U.S. patent application number 13/752299 was filed with the patent office on 2013-08-15 for plant for the controlled-speed pneumatic transport of granular material and conveyance speed control process.
This patent application is currently assigned to MORETTO S.P.A.. The applicant listed for this patent is MORETTO SPA. Invention is credited to RENATO MORETTO.
Application Number | 20130209180 13/752299 |
Document ID | / |
Family ID | 39708399 |
Filed Date | 2013-08-15 |
United States Patent
Application |
20130209180 |
Kind Code |
A1 |
MORETTO; RENATO |
August 15, 2013 |
PLANT FOR THE CONTROLLED-SPEED PNEUMATIC TRANSPORT OF GRANULAR
MATERIAL AND CONVEYANCE SPEED CONTROL PROCESS
Abstract
The invention relates to a plant for the transport of granular
material comprising at least one container for granular material to
be transported, at least one receiver-meter group, at least one
conveyance duct, depressurization-pressurization means arranged to
suction/inject a gaseous medium from/into said at least one
container, and at least one vacuum duct between a receiver-meter
group and said depressurization-pressurization means, thereby
creating a flow of said granular material and said gaseous medium
in said at least one conveyance duct and a flow of gaseous medium
between said at least one receiver-meter group and said
depressurization-pressurization means.
Inventors: |
MORETTO; RENATO; (PADUA,
IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MORETTO SPA; |
|
|
US |
|
|
Assignee: |
MORETTO S.P.A.
Massanzago (Padua)
IT
|
Family ID: |
39708399 |
Appl. No.: |
13/752299 |
Filed: |
January 28, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12155996 |
Jun 12, 2008 |
8360691 |
|
|
13752299 |
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Current U.S.
Class: |
406/153 |
Current CPC
Class: |
B65G 53/66 20130101;
Y10T 137/0396 20150401; Y10T 137/86187 20150401; B65G 53/24
20130101 |
Class at
Publication: |
406/153 |
International
Class: |
B65G 53/24 20060101
B65G053/24 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 12, 2007 |
IT |
VR2007A000083 |
Claims
1. A plant for the transport of plastic granular material,
comprising: at least one container for plastic granular material to
be transported, at least one or more receiver-meters one or more
conveyance ducts each of which being in fluid connection with said
at least one container and said at least one or more receiver
meters, depressurization structure for creating a relative vacuum,
at least one vacuum duct in fluid connection with said
depressurization structure and said at least one or more
receiver-meters, each of said one or more conveyance ducts being in
fluid connection with said at least one vacuum duct through said at
least one or more receiver-meters, a speed detection structure
located in each of said vacuum ducts, an electronic speed detection
control with structure in communication with said speed detection
structure, said depressurization structure, and said at least one
or more receiver-meters, and a cleaning valve in fluid connection
with each of said conveyance ducts, wherein a flow of plastic
granular material from each of said containers can be individually
and automatically adjusted.
2. A plant according to claim 1, wherein said depressurization
structure comprises at least one rotatable component actuated by an
electric motor and a power adjusting structure having at least one
rotation speed variation device of at least one rotating component
of said depressurization structure.
3. A plant according to claim 2, wherein said power adjusting
structure comprises an inverter to vary the frequency of power
supply current to said electric motor in said depressurization
structure.
4. A plant according to claim 1, wherein said depressurization
structure comprises at least one vacuum pump.
5. A plant according to claim 1, wherein said speed detection
structure comprises measuring structure of air speed.
6. A plant according to claim 5, wherein said speed detection
structure comprises at least one flow rate meter.
7. A plant according to claim 1, comprising at least one reduced
pressure storage tank arranged upstream of at least one
depressurization structure and in fluid communication with at least
one vacuum duct of at least one receiver-meter.
8. A plant according to claim 7, comprising, downstream of said at
least one tank, at least one filtering structure through which
fluid suctioned from said at least one tank is caused to flow.
9. A plant according to claim 8, comprising: a differential
pressure meter structure arranged to measure possible load losses
due to obstruction of said at least one filtering structure and to
generate respective electrical signals to be sent to electronic
control unit.
10. A plant according to claim 9, comprising: a meter structure of
the fluid flow rate, a pressure meter structure to measure the
pressure in a respective vacuum duct and to send respective signals
to the input of said electronic control unit structure, and valve
structure arranged to maintain a correct reduced pressure or vacuum
level in a respective vacuum line as well as in a respective
receiver-meter.
11. A plant according to claim 1, comprising in each conveyance
line, a respective detection structure of the speed of the granular
material which moves inside its respective conveyance duct, said
detection structure being intended to send a signal to said
electronic control unit structure.
12. A plant according to claim 1, comprising a user interface video
unit and data insertion structure, said user interface being
intended to store, in said electronic control unit structure,
treatment parameters and characteristics related to the granular
material(s) to be treated.
13. A plant according to claim 1, wherein said electronic control
unit structure comprises a storage portion designed to store
characteristic data of the transport speed progression of specific
granular materials.
Description
FIELD OF INVENTION
[0001] The present invention regards a plant for the
controlled-speed pneumatic transport of granular material,
particularly but not exclusively suitable for the transport of
granular material made of plastic material, as well as a process
related thereto.
BACKGROUND OF INVENTION
[0002] With the terms "granules" or "granular", it is intended to
indicate in the present description and in the claims the small
scales, sheets or plates produced by the grinding-crushing of slab,
sheet, film and the like plastic material. In the plants for
working and/or transforming plastic materials reduced into
granules, granular material is transported from a storage container
to one or more machines designed to use such a material and usually
comprising injection or thermoforming presses, by means of a
pneumatic conveyance or transport system, preferably operating
under reduced pressure. The transport system must ensure a minimum
flow rate of granular material, thereby ensuring a continuous feed
of granular material to the transformation machine or machines.
[0003] In reduced-pressure transportation systems of granular
material proposed up to now, a vacuum source is provided, e.g. a
vacuum pump, arranged to suck air from a container of granular
plastic material. The granular material is thus driven by the
suctioned air along a suction tubing which leads above, and
discharges the granular material into, a collection tank, whereas
the transport air is suctioned to convey towards the vacuum source.
Between the collection tank of the granular material and the vacuum
source, a filter is provided to filter the air, which has just
separated from the bulk of the granular material, before it reaches
the vacuum source. An electronic control unit controls the entire
cycle. As a matter of fact, it is the atmospheric pressure that
pushes the granular material along the tubing towards the vacuum
source.
[0004] For a correct conveyance of the granular plastic material
within the ducts or tubing, the air flow created by the vacuum
source must flow within a desired speed range, both to prevent the
material from being conveyed at overly high speeds deemed
"dangerous", and to prevent the stagnation of the granular material
if the conveyance speed is not sufficiently high.
[0005] One of the most difficult problems to solve in the reduced
pressure transport of granular material within conveyance ducts is
that of being suitable for maintaining its transfer speed constant,
even with the change of light or section of the ducts and/or
configuration (curved, rectilinear) of the tubes along which the
conveyance is carried out.
[0006] In the conventional plants, and in particular along the
transport tubing, the speed of a granular material is usually not
maintained constant over time. In the various conveyance steps
carried out in a conventional reduced-pressure transport plant, the
conveyed plastic material granules usually reach very high speeds,
even double the optimum speed. When high speeds are reached,
plastic material granules scrape against the walls, especially at
the curved tubing sections, and due to the combined effect both of
the centrifugal force and the electrostatic charges and to the
friction they tend to adhere to the walls and to form thin film
encrustations or deposits on the walls themselves. Such deposits,
after a certain lapse of plant functioning time, are detached from
the tubing walls, giving rise to multilayer crusts or scales of
materials that are even different from each other, considering that
they are usually fed in different cycles through one same tubing.
The multilayer crusts or scales that are detached from the walls
constitute a source of pollution/contamination for the granular
materials that are conveyed along the tubing after their detachment
from the inner wall of the tubing itself. This phenomenon is called
"angel hair" formation in jargon.
SUMMARY OF THE INVENTION
[0007] The main object, therefore, of the present invention is that
of providing a plant for the reduced pressure transport of granular
material along tubing in optimal flow speed or intensity conditions
for the specific transported granular material, thus avoiding both
the formation of granular material on the walls of the tubing and
undesired stagnations of the granular material.
[0008] Another object of the present invention is to provide a
plant for the reduced pressure transport of granular material that
permits significantly reducing the operating costs with respect to
the conventional plants.
[0009] Another object of the present invention is that of providing
a process for transporting granular material that provide for
adapting the flow speed or intensity to the specific granular
material to be conveyed along the transport ducts.
[0010] According to a first aspect of the present invention, a
plant for the transport of granular material comprising at least
one container for at least one granular material to be transported,
at least one receiver-meter group designed to receive granular
material from said at least one container, at least one conveyance
duct of said granular material from said at least one container to
said at least one receiver-meter group,
depressurization-pressurization means arranged to suction/inject a
gaseous medium from/into said at least one container, and at least
one vacuum duct between said at least one receiver-meter group and
said depressurization-pressurization means, thereby creating a flow
of said granular material and said gaseous medium in said at least
one conveyance duct or line directed to said at least one
receiver-meter group and a flow of gaseous medium between said at
least one receiver-meter group and said
depressurization-pressurization means, said plant comprising
detection means of parameters of said flow located in said at least
one vacuum duct or line, adjusting means of the power of said
depressurization/pressurization means and electronic control means
designed to receive in input control signals from said speed
detection means and to emit control signals in output for driving
said adjusting means.
[0011] According to another aspect of the present invention, a
conveyance speed control process is provided of a granular material
along at least one conveyance line between at least one container
of the granular material to be conveyed and at least one
receiver-meter group of the same comprising: [0012] the application
of a depressurization-pressurization to said granular material
through at least one conveyance duct extending between said at
least one container and said at least one receiver-meter group and
through said at least one vacuum line or duct, whereby
suctioning/injecting a gaseous medium from/into said at least one
container and to create a flow of said granular material and said
gaseous medium along said at least one conveyance duct directed to
said at least one receiver-meter group and a flow of gaseous medium
between said at least one receiver-meter group and
depressurization-pressurization means, comprising: [0013] detecting
parameters of said gaseous flow in said at least one vacuum line or
duct, and [0014] adjusting said flow by varying the
depressurizing-pressurizing power of said
depressurization-pressurization means as a function of the detected
parameters of said flow.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Further aspects and advantages of the present invention will
be clearer from the following detailed description of several
currently preferred embodiments of a reduced-pressure granular
material transport plant, illustrated as indicative and
non-limiting examples in the accompanying drawings, in which:
[0016] FIG. 1 is a schematic front elevation view of a conventional
reduced pressure transport plant;
[0017] FIG. 2 illustrates an enlarged scale detail of the plant of
FIG. 1 in a first operating position;
[0018] FIG. 3 shows the detail of FIG. 2 in a second operating
position;
[0019] FIG. 4 is a diagrammatic view of a centralized
reduced-pressure transport plant of granular material from several
granular material sources and the same number of transforming
machines of the same material;
[0020] FIG. 5 shows a partial, schematic view on an enlarged scale
of a cleaning device of the granular material conveyance ducts
provided in the plant of FIG. 4;
[0021] FIG. 6 illustrates a centralized reduced pressure transport
plant of granular material from several granular material sources
and the same number of transforming machines, the plant being
provided with a set of cleaning devices as illustrated FIG. 5;
and
[0022] FIG. 7 illustrates a schematic view of a further embodiment
of a reduced pressure transport plant of granular material
according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] With reference first to FIGS. 1 to 3, it will be noted that
a conventional reduced pressure transport plant of granular
material comprises a container 1 of any suitable type containing a
specific amount of granular material 1a to be transported, a
fluidizing lance member 2 drawing in granular material 1a, e.g.
formed by a substantially rigid tube, intended to capture material
granules and mix them with air, as will be further described below.
The lance member 2 is in fluid communication with one end of a tube
or hose 3, which can be of both rigid and flexible type and whose
other end penetrates in an intermediate portion of a
hermetically-sealed receiver-meter device 4 and defines a discharge
mouth 3a.
[0024] Within the receiver-meter device 4, at a lower level than
that of the discharge mouth 3a, a small metering hopper 33 is
provided equipped with lower discharge mouth that can be opened and
closed by a bottom flap 34 supported by a projecting arm 15 in turn
pivoted at 35 to the hopper, thereby being arranged to oscillate
about a horizontal axis. The discharge mouth is illustrated closed
in FIG. 2, while in FIG. 3 it is open, in order to discharge
granular material 1a conveyed and collected in the metering hopper
33 into an underlying hopper 13 set to act as a feed storage of
plastic granular material 1a for a transformer machine generally
indicated with M.
[0025] The rotatable equipment formed by the bottom flap 34 and by
the support arm 15 is provided with a counter-weight 20 that
encloses a magnet (not shown in the drawings) and an
electromagnetic alignment sensor 21. With this structure, when
granular material is not present in the metering hopper 33, the
bottom flap 34 comes to automatically close the discharge mouth of
the hopper 33, due to the presence of the counterweight 20 and the
vacuum, and the magnet enclosed in the counterweight aligns with
the magnetic sensor 21, thus generating an electrical signal. Such
electrical signal is sent, e.g. by means of electric cable, to a
receiving unit, as will be further described below.
[0026] The transport air of the granular material 1a coming from
the container 1 is separated from the granular material falling
inside the receiver-meter 4 and is suctioned, possibly through a
first filter 6, via a mouth 7a placed in the upper head or portion
5 of the receiver-meter 4 and in fluid communication with one end
of a rigid or flexible duct 7, whose other end leads to a cyclone
filtering group 8. The latter is equipped with inner filter 9 with
high filtering capacity and traps even small particles dispersed in
the air that crosses it.
[0027] From the cyclone filtering group 8, a flexible duct 10
departs which is connected to a vacuum source, typically to the
suction mouth of a vacuum pump or a blower 11 provided with an
electric control panel 14, that expels the air drawn through the
ducts 3, 7 and 10 directly into the ambient air, e.g. by means of a
duct 12.
[0028] If the vacuum pump 11 is stopped, the granular material
possibly contained in the meter hopper 33, due to the lack of
vacuum and the weight of the granular material therein contained,
causes the discharge mouth of the hopper 33 to open, so that any
granular material is discharged into the underlying hopper 13.
[0029] When the magnet associated with the counterweight 20 is
aligned with the magnetic sensor 21, an electric control signal is
generated that is sent to the electric panel 14 of the blower or
vacuum pump 11, which is thus actuated, giving rise to a new
granular material feed cycle. The cycle is timed and can be varied
as a function of the size of the receiver-meter 4, of its distance
from the container 1 and/or of the type of granular material to be
transported.
[0030] With a plant of the above-described type, it is possible to
carry out the transport of plastic granular material for distances
up to 200 m, even for feeding several machines for the
transformation of plastic granular materials, in which case the
plant is called a "centralized" transport plant in jargon. One
example of a centralized reduced pressure transport plant is
illustrated in FIG. 4, where a single suction unit (pump or blower)
11 is provided and a cyclone filtering group 8 is arranged upstream
of the suction unit. The various receivers-meters 4 of number n,
for example 28 receivers-meters, are in fluid communication with
the filtering group 8 by means of a common duct 70, termed "vacuum
line" in jargon. In other words, the vacuum line 70 can serve a
number n of transformation machines M1, M2 . . . Mn. Preferably,
the receiver-meters 4 are each equipped with an interception valve
(not illustrated in the drawings) placed inside its respective head
5, which is drivable by a respective electro-pneumatic valve VE1,
VE2 . . . , VEn, in turn, controlled by a suitable electronic
control unit ECU set to control every zone of the plant, in
particular energizing at one time one or another receiver-meter 4
according to operating needs. This plant type is particularly
indicated for conveying granular material over relatively large
distances, on the order of 200 m. In this case, it is necessary to
employ a very powerful suction unit 11, since the loss loads must
be overcome, which are obviously much greater for high distances,
keeping in mind that installing several suction units would lead to
prohibitive costs.
[0031] With every cycle, the conveyance line L1, L2, . . . , Ln is
hit with a pre-established quantity of air and granular material
and at the end of every cycle it is completely evacuated of
granular material, owing to the presence of an interceptor device,
termed "cleaning valve", VP1, VP2 . . . , VPn provided for each
receiver-meter 4, so that when the suction unit 11 is stopped, the
conveyance line L1, L2, . . . , Ln is emptied. One such plant is in
particular used when one must feed, in subsequent cycles, different
granular materials to several machines for the transformation of
plastic granular material.
[0032] Should the conveyance line L1, L2, . . . , Ln be not emptied
at the beginning of every cycle, the tubing could be contaminated
or even obstructed by granules of the previously conveyed material
and the suction unit 11 may not be able to create a sufficient
suction effect suitable for ensuring both the evacuation of the air
and the transport of granular material.
[0033] One of the problems that occurs in conventional reduced
pressure transport plants of this type is that the flow speed or
intensity of the granules inside the tubes does not remain
constant, but varies, up to even doubling, with the variation of
the work conditions.
[0034] In FIG. 5, a typical cleaning valve is illustrated,
indicated with VP1 and inserted in the feed duct 3 of a respective
receiver-meter 4. It comprises a valve body, in which an air and
granular material inlet mouth 40 is obtained, where e.g. a nozzle
41 is provided for a first section of duct 3 in communication with
the respective lance member 2. An outlet mouth is also provided in
the valve body, preferably placed in offset position with respect
to the inlet mouth 40, from which a second section of the feed duct
3 departs, directed to the receiver-meter 4. In front of the inlet
mouth, but on opposite side thereof, a receiving opening is formed
in the valve body for a linear actuator device 43 of any suitable
type, which is set to control a preferably conical plug element 44,
moving it on command of the electronic control unit ECU between a
closed position, as shown in FIG. 5, in which it closes the inlet
mouth 40 or the nozzle 41, and an open position far from the mouth
40 or the nozzle 41.
[0035] An ambient air inlet opening 45 is also formed in the valve
body, externally provided with a filter 46, whereas within the
valve body such opening 45 can be intercepted by the plug element
44 when it is moved into open position by the actuator 43. With
this structure of the cleaning valve VP1, when the plug element is
moved into closed position of the inlet mouth 40 or of the nozzle
41, only ambient air is suctioned through the filter 46 and thus
through the receiver-meter 4 in order to carry out a cleaning cycle
of the tubing.
[0036] In a granular material transport cycle, i.e. when the
cleaning valve VP1 places the tube section 3 in communication with
the lance member 2, with the second section of tube 3 in
communication with its respective receiver-meter 4, due to the
reduced pressure created by the suction unit 11, the granular
material is caused to move and accelerate until it reaches a
so-called "equilibrium" speed.
[0037] The initial acceleration imparted to the granular material
mainly depends on the fact that the granular material at the start
finds the second section of tube 3, that directly communicating
with the receiver-meter 4, to be completely empty, and as it
receives granular material, the load losses of the internal air
flow and the friction against the walls increase, and consequently
the speed of the suctioned air flow decreases. These factors ensure
that the acceleration imparted to the plastic granular material 1a
gradually decreases until it reaches the equilibrium speed.
[0038] The same occurs when at the cycle's end the linear actuator
43 moves the plug element 44 into closed position against the inlet
mouth 40 or the nozzle 41, thus allowing the suction of ambient air
through the filter 46 in order to start the cleaning of the tubing.
In this step, the speed of the plastic material granules present in
the second section of the duct 3 tends progressively increase,
until complete emptying of the tubing has been obtained, achieving
flow intensity values that are even double that of the equilibrium
speed. At one such speed, the plastic material granules 1a scrape
against the walls of the tubes, in particular at the curved
sections of the tubes; consequently, a thin film is deposited,
especially at rough areas of the material (usually metal) composing
the tube, giving rise to the angel-hair phenomenon mentioned
above.
[0039] With reference to the embodiment of the present invention
illustrated in FIG. 6, a reduced pressure transport plant of
granular materials comprises one or more granular material
containers or silos 100, from which such material is suctioned by
means of one or more suction units 11, e.g. formed by one or more
vacuum pumps, and a gaseous medium or fluid, e.g. air or nitrogen,
which brings the granular material 1a therewith.
[0040] The various containers 100 of granular material 1a are in
fluid communication by means of a respective duct L1, L2, . . . ,
Ln with a respective receiver-meter RD1, RD2, . . . , RDn, each
duct L1, . . . Ln being interceptable by a respective cleaning
valve VP1, VP2, . . . , VPn.
[0041] The outlet for air from each receiver-meter RD1, RD2, . . .
, RDn is connected to a common vacuum line LV, in which an air flow
rate meter MP is provided, e.g. comprising a Venturi meter of any
suitable type, which is electrically connected with an electronic
control unit ECU.
[0042] Moreover, the plant comprises one variator device DV per
suction unit 11, which is arranged to vary the power or typically
the rotation speed of the electric motor (not shown in the
drawings) for actuating the respective suction units. Such speed
variator device is preferably of electronic type, e.g. a so-called
inverter, of any suitable type, which is intended to vary the
frequency of the power supply current to the motor of its
respective suction unit, and is in turn controllable by the
electronic control unit ECU.
[0043] The air flow rate meter MP is designed to send electrical
signals to the input of the electronic control unit ECU which are
correlated to the air flow rate in the vacuum line LV. The
electronic control unit ECU processes the signals received in input
in order to generate control signals to be sent to the speed
variator device(s) (inverter(s)) DV, which correspondingly vary the
frequency of the power supply current to the motor of the suction
unit(s) 11, 11a. In this manner, the depressurization or vacuum
level and consequently the speed of the granular material 1a
traveling along the tubes is adjusted as a function of the
variations in the transport conditions of the material, which as
stated above can vary when passing, for example, from the filling
step to the unloading step of the granular material in the various
suction lines L1, L2, . . . , Ln of the granular material 1a.
[0044] More particularly, since there is a correlation between the
parameters formed by flow rate, air speed and the vacuum level
inside the tubes, the electronic control unit ECU through the
inverter(s) DV modulates the rotation speed of the motor, and thus
the power of each suction unit 11, thereby producing an initial
acceleration ramp of the granular material 1a as a function of the
variation of the depressurization or vacuum level. Subsequently,
when an increase occurs of the load losses following the deposit of
granular material on the inner surface of the vacuum line LV, the
flow rate meter MP detects the flow rate variation caused by the
load losses, which results in the variator device(s) DV
(inverter(s)) increasing its rotation speed and thus the power of
the respective suction unit 11, 11a. In such a manner, the flow
rate decrease is gradually compensated, thus maintaining the
granular material 1a movement speed constant over time along the
ducts, or thus obtaining, if the circumstances require it, a
variable speed progression over time.
[0045] In the tube cleaning step, on the other hand, the reverse
process occurs. Once the feed of granular material 1a to the
respective receiver-meter RD1, RD2, . . . , RDn is stopped, the air
speed in the reduced pressure tubing increases. The flow rate meter
MP consequently detects a flow rate variation and sends a
corresponding signal to the electronic control unit ECU, which will
consequently drive the speed variator device(s) DV.
[0046] A control microprocessor (not shown), e.g. a PLC of any
suitable type placed in the electronic control unit ECU, is set to
create different transport condition profiles as a function of the
type of granular material 1a to be transported. Typically, in a
first storage portion of the control microprocessor, a table is
pre-stored, which is none other than a list of a first array of
plastic granular materials 1a with their respective characteristic
parameters of their respective optimal transport speed profile. In
a second storage portion, the operator of the reduced pressure
transport plant can store the parameters of possible new granular
materials, defined "experimental", through a suitable user
interface, e.g. consisting of a video unit (monitor) and access
means to the microprocessor for the data insertion, e.g. a keyboard
and/or a mouse. Preferably, the user interface is a graphical
interface with objects of "touch-screen" type.
[0047] With such device, it is possible to process any granular
material 1a, feeding it at the most suitable speed, without
generating powders, eliminating possible speed peaks, reducing the
transport tube wear by the conveyed granular materials, optimizing
the various cycles in a completely automatic manner, without
risking the obstruction of the transport ducts, adapting the
performances and productivity of the plant as a function of the
transported granular material and eliminating every impact of the
filtering effect on the speed and/or reduced pressure level
prevailing during the transport.
[0048] According to an advantageous variation of a reduced pressure
pneumatic transport plant according to the present invention, the
suction units 11 and 11a or possibly further provided suction
units, all equipped with a respective inverter DV, operate for
example in stand-by since they are connected in parallel with each
other, and are intended to begin operating in an alternating manner
or simultaneously if conditions require it in order to increase the
power, i.e. the depressurization level in the vacuum line LV and in
the receiver-meters RD1, RD2, . . . , RDn.
[0049] A reduced pressure transport plant as described above can be
used with only one suction unit 11 in order to ensure the feed of
granular material 1a to a single transformation machine or array of
transformation machines M1, M2, . . . , Mn.
[0050] Another reduced pressure transport plant of granular
material according to the present invention will be described below
with reference to FIG. 7, where the same reference numbers are used
for indicating components already described with reference to the
embodiment of FIG. 6. Such plant provides for the presence of a
suction unit 11 equipped with inverter DV. Advantageously, one or
more auxiliary suction units 11a can be connected in parallel to
the suction unit 11, also equipped with inverter DV, similar to
that described with reference to the embodiment illustrated in FIG.
6.
[0051] Also provided is a reduced pressure storage tank SER of any
suitable type, into which the various vacuum lines LV1, LV2, . . .
, LVn converge of the respective receivers-meters RD1, RD2, . . . ,
RDn serving a respective transformation machine M1, M2, . . . , Mn.
The tank SER is arranged upstream of the suction unit 11.
[0052] Preferably, downstream of the tank SER, a filtering group F
is provided for, to which the air suctioned by the tank SER is
directed in order to be filtered before reaching the suction
unit(s) 11, 11a. Moreover, according to such embodiment a
differential pressure meter DPS is also provided for of any
suitable type, intended to measure the load loss due to the
obstruction of the filtering group F and to generate respective
electrical signals to be sent to the input of an electronic control
unit ECU.
[0053] Starting from each container 100 of granular material to be
transferred, a feed duct L1, L2, . . . , Ln departs that is
intended to feed granular material to a respective receiver-meter
RD1, RD2, . . . , RDn. Provided in series in each conveyance line
L1, L2, . . . , Ln is both a cleaning line VP1, VP2, . . . , VPn
and a detection means RS1, RS2, . . . , RSn of the speed of the
granular material that moves inside the respective feed line, e.g.
comprising a sensor known in the state of the art and based on the
interaction of the flow of the solid material moving in the feed
line with a suitable electromagnetic signal, e.g. low energy
microwaves, which send corresponding control signals to the input
of the electronic control unit ECU.
[0054] In each vacuum line LV1, LV2, . . . , LVn, the following are
provided in series: [0055] an air flow rate meter VT1, VT2, . . . ,
VTn, e.g. comprising a Venturi meter of any suitable type, [0056] a
pressure meter PS1, PS2, . . . , PSn intended to measure the
pressure in the respective vacuum line LV1, LV2, . . . , LVn and to
send corresponding signals to the input of the electronic control
unit ECU, and [0057] a motorized valve MV1, MV2, . . . , MVn of any
suitable type arranged to maintain a correct reduced pressure or
vacuum level in the respective vacuum line LV1, LV2, . . . , LVn as
well as in its respective receiver-meter RD1, RD2, . . . , RDn.
[0058] The electronic control unit ECU is designed to process the
signals received in its input and to send, if deemed necessary,
control signals to one or more of the motorized valves MV1, MV2, .
. . , MVn, thereby obtaining a desired speed profile for each
specific granular material to be fed to the transformation machines
M1, M2, . . . , Mn, as well as to the speed variator device(s) DV,
which modulate the rotation speed and thus the power of the
respective suction units 11, 11a, thus always maintaining a desired
reduced pressure level or vacuum level in the vacuum storage tank
SER.
[0059] The electronic control unit ECU is suitable for diversifying
the functioning parameters in the various vacuum lines LV1, LV2, .
. . , LVn and in its respective receiver-meters RD1, RD2, . . . ,
RDn based on the pre-established movement speed for every type of
granular material inside each conveyance line L1, L2, . . . ,
Ln.
[0060] Of course, also in this embodiment, through a control
microprocessor of the electronic control unit ECU, e.g. a PLC, of
any suitable type, it is possible to store different transport
condition profiles as a function of the material type for every
transport line.
[0061] Alternatively, if it is desired to diminish the plant costs,
in place of the pressure meters PS1, PS2, . . . , PSn a single
pressure meter can be provided, such meter being designed to carry
out the measurement of the reduced pressure in the vacuum storage
tank SER and to send corresponding control signals to the input of
the electronic control unit ECU.
[0062] The above-described plant is susceptible to numerous
modifications and variations within the protection scope as defined
by the claims.
[0063] Thus, in place of suction means of the air or another
gaseous fluid, pressing or pressurizing means can be provided,
obtaining entirely similar results.
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