of the bowstring  120  if it tries to slip around the nock  312  and along the shaft  202  of the bolt  200 . A vertical movement of the bowstring  120  would also move the nock  312  upward or downward with the bowstring  120  due to contact with the lobes  1000 , thereby keeping the bowstring  120  cradled or captured behind the nock  312  and able to continue to transfer its potential energy to the bolt  200 . 
         [0106]      FIGS. 12G-12I  illustrate the bolt launching process.  FIG. 12G  shows the state of the ADF mechanism  1200  momentarily after the trigger assembly  104  is pulled. The release member  1204  rotates around its pivot point  1210 , thereby moving out of contact with the holding surface  1214  of the string retaining member  1202 . The tension in the bowstring  120  is applied to the string retaining member  1202 , so the string retaining member  1202  rotates to the position shown in  FIG. 12H . As the bowstring  120  moves forward, it is held against the nock  312  and pushes the bolt  200  forward as well. The string retaining member  1202  continues to rotate out of the way of the bowstring  120  and may eventually reach the position shown in  FIG. 12I . In  FIG. 12I , the bowstring  120  is completely out of contact with the string retaining member  1202 , which has rotated down and out of the way of the bowstring  120  as the bowstring  120  passed over it while propelling the bolt  200  forward. Eventually the tension applied to the bowstring  120  is released, and the bolt  200  is launched away from the crossbow  100  at high velocity. The bowstring  120  remains in contact with the nock  312  from the position shown in  FIG. 12F  until the bowstring  120  stops moving forward. 
         [0107]      FIG. 12J  shows the string retaining member  1202  and ADF member  1206  as they spring back into their first positions, which are shown in  FIG. 12K . Once returning to the position of  FIG. 12K  (which is comparable to the position of  FIG. 12A ), the holding surfaces  1214 ,  1216  remain in contact with the release member  1204  until the crossbow  100  is cocked and loaded over again. 
         [0108]    Various inventions have been described herein with reference to certain specific embodiments and examples, However, they will be recognized by those skilled in the art that many variations are possible without departing from the scope and spirit of the inventions disclosed herein, in that those inventions set forth in the claims below are intended to cover all variations and modifications of the inventions disclosed without departing from the spirit of the inventions. The terms “including” and “having” come as used in the specification and claims shall have the same meaning as the term “comprising.”