Apparatus for the pneumatic conveyance of pulverized or granulated matter

The apparatus comprises stations or silos for accumulating the material, which are connected to stations for the drawing thereof through a pneumatic line including a recycling section which conveys the "trailings" or residues of material towards the silos thus performing the recovery thereof. Devices mounted on the pneumatic line at the stations perform the drawing of the material during its conveyance in the pneumatic line and discharge it therefrom, while for performing the recycling they allow the free transfer of the residues towards the silos.

BACKGROUND OF THE INVENTION 
The present invention relates to an apparatus for the pneumatic conveyance 
of pulverized or granulated material between collection units and drawing 
stations with the extraction of the same material from the flow line 
during conveyance. 
The apparata to which the present invention relates are employed to 
transfer loose pulverized or granulated material (e.g. flour, corn, 
granulated plastic material and the like) from collecting silos towards 
drawing stations wherein the flow of material is interrupted. In these, 
the material is weighed and discharged onto the machines which employ it. 
To perform said transfer, a pneumatic line is employed, wherein the air, 
in aspiration or in compression, conveys the material from the collecting 
silos towards the drawing stations. These are composed, in conventional 
apparata, of a decanting cyclone inside which the air is separated from 
the powders. In particular, the latter fall downwards towards the output 
of the cyclone which is controlled by a system of valves which are 
operated by a reducer, while the air originating from the pneumatic line 
is discharged upwards and conveyed inside filters to separate the residues 
of power which is still carries. The filtered air is then finally 
discharged into the environment where the drawing stations are 
accommodated. 
The conventional apparata described above have many disadvantages. Among 
these, the need to employ a cyclone fitted with valves with a related 
reducer and a filter, provided in each material drawing point from the 
pneumatic line; the use of a system of routing valves to route the powders 
towards the various drawing stations, the number of which cannot obviously 
increased beyond that of the routings allowed by the valve; the 
significant bulk represented by the expensive cluster of cyclones and 
associated filters, the installation of which requires very spacious and 
high accommodations. 
Still another disadvantage lies in the discharge into the environment 
occupied by the drawing stations of a certain amount of pulverized 
material dragged along by the air leaving the filters. 
The most serious problem, however, is represented by the elimination of the 
"trailings" or residues of material which remain in the pneumatic line of 
known apparata. Actually, once the required weighing or metering values of 
the material are achieved, the valves which control the discharge thereof 
are closed and significant amounts of material are trapped in the 
cyclones. This, if discharged, alters the desired values, having a 
negative effect on the preset mixtures, and the consequences on the costs 
of recovering the residues are similarly negative. For the recovery and 
the elimination of the trailings, conventional apparata may comprise a 
plurality of separate silos for collecting the residues, which makes the 
apparatus even more complicated, expensive and bulky. The operations 
related to these recoveries furthermore extend the overall material 
processing times. The residues, on their part, complicate and hinder the 
adjustment of the devices of the apparatus, which must be conventionally 
controlled by electronic controls which easily give rise to problems. 
These problems are all the more relevant, if it is considered that the 
circulating material can be of a different nature, and therefore require a 
specific and selective control of its conveyance. 
SUMMARY OF THE INVENTION 
The present invention has the aim of overcoming the above said limitations 
and disadvantages of conventional apparata of the kind described above. In 
particular, the invention has the object of providing an apparatus for the 
pneumatic conveyance of loose pulverized or granulated material which is 
simpler, less bulky and less expensive than those currently in use. It 
proposes to solve the problems constituted by the drawing of material 
during the conveyance phase inside the pneumatic line, as well as by the 
control and the recovery of the "trailings". 
This aim and other objects are achieved with the apparatus for the 
pneumatic conveyance of pulverized or granular material according to the 
present invention, wherein the conveyance circuit for the material 
comprises collecting stations and drawing stations for the same material, 
connected to each other by a pneumatic line for the conveyance of the 
latter, characterized in that said material conveyance circuit is a closed 
circuit, said pneumatic line providing a recycling section for the 
residues of material at said collecting stations. 
According to further characteristics of the invention, said drawing 
stations each comprise a device suitable for drawing and discharging the 
material from the pneumatic line, during its conveyance inside the latter. 
This device of the apparatus according to the invention is provided 
communicating, through the same pneumatic line, with the loading sections 
of the material to the abovementioned collecting stations; it is also 
essentially composed of rotating blade means fixed on the pneumatic line 
with the axis of rotation of the blades parallel to the direction of flow 
of the material inside the same pneumatic line. Along the latter, and 
according to a further characteristic of the invention, said drawing 
stations are arranged in series, each being endowed with the above 
described device. 
The apparatus of the invention is notably advantageous with respect to 
those currently known. In fact, it no longer entails the use of cyclones 
and associated valves and filters, but is provided with devices which are 
simple and easy to produce from elements and materials commonly available 
on the market; dimensions and overall costs of the apparatus are 
consequently much lower than those of known systems. The extraction of the 
material from the pneumatic line is performed in a complete manner without 
reducing the airflow in the path and the material is discharged without 
compression. For separating the air from the powder residues, the filters 
normally provided on the sections for loading material into the collecting 
silos are advantageously employed, according to the invention, which 
filters are more efficient than the conventional ones employed on the air 
vent of the cyclones. 
The problems related to the elimination of the residues on the pneumatic 
line are solved by virtue of the presence of the recycling of the material 
which is achieved by employing particular drawing and discharge devices 
which, when the blades are still, allow the free passage of the material 
along the pneumatic recycling line, while they perform a drawing action 
when the blades are moving. 
The conveyance of the flow of material towards the different drawing 
stations can be effected, differently from the solutions of the prior art, 
without the use of routing valves, but simply by controlling the motion of 
the blades of the same separating devices. In particular, since there is 
no longer the need to impart preset deviations on the flow of material, it 
is possible to provide along the pneumatic line any number of drawing 
stations, the quantity of which is no longer related to the number of ways 
of any routing device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The apparatus illustrated in FIG. 1 comprises a bank of collecting silos 1, 
2 and 3, in which the granulated or pulverized material is stored, and a 
plurality of material drawing stations 4, 5. The apparatus furthermore 
comprises a pneumatic line provided with the appropriate filters and 
aspirators (or compressors) generally designated with the reference 
numeral 6. The material originating from the silos 1, 2 and 3, which in 
the example described are in the number of three, but which naturally can 
be in any number whatever, is fed into the pneumatic line 6 through 
valves, respectively 7, 8 and 9, which control its discharge from the same 
silos and subsequently is carried along by the air towards the drawing 
stations 4 and 5. The latter are each provided with a drawing and 
discharge device 10, intended to remove the material from the pneumatic 
line during its transfer inside the same and to discharge it towards the 
stations 4, 5 without decreasing the airflow in the path, and discharging 
the material free from compression. The air thus freed from powder or 
granules continues its path towards the sections 11, 12 and 13 for the 
loading of the material to the silos, respectively 1, 2 and 3. The air 
outflowing from the silos passes through filter 14, already normally 
provided in silos, where it deposits the last traces of material and is 
finally discharged into the atmosphere. In this last section, or recycling 
section 16 of the pneumatic line 6, two-way valves 15 are provided for 
directing the flows of the conveyance medium towards the individual silos. 
The material collected at the stations 4 5 is subsequently weighed and 
packaged or sent to the specific use. When inside the drawing stations 4 
and 5 the desired amount of the circulating material has been achieved, 
the valves 7, 8 and 9 are closed and the devices 10 are arranged in a 
recycling position for the residuals of material which fill the pneumatic 
line in the section between the silos valves and the drawing stations. In 
this recycling position, the devices 10 allow the free flow of the 
material towards the collecting silos where, as previously described, it 
is recovered. Therefore, the pneumatic line 6 is, together with the 
collecting silos and the drawing stations, a closed circuit for the air 
and for the material conveyed therein, the residues of which, either 
deriving from the closing of the valves 7, 8 and 9, or prevented by the 
air from being subject to the drawing action of the devices 10, are taken 
back into the silos (and are recovered therefrom) through the recycling 
section 16 of the pneumatic line 6. 
The device 10 employed in the apparatus of FIG. 1 is illustrated in detail 
in FIGS. 2 and 3 and is essentially composed of an impeller 17 with 
blades, rotatably mounted in a chamber 18 provided inside a shell 19 of 
the same device. The structure of the latter is completed by lateral 
covers 20, 24 at which the driving axle 25 of the impeller 17 is provided 
with the associated bearings 22 and sealing rings 21, 23. 
The upper part 26 of the shell 19 is closed, while the lower part 27 is 
open and represents the discharge section for the material towards the 
stations 4, 5 (arrow F1 of FIG. 2). The air-material mixture enters in the 
upper part of the chamber 18 through the passage section 28 (FIG. 3) which 
represents the connecting portion between the pneumatic line 6 and the 
device 10. The material enters the chamber 18 (arrow F2 of FIG. 2) with a 
direction which is parallel to that of the axis of rotation 29 of the 
impeller 17. Here it interferes with the blades 30 which draw material 
from the flow line and discharge it downwards through the section 27 of 
the device. Advantageously, the chamber 18 has an oval cross section which 
is intended to create a certain sealing action at the points of contact 31 
between the blades 30 and the internal wall of the same chamber 18. By 
virtue of this sealing action, the upper part of the chamber 18, traversed 
by the flow of pressurised air, is isolated from the lower part, so that 
the material is discharged towards the stations 4, 5 substantially at 
atmospheric pressure. The air thus freed from the material continues its 
path flowing out of the opening 32 of the device 10 (arrow F3 of FIG. 2) 
thus entering the recycling section 16 of the pneumatic line 6. In the 
recovery phase of the residues of material, or simply if it is desired to 
interrupt the drawing at one or more stations 4, 5, it is sufficient to 
stop the motion of the impeller 17, the blades 30 whereof neither exert 
the drawing of material from, nor constitute an obstacle to the flow of 
material along the pneumatic line. 
By virtue of the particular structure and arrangement of the drawing and 
discharge devices on the pneumatic line 6, the stations 4, 5 can be 
mounted in series on the apparatus practically without limitations in 
number. 
Naturally, the invention as described and illustrated is susceptible to 
variations and modifications without thereby abandoning the scope of the 
protection if these variations reproduce the embodiment of a closed cycle 
of the material between the collecting and drawing stations by means of 
devices which extract the material from the flow line during its 
conveyance.