Note: Descriptions are shown in the official language in which they were submitted.
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TITLE: AIR RETURN FOR VENTURI SYSTEM
FIELD OF THE INVENTION
The present invention relates to an air return
which is used in an inline venturi system.
BACKGROUND OF THE INVENTION
In line venturi systems are used to move product
from place to another. An example of an inline venturi
system is described in my own United States Patent
5,002,092 issued March 26, 1991 where I use a blower
feeding air to a venturi device to create a low pressure
region causing air to be drawn into and through the system.
One of the keys to my earlier patented system is
the use of a static regain chamber downstream of the
venturi device which substantially enhances capacity of my
system.
In line venturi systems are typically limited in
the length of conduit that they can service simply because
the amount of air flow that can be generated at the
upstream end of the conduit drops over the length of the
conduit. After a certain conduit length, the air flow
drops to the point that the product will no longer move
through the conduit. With prior art techniques, the only
way to overcome this problem is to first drop the material
into a settling box or cyclone and then pick it up with a
further venturi and blower. This will not work with
certain types of material such as continuous strips of
material because the material would ball up once it is
settled into the box. Furthermore, whenever dust is
associated with ythe product and you drop it into the
settling box or cyclone it creates a serious dust problem.
This requires the addition of a dust collection
substantially adding to the cost of the prior art systems.
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SUMMARY OF THE INVENTION
The present invention relates to an air return
which is used in an inline venturi system of the type
having an upstream blower operated air induction member
causing a flow of induced air to move through a conduit
downstream of the air induction member.
The air return itself comprises a housing having a
product flow region to be fitted inline with the conduit
and an air draw region separated from the product flow
region by a perforate divider. A baffle is provided
internally of the divider. The air return further includes
an air return line from the air draw region to be fitted
back to the negative pressure side of the blower of the air
induction member.
The air return not only provides the static regain,
but in addition, because air is drawn from it by the
blower, it causes increased draw through the conduit at the
location of the air return. Therefore, by adding as many
venturies, air returns and blowers as are necessary, the
length of the conduit can be virtually limitless.
BRIEF DESCRIPTION OF THE DRAWINGS
The above as well as other advantages and features
of the present invention will be described in greater
detail according to the preferred embodiments of the
present invention in which;
Figure 1 is a schematic view of a venturi system
fitted with an air return unit in accordance with a
preferred embodiment of the present invention;
Figure 2 is a perspective view of the air return
unit when removed from the system of Figure l;
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Figure 3 is a perspective view of an internal
baffle arrangement used within the air return unit of
Figure 3;
Figure 4 is an enlarged perspective view of a
section from the baffle unit of Figure 3;
Figure 5 is a perspective view showing insertion of
the baffle unit of Figure 3 into the housing of the air
return unit of Figure 2;
Figure 6 is an end view of the housing with baffle
arrangement after assembly;
Figure 7 is a perspective view of a region of the
housing of Eigure 2 with part of the housing removed for
inspecting the internal construction of the air return
unit;
Figure 8 is a sectional view through the air return
unit of Figure 2;
Figure 8a is an enlarged sectional view through
some of the conical baffles used in the air return unit of
Figure 2.
Figure 9 is a schematic view of an alternate
venturi system from that shown in Figure 1 incorporating a
plurality of blowers, venturies and air returns feeding in
a common direction.
Figure 10 is a schematic view of still a further
venturi system reversible in direction of operation..
DETAILED DESCRIPTION ACCORDING TO THE PREFERRED
EMBODIMENTS OF THE PRESENT INVENTION
Figure 1 shows a pneumatic conveying system
generally indicated at 1. This system, like the system in
my earlier issued patent has an air induction venturi
member generally indicated at 3 at the upstream end of the
system. A product and air flow conduit 5 is located
downstream of the venturi device.
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In my earlier patent, I describe the use of a
static regain provided in the product flow conduit. This
static regain, according to my earlier patent, is a very
simple expansion of the conduit.
In the present application, rather than simply
enlarging the conduit, I provide an air return unit
generally indicated at 7. This air return unit not only
forms a static regain, but in addition, substantially
enhances the draw through the product flow conduit. This
is achieved because the blower generally indicated at 21
which is used to operate the venturi device 3 draws its air
from the air return unit and feeds that air to the venturi
device, therefore, not only is there an air induction at
the upstream end of the system, but in addition, there is
an air draw through the air return unit pulling product
downstream along the product flow conduit.
In order to produce an essentially endless venturi
system, a series of air return units, and venturies may be
provided at spaced intervals along the length of the
conduit. Furthermore, if required, additional venturi
devices may also be provided.
The air return unit itself comprises a main housing
8 having end connections 9 and 11 for fitting directly into
the conduit 5. Internally of housing 8 is a product flow
through region 13 which, as can be seen in Figure 1 is
directly in line with and forms a continuation of conduit
5. An air draw region 15 surrounds the product flow region
13 and the two regions are separated from one another by
means of a perforated screen 14. In the preferred
embodiment, the air return unit, like the product flow
conduit has a rounded configuration as best seen in Figure
2 of the drawings, and the screen dividing the product flow
region form the air draw region is rolled upon itself in a
cylindrical configuration.
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Again,according to the preferred construction,
screen 14 is more open than it is closed, i.e. it comprises
about 40% screen body and about 60% openings through the
screen body. The screen therefore allows a very
substantial movement of air from the product flow region to
the air draw region. However, at the same time, the screen
acts to filter product carried by the air flow from moving
from the product flow region into the air draw region.
The air return unit is looped or coupled back to
the negative pressure side of fan 21 by means of an air
return line 17. The air return line includes a divergent
mouth 19 opening through the wall of housing 8 to the air
draw region. The divergent shaping of mouth 19 adds to its
efficiency in that it tends to draw air from all around the
entire unit whereas, a straight mouth would tend to have a
much more localized air draw. It is to be noted in Figure
1 that the mouth 19 of air return line 17 is of
substantially the same configuration as the mouth 24 of air
line 23 through which air is provided by the blower to the
venturi device 3. This provides a balance of air flow from
the air return unit back to the venturi.
In addition screen 14 with its open mesh
construction provides an extremely efficient air spreader
to once again assist in equalizing the air draw
circumferentially and longitudinally of the air return unit
rather than having a much more localized draw which would
have a much greater tendency to undesirably pull the
product into the screen.
In one embodiment of the present invention, the air
return unit is provided with an internal baffle assembly
generally indicated at 25. This baffle assembly as best
seen having reference to Figures 3 through 8 of the
drawings is provided to prevent clogging of screen 14. It
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allows the air to be drawn from the product flow region but
blocks the product itself from being dragged into the
screen.
The actual construction of the baffle assembly is
best shown in Figure 3 of the drawings. It is formed by a
plurality of generally conical members 27 which are secured
side by side in line with one another by means of a baffle
frame comprising a longated securing strips 31 provided at
circumferentially spaced intervals around the baffle
assembly. The opposite ends of each of the strips 31 are
secured to an end cap 33 which terminates in an extended
mouth 34. As best seen in Figure 8 of the drawings, each
of the mouths 34 extends beyond the coupling ends 9 and 11
of the air return unit. As best seen in Figure 6 of the
drawings, the air return unit itself includes a quick
connect coupler, one being provided at each end of the unit
for direct connection of the air return unit to the product
flow line with the opposite end mouths 34 of the baffle
unit being fitted to the inside of the conduit.
Each of the cones 27 is turned or bent at its inner
free end 29 to lie essentially parallel with the direction
of air movement through the air return unit. This is best
seen having reference to figures 8 and 8a of the drawings.
The bending of the cone ends parallel to the direction of
air flow reduces turbulence in the air return unit. It also
prevents product from catching on the end of the cone.
Furthermore, it eliminates anything in the way of sharp
edges to which product would otherwise be exposed while
moving downstream to the baffle.
The baffle assembly provides a guide for product
flowing through the air return unit and because of the
downstream angling and substantially overlapping
positioning of the cones, they prevent product from moving
outwardly to the dividing screen between the product flow
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region and the air return region of the unit. However,
because of the radial gapping betweenthe cones, they do not
adversely affect the air draw from the product flow region
to the air draw region of the unit.
As clearly described above, the baffle assembly is
put together as a unitary structure outside of the air
return unit. This unitary structure is then fitted into
one end of the air return unit as shown in Figure 5 of the
drawings. The fully inserted position of the baffle or
assembly is shown in Figure 6 of the drawings.
When working with the baffle assembly the diameter
of the screen is widened relative to the product flow
conduit into the air return unit leaving room for the
baffle assembly so that the interior diameter of the cones
matches the interior diameter of the conduit once again
maintaining a uniform product flow passage through the
system.
The above above assembly of the air return unit is
very simple and efficient. As will be appreciated the
baffle assembly can be removed just as easily from the air
return unit if needed for maintenance purposes. In
addition, screen 14 can also be made removable from the
unit for cleaning and the like.
As best seen in Figure 2 of the drawings, the
housing 8 of the air return unit includes a removable cover
plate generally indicated at 35. Figure 7 of the drawings
shows the housing with the cover plate removed which allows
easy inspection of the interior of the air unit.
Figure 9 shows a system incorporating a plurality
of air return units 14, each cooperating with an associated
venturi 3 and blower 21 and feeding along a common feed
path 5. As will be seen, when using the air return units
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there is no need to add settling boxes and dust collectors.
The system of Figure 9 is extremely simple and efficient
and can be extended to substantially any desired length.
The system shown in Figure 1 feeds in one direction
only. Figure 10 shows a further venturi system generally
indicated at 41 which is reversible in its direction of
feed. This system includes a pair of venturi devices 3a
and 3b both of which operate using a single blower 21
common to both venturi devices. Blower 21 supplies
induction air along air flow path 43 feeding to venturi
device 3b or in the alternative along air flow path 43a
feeding venturi device 3a. A shut off device 45 is
provided in flow path 43a and a shut off device 47 is
provided in flow path 43b.
Located between the two venturi devices 3a and 3b
are conduit sections 5a and 5b with air return unit 6 being
placed between the two conduit sections. Air return unit 6,
feeds to an air return path 18 back to blower 21.
If it is desired to operate the system such that
the product flows from the left to the right hand side of
system 41, i.e. from venturi device 3a towards venturi
device 3b, shut off 47 in flow path 43b is closed and shut
off device 45 is left open such that the induction air from
blower 21 feeds to venturi device 3a along flow path 43a
and the return air is drawn along line 18 back to the
blower. In this example, conduit section 5a, the air return
unit, conduit section 5b and venturi device 3b are all
located downstream of venturi device 3a.
If it is desired to have product flow in the
opposite direction, then shut off device 45 is closed and
shut off device 47 is open. Blower 21 then feeds induction
air along line 43b to venturi device 3b. The return air
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from the air return unit feeds identically, i.e. along line
18 and back to blower 21.
Regardless of the direction of flow, only a single
air return unit is required because of its symmetrical
construction very similar to the constructionused in air
return unit 8 earlier described, except in this case it is
preferable to eliminate the baffle assembly which might
otherwise catch product flowing against the taper of the
baffle cones in the baffle.
It also should be noted that each of the venturi
devices has an essentially straight through internal
construction which allows product to flow completely
through therein if desired.
The shut off devices 45 and 47 can either be
automatically or manually operated. Furthermore, they can
be replaced with a single diverter located at the juncture
of the air flow paths 43a and 43b. The diverter would then
be appropriately positioned to direct air flow to either
one or the other of the two air flow paths and shut off the
flow of air to the unselected path.
The reversible system as described immediately
above has many different applications and one of particular
note is for use as an office message transmission system.
Although various preferred embodiments of the
present invention have been described herein in detail, it
will be appreciated by those skilled in the art, that
variations may be made thereto without departing from the
spirit of the invention or the scope of the appended
claims.
