Induction vacuum

An induction vacuum includes a cylindrical body having an inlet plate, an outlet plate, and a vacuum connector; a nozzle detachably mountable to the inlet plate, a mixing tube detachably mountable to the outlet plate and an exhaust bell detachably mountable to the mixing tube. An induction vacuum kit includes a body, a plurality of nozzles, a plurality of mixing tubes, and at least one exhaust bell. The nozzles and mixing tubes may include identifying indicia and the kit may include instructions recommending nozzle and mixing tube combinations for achieving different vacuum properties.

The present invention relates to surface preparation equipment and in 
particular to induction vacuums. 
In the sandblasting industry, discharged abrasive particles and debris 
particles dislodged from the surface being sandblasted are often 
retrieved. In recent years, the health and environmental dangers of lead 
have been increasingly recognized. Thus, retrieval is especially important 
when the sandblasting debris results from a surface bearing lead-based 
paint. The retrieval process, when performed simultaneously with 
sandblasting, also enables control of dust including lead. 
Air-compressors are typically employed in sandblasting. Induction vacuums 
also utilize a high pressure air supply to generate a vacuum. Induction 
vacuums therefore tend to offer an effective and compatible method for 
retrieving sand and particles. 
Currently available induction vacuums are expensive, complex in design, 
difficult to maintain and variable in efficiency. An advance in induction 
vacuum design which reduces capital cost, speeds assembly and maintenance, 
and increases versatility would be highly desirable. 
SUMMARY OF THE INVENTION 
An induction vacuum of the present invention includes a body, a nozzle, a 
mixing tube and an exhaust bell. The body has an inlet plate, an outlet 
plate, and a vacuum connector and, preferably, is generally cylindrical. 
The nozzle is detachably mountable to the inlet plate and preferably 
includes a mounting plate and a protuberance having an axial passage 
leading to a discharge orifice. The mixing tube is detachably mountable to 
the outlet plate and preferably includes a mounting plate and a tubular 
portion, terminating in a flair to provide an axial passage. The exhaust 
is detachably mountable to the mounting plate of the mixing tube and 
preferably shares a common means for mounting with the mixing tube. Most 
preferably the common means for mounting the mixing tube and exhaust bell 
include four threaded studs projecting from the outlet plate and a 
four-bolt hole pattern in the mounting plates of the mixing tube and 
exhaust bell. A preferred means for mounting the nozzle also includes four 
threaded studs projecting from the inlet plate and a four-bolt hole 
pattern in the mounting plate of the nozzle. 
The combination of the body, nozzle and mixing tube along with the mounting 
method and dimensions, causes the nozzle orifice and mixing tube intake 
flair to achieve a desired and effective alignment within the body, such 
that a high pressure air flow from the orifice into the mixing tube 
generates a vacuum within the body. The vacuum is used by allowing an air 
flow into the body through the vacuum connector. 
The present invention also envisions a kit including a body, a plurality of 
nozzles, a plurality of mixing tubes and at least one exhaust bell. 
Preferably, the nozzles and mixing tubes bear indicia for identifying the 
passage dimensions of the various nozzles and mixing tubes. Because the 
nozzles may be interchanged and the mixing tubes may be interchanged, it 
is possible to select particular members of the plurality to provide 
particular characteristics allowing an effective matching of the high 
pressure air supply and desired vacuum. Most preferably, an instruction 
set, outlining suggested combinations is included with the kit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A preferred embodiment of an induction vacuum of the present invention is 
shown in FIG. 1 at 20. The induction vacuum 20 includes 4 components: a 
body 22, a nozzle 24, a mixing tube 26, and an exhaust bell 28. 
The body 22 includes a cylindrical wall 32 having a first or input end 34 
and a second, or discharge end 36. The input end 34 is attached to an 
inlet plate 38 and the discharge end 36 is attached to an outlet plate 40. 
The inlet plate 38 has a 4-bolt mounting pattern 42 concentrically 
arranged about a longitudinal axis 44 of the body 20. Additionally, the 
inlet plate 38 includes a central aperture 46. Together, the 4-bolt 
arrangement 42 and aperture 46 allow for mounting of the nozzle 24. The 
outlet plate 40 includes 4-bolt holes 48 concentrically arranged about the 
axis 44. The outlet plate 40 further includes a centrally located aperture 
50 concentrically located about the axis 44. The bolt holes 48 and central 
aperture 50 of outlet plate 40 serve to allow insertion and mounting of 
the mixing tube 26. 
Preferably, the cylindrical wall 32 of the body 20 may be provided from a 
section of 8 inch schedule 40 steel pipe. The inlet and outlet plates 38 
and 40 are also preferably formed of steel and are permanently attached to 
the ends 34 and 36 of the body 22 preferably by welding. The wall 32 also 
includes an aperture 52. Preferably the aperture 52 is located adjacent 
the inlet plate 38. A vacuum connecting tube 54 is permanently attached to 
the aperture 52 of the cylindrical wall 32. Preferably the vacuum 
connector is also permanently attached to the wall 32 by welding. The 
preferred vacuum connector additionally includes an opposite end 56 and a 
bend 50 opposite end 56 in a generally parallel relationship with the wall 
32 and directed generally toward the outlet plate 40. 
The nozzle 24 includes a mounting plate 60 including a 4-bolt mounting 
pattern 62 with substantially the same spacing and sizing of bolt holes as 
the bolt pattern 42 of inlet plate 38. The end plate 60 further includes a 
short segment of cylindrical projection 64 concentrically arranged about 
the longitudinal axis of the nozzle 24. The radius of the cylindrical 
projection 64 is such that it will snugly fit within the aperture 46 of 
the inlet plate 38. The 4-bolt pattern 62, as shown in FIG. 2, and the 
cylindrical projection 64 of the nozzle 24, as shown in FIG. 1, enable 
mounting of the nozzle to the inlet plate 38 such that the longitudinal 
axis of the nozzle 24 becomes coincident with the longitudinal axis 44 of 
the body 22. The nozzle 24 further includes a protuberance 65 axially 
extending from the cylindrical projections 64 and having a hollow 
cylindrical wall 66 leading to a frustoconical surface 68 and a discharge 
orifice end 70. Within the nozzle 24 is an axial passage 72 and a 
constriction 74 preferably located within the frustoconical portion 68 of 
the nozzle 24. The passage 72 also includes a slight expansion or increase 
in bore past the constriction 74 and extending to the discharge orifice 
70. 
The mixing tube 26 includes a circular mounting plate 78. The mounting 
plate 78 also includes a 4-bolt pattern 80, as shown in FIG. 3, and a 
concentrically arranged cylindrical extension 82, as shown in FIG. 1. The 
radius of the extension 82 is such that it will closely fit within the 
aperture 50 of the outlet plate 40. The arrangement of the bolt holes 80 
is such that they may be aligned with the bolt holes 48 of the outlet 
plate 40 while the cylindrical portion 82 is fit snugly within the 
aperture 50 so as to mount the mixing tube 26 generally within the body 22 
with the longitudinal axis of the mixing tube 26 coincident with the axis 
44 of the body 22. Projecting from the raised portion 82 is an axially 
extending central tube 84 which terminates in an intake flair or bell 86. 
The interior passage created by the tube 84 and bell 86 includes a flared 
mouth 88 beginning at the belled terminus 86 and leading to a cylindrical 
inner wall 90. 
When the nozzle 24 and the mixing tube 26 are both appropriately mounted 
upon the body 22, the discharge orifice 70 of the nozzle 24 is located 
concentrically within the mixing tube 26 at a point 92 where the flared 
mouth 88 meets the inner wall 90. 
The exhaust bell 28 also includes a circular mounting plate 94 having a 
4-bolt concentrically arranged mounting pattern 96 and a frustoconical 
shaped wall 98 enclosing a frustoconical passage 100 which is 
concentrically arranged about the longitudinal axis of the exhaust bell 28 
and increases in diameter from the mounting plate 94 to a terminus 104. A 
cylindrical flange 106 also having a 4-bolt pattern 108 projects radially 
outward at the terminus 104. 
The radius of the greatest extent of the flair 86 is such that it may pass 
through the aperture 50. Thus, allowing the mixing tube 26 to be fully 
removed from its assembled position within the body 22. 
A standard pipe flange 110, including a 4-bolt hole pattern 112 which 
matches the 4-bolt pattern of the inlet plate 38 and the nozzle 24 may be 
provided for placement over the nozzle 24. 
Preferably, knurled studs 114 and 116, as shown in FIG. 4, are provided for 
detachable mounting of the nozzle 24 and the pipe flange 110 to the inlet 
plate 38 and the mixing tube 26 and exhaust bell 28 to the outlet plate 
40. The knurled studs 114 and 116 are arranged within the inlet and outlet 
plates 38 and 40 such that the heads of the studs 114 and 116 are within 
the body 22 and the threaded portions of the studs are directed outward 
and project from the 4-bolt pattern on the inlet and outlet plates 38 and 
40 to facilitate convenient mounting of the plates 60, 110, 78 and 94. The 
various components may be secured by tightening hexnuts onto the 
protruding studs and optionally including lockwashers 117. Because the 
nozzle 24 and mixing tube 26 are each radially symmetrical and the four 
studs projecting from each of the inlet and outlet plates 38 and 40 are 
also radially symmetrical about the axis 44 of the body 22, assembly 
merely involves alignment of the mounting plate 60 or 78 with the studs. 
That is, proper alignment is achieved in any of the four rotations in 
which the holes align with the studs. 
The induction vacuum functions by provision of a high-pressure air source 
to the nozzle 24, preferably by a threaded connection within the pipe 
flange 110. A flow of air from the pipe flange 110 through the nozzle 24 
and continuing through the cylindrical passage 90 and onward through the 
interior passage 100 of the exhaust bell 28, creates a region of 
low-pressure within the mixing tube 26. In response, suction is created 
drawing air or other materials from the interior of the body 22 past the 
flared bell 86 and inward through the flared passage 88 to join the main 
flow of air within the cylindrical passage 90. This in turn creates 
suction and typically air flow within the suction tube 54 and toward the 
passage 90. The suction may be used to pick up material such as sand or 
paint chips. Materials, such as sand or paint chips, entrained within an 
air flow traveling through the vacuum connection 54 toward the mixing tube 
26 may either continue to travel through the induction vacuum 20 or 
alternatively and preferably may be trapped by well-known procedures in 
this art, such as expansion chambers or filters prior to entering the 
induction vacuum 20. 
The induction vacuum 22 may be conveniently mounted on a frame, for example 
the frame of an air compressor, by employing "U" bolts about the body. For 
a body having an 8-inch diameter, two 8-inch "U" bolts are satisfactory. 
The present invention offers the advantage, relative to the prior art, of 
easy maintenance, simple assembly, relatively few parts, and low-cost 
production. Additionally, the induction vacuum of the present invention is 
relatively lightweight, due to its cast aluminum parts. Production costs 
are relatively low since the only machining typically required in 
production of the cast aluminum parts is machining on the faces of the 
nozzle mounting plate 60 and the wall of the cylindrical extension 46, as 
well as machining of the adjoining faces of the mixing tube 26 and exhaust 
bell 28. 
Preferably, the nozzle 24, mixing tube 26 and exhaust bell 28 are prepared 
by casting aluminum. Only minor drilling and machining of a few faces is 
required for additional production of these parts. Preferably, the 
portions of the mounting plate 60 which contact the inlet plate 38 and the 
pipe flange 110 should be machined to minimize any air leakage. Similarly, 
it is preferable to machine the portions of the mounting plate 78 which 
contact the outlet plate 40 and the exhaust bell 28. Similarly, the 
portion of the exhaust bell 28 contacting the mounting plate 78 should be 
machined. 
An additional advantage of the present invention, particularly when minor 
matching to promote a leak-free fit, relative to the prior art, includes 
the lack of any requirement for O-rings during assembly. Optionally, the 
faces may be coated with a silicon caulking prior to assembly. 
Suitable constriction 74 may be from about 0.200 inches to about 0.750 
inches. Suitable diameters for the interior of the mixing tube 90 would be 
from about 1.0 inches to about 3.0 inches. Preferable combinations of 
orifices 74 and mixing tube diameter 90 would be, for example, 0.25 inches 
constriction and 1.04 inch mixing tube diameter; 0.450 inch constriction 
with about 1.87 inch diameter of the mixing tube 90; and for example, 0.65 
inch diameter constriction with a mixing tube diameter of about 2.70 
inches. The most preferable combination of constriction and mixing tube 
diameter is about 0.45 inches and a 1.5 inch diameter within the mixing 
tube, when employed with 125 PSI air supply using approximately 335 cfm 
produces approximately 15 inches mercury of reduced pressure, and will 
consume approximately 600 cfm through a four inch vacuum connector 56. 
In a further embodiment of the present invention, the nozzle 24 and mixing 
tube 26 may be interchanged with other substitute nozzles and mixing 
tubes. Preferably, the induction vacuum of this embodiment is supplied as 
kit, including: a body, a selection or set of several nozzles and several 
mixing tubes and one or preferably several exhaust bells. Preferably, the 
interchangeable members of the sets, (i.e., the nozzle and mixing tube 
combinations) each include identifying indicia to facilitate selection of 
a appropriate nozzle and mixing tube pair. The kit may also include 
appropriate instructions and selection suggestions for various 
applications. The substitution of nozzles and mixing tubes, preferably as 
matched pairs, allows versatility to be incorporated in an induction 
vacuum since the vacuum may be altered to best match a particular high 
pressure air supply and vacuum requirements. Additionally, should the 
induction require repair of a worn or damaged nozzle 24 or mixing tube 26, 
easy removal and substitution may be achieved. Although the present 
invention has been described with reference to the preferred embodiments, 
workers skilled in the art will recognize that changes may be made in form 
and detail without departing from the spirit and scope of the invention.