PATENT ABSTRACT
A radial arm saw is adapted with a safety top configured with cutting box enclosure that contains and collects substantially all of the sawdust generated during use. A dust collection system is in fluid communication with the cutting box for removing the sawdust contained therein. Spring biased push blocks function to hold the work piece in place during the sawing process while maintaining the user&#39;s hands safely away from the saw blade. A laser alignment device projects a beam within the cutting box along the cutting plane. A control panel is provided to allow use by authorized users upon entry of an authorization code.

PATENT DESCRIPTION
CROSS REFERENCE TO RELATED APPLICATIONS 
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   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
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   COPYRIGHT NOTICE 
   A portion of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or patent disclosure as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyrights rights whatsoever. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to radial arm saws, and more particularly to a safety top for use in safe operation of radial arm saws while providing improved dust collection. 
   2. Description of Related Art 
   Radial arm saws are routinely found in wood working environments for use us in various wood cutting applications. Over the past several years, the use of the radial arm saw has expanded significantly due largely to versatility and simplicity of use. Today, radial arm saws are in use in wood working shops, garages, even retail outlets, such as hardware and home improvement stores. 
   A typical radial arm saw includes a work table having a horizontal flat top work surface with a vertically projecting backstop, commonly referred to as a fence. The material to be cut, such as a piece of wood, is supported on the work surface and against the fence. At the rear of the work table a vertical column extends upwardly. Extending horizontally from the top of the column is a radial arm, which is capable of rotation about the column, but which is generally positioned over the top of the table. A rotary power saw is suspended below the radial arm by a carriage adapted for travel along the length of the radial arm. In most operations, the saw is positioned over the work table and is moved along the radial arm to cut a workpiece positioned on the work surface. 
   While the radial arm saw is an efficient and proven power tool, there remain a number of problems and shortcomings associated with the operation thereof that heretofore have not been adequately solved or addressed. One such problem associated with the radial saw operation relates to the substantial amount of sawdust created and dispersed when cutting. The sawdust generated by a radial arm saw ranges from very fine dust particles to larger wood chips. While this problem has been widely recognized for many years, radial arm saw manufacturers have failed to develop an effective dust collection system for use with these saws. One common, yet ineffective, solution has been to provide the saw blade with a protective guard or hood adapted with a suction port connected to a vacuum-generating dust collection system by a hose. That attempt, however, has proven unsatisfactory and generally ineffective. 
   As a result of the persistent problems associated with saw dust, the background art reveals a number of attempts directed to dust collection systems for use with radial arm saws. For example, U.S. Pat. No. 2,839,102, issued to Kido, discloses a dust collecting attachment that mounts behind the guide fence of a radial arm saw. The attachment defines slotted openings aligned with kerfs in the guide fence, and is attached to a suction-generating dust collector apparatus. U.S. Pat. No. 3,322,169, issued to Hilliard, discloses a dust collector for a radial arm saw including a rectangular shroud having an inlet and a tapered tube extending rearwardly therefrom for connection to a vacuum hose. U.S. Pat. No. 3,401,724, issued to Kreitz, discloses a dust collector for a radial arm saw comprising generally funnel-shaped hood positioned at the rear of the work table. The wide hood inlet opens toward the front of the work table and a narrow outlet is connected to a dust collector apparatus. U.S. Pat. No. 4,144,781, issued to Kreitz, discloses a dust collector for a radial arm saw including a generally funnel-shaped flat-bottomed shroud connected to a vacuum hose. The top and bottom of the shroud are contoured so that the shroud partially surrounds the column which supports the radial arm saw. U.S. Pat. No. 4,742,743, issued to Scarpone, discloses a radial arm saw accessory comprising a grid structure formed in the table surface in proximity to the fence to permit passage of sawdust therethrough. 
   It appears, however, that the above-referenced advances in the art of radial arm saw dust collection have not been successful in substantially containing and collecting sawdust generated by the radial arm saw. Accordingly, those devices have not gained widespread acceptance. Thus, there exists a need for improvements in radial arm saw design. More particularly, there exists a need for an improved dust collection system for use with radial arm saws. 
   Another serious problem present with the widespread use of radial arm saws relates to operator safety. More particularly, during normal use the rotating saw blade often comes in close proximity to the operators hands and fingers. As a result, numerous individuals have been seriously injured by inadvertent contact with the rotating saw blade while operating the radial arm saw. The problem is complicated since operation of the saw requires the user to move the saw/blade across the work surface while cutting thereby increasing the risk of injury. The risk of injury increases when the saw is used by inexperienced operators in garage shops or employees in retail locations. Despite the serious risk of injury inherent with conventional radial arm saw designs, manufacturers have failed to provide adequate measures intended to prevent injury. 
   The background art reveals a number of attempts directed to protecting operators from injury while operating radial arm saws. These attempts include blade guards intended to prevent the operator&#39;s hand from contacting the rotating blade. Blade guards, however, have proven ineffective. Other attempts include providing work piece guides and push devices designed to assist the operator in positioning the work piece. U.S. Pat. No. 5,678,467, issued to Aigner, discloses a handle adapted for holding or pushing wood during the sawing process. The Aigner device, and others in the art, provide handle-like structures that engage the wooden workpiece such that the user&#39;s hand is positioned away from the cutting plane. The prior art further reveals a number of work piece guides, primarily for use with table saws. Representative disclosures of such devices are found in U.S. Pat. Nos. 4,026,173 (Livick), 4,469,318 (Slavic), and 4,485,711 (Schnell). These devices, however, are adapted for pushing and guiding the workpiece though the cutting area, and are generally not suitable for use with a radial arm saw wherein the saw blade is moved through the workpiece. Accordingly, there exists a need for improvements directed to radial arm saws directed to protecting operators from injury by securing the workpiece. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention overcomes the disadvantages and shortcomings in the art by adapting a radial arm saw with a safety top configured with a cutting box enclosure for containing and collecting substantially all of the sawdust generated when in use. The safety top further includes spring biased push blocks that function to hold the work piece in place during the sawing process while maintaining the user&#39;s hands safely away from the saw blade. In accordance with the present invention, a radial arm saw is adapted with a safety top providing an improved work surface, a fully integrated structure that contains and captures substantially all of the sawdust and particles generated by the saw, and integrated push blocks that are mechanically biased to secure the workpiece in engagement with the fence. 
   Accordingly, it is an object of the present invention to provide an improved safety top for use with radial arm saws. 
   Another object of the present invention is to provide an improved dust collection system for use with radial arm saws. 
   Still another object of the present invention is to provide advancements in control systems for radial arm saws. 
   In accordance with these and other objects, which will become apparent hereinafter, the instant invention will now be described with particular reference to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       FIG. 1  depicts a typical radial arm saw of the prior art; 
       FIG. 2  depicts a radial arm saw adapted with a safety top in accordance with the present invention; 
       FIG. 3  illustrates cutting of a wood work piece using a radial arm saw adapted with a safety top in accordance with the present invention; 
       FIG. 4  is a bottom view of the safety top showing alternate mechanical biasing systems for the push handles; 
       FIG. 5  is a top view of the safety top wherein the saw is positioned to cut a wood work piece; 
       FIG. 6  is a top view of the safety top wherein the work piece has been cut; and 
       FIG. 7  depicts a control panel for use with the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  depicts a radial arm saw  10  typical of prior art saws to which the present invention most directly pertains. The typical radial arm saw  10  includes a work table  20  having a horizontal flat top work surface  22  with a vertically projecting backstop  24 , commonly referred to as a rip fence. The material to be cut, such as a piece of wood, is supported on work surface  22  in abutting relation with fence  24 . A vertical column  30  extends upwardly from the back of work table  20 . Extending horizontally from the top of column  30  is a radial arm  32 , which is capable of rotation about the column, but which is generally positioned over the top of the table. A rotary power saw  40  is suspended below the radial arm by a carriage adapted for travel along the length of radial arm  32 . Power saw  40  includes a rotating blade  42 , a protective blade shroud  44 , a motor housing  46 , and a handle  48 . As noted above, blade shroud  44  is often configured to function as a dust collecting shroud by attachment of a shop vac dust collector thereto. In most operations, the saw is positioned over the work table and is moved along the radial arm to cut a workpiece positioned on the work surface when pulled by the user such that the saw moves from behind the fence through the workpiece to be cut. 
     FIG. 2  depicts a radial arm saw adapted with a safety top assembly, generally referenced as  100 , an improved control system, which includes a control panel  200 , according to the present invention. Safety top  100  is preferably fabricated from a durable material. In a preferred embodiment, safety top  100  is fabricated from sheets phynolic material, which sheets are known for their strength, high heat resistance and flame retardancy. It should be noted, however, that any suitable material is considered within the scope of the present invention. Safety top  100  is preferably a fully assembled structure adapted for mounting directly on to a radial arm saw with minimal if any modification required. 
   Safety top  100  includes a generally planar work surface  102  and a backstop or rip fence  104  (hereinafter “fence”) vertically projecting therefrom. Work surface  102  defines a pair of slotted apertures  106  that function as guide slots for push handles  108 . Each push handle  108  includes a base  108 A, a vertical end wall  108 B for engaging a workpiece, and a cutout portion  108 C to facilitate grasping thereof by the user. Base  108 A includes a downwardly projecting tongue sized for slidable inserted engagement with slotted aperture  106 .  FIG. 3  depicts a wood workpiece, such as a two-by-four disposed between push handles  108  and rip fence  104 . 
   Each push handle  108  is mechanically biased toward fence  104  by a spring loaded biasing mechanism preferably disposed on the bottom surface of work surface  102 .  FIG. 4  shows a bottom view of safety top  100  and discloses a preferred helical spring loaded embodiment of the mechanical biasing system depicted on the right hand side of  FIG. 4B , which embodiment is generally referenced as  110 , and an alternate auto-retracting embodiment mechanical biasing system depicted on the left hand side of  FIG. 4B , which embodiment is generally referenced as  120 . The helical spring mechanical biasing system  110  includes a plurality of anchors  112  fastened to the underside of work surface, and an anchor  114  fastened to the lower portion of push handle  108 . A spring biased cable and pulley system is connected to anchors  112  and  114 . More particularly, the spring biased cable and pulley system includes a chain section  116  connected at one end thereof to an anchor  112 , a helical spring  117  connected on one end thereof to chain  116  and connected at the opposite end thereof to a first pulley  118 . A cable  119  is routed in a two pulley configuration with opposing cable ends connected to a fixed anchor  112  and anchor  114  respectively thereby realizing a mechanical advantage. The provision of chain section  116  allows for adjustment of the tension by adjustable connection of individual links to anchor  112 . The alternate embodiment mechanical biasing system  120  includes an automatic retraction apparatus  122  connected to the lower portion of push handle  108  by a cable  124 . Automatic retraction apparatus  122  is generally characterized as providing a retraction force of a substantially constant level by use of internal spring mechanisms. It should be noted, however, that any suitable biasing system, whether mechanical or electrical is considered within the scope of the present invention. As should be apparent, the mechanical biasing systems function to urge push handles  108  toward rip fence  104  so as to secure a piece of wood in place for the sawing process. 
   Safety top  100  further includes dust collecting cutting box  130  mounted on and projecting above work surface  102 . Cutting box  130  is preferably mounted in alignment with power saw  40 , and particularly saw blade  42  for reasons more fully discussed hereinbelow. Cutting box  130  is bounded by a floor formed by the work surface  102 , and further includes a top  132 , opposing sides  134 , and front and rear walls  136 . Top  132  defines a plurality of slotted apertures (“slots”), including a saw blade slot  137  aligned with saw blade  42 , and left and right slotted apertures  137  disposed on opposing sides of blade slot  137  and in parallel relation therewith. Saw blade slot  137  allows saw blade  42  to pass below cutting box top  132  during the sawing process. Left and right slotted apertures  138  function to provide the user with a line of sight through cutting box top  132  to the cutting area disposed below. Cutting box sides  134  include portions thereof formed by brush bristles  135  connected to and projecting downwardly from top  132 , extending forward from fence  104 . Brush bristles  135  allow a work piece to be inserted into cutting box  130  and automatically form a seal to contain saw dust within cutting box  130 . The present invention further contemplates providing the saw portion with a specially adapted semi-circular shroud  150  in partial covering relation with the saw blade. Shroud  150  defines a bottom opening having a generally rectangular cross-section, which opening includes brush bristles  152  attached to the peripheral edge thereof. Shroud bristles  152  project downwardly from shroud  150  and are in sweeping contact with the cutting box top  132  thereby forming a dust seal between shroud  150  and top  132  as the saw moves back and forth while cutting the work piece. 
   Cutting box  130  thus defines an internal chamber wherein the rotating saw blade meets the work piece during the cutting process and functions to contain the sawdust and wood chips generated as the blade cuts through the wood. Accordingly, cutting box  130  is further adapted for connection to an external dust collection system. More particularly, cutting box  130  is adapted with first and second dust collection outlet ports, referenced as  160  and  162  respectively. Each outlet port provides a connection point for attachment of a hose from a vacuum generating external dust collection system. Since vacuum type dust collection systems are well known, those systems shall not be further detailed. Outlet port  160  is preferably located rearward along cutting box side  134  and thus places the interior of cutting box  130  in fluid communication with the external dust collection system. As best depicted in  FIG. 4 , second outlet port  162  is defined by a dust collecting tray  164  disposed beneath work surface  102  in alignment with a slotted aperture  166  defined bottom of work surface  102 . First and second outlet ports are preferably connected to a common dust collection system by a vacuum hose adapted with a Y-fitting. 
   As best depicted in  FIG. 3 , safety top  100  further includes a flexible, generally flat, strip of sealing material  170  having a first end thereof attached to shroud  150  and a second end thereof  172  hanging or draping down the back side of safety top  100 . Sealing strip  170  further includes opposing edges thereof riding within grooves formed on opposing sides of saw blade slot  137 . Accordingly, as the saw is moved forward during the cutting process, sealing strip  170  is pulled in trailing relation with shroud  150  so as to cover or seal that portion of saw blade slot  137  behind the saw thereby providing a seal and preventing saw dust from escaping. As the saw is moved rearward during the cutting process sealing strip  170  is pushed rearward while traveling within grooves formed on opposing sides of saw blade slot  137 . As should be apparent, any sawdust generated during operation of the radial arm saw adapted with a safety top  100  in accordance with the present invention will be contained within cutting box  130  and will be removed therefrom via dust collection outlet ports  160  and  162 . 
   As best depicted in  FIGS. 5 and 6 , radial arm saw safety top  102  further includes a laser alignment device  180  for projecting a light beam  182  over the work piece to insure proper alignment and precise cutting. In a preferred embodiment, laser alignment device  180  is mounted within cutting box  130  and oriented so as to project a light beam over the work piece and along the cutting plane formed by the edge of the saw blade. Light beam  182  thus provides visible indication as to exactly where the saw blade will intersect the work piece. Light beam  182  may be visible to the operator through any of cutting box top slots  137  or  138 . 
   As further illustrated in  FIG. 2 , the present invention may further include a control panel, referenced as  200  which functions to provide safe and efficient operation of the radial arm saw, particularly for saws operating in retail store environments, such as saws operating in home improvement and hardware stores. Control panel  200  provides a primary connection to electrical power, such as 208VAC, 230 VAC, or 460VAC electrical power and includes a step-down electrical transformer capable of 24 VAC output. The ability of control panel  200  to operate using a range of voltages is considered important since the power available at different locations often varies. Control panel  200  includes a keypad  202  that provides an input device to restrict operation to authorized users who enter an appropriate authorization code. A power supply is connected to the 24 VAC output for providing DC power to keypad  202 . Control panel  200  further includes a main disconnect switch  204  that enables quick disconnection of power to the saw and various components. In addition, a push-start/pull-stop control button  206  is provided to initiate or discontinue operation. Further, control panel  200  includes a visual alarm beacon  208  that is configured to flash when power is supplied to the radial arm saw systems, and an alarm horn  210  that is configured to generate an audible sound after a predetermined time period to indicate that the radial arm saw is about to shut down. 
   The operating sequence for a radial arm saw adapted with a control panel according to the present invention is a follows. A red indicator light  202 A on the keypad indicates that power is being supplied to the radial arm saw control panel. The user enters the appropriate security code on the keypad to initiate operation. As should be apparent, any suitable code may be used. Upon entry of the appropriate code, a light  206 A on control button  206  illuminates indicating that a predetermined operation period, such as five minutes, has begun. The user then must pull control button  206  to automatically supply power from the control panel to the radial arm saw and dust collection system, at which time beacon  208  is activated thus providing a visual signal/warning that power has been supplied and the systems are operational. Shortly before expiration of the predetermined operation period (e.g.  30  seconds prior to expiration) alarm horn  210  sounds as a signal that the saw will automatically shut down shortly. While the system is programmed to allow operation for a predetermined period of time before automatically shutting down, the period of operation may be extended by re-entering the authorization code. If, at any time, the operator wishes to manually shut the systems down he simply must push control button  206 . 
   The instant invention has been shown and described herein in what is considered to be the most practical and preferred embodiment. It is recognized, however, that departures may be made therefrom within the scope of the invention and that obvious modifications will occur to a person skilled in the art.