Abstract:
A below-table blade enclosure for a table saw protects the health and safety of the person operating the saw, by enclosing the saw blade, and thereby protecting the operator from exposure to hazardous and potentially carcinogenic saw dust. The blade enclosure contains and collects the saw dust, which is removed from the blade enclosure by an external dust collecting system, for example via a vacuum hose.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
       [0001]    This application relates to subject-matter more fully explained in my co-pending application Ser. No. 12/______, entitled HEALTH AND SAFETY SYSTEM FOR A TABLE SAW (Attorney Docket 873-013-101), filed the same day as the present application, the disclosure of which is hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to systems for power saws, providing improved health and safety during operation. 
       BACKGROUND AND SUMMARY OF THE INVENTION 
       [0003]    Table saws are power tools used to cut work pieces of wood, plastic and other materials. Such saws are among the most widely used power tools in woodworking and materials processing shops, carpentry and building work sites. Four general classes of table saws are in common use including bench top table saws, contractor table saws, cabinet table saws and hybrid table saws. 
         [0004]    A table saw includes a flat surface, or table, with a circular saw blade extending vertically up through a slot in the table. The saw blade is mounted on an arbor which is driven by an electric motor (either directly, by belt, or by gears). 
         [0000]    The saw operator slides a workpiece on the table against and past the blade while the circular blade revolves at a high rate of speed (typically about 4,000 rpm) and cuts through the workpiece.
 
The thickness of the workpiece that can be sawed completely through, or the depth of the cut into the workpiece, is controlled by moving a saw motor trunnion or carriage, holding the motor, saw arbor and saw blade, up or down, relative to the saw table top. The higher the blade protrudes above the table, the deeper the cut that is made in the workpiece. Commonly, the cut into the workpiece is made perpendicular to the saw table, but most table saws also can be adjusted to make cuts at angle of up to 45 degrees from the perpendicular. Such angle or bevel cuts are made by rotating the saw motor carriage from the perpendicular such that the angle of the motor, saw motor, motor arbor and blade are adjusted to provide the desired cutting angle. Table saws are generally designed to allow rotation of the carriage, motor, arbor and blade either to the left or to the right (but not both).
 
         [0005]    Table saws typically are provided with various pieces of auxiliary equipment including a rip fence to guide a work piece make rip cuts, that is to cut work pieces generally with the grain, and a miter gauge to cut work pieces perpendicular to or generally at an angle to the grain. A splitter, a vertical projection located behind the saw blade, typically either a pin or a fin shaped piece of metal, is also typically provided as a standard or optional attachment for table saws. The splitter is typically slightly narrower in width than the blade and is aligned directly in line with the blade kerf. Saws also typically are provided with an anti-kickback device that attaches to the splitter, as well as a hinged blade cover also attached to the splitter. Saws usually have an easily replaceable insert around the blade in the table top. This allows the use of special-purpose cutters and inserts as may be required for various cutting operations. 
         [0006]    All species of saw dust have recently been classified as carcinogenic and the finer particles are considered the most harmful. Fine saw dust, such as that generated by a table saw, has been determined to be a human carcinogen and is believed to be implicated in many other respiratory ailments as well. The carcinogenicity of saw dust has been recognized by, among others, the American Conference of Government and Industrial Hygienists (ACGIH), the National Institute of Occupational Safety and Health (NIOSH) and the International Agency for Research on Cancer (IARC). Chronic exposure to saw dust has been implicated as a cause of fibrosis, emphysema, bronchitis, asthma, respiratory allergies and dermatitis. Additionally, substantial research also indicates that many of the chemicals including various glues, adhesives and preservatives used in processed wood products are highly toxic when inhaled as a component of saw dust. Recent research suggests that chronic exposure to saw dust may prove to be an even greater danger to saw operators than the perhaps more immediately obvious risk of serious trauma injury. 
         [0007]    Partial blade enclosures intended for collection of saw dust expelled below the table surface are within the known prior art such as U.S. Pat. No. 6,925,919 issued to LIAO et al., U.S. Pat. No. 4,255,995 issued to J. FRANKLIN CONNOR, U.S. Pat. No. 4,063,478 issued to HANS STUY, and U.S. Pat. No. 4,721,023 issued to BARTLETT et. al. These and similar prior art below-table enclosures intended for dust containment and extraction suffer from shortcomings related to inadequate seal thereby allowing significant amounts of sawdust to escape the enclosure where the seals are inadequate, particularly around the rotating saw arbor and the top of the enclosure at the table insert. Since most of dust generated normally is ejected from the saw below the table it is important to maintain adequate sealing to insure maximum effectiveness of the dust containment and extraction device. 
         [0008]    The most common and oldest prior-art dust collection method for the cabinet type or hybrid table saw allows the sawdust to simply accumulate inside the table saw base and extract it from the base using ducting to a powerful central dust collector system. More recent prior-art has introduced various designs for attaching cloth bags under the base to capture saw dust. Both of these methods fall far short of their intended goal and provide inadequate capture of dust considering the several recently discovered health hazards associated with saw dust exposure. The present invention more effectively captures and extracts saw dust from very close to the saw blade or cutter head and thus protects the saw operator from inhaling said dust. Many woodworkers as well as industrial safety officials have recently come to view, as imperative, increased control and removal of saw dust as close to the source of generation as possible, thereby minimizing environmental exposure of saw operators to these hazards. Although the problem of saw dust control has long been known, it is widely recognized that prior art dust removal efforts have failed to adequately solve this problem. Thus, there exists a need for a table saw with improved dust containment and collection system that significantly reduces exposure of table saw operators to the long term risks of exposure to carcinogenic saw dust. The below-table blade enclosure or guard of the present invention provides a significantly improved dust containment and collection enclosure that may be retrofitted to many existing table saws and, alternatively, may be incorporated into many new table saw designs. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a perspective view of a blade enclosure for saw dust control in accordance with one embodiment of the present invention. 
           [0010]      FIG. 2  is a perspective view of a mounting bracket for a blade enclosure unit for a table saw in accordance with one embodiment of the present invention. 
           [0011]      FIG. 3  is a front view of a blade enclosure for saw dust control in accordance with one embodiment of the present invention. 
           [0012]      FIG. 4  is a rear view of a blade enclosure for saw dust control in accordance with one embodiment of the present invention. 
           [0013]      FIG. 5  is a detailed side elevation, in a partially exploded view, of a preferred embodiment of a blade enclosure, for a table saw in accordance with the present invention. 
           [0014]      FIG. 6  is a perspective view of a secondary insert gasket for use with a blade enclosure for a table saw in accordance with one embodiment of the present invention. 
           [0015]      FIG. 7  is a perspective view of a secondary insert gasket, showing the position of the saw blade, for use with a blade enclosure for a table saw in accordance with one embodiment of the present invention. 
           [0016]      FIG. 8  is a detailed top elevation, in a partially exploded view, of a preferred embodiment of a secondary insert gasket, in accordance with the present invention; AND 
           [0017]      FIG. 9  is a perspective view of a connection to a dust collection and containment system for a table saw blade enclosure in accordance with one embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    An exemplary embodiment of a blade enclosure for dust collection and containment in accordance with the present invention is illustrated schematically in  FIGS. 1 and 3 . The table saw to which such blade enclosure is adapted may be any type, model or configuration of table saw suitable for cutting wood, plastic or other suitable material that incorporates one or more of the various aspects of the present invention. The present invention includes complete saws as well as systems, parts, pieces or kits of parts which may be mounted on existing table saws to adapt or retrofit them in accordance with one or more of the various aspects of the present invention. 
         [0019]    One aspect of the present invention is a blade enclosure for saw dust containment and collection, as shown in  FIGS. 1 through 5 , for a table saw which may be used with a dust containment and collection system for a table saw. Blade enclosures according to the present invention contribute to safe saw operation, not only by containing and collecting hazardous saw dust but also by preventing exposure of the saw operator to the handling of said hazardous saw dust. Blade enclosures of the present invention are mounted below the saw table  62  ( FIG. 1 ), generally on the tiltable portion of the saw and motor frame carriage  61 , such that blade enclosure surrounds the blade, except at the upper edge of the saw blade where the blade passes vertically through the saw table  62  in order to cut the workpiece. 
         [0020]    Blade enclosures of the present invention incorporate one or more of several aspects of the present invention disclosed in detail herein, and shown including: a blade enclosure  50  ( FIG. 3 ), a removable blade cover  51 , a blade enclosure vacuum seal  52  ( FIG. 5 ), a seal  56  between the blade enclosure and the front cover, a front cover arbor vacuum seal  83  ( FIG. 3 ), a blade enclosure mounting bracket  39  ( FIGS. 1 and 2 ), which replaces the manufacturer&#39;s supplied splitter mounting bracket and splitter mounting bolt in this exemplary embodiment of the invention. Also incorporated in this invention are blade enclosure bracket mounting bolts  58   FIG. 2 , a blade enclosure mounting screw  87  ( FIG. 2 ), a secondary saw table insert which functions as a gasket  54  (FIGS.  6 , 7 ), and flexible hose connector  86  ( FIG. 9 ) to a dust containment and collection system. A blade enclosure of the present invention, when designed to be retrofitted to an existing table saw, must be designed to fit the below the table structure and design of that particular saw. The exemplary blade enclosure, of  FIGS. 1 through 5 , is designed and adapted to be mounted on many models of existing Delta UNISAW® table saws which have been widely used throughout the world for over fifty years. It will be readily appreciated that one of ordinary skill, provided the disclosures herein, would readily be able to design and manufacture a suitable blade enclosure for many other models of table saws. 
         [0021]    Table saws are designed to permit the saw blade, saw arbor  60  and saw motor carriage  61  ( FIG. 1 ), to be adjustably titled at angles of up to 45 degrees relative to the normal upright or vertical saw blade position. This permits the saw operator to make bevel cuts of up to 45 degrees. The blade enclosure  50  ( FIG. 1 ) must, therefore, be shaped and mounted to accommodate such adjustable tilting of the saw blade, saw arbor  60  and to permit saw motor carriage  61  to be adjustably titled at angles of up to 45 degrees without interference or obstruction between blade enclosure  50  or blade cover  51  and the underside of saw table  62  or the underside of saw table insert  57 . 
         [0022]    It will be appreciated that one of ordinary skill in the design, manufacture or operation of table saws would, if given the disclosures herein, understand that there are many ways in which blade enclosure  50  and front cover  51  could be so shaped and mounted. One of ordinary skill in the design, manufacture or operation of table saws, provided the disclosures herein, would readily be able to design and manufacture a suitable mount for a blade enclosure for any model of table saw. Exemplary rear mounting bracket  39  is mounted to saw motor carriage  61  using bolts  58 , as shown in  FIG. 2 . 
         [0000]    Blade enclosure  50  is then mounted to rear mounting bracket  39 , which is threaded, using bolt  87   FIG. 2 . Blade enclosure  50  is also mounted to that portion of saw motor carriage  61  adjacent to the front of the saw using bolt  59   FIG. 5 . Bolt  59  fits, and is bolted into, an existing threaded bolt hole in saw motor carriage  61 . Said threaded bolt hole is used in many models of table saw, including many models of Delta UNISAW® table saws, to support a saw dust chip deflector, which saw dust chip deflector is entirely replaced by blade enclosure  50  in the present invention. When the saw motor is tilted, to permit bevel cutting, the blade enclosure will thus also be equally tilted. 
         [0023]    The blade cover  51  ( FIG. 3 ) must be carefully designed to permit the enclosed saw blade to be tilted through the full range permitted by design of the saw, without being impeded by, or interfering with, any part or feature of the saw interior when the secondary table insert gasket is removed. This can be accomplished by careful attention to design of the geometry, shape and dimensions of the blade cover  51 . As previously indicated, the exemplary blade cover  51  is designed to retrofit a blade enclosure of the present invention on a Delta UNISAW® table saw. Blade cover  51  is mounted to rear blade enclosure  50  with thumbscrews  81  ( FIGS. 3 and 5 ) that may be hand tightened and easily removed for changing saw blades. It will be appreciated that one of ordinary skill in the design, manufacture or operation of table saws, if given the disclosures herein, would readily be able to design and manufacture a suitable mount for a blade enclosure for any model of table saw. For complete table saw of the present invention, the blade enclosure cover and the saw interior can be designed together as a system, to permit tilting of the saw blade. 
         [0024]    The blade enclosure  50  and blade cover  51  may be made of any suitable material. Preferably, the enclosure should be primarily fabricated of a durable yet economical material such as steel, fiberglass, graphite, fiber composite or thermoplastic. 
         [0025]    Table saws must permit the saw blade and saw arbor  60  ( FIG. 1 ) to be adjusted vertically, relative to the saw motor carriage  61 , and also to the saw table  62 , to permit the saw to cut work pieces of different thicknesses. The blade enclosure  50  must therefore permit the saw arbor to pass through the blade enclosure at all vertical positions from the centerline of the blade enclosure at the lowest blade position to its uppermost margin. It will be appreciated that one of ordinary skill in the design, manufacture or operation of table saws would, if given the disclosures herein, understand that there are a number of methods in which the blade enclosure  50 , and arbor seals,  52  ( FIG. 4 ) could permit such vertical movement of the saw arbor. An exemplary blade enclosure according to the present invention accommodates vertical adjustment of the arbor by means of a curved slot  84  ( FIG. 5 ), sealed with one or more replaceable strip brush seals  52 , mounted to the body of the blade enclosure  50  by mounting channels  82  as shown in  FIGS. 4 and 5 . 
         [0026]    The dust control and collection features of blade enclosures of the present invention are achieved by connection of the blade enclosure  50  to a vacuum dust control and collection system with a 2.00″-2.25″ (50 mm-57 mm) inner diameter (ID) flexible hose and capable of maintaining an nominal air velocity of 1500-2000 feet per minute (760-1014 centimeters per second) at the table insert throat plate  57  ( FIG. 8 ), level with the table surface. Exemplary blade enclosure  50  is thus provided with an exhaust port  55  ( FIGS. 3 ,  4 ,  5 ). Preferably, one chooses a ratio, between a cross-sectional area of the longitudinal slot in table insert  57 , and a cross-sectional area of outlet port  55  which is suitable to facilitate a desirably high airflow rate for entraining the saw dust particles and particulates. 
         [0000]    It will be readily appreciated that one of ordinary skill, if given the disclosures herein, would readily be able to design and manufacture a suitable dust collection system connection port. Effective functioning of the dust containment and collection aspects of the blade enclosure requires that the blade enclosure  50  and blade cover  51  be carefully designed and constructed, so as to form a system capable of being sufficiently sealed from air leakage and to maintain sufficient vacuum integrity, in order to substantially prevent saw dust leakage into the saw interior or into the air surrounding the saw. The external vacuum or negative air flow employed must be sufficient to contain substantially all the dust produced by the saw within the blade enclosure, and to move such dust out of the blade enclosure and to the dust collection system at approximately the same rate at which dust is produced by the sawing blade. It will be appreciated that one of ordinary skill in the design, manufacture or operation of table saws, if given the disclosures herein, would readily be able to design and manufacture suitable seals for the blade enclosure to maintain a vacuum sufficient to accomplish effective dust containment and removal. The exemplary blade enclosure  50  and cover  51  are provided with a gasket seal  56  ( FIG. 5 ), attached to the blade enclosure  50  that provides a seal between the blade cover  51  and blade enclosure. This gasket seal  56  may be made of any suitable material including rubber, cork, felt, synthetic fabric, polymers or composites. 
         [0027]    The exemplary preferred blade enclosure  50  is provided with a replaceable brush seal  83  ( FIG. 3 ), attached to the blade enclosure  50  to provide a seal over the arbor cutout  85  ( FIG. 5 ) and provides a seal between the blade enclosure  50  and the saw blade arbor  60  ( FIG. 1 ). As the height of the saw blade is adjusted upward, the rapidly rotating and vertically adjustable saw arbor  60  ( FIG. 1 ) will partially project through the front cover cutout  85  ( FIG. 5 ) at the upper range of blade height adjustment. 
         [0000]    Replaceable brush seal  83  ( FIG. 3 ) is intended to help maintain the strength of vacuum air flow within the enclosure  50 , and to minimize saw dust leakage through cutout  85  when the saw is operating in the upper range of blade height adjustment, causing the saw blade arbor to project slightly through the front cover cutout  85  ( FIG. 5 ). 
         [0028]    It will be appreciated that one of ordinary skill in the design, manufacture or operation of table saws, if given the disclosures herein, would readily be able to design and manufacture suitable seals for the blade enclosure/saw arbor interface, of many configurations and designs and to manufacture such seals from many suitable materials or combinations of materials. 
         [0000]    Replaceable seals  83  ( FIG. 3) and 52  ( FIGS. 4-5 ) may be made of any suitable material, including one or more fiber brushes, expanded foam, rubber, cork, felt, synthetic fabric, polymers or composites that will both provide an adequate seal and that will accommodate rotating saw arbor and that will further accommodate vertical adjustment of the saw arbor  60  (FIG.), relative to the saw motor carriage  61 . Brush seals  83  ( FIG. 3) and 52  ( FIGS. 4-5 ) provide the required seal while accommodating saw arbor  60  ( FIG. 1 ) rotational and height adjustment movement, in the exemplary embodiment shown. 
         [0029]    Vacuum integrity within the blade enclosure, and thus effectiveness of the dust control and collection system, can be further improved in table saws of the present invention by provision of a secondary insert gasket  54  ( FIGS. 6-7 ), which provides a seal between saw table  62  ( FIG. 7 ) and the upper edge of blade enclosure  50  and of blade cover  51 , as shown in  FIG. 8 . Table saws are typically provided with a port, in the saw table  62 , that is substantially larger than needed to accommodate the saw blade. In addition, table saws are typically provided with a replaceable table insert  57  ( FIG. 8 ) which closely fits into the table port and which closely surrounds different sized blades or cutters, as they project up through the top of the saw table  62 . When these standard inserts are in place, there remains a considerable space between the bottom surface of the insert and the upper edge of blade enclosure  50  and blade cover  51 . A secondary table insert  54  (FIGS.  6 , 7 , 8 ) is employed in the present invention to fill the space between the upper edge of blade enclosure  50  and blade cover  51  and the bottom surface of standard saw table insert  57  which provides an improved vacuum seal for the blade enclosure  50  and blade cover  51 . 
         [0030]    Standard table inserts such as  57  ( FIG. 8 ), are provided with four leveling set screws  40  ( FIG. 8 ), which normally bear against the four insert support tabs  88  ( FIG. 7 ), which are cast into the saw table top  62  ( FIGS. 7-8 ), and are used to precisely adjust the top surface level of the table insert to match the surface level of the saw table. In the present embodiment, to compress table insert gasket  54  ( FIG. 8 ), against the blade enclosure  50  ( FIG. 3 ), and the blade enclosure cover  51  ( FIG. 3 ), the four insert support tabs have been threaded to accommodate longer set screws intended to hold the table insert  57  level and firmly in place, and to compress the table insert gasket  54  against the blade enclosure. 
         [0031]    Saw table insert gasket  54 , may be made of any suitable compressible gasket material including foam board, PVC foam board, polypropylene, plastic, foam rubber, foam core, or any functionally suitable and cost effective material. Saw table insert  54  should be constructed of a material that will be easily and safely cut by the saw blade, such that no hazard will be posed to the saw operator, in the event of any accidental contact between the table insert gasket  54 , with the saw blade. It will be appreciated that one of ordinary skill in the design, manufacture or operation of table saws, if given the disclosures herein, would readily be able to design and manufacture suitable table saw insert gaskets of many configurations and designs, and to manufacture such seals from many suitable materials or combinations of materials. 
         [0032]    A flexible hose, connecting the blade enclosure to a vacuum or dust collection system, may be connected to blade enclosure port  55  and may exit the table saw at any convenient location. In a preferred embodiment, a convenient flexible hose fitting  86  ( FIG. 9 ) is provided and attached to the base of the table saw. A length of flexible hose is connected to blade enclosure port  55 , is run through the base cabinet of the table saw, and is connected to flexible hose fitting  86  inside the saw cabinet. The external side of flexible hose fitting  86  may then be connected by a length of flexible hose to a dust collector or a suitable source of vacuum. It will be appreciated that one of ordinary skill in the design, manufacture or operation of table saws would, if given the disclosures herein, understand that there are many ways in which the below-table blade enclosure of the present invention could be connected to a dust collection and containment system.