Abstract:
A projectile launcher includes an acceleration rail with an accelerator mounted on opposite sides of the rail. Each accelerator includes an elastomeric energy generator having an end that is held stationary, while another end is connected to a string. This string then passes over a series of pulleys and crosses over the rail into the other accelerator. Thus, both accelerators act on the same string. In operation, as the string is pulled back and engaged with the projectile on the acceleration rail, the elastomeric drives are stretched. Also, each series of pulleys effectively causes a velocity multiplication that enhances the momentum of the projectile when it is launched.

Description:
[0001]    This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/324,209, filed Apr. 14, 2010. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention pertains generally to man-powered weapons. More particularly, the present invention pertains to weapons that allow an individual to configure the weapon with their own physical strength, to thereby establish sufficient energy for effectively launching projectiles with a momentum required for activities such as “big game” hunting. The present invention is particularly, but not exclusively, useful as a man-powered weapon that can be handled, aimed and operated with enhanced power and accuracy. 
       BACKGROUND OF THE INVENTION 
       [0003]    All man-powered weapons rely on the inherent capability of the weapon to be operationally armed by an individual. Essentially, this means that a single individual must be able to, somehow, reconfigure or manipulate the weapon so that it has sufficient potential energy to effectively launch a projectile. In particular, no chemical reaction, such as the explosion of gun powder, is involved in the operation of a man-powered weapon. Traditionally, man-powered weapons have generally included air-pump guns, slings, blow-guns, bow-and-arrow sets, and crossbows. Of these, the bow-and-arrow and crossbow have clearly been the most versatile and powerful. And, of these, the crossbow is arguably the most powerful. A traditional crossbow, however, has its shortcomings. Most notably, a traditional crossbow is front-end heavy and, consequently, is somewhat difficult to manipulate during hunting. 
         [0004]    An important consideration of any man-powered weapon is its mechanical compatibility with the projectile that is to be launched. The follow-on consideration from this involves the efficacy of the projectile itself. Recent studies have indicated that, in a hunting context, the momentum of a projectile is often more important than its velocity. A generalized consequence of this observation is that for an elongated projectile, the center of mass needs to be nearer the front end of the projectile. Further, for improved accuracy, it is preferable that the percent of projectile mass which is Forward of Center (% FOC) be around 25% or greater. Mathematically, where “center” is taken to be the balance point of the projectile, where “L” is the length of the projectile&#39;s shaft (aft of the broadhead), and where “x” is the distance from the tail end of the projectile to center, the % FOC can be calculated using the expression: 
         [0000]      % FOC=( x/L− ½)100
 
         [0000]    From the above, it then follows that the weapon (i.e. launcher) must effectively accommodate such a projectile. 
         [0005]    For purposes of hunting “big game”, or even small game for that matter, silence is a valued capability for a man-powered weapon. More specifically, it is desirable that a man-powered weapon have minimal, if any, report. Equally important is the ability of a hunter (user) to handle and aim the weapon easily and accurately. For a rifle or shotgun, this ability is essentially an inherent characteristic of the weapon. As implied above, with reference to a traditional crossbow, this is not necessarily so for a man-powered weapon. 
         [0006]    In light of the above, it is an object of the present invention to provide a man-powered projectile launcher having increased accuracy. Still another object of the present invention is to provide a man-powered launcher that is capable of shooting a projectile with high momentum. Yet another object of the present invention is to provide a projectile launcher that is rugged and relatively noiseless, i.e. it has good mechanical and acoustic containment. A further object of the present invention is to provide a projectile launcher that is relatively simple to manufacture, is easy to use, and is comparatively cost effective. 
       SUMMARY OF THE INVENTION 
       [0007]    A projectile launcher in accordance with the present invention provides a high momentum launch for projectiles using at least one elastomeric drive unit. An important feature of the invention is the incorporation of a launcher design that can be made to either push or pull the projectile for acceleration during launch. Another important feature is the noise suppression that is provided by the launcher design. 
         [0008]    Structurally, the projectile will preferably include a projectile head with a long, straight cylindrical shaft extending from the head. The projectile launcher itself includes an elongated base member that is formed with an acceleration rail. And, a sled is mounted on the base member for reciprocal linear movement along the acceleration rail. The sled is configured to receive the head portion of the projectile and, preferably, the head portion of the projectile is magnetically held on the sled. In any event, an engagement of the head of the projectile with the sled must stabilize the projectile on the sled until the projectile has been launched. 
         [0009]    In addition to the acceleration rail, a preferred embodiment of the launcher includes a pair of accelerators. More specifically, a first accelerator is mounted on one side of the base member, and a second accelerator is mounted on the other side of the base member, opposite the acceleration rail from the first accelerator. A string is provided, and a first end of the string is affixed to a stationary point on the first accelerator. Similarly, a second end of the string is affixed to a stationary point on the second accelerator. Within this arrangement, the string crosses over the acceleration rail between the first accelerator and the second accelerator. As the string crosses the acceleration rail it is engaged with the sled. 
         [0010]    An important feature of the present invention is that each accelerator is housed inside a noise-suppression tube. For this feature, each noise-suppression tube is a hollow structure, and it has a base end and a deployment end. The base end of each noise-suppression tube is pivotally mounted on opposite sides of the base member as implied above. Within this structure, each accelerator includes an elastomeric drive unit. Inside each respective noise-suppression tube, a first end of the drive unit is affixed to the base end of the tube, and a velocity multiplier pulley is attached to the second end of the drive unit. Importantly, the velocity multiplier pulley is attached for movement with the second end of the drive unit. The accelerator also includes an external deployment pulley that is fixedly attached to the deployment end of the noise-suppression tube. With this structure, an end of the string is affixed to the deployment end of the noise-suppression tube. The string then extends through the interior of the noise-suppression tube for successive engagements with the velocity multiplier pulley and the external deployment pulley. The string then exits from the noise-suppression tube for its engagement with the sled on the acceleration rail of the base member. 
         [0011]    In addition to the structure disclosed above, each accelerator also includes a rigid truss member that facilitates arming and firing the launcher. In detail, the truss member has a first end that is pivotally attached to the deployment end of the noise-suppression tube. The truss member also has a second end that is engaged with the base member, to slide along the base member between a first location and a second location. With a movement of the second end of the truss member from its first location to its second location, the accelerator is reconfigured from an unloaded configuration to a pre-load configuration. In its unloaded configuration, the noise-suppression tube is substantially parallel to the base member. In its pre-load configuration, however, the noise-suppression tube is pivoted at its base end to establish an angle φ between the noise-suppression tube and the acceleration rail of the base member. The consequence of this reconfiguration is that the drive unit is stretched from an unloaded state and into a pre-load state. 
         [0012]    With the accelerators of the projectile launcher in a pre-load state, an arming of the launcher is accomplished by pulling the sled back along the acceleration rail to an armed-for-launch (i.e. loaded) position that is located near the base ends of the accelerators. By positioning the sled in this armed position on the acceleration rail, both accelerators are simultaneously activated. If not already engaged, the head of the projectile can then be placed on the sled. For launch, a trigger releases the sled from the armed (loaded) position and this pulls on the head portion of the projectile to release useful stored energy for launching the projectile. 
         [0013]    In an alternate embodiment of the present invention, a single accelerator can be used. For this embodiment, instead of the string passing through the sled for its engagement with the sled, the string is attached directly to the sled. A braking mechanism for the sled is provided for this embodiment. 
         [0014]    An adaptation of the present invention that employs the concepts of a compound bow involves a three-string structure for use with the accelerators. Specifically, this embodiment of the invention employs a single draw string that extends between the deployment ends of the accelerators. And, it employs a separate drive string for each accelerator. Further, for this embodiment, each accelerator incorporates a dual cam that is mounted for rotation at the deployment end of each respective noise-suppression tube. Structurally, each dual cam includes a drive cam that is affixed and juxtaposed to a draw cam. Importantly, the drive cam and the draw cam are affixed to each other, for rotation with each other. Within this structure, the draw string is engaged between respective draw cams of the two accelerators, and each separate drive string is engaged between a drive cam and a respective drive unit in the noise-suppression tube of the accelerator. During a pull on the draw string, the draw cam radius increases non-linearly, while the drive cam radius decreases at the end of the draw. Together, these simultaneous actions achieve a combined action similar to a compound bow. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which: 
           [0016]      FIG. 1  is a perspective view of the projectile launcher in accordance with the present invention with portions broken away for clarity; 
           [0017]      FIG. 2A  is a top plan view of the projectile launcher in an unloaded configuration; 
           [0018]      FIG. 2B  is a top plan view of the projectile launcher in a pre-load configuration; 
           [0019]      FIG. 3A  is a schematic representation of the accelerators of the projectile launcher in a pre-load condition; 
           [0020]      FIG. 3B  is a schematic representation of the accelerators of the projectile launcher in a loaded condition showing both a “pull” and a “push” configuration for the launcher; 
           [0021]      FIG. 4  is a graph showing the relationship between string extension and string tension for various conditions of the accelerators; 
           [0022]      FIG. 5  is a schematic representation of an alternate embodiment of the projectile launcher having a single accelerator configured for a “pull” action on the projectile; and 
           [0023]      FIGS. 6A-C  illustrate a sequence of configurations for dual-cam accelerators when employed to achieve a compound bow action. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0024]    Referring initially to  FIG. 1 , a projectile launcher in accordance with the present invention is shown and is generally designated  10 . As shown, the launcher  10  includes a base member  12  that is formed with an acceleration rail  14 . Further, a sled  16  is shown mounted on the acceleration rail  14  for reciprocal movement thereon. A projectile is also shown in  FIG. 1 , with the projectile having a projectile head  18 , with an elongated projectile shaft  20  extending from the projectile head  18 . More specifically, the projectile head  18  is shown engaged with the sled  16 . Preferably, this engagement is accomplished magnetically. 
         [0025]    Still referring to  FIG. 1 , it will be seen that the launcher  10  includes a pair of accelerators  22   a  and  22   b . In detail, the accelerators  22   a  and  22   b  each include a noise suppression tube  24  and they are positioned on opposites sides of the base member  12 . Using the accelerator  22   a  as an example for disclosure purposes, it will be seen that the accelerator  22   a  has a base end  26  and a deployment end  28 . As shown, the base end  26  of the accelerator  22   a  is mounted on the base member  12  for rotation between an unloaded configuration (see  FIG. 2A ) and a pre-load configuration (see  FIG. 2B ). In the unloaded configuration for launcher  10  ( FIG. 2A ), the accelerators  22   a  and  22   b  are aligned substantially parallel to the base member  12 . On the other hand, in the pre-load configuration for launcher  10  ( FIG. 2B ), the accelerators  22   a  and  22   b  are each pivoted at their base end  26  and are splayed to establish an angle “φ” between the respective accelerators  22   a  and  22   b  and the base member  12 . 
         [0026]    Still referring to  FIG. 1 , and still using the accelerator  22   a  as an example, within the noise suppression tube  24  it will be seen that the accelerator  22   a  includes a drive unit  30  that is preferably made of a stretchable elastomeric material. It could, however, be made as a spring or as some other type mechanism known in the pertinent art that will store energy when stretched. In any event, one end of the drive unit  30  is fixed at the base end  26  of the accelerator  22   a , and the other end of the drive unit  30  is fixed to a velocity multiplier pulley  32 .  FIG. 1  also indicates that a deployment (base) pulley  34  is mounted on the accelerator  22   a  at its deployment end  28 . 
         [0027]    As perhaps best seen in  FIG. 3A , the launcher  10  includes a launching string  36  that is interconnected between the deployment end  28  of the accelerator  22   a , and the deployment end  28 ′ of the accelerator  22   b . More specifically, for this interconnection the string  36  is fixed at the deployment end  28  of accelerator  22   a  and extends therefrom for engagement with the velocity multiplier pulley  32 . It then extends back from the velocity multiplier pulley  32  to the deployment (base) pulley  34 . After the string  36  exits from the accelerator  22   a  at the deployment (base) pulley  34 , it then crosses over the acceleration rail  14  where it engages with the sled  16 . From the sled  16 , the string  36  enters the accelerator  22   b . The string  36  then successively engages with deployment (base) pulley  34 ′ and velocity multiplier pulley  32 ′ before it is fixed at deployment end  28 ′ of accelerator  22   b . Within the accelerator  22   b , the drive unit  30 ′ interconnects the velocity multiplier pulley  32 ′ with base end  26 ′ in the same manner as corresponding components are incorporated in accelerator  22   a . In comparison with  FIG. 3B ,  FIG. 3A  shows the string  36  as it will be deployed when the launcher  10  is in a pre-load configuration. On the other hand,  FIG. 3B  shows the string  36  in a configuration wherein the launcher  10  is armed. With reference to  FIG. 3B , it is to be appreciated that in an alternate embodiment of the launcher  10  the string  36  can be engaged with a nock (not shown) at the rear of projectile shaft  20 . For this embodiment, the projectile head  18  is launched with a pushing action and does not necessarily require use of the sled  16 . In any event, it will be appreciated by the skilled artisan that a “push” or a “pull” action can be accomplished with or without a sled  16 . 
         [0028]    Returning to  FIG. 1 , it will be seen that the launcher  10  also includes a pair of truss members  38   a  and  38   b  that, respectively, support the accelerators  22   a  and  22   b  on the base member  12 . With reference to  FIGS. 2A and 2B , it will be seen that these truss members  38   a  and  38   b  are substantially aligned with the base member  12  when the launcher  10  is unloaded ( FIG. 2A ). When the launcher  10  is placed in its pre-load configuration however ( FIG. 2B ), the truss members  38   a  and  38   b  are splayed to interconnect the deployment ends  28  of the accelerators  22   a  and  22   b  with the base member  12 . Thus, in operation, the truss members  38   a  and  38   b  support and stabilize the accelerators  22   a  and  22   b  during a firing of the launcher  10 . 
         [0029]    An operation of the launcher  10  will be better appreciated with reference to  FIG. 4 . In detail, the graph line  40  in  FIG. 4  shows the relationship between the extensions of the drive unit  30  and the resultant tension force that are thereby generated in the drive unit  30 . As will be appreciated by the skilled artisan, the area under this graph line  40  between points  44  and  46  is indicative of the useful energy (i.e. potential energy) that is stored in the drive unit  30 . With this in mind, an operation of the launcher  10  starts with an unloaded launcher  10 , in a configuration as shown in  FIG. 2A . This unloaded configuration corresponds to a nominal extension of the drive unit  30  and generally corresponds to the point  42  indicated in  FIG. 4 . It is an important aspect of the present invention that this unloaded configuration still imparts a tension on the drive unit  30 . Specifically, the slight tension of the unloaded configuration avoids adverse effects of hysteresis. From this start point, i.e., the unloaded configuration, it will be appreciated that the pre-load can actually be performed either before or after the full load configuration. 
         [0030]    From an unloaded configuration, the accelerators  22   a  and  22   b  are then splayed, along with the truss members  38   a  and  38   b , to reconfigure the launcher  10  into its pre-load (operational) configuration as shown in  FIG. 2B . This pre-load (operational) configuration ( FIG. 2B ) corresponds to a short extension of the drive unit  30  as indicated by point  44  in  FIG. 4 . Note: for purposes of disclosure, when the launcher  10  is in its pre-load (operational) configuration ( FIG. 2B ), the string  36  is positioned substantially as shown in  FIG. 3A . Loading (i.e. arming) the launcher  10  simply requires withdrawing the sled  16  along the acceleration rail  14 , and engaging the projectile head  18  with the sled  16 . Or, as disclosed below, the projectile shaft  20  can be engaged directly with the string  36 . In either case, after the launcher  10  has been loaded (i.e. armed), the string  36  will be positioned substantially as shown in  FIG. 3B . This corresponds to the point  46  in  FIG. 4 . The launcher  10  can then be fired by manipulation of the trigger mechanism  48  (see  FIG. 1 ). As will be appreciated by the skilled artisan, a withdrawal of the sled  16  (string  36 ) to arm the launcher  10  can be accomplished in any manner well known in the pertinent art, such as manually, with toothed belt and pulley, quick-release lead screws, a compact winch, a bicycle-style chain, or multi-stepping sheep&#39;s foot. 
         [0031]    With reference to  FIG. 5 , it will be appreciated that the present invention envisions variations in embodiments of mechanisms that operate in lieu of the pair of accelerators  22   a  and  22   b  disclosed above. Specifically, for the embodiment shown in  FIG. 5 , a single accelerator  22  may be used. In this embodiment, the acceleration rail  14  can be narrowed at its distal end to provide a breaking action for the sled  16 . In another variation, a mechanism is provided that incorporates structure having the arming characteristics of a compound bow. Such an embodiment for the present invention is shown in  FIGS. 6A-C . 
         [0032]    In  FIG. 6A , a dual cam mechanism  50  is shown to include a cam plate  52  on which are mounted both a power cam  54  and a launch cam  56 . Importantly, both of the cams  54  and  56  rotate together with the cam plate  52 .  FIG. 6A  also shows that a launcher  10  that incorporates a cam mechanism  50  will typically also incorporate a corresponding cam mechanism  50 ′. For purposes of disclosure, the cam mechanism  50  will be described and considered exemplary of other such mechanisms (i.e. cam mechanism  50 ′). 
         [0033]    Along with the power cam  54  and the launch cam  56 ,  FIG. 6A  shows that cam mechanism  50  includes a power line  58  interconnecting the power cam  54  with the drive unit  30 . It is also shown that the cam mechanism  50  includes a launch line  60  interconnecting the launch cam  56  of cam mechanism  50  with the launch cam  56 ′ of cam mechanism  50 ′. Further, the launch line  60  is shown crossing the acceleration rail  14  and engaging with the sled  16 . Consequently, when the sled  16  is withdrawn along the acceleration rail  14 , the launch line  60  is guided by the launch cams  56  to simultaneously rotate the respective cam plates  52  and  52 ′ of the mechanisms  50  and  50 ′. As the cam plates  52  and  52 ′ rotate, the power cams  54  on each cam plate  52  also rotate and pull on their respective power lines  58 . This causes the drive units  30  to extend (see  FIGS. 6B and 6C  sequentially) and thereby store energy for the subsequent launch of a projectile (not shown in  FIGS. 6A-C ). 
         [0034]    While the particular Projectile Launching Device as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims. 
         [0035]    An important consideration of any man-powered weapon is its mechanical compatibility with the projectile that is to be launched. The follow-on consideration from this involves the efficacy of the projectile itself. Recent studies have indicated that, in a hunting context, the momentum of a projectile is often more important than its velocity. A generalized consequence of this observation is that for an elongated projectile, the center of mass needs to be nearer the front end of the projectile. Further, for improved accuracy, it is preferable that a measure of the location for the center of mass, referred to as the percent Forward of Center (% FOC), be around 25% or greater. Mathematically, where “L” is the length of the projectile&#39;s shaft (aft of the broadhead), and where “x” is the distance from the tail end of the projectile to center, the % FOC can be calculated using the expression: 
         [0000]      % FOC=( x/L− ½)100
 
         [0000]    From the above, it then follows that the weapon (i.e. launcher) must effectively accommodate such a projectile.