Note: Descriptions are shown in the official language in which they were submitted.
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WET ABRASIVE BLAST POT
BACKGROUND
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.
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
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.
Preferably, the top section further includes a concave dish top, wherein a
lower most
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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
Figure 1 is a cross sectional schematic view of a prior art blast pot with a
concave
head configuration.
Figure 2 is a schematic cross-sectional view taken through the middle of a
blast pot
showing a convex head configuration.
Figure 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.
Figure 4 is a schematic of a wet abrasive blasting system including the blast
pot of
Figure 3.
DETAILED DESCRIPTION
Figure 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.
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.
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 Figure 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 Figure
1.
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
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commenced.
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.
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.
The disadvantage of the prior art design depicted in Figure 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.
Figure 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.
In use, abrasive and water is filled into fill inlet 112. Due to the
configuration of
convex head 252 as shown in Figure 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.
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.
Figure 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.
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Blast pot 300 also includes fill inlet 112, pop up valve 116, and access port
118.
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.
Figure 4 is a schematic diagram of an abrasive wet blasting system utilizing
blast
pot 300, which includes the following additional components not shown in
Figure 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.
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.
Figure 4 shows schematically how the newly conceived of blast pot 300 would be
used together with a typical wet abrasive blasting system.
It is also possible that blast pot 200 could be used in a similar
configuration as
shown in Figure 4.
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.
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