Patent Publication Number: US-11385019-B2

Title: Double walled handguard for firearm

Description:
BACKGROUND 
     The present invention relates to a double-walled handguard for a firearm. 
     SUMMARY 
     In one embodiment, the invention provides a handguard for mounting around a barrel of a firearm, the handguard comprising: an inner tube surrounding a portion of the barrel; an outer tube surrounding the inner tube; a plurality of radial struts interconnecting the inner tube and the outer tube to create a circumferential gap between the inner tube and outer tube; and a plurality of accessory mounting apertures in the outer tube for mounting a plurality accessories to the handguard. 
     In one aspect of the invention, the inner tube includes a plurality of clearance apertures aligned with the accessory mounting apertures, such that ends of fasteners used to secure an accessory to the handguard extend into the clearance apertures. In one aspect of the invention, the outer tube includes a plurality of flat surfaces and the accessory mounting aperture is formed in one of the flat surfaces. In one aspect of the invention, the outer tube includes more than three flat surfaces in which accessory apertures are formed. In one aspect of the invention, the outer tube includes at least five flat surfaces in which accessory apertures are formed. In one aspect of the invention, the outer tube has an octagonal cross-section eight vertices; the radial struts intersect at a plurality of the vertices; and the plurality of accessory mounting apertures are formed in at least two surfaces of the octagonal outer tube. In one aspect of the invention, the outer tube includes vent holes for venting air from the circumferential gap. In one aspect of the invention, the circumferential gap is sized to accommodate mounting nuts for the plurality of accessories. In one aspect of the invention, the radial struts extend lengthwise along the inner and outer tubes to divide the circumferential gap into lengthwise segments. In one aspect of the invention, the inner tube and outer tube are concentric about a longitudinal axis of the handguard. 
     The invention also provides a method of manufacturing a handguard for a firearm, the method comprising the steps of: (a) forming a blank comprising an inner tube, and outer tube surrounding the inner tube, and a plurality of radial struts interconnecting the inner tube and the outer tube to create a circumferential gap between the inner tube and outer tube; and (b) forming into the outer tube a plurality of accessory mounting apertures to facilitate mounting accessories to the handguard. 
     In one aspect, the invention further comprises the step of forming into the inner tube a plurality of clearance apertures aligned with the accessory mounting apertures, such that ends of fasteners used to secure an accessory to the handguard extend into the clearance apertures. In one aspect of the invention, step (a) includes providing a plurality of flat surfaces on the outer tube and step (b) includes forming the accessory mounting apertures into the flat regions. In one aspect of the invention, step (a) includes providing more than three flat surfaces on the outer tube and step (b) includes forming the accessory apertures into the flat regions. In one aspect of the invention, step (a) includes forming the outer tube with an octagonal cross-section eight vertices; step (a) further includes forming the radial struts at a plurality of the vertices; and step (b) includes forming the accessory mounting apertures into at least two sides of the octagonal outer tube. In one aspect, the invention further comprises forming a plurality of vent holes in the outer tube for venting air from the circumferential gap through the vent holes. In one aspect of the invention, step (a) includes sizing the circumferential gap to accommodate mounting nuts for the plurality of accessories. In one aspect of the invention, step (a) includes dividing with the struts the circumferential gap into peripheral segments. In one aspect, the invention further comprises forming communicating holes through the struts to place the peripheral segments in communication with each other. In one aspect of the invention, step (a) includes forming the outer tube and inner tube concentrically about a longitudinal axis. In one aspect of the invention, step (a) includes extruding the blank and step (b) includes machining the accessory mounting apertures into the outer tube. In one aspect of the invention, step (a) includes extruding the blank with at least five bores. 
     Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a firearm having a double-walled handguard according to the present invention. 
         FIG. 2  is a perspective view of the handguard. 
         FIG. 3  is a cross-section view of the handguard taken along line  3 - 3  in  FIG. 2 . 
         FIG. 4  is a cross-section view of the handguard taken along line  4 - 4  in  FIG. 2 . 
         FIG. 5  is a perspective view of an alternative configuration of the handguard. 
         FIG. 6  is a cross-section view of the handguard taken along line  6 - 6  in  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION 
     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. 
       FIG. 1  illustrates a firearm  10  in the form of an AR-15 carbine or rifle. The firearm  10  has well-known components, such as an upper receiver  20 , a lower receiver  30 , a buttstock  40 , and a barrel  50 . A handguard  150  according to the present invention surrounds the barrel  50  and will be discussed below. The upper receiver  20  includes the firing and reloading action of the firearm  10 . The upper receiver  20  includes an upper receiver accessory rail  60  (in the form of a Picatinny rail in the illustrated embodiment) running along the top of the upper receiver  20 . The lower receiver  30  is below the upper receiver  20  and includes a trigger assembly  70  for actuating the firing action in the upper receiver  20  and also includes a pistol grip  80  for the user to grasp during operation. The buttstock  40  extends rearwardly of the upper receiver  20  and is held against a user&#39;s shoulder during firing. The barrel  50  is mounted to the upper receiver  20  with a barrel nut  90 . The barrel  50  extends forward from the upper receiver  20  and defines a longitudinal axis  100 . A flash suppressor  110  may be mounted to the end of the barrel  50  to reduce the visibility of burning gases exiting the barrel  50  while firing the weapon. 
     With reference to  FIGS. 1 and 2 , the handguard  150  is mounted at one end to the outer surface of the barrel nut  90  which interconnects the barrel  50  to the upper receiver  20 . The handguard  150  surrounds the barrel  50  and provides a convenient place for the user to grasp while firing the firearm  10 . The handguard  150  extends in cantilever fashion forward along the longitudinal axis  100  from the upper receiver  20  to a distal end. As illustrated, the handguard  150  is concentric with the barrel longitudinal axis  100 . 
     The illustrated handguard  150  includes accessory mounts in the form of handguard accessory rails  160 , a plurality of accessory mounting apertures  170 , or any other form of an accessory mount. The illustrated handguard accessory rails  160  are forward and rear Picatinny rails running along the top of the handguard  150  (i.e., at the twelve o&#39;clock position of a clock face superimposed on the cross-section) and also Picatinny rails in the rear portion of the handguard  150  at the three o&#39;clock, six o&#39;clock, and nine o&#39;clock positions. The top handguard accessory rails  160  align with the upper receiver accessory rail  60  in the illustrated configuration. The accessory mounting apertures  170  may take the form of M-Lok slots, KeyMod slots, or H Key slots. Accessories (e.g., flashlight, laser sight, scope, hand grip) can be attached to the handguard  150  by way of the accessory mounting apertures  170  to enhance efficacy of the firearm  10  in the hands of its user. 
     Referring to  FIGS. 3 and 4 , the handguard  150  includes an inner tube  210 , an outer tube  220 , and a plurality of radial struts  230  interconnecting the inner tube  210  and outer tube  220 . As illustrated, the inner tube  210  and outer tube  220  are concentric with each other. The inner tube  210  may be cylindrical with a circular cross-section and the outer tube  220  may be include a plurality of flat surfaces or regions  240   a ,  240   b . The inner tube  210  surrounds a portion of the barrel  50  and the outer tube  220  surrounds the inner tube  210 . The inner tube  210  includes a gap  250  at the top as will be explained further below. 
     In the illustrated embodiment, the outer tube  220  has an octagonal cross-section with four primary flat regions  240   a  and four secondary flat regions  240   b . When properly installed, the four primary flat regions  240   a  are at the twelve o&#39;clock, three o&#39;clock, six o&#39;clock, and nine o&#39;clock positions of a clock face superimposed on the cross-section. The four secondary flat regions  240   b  are nominally at the one-thirty, four-thirty, seven-thirty, and ten-thirty clock positions, connecting or bridging between the primary flat regions  240   a . Other outer tube  220  shapes are contemplated by the present invention. For example, the outer tube  220  may include four or more flat regions around its outer surface and the flat regions can be non-symmetrical and of not the same width depending on the application. The accessory mounts  160 ,  170  can be positioned on or in any of the flat regions of the outer tube  220 . 
     The illustrated embodiment includes eight radial struts  230  which connect at the eight vertices of the octagonal cross-section outer tube  220  (i.e., the eight intersections of the primary and secondary flat regions  240   a ,  240   b ). The radial struts  230  extend in the longitudinal direction along the entire lengths of the inner and outer tubes  210 ,  220 . The struts  230  also extend radially from the inner tube  210  to the outer tube  220  to create and maintain a circumferential gap  260  between the inner tube  210  and outer tube  220 . The circumferential gap  260 , which can be referred to as an annular spacing or gap or an annulus, is bounded by the inner tube  210  and outer tube  220 . The circumferential gap  260  may be of constant radial thickness or width around the circumference of the inner tube  210  or may vary depending on the shapes of the tubes  210 ,  220  and the desired result. The radial thickness or width of the circumferential gap  260  can be set to accommodate known fasteners (e.g., T-nuts and the like) of known accessory mounting systems. The circumferential gap  260  can provide an additional benefit of capturing the fasteners if they become detached from the accessory or accessory mounting system. 
     The double-wall (tube-within-a-tube) configuration with struts is structurally similar to an I-beam. Spacing the tube walls  210 ,  220  from each other with the struts  230  provides a relatively high mass moment of inertia (and therefore stiffness) compared to a single-tube handguard, much like an I-beam provides a higher mass moment of inertia compared to a standard beam. 
     The handguard  150  is preferably manufactured by extruding a concentric tube blank from any extrudable material ideal for firearm use. For example, the material might be one of many available temperature resistant, high strength polymers, resins, composites, or carbon fiber materials or an alloy of magnesium, aluminum, and titanium or a suitable carbon or stainless steel. The tube blank includes the inner tube  210 , outer tube  220 , and struts  230 . The tube blank includes eight bores comprising a central bore  270  and seven peripheral bores or segments  280 . The central bore  270  is inside the inner tube  210  and also includes a top lobe  270   a  at the twelve o&#39;clock position which defines the gap  250  in the inner tube  210 . The top lobe  270   a  accommodates the gas tube of the firearm  10 , which runs along the top of the barrel  50 . Each of the seven peripheral bores  280  is bounded by the outer surface of the inner tube  210 , the inner surface of the outer tube  220 , and two of the struts  230 . 
     It should be noted that the present invention can be extruded with the central bore  270  and four or more peripheral bores  280  (i.e., at least five bores), resulting potentially in a double-walled handguard having four or more flat portions  240  on the outer tube  220  for accessory mounts  160 ,  170 . The handguard  10  can be extruded with five, six, seven, eight (as illustrated) or more bores and flat portions depending on the application. 
     The tube blank is machined to form the accessory mounts  160 ,  170  in the flat portions  240   a ,  240   b  of the outer tube  220 . The term “machine” and its derivatives (e.g., “machined”) includes any process of forming by elimination, for example grinding, drilling, and cutting. The tube blank can be machined to form any conceivable combination of accessory rails and accessory mounting apertures, including but not limited to Picatinny rails, KeyMod slots, M-Lok slots, or HKey slots. The illustrated configuration is not intended to be limiting. For example, accessory rails  160  could be machined into any of the flat portions  240   a ,  240   b . Indeed, in the illustrated embodiment accessory rails  160  are machined into the four primary flat portions  240   a  in the rear portion of the handguard  10  as seen in  FIGS. 1, 2 and 3 . As illustrated in  FIGS. 1 and 2 , the accessory rails  160  do not have to extend the entire length of the handguard  150 . A flat section can be machined into the blank between the two accessory rails  160  as illustrated. 
     Likewise, any kind of accessory mounting aperture  170  or combination of aperture types could be machined into any of the flat portions  240   a ,  240   b . With reference to  FIG. 4 , clearance apertures or holes  290  may be machined into the inner tube  210  to accommodate the end of a fastener that is used to secure an accessory in a corresponding accessory mounting aperture  170  in the outer tube  220 . The clearance holes  290  are positioned opposite the accessory mounting apertures  170  where such fasteners are expected to extend. 
     Referring to  FIGS. 2 and 3 , weight-saving features such as weight-saving or lightening apertures  300  can be machined into the inner and outer tube  210 ,  220  walls to remove material and thereby reduce the overall weight of the handguard  150 . Additionally, portions of the outer tube  220  could be completely machined away in some embodiments to reduce weight and expose the inner tube  210  in that portion of the handguard  150 . In such case, an accessory mount  160 ,  170  or lightening apertures  300  could be machined into the exposed portion of the inner tube  210  for a desired attachment system or weight reduction. 
     Referring to  FIGS. 2 and 4 , another feature that can be machined into the tube blank when forming the handguard  150  is venting holes  310  in the top of the outer tube  220  and communication holes through the struts  230  to place the peripheral bores  280  in communication with each other. As the firearm  10  is fired, the barrel  50  can become hot. Heat from the barrel  50  is transferred to the air around the barrel  50  inside the handguard  150 . The hot air migrates between the peripheral bores  280 , naturally rising to the top of the circumferential gap  260  (which comprises the peripheral bores  280  in communication with each other). The venting holes  310  permit hot air to escape the circumferential gap  260  in an efficient manner to the sides of any site on top of the upper receiver  20  and handguard  150  such reduce distraction due to the mirage effect of such rising hot air. 
     The relatively large mass or surface area of the double-walled handguard  150  and the insulating layer of air in the circumferential gap  260  are expected to reduce the temperature of the outer tube  220  compared to the temperature of a similarly sized single-wall handguard. This should result in more comfort for the firearm user. 
       FIGS. 5 and 6  illustrate another configuration of the handguard  150 ′. The handguard  150 ′ is made the same way as described above, namely with an extruded double-wall blank into which features are machined. The features of the handguard  150 ′ are accessory mounts  160 ,  170  in the form of Keymod slots formed in the flat regions  240   a ,  240   b  and a Picatinny rail on top. Because the Keymod system does not use T-nuts and relatively long fasteners, there is no need for the clearance holes in the inner tube  210 . When desirable, weight lightening apertures may be machined into the inner tube  210  or outer tube  220  or both as discussed above. 
     Thus, the present invention provides a handguard and a method of manufacturing a handguard. The handguard includes inner and outer tubes spaced apart from each other via a plurality of struts to define a circumferential gap between the tubes. The handguard includes a plurality of accessory mounts, which can include accessory rails and accessory mounting apertures. These and other aspects of the invention are recited in the following claims.