Patent Publication Number: US-8991092-B2

Title: Method and apparatus for splitting a delta ring on a rifle

Description:
The present application draws priority from a U.S. Provisional Patent Application, Ser. No. 61/522,524, filed Aug. 11, 2011. 
    
    
     TECHNICAL FIELD 
     The present invention relates to military-style small arms and modern sporting rifles that are fashioned after an AR15 style of fire arm having a similar form of handguard system; more particularly, to the “delta ring” component of an AR15 type rifle such as an M16 or M4 carbine rifle; and most particularly, to an apparatus and method for use in splitting a delta ring installed on a rifle to facilitate, for example, changing of a type of handguard or converting to a free-float barrel. 
     BACKGROUND OF THE INVENTION 
     A so-called delta ring is a well known inline component of various types of shoulder-fired weapons also known in the art as long arms. In an assembled weapon, the delta ring assembly consists of an aluminum alloy delta ring, a steel weld bias spring and a snap ring that retains the assembly on the barrel assembly. The delta ring surrounds a proximal portion of the weapon barrel and is spring-biased forward by the steel weld spring to retain, support, and position a two-piece handguard assembly on and around the barrel. The delta ring may be urged manually rearward of the barrel against the bias spring to free each upper and lower handguard section for removal. 
     Typically, a delta ring assembly may be thought of as a sub-assembly of the barrel assembly and integral to the handguard system. For various reasons that may arise during use of a long arm, it may become desirable to remove the delta ring assembly rapidly and easily, for example, as a step in changing over to a new and/or different type of handguard system which might substantially improve the performance of the long arm such as by allowing the barrel to free float. After the weapon&#39;s handguard is removed, the delta ring is fully exposed and accessible. 
     In the prior art, the delta ring is removed either by a full disassembly of the barrel from the upper receiver by removal of the handguard, then the gas tube, and then the barrel nut. Alternatively, the delta ring may be removed by removing the handguard and then splitting the delta ring in two with, for example, general purpose tools such as large bolt cutters or a Dremel cutting tool, and then removing the two halves of the delta ring radially of the weapon. 
     Dissassembly by removing the barrel nut is generally undesirable as it is time-consuming and requires a pin punch to remove the gas tube retaining pin, removal of the gas tube, a special barrel nut tool to remove the barrel nut from the weapon&#39;s upper receiver and requires snap ring pliers to release the delta ring assembly, sliding the delta ring, steel weld spring, and snap ring off the distal end of the barrel. Reassembly of the barrel assembly after removing the delta ring assembly requires re-torquing the barrel nut back onto the receiver which is more time-consuming and requires both a barrel nut tool and a torque wrench and is generally undesirable to perform more times than is necessary as one is torqing a steel nut onto aluminum threads which are softer and may wear or fatigue. Furthermore, force is applied to the barrel nut in the torquing process which acts upon the thin crenellations of the barrel nut which encircle the gas tube after final installation. This force on the barrel nut tool can deform the barrel nut crenellations and consequently require replacement of the barrel nut altogether. This may also be difficult to accomplish under field conditions and can expose the weapon to misaligning forces during reassembly. 
     Splitting the delta ring is generally a preferable method of removal of the delta ring assembly, as it exposes the weld spring and snap ring for easy removal from the proximal end of the barrel with general purpose pliers; however, current methods for cutting the delta ring itself using electrically-powered tools, which may not be present under field conditions, require more skill and may also nick the barrel nut or receiver, and may require several cutting blades. In methods using large bolt cutters, the tool may easily slip off the delta ring and may require an additional fixture to secure the upper receiver or barrel during the operation. 
     What is needed in the art is a method for splitting a delta ring using a simple and lightweight apparatus that may be readily available in the field and can reduce the training or skill required to complete the task. 
     It is a principal object of the present invention to facilitate removal of a delta ring assembly from a weapon. 
     SUMMARY OF THE INVENTION 
     Briefly described, a currently preferred apparatus in accordance with the present invention includes a tool body having first and second spaced-apart parallel columns extending from a common base. The base includes a lip generally perpendicular to the columns and extending outward therefrom, preferably with ears, defining an anvil for receiving a delta ring. A guillotine cutter has a cutter body slidably disposed between the columns and a blade extending outward from the columns and positioned facing and in opposition to the anvil. The cutter body is aligned during travel between the columns by one or more transverse guide pins extending through guide slots formed in the columns. 
     In operation, a section of the delta ring is positioned between the blade and the anvil, following which the blade is driven toward the anvil by any one of various mechanical, pneumatic, and/or hydraulic mechanisms known in the art and connected to the tool body and cutter body, the simplest of which is a bolt extending through the cutter body and received in a threaded bore in the base or vice versa. Preferably, the anvil includes a slot for receiving the blade at the extreme of its travel, as the ring is severed. 
     Other embodiments may include, for example, two such tools, which may be operationally connected for cutting simultaneously two diametrically opposed delta ring sections. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1  is an isometric view of a prior art M4A3 carbine rifle having a delta ring and removable handguard; 
         FIG. 2  is an exploded isometric view of the barrel assembly of the rifle shown in  FIG. 1 ; 
         FIG. 3  is an exploded isometric drawing of a portion of a first embodiment of a delta ring splitting apparatus in accordance with the present invention; 
         FIG. 4  is an isometric view of a completely assembled apparatus in accordance with the present invention; and 
         FIG. 5  is an isometric view of the apparatus shown in  FIG. 4  having a delta ring installed in position for splitting in accordance with a method of the present invention; 
         FIG. 6  is an isometric view showing the apparatus shown in  FIG. 4  disposed on the barrel assembly shown in  FIG. 2 ; 
         FIG. 7  is an elevational view similar to the isometric view shown in  FIG. 6 ; and 
         FIG. 8  is an elevational view showing a second embodiment of a delta ring splitting apparatus wherein first and second splitters are disposed in opposition on a common delta ring. 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate currently preferred embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIGS. 1 and 2 , a typical AR15 military-style rifle  10  having a delta ring  12  is shown. Delta ring  12  is slidably disposed on barrel  14  and is spring-biased forward to engage and retain split handguard  16  in use position by urging the handguard into reception by handguard cap  18 . When delta ring  12  is displaced away from handguard  16  by compressing weld spring  17  against spring clip  19 , the handguard is readily removed, providing full axial access to delta ring  12  and scalloped barrel nut  20  which is threaded and torqued onto receiver  15 . 
     Referring to  FIGS. 3 through 5 , a first embodiment  110  of a tool for splitting a delta ring comprises a tool body  112  and a cutter body  114 , both formed preferably of metal alloys such as steel, and hardened steel for the blade. 
     Tool body  112  comprises first and second spaced-apart parallel columns  116 , 118  extending from a common base  120 . Base  120  includes a lip  122  generally perpendicular to columns  116 , 118  and extending outward therefrom, preferably with first and second hooks  124 , 126 , defining an anvil  128  for receiving a delta ring  129  on lip  122  behind hooks  124 , 126 . Columns  116 , 118  preferably are provided with respective arcuate surfaces  117 , 119  that are conformable with the outer surface of a delta ring. 
     Cutter body  114  is slidably disposed between columns  116 , 118 , and blade  130  extends outward from columns  116 , 118  and is positioned facing and in opposition to anvil  128 . Cutter body  114  is aligned during travel between columns  116 , 118  by one or more transverse guide pins  132  mounted in cutter body  114  and extending through guide slots  134  formed in columns  116 , 118 . 
     In operation of the present example, a portion  12   a  of delta ring  12  is positioned between blade  130  and anvil  128 , following which blade  130  is driven toward anvil  128  by machine bolt  136  extending through a smooth bore  138  in cutter body  114  and received in a threaded bore (not visible) in base  120 . Preferably, anvil  128  includes a slot  140  for receiving blade  130  at the extreme of its travel, as delta ring  12  is severed. 
     A delta ring  12  typically includes a tapered body portion  12   b  and an inner ring  12   c  for engaging a flange on handguard  16 . Therefore, preferably blade  130  comprises first and second blade edges  131 , 133  for cutting body portion  12   b  and inner ring  12   c , respectively. The inner edge of second blade edge  133  also keeps first blade edge  131  retained in tapered surface  12   b  while it is cutting. 
     Referring to  FIGS. 6 and 7 , after handguard  16  ( FIG. 2 ) is removed, tool  110  may be installed onto delta ring  12 . Note that blade  130  is formed to fit through the crenellations  142  on barrel nut  20 . 
     Other embodiments of the present invention may include, for example, a second embodiment  210  comprising two such tools  110 - 1 , 110 - 2  to be used simultaneously and operationally connected (not shown) for cutting two diametrically opposed sections  12   a , 12   d  of delta ring  12 . Such operationally connected means (not shown) may be mechanical, hydraulic, and/or pneumatic and may include, for example, a lever and/or a ratchet. 
     Another embodiment (not shown) envisioned by the present invention comprises a tool wherein first and second blades (“upper” and “lower” blades, respectively) engage a delta ring therebetween and are driven towards each other in the manner of a bolt cutter. Preferably, each blade includes a hook-like feature to maintain the delta ring in proper position during cutting thereof. 
     While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims.