U.S. patent application number 15/887383 was filed with the patent office on 2018-06-07 for pneumatic material delivery system with air flow limiting.
This patent application is currently assigned to Novatec, Inc.. The applicant listed for this patent is Stephen B. Maguire, Novatec, Inc.. Invention is credited to Stephen B. MAGUIRE, James ZINSKI.
Application Number | 20180155136 15/887383 |
Document ID | / |
Family ID | 58523505 |
Filed Date | 2018-06-07 |
United States Patent
Application |
20180155136 |
Kind Code |
A1 |
MAGUIRE; Stephen B. ; et
al. |
June 7, 2018 |
PNEUMATIC MATERIAL DELIVERY SYSTEM WITH AIR FLOW LIMITING
Abstract
Apparatus for conveying granular material from a supply to
receivers that retain and dispense the material when needed by
process machine include a vacuum pump, an air flow limiter
connected to the vacuum pump, a first conduit connecting the
receivers to the air flow limiter, and a second conduit connecting
the material supply to the receivers.
Inventors: |
MAGUIRE; Stephen B.; (West
Chester, PA) ; ZINSKI; James; (Ellicot City,
MD) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Maguire; Stephen B.
Novatec, Inc. |
West Chester
Baltimore |
PA
MD |
US
US |
|
|
Assignee: |
Novatec, Inc.
Baltimore
MD
|
Family ID: |
58523505 |
Appl. No.: |
15/887383 |
Filed: |
February 2, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15392650 |
Dec 28, 2016 |
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15887383 |
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14804404 |
Jul 21, 2015 |
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15392650 |
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14602784 |
Jan 22, 2015 |
9550636 |
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14804404 |
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14593010 |
Jan 9, 2015 |
9550635 |
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14602784 |
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14574561 |
Dec 18, 2014 |
9604793 |
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14593010 |
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14185016 |
Feb 20, 2014 |
9371198 |
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14804404 |
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62027379 |
Jul 22, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B65G 53/58 20130101;
B29C 31/002 20130101; B65G 53/66 20130101; B65G 53/24 20130101 |
International
Class: |
B65G 53/24 20060101
B65G053/24; B65G 53/58 20060101 B65G053/58; B29C 31/00 20060101
B29C031/00 |
Claims
1. Apparatus for conveying granular plastic resin from a supply to
receivers that retain and dispense the resin when needed by a
process machine, comprising: a) a vacuum pump; b) an air flow
limiter connected to a suction head of the vacuum pump; c) a first
conduit connecting the receivers to the air flow limiter; and d) a
second conduit connecting the supply to the receivers; whereby
suction created by operation of the vacuum pump draws granular
plastic resin from the supply into the receivers through the second
conduit and draws air from the second conduit through the
receivers, the first conduit and the air flow limiter.
2. Apparatus of claim 1 wherein the air flow limiter further
comprises: a) a tube; b) a pair of open-ended tubular segments
within the tube, an outer tubular segment being fixed and the other
being slideably axially movable along the fixed segment; c) a plate
extending partially across the interior of the tube, positioned for
contacting and limiting travel of the moveable tubular segment, the
plate covering an outlet end of the movable tubular segment upon
contact therewith; d) a sail connected to the moveable segment,
positioned in the tube upstream of the segments.
3. Apparatus of claim 2 wherein the tubular segments are
telescoping.
4. Apparatus for conveying granular plastic resin from a supply to
receivers that retain and dispense the resin when needed by a
process machine, comprising: a) a vacuum pump; b) air flow limiters
connected to outlets of the receivers; c) a first conduit
connecting the air flow limiters to a suction head of the vacuum
pump; and d) a second conduit connecting the supply to the
receivers; whereby suction created by operation of the vacuum pump
draws granular plastic resin from the supply into the receivers
through the second conduit and draws air from the second conduit
through the receivers, the air flow limiters and the first
conduit.
5. The apparatus of claim 4 wherein at least one of the air flow
limiters consists of: a) a tube; b) a pair of open-ended tubular
segments within the tube, an outer tubular segment being fixed and
the other being slideably axially movable along the fixed segment;
c) a plate extending partially across the interior of the tube,
positioned for contacting and limiting travel of the moveable
tubular segment, the plate covering an outlet end of the movable
tubular segment upon contact therewith; d) a sail connected to the
moveable segment, positioned in the tube upstream of the
segments.
6. Apparatus of claim 1 wherein the air flow limiter comprises: a.
a tube; b. a valve within and connected to the tube; and c. a
baffle located within and connected to the tube, positioned to
direct air flow within the tube against the valve.
7. Apparatus of claim 6 wherein the valve comprises a pair of
telescoping tubular segments.
8. Apparatus of claim 7 wherein the outer one of the telescoping
tubular segments is fixed by and the inner one of the telescoping
tubular segments is slidably moveable along the fixed segment in
the axial direction with the tube.
9. Apparatus of claim 8 wherein the valve further comprises a plate
extending partially across the interior of the vertically oriented
tube, being connected to the tube and positioned for contacting a
moveable one of the telescoping tubular segments.
10. Apparatus of claim 9 wherein the valve further comprises a sail
within the vertically oriented tube, connected to the moveable one
of the telescoping tubular segments.
11. Apparatus of claim 4 wherein the air flow limiter further
comprises: a. a tube; and b. a valve within and connected to the
tube; and a baffle located within and connected to the tube,
positioned to direct air flow within the tube against the
valve.
12. Apparatus of claim 11 wherein the valve comprises a pair of
telescoping tubular segments.
13. Apparatus of claim 12 wherein the outer one of the telescoping
tubular segments is fixed and the inner one of the telescoping
tubular segments is slidably moveable along the fixed segment in
the axial direction with the tube.
14. Apparatus of claim 13 wherein the valve further comprises a
plate extending partially across the interior of the vertically
oriented tube, being connected to the tale and positioned for
contacting a moveable one of the telescoping tubular segments.
15. Apparatus of claim 14 wherein the valve further comprises a
sail within the vertically oriented tube, connected to the moveable
one of the telescoping tubular segments.
16. Apparatus for conveying granular plastic resin from a supply to
receivers that retain and dispense the resin when needed by a
process machine, consisting of: a) a vacuum pump; b) an air flow
limiter connected to a suction head of the vacuum pump; c) a first
conduit connecting the receivers to the air flow limiter; and d) a
second conduit connecting the supply to the receivers; whereby
suction created by operation of the vacuum pump draws granular
plastic resin from the supply into the receivers through the second
conduit and draws air from the second conduit through the
receivers, the first conduit and the air flow limiter.
17. Apparatus for conveying granular plastic resin from a supply to
receivers that retain and dispense the resin when needed by a
process machine, consisting of: a) a vacuum pump; b) air flow
limiters connected to outlets of the receivers; c) a first conduit
connecting the air flow limiters to a suction head of the vacuum
pump; and d) a second conduit connecting the supply to the
receivers; whereby suction created by operation of the vacuum pump
draws granular plastic resin from the supply into the receivers
through the second conduit and draws air from the second conduit
through the receivers, the air flow limiters and the first
conduit.
18. Apparatus for conveying granular plastic resin from a supply to
receivers that retain and dispense the resin when needed by a
process machine, consisting essentially of: a) a vacuum pump; b) an
air flow limiter connected to a suction head of the vacuum pump; c)
a first conduit connecting the receivers to the air flow limiter;
and d) a second conduit connecting the supply to the receivers;
whereby suction created by operation of the vacuum pump draws
granular plastic resin from the supply into the receivers through
the second conduit and draws air from the second conduit through
the receivers, the first conduit and the air flow limiter.
19. Apparatus for conveying granular plastic resin from a supply to
receivers that retain and dispense the resin when needed by a
process machine, consisting essentially of: a) a vacuum pump; b)
air flow limiters connected to outlets of the receivers; c) a first
conduit connecting the air flow limiters to a suction head of the
vacuum pump; and d) a second conduit connecting the supply to the
receivers; whereby suction created by operation of the vacuum pump
draws granular plastic resin from the supply into the receivers
through the second conduit and draws air from the second conduit
through the receivers, the air flow limiters and the first
conduit.
20. Apparatus for conveying granular plastic resin from a supply to
receivers that retain and dispense the resin when needed by a
process machine, comprising: a) a vacuum pump; b) an air flow
limiter connected to a suction head of the vacuum pump; the air
flow limiter comprising: i) a tube; ii) a pair of open-ended
tubular segments within the tube, an outer tubular segment being
fixed and the other being slideably axially movable along the fixed
segment; iii) a plate extending partially across the interior of
the tube, positioned for contacting and limiting travel of the
moveable tubular segment, the plate covering an outlet end of the
movable tubular segment upon contact therewith; iv) a sail
connected to the moveable segment, positioned in the tube upstream
of the segments. c) a first conduit connecting the receivers to the
air flow limiter; and d) a second conduit connecting the supply to
the receivers; whereby suction created by operation of the vacuum
pump draws granular plastic resin from the supply into the
receivers through the second conduit and draws air from the second
conduit through the receivers, the first conduit and the air flow
limiter.
21. Apparatus for conveying granular plastic resin from a supply to
receivers that retain and dispense the resin when needed by a
process machine, consisting of: a) a vacuum pump; b) an air flow
limiter connected to a suction head of the vacuum pump; the air
flow limiter consisting of: i) a tube; ii) a pair of open-ended
tubular segments within the tube, an outer tubular segment being
fixed and the other being slideably axially movable along the fixed
segment; iii) a plate extending partially across the interior of
the tube, positioned for contacting and limiting travel of the
moveable tubular segment, the plate covering an outlet end of the
movable tubular segment upon contact therewith; iv) a sail
connected to the moveable segment, positioned in the tube upstream
of the segments. c) a first conduit connecting the receivers to the
air flow limiter; and d) a second conduit connecting the supply to
the receivers; whereby suction created by operation of the vacuum
pump draws granular plastic resin from the supply into the
receivers through the second conduit and draws air from the second
conduit through the receivers, the first conduit and the air flow
limiter.
Description
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS
[0001] This patent application is a 35 USC 120 division of
co-pending U.S. Ser. No. 15/392,650, filed 28 Dec. 2016 in the
names of Stephen B. Maguire and James Zinski, published 20 Apr.
2017 as US 2017/0107064 A1.
[0002] The '650 patent application was a 35 USC 120
continuation-in-part of U.S. Ser. No. 14/574,561 entitled "Resin
Delivery System with Air Flow Regulator" filed 18 Dec. 2014 in the
name of Stephen B. Maguire, issued 28 Mar. 2017 as U.S. Pat. No.
9,604,793.
[0003] The '650 patent application was also a 35 USC 120
continuation-in-part of U.S. Ser. No. 14/602,784 entitled "Method
and Apparatus for Resin Delivery with Adjustable Air Flow Limiter"
filed 22 Jan. 2015 in the name of Stephen B. Maguire, issued 24
Jan. 2017 as U.S. Pat. No. 9,550,636.
[0004] The '650 patent application was yet also a 35 USC 120
continuation-in-part of co-pending U.S. Ser. No. 14/804,404
entitled "Vacuum Powered Resin Loading System Without Central
Control" filed 21 Jul. 2015 in the name of Stephen B. Maguire,
published 12 Nov. 2015 as US 2015/0321860 A1.
[0005] The '650 application also claimed under 35 USC 120 the
benefit of the priority of U.S. provisional application Ser. No.
62/027,379 entitled "Central Vacuum Loading System Without Central
Control", filed 22 Jul. 2014 in the name of Stephen B. Maguire.
[0006] The '650 patent application was further a 35 USC 120
continuation-in-part of U.S. Ser. No. 14/593,010 entitled "Air Flow
Limiter with Closed/Open Sensing", filed 9 Jan. 2015 in the name of
Stephen B. Maguire, issued 24 Jan. 2017 as U.S. Pat. No.
9,550,635.
[0007] The '650 patent application still further claimed under 35
USC 120, through parent application Ser. No. 14/804,404 filed 21
Jul. 2015, the benefit of the priority of U.S. Ser. No. 14/185,016
entitled "Air Flow Regulator" filed 20 Feb. 2014 in the name of
Stephen B. Maguire, which issued 21 Jun. 2016 as U.S. Pat. No.
9,371,198.
[0008] This application claims the benefit of the priority of the
'650 application under 35 USC 120 and also claims the benefit of
the priority, through the '650 application under 35 USC 120, of all
of the patent applications and issued patents listed above to which
the '650 application claimed priority.
Incorporation by Reference
[0009] The disclosures of the '404 application and the '793, '636,
'635 and '198 patents are hereby incorporated by reference.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND
DEVELOPMENT
[0010] Not Applicable.
BACKGROUND OF THE INVENTION
Field of Invention
[0011] This invention relates principally to manufacture of plastic
articles and even more particularly relates to pneumatic conveyance
and processing of plastic resin pellets, as well as other granular
materials, prior to molding, extrusion, or other processing of
those pellets or other granular materials into a finished or
semi-finished product.
[0012] In this patent application, injection and compression
molding presses and extruders are collectively referred to as
"process machines."
BACKGROUND OF THE INVENTION
Description of the Prior Art
[0013] Current resin and other granular material central loading
systems concerned with conveying granular material from a storage
area for molding or extrusion typically include a vacuum pump or
pumps and multiple receivers.
[0014] In some systems, with many receivers, several small pumps
are used.
[0015] It would be less expensive to use only one, or fewer, larger
pumps. However, a larger pump may draw too much air with resulting
damage to the material being conveyed. While a larger pump could
load several receivers at once, there is a risk that an "open"
line, namely a line drawing only air, and no material, would cause
the vacuum to drop too much, and no material would load. Also, when
only one receiver is loading material, air velocity might be too
high, again with a risk of damaging the material.
[0016] Nevertheless, in facilities that fabricate products by
molding or extrusion, it is common to use such vacuum loading
systems to pneumatically convey pellets of thermoplastic resin or
other materials, prior to molding, extrusion, or other processing
of those pellets or other materials into a finished or
semi-finished product. The materials are typically purchased in 50
pound bags, 200 pound drums, or 1,000 pound containers commonly
referred to as "Gaylords."
[0017] A preferred approach for conveying plastic resin pellets and
other granular materials from a storage location to a process
machine, which approach is often used in larger facilities, is to
install a central vacuum pump or even several vacuum pumps,
connected by common vacuum lines to multiple "receivers."
[0018] Vacuum pumps connected to the vacuum lines draw vacuum,
namely air at pressure slightly below atmospheric, as the vacuum
pump sucks air through the "vacuum" line. The suction moves large
quantities of air which carries thermoplastic resin pellets or
other granular material through the "vacuum" line.
[0019] An alternative is to use positive pressure produced by
either a blower or the exhaust side of a vacuum pump. With such an
approach, the positive pressure results in movement of substantial
amounts of air which may be used to carry the granular material.
However, the vacuum approach of drawing or sucking granular
material through the system conduits is preferable to the positive
pressure approach of pushing the material granules through the
system conduits.
[0020] In practice, vacuum pumps are preferred and vacuum lines are
desirable in part because power requirements to create the required
vacuum necessary to draw granular materials through the lines are
lower than the power requirements if the material granules are
pushed through the lines by a blower or by the exhaust side of a
vacuum pump. When vacuum is used, the static pressure within the
line may be not much less than atmospheric. When positive pressure
is used, the dynamic pressure of the air flowing through the line
must be relatively high in order to move an adequate quantity of
granular material.
[0021] As used herein, and in light of the foregoing explanation,
the terms "vacuum pump" and "blower" are used interchangeably.
[0022] When one or more central vacuum pumps are connected to
multiple receivers, a receiver is typically located over each
temporary storage hopper, in which the plastic resin pellets or
other granular material is temporarily stored before being molded,
extruded, or otherwise processed. A temporary storage hopper is
typically associated with each process machine.
[0023] In current practice, the receiver is connected by a control
wire to a central control system. The control system works by
selectively opening a vacuum valve located in each receiver,
allowing one or several vacuum pumps to work in sequence drawing
"vacuum", i.e. below atmospheric pressure air, to carry the pellets
or other material granules among and to multiple receivers as
individual ones of the receivers, positioned over individual
hoppers associated with the individual process machines, require
additional plastic resin pellets or granules of other material. The
receiver for a given hopper-process machine combination is actuated
by opening the vacuum valve located in or near the receiver,
causing the receiver to supply plastic resin pellets or granules of
other material by gravity feed into the hopper from where the
pellets or other material granules may be fed further downwardly by
gravity into the associated process machine.
[0024] Large, high capacity industrial vacuum pumps are reliable
and are suited to heavy duty industrial use. Large high capacity
vacuum pumps allow long conveying distances for the plastic resin
pellets and other granular materials. Currently available large
capacity vacuum pumps permit plastic resin pellets and other
granular materials that are similar in size and density to be
conveyed over distances of 200 feet or more using vacuum drawn by
the pump. Use of such high capacity vacuum pumps results in a rush
of below atmospheric pressure air through the line, carrying the
plastic resin pellets or other granular materials over a long
distance.
[0025] Operators of manufacturing facilities prefer to buy plastic
resin pellets and other necessary granular materials in bulk, in
rail cars or tanker trucks. Bulk purchases result in cost savings.
Such materials delivered in bulk are typically pumped into large
silos for storage. In a large manufacturing facility, the distance
from a plastic resin pellet or other material storage silo to a
process machine may be several hundred feet, or more. Accordingly,
when plastic resin pellets or other granular materials are
purchased in bulk, a central vacuum-powered conveying system,
powered by one or more large, high capacity industrial vacuum
pumps, is a necessity.
[0026] Typically, large central plastic resin pellet and other
similar granular material conveying systems have one or more vacuum
pumps, each typically from 5 to 20 horsepower. These central
systems include central controls connected by wire to each receiver
associated with each process machine in the facility. Typically
eight, sixteen, thirty-two or sixty-four receivers, each associated
with a process machine, may be connected to and served by the
central vacuum conveying system. Of course, the higher the number
of receivers served by the system, the higher the cost.
[0027] A factor to be considered in designing such a system is the
speed of the plastic resin pellets or other material granules as
they flow through a conduit as the pellets or granules are carried
by the moving air stream drawn by the vacuum pump. If air flow is
too slow, the pellets or other granules fall out of the air stream
and rest on the bottom of the conduit, with resulting risk of
clogging the conduit. If air flow is too fast, the pellets or other
granules can skid along the conduit surface. In such case, harder,
more brittle plastic resin pellets and other granular materials may
be damaged, resulting in dust within the conduit, which when drawn
into the vacuum pump can damage the vacuum pump and render the
system inoperative. Softer plastic resin pellets and other soft
granular materials heat up and can melt from friction when
contacting the conduit interior surface. In the case of plastic
resin pellets, this results in "angel hair"--long, wispy-thin
strands of plastic film which eventually clog the conduit and cause
the system to shut down.
[0028] For these reasons, pneumatic plastic resin pellets and other
granular material conveying systems must be designed to produce
desired, reasonable conveying speeds for the conveyed
materials.
[0029] Currently, conveying speed of the plastic resin pellets and
other granular material is most often controlled by controlling air
flow, measured in cubic feet per minute, and varying the desired
and designed cubic feet per minute based on conduit diameter, with
a larger diameter conduit requiring more cubic feet per minute of
air flow to maintain proper air flow speed through the conduit.
Controlling air flow, measured in cubic feet per minute, is
conventionally done by properly specifying the vacuum pump by
capacity and, in some cases, by varying speed of the vacuum pump as
the vacuum pump draws the air in a "vacuum" condition through the
conduit, carrying plastic resin pellets or other material granules
in the moving, below atmospheric pressure air. Controlling cubic
feet per minute of air flow is an indirect way of controlling
plastic resin pellet or other material granule speed as the pellets
or other granules flow through a conduit of a given diameter.
[0030] Typically, a 2 inch diameter conduit requires about 60 cubic
feet per minute of air flow to convey typical plastic resin pellets
or other granular material of similar size and density
characteristics. A 21/2 inch diameter conduit typically requires
about 100 cubic feet per minute of air flow to convey typical
plastic resin pellets or other granular material. To achieve these
desired air volume flow rates, a conventional designer must
carefully match the horsepower of a vacuum pump, which has a given
cubic feet of air per minute rating, to a selected size conduit,
taking into consideration the average distance the plastic resin
pellets or other material granules must be conveyed through the
conduit from a storage silo to a receiver or loader. If this
results in selection of a 5 horsepower blower/vacuum pump, then a
given facility may require several such blowers/vacuum pumps, with
each blower/vacuum pump supplying only a selected number of
receivers.
[0031] A single plastic resin molding or extruding facility or
another type of granular material processing facility might
theoretically require a 20 horsepower blower and the corresponding
cubic feet per minute capability for conveyance provided by the
single blower to meet the total conveying requirements for plastic
resin pellets or other material granules throughout the facility.
However, a single twenty horsepower blower would result in far too
high a conveying speed for the plastic resin pellets or other
material granules through any reasonable size conduit. As a result,
the conveying system for the plastic resin pellets or other
granular material in a large facility is necessarily divided and
powered by three or four smaller blowers, resulting in three or
four different, separate systems for conveyance of plastic resin
pellets or other granular material. Sometimes several blowers are
connected to a single set of receivers, with one or more of the
extra blowers turning "on" only when required to furnish the
required extra cubic feet per minute of air flow. This is
controlled by a central station monitoring all receivers and all
blowers, with the central station being programmed to maintain all
of the hoppers associated with the process machines in a full
condition, wherever those hoppers are located throughout the
facility.
[0032] Even with careful planning and design, results achieved by
such pneumatic plastic resin pellet or other granular material
conveying systems are not consistent. Air flow speed and cubic feet
per minute capacity of blowers often vary and are outside of
selected design and specification values.
SUMMARY OF THE INVENTION
[0033] The instant invention provides an improvement to known
pneumatic plastic resin pellet and other granular material
conveying systems, reducing the costs of those systems while
providing consistent control of delivered cubic feet per minute of
air for individual receivers. The invention also facilitates easy
expansion of the pneumatic plastic resin pellet and other granular
material conveying system as the system grows. Such expandable
systems are made feasible by an air flow controller embodying
aspects of this invention.
[0034] In one aspect of this invention, air flow control limiters,
desirably of the type generally disclosed in U.S. Pat. No.
9,371,198, are added to each receiver so that the air pulled from
any single receiver is limited to the correct predetermined,
preselected flow rate. This prevents excessive flow rates and
"open" lines that dump too much air into the system.
[0035] Use of these air flow limiters allow one large pump to be
used without risk to the system or to the resin or other granules
being conveyed. An added advantage of a very large pump is that it
can fill multiple receivers simultaneously with resin or other
granular material. As used herein, the term "receiver" denotes the
type of apparatus disclosed in U.S. Pat. Nos. 6,089,794; 7,066,689,
and 8,753,432. The disclosures of these patents are hereby
incorporated by reference.
[0036] The invention allows receivers to "load" the resin or other
granular material the instant there is demand for material by
dropping or otherwise supplying the material, usually downwardly,
into a gravimetric blender or directly into a process machine. The
receiver need not wait in the "queue" to load because no sequencing
of the receivers is required. Each receiver is always "ready to
go."
[0037] A central control station is not required, and neither is
wiring from each receiver to a central control station, thus
further reducing costs.
[0038] Consequently, in this invention as implemented in one of its
embodiments, there are one or several large vacuum pumps, with
receivers that stand alone without need for a central control, and
an air flow limiter on each receiver to assure proper and constant
flow rate.
[0039] This invention facilitates periodically reducing the speed
of the vacuum pump, to hold the desired vacuum level in the lines.
This is in contrast to running the vacuum pump at full speed all
the time.
[0040] "CFM" is a term referring to a cubic foot of air regardless
of the density of the air. "SCFM" refers to a cubic foot of air at
standard temperature and pressure, namely 70.degree. F. at sea
level. The air flow limiter holds SCFM constant. This means that
air flow through the air flow limiter will be faster when the air
is thin, such as at high altitudes, and slower when the air is
thick, such as at sea-level. However, in both cases (or any case),
the air flow limiter maintains SCFM, namely air flow in standard
cubic feet per minute, constant. Stated differently, so long as the
SCFM is held steady, as is the case with the air flow limiter
disclosed herein, the same weight of air, or number of air
molecules, flows through the limiter regardless of conditions. Air
flow rate through the limiter may change in terms of the speed of
the air, but in all cases, the quantity of air flowing, measured in
standard cubic feet per minute, is constant.
[0041] In another embodiment of the invention one air flow limiter,
as disclosed in the instant application, is in place as a single
air flow limiter at the vacuum pump suction inlet with the vacuum
pump being connected to a plurality of receivers all connected in a
system. This provides a selected, correct rate of air flow in
standard cubic feet per minute. In this embodiment of the
invention, only a single air flow limiter is used at the vacuum
pump inlet, as opposed to the alternative embodiment of the
invention described above where one air flow limiter is used at
each receiver.
[0042] An advantage of using only a single air flow limiter of the
type disclosed herein is that the vacuum pump can be sized and
operated for the longest distance over which resin or other
granular material is to be conveyed in a given locale. This can be
done while still protecting shorter runs of the system from
excessive granular material velocity, where less vacuum is
required. One air flow limiter costs less than having an air flow
limiter located at every receiver; this provides an advantageous
aspect to this embodiment of the invention.
[0043] By adding an air flow limiter manifesting aspects of this
invention to every receiver, control of air flow in cubic feet per
minute can be maintained at a constant value that is ideal for that
particular receiver, considering conduit diameter and distance over
which the plastic resin pellets or other granular material must be
conveyed through the associated conduit. Alternatively, by adding
an air flow limiter just to the suction inlet of the vacuum pump,
one can control air flow in cubic feet per minute to a constant
value that is ideal for the system as a whole, considering conduit
diameter and distance over which the plastic resin pellets or other
granular material must be conveyed to the multiple receivers in the
system.
[0044] Use of the air flow limiter allows pneumatic plastic resin
pellet or other granular material conveying systems to utilize a
single large high horsepower vacuum pump. In accordance with one
embodiment of the invention, each receiver in a facility is fitted
with an air flow limiter embodying the invention so the flow for
each receiver in cubic feet per minute is self-limiting. This
approach eliminates the need to match vacuum pumps or blowers to a
specific material conduit size or conveyance distance. Using this
approach, the flow limiter permits operators to run a very large
vacuum pump or blower at a speed that will maintain a desired high
level of vacuum throughout the entire vacuum (or pneumatic) plastic
resin pellet or other granular material conveying system.
[0045] Using larger than standard diameter vacuum conduits allows a
significant vacuum reserve to exist in the plastic resin pellet or
other granular material conveying system, without the need for a
vacuum reserve tank. Larger diameter conduits also mean there is
little loss of vacuum over long distances, even at the most distant
receiver to which plastic resin pellets or other material granules
are supplied by the system. A variable frequency drive control may
be used to adjust the speed of the vacuum pump to maintain air flow
at the desired standard cubic feet per minute rate through the air
flow limiter.
[0046] With the flow regulator facilitating use of high horsepower
vacuum pumps or blowers, designers can now design to load multiple
receivers at the same time without fear of dropping vacuum levels
too low in portions of the pneumatic or vacuum plastic resin pellet
or other granular material conveying system.
[0047] In the plastic resin pellet or other granular material
conveying system aspect of the invention, no central control system
is required. Using the flow limiter of the invention, each receiver
controls its own operation and is not wired to any central control
facility. When the level of plastic resin pellets or other material
granules in the hopper of a process machine falls to a sufficiently
low level, a level sensor tells the receiver to load the hopper of
the process machine. Coupled to the level sensor may be a vacuum
sensor, which confirms that the main system has sufficient vacuum
available to load the receiver. If too many other receivers are
currently loading, and the vacuum level is sensed to be below the
threshold for effective loading, then the receiver associated with
the sensor will wait until vacuum readings rise. When available
system vacuum is sufficient to assure adequate flow of plastic
resin pellets or other material granules into a given receiver, the
vacuum sensor causes a vacuum valve associated with the receiver to
open the connection of the receiver to the conduit carrying the
plastic resin pellets or other granular material, and the receiver
fills with resin pellets.
[0048] In accordance with one aspect of the invention, each
receiver acts on its own sensed information. Use of the high
horsepower vacuum pump means that several receivers can load
simultaneously.
[0049] The air flow limiter does several things to make such
systems in accordance with the invention possible. By limiting
cubic feet per minute of flow to the desired constant level, there
is virtually no limit on the horsepower of the vacuum pump. The
risk of a too high a conveyance speed of the plastic resin pellets
or other material granules through the conduit is eliminated.
Additionally, if a receiver is not drawing in plastic resin pellets
or other granular material but is just drawing air as a result of
the main supply of plastic resin pellets or other material granules
being exhausted, the empty conduit of the conveying system would
ordinarily convey a substantial amount of air, which normally would
drop the vacuum reserve of the entire pneumatic conveying system
very rapidly. But with the flow limiter such dumping of air into
the conveying conduit is at least substantially reduced, and if the
flow limiter is at the suction intake of the vacuum pump, such
dumping of air into the system is essentially impossible.
[0050] Further contributing to minimized air dump into the vacuum
conduit is the receiver's ability to detect system failure or
absence of material being loaded, thereby stopping further load
cycles and sounding an alarm.
[0051] The air flow limiter preferably has but a single moving
part, a valve, which relies on two opposing forces, namely gravity
in one direction and "lift" created by air flow in the opposite
direction. Because the air flow limiter uses gravity to close the
valve portion of the regulator, orientation of the air flow limiter
is important. Air flow must be upward, essentially or at least
largely vertically through the air flow limiter, to counter the
downward force of gravity.
[0052] The air flow limiter is desirably in the form of a tube with
an air flow actuated valve within the tube. In a "no flow"
condition, gravity holds the valve closed. However, as air flow
through the limiter reaches a pre-selected design value, air
flowing over and against a sail-like plate lifts an internal free
floating valve. This shuts off air flow through the air flow
limiter if the free floating valve rises sufficiently to contact a
stop located within the tube.
[0053] By adjusting the size and/or shape of the "sail", and the
weight of the free floating valve, desired air flow in standard
feet per minute can be regulated very closely. Gravity as a force
in one direction means the opening force is constant over the full
range of motion of the valve device. (A spring, if one were used,
would provide a variable force. However, use of gravity in the air
flow limiter eliminates that variable).
[0054] In the air flow limiter, at the desired design standard
cubic feet per minute of air flow, the valve opens as air lifts it.
The valve would continue moving upwardly except for the fact that
the valve reaches a point of air flow restriction where the valve
holds air flow steady at the desired design value. If the valve
moves further upwardly towards a "closed" position, this reduces
air flow and the resulting force on the valve, causing the valve to
drop in response to gravity. If the valve drops below the control
level, this allows more air flow and consequently the valve rises
as the air pushes the valve upwardly. As a result, the valve
reaches the desired design valve equilibrium control point
essentially instantly and very accurately. Usually the length of
the short tube is less than the diameter of the short tube.
Desirably the length of travel of the short tube is no more than
one half the length of the short tube.
[0055] Known air flow shutoffs are subject to "vacuum pull",
causing them to shut off completely once air begins to flow. This
is because in known shutoffs, vacuum "pull" of the vacuum pump is
always present. In the air flow limiter preferably used herein, a
short vertical tube closes against a flat horizontal surface. In
this air flow limiter, air flow is preferably directed through the
center of the short tube and preferably escapes over the top edge
of the short tube and preferably then around open edges of a flat
shutoff surface. A flat, desirably triangular or star-shaped plate
is preferably positioned in the air flow below and preferably
connected to the short tube. This plate acts as a sail in the air
flow and will, at the designed desired standard cubic feet per
minute air flow rate, provide enough lift to raise the short tube
against the shutoff plate.
[0056] At shut off, with vacuum above the flat shutoff surface and
air at some pressure below the flat shutoff surface, most of the
air pressure forces are against the walls of the short tube. Those
forces are radially outwardly directed. Specifically, they are
horizontal due to the configuration of the air flow limiter, and do
not exert significant vertical force that would make the movable
portion of the valve, namely the short tube, move in a vertical
direction.
[0057] The surface of the end of the short tube, at the short tube
end edge, is a horizontal surface and can provide a small vertical
force when air travelling upwards impinges on the surface. For this
reason, the air flow limiter aspect of the invention uses a very
thin wall short tube, to minimize the vertically projected,
horizontal surface area of the short tube.
[0058] In the air flow limiter preferably used herein, air flow
rate in cubic feet per minute can be adjusted by adding or
subtracting weight from the floating valve, or by adjusting the
surface area of the sail, or by adjusting the size or shape of the
sail in the air flow.
[0059] Accordingly, in one of its aspects, the invention provides a
resin delivery system and method that includes an air flow limiter
preferably having a vertically oriented tube, a pair of open-ended
telescoping tubular internal segments within the tube, with an
outer tubular segment preferably being fixed and the other
preferably being slidably moveable along the fixed segment in the
axial direction. The air flow limiter preferably further includes a
plate extending partially across the interior of the vertically
oriented tube and positioned for contacting the moveable one of the
desirably telescoping tubular segments and limiting travel of the
moveable telescoping tubular segment, with the plate covering the
upper, open end of the moveable desirably telescoping tubular
segment upon contact therewith. In this aspect, the invention yet
further preferably includes a sail positioned in the vertically
oriented tube below the telescoping segments, a strut connecting
the sail and the moveable telescoping tubular segment, and a baffle
positioned to direct upward air flow within the tube through the
desirably telescoping tubular segments. The moveable desirably
telescoping tubular segment moves vertically within the tube,
unitarily with the sail, responsively to air flowing upwardly
through the tube against the sail.
[0060] The tubular segments are preferably cylindrical; the surface
of the plate contacted by the moveable tubular segment is
preferably planar; and the portion of the moveable tubular segment
contacting the plate surface is preferably annular.
[0061] In a variation of terminology, a surface of the plate
contacted by the moveable tubular segment is flat, the tubular
segments are cylindrical and the circular edge of the tubular
segment contacting the plate surface is annular and normal to the
axis of the tubular segment.
[0062] In yet another one of its aspects, this invention provides a
granular material delivery system having at least one air flow
limiter consisting of a vertically oriented tube, a tubular segment
within the tube, which segment is moveable in the axial direction,
a plate extending at least partially across the interior of the
tube for contacting the movable tubular segment and defining a
limit of travel of the moveable tubular segment, a sail positioned
in the tube below the moveable tubular segment and being moveable
vertically within the tube, a strut connecting the tubular segment
and the sail, and a baffle connected to and located within the tube
defining a lower limit of travel of the moveable tubular segment
upon contact of the strut with an upper extremity of the baffle.
The moveable tubular segment is in sliding, desirably telescoping
engagement with the tubular portion of the baffle, directing upward
air flow within the tube, with the moveable tubular segment being
moveable unitarily with the sail in response to upward air flow
through the tube contacting the sail.
[0063] In yet another one of its aspects, this invention provides a
granular material delivery system that includes at least one air
flow regulator having a vertically oriented tube with a sail
assembly positioned in the tube and moveable therewithin
responsively to air flow through the tube to regulate air flow
through the tube and to stop air flow thorough the tube upon air
flow exceeding a preselected value expressed in standard cubic feet
per minute.
[0064] In yet another one of its aspects, this invention provides a
method for conveying granular plastic resin or other granular
material by controlled air flow where air flow control involves the
steps of providing a vertically oriented tube, positioning a
moveable sail assembly including a sail within the tube,
positioning a stop within the tube, and permitting the sail
assembly to move responsively to air flow through the tube between
a position at which air flows around the sail assembly and through
the tube, and a position at which the sail assembly contacts the
stop and blocks air flow through the tube.
[0065] In yet another one of its aspects, this invention provides a
pneumatic granular material delivery system utilizing air flow
regulating apparatus including a preferably substantially
vertically oriented first tube, a preferably substantially
vertically oriented second tube which is moveable along and within
the first tube, a baffle within the first tube for forcing air flow
in the first tube through the second tube, a guide within the first
tube for limiting the second tube to preferably substantially
vertical co-axial movement within and relative to the first tube, a
sail within the first tube being connected to the second tube and
being moveable responsively to air flow within the first tube, and
a stop within and connected to the first tube for limiting upward
travel of the second tube.
[0066] In still another one of its aspects, this invention provides
apparatus for conveying granular plastic resin or other granular
material from a supply preferably to receivers that retain and
dispense the resin or other material granules when needed by a
process machine, where the apparatus preferably includes a vacuum
pump, a single air flow limiter preferably connected to a suction
head of the vacuum pump, a first conduit preferably connecting the
receivers to the air flow limiter, and a second conduit preferably
connecting the granular material supply to the receivers. In this
embodiment of apparatus of the invention, suction created by
operation of the vacuum pump preferably draws granular plastic
resin or other material granules from the supply into the receivers
through the second conduit and preferably draws air from the second
conduit through the receivers, the first conduit and the air flow
limiter. The air flow limiter is preferably oriented substantially
in a vertical direction for substantially vertical flow of air
substantially upwardly therethrough.
[0067] In yet still another aspect, this invention provides
apparatus for conveying granular plastic resin material or other
granular material from a supply of granular material to receivers
that retain and dispense the resin or other granular material when
needed by a process machine, where the apparatus preferably
includes a vacuum pump, air flow limiters connected to outlets of
the receivers, with the air flow limiters preferably being
vertically oriented for vertical flow of air drawn by suction
therethrough, a first conduit connecting the air flow limiters to a
suction head of the vacuum pump and a second conduit connecting the
granular material or supply to the receivers. In this apparatus
aspect of the invention, suction created by operation of the vacuum
pump preferably draws granular plastic resin or other material
granules from the supply of granular material into the receivers
through the second conduit, and also preferably draws air from the
second conduit through the receivers, the air limiters, and the
first conduit. In this second embodiment, at least one of the air
flow limiters preferably consists of a tube, a tubular segment
within the tube that is moveable in the axial vertical direction, a
plate extending at least partially across the interior of the tube
for contacting the moveable tubular segment and defining a limit of
vertical travel of the moveable tubular segment, a sail connected
to the moveable tubular segment and being moveable therewith within
the tube, and a baffle connected to and within the tube defining a
second limit of vertical travel of the moveable tubular segment,
where the moveable tubular segment is in sliding, telescoping
engagement with the tubular portion of the baffle and the baffle
directs air flow within the tube into the tubular segment. The
moveable tubular segment moves unitarily with the sail in response
to vertical air flow through the tube contacting the sail.
[0068] While the foregoing summarizes the invention and the manner
of practicing it in a manner that one of skill in the art can
practice the invention, it is to be understood that the foregoing
summary of the invention is only a summary and that the invention
has aspects broader than those recited. The invention may be
implemented in embodiments other than those disclosed herein and
may be practiced using apparatus other than that disclosed herein.
It is further to be understood that the drawings are attached for
purposes of explanation only and that one of skill in the art, upon
reading the foregoing description and summary of the invention and
looking at the drawings, might contemplate alternate means of
practice of the invention. All of such alternate means are deemed
to be within the scope of the invention so long as those alternate
means achieve essentially the same result in essentially the same
way as the invention and are functionally related to the function
of this invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0069] FIG. 1 is a schematic representation of a resin or other
granular material delivery system with a single air flow regulator
in accordance with aspects of the invention.
[0070] FIG. 2 is a schematic representation of a resin or other
granular material delivery system with a plurality of air flow
regulators in accordance with aspects of this invention.
[0071] FIG. 3 is an isometric view of the exterior of an air flow
limiter portion of apparatus for pneumatically conveying granular
plastic resin or other material granules in accordance with aspects
of the invention.
[0072] FIG. 4 is a front elevation of the air flow limiter
illustrated in FIG. 3.
[0073] FIG. 5 is an isometric sectional view of the air flow
limiter illustrated in FIGS. 3 and 4, with the section taken at
arrows 3-3 in FIG. 4.
[0074] FIG. 6 is a sectional view in elevation of the air flow
limiter illustrated in FIGS. 3 and 5, with the section taken at
lines and arrows 3-3 in FIG. 4, with air flow through the air flow
limiter being depicted in FIG. 6 by curved dark arrows.
[0075] FIG. 7 is a sectional view in elevation similar to FIG. 6
but with the air flow limiter internal parts in position whereby
there is no air entering the air flow limiter and hence there is no
air flow upwardly through the air flow limiter, in contrast to such
air flow being shown in FIG. 6.
[0076] FIG. 8 is a sectional view in elevation similar to FIGS. 6
and 7 but with the air flow limiter internal parts in position
where there is an excessive amount of air attempting to enter the
air flow limiter but there is no air flow upwardly through the air
flow limiter due to the air flow limiter valve having moved to
block air flow upwardly through the air flow limiter, in contrast
to upward air flow through the air flow limiter as shown in FIG.
4.
[0077] FIG. 9 is an exploded isometric view of the air flow limiter
illustrated in FIGS. 3 through 8.
[0078] FIG. 10 is an isometric view of the movable portion of the
air flow limiter illustrated in FIGS. 3 through 9.
[0079] FIG. 11 is a sectional view of the air flow limiter similar
to FIGS. 6, 7 and 8, illustrating an alternate construction of the
baffle portion of the air flow limiter.
[0080] FIG. 12 is sectional view of the air flow limiter similar to
FIGS. 6, 7, and 11, illustrating a second alternate construction of
the baffle portion of the air flow limiter.
DETAILED DESCRIPTION OF THE OF THE INVENTION
[0081] In this application, unless otherwise apparent from the
context it is to be understood that the use of the term "vacuum"
means "air at slightly below atmospheric pressure." The vacuum
(meaning air slightly below atmospheric pressure) provides a
suction effect that is used to draw granular plastic resin or other
granular material out of a supply and to convey that resin or other
granular material through various conduits to receivers where the
resin or other granular material can be temporarily stored before
being molded, extruded, or otherwise processed. Hence, in this
application it is useful for the reader mentally to equate the term
"vacuum" with the term "suction".
[0082] Referring to the drawings in general and to FIG. 1 in
particular, apparatus for conveying granular plastic resin material
or other granular material from the supply to receivers that retain
and dispense the resin or other material granules when needed by a
process machine is illustrated in FIG. 1. The apparatus, which is
designated generally 88 in FIG. 1, preferably includes a vacuum
pump designated generally 92 and shown schematically in FIG. 1. The
vacuum pump preferably includes a vacuum pump suction head 93 also
shown schematically in
[0083] FIG. 1. Connected to the vacuum pump suction head 93 is an
airflow limiter 30 shown only in schematic form in FIG. 1, but
shown in detail in FIGS. 3 through 12. Airflow limiter 30 receives
vacuum drawn by vacuum pump 92 through vacuum drawing conduit
100.
[0084] Vacuum drawing conduit 100 is connected to a plurality of
receivers 16, each of which receives, retains and dispenses, as
needed, granular plastic resin material or other granular material
to a process machine, such as a granulator, a blender, an extruder,
or a molding press, as located preferably below a receiver 16. The
process machines are not illustrated in FIG. 1 to enhance the
clarity of the drawing.
[0085] Further illustrated in FIG. 1 is a hopper 18 for storage of
granular plastic resin material or other granular materials therein
and a resin conveying conduit 98, which serves to draw resin from
hopper 18 and to deliver the granular material through resin
conveying conduit 98 to the respective receivers as vacuum is drawn
by the vacuum pump, with vacuum propagating through air flow
limiter 30, vacuum drawing conduit 100, the various receivers 16,
and resin conveying conduit 98, back to hopper 18.
[0086] FIG. 2 shows an alternate embodiment of the granular
material conveying system where this alternate embodiment of the
conveying system has been designated 88A. FIG. 2, as in FIG. 1,
depicts a vacuum pump 92 shown in schematic form having a vacuum
pump suction head 93 also depicted in schematic form. In the
alternate embodiment illustrated in FIG. 2, vacuum drawing conduit
100 leads directly into and communicates with vacuum pump suction
head 93. In the embodiment illustrated in FIG. 2, an air flow
limiter 30 is provided for each receiver 16, with the air flow
limiter 30 for a respective receiver 16 being located in a portion
of a connection conduit 102 that connects a respective receiver to
vacuum drawing conduit 100. In FIG. 2, each air flow limiter 30 is
depicted in a vertical orientation, just as airflow limiter 30 is
depicted in a vertical orientation in FIG. 1. Each receiver is
connected by connection conduit 102 to vacuum drawing conduit 100
with air flow limiter 30 preferably forming a portion of connection
conduit 102.
[0087] In FIG. 2, as in FIG. 1, a first conduit 98 serves to convey
granular plastic resin or other material granules from hopper 18 to
the respective receivers in response to vacuum drawn by vacuum pump
92 as that vacuum propagates from vacuum pump 92 through second
conduit 100, connection conduits 102, receivers 16, and granular
material conveying conduit 98, to hopper 18.
[0088] During operation of the granular material conveying systems
shown schematically in FIGS. 1 and 2, upon actuation of vacuum pump
92, a vacuum preferably is drawn at vacuum pump suction head 93.
This vacuum, as it propagates back to hopper 18, serves to draw
granular material out of hopper 18 and into the respective
receivers 16. In the embodiment illustrated in FIG. 2, individual
air flow limiters 30 limit the suction or vacuum drawn by vacuum
pump 92 through a given associated receiver 16. In the embodiment
illustrated in FIG. 1, a single air flow limiter 30 limits the
vacuum drawn through all of receivers 16 forming a portion of the
granular resin or other granular material conveying system
illustrated in FIG. 1.
[0089] Referring to FIGS. 1 and 2, the air flow limiter 30 portion
of the granular material delivery system is preferably in the
general form of a substantially vertically oriented tube,
preferably having inlet and outlet ends 54, 56 respectively. The
preferably tubular character of air flow limiter 30 is apparent
from FIGS. 3 through 8, where air flow limiter 30 preferably
includes a vertically oriented exterior tube 32, with open-end caps
58, 60 defining and providing open inlet and outlet ends 54, 56
respectively. End caps 58, 60 are open, preferably of generally
cylindrical configuration, and are configured to fit closely about
vertically oriented tube 32 so as to provide a substantially air
tight fit between end caps 54, 56 and tube 32.
[0090] As illustrated in FIG. 5, air flow limiter 30 preferably
includes, within vertically oriented exterior tube 32, a
horizontally positioned plate 46, which is oriented perpendicularly
to the axis of tube 32. Plate 46 is preferably configured as a
circular disk of lesser diameter than the inner diameter of
vertically oriented tube 32, with plate 46 further preferably
including three legs extending outwardly from the circular interior
disk portion of plate 46. Legs of plate 46 are designated 62 in
FIG. 9, while the circular interior portion of plate 46 is
designated 64 in FIG. 9. Plate 46 is secured to the interior of
vertically oriented outer tube 32 by attachment of legs 62 to the
interior surface of tube 32. Any suitable means of attachment, such
as by welding, adhesive, mechanical screws, or end portions of legs
62 defining tabs fitting into slots within tube 32 as shown in FIG.
5, may be used.
[0091] As best shown in FIGS. 5, 6, and 7, a baffle 52 is
positioned within vertically oriented outer tube 32, below plate
46. Baffle 52 has a lower conical portion 66 and an upper
cylindrical portion 44, with cylindrical portion 44 defining a
fixed internal tubular segment of air flow limiter 30. Baffle 52 is
preferably retained in position by a pair of screws designated 68,
70 respectively. Baffle 52 preferably rests on screw 68. Screw 70
preferably fits against the fixed internal tubular segment 44
portion of baffle 52 to secure baffle 52 in position within
vertically oriented external tube 32. Lateral force applied by
screw 70 in a direction perpendicular to the axis of vertically
oriented external tube 32, with screw 70 in contact with fixed
internal tubular segment 44, serves to effectively retain baffle 52
against movement within vertically oriented external tube 32.
[0092] The upper portion of baffle 52, defining fixed internal
tubular segment 44, is adapted for sliding, preferably telescopic
engagement with and movement therealong by movable tubular segment
42. Fixed to movable tubular segment 42 is a first strut 48
preferably extending transversally across the upper portion of
movable tubular segment 42 and preferably secured at either end to
movable tubular segment 42, as illustrated in FIG. 10. Preferably
extending downwardly from first strut 48 is a second strut 50,
preferably secured to first strut 48 and preferably also to a sail
34, as illustrated in FIG. 10 and in FIGS. 5, 6, 7, 8 and 9.
[0093] Movable sail 34 is preferably planar and positioned fixedly
on second strut 50 to remain perpendicular with respect to the axis
of vertically oriented outer tube 32. Movable sail 34 is preferably
of generally triangular configuration, as best illustrated in FIGS.
9 and 10, with the sides of the triangle curving slightly inwardly.
The curved edges 72 of movable sail 34 converge and terminate to
form small rectangularly shaped extremities of sail 34, which are
designated 76 in FIG. 9.
[0094] Movable sail 34 is positioned within generally vertically
oriented outer tube 32 so that rectangular extremities 76 are
closely adjacent to but do not contact the inner surface of
preferably vertically oriented outer tube 32, so long as sail 34
moves vertically up and down within preferably vertically oriented
external tube 32. The rectangular shape of extremities 76 with
their outwardly facing preferably planar surface assures minimal
friction and consequent minimal resistance to movement of movable
sail 34 in the event one of rectangular extremities 76 contacts the
interior surface of vertically oriented tube 32, should sail 34 for
some reason move laterally, or otherwise, and become skew to the
vertical axis of tube 32.
[0095] Movable internal tubular segment 42 is telescopically
movable, unitarily with sail 34, relative to and along fixed
internal tubular segment 44. A lower limit of movement of movable
tubular segment 42 is illustrated in FIG. 7, where the first strut
portion 48 of movable tubular segment 42 (shown in FIG. 10) rests
on the upper circular edge of fixed internal tubular segment 44.
This is the condition when no air is flowing or drawn through the
air flow limiter 30 and gravity causes sail 34 together with
movable internal tubular segment 42 to drop, with first strut 48
coming to rest on the upper circular edge of fixed tubular segment
44.
[0096] When air is flowing through air flow limiter 30, as
illustrated generally in FIG. 6, the moving air pushes against
movable sail 34, moving it upwardly. Movable internal tubular
segment 42 moves upwardly unitarily with sail 34 due to the fixed
connection of movable tubular segment 42 and movable sail 34 made
via first and second struts 48, 50, as illustrated in FIGS. 5, 6,
7, 9, and 10.
[0097] If air flow upwardly through air flow limiter 30 reaches an
extreme level, above an acceptable level of operation of the
granular material delivery system of which air flow limiter 30 is a
part, the excessive force (resulting from the high volume of air
flow contacting sail 34) pushes sail 34 upwardly to the point that
upper annular edge 78 of movable internal tubular segment 42
contacts plate 46. In this condition, which is illustrated in FIG.
8, no air can pass between the upper annular edge 78 of movable
tubular segment 42 and flow limiting horizontal plate 46, and air
flow stops.
[0098] Once air flow stops through vertically oriented outer tube
32, gravity pulling downwardly on sail 34, connected movable
internal tubular segment 42, and connected first and second struts
48, 50, causes these parts, which may preferably be fabricated
together as a single integral assembly as shown in FIG. 8, to move
downwardly, thereby again permitting air flow upwardly through air
flow limiter 30 as depicted generally in FIG. 6. Consequently, air
flow limiter 30 is self-regulating in that when air flow is too
high, the force of air moving or impinging on sail 34 pushes
movable internal tubular segment 42 upwardly until upper annular
edge 78 of movable tubular segment 42 contacts plate 46 and no air
can then escape upwardly between the upper annular edge 78 of
movable tubular segment 42 and plate 46. This stops air flow
through flow limiter 30 until downward movement of sail 34 together
with movable internal tubular segment 42 moves upper annular edge
78 of movable tubular segment 42 away from plate 46, again
permitting air to flow through the upper extremity of movable
tubular segment 42, with air passing between upper annular edge 78
of movable internal tubular segment 42 and flow limiting horizontal
plate 46, and then escaping through upper outlet end 56 of air flow
limiter 30.
[0099] With the self-regulating characteristic of air flow limiter
30, the assembly consisting of movable internal tubular segment 42,
first and second struts 48, 50 and sail 34 may oscillate somewhat
about the position at which air flow drawn by suction is at the
desired level, as the speed of the vacuum pump drawing air through
flow limiter 30 varies, and hence the flow varies in cubic feet per
minute of air drawn.
[0100] Desirably, ends of first strut 48, which is depicted as
being horizontally disposed in the drawings, are mounted in movable
tubular segment 42 in movable fashion such that first strut 48 can
move slightly, rotationally, relative to movable internal segment
42. This is to provide a small amount of "play" in the event
movable sail 34 and second strut 50, which is vertically oriented
and connected to movable sail 34, become skew with respect to the
vertical axis of vertically oriented exterior tube 32. Should this
occur, the movable characteristic of first strut 48, being slightly
rotatable relative to movable internal tubular segment 42,
effectively precludes movable internal tubular segment 42 from
binding with respect to fixed internal tubular segment 44 and
thereby being restricted from what would otherwise be freely
telescoping movement of movable internal tubular segment 42
relative to fixed internal tubular segment 44.
[0101] Desirably first strut 48 is rotatable relative to movable
internal tubular segment 42, to provide maximum freedom of vertical
motion of movable internal tubular segment 42 in the event movable
sail 34 becomes skew to the axis of vertically oriented exterior
tube 32, with consequent frictional force restricting vertical
movement of movable sail 34.
[0102] Baffle 52 preferably includes two portions, the upper
portion preferably being defined by fixed internal tubular segment
44 and a lower portion preferably being defined by conical portion
66 of baffle 52. A lower edge of baffle 52 is circular and is
designated 84 in the drawings. Circular edge 84 fits closely
against the annular interior wall of vertically oriented exterior
tube 32 so that all air passing upwardly through air flow limiter
30, namely through preferably vertically oriented exterior tube 32,
is constrained to flow through the interior of baffle 52. The tight
fitting of the circular lower edge of baffle 52 against the
interior wall of vertically oriented exterior tube 32 forces all
air entering flow limiter 30 from the bottom to flow through the
interior of baffle 52, flowing upwardly through lower conical
portion 66 of baffle 52.
[0103] The air then flows further upwardly through the interior of
fixed internal tubular segment 44. Thereafter, if movable internal
tubular segment 42 is spaced away from flow limiting horizontal
plate 46, air flows along the surface of movable internal tubular
segment 42, passing the upper annular edge 78 of movable internal
tubular segment 42; air then flows around the space between edge 82
of flow limiting horizontal plate 46 and the interior annular wall
of vertically oriented exterior tube 32. The air then flows out of
air flow limiter 30 via open outlet end 56 formed in end cap
60.
[0104] In an alternate embodiment of the air flow limiter, baffle
52 may be constructed from two pieces that fit closely together,
with the two pieces being in facing contact in the area where they
define fixed internal tubular segment 44, but diverging one from
another in the area where they define conical portion 66 of baffle
52. As illustrated in FIG. 12, the two portions of baffle 52 are
designated "66A" and "66B" where they diverge, with baffle portion
66A serving to channel air flow upwardly through vertically
oriented exterior tube 32 into fixed internal tubular segment
portion 44 of baffle 52. The space between the lower parts of
baffle portions 66A and 66B is filled with a filler material 86 to
provide additional assurance that all air entering vertically
oriented exterior tube 32 from the bottom flows through fixed
internal tubular segment 44 and on through movable internal tubular
segment 42, and does not pass around the edge of baffle 52, namely
between baffle 52 and the interior surface of vertically oriented
exterior tube 32. Filler material 86 provides additional structural
rigidity for flow limiter 30.
[0105] In another alternative environment of the air flow limiter,
baffle 52 is one single piece, preferably molded plastic, as
illustrated in FIG. 11, where baffle 52 is designated 52B to
distinguish it from the baffle construction illustrated in FIG. 12
and the baffle construction illustrated in the other drawing
figures. In the baffle construction illustrated in FIG. 11, the one
piece construction means there is no need or space for any filler
material. The baffle construction illustrated in FIGS. 3 through 10
is preferred.
[0106] The assembly illustrated in FIG. 10 comprising the moveable
internal tubular segment 42, first strut 48, second strut 50 and
moveable sail 34 may preferably be constructed as a single piece or
several pieces as required. The assembly of moveable internal
segment 42, first and second struts, 48, 50 and moveable sail 34 is
referred to as a "sail assembly." It is not required that first and
second struts 48, 50 be separate pieces; they may preferably be
fabricated as a single piece. Additionally, second strut 50, which
has been illustrated as a machine screw in FIGS. 9 and 10, need not
be a machine screw. Any suitable structure can be used for second
strut 50 and it is particularly desirable to fabricate first and
second struts 48 and 50 from a single piece of plastic or metal, by
molding, by machining, or by welding, or by otherwise fastening two
pieces together. Similarly with the hex nut, which is unnumbered in
FIG. 10 and illustrated there, any other suitable means for
attachment of the second strut or a vertical portion of a strut
assembly to moveable sail 34 may be used.
[0107] Air flow limiter 30 preferably contains no springs. Air flow
limiter 30 preferably contains no sensors to provide feedback to a
control device; no sensors are needed because flow limiter 30 is
self-regulating. Air flow limiter 30 preferably includes a tubular
valve, closing against a flat surface, where the tubular valve is
defined by movable internal tubular segment 42 closing against flow
limiting horizontal plate 46. Movable internal tubular segment 42
is in the form of an open-ended cylinder and is connected to a
plate in the form of movable sail 34 to move movable tubular
segment 42 against flow limiting horizontal plate 46. Air flow
limiter 30 uses gravity alone to open the valve defined by the
assembly of movable internal tubular segment 42, movable sail 34,
and the connecting structure therebetween.
[0108] In the air flow limiter illustrated in FIGS. 3 through 12,
the movable internal tubular segment 42 is preferably made with a
very thin wall, preferably from metal tubing, where the wall is
preferably less than 1/32 inch in thickness.
[0109] Air flow limiter 30 functions equally well with a vacuum
pump drawing air through air flow limiter 30 from bottom to top by
application of vacuum to outlet end 56 as depicted generally in
FIGS. 1 and 2, or by air being supplied under positive pressure at
inlet end 54 for passage upwardly through air flow limiter 30.
[0110] While the invention and the modes of operation have been
described clearly and in more than sufficient detail that one of
skill in the art may practice the invention using the teachings of
the instant application, and while the claims appended hereto are
clear and concise and find full support in the foregoing
specification, the invention is not limited to the embodiments
described in the foregoing specification or to the literal language
of the appended claims. The invention further embraces components,
assemblies and methods not disclosed herein but which would perform
substantially the same function in substantially the same way to
achieve the same result as the apparatus and methods that are the
subject of the appended claims, all in accordance with the spirit
of the invention.
[0111] In the claims appended hereto, the term "comprising" is to
be understood as meaning "including, but not limited to" while the
phrase "consisting of" is to be understood a meaning "having only
and no more". The phrase "consisting essentially of" is to be
understood to mean the specified, recited elements, materials or
steps, as well as those that do not materially affect the basic and
novel characteristics of the claimed invention. See In re Herz, 537
F.2d 549; 190 USPQ 461 (CCPA 1976); 2111 Manual of Patent Examining
Procedure, Ninth Edition, Revision 07 2015, Last Revised Nov.
2015.
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