Abstract:
A scraper removes debris from under a work table, particularly slag resulting from cutting of metal. A pair of parallel tracks extends along opposite sides of a collection area under the table. A blade carriage is carried on the tracks and driven between forward and rearward positions. A pair of arm assemblies are connected to opposite sides of the blade and pivotally mounted to the carriage for moving the blade between a scraping position and a retracted position. A forward notch on each of the tracks is contacted by the arm assembly after reaching the forward position to cause the arm to move the blade from the scraping position to the retracted position during rearward movement. A rearward notch on each of the tracks is contacted by the arm assembly after reaching the rearward position and commencing forward movement to cause the arm to move the blade from the retracted position to the scraping position. The carriage is moved by continuous cables.

Description:
This invention claims the provisional application filing date of Jun. 25, 2002, Ser. No. 60/391,465. 

   FIELD OF THE INVENTION 
   This invention relates in general to devices for removing debris from under a work table, and in particular to a scraping blade assembly for removing slag from under a torch cutting table. 
   BACKGROUND OF THE INVENTION 
   One method for cutting metal plate is to place the plate on a table that has a grid. Torches are mounted to a gantry and moved longitudinally and laterally over the table to cut the metal. Molten metal where the torch cuts falls through the grid to a collection area below the table. This debris, typically called slag, builds up and must be removed. 
   One type of removal device uses a blade that is mounted to a blade carriage carried on tracks under the table. Typically the blade carriage is driven by an electrical motor and a rack and pinion gear arrangement on the tracks. Debris from the table tends to fall on the gear arrangement and the motor. The debris hampers operation of the blade carriage and must be cleaned by other means. 
   SUMMARY OF THE INVENTION 
   The apparatus of this invention has a blade carriage located under a work table. A drive mechanism conveys the blade carriage under the table between forward and rearward positions. A blade is mounted to the blade carriage by an arm assembly. The arm assembly moves the blade between a scraping position, in which a lower edge of the blade contacts the collection surface, and a retracted position in which the lower edge of the blade is spaced above the collection surface. 
   A forward trip member is contacted by the arm assembly at the forward position to cause the arm to move the blade from the scraping position to the retracted position. A rearward trip member is contacted by the arm assembly at the rearward position to cause the arm to move the blade from the retracted position to the scraping position. 
   In the preferred embodiment, the arm has a pivot end that is mounted to a pivot point on the blade carriage, and a blade end that is secured to the blade. A pawl is rotatably mounted to the blade end of the arm, the pawl rotating under the blade end of the arm to elevate the blade end of the arm and move the blade to the retracted position when contacting the forward trip member as the blade carriage moves rearward. The pawl rotates out from under the blade end of the arm to lower the blade end of the arm and move the blade to the scraping position when contacting the rearward trip member as the blade carriage moves forward. 
   The drive mechanism for moving the blade carriage in the preferred embodiment has a driven drum mounted adjacent one side of the collection area. A left-side cable having first and second ends is secured to a left side of the blade carriage and extends along a left side of the collection area to the drum. A right-side cable having first and second ends secured to a right side of the blade carriage and extends along a right side of the collection area to the drum. Rotating the drum in one direction causes the cables to move the blade carriage in a forward direction, and rotating the drum in an opposite direction causes the cables to move the blade carriage in a rearward direction. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features believed to be characteristic of the invention are set forth in the appended claims. The invention itself however, as well as a preferred mode of use, further objects and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings. 
       FIG. 1  is a perspective view of a cutting table constructed according to the present invention. 
       FIG. 2  is a perspective view of a blade assembly of the table of  FIG. 1 . 
       FIG. 3  is a schematic, plan view of a cable drive system of the table of  FIG. 1 . 
       FIG. 4  is a left side view of the right portion of the blade assembly of  FIG. 2 , the blade assembly located on tracks, a pawl being in a first position. 
       FIG. 5  is a side view of a portion of the right side shown in  FIG. 4 , the pawl being moved to a second position. 
       FIG. 6  is a left side view of the blade assembly of  FIG. 2  on a forward end of the tracks of  FIG. 4 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to the figures, a cutting table  11  has at least one cutting torch  13  on moveable gantry  15 , table  11  being shown in  FIG. 1  with three torches  13 . Table  11  is a rectangular box structure, having vertical walls  17 ,  19  with a grid extending between (not shown) for supporting a workpiece  20  and gantry  15  at an upper portion of table  11 . Gantry  15  and workpiece  20  may rest on separate sets of rails (not shown). Torches  13  are used to cut workpiece  20 , producing waste material in the form of gaseous materials and solid materials, called slag. The gases are vented away from table  11 , but the slag falls through the upper portion of table  11  and into the volume between walls  17 ,  19 . 
   Inclined plates  21 ,  23  are mounted to the inner surfaces of walls  17 ,  19 , respectively, creating a longitudinal funnel for directing the slag toward a collection surface  25  of table  11 . A blade assembly  27  is moveable longitudinally and rides on tracks  29 ,  31  located on either side of surface  25 . Plates  21 ,  23  extend toward the centerline of table  11  to position the inner edges of plates  21 ,  23  such that slag falls from plates  21 ,  23  onto collection surface  25  between tracks  29 ,  31 . Blade assembly  27  has a blade  33  for scraping collection surface  25 , assembly  27  reciprocating between forward and rearward ends of table  11  for moving accumulated slag to the forward end of table  11  for collection and disposal. The words “forward” and “rearward” are used for convenience only. A mesh or grate  34  may be located above plates  21 ,  23 . 
   Blade assembly  27  is illustrated in  FIG. 2 . Shafts  35 ,  37  extend through and connect forward and rearward portions of longitudinal members  39 ,  41 , forming a rectangular perimeter frame. Slider blocks  43 , which are preferably formed of plastic or cast iron, are mounted on the outer ends of shafts  35 ,  37 , the lower surface  45  of each block  43  being lower than the lower edge of members  39 ,  41  to provide a sliding support surface for assembly  27 . Blocks  43  slide on top of tracks  29 ,  31 . 
   Blade  33  is attached to a rear portion of each of two pivoting arms or arms  47 ,  49 , blade  33  being located between arms  47 ,  49 . The forward end of each arm  47 ,  49  is pivotally connected to shaft  35 , and the rearward end is moveable vertically relative to shaft  37 . A pawl  50  is pivotally connected to the rearward end of each arm  47 ,  49 , pawls  50  pivoting between a scraping position, in which blade  33  is in a lower, scraping position during a forward stroke, to a retracted position, in which blade  33  is in a retracted position during a return stroke. Each member  39 ,  41  has a connector  51  on its upper edge for fixedly receiving a cable  53 ,  55 , cables  53 ,  55  being driven for moving assembly  27 . 
     FIG. 3  illustrates cable system  57  for moving assembly  27 . Grooved drums  59 ,  61  are located to one side of cable system  57 , drum  59  being driven by a motor (not shown). Cables  53 ,  55  are coiled around drums  59 ,  61  and are routed through a series of pulleys, both ends of each cable  53 ,  55  being affixed to the corresponding connector  51  on members  39 ,  41  for creating continuous cable loops. Pulleys  60 ,  62 ,  63 , are located at a rear portion of table  11  on what will be considered for convenience only, a left side of the collection surface  25  ( FIG. 1 ). Pulleys  65 ,  67 ,  69 ,  71  are located at a forward portion of table  11 . Pulleys  65 ,  71  are located on the opposite lateral side, or left side of table  11  from drums  59 ,  61 , whereas pulleys  67 ,  69  are located near drums  59 ,  61 . Pulleys  70 ,  72  and  73  are located at the rearward end of table  11  on the right side. 
   Cable  53  begins at left-side connector  51  on member  39 , then extends rearward around first left rearward pulleys  60 ,  63 . From there, cable  53  extends around second left rearward pulley  62  forward to a first left-side forward pulley  65  and across to a first forward right-side pulley  67 . From there, cable  53  winds onto drums  59 ,  61 , and then is routed forward to a second forward right-side pulley  69 . From there, cable  53  extends back across to a second forward left-side pulley  71  then rearward to left connector  51  on member  39 . 
   Cable  55  begins at right-side connector  51  on member  41 , then extends rearward and around rearward right-side pulleys  70 ,  73 . Cable  55  extends around second rearward right-side pulley  72  forward to first right-side pulley  67  and winds onto drums  59 ,  61 . Cable  55  then extends forward to second right-side pulley  69 , then rearward to right-side connector  51  on member  41 . A tension device is used to maintain tension in cables  53 ,  55 , for example, spring  75  shown connecting rearward pulleys  63 ,  73 . 
   As drum  59  is rotated by the motor, cables  53 ,  55  feed simultaneously onto drum  61  then into their respective cable loops. Rotation of drum  59  in one direction causes forward movement of blade assembly  27 , whereas rotation in the other direction causes rearward movement of blade assembly  27 . The friction of cables  53 ,  55  on drum  61  provides additional friction to that between cables  53 ,  55  on drum  59 , ensuring that cables  53 ,  55  do not slip. As indicated by the arrows, when blade  33  is moving forward, first forward pulleys  67 ,  71  rotate clockwise and second forward pulleys  65 .  67  rotate counterclockwise. Similarly, first rearward pulleys  60 ,  70  rotate counterclockwise while second rearward pulleys  62 ,  72  rotate clockwise. By providing cable system  57  with cables  53 ,  55  located laterally outward of blade  33 , slag falling onto collection surface  25  does not contaminate cable system  57 , allowing for less required maintenance and more reliable operation of table  11 . 
   The right-side portion of blade assembly  27  is shown positioned on track  31  in  FIG. 4 , the left-side portion being a mirror image of the right-side portion positioned on track  29 . As shown, the rear portion of member  49  is in the lower position with blade  33  is in the engaged position, the lower edge of blade  33  being in contact with collection surface  25 . This position is used when blade assembly  27  is moving forward for scraping slag accumulated on collection surface  25 . Pawl  50  is in the first position, which is a trailing orientation, allowing blade to rest on collection surface  25 . Surface  45  of each sliding block  43  slides on upper surface  76  of track  31 . Pawl  50  is in the scraping position of  FIG. 4  when blade assembly  27  is moving to the left, or forward for scraping. Pawl  50  is in the retraction position of  FIG. 5  when blade assembly  27  is moving to the right, or rearward after a scraping stroke. 
   Trip members or notches  77  are located at rearward inner locations on both tracks  29 ,  31  and are formed in surface  76 , notches  77  having an inclined forward ramp  79  and an inclined rear ramp  81 . Notches  77  rotate pawls  50  between the first and second positions as pawls  50  engage notches  77  during travel of blade assembly  27 . 
     FIG. 4 , shows blade assembly  27  after is has already moved rearward of notches  77  and has started moving forward during a scraping stroke. During the retraction stroke, pawl  50  would have been in the retracted position of  FIG. 5 . As pawl  50  moves rearward into notch  77  while retracted, notch  77  will not change the position of pawl  50 . Once rearward of notch  77 , a limit switch causes blade assembly  27  to move forward. As pawl  50  falls into notch  77  on the forward stroke, notch  77  will rotate pawl  50  back from the retracted position of  FIG. 5  to the scraping position of  FIG. 4 . Notches  77  thus serve as rearward tripping members to cause blade  33  to move from a retracted to a scraping position. 
     FIG. 6  is a left-side view showing the forward end of track  29  and blade assembly  27  at its forward most point. A forward portion of each track  29 ,  31  is inclined, and blade assembly  27  slides up the inclined portions during the forward stroke. Tracks  29 ,  31  have trip members or notches  87  on the inclined portions, notches  87  being formed to have the same shape and function as notches  77  ( FIG. 4 ), except they serve to move blade  33  from the scraping position to the retracted position. Collection surface  25  terminates on the inclined portions, creating hole  89  between tracks  29 ,  31 . As blade assembly  27  is moved forward toward the end of collection surface  25 , blade  33  continues in contact with collection surface  25 , pushing slag ahead of blade  33 . Blade  33  pushes slag until blade  33  reaches hole  89 , through which slag falls. A cart (not shown) or other container is preferably located below hole  89  for containing slag for removal from table  11 . 
   During the forward stroke, blade assembly  27  to a position wherein pawls  50  are forward of notches  87 , then a limit switch causes blade assembly  27  to start moving rearward. As blade assembly  27  moves rearward, pawls  50  engage notches  87 , rotating pawls  50  to the retracted position of  FIG. 5 . This lifts arms  47 ,  49  and blade  33  to the retracted position. Blade assembly  27  moves rearward in the return stroke until pawls  50  pass rear notches  77 , then pawls  50  engage notches  77  on the start of the forward stroke to return blade to the engaged position as assembly  27  is moved forward on the next forward stroke. 
   Referring to the figures in operation, a workpiece  20  is placed on table  11 , and torches  13  are positioned by gantry  15  for cutting workpiece  20 . Slag and other wastes are produced, which fall into the interior of table  11 . To cause the slag to collect near the center of table  11  on collection surface  25 , inclined plates  21 ,  23  funnel falling material towards surface  25  and inward of tracks  29 ,  31 . 
   Blade assembly  27  is operated by a cable system  57  for stroking assembly  27  forward and rearward, slider blocks  41 ,  43  on assembly  27  sliding on tracks  29 ,  31 . Blade assembly  27  is moved forward with blade  33  in an engaged position in contact with collection surface  25 , blade  33  scraping accumulated slag from surface  25  and pushing the slag forward ahead of blade  33 . At the forward end of the scraping stroke, blade assembly rides up inclined portions of tracks  29 ,  31 , and blade  33  pushes slag out of a hole  89  located at the end of collection surface  25 . Slag preferably falls into a removable container (not shown) for removal of slag from table  11 . 
   As blade assembly is moved rearward in a return stroke, pawls  50  engage notches  87 , rotating pawls and lifting arms  47 ,  49  and blade  33 . In this position, blade  33  is spaced from collection surface  25 , allowing blade to return the rear end of table  11  without scraping slag. Pawls  50  remain in this position through the return stroke. At the end of the return stroke, the direction of travel of blade assembly  27  is again reversed, and pawls  50  engage notches  77  for rotating the lower ends of pawls  50  to a trailing position, allowing arms  47 ,  49  and blade  33  to drop into the engaged position for scraping surface  25  during the forward stroke. 
   The present invention has several advantages. The blade assembly scrapes slag from a collection surface and pushes the slag forward for deposit in a removable container. The blade automatically retracts when moving rearward after a forward stroke, and automatically returns to the scraping position when again moving forward. Inclined plates funnel the slag towards the collection surface and within tracks for the blade assembly, preventing the slag from landing on the tracks. The cable system around the perimeter of the blade assembly path is used to move the blade assembly, preventing slag from contaminating the cable system. The cable system eliminates a need for a rack-and-pinion or similar drive system that is located in the dirty areas and the possible need for the blade assembly to carry a motor. 
   While the invention has been shown in only one of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes without departing from the scope of the invention.