Patent Publication Number: US-2007096539-A1

Title: Apparatus and method for cutting asphalt, concrete and other materials

Description:
This is a nonprovisional application claiming priority to provisional patent application No. ______, filed Oct. 28, 2005 by Douglas H. Walker et al. entitled Apparatus and Method for Cutting Road Surfaces. 
    
    
     FIELD OF THE INVENTION  
      The invention relates to an apparatus and method for dry cutting asphalt, concrete, masonry and other hard construction materials in all forms, wherein the dust generated during cutting is more effectively collected.  
     BACKGROUND OF THE INVENTION  
      During construction, maintenance, improvement, or renovation, it is often necessary to cut hard materials such as asphalt, concrete, mortar, ceramic, masonry, composite, and other construction materials. At many worksites, the slurry generated during wet cutting or the dust generated during dry cutting at many worksites must be collected and properly discarded. Road surfaces are one type of worksite at which dust cleaning and collection is required and, in fact, regulated by departments of transportation.  
      When concrete road surfaces are paved over with asphalt, the asphalt often cracks when the underlying concrete slabs heave and shift relative to one another. To prevent cracking, the asphalt is cut directly above and along each joint in the concrete. The cut is then filled with a flexible filler such as hot rubberized asphalt, silicon, or neoprene. The filler allows the underlying concrete slabs to heave without cracking the asphalt.  
      The asphalt is often cut with a powerful, four wheeled, walk-behind saw known as a flat saw. In the prior art, flat saw cutting of asphalt is performed wet by continuously injecting water into the blade guard. The slurry generated during cutting is ejected from the rear of the blade cover. When the slurry dries, a layer of road dust remains on the road surface, which is not only visually unappealing but is also a safety hazard. For example, when motor vehicles drive over the dust, it becomes airborne and obstructs visibility. To prevent accidents, the slurry must be cleaned from the road surface by a cleaning apparatus and/or work crew, which adds to the time and expense of the job.  
      To insure good adhesion to the asphalt, the groove must be cleaned prior to filling with the flexible filler. It is known in the prior art to trail the flat saw with a vacuum collection device. However, because of the depth of the groove and the properties of the slurry, known prior art vacuum cleaning devices do not adequately clean the groove. Alternatively, the groove may be cleaned with pressurized air or water, which doesn&#39;t collect the road dust. Therefore, a cleaning apparatus and/or work crew trailing the cutting crew is required in order to clean the groove and the road surface.  
     SUMMARY OF THE INVENTION  
      The invention comprises an apparatus for dry cutting asphalt and concrete in all forms including, for example, road surfaces, slabs, walkways, parking lots and decks, foundations, waterways, etc. The apparatus also cuts masonry, ceramic and other hard construction materials such as, for example, brick, mortar, stone, composite paver, tile, etc. The apparatus collects the dust created during cutting, and cleans the groove and area adjacent the groove.  
      The apparatus has a forward direction of operation and generally comprises a circular saw, a blade guard, and a vacuum collection means connected to the blade guard. The circular saw has a housing with front and back ends, and means for conveying the housing over the surface of the material. A rotatable shaft extends from the side of the housing and has a blade fixed thereto. The blade has an upper portion and a lower portion. A motor and transmission rotate the shaft and blade in a direction that upcuts the material when the saw is conveyed in the forward direction.  
      The blade guard is mounted to the housing and generally comprises a cover and a shoe. The cover portion surrounds the upper portion of the blade. The shoe surrounds the lower portion of the blade. The cover and shoe are connected by an adjustable connection interface. Vacuum collection means is connected to the blade guard. The height of the blade can be adjusted for different cut-depths.  
      The blade guard adjusts and surrounds the entire portion of the blade above the material surface at each cut-depth setting. In a preferred embodiment, the adjustable connection interface comprises a receptacle portion in the shoe and the cover telescopes within the receptacle portion.  
      In a preferred embodiment, the blade guard includes front and back ends, an air intake port in the back end, and a discharge port in the front end connected to the vacuum collection means. The discharge port has an internal opening proximate the projection point between the blade and the material surface. The internal opening is aligned directly in the trajectory of the dust from the projection point so that dust is projected directly into the exhaust port without contacting the interior of the blade guard. The exhaust port extends upwardly at an inclined angle relative to the trajectory of the dust from the projection point so that the dust impinges on the exhaust port at an angle less than 90 degrees.  
      The intake port has an internal opening aligned in the plane of the blade and above the groove, and located proximate the trailing contact point between the blade and the material surface. The air intake port may also have an air flow regulator.  
      The blade guard, the rotating blade, and the vacuum collection means create an air flow pattern flowing through the intake port, into the groove behind the trailing contact point of the blade and the groove, around the blade, and out the discharge port. The air flow pattern collects the dust, cleans the groove and adjacent surface, and cools the blade.  
      The apparatus has primary and secondary means for collecting the dust. With the primary means, dust is projected directly into the discharge port without contacting the interior of the blade guard and before the dust contacts the material surface. The air flow pattern helps direct the projected dust directly into the discharge port. With the secondary means, the air flow pattern dislodges dust from the trailing groove and directs it into the discharge port. The blade cover encloses the entire portion of the blade above the surface to contain the dust within an enclosed area.  
      The invention also provides a method dry cutting asphalt, concrete, ceramic, masonry, and other hard construction materials in all forms including, for example, road surfaces, slabs, walkways, parking lots and decks, foundations, waterways, etc. The apparatus collects the dust created during cutting, and cleans the groove and area adjacent the groove. In the novel method, the material is upcut with a circular saw. The portion of the blade above the material surface is enclosed to contain the dust within an enclosed area. The dust projected from the projection point between the blade and surface is collected before it contacts the surface. The trailing groove and adjacent surface are cleaned of any residual dust by directing a flow of air onto the groove and adjacent surface and vacuum collecting the residual dust.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a schematic view of a cutting device in accordance with an embodiment of the invention;  
       FIG. 2  is a side elevation of the blade guard of the cutting device in accordance with an embodiment of the invention;  
       FIG. 3  is a side elevation of the upper cover portion of the blade guard shown in  FIG. 2  after the bottom shoe has been removed;  
       FIG. 4  is a top plan view of the blade guard of  FIG. 2  after the bottom shoe has been removed and shown attached to the housing of the cutting device;  
       FIG. 5  is a side elevation of the upper cover portion of the blade guard of  FIG. 3  after the outer plate has been removed;  
       FIG. 6  is a side elevation of the upper cover portion of the blade guard of  FIG. 5  after the blade and blade flanges have been removed;  
       FIG. 7  is an opposite side elevation of the upper cover portion of the blade guard of  FIG. 3 ;  
       FIGS. 8   a  and  8   b  are side elevations of the blade guard of  FIG. 2  adjusted to cut grooves at two different depths;  
       FIG. 9  is a perspective view of the bottom shoe of the blade guard of  FIG. 2 ; and,  
       FIG. 10  is a schematic view of the blade guard and method of cutting in accordance with an embodiment of the invention.  
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
      For the purpose of illustrating the invention, there is shown in the accompanying drawings a preferred embodiment of the invention wherein like reference numerals are used throughout to designate like elements. However, it should be understood by those of ordinary skill in the art that the invention is not limited to the precise arrangements and instrumentalities shown therein and described below.  
      The term “upcutting” shall mean the method of cutting wherein a saw having a circulating blade is moved across the surface of a material in a forward direction F 1  and the blade  18  of the saw is rotated in a direction R 1  that causes the teeth to cut upwardly from below the surface and causes the blade  18  to resist movement of the saw in the forward direction F 1 . The term “dust” shall mean the debris and dust created by cutting or scoring a material such as asphalt or concrete. The term “projection point” shall mean the point of contact P 1  between the blade  18  and the surface  8  from which dust is projected outwardly from the blade  18  and upwardly from the road surface. The term “trailing contact point” shall mean the most rearward point of contact P 2  between the blade  18  and the material in the bottom of the groove. The definitions are schematically illustrated in  FIG. 10  with reference to cutting a groove  6  in a road surface  8 .  
      The invention is illustrated and described below with reference to cutting an asphalt or concrete road surface  8 . However, the invention may be used to cut and clean any form of asphalt or concrete material including, for example, slabs, walkways, parking lots and decks, foundations, waterways, roofs, etc. The invention may also be used to cut masonry, ceramic, and other hard construction materials including, for example, brick, mortar, stone, composite paver, etc.  
      An embodiment of the cutting device, designated generally by reference numeral  10 , is schematically illustrated in  FIG. 1 . The device  10  is constructed to operate in the forward direction F 1 . The device  10  cuts grooves  6  of varying widths and depths in asphalt or concrete road surfaces  8  and simultaneously collects nearly all of the road dust generated during cutting.  
      The road surface cutting device  10  has a housing  12  with a front end  12   a,  back end  12   b,  and sides  12   c.  A shaft  14 , best seen in  FIG. 4 , extends from one side  12   c  of the housing  12 . One or more masonry blades  18  are mounted on the shaft  14 . In a preferred embodiment, multiple blades  18  are stacked on the shaft  14  with the teeth locked in staggered radial locations relative to one another. The number of blades  18  selected by the operator will depend on the desired groove width.  
      A motor and transmission  20  drive the shaft  14 . As shown by the direction arrows in  FIGS. 1 and 10 , the motor and transmission  20  rotate the shaft  14  in a direction R 1  that creates upcutting by the blades  18  when the device  10  is conveyed in the forward direction of operation F 1 . The motor may be gas, electric, diesel or hydraulic.  
      The housing  12  is supported and conveyed over the road surface  8  by a front pair  16   a  and back pair  16   b  of wheels, which are mounted on shafts  22   a,    22   b,  respectively. In the preferred embodiment, the back pair of wheels  16   b  is driven by the motor to assist conveyance of the device  10  across the road surface  8 .  
      In a preferred embodiment, the shaft  22   a  of the front wheels  16   a  extends from and retracts toward the housing  12  to raise or lower the front end  12   a  of the housing  12  relative to the road surface  8 . By raising or lowering the front end  12   a  of the housing  12 , the blade  18  is also raised or lowered relative to the road surface  8 , thereby adjusting the groove depth without changing the diameter of the blade  18 .  
      A blade guard  24  is removably attached to the housing  12 . As best seen in  FIGS. 8   a  and  8   b,  the blade guard  24  surrounds the shaft  14  and the upper portion of the blades  18  above the road surface  8  at a range of groove depths. The blade guard  24  has a front end  24   a  and a back end  24   b,  which are arranged in the same orientation as the front end  12   a  and back end  12   b,  respectively, of the housing  12 . The blade guard  24  has an air intake port  26  at the back end  24   b  and a discharge port  28  at the front end  24   a.    
      Referring to  FIG. 2 , the blade guard  24  generally has a two-piece construction comprising an upper cover  30  and a lower shoe  32 . In a preferred embodiment, the cover  30  and shoe  32  have an adjustable, telescoping connection as best seen in  FIGS. 8   a  and  8   b.    
      Referring to  FIG. 4 , the cover  30  comprises an outer plate  34  and an inner plate  36 , which form an internal cavity  38  within which the blades  18  rotate. The inner plate is arranged in between the housing  12  and the outer plate  34 . The cover  30  surrounds the upper portion of the blade, which may include a substantial portion of the lower half of the blade  18 . The shoe  32  surrounds the lower portion of the blade  18 , which may include a portion of the upper half of the blade  18 . The dimensions of the cover  30  and shoe  32  may vary so long as a range of overlap is provided.  
      Referring to  FIGS. 3 and 4 , the outer plate  34  is generally flat except for a protruding central hub portion  34   a.  Referring to  FIG. 3 , the outer plate  34  has straight side edges  34   b  and a straight bottom edge  34   c.  The top edge  34   d  has an arcuate shape. A plurality of fastener holes  35  are arranged around the periphery of the outer plate  34 . Fasteners  46  extend through the holes  35  and connect the outer plate  34  to the inner plate  36 .  
      Referring to  FIGS. 4 and 5 , the inner plate  36  has a pan-shaped cross-section. The central portion  36   a  is generally flat and includes a central aperture (not shown) through which the saw shaft  14  extends into the internal cavity  38 . Referring to  FIG. 7 , the side edges  36   b  and bottom edge  36   c  of the inner plate  36  are straight. The top edge  36   d  is arcuate.  
      Sidewalls  40  are fixed to the side edges  36   b  and top edge  36   d  as best seen in  FIG. 4 . The sidewalls  40  extend transversely to the plane of the central portion  36   a.  The sidewalls  40  define the depth of the internal cavity  38  and are preferably deep enough to accommodate a sufficient number of blades  18  to cut a groove about 2 in. wide.  
      A flange  42  is fixed to the arcuate upper sidewall  40 . The flange  42  includes a plurality of holes  44  arranged around the periphery. Fasteners  46  extend through the holes and releasably connect the inner  36  and outer  34  plates. The inner plate  36  also includes threaded bores  48  proximate each bottom corner, which receive removable threaded fasteners  46  to connect the inner  36  and outer  34  plates.  
      Referring to  FIGS. 4, 6  and  7 , a mounting ear  50  is fixed to the upper portion of the exterior side of the inner plate  36 . As best seen in  FIG. 4 , the ear  50  comprises a C-shaped channel segment having a web portion  50   a  and a flange portion  50   b.  To connect the ear  50  to the housing, a bolt  52  extends through a bracket  54  on the housing  12  and through the web portion  50   a.  The flange portion  50   b  is wide enough so that a nut  56  can be fit into the channel and easily tighten onto the bolt  52 .  
      Referring to  FIGS. 7, 8   a,  and  8   b,  a pair of shoe-hang brackets  58  are fixed to the upper portion of the exterior side of the inner plate  36 . The shoe-hang brackets  58  extend lengthwise past the front  24   a  and back  24   b  ends of the blade guard  24 . The free ends of the shoe-hang brackets  58  are connected to chains  60  from which the lower shoe  32  suspends when the blade guard  24  is not resting on the road surface  8 . The shoe  32  can be removed by disconnecting the chains  60 .  
      A flange bearing  62  is mounted by fasteners  63  to the central portion of the exterior side of the inner plate  36 . The flange bearing  62  supports the blade guard  24  on the shaft  14  and provides an airtight seal between the shaft  14  and the inner plate  36 . The seal improves the effectiveness of the vacuum collection means  88  and the air flow pattern described below.  
      The blades  18  are fixed to the blade shaft  14  by bolt  64  which tightens into an axial, threaded bore  66  in the shaft  14 . The bolt tightens inner  68  and outer  69  blade flanges on opposed sides of the blade  18 . Referring to  FIG. 6 , the inner blade flange  68  is keyed to the shaft  14 .  
      Referring to  FIG. 9 , the shoe  32  has a rectangular-shaped receptacle portion  70  comprising parallel sidewalls  72 ,  74  and end walls  76 ,  78 . The interior length and width of the receptacle  70  are slightly larger than the exterior length and width of the lower portion of the cover  30  so that the cover telescopes snugly into and forms a generally-airtight interface with the receptacle portion  70  of the shoe  32 .  
      The bottom of the receptacle is formed by an abrasion-resistant skid plate  80 , which includes a slit  82  through which the blades  18  extend. The slit  82  is slightly wider than the width of the maximum number of stacked blades  18 . Except for the slit  82 , the skid plate  80  seals the bottom of receptacle portion  70  of the shoe  32 . Further, since the skid plate  80  lays flat on the road surface, the shoe  32  also surrounds and encloses the area surrounding the blade and cutting area, thereby containing the road dust within the blade guard  24 . The enclosure formed by the shoe also improves the effectiveness of the vacuum collection means  88  and the air flow pattern described below.  
      Each end wall  76 ,  78  has a bracket  81  fixed to the exterior surface. The brackets  81  releasably connect to the chains  60  to prevent the shoe  32  from dropping off the cover when the shoe  32  is not resting on the road surface  8 .  
      The air intake port  26  is formed in the back end wall  76  of the shoe  32 . The air intake port  26  includes an adjustable valve  84 , which regulates the amount of air drawn into the shoe  32 .  
      The discharge port  28  is formed in the front end wall  78  of the shoe  32 . The external end of the discharge port  28  is connected to a vacuum hose  28 , which is connected to the vacuum collection means  88 , which may be integrated with the housing or, as schematically illustrated in  FIG. 1 , remote from the cutting device  10 . Referring to  FIG. 10 , an air flow pattern, shown by the single arrows, is created by the construction of the blade cover, the rotation of the blade and the vacuum of the collection means  88 .  
      The internal opening of the intake port  26  is located in the plane of the blade  18  and groove  6 , and proximate the trailing contact point P 2 . This location helps direct the air flow pattern down into the groove to dislodge and project any residual road dust into the discharge port  28 .  
      The internal opening of the discharge port  28  is aligned to maximize the amount of road dust that is projected from the blade  18  directly into the discharge port  28 . Depending on the depth of the groove, the angle at which road dust is projected from the blade, tangent to the projection point P 1 , will vary slightly as shown by the triple cluster of arrows in  FIG. 10 . Therefore, the internal opening of the discharge port  28  should be large enough to account for varying angles of projection.  
      In order to reduce friction, the discharge port  28  is inclined at an angle Θ from vertical to reduce the angle of impact of the road dust on the internal walls of the discharge port  28 , preferably less than 90 degrees. For example, in the embodiment shown in  FIG. 10 , the discharge port  28  may be inclined at an angle Θ of about 25° from vertical.  
      In accordance with the method of the present invention, the road surface  8  is cut using a saw that traverses the road surface  8  in a forward direction F 1  while simultaneously upcutting the road surface. During cutting, the area surrounding the blade  18  is enclosed to contain the road dust. The road dust within the containment area is then collected by primary and secondary methods.  
      In the primary method, the vast majority of road dust is collected proximate the projection point by locating a discharge port proximate the projection point and directly in the road dust trajectory. A vacuum is also applied the discharge port.  
      In the secondary method, any residual road dust that escapes the primary collection means and collects in the trailing groove  6  or on the adjacent road surface  8  is blown from the groove  6  by an air stream, and then withdrawn through discharge port  28 . The air stream is created by locating an air intake port in the plane of the blade  18  and groove  6  proximate the trailing contact point P 2 . The rotation of the blade R 1  and the vacuum applied to the discharge port  28  combine to create a strong, steady flow of air through the intake port  26 , through the groove  6 , around the blade  18 , and out the discharge port  28 , as schematically illustrated in  FIG. 10 . The steady flow of air has the added benefit of cooling the blade  18  during cutting.  
      By upcutting the road surface, road dust is projected upwardly out of the groove where it can more be more easily collected by the vacuum collection means. In contrast, if the blade were rotated in an opposite direction, i.e., “down cutting”, the road dust would be projected from the trailing contact point P 2  into the trailing groove where it is far more difficult to remove and collect.  
      In one embodiment of the invention, the saw comprises a 72 hp. commercial diesel flat saw with an hydraulic system that raises and lowers the front end of the saw and hydraulics that propel the saw. The transmission is modified to rotate the blade in an upcutting direction. Operating the engine at 2,800 r.p.m. and the blade at 2,500 r.p.m. provides good results. The blade guard is connected to a HEPA type vacuum collection system which draws a vacuum of about 14 in. of lift. The diameter of the vacuum hose  86  reduces from 4 in. at the vacuum collection system  88  to 2 in. at the discharge port  28  of the blade guard  24 .  
      While the principles of the invention have been described above in connection with specific embodiments, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of the invention. For example, the blade guard  24  may be provided on a saw that is already constructed to upcut asphalt. The blade guard  24  is then mounted to the saw and used in accordance with the method described above.