Abstract:
The present invention is a modular gunstock utilizing a two-piece mounting structure and a stock module. The structure comprises a weapon attachment, in the case of an AR15/M16 rifle a receiver extension tube, and a sleeve slidable over said attachment and containing mounting structure for the stock module. The disclosed stock module is adjustable for length and features a length pre-set system, a latch with independent dual-pawls and an integrated impact buffer, modular tailpiece, and storage. The sleeve also features a position selectable fixed cheek plate.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
   This Application claims priority on prior filed U.S. Provisional Application No. 60/889,244, filed Feb. 9, 2007 and incorporates the same by reference in its entirety. 

   FIELD OF THE INVENTION 
   The present invention relates to the field of firearms and more particularly relates to a gunstock with enhanced modularity and adjustment functions. 
   BACKGROUND OF THE INVENTION 
   Gunstocks or “buttstocks” as they are commonly known, are well known in the art of firearms. These devices have been used with “long arms” as a means for resting and securing the weapon against the shoulder of the user when firing. Gunstocks have also been used as a weapon in and of themselves in a melee fight. As such, gunstocks have been developed along many different shapes and designs and using various materials to increase durability, reduce the effects of recoil, or “kick”, provide adjustability and customization, increase shooter accuracy, provide storage for gear, and other goals too myriad to mention. 
   One recent goal, however, is to provide a modular gunstock such that a single stock, or portion of a stock, may be used as a platform upon which user customizations may be mounted. However, previous modular gunstocks present a number of difficulties. The first of which is that the mounting components for such systems tends to be bulky, as they contain additional mounting features not present in other stocks. Second, a structural failure in a mounting component tends to render the weapon useless until a costly part is replaced. As such, a new modular gunstock is needed that presents a lower profile, with a simpler mounting paradigm, and is cost effective to replace in the event of structural failure. 
   The present invention is a modular gunstock that provides a two-piece mounting platform as a new modular paradigm. The present invention represents a departure from the prior art in that the modular gunstock of the present invention allows for a durable two-piece mounting platform upon which stock options may be mounted. As a two-piece platform, the design draws upon the inherent strength of having two or more pieces working on concert, a layering approach, and also allows for the replacement of one of such pieces should either fail with lesser cost both to the user and the manufacturer. 
   The present invention is described as a preferred embodiment with an adjustable for length stock attachment. Particular problems with such systems include lack of stability, insufficient strength, and cheek weld disruption where the pieces join. 
   SUMMARY OF THE INVENTION 
   In view of the foregoing disadvantages inherent in the known types of modular gunstocks, this invention provides a new modular gunstock utilizing a two-piece mounting platform. As such, the present invention&#39;s general purpose is to provide a new and improved modular gunstock that is durable, lower cost and achieves the goal of modular customization with greater efficiency. To these ends, the modular gunstock comprises a receiver extension tube, or “buffer tube”, upon which a sleeve is slid into place and secured to the tube by conventional means. The sleeve has on its external surface mounting hardware for the remainder of the stock, in the form of a rail. Other hardware is provided to provide interface with the remainder of the weapon. Since the modular gunstock is primarily mounted upon a buffer tube, it presents an instant advantage over prior modular systems and earlier carbine systems as previous systems had to be “timed” to properly engage the receiver with their interface when screwed into the receiver. This modular system required no such estimation. It should be noted that the gunstock as depicted is for a U.S. standard M-16/AR-15 style rifle. However, it should be appreciated that other weapon platforms which use a gunstock will benefit from the present invention and that the only changes necessary will be in the interface of the stock with the weapon. As such, such changes should be read into and considered as a within the scope of this invention. 
   Other features of this gunstock, as disclosed in the preferred embodiment, include an adjustable for length stock with a quick extension pre-set system and a dual, independent pawl latch. The adjustable for length stock also features a shock cushion for the latching mechanism, so as to minimize kick and bludgeon shock to the latch, a storage compartment, a modular tail-piece and a customizable fixed cheek piece. It should also be appreciated that this disclosure is only describing one possible stock module to interface with the system that is the invention. Other stock types, including fixed stocks and precision shooting stocks, may be manufactured for this system and still be considered within the scope of this invention. 
   The more important features of the invention have thus been outlined in order that the more detailed description that follows may be better understood and in order that the present contribution to the art may better be appreciated. Additional features of the invention will be described hereinafter and will form the subject matter of the claims that follow. 
   Many objects of this invention will appear from the following description and appended claims, reference being made to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views. 
   Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting. 
   As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a left plan view of the gunstock using an adjustable for length stock module. 
       FIG. 2  is a cross-sectional view of the stock of  FIG. 1 . 
       FIG. 3  is a perspective view of the gunstock&#39;s extension tube module installed on an AR-15 lower receiver. 
       FIG. 4  is a perspective view depicting the gunstock&#39;s sleeve module installed. 
       FIG. 5  is a perspective view of the assembled mounting structure&#39;s underside. 
       FIG. 6  is a right plan view of the assembled mounting and the length of pull preset system, taken when the stock (not shown) is in a collapsed position. 
       FIG. 6   a  is a bottom plan view of the system depicted in  FIG. 6 . 
       FIG. 6   b  is a sectional view, taken along line B-B of  FIG. 6 . 
       FIG. 6   c  is a rear plan view of the system depicted in  FIG. 6 . 
       FIG. 7  is a right plan view of the assembled mounting and the length of pull preset system, taken when the stock (not shown) is in an extended to the pre-set position. 
       FIG. 7   a  is a bottom plan view of the system depicted in  FIG. 7 . 
       FIG. 7   b  is a sectional view, taken along line B-B of  FIG. 7 . 
       FIG. 7   c  is a rear plan view of the system depicted in  FIG. 7 . 
       FIG. 8  is a right plan view of the assembled mounting and the length of pull preset system, taken when the stock (not shown) is in an extended to the pre-set position and the release latch is biased to avoid the pre-set. 
       FIG. 8   a  is a bottom plan view of the system depicted in  FIG. 8 . 
       FIG. 8   b  is a sectional view, taken along line B-B of  FIG. 8 . 
       FIG. 8   c  is a rear plan view of the system depicted in  FIG. 8 . 
       FIG. 9  is a right plan view of the assembled mounting and the length of pull preset system, taken when the stock (not shown) is in a position between the pre-set and the end stop, maintaining the latch bias of  FIG. 8 . 
       FIG. 9   a  is a bottom plan view of the system depicted in  FIG. 9 . 
       FIG. 9   b  is a sectional view, taken along line B-B of  FIG. 9 . 
       FIG. 9   c  is a rear plan view of the system depicted in  FIG. 9 . 
       FIG. 10  is a right plan view of the assembled mounting and the length of pull preset system, taken when the stock (not shown) is in an extended position to the end stop, maintaining the latch bias of  FIG. 8 . 
       FIG. 10   a  is a bottom plan view of the system depicted in  FIG. 10 . 
       FIG. 10   b  is a sectional view, taken along line B-B of  FIG. 10 . 
       FIG. 10   c  is a rear plan view of the system depicted in  FIG. 10 . 
       FIG. 11  is a right plan view of the assembled mounting and the length of pull preset system, taken when the stock (not shown) is in an extended position to the end stop, releasing the latch bias of  FIG. 8 . 
       FIG. 11   a  is a bottom plan view of the system depicted in  FIG. 11 . 
       FIG. 11   b  is a sectional view, taken along line B-B of  FIG. 11 . 
       FIG. 11   c  is a rear plan view of the system depicted in  FIG. 11 . 
       FIG. 12  is a right plan view of the assembled mounting and the length of pull preset system, taken when the stock (not shown) is in an extended position to the end stop, reversing the latch bias of  FIG. 8 . 
       FIG. 12   a  is a bottom plan view of the system depicted in  FIG. 12 . 
       FIG. 12   b  is a sectional view, taken along line B-B of  FIG. 12 . 
       FIG. 12   c  is a rear plan view of the system depicted in  FIG. 12 . 
       FIG. 13  is a perspective view of the latch mechanism for the stock, according to the present invention. 
       FIG. 13   a  is a perspective view of the trigger mechanism of the latch depicted in  FIG. 13 . 
       FIG. 13   b  is a perspective view of the trigger mechanism and pawls for the latch of  FIG. 13 . 
       FIG. 14  is a left plan view of the mounting structure, sleeve module, and latch mechanism, without trigger, of the invention. 
       FIG. 15  is a rear plan view of the mounting structure, sleeve module and latch mechanism in a locked state. 
       FIG. 15   a  is a partial sectional view of the system depicted in  FIG. 15 , taken along line A-A. 
       FIG. 16  is a rear plan view of the mounting structure, sleeve module and latch mechanism in an intermediate state. 
       FIG. 16   a  is a partial sectional view of the system depicted in  FIG. 16 , taken along line A-A. 
       FIG. 17  is a rear plan view of the mounting structure, sleeve module and latch mechanism in an unlocked state. 
       FIG. 17   a  is a partial sectional view of the system depicted in  FIG. 17 , taken along line A-A. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   With reference now to the drawings, the preferred embodiment of the modular gunstock is herein described. It should be noted that the articles “a”, “an”, and “the”, as used in this specification, include plural referents unless the content clearly dictates otherwise. 
   With reference to  FIGS. 1 and 2 , the modular gunstock comprises three main components. The first is a weapon mounting structure  12  which is the actual attachment to the weapon (See,  FIG. 3 ). In the case of an AR15/M16 model weapon, the structure is actually a replacement receiver extension tube. However the only requirement is that the mounting structure  12  be cylindrical (either round or polygonal) so that sleeve module  14  may slide over it. As such, references to the mounting structure  12  as being an extension tube should be construed as only relating to this preferred and disclosed embodiment as alteration of the structure for other weapon platforms that do not need a receiver extension tube will be obvious permutations of the present invention and should be read as included within this invention. Weapon mounting structure features actual interfacing structure, in the case of this preferred embodiment a threaded open end  26 , and a threaded nut  24  at its distal end. The preferred embodiment then simply screws onto the weapon&#39;s lower receiver  30 , shown in  FIG. 3 . It should be noted that the key slot  32  is avoided by the invention at this stage. 
   The second component is the sleeve module  14 , which slides over the mounting module  12 , shown in  FIGS. 2 and 4 . ON the lower half of sleeve module  14 , is rail  52  which serves as structure for the stock body. Rail also provides interface structure for yoke  42  and end cap  44 . End cap  44  is attached and keyed into sleeve  14  between two prongs of rail  52 . Bolt  22  is then used to secure end cap  44  to threaded nut  24  on the mounting structure  12 . Sleeve  14  is thereby secured to mounting structure  12  in a manner that prevents rotation. Yoke  42  is positioned at a forward end of sleeve  14 , on rail  52 . It provides structure  41  to key into the receiver&#39;s key slot  32 , thereby preventing rotation in relation to lower receiver  30 . Yoke  42  is secured as a vice, biased by bolt  43 , and may provide additional useful structure as a quick-detach point for certain accessories such as slings. 
   Sleeve module  14  also features a plurality of sets of threaded holes  48   a ,  48   b  along its sides. These holes provide mounting structure for cheek plate  46 , as it is secured by threading bolts  48  into one of each set  48   a ,  48   b  of holes, depending on the location the user desires the cheek plate  46 , as shown. It should be understood that matching sets of holes are ideally placed on the side not shown in the figures. As shown, the sleeve module  14  provides three placement options for positioning the cheek plate  46 . 
   Rail  52 , shown in  FIG. 5 , provides structure for mounting the stock body and contains structure for the pre-set system utilized by stock bodies which are adjustable for length. The length of pull system comprises a series of pre-drilled threaded holes  56 , which are off-set from a center axis of the rail (shown in better detail in  FIG. 6   a ). A stop bolt  54  is provided to interface with whichever hole  56  a user desires. End cap  44  also provides a terminal stop  45 , which is also off-set but opposite holes  56 . Angled detents  58  are provided for pawls in the latch mechanism. 
   The length of pull pre-set system works as follows, shown in  FIGS. 6-12   c . The stock is in a normal state, shown in  FIGS. 6-6   c , where a stop bolt  54  is inserted in one threaded hole  56  and the terminal stop  45  is in place. Release latch  88  is situated just underneath the rail and is biased in a central orientation by plunger  89 , which is so biased by spring  89   a . On top of release latch  88 , is an angled block  88   a  which will interface with stop bolt  54  and terminal stop  45 . In  FIGS. 7-7   c , the stock is depicted as having been extended (moved back) until the block  88   a  abuts stop bolt  54 . As can be seen, the wide portion of the angled block  88   a  actually abuts the stop bolt  54  and prevents the stock from being further retracted. However, it should be noted that if the release latch was on the other side of the stop bolt  54 , the angled portion of the block  88   a  would interface with the stop bolt  54  (if being pushed forward) and would actually act as a lever, moving the release latch  88  out of the way so that the stock could be collapsed without engaging the release latch  88 . 
   In order to avoid the stop bolt  54 , the user presses the release latch  88  to one side ( FIGS. 8-8   c ). As the block  88   a  circumvents the stop bolt  54 , the stock may be retracted further ( FIGS. 9-9   c ) without hindrance, until it reaches the point of terminal stop  45  ( FIGS. 10-10   c ). It should be noted that in both its natural stage ( FIGS. 11-11   c ) and the biased stage ( FIGS. 10-10   c ), the block  88   a  interfaces with the terminal stop  45 . Instead, to avoid the terminal stop  45 , the release latch  88  must be biased in the opposite direction as to avoid the bolt stop  54 . This is done intentionally so as to avoid accidental removal of the stock from the system which only trying to avoid the bolt stop  54 . The release latch  88  maintains its central bias via spring loaded plunger  89  which interfaces with a “V” shaped notch  88   b  on the underside of the release latch  88 . When the release latch  88  is biased to one side or the other by the user, plunger  89  is displaced by the walls of notch  88   b  and spring  89   a  is compressed ( FIGS. 8   a ,  9   a ,  10   a ,  12   a ). When the bias is released, spring  89   a  decompresses, forcing plunger  89  forward and restoring release latch  88  to its central orientation ( FIGS. 6   a ,  7   a ,  11   a ) by pressure against the notch  88   b.    
   The latching mechanism is depicted in  FIGS. 13-17   a . As seen in  FIGS. 13-13   b , the latch components are the latch housing  85 , which contains the shock cushion  86  and trigger structure  82 . Lock pawls  84  are mounted on the top of the housing  85 . Lock pawls  84  are biased by springs  90  ( FIGS. 15 &amp; 16 ) in an upward orientation. Trigger structure is also spring biased in an extended position by latch spring  92 , mounted upon post  94  in the housing ( FIG. 17   a ). Latch spring  92  rests inside orifice  87  in the trigger structure ( FIG. 13   a ). Trigger structure comprises the actual trigger body  81  and two bias wedges  83 ,  93 , to actuate lock pawls  84 . As shown in  FIG. 14 , the latch mechanism resides below the rail  52  on the sleeve module  14 . Pre-set latch  88  resides between the latch mechanism and the rail  52 . 
   In operation, the latch is usually in its locked position, shown in  FIGS. 15 and 15   a , with lock pawls  84  resting within detents in the rail  52 . Lower wedge  83  provides a mechanical stop to prevent the lock pawls  84  from accidentally being compressed. In intermediate stages, the front slope of the wedge  83  actually provides an assist to effectively and securely move the lock pawls  84  into their locked position ( FIGS. 16 and 16   a ). To unlatch the stock ( FIGS. 17 and 17   a ), trigger body  81  is compressed against trigger spring  92 . This motion causes upper wedge  93  to approach a pawl pin  91  that extends from each pawl  84  and push the pin  91  downward, compressing pawl springs  90  (not shown in  FIGS. 17 and 17   a ) and lowering the lock pawls  84 . This then allows the stock body to slide transversely along the rail  52 , subject to the pre-set system. It should be noted that the lock pawl pins  91  do not join the lock pawls  84  together. The lock pawls  84  operate independently of each other so that failure of one, especially in the open position, may be compensated by the action of the other. 
   Other features of the stock body, in its preferred embodiment and shown in  FIGS. 1 and 2 , include a storage compartment  62 , formed by having a hollow body enclosed by attachable walls. One of said walls may be capable of opening without removal. The stock also features a removable tailpiece  64 . Tailpiece  64  provides structural support and may be designed to protrude from the stock body (as shown in  FIG. 2 ) with a sling loop or with other useful structure, like a glass strike plate. A rubberized butt pad  66  may also be provided to provide some shock absorption when impacts occur, either intentionally or unintentionally. It should be noted that other stock bodies, each with their own set of desirable features, may be designed and used with the described mounting system. As such, no limitation in the claims to the preferred stock body as described herein should be inferred, but only read into the claims where the specific structures of the preferred stock body are directly claimed. 
   Although the present invention has been described with reference to preferred embodiments, numerous modifications and variations can be made and still the result will come within the scope of the invention. No limitation with respect to the specific embodiments disclosed herein is intended or should be inferred.