Patent Publication Number: US-6655569-B1

Title: Power actuated tool and shroud for use with the tool

Description:
This invention relates to power actuated tools and more particularly to explosively actuated tools for driving a fastener such as a pin into a substrate such as concrete or steel. 
     Explosively actuated tools which are used to fire fasteners into a hard substrate such as concrete or steel generally have an associated recoil action during which noise resulting from the firing procedure is emitted. Such a tool typically comprises a barrel from which the fastener is expelled by means of the piston driven by detonation of the explosive charge. The detonation of the explosive charge results in recoil of the tool and combustion gasses subsequently being vented from the barrel at high pressure and velocity to thereby generate a loud noise emission. 
     The invention seeks to reduce noise emissions in power actuated tools. 
     In accordance with the invention, there is provided a shroud for use with a power actuated tool for firing a fastener into a substrate, the shroud being adapted to couple between a main barrel and a slidable front barrel of the tool and being adapted to extend from a collapsed condition when a mouth of the front barrel is positioned adjacent to a substrate into which a fastener is to be fired and an extended condition when the main barrel is in a recoiled position relative to the front barrel after firing the tool, wherein the shroud defines a cavity to at least partially contain noise emission from the main barrel resulting from the tool firing of the tool. 
     Further according to the invention, there is provided a power actuated tool for driving a fastener into a substrate such as steel or concrete, said tool comprising a housing, a barrel assembly mounted to the housing, and a piston displaceable within the barrel assembly upon firing of the tool to drive a fastener from the forward end of the barrel into the substrate, at least a forward end of the barrel assembly being mounted for axial movement relative to the housing whereby firing of the tool requires the forward end of the barrel assembly to be pressed against the substrate to cause retraction of the forward end relative to the tool housing, said tool further comprising a shroud surrounding the forward end of the barrel assembly to at least partially suppress noise emission resulting from firing of the tool. 
    
    
     The invention is more fully described, by way of non-limiting example only, with reference to the accompanying drawings, in which: 
     FIG. 1 is a partial cross-sectional side view of a known form of power actuated tool; 
     FIG. 2 is a partial side view of the tool of FIG. 1, showing the configuration of the barrel assembly upon recoil after firing in a recoiled position; 
     FIG. 3 is a diagrammatic cross-sectional view of a power actuated tool, including a shroud, in accordance with the invention; 
     FIG. 4 illustrates the tool of FIG. 3 with the shroud in an extended condition after firing; 
    
    
     The known tool  1  shown in FIG. 1 includes a housing  2 , a hand grip  3  and a trigger  4 . A barrel assembly comprising a main barrel  5  extends into the housing  2  and receives a front barrel  6  therewithin for axial slidable movement relative to the main barrel. The barrel  6  has a central bore  7  which in turn receives a fastener guide  8  which has a free end  9  projecting from a muzzle  10  of the front barrel  6 . The front barrel  6  also has an annular shoulder  11  for abutment with a mouth  12  of the main barrel  5 . 
     In use of the tool  1 , a fastener is inserted in the free end  9  of the fastener guide  8  and the forward end of the tool is pressed against a substrate into which the fastener is to be fired. The pressure causes the fastener guide  8  to retract into the front barrel  6  and possibly the entire barrel assembly to retract which releases a safety lock of the tool  1  and places the muzzle  10  in direct abutment with the substrate. Such safety mechanisms which enable firing of the tool only when the forward end of the barrel assembly is pressed against the substrate are well known in tools of this type. The trigger  4  may then be actuated to detonate an explosive charge via an appropriate firing mechanism to force a piston along the barrel  5  and through the fastener guide  8  to directly impact with the fastener and drive it into the substrate. When the charge detonates, a recoil action causes the housing  2  to move rearwardly relative to the front barrel  6 . Relative displacement between the front barrel  6  and the main barrel  5  exposes an exhaust aperture  14 , as represented in FIG. 2, to allow combustion gases within the barrel  5  to be vented to the atmosphere. The high pressure and velocity of the gases causes a considerable noise to result. 
     The tool  20  of the present invention is shown in FIG.  3 . Only the main and front barrel region of the tool is shown since the other parts of the tool are otherwise similar to those of the tool  1 , described with reference to FIGS. 1 and 2 and like parts are denoted with similar reference numerals. Like the tool  1 , the tool  20  includes a housing  2  with a main barrel  5  and a front barrel  6 , however the tool  20  has a shroud  21  coupled therebetween. The shroud  21  includes a plurality of telescopically connected sleeves  22 ,  23  and  24 . Although as shown there are three sleeves, other embodiments may consist of only two sleeves, or more than three sleeves. The sleeve  22  is slidably mounted about the housing  2  surrounding the main barrel  5  whereas the sleeve  24  is secured to a front portion  25  of the front barrel  6  by suitable attachment means. 
     Accordingly, relative axial movement between the front barrel  6  and the main barrel  5  results in corresponding movement of the sleeves  22 ,  23  and  24 . When the front barrel  6  is in the pre-firing condition, similar to that shown in FIG. 1, the sleeves are in a collapsed condition as shown in FIG.  3 . However, relative movement between the barrels  5 , 6  as will occur on recoil after firing will result in the shroud  21  extending as shown in FIG. 4 whereby any gases vented from within the barrel exit directly into a cavity  26  defined by the shroud  21 . As such, noise emissions may be substantially reduced. Performance of the invention has been demonstrated with a prototype as being capable of achieving a noise reduction from 114 dB to 106 dB. After initial capture of the combustion gases, the gases may exit to atmosphere from the tool in a laminar fluid flow between the sleeves  22  to  24  which are not a tight fit one relative to the other. 
     After firing, the front barrel  6  can be retracted relative to the main barrel  5  by grasping the front sleeve  24  of the shroud  21  and displacing the sleeve  24  rearwardly to collapse the shroud. This movement of the front barrel  6  may also serve to facilitate resetting of the piston into the rear of the barrel assembly in preparation for a subsequent firing. 
     In addition to reducing noise emissions, the shroud fully encases the components of the tool between the housing  2  and the front portion  25  of the front barrel  6  such that cycling of the tool in a conventional manner, results in the shroud  21  being fully extended in the manner illustrated in FIG.  4 . The shroud thereby serves to protect the internal components of the tool from the environment and contaminants such as dust or other particulate matter. Accordingly, the shroud  21  can assist in increasing the working life and reliability of the tool whilst also providing an aesthetically pleasing external appearance. 
     The shroud  21  and tool  20  have been described by way of non-limiting example only and many modifications and variations may be made thereto without departing from the spirit and scope of the invention as hereinbefore described. 
     Throughout this specification and claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers or steps but not the exclusion of any other integer or group of integers.