Note: Descriptions are shown in the official language in which they were submitted.
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S P E C I F I C A T I O N
This invention relates to airless abrasive
blast wheels for projecting metallic and non-metallic
particulate media for impact upon surfaces in such
processes as shot peening, descaling, deburring, and
other abrasive blast applications.
Generally speaking, such blast wheels comprise
a simple wheel formed of two blades extending diamet-
rically in opposite directions from a central hub mounted
on a motor driven, belt driven, or the like shaft for
rotational movement about a central axis of the shaft.
A centrifugal two-bladed airless blast wheel of the type
described is marketed in this country under the name
Delta type wheel. Certain aspects of the invention,
also have application to other types of single or
multiple bladed wheels, wherein the particulate media
is introduced for engagement with the inner portion of
the blade surface for projecting from the ends thereof
in response to centrifugal force imparted by rotation
of the blades at high speed about the central axis.
Delta type wheels of the type heretofore
produced have been found to be deficient in a number of
respects. Blade change to replace worn out blades has
been awkward and sometimes very difficult, and the
mounted blades are inadequately supported on the central
shaft. Further, the assembly is subject to vibrations,
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which bring about increased wear and reduction in
strength of the assembly.
The feed from the tubes used to introduce
the particulate media into the path of the blades pro-
vides for an erratic flow rate which not only reduces
the output efficiency of the wheel but results in lack
of control of the blast pattern.
One important feature of this invention resides
in the configuration of the feed tube through which the
particulate media is fed to the wheel. In the past, use
has been made of a tubular member of uniform cross section
extending from the end of a hopper to a level which just
clears the upper edge of the blades.
Because of the increasing velocity of the
particulate media as it falls gravitationally downwardly
through the feed tube, particulate media which fills the
tube at the inlet only partially fills the tube at the
outlet. It has been found that when the discharge end
of the tube is only partially filled, erratic patterns
result from the wandering action of the particulate media
out of the feed tube.
The following tabulation gives the velocity and
the density determinations made with the same particulate
media for various lengths of fall through a feed tube
having a 1.5 inch orifice and from an initial velocity of
92 ft./min. and a K factor for the friction of the tube
walls of 0.5.
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Distance of Fall Velocity out of Exit Density out
Dischar~e F.nd of Tube of Tube
3" 193.5 ft/min 47.5%
6" 257.7 ft/min 35.7~
9" 308.9 ft/min 29.8%
12" 352.9 ft/min 26.1%
24" 490.2 ft/min 18.8%
The erractic action has been overcome, in accord-
ance with one aspect of this invention, by the use of a feed
tube having a prescribed configuration in order to provide
for a smooth feed of particulate media at a uniform rate
which calculates out to be a maximum rate with corre-
sponding movement in the pattern of the blast.
More specifically, the present invention pro-
vides a device for airless blast with particulate material
comprising a wheel having wheel blades which extend
radially outwardly from an axial portion of the wheel,
means for driving the wheel in rotational movement at
high speed, and means for feeding particulate material to
the inner end portions of the wheel blades for engagement
by the blades during rotational movement of the wheel
whereby said engaged particulate material is displaced
outwardly over the surfaces of the blades for pro~ection
at high velocity from the outer ends of the blades, in
which the means for feeding particulate material to the
blades comprises a vertically disposed tubular member
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having an upper inlet in communication with a discharge
opening aligned with the inner end portions of the blades
and which embodies at least one of the features of a
discharge opening which is at the apex of a section of
decreasing cross section and/or a discharge opening
having a dimension in the direction of rotation of the
wheel which is greater than the crosswise dimension
whereby the time of flow of particulate material onto
the blades is increased thereby to increase the length
of the pattern of particulate material thrown from the
outer ends of the blades.
By forming the feed tube with a configuration
which diminishes in cross section from the inlet end to
the discharge end, the density of the particulate media
at the discharge end is at substantially maximum density
which assures a smooth feed at a uniform rate.
Similarly, it has also been found that the
pattern thrown by the blades can be markedly lengthened
to provide for greater coverage and more efficient
operation by configuration of the discharge from the
feed tube to lengthen the discharge of particulate media
somewhat in the direction of rotation of the blades.
This has the effect of increasing the time of flow of
particulate media onto the face of the blade with a
resultant longer particulate blast pattern. In other
words, the same inner area of the blade is adapted to
engage successive amounts of particulate media during
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its rotational movement thereby to increase the length
of the blade covered by particulate media during any one
instant, with corresponding increase in the angle for
projection of the particulate media from the blade.
Other features and advantages of this invention
will hereinafter be described with reference to a number
of preferred embodiments of the invention as shown in the
accompanying drawings, in which:
Figure 1 is a side elevational view of a wheel
assembly embodying the features of the invention, with
portions broken away to show elements in the interior
thereof;
Figure 2 is a sectional view taken along line
2-2 of Figure l;
Figure 3 is a top plan view of the two-bladed
wheel shown in Figure l;
- Figure 4 is a side elevational view of the
two-bladed wheel of Figure 3;
Figure 5 is a sectional view taken along the
line 5-5 of Figure 4;
Figure 6 is a sectional view taken along the
line 6-6 of Figure 4;
Figure 7 is a sectional view taken along the
line 7-7 of Figure 4;
Figure 8 is a perspective view of a feed tube
embodying the features of this invention;
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Figure 9 is a perspective view of a modifica-
tion in a feed tube embodying the features of this in-
vention;
Figure 10 is a perspecti.ve view of a further
modification in a feed tube embodying the features of
this invention;
Figure 11 is a front elevational view showing
the wheel and feed mounted for rotational movement about
a horizontally disposed axis; and
Figure 12 is a schematic side elevational view
showing the relation between the wheel blades and the
feed opening in a wheel of the type shown in Figure 11.
Referring now to Figures 3 to 7 of the drawings,.
illustration is made of the two-bladed wheel comprising
a central hub 10 and a pair of blades 12 and 14 extending
outwardly in parallel relation in opposite directions
from the hub 10, from portions of the hub on opposite
sides of the axis and spaced from the axis by an equal
amount to provide a balanced wheel.
The two-bladed wheel is mounted for movement
about an axis by means of a bushing 16 which is received
in fitting relation within an axial bore 18 through a
portion of the hub and which, in turn, is mounted on the
end of a motor driven shaft 20 which extends through an
axial opening 22 in the hub in contiguous relation with
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the bore 18. The bushing is provided with a key 24
adapted to be received in fitting relationship within
a keyway 26 in the hub for replaceably mounting the
two-bladed wheel on the bushing for rotational movement
therewith.
The surfaces 28 of the blades 12 and 14, facing
in the direction of rotational movement, indicated by
the arrow in Figure 2, constitute the front face adapted
to engage the particulate media and over which the
particulate media is displaced outwardly for projection
from the ends of the blades in response to rotational
movement of the wheel at high speed.
The front face 28 of each blade 12 and 1~ is
formed with a rib 30 which projects from the front face
along the lower edge substantially throughout the length
thereof. A similar rib 32 of lesser depth extends from
the upper edge of the front face substantially throughout
the length thereof except for a short inner section adja-
cent the hub 10 in circumferential alignment with the out-
let from the feed tube through which particulate mediaflow into the path of the inner end portion of the blades
for engagement thereby during rotational movement of the
wheel.
Preferably, the two-bladed wheel is formed in
one piece to enable easier assembly while providing a
stronger wheel which remains well balanced during use and
thereby to provide for greater stability and less vibration
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during operation.
The blades 12 and 14 are usually straight
mem~ers of rectangular shape having a width within the
range of 1.5-4 inches and a length within the range of
3-10 inches. The ribs or flanges 30 and 32 operate to
confine the particulate media for travel along the face
of the blade and to minimize stray of particulate media
ovèr the edges of the blades.
As illustrated in Figures 1 and 2, the two-
bladed wheel is mounted within a shroud 40 having anopen side 42 through which particulate media is projected
by the wheel. In the illustrated modification, the
shroud is of trapezoidal shape with a back wall 44,
angularly extending side walls 46 and 48 and trapezoidally
shaped bottom and top walls 50.
A bracket 54 mounts an electric motor 56 from
the bottom wall 50 of the shroud with the shaft 58 of
the motor extending through the bottom wall for receipt
of the busing 16 on the through extending portion thereof
and which is adapted to be secured thereon, as by means
of a cap screw 60. A rubber seal 62 is provided between
the motor housing and the bottom wall 50 of the shroud
and a sealing gasket 64 is provided about the shaft
portion extending through the bottom wall for protection
from the abrasive media.
111981~
~ s illustrated in Figures 1, 2 and 8, one
preferred configuration for the particulate feed means
comprises a feed tube 66 which tapers inwardly from the
entrance end 68 to the discharge end 70 with the dis-
charge end defining an orifice to crescent shape arranged
to extend circumferentially to the axis of rotation of
the wheel or to extend lengthwise in the direction of
rotation of the blade.
The desired effect could also be obtained with
a feed tube of the type shown in Figure 9, in which the
feed tube tapers inwardly from the inlet end 72 to the
discharge end 74 with the outlet opening at the discharge
end being of oblong or other geometric shape with the
major dimension extending in the direction circumferential-
ly of the axis or in the direction of rotation of the
blade.
As of a further modification, the feed tube can
be formed of two or more separate tubular members 76 and
78 of circular or polygonal cross section, each of which
tapers inwardly from their inlet end 80 to the discharge
82 with the tubular members arranged circumferentially
with respect to the axis of the wheel to discharge
particulate media at variable distances from the blade
for continuous engagement by the blade over a period
of time during its rotational movement.
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All of these arrangements have the effect of
making increased use of the blade thereby to increase the
output of the wheel, while, at the same time, increasing
the area covered by the abrasive blast.
As shown in Figures 1 and 2, the feed tube 66
extends through an opening in the top plate of the shroud
to a level immediately above the upper inner edge of the
blade. The feed tube 66 is supported by a plate 84 that
is fastened to the top surface of the top plate, as by
means of lock washers 86 held down by cap screws 88.
Particulate media is fed to the inlet of the feed tube
66 from a hopper (not shown) in communication therewith
for gravity flow of particulate media from the hopper
into the feed tube.
In operation, the wheel is rotated at high speed.
The article to be treated by particulate media thrown from
the wheel is positioned in front of the open side 42 of the
shroud. Particulate media which falls from the discharge
end of the tube 66 is engaged by the face of the blades
rotating at high speed. Upon engagement with the face of
the rotating blades, the particulate media is centrifugally
displaced over the face of the blade and is thrown with
high centrifugal force from the ends thereof, through the
open side 42 onto the article in front thereof.
It will be understood that the wheel shaft can
be driven in rotational movement by convention means other
than an electrical motor, for example, as by an internal
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combustion engine, magnetic drive, or by indirect belt or
gear drive. Similarly, the shroud can vary in shape as
long as it substantially encloses the wheel except for
the open side wall for projection of the particulate media
therethrough. The wheel can be mounted for rotational
movement about a vertical axis or a horizontal axis or any
angle in between.
The wheel assembly described constitutes a low
cost airless blast device which is easy to operate and
which utilizes minimum space and supporting equipment. The
spent abrasive or other particulate media can be recovered
in the usual manner for reuse, preferably after removing
dust and dirt as by means of a screen, air wash, and/or
magnetic separator.
When it is desired to remove the wheel for re-
placement or repair, it is only necessary to remove the
wheel from the shaft, with or without the bushing, and to
replace the wheel by reversal of the operation.
The described features are not restricted to a
vertical feed to wheel blades mounted for rotational move-
ment in a horizontal plane. It has been found that similar
results can be obtained with a wheel mounted to rotate
about a substantially horizontally disposed axis or along
any angle between vertical and horizontal. It is re~uired,
however, to divert the vertical flow of particulate material
from downward flow through the tubular member and through a
hollow member which extends crosswise and which includes
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the concept o~ decreasing cross sections to a discharge
opening of the type described which faces laterally in
the direction towards the adjacent outer edge of the blades
to feed the particulate material onto the blades in
circular alignment with the inner end portions of the
blades.
Figures 11 and 12 illustrate a two-bladed wheel
of the latter type mounted for rotational movement of the
wheel about a horizontal axis for rotation of the blades
in a vertical plane. As shown in these Figures 11 and 12,
the blades 14, extend radially outwardly from the hub 10,
are mounted on shaft 20 for rotational movement by the
electrical driving motor 56 about their horizontal axis.
It will be understood that the angle of the wheel can be
varied for rotation about a vertical or horizontal axis
or any angle therebetween.
In the modification shown in Figures 11 and 12,
the particulate material is fed into the funnel 100 which
directs the particulate material into the open u~per end
104 of a feed tube 102, in the form of a tubular member
having a circular opening 106 in the inner side wall in
crosswise alignment and in full communication with an
outer open end 108 of a conically shaped hollow body 110
having a discharge opening 112 at its inner apex end in
facing relation with the blades 14. At least the position
of the hollow body 110 leading into the discharge opening
is of the diminishing cross section, as heretofore described
1119812
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for maintaining uniform flow and control of the particulate
material fed onto the blades 14.
The discharge opening 112 is of a configuration
of the type heretofore described to prolong the feed of
particulate material onto the inner end portions of the
blades 14. Thus, the blades 14 engage successive portions
of the particulate material issuing from the feed opening
112 during rotational movement of the blades 14 thereby to
enlarge the pattern of particulate material projected
from the ends of the blades. The various shapes of the
feed openings elongated in the direction of rotational
movement of the blades are illustrated in Figures 8, 9
and 10.
The conically shaped hollow body 110 is preferably
mounted on the tubular member for rotational movement
relative thereto about an axis substantially in endwise
alignment with the axis of the wheel with the outlet
opening 112 offset for crosswise alignment with the inner
end portions of the blades 14 to feed the particulate
material onto the inner end portions of the blades 14.
By way of construction, the conically shaped hollow body
110 can be adjusted for rotational movement about its axis
to locate the feed opening 112 in any desired circumferen-
tial relation relative to the wheel thereby to enable sub-
stantially precise control over the direction of the par-
ticulate material thrown from the ends of the blades 1~.
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For example, when the conically shaped hollow body is
rotated to position the feed opening 112 at the location
shown in Figure 12, the particulate material will be
thrown in a spread pattern in a lateral direction. By
rotation of the hollow body 110 to locate the feed opening
112 above the axis of the wheel, the pattern of particulate
material thrown from the ends of the blades 14 will be in
a do~nward direction. Similarly, the hollow body 110 can
be rotated to vary the direction which will normally be
in a direction about diametrically opposite the radial
direction of offset of the feed opening 112 from the axis
of the wheel.
For rotational adjustment, the outlet opening
106 of the tubular member 102 and the inlet opening 108
of the hollow body 110 are formed of circular cross section
with an annular flange 114 about the inlet in telescoping
relation with an annular shroud 116 about the outlet
opening 106 to support the hollow body 110 on the tubular
member 102. The telescoping portions can be provided with
openings (not shown) through which locking pins (not shown)
can be inserted when aligned to interlock the members in
their assembled and adjusted relation. Alternatively, the
elements may be secured in the assembled relation by
suitable clamps or other locking means.
