U.S. patent number 3,916,568 [Application Number 05/518,579] was granted by the patent office on 1975-11-04 for sandblast machine.
This patent grant is currently assigned to Enviro-Blast International. Invention is credited to Edward L. Horton, James J. Rose.
United States Patent |
3,916,568 |
Rose , et al. |
November 4, 1975 |
Sandblast machine
Abstract
To sandblast a floor surface, a hood is mounted on wheels to
move over the floor with the open side of the hood facing downward
to form a traveling chamber. A sandblast nozzle inside the hood is
directed downward and is moved in a circular horizontal orbit by a
variable speed motor to traverse the floor as the hood travels. An
air jet pump is attached to the hood to maintain a vacuum therein
and to withdraw from the hood a high velocity air stream entraining
the solid particles that are created by the sandblast operation.
The hood is manually steered and is driven by a variable speed
motor. Simply cutting off the supply of sand to the blast nozzle
enables the device to function as a vacuum cleaner in which clean
air discharged by the orbiting blast nozzle agitates particles of
debris on the floor and thus enable the air stream created by the
jet nozzle to entrain and remove the particles.
Inventors: |
Rose; James J. (Sylmar, CA),
Horton; Edward L. (San Gabriel, CA) |
Assignee: |
Enviro-Blast International (Los
Angeles, CA)
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Family
ID: |
27047617 |
Appl.
No.: |
05/518,579 |
Filed: |
October 29, 1974 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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483357 |
Jun 26, 1974 |
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360192 |
May 14, 1973 |
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Current U.S.
Class: |
451/92; 451/101;
451/350 |
Current CPC
Class: |
B24C
3/065 (20130101) |
Current International
Class: |
B24C
3/06 (20060101); B24C 3/00 (20060101); B24C
003/06 () |
Field of
Search: |
;51/8R,9M,14,15,174
;15/345,346 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Kelly; Donald G.
Attorney, Agent or Firm: Weilein; Paul A.
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of our copending
application of the same title, Ser. No. 483,357, filed June 26,
1974, now abandoned, which application is a continuation of Ser.
No. 360,192, filed May 14, 1973, now abandoned.
Claims
We claim:
1. In an apparatus to sandblast a surface, the combination of:
support structure,
said support structure including a first bearing having its axis
substantially normal to said surface;
rotatable structure having a tubular portion rotatable in said
bearing to support the rotatable structure;
a sandblast nozzle;
a second bearing on the rotatable structure rotatably embracing the
sandblast nozzle to permit relative rotation between the nozzle and
the second bearing, the second bearing directing the nozzle towards
said surface;
power means to actuate the rotatable structure about said axis,
said second bearing being spaced from said axis to carry the nozzle
along an arcuate path in response to rotation of the rotatable
structure; and
a hose to supply the nozzle,
a portion of the hose extending through said tubular portion of the
rotatable structure along said axis with an end portion of the hose
diverted from the axis to the blast nozzle in the second
bearing.
2. A combination as set forth in claim 1 which includes means
clamping said hose to resist rotation of said portion of the
hose.
3. A combination as set forth in claim 1 in which said power means
is a variable speed power means.
4. A combination as set forth in claim 1 which includes means to
vary the radial distance of said second bearing from said axis.
5. A combination as set forth in claim 1 in which said power means
continuously rotates the rotatable structure about said axis to
move the blast nozzle continuously in a circular orbit.
6. A combination as set forth in claim 1 which includes means to
space said first bearing a predetermined distance from said
surface,
said spacing means including roller means to roll along said
surface.
7. A combination as set forth in claim 1 which includes a
counterbalance for the blast nozzle, said counterbalance being
mounted on said rotatable structure at a position diametrically
opposite from the position of the second bearing.
8. A combination as set forth in claim 7 in which both said
counterbalance and said second bearing are adjustable radially of
said axis.
9. A combination as set forth in claim 8 in which said rotatable
structure includes a pair of opposite arms diverging from said
tubular portion at acute angles relative thereto, said two arms
supporting said blast nozzle and said counterweight.
10. A combination as set forth in claim 9 which includes a
transverse bar interconnecting the outer ends of said two arms,
the blast nozzle and the counterweight being adjustably mounted on
said transverse bar.
11. A combination as set forth in claim 1 which includes:
a hood united with said first bearing, said hood having an open
side confronting said surface to form therewith a vacuum
chamber;
means to draw air from the hood to maintain a vacuum therein and to
entrain solid particles produced by the sandblasting operation to
remove the particles from the vacuum chamber; and
means to space the hood from said surface, said spacing means
including roller means in rolling contact with the surface.
12. A combination as set forth in claim 11 in which the means to
space the hood from the surface is a frame carrying said roller
means.
13. A combination as set forth in claim 12 which includes power
means on the frame to actuate said roller means to cause the hood
to travel on said surface.
14. A combination as set forth in claim 13 in which said power
means is a variable speed motor.
15. A combination as set forth in claim 14 in which said roller
means includes dirigible roller means; and which includes manual
means to control the dirigible roller means to steer the hood.
16. A combination as set forth in claim 12 which includes means
mounting the hood on said frame, said mounting means being
yieldable to floatingly support the hood.
17. A combination as set forth in claim 12 which includes mounting
means to support the hood on the frame, said mounting means being
adjustable to vary the spacing of the hood from the surface.
18. A combination as set forth in claim 12 which includes means
mounting the hood on said frame, said mounting means including:
a plurality of circumferentially spaced apertured brackets on the
outer surface of the hood;
a corresponding plurality of screw threaded posts on the frame
extending upward through the corresponding apertured brackets;
a corresponding plurality of coil springs surrounding the screw
threaded posts in axial compression between the brackets and the
frame; and
a corresponding plurality of nuts on the posts bearing against the
upper sides of the brackets.
19. A combination as set forth in claim 11 which includes
rubber-like skirt means on the hood extending from the hood towards
said surface.
20. A combination as set forth in claim 19 in which said skirt
means embraces the hood and is slidingly adjustable axially
relative to the hood to vary the extent that the skirt extends
towards said surface.
21. A combination as set forth in claim 11 in which said hood is
provided with an outer rubber-like skirt and an inner rubber-like
skirt extending from the hood toward said surface;
and which includes a circumferentially extending brush means inside
the outer skirt reinforcing the outer skirt against inward
collapse.
22. A combination as set forth in claim 21 which includes spring
members extending downward from the inside of the hood to reinforce
said inner skirt against inward collapse.
23. A combination as set forth in claim 11 which includes a
rubber-like skirt extending downward from the hood towards said
surface;
and which includes baffle means movable with the blast nozzle to
protect said skirt means from abrasion by the stream from the blast
nozzle.
24. A combination as set forth in claim 11 in which said means to
draw air from the hood comprises:
a diffuser having its inlet end connected to the hood;
a jet nozzle at the inlet end of the diffuser; and
means to supply the jet nozzle with compressed air.
25. A combination as set forth in claim 24 which includes a duct
connected to the diffuser and an air cleaner connected to the duct
to separate the entrained solid particles.
26. A combination as set forth in claim 24 which includes:
an air line from a source of compressed air to said jet nozzle of
the diffuser;
a second air line from a source of compressed air to the blasting
nozzle;
a sand pot connected to the second air line; and
means to cut off the sand pot from the second air line to cause the
blast nozzle to discharge an air stream free from sandblast
particles.
27. Apparatus for sandblasting a work surface, comprising: a
carriage, wheels on the carriage for engagement with the surface, a
hood on the carriage forming a chamber having an opening at one
end, a closed end wall at the other end and a side wall between the
closed end wall and the opening, a bearing assembly mounted in the
end wall, a frame in the chamber, said frame comprising a rotating
drive member extending through said bearing assembly and having a
supported mounting therein, and a transverse beam having one end
extending from the axis of rotation of the drive member radially
outwardly toward the side wall of the hood, a power drive having a
rotating driving connection to said drive member, a nozzle having a
connection to the frame and directed toward the work surface, a
supply line for sand and air under pressure extending through said
bearing assembly to a connection with said nozzle, and an exhaust
line from the chamber for connecting the hood to a discharge
location.
28. Apparatus according to claim 27, wherein there is an adjustment
between the nozzle and the frame adjustable in a direction toward
and away from the work surface.
29. Apparatus according to claim 27, wherein there is an adjustment
between the nozzle and the frame adjustable in a radial
direction.
30. Apparatus according to claim 27, wherein there is a tilt
adjustment between the nozzle and the frame adjustable in a
direction changing the angle between the longitudinal axis of the
nozzle and the work surface.
31. Apparatus according to claim 27, wherein there is an adjustment
between the carriage and the hood adjustable in a direction toward
and away from the work surface.
32. Apparatus according to claim 27, wherein there is a perimetral
rim on the side wall of the hood surrounding said opening and a
flexible seal member on said rim adapted to travel over the work
surface and in engagement therewith to prevent passage of sand and
dirt residue from the chamber outwardly to the atmosphere.
33. Apparatus according to claim 32, wherein said flexible seal
member comprises a pluarality of inwardly turned bands.
34. Apparatus according to claim 33, wherein said flexible seal
member has a perimetrally extending brush element located between
outer and inner bands.
35. Apparatus according to claim 32, wherein there is a separator
for separating sand and dirt residue from clean air, said separator
being connected to a discharge end of said exhaust line, and means
adapted to generate a negative pressure in said exhaust line
greater than positive pressure in said chamber whereby to inhibit
expulsion of sand or dirt residue into the atmosphere.
36. Apparatus according to class 27, wherein there is a power drive
on the carriage in driving engagement with the wheels, and a
control interconnected with said power drive and said nozzle drive
means, at least one of said drives being variable whereby to enable
the speed of movement over the work surface to be varied relative
to the rate of rotation of the drive shaft and thereby vary the
cutting action of sand on the work surface.
37. Apparatus according to claim 27, wherein there is a section of
said supply line between the bearing assembly and the nozzle which
extends obliquely outwardly and describes a frusto-conical path
when the dirve member is rotated, and the side wall of said hood
has a frusto-conical shape slightly wider than said frusto-conical
path whereby to enable unrestricted rotation of the nozzle and at
the same time substantially minimize the size of said chamber.
Description
BACKGROUND OF THE INVENTION
This invention relates to the type of sandblasting apparatus in
which a hood is movable along a surface with the open side of the
hood adjacent the surface to cooperate therwith to form a traveling
chamber. A sandblast nozzle inside the chamber is directed towards
the surface and is continuously shifted in position inside the
traveling hood. Pump means is connected to the hood to maintain a
vacuum therein and to continuously draw an air stream from the hood
with the air stream entraining the solid particles that are
produced by the sandblast operation.
An apparatus of this general character is disclosed in the Cardon
U.S. Pat. No. 3,448,544, issued June 10, 1969.
SUMMARY OF THE INVENTION
One of the objects of the invention is to provide a hood-type
sandblasting apparatus that may be used on either vertical surfaces
or horizontal surfaces, but is specialized for operation on a floor
surface. For this purpose the hood is mounted by springs on wheels
that include drive wheels with provision for manual steering as the
drive wheels are actuated by a variable speed motor. For adjustment
of the clearance space between the hood and the floor surface, the
hood is vertically adjustable on a frame that carries the wheels
and in addition the hood is equipped with vertically adjustable
circumferential skirt means.
Another object of the invention is to actuate a blast nozzle inside
the traveling hood in a manner conducive to effective coverage of
the floor surface. Broadly described, this object is accomplished
by cyclically shifting the blast nozzle alternately towards the
opposite sides of the hood. In the preferred practice of the
invention the blast nozzle is continuously moved in a horizontal
circular orbit.
A feature of the invention is the manner in which the blast nozzle
is supported and actuated for orbital movement and the manner in
which the orbiting nozzle is supplied with a sandblast stream. A
rotary structure inside the hood having a vertical axis of rotation
is carried by a vertical tubular support that is journalled in a
first bearing in the top wall of the hood. The blast nozzle is
located on the rotary structure at a radial distance from the axis
of rotation for the purpose of the orbital movement of the nozzle.
A hose carrying the sandblast stream extends into the hood through
the tubular support along the axis of rotation of the rotary
structure with an end portion of the hose diverging from the axis
to the off-center blast nozzle. The blast nozzle itself is mounted
on the rotary structure by a second lower bearing. The air hose is
not intended to rotate on its own axis and preferably is
effectively clamped to resist such rotation. Thus, the divergent
end of the clamped hose is moved in the circular orbit by the
second bearing on the rotary structure that embraces the blast
nozzle, the second bearing rotating relative to the non-rotating
blast nozzle that it embraces.
Stability of the rotary structure is achieved by providing a
counterbalance for the blast nozzle with the counterbalance located
diametrically across the circular orbit from the location of the
blast nozzle. Both the distance of the blast nozzle from the axis
of rotation and the distance of the counterweight from the axis of
rotation are adjustable to permit change in the diameter of the
circular orbit. With a given blast stream and a given rate of
travel of the hood, the abrasive affect of the blast stream on the
floor surface may be intensified by narrowing the orbit of the
blast nozzle or vice versa and by lowering the orbit or vice
versa.
The hood is provided at its bottom rim with a skirt structure of
rubber-like material that extends towards the floor and that
readily yields to minor obstacles projecting from the floor, such
as rivets, bolt heads, and the like. In the preferred embodiment of
the invention the hood is provided with an outer skirt and an inner
skirt both of which bend radially inwardly at floor level. A
circumferential brush reinforces the outer skirt from the inside of
the skirt against inward collapse of the outer skirt and spring
members extending downward from the inner wall of the hood
reinforce the inner skirt against inward collapse. A feature of the
invention is the provision of a baffle that orbits with the blast
nozzle to prevent abrasion of the skirt structure by the blast
stream.
A further object of the invention is to prevent pollution of the
atmosphere by the solid particles that are produced by the
sandblasting operation and also to prevent accumulation of such
particles inside the traveling hood. For this purpose a high
velocity air stream is continuously withdrawn from the hood with
consequent maintenance of a relatively high vacuum in the hood. The
high vacuum prevents escape of the solid particles from the hood by
creating effective radially inward flow of air under the bottom of
the circumferential skirt structure of the hood. At the same time,
the high velocity air stream entrains the solid particles and
carries them through a hose to an air cleaner that isolates the
solid particles. The orbiting blast nozzle thoroughly agitates the
solid particles inside the hood to insure that the solid particles
are entrained by the outgoing high velocity discharge stream.
The invention teaches that important advantages may be achieved by
using a jet air pump to create the high velocity discharge stream
from the interior of the hood. For this purpose the inlet end of a
diffuser is attached to the hood and compressed air is fed to a jet
nozzle in the inlet end of the diffuser. One advantage of this
arrangement is that such an air pump is capable of creating as high
a rate of discharge flow as may be needed for efficient operation
of the apparatus. Another advantage is that a jet air pump has no
moving parts and is exceptionally light in weight. A further
advantage is that the jet air pump may be actuated from the same
source of compressed air as the orbiting blast nozzle.
A still further object of the invention is to provide an apparatus
of the character described that is capable of functioning as a
vacuum cleaner at exceptionally high efficiency. Conversion from
sandblasting operation to vacuum cleaning operation requires only
the closing of a single valve to isolate a sand pot from the stream
of compressed air that is fed to the blast nozzle. The resulting
blast of clean air from the orbiting nozzle is highly effective to
agitate debris on the floor surface and thus promote entrainment of
the debris by the high velocity air stream that is created by the
jet air pump.
This versatility of the apparatus makes possible impressive
savings, for example, in the sandblasting of the interior of an
upright storage tank. Sandblasting the upright inner surfaces of
such a tank results in the accumulation on the floor surface of a
deep layer of the solid particles that are created by the sandblast
operation. It has been found that one-third of the total cost of
sandblasting the interior of an upright tank is in the cost of
removing the accumulated deposit of solid particles in the
heretofore prevalent manner. With the present apparatus functioning
as a vacuum cleaner, the layer of accumulated particles may be
removed expeditiously with no manual labor. After the accumulated
layer of solid particles is removed by the vacuum operation, the
apparatus may be converted to sandblast operation to sandblast the
floor surface of the tank.
The features and advantages of the invention may be understood from
the following detailed description and the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings, which are to be regarded as merely
illustrative:
FIG. 1 shows the presently preferred embodiment of the invention in
side elevation with portions broken away and additionally shows
diagrammatically a system for supplying the apparatus with
compressed air and sandblast particles;
FIG. 1A is a fragmentary enlarged plan view as seen along the line
1A--1A of FIG. 1 showing one of the circumferentially spaced
brackets for yieldingly mounting the hood on a frame that is
equipped with ground wheels;
FIG. 2 is an overall plan view of the apparatus as seen along the
line 2--2 of FIG. 1;
FIG. 3 is a fragmentary vertical sectional view taken along the
line 3--3 of FIG. 1;
FIG. 4 is a fragmentary view similar to FIG. 3 with the orbiting
blast nozzle spaced a greater distance from the floor surface;
and
FIG. 5 is a horizontal sectional view taken along the line 5--5 of
FIG. 3.
DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENT OF THE
INVENTION
The drawings show a presently preferred embodiment of the invention
which is generally designated by reference numeral 10. A hose 11
supplies compressed air for the jet pump of the apparatus and a
hose 12 supplies the required stream of compressed air laden with
particles for sandblast operation. As shown diagrammatically in
FIG. 1, an air line from a source of compressed air has a branch
with a valve V-1 connected to hose 11 and has a branch with a valve
V-2 that is connected both to the hose 12 and to the top of a sand
pot. A short pipe controlled by a valve V-3 connects the outlet of
the sand pot to the hose 12. An exhaust line 13 conducts spend
sandblast material from the sandblast apparatus 10 to an air
cleaner 14.
As best shown in FIG. 2, the sandblast apparatus 10 includes a
carriage, generally designated 15. Two forward corner plates 16
supporting forward dirigible wheels 17 and 18, respectively, are
parts of a steering assembly that includes a forward crossbar 19.
The opposite ends of crossbar 19 are pivotally attached by
respective pins 20 and 21 to respective bell cranks 22 and 23 that
control the orientation of the forward wheels 17 and 18. The
carriage 15 has a square frame comprising horizontal beams 26, 27,
28 and 29 that rests at its foreportion on the plates 16.
Referring to FIGS. 1 and 2, drive wheels 30 on respective right and
left sides of the square frame are carried by a common drive shaft
31. The drive shaft 31 is mounted on brackets 32 (FIG. 1) which in
turn are carried by plates 33 and 34 on respective right and left
hand sides of the square frame.
A manual steering lever 36 is mounted by a pivot pin 37 on the
plate 34. A push-pull rod 38 is pivotally secured by a pin 39 to
the lower end of the steering lever 36, the opposite end of the
push-pull rod being secured by a pivot 40 to the bell crank 23 that
guides wheel 18. Thus, the push-pull rod serves to rotate both bell
cranks 22 and 23 to change the direction of the forward dirigible
wheels 17 and 18.
A variable speed electric motor 45 is mounted on plate 33 and its
shaft 46 carries a sprocket 47 which is connected by a sprocket
chain 48 to a driven sprocket 49 (FIG. 1) that is keyed to drive
shaft 31.
A hood 50 of frusto-conical form, which may be made of glass fibre
reinforced by resin, has its open side facing downward to cooperate
with the floor or work surface to serve as a mobile vacuum chamber.
The hood is carried by the square frame consisting of the
previously mentioned horizontal beams 26, 27, 28 and 29. The square
frame has four clips 56 on its four sides, respectively, and the
hood 50 has four corresponding brackets 57 spaced above the clips.
As shown in FIGS. 1 and 1A, screw threaded posts 58 extend upward
from the respective clips 56 through slots 59 in the brackets 57
and carry nuts 60 that bear against the upper sides of the
brackets. Coil springs 61 surrounding the respective screws 58 act
under compression between the clips and the brackets for yielding
support of the hood.
A tapered diffuser 62 of an air jet pump, generally designated 63,
is connected at its inlet end to the peripheral wall of the hood 50
and at its outer end is connected to the previously mentioned hose
discharge 13. The previously mentioned hose 11 supplies compressed
air to an annular jet nozzle 64 in the inlet end of the diffuser
62.
Referring to FIG. 3, the bottom rim 66 of the hood 50 is provided
with a multiple seal consisting of a circumferential outer flexible
rubber-like skirt 67, a circumferential inner flexible rubber-like
skirt 68 and a circumferential brush 69. The brush 69 is sandwiched
between the outer and inner flexible skirts and serves to reinforce
the outer skirt against inward collapse. The outer flexible skirt
67 may be long enough so that a radially inward toe 70 can underlie
the lower edge of the circumferential brush 69. The inner flexible
skirt 68 is made such that an arcuate portion 71 extends radially
inwardly from the rim 66 whereby to provide a tangential surface 72
capable of riding over the floor or work surface 73. U-shaped
retaining springs 74 secured by bolts 74' on each of four sides of
the rim 66 extend downwardly over the inner surface of the inner
flexible skirt 68 for reinforcement thereof against inward
collapse.
The sandblast operation is accomplished by a blast nozzle 75 which
is carried by a rotatable structure or frame that is indicated
generally by reference numeral 76. The rotatable frame 76 comprises
diagonal struts 77 and 78 terminating in lower respective leg
portions 79 and 80. A transverse beam 81 interconnects the free
ends of the leg portions 79 and 80, the connection being braced by
gusset plates 82 and 83.
At their upper ends the diagonal struts 77 and 78 are welded to and
supported by a collar 84. To rotationally mount the frame 76 on the
upper end wall 51 of the hood, a composite bearing assembly
indicated generally by the reference character 85 is provided. A
tubular drive member 86 is rotatably mounted in a bearing 87 in the
top wall of the hood. The bearing 87 rests on a washer 91 on the
outer face of the top wall of the hood 50, and the washer 91 is
connected to an inner washer 92 around an opening 94 in the hood by
means of bolts 95.
A sprocket 96 integral with the tubular drive member 86 is engaged
by a drive chain 97 that is driven by a drive sprocket 98 on a
drive shaft 99 of a variable motor 100 for rotating the frame 76.
The tubular drive member 86 supports the previously mentioned
collar 84 of the rotatable frame 76 by means of screws 101. The
motor 100 is supported on the previously mentioned horizontal beam
28 by a column 102.
In the present embodiment of the invention, the blast nozzle 75 is
moved in a circular orbit by the frame 76 but the blast nozzle
itself does not rotate on its own axis. Instead, a tiltable bearing
105 carried by the frame 76 rotates relative to the blast nozzle 75
as the tiltable bearing is carried in an orbit by the frame 76.
Thus, a flexible hose 106 which is a continuation of hose 12 and
not itself rotate on its own axis. The flexible hose 106 is
connected to a neck 107 of the blast nozzle 75 and extends along
the axis of rotation of the frame 76 through a passage 108 in the
collar 84 and a bore 109 in the tubular drive member 86.
A bracket 110 on the upper side of the hood 50 carries a clamp 111
that grips the hose 106 to prevent rotation of the hose on the hose
axis. A coupling 112 connects the flexible hose 106 to the supply
line 12. A roller bearing 113 on the upper end of the tubular drive
member 86 surrounds a collar 114 which embraces the flexible hose
106. The roller bearing 113 avoids imparting rotation of the hood
to the hose.
Sundry adjustments are provided for the blast nozzle 75 so that it
can be moved closer to or farther away from the work surface 73, or
moved radially outwardly or inwardly with respect to the center of
rotation of the frame 76, or moved to different angles of tilt.
For changing the location of blast nozzle 75 radially with respect
to the axis of rotation of the frame 76, the tiltable bearing 105
is carried by an angular plate 120 shown in FIGS. 3 and 5 and the
angular plate is attached to the transverse beam 81 by bolts 121
and 122. The bolts are adapted to slide in a slot 123 in the
transverse beam 81 for adjustment at selected radial distances from
the axis of rotation of the frame 76. A similar slot 124 on the
opposite side of the transverse beam provides for adjustably
positioning a counterweight 125 for the nozzle 75 by means of a
bolt 126.
For moving the blast nozzle 75 to different distances with respect
to the work surface 73, slots 127 and 128 are provided in the
respective leg portions 79 and 80. Bolts 129 and 130 in the
respective gusset plates 82 and 83 can be tightened or loosened as
needed to permit the transverse beam 81 to be adjusted, for
example, at the position shown in FIG. 3 or the higher position
shown in FIG. 4.
A baffle 131 having a tiltable mounting shown in FIGS. 3 and 4 is
secured by an arm 132 and a previously mentioned bolt 121 to the
transverse beam 81. A slot 133 in the arm 132 permits the baffle
131 to be extended or retracted to position the baffle to protect
the inner skirt 68 from the discharge of the blast nozzle 75
regardless of the adjustment of the nozzle location. The same
connection just described also permits the baffle to be tilted
variously depending upon the position of the tilt of the nozzle 75.
For tiltable adjustment of the blast nozzle, bolts 135 and 136 are
provided by means of which the ball-shaped body of the tiltable
bearing 105 can be tightened or loosened, thereby to fix the axis
of the bearing at a selected angle of adjustment.
A control box 138 of substantially conventional construction is
provided to control both the variable speed motor 45 and the
variable speed motor 100, suitable power being provided either by a
power cord (not shown) or by a battery. Controls 139 and 140 on the
control box 138 are manipulatable separately to vary the speed of
travel of the rig over the work surface and to vary the speed of
rotation of the frame 76 to provide for a greater or lesser cutting
effect of the sandblast when the apparatus is in operation.
In operation, the apparatus is guided on the wheels 17, 18 and 30
over the work surface 73, the skirts 67 and 68 of the hood being
kept in contact with the surface or close thereto. Although sand
and air under pressure are driven through the flexible hose 106 and
blast nozzle 75 into the interior of the hood, subatmospheric
pressure is maintained in the hood by the air jet pump 63. The
subatmospheric pressure inside the hood creates inward air flow
under the hood to prevent any sandblast particles from escaping
outwardly from under the edge of the skirt of the hood.
By making the system a closed system, i.e., by having the exhaust
line 13 pass directly to the air cleaner 14 through a conventional
vacuum pump 146, all of the solid particles released by the
operation pass to the air cleaner where they are separated from the
air so that only clean air passes outwardly through an air outlet
147. The separated solid particles are collected in a hopper
148.
The clearance of the two skirts 67 and 68 from the floor may be
varied by adjusting the nuts 60 to raise or lower the hood 50 or
may be varied by manually sliding up or down the portion of the
skirt structure that embraces the hood.
While the invention has herein been shown and described in what is
conceived to be a practical and effective embodiment, it is
recognized that departures may be made therefrom within the scope
of the invention, which is not to be limited to the details
disclosed herein but is to be accorded the full scope of the claims
so as to embrace any and all equivalent devices.
* * * * *