Abstract:
A wet abrasive blast pot includes a cylindrical pressure vessel have a top section, a bottom section, and sidewalls extending between the top section and the bottom section. The bottom section includes an outlet, and the top section includes a fill inlet. The top section includes a convex head, with the fill inlet located at the uppermost portion of the pressure vessel.

Description:
BACKGROUND 
       [0001]    Wet abrasive blasting systems are typically used in situations requiring blasting operations that do not tolerate dry sandblasting conditions due to environmental or other factors. Wet abrasive blasting systems are used to control generation of dust and at the same time ensure that there is minimal damage to the substrate. Wet abrasive blasting systems force a slurry of abrasive media into a compressed airstream under controlled conditions. A blast pot or pressure vessel is charged with water and a solid abrasive to form a wet abrasive slurry. It is very important that the blast pot be purged of air prior to commencement of the blasting operation. The pressurized water forces the slurry out of the blast pot, into a piping system, and finally into a mixing point where the wet slurry is mixed with compressed air. Fluctuations in flow of pressure in either the slurry or pressurized gas will result in inconsistent behaviour of the wet abrasive blasting system and ultimately will lead to an uncontrollable or inefficient blasting process. It has been found that air entrapment in the blast pot or pressure vessel is a major contributing factor to instability of wet abrasive blasting systems. In systems to date, air relief valves have been employed in order to purge the blast pot or pressure vessel of all air prior to pressurizing with water. Unfortunately these air bleeding or purging systems often require two to three minutes of time to completely evacuate the blast pot or pressure vessel of air thereby reducing the efficiency of the wet abrasive blasting operation. 
         [0002]    It would be best and beneficial if one were able to utilize a blast pot pressure vessel design which eliminates the entrapment of air and therefore reduces or eliminates the need for bleeding of entrapped air in the pressure vessel prior to commencement of the blasting operation. 
       SUMMARY 
       [0003]    A wet abrasive blast pot includes a cylindrical pressure vessel having a top section, a bottom section, and sidewalls extending between the top section and the bottom section. The bottom section includes an outlet, and the top section includes a fill inlet. The top section includes a convex head, with the fill inlet located at the uppermost portion of the pressure vessel. 
         [0004]    Preferably, the top section further includes a concave dish top, wherein a lower most portion of the concave dish top is connected to the upper most portion of the convex head at the fill inlet. The top section also preferably includes connecting walls for connecting the sidewalls to the outer most portion of the concave dish top. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is a cross sectional schematic view of a prior art blast pot with a concave head configuration. 
           [0006]      FIG. 2  is a schematic cross-sectional view taken through the middle of a blast pot showing a convex head configuration. 
           [0007]      FIG. 3  is a schematic cross-sectional view taken through the middle of a blast pot showing a convex head configuration together with a concave dish extension. 
           [0008]      FIG. 4  is a schematic of a wet abrasive blasting system including the blast pot of  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION 
       [0009]      FIG. 1  is a prior art depiction of a typically currently used wet abrasive blast pot  100  which includes the following major components: pressure vessel  102  having side walls  104 , concave top section  106 , bottom section  108 , outlet  110 , and fill inlet  112 . 
         [0010]    Furthermore, pressure vessel  102  defines interior  114  and also includes pop up valve  116 , access port  118  for cleaning out the pressure vessel, air pressure release valve  120  (which allows trapped air  124  to be expelled as air  122 ), and water level  126 . Blast pot  100  further includes legs  130  which support pressure vessel  102  and dished top section  106  which includes concave head  128 . 
         [0011]    In use, prior art blast pot  100  is filled with abrasive and water through fill inlet  112  until interior  114  of pressure vessel  102  is filled as high as is possible, which normally would be close to water level  126  shown in  FIG. 1 . Top section  106  is made up of dished concave head  128 . Due to the geometric configuration of concave head  128 , air  122  is trapped as trapped air  124  in the space above water level  126  and below concave head  128  as shown in  FIG. 1 . 
         [0012]    Due to the location of fill inlet  112 , under gravity filling it is difficult to get the water and abrasive in pressure vessel  102  any higher than water level  126 . Once abrasive and water is filled to water level  126 , pop up valve  116  is closed, and then purging of trapped air  124  is commenced. 
         [0013]    At this point, blast pot  100  is pressurized with pressurized water. Air release valve  120  allows trapped air  124  to be released and expelled from interior  114  of pressure vessel  102  as air  122  until such time as water level  126  reaches fill level  132 , which is the upper most point defined where sidewall  104  meet the upper most portion of concave head  128 . 
         [0014]    Blast pot  100  uses an inverted or concave head  128  which functions not only as a top to pressure vessel  102 , but also acts as a funnel and/or dish hopper for directing the blasting abrasive material and water into fill inlet  112  of blast pot  100 . 
         [0015]    The disadvantage of the prior art design depicted in  FIG. 1  is that concave head  128  entraps trapped air  124  above fill inlet  112  of blast pot  100 . Therefore blast pot  100  must be fitted with air release valve  120  to allow trapped air  124  to escape as air  122 . This purging or bleeding of trapped air  124  can take upwards of two to three minutes and result in reduced productivity of the wet abrasive blasting system. 
         [0016]      FIG. 2  shows blast pot  200 , which includes the following major components: pressure vessel  202  which defines an interior  214  made up of side walls  204 , top section  250 , bottom section  108  (which includes an outlet  110  at the bottom section  108 ), and fill inlet  112  at top section  250 . Unlike prior art blast pot  100 , blast pot  200  includes a convex-shaped convex head  252 . 
         [0017]    In use, abrasive and water is filled into fill inlet  112 . Due to the configuration of convex head  252  as shown in  FIG. 2 , water and abrasive can be filled all the way up to fill level  232  (which is at least the bottom of fill inlet  112 ), thereby ensuring that there is little to no entrapped air within pressure vessel  202  once water and abrasive is filled all the way to the top to fill level  232 . 
         [0018]    A disadvantage of this design is that there is no funnel or dish hopper configuration at the top section  250  which would funnel water and abrasive into the pressure vessel  202 . This could result in a significant amount of spillage and waste of both the abrasive material and water. 
         [0019]      FIG. 3  shows blast pot  300 , which includes the following major components: namely, pressure vessel  302 , made of side wall  304 , bottom section  108  including outlet  110 , top section  370  (which includes convex head  252 , and connecting wall  362 ), and concave dish top  360 . Blast pot  300  also includes fill inlet  112 , pop up valve  116 , and access port  118 . 
         [0020]    In this embodiment, blast pot  300  includes all the advantages described above for blast pot  200  with the addition of a concave dish top which connects at fill inlet  112  with convex head  252  and is supported by connecting wall  362 . Blast pot  300  does not entrap any air due to the fact that at fill level  380  most if not all of the air has been purged from interior  214  of pressure vessel  302  through fill inlet  112 , which is at the uppermost point of pressure vessel  302 . Blast pot  300  however also includes the advantage of the prior art blast pot design  100  section since it includes a concave dish top  360  which acts as a funnel and/or a dish hopper for directing abrasive material and water into the fill inlet of pressure vessel  302 . 
         [0021]      FIG. 4  is a schematic diagram of an abrasive wet blasting system utilizing blast pot  300 , which includes the following additional components not shown in  FIG. 3 . Water pump  400  (which preferably is a pneumatic air over water piston pump) takes water supply  402  and pressurizes it and sends it under pressure to water inlet  404 , thereby pressurizing water abrasive mixture  406  within interior  214  of pressure vessel  302 . Water abrasive mixture  406  is a slurry which is forced out through outlet  110  and through transfer hose  410  up through ball valve  412  and through pinch hose  416 , which can be shut off with pinch valve  414  prior to water abrasive mixture  406  entering T connector  418  at mixing point  420 . 
         [0022]    Independently, air supply  422  delivers compressed air (typically from a high volume air compressor) through air valve  424 , and check valve  421  to mixing point  420 . At mixing point  420 , the compressed air mixes together with the water abrasive mixture  406  and is forced out through blast hose  426  and ultimately through blast nozzle  428 , thus forming an air water abrasive blast  430  out of blast nozzle  428 . 
         [0023]      FIG. 4  shows schematically how the newly conceived of blast pot  300  would be used together with a typical wet abrasive blasting system. 
         [0024]    It is also possible that blast pot  200  could be used in a similar configuration as shown in  FIG. 4 . 
         [0025]    It should be apparent to persons skilled in the arts that various modifications and adaptation of this structure described above are possible without departure from the spirit of the invention the scope of which defined in the appended claim.