Deaerator for automatic bag filling machines for particulate materials

Abstract

 The invention consists in making the wall on which the product to be bagged flows, in the area where the product is fed to the filling nozzle, of a filtering material, through which air can pass but not the product to be bagged, and in closing such an area of filtering porous material, with an impermeable wall so as to form a chamber, where vacuum in the bag filling stage or a pressurized air blow in the stage of replacing a filled bag with an empty bag on the nozzle, are alternately produced.

Description

[0001] The present invention relates to a deaerating device for removing air contained in particulate materials inside the automatic bag filling machines.

[0002] The known automatic bag filling machines for granular and/or powdery materials are of the static or rotary kind and generally consist of a hopper receiving the material to be bagged, fed to it by generally pneumatic known means, said hoppers being provided with a number of delivery nozzles, on which the bags to be filled are inserted, each nozzle being provided with feeding means connected with bag weighing and ejecting means, which stop material delivery and eject the bag when the latter reaches a predetermined weight, the filling operation being resumed only when another bag is inserted on the nozzle.

[0003] Several systems for feeding the material to the filling nozzle are known: screw feeders, where a screw arranged at the hopper bottom and partially inserted in the nozzle, causes material to advance in it; turbine feeders, where a wheel provided with rotary blades pushes the material into the nozzle (this system may have either a horizontal or a vertical turbine); belt feeders, where the material advanced by a drum, is practically thrown into the nozzle by a conveyor belt partially wrapping said drum and moving at a speed equal to the surface speed of the drum.

[0004] It is also known that when the particulate material arrives at the nozzle, it contains or encloses considerable amounts of air, due to the means generally employed for carrying or transferring the particulate materials from storage bins to the bag filling machines and also from the production equipments to the storage bins, and the greater is the amount of enclosed air, the lower is the flowability of the material.

[0005] A problem still to be solved and highly felt by the manufacturers of bag filling machines, is to remove the greatest possible amount of air enclosed in the material, during the bag filling operation, since said air at this point of the working cycle is no more required and on the contrary it has a harmful effect because with the bigger volume of material, it increases bag filling time and bag volume for the same weight, as the bag has to contain a certain volume of air in addition to the particulate material.

[0006] Several attempts were already made to remove a certain quantity of air by vacuum means during the bag filling operation, however without practical and satisfactory results.

[0007] The present invention solves the problem of removing air contained in the material before the bag filling operation, and thorough tests and experiments showed that this system is reliable, and a considerable reduction of the bag filling time is obtained (so that it becomes a fraction of the time presently required for some materials such as hydrated lime) as well as an increase in bag capacity, so that it is possible either to use smaller bags or to increase the contents in the presently used bags.

[0008] The present invention consists in making the wall of the inlet area for the material in the nozzle, and a portion of the nozzle wall (according to the feeding system used, either a turbine feeder or a screw feeder) of a filtering material, through which air can be passed but not the product to be bagged, such as porous material, filtering wires and so forth, and making under said wall a chamber where vacuum or a pressurized air blow are alternately produced, said vacuum being produced during the bag filling operation, so as to remove enclosed air from the material flowing along said wall, and the pressurized air blow being produced during the stage of replacing on the nozzle a filled bag with an empty bag, in order to prevent that minute particles of material entered in the capillary air passages, in the long run clog the air filtering area.

[0009] The invention will by better understood be the following detailed description of a preferred and non limiting embodiment, given as an example only and illustrated in the accompanying drawings, in which:

Fig. 1 is a vertical sectional showing of the invention applied to a nozzle fed by a screw feeder;

Fig. 2 is a cross-sectional view of the invention of Fig. 1;

Fig. 3 is a showing of the invention applied to a nozzle fed by vertically arranged turbine feeder; and

Fig. 4 is a horizontal sectional view of the invention of Fig. 3.

[0010] With reference now to Figs. 1 and 2, reference numeral 1 is a hopper feeding a nozzle 2 of a bag filling machine of the kind fed through a screw feeder 3. The lower wall of the hopper 1 and a portion 4 of the wall of nozzle 2 according to the present invention is made of an air permeable material, such as a porous blanket or baffle, a filtering wire or cloth and the like, suitably backed in case non rigid materials such as cloth and the like are being used.

[0011] The zone occupied by the material is closed to the outside by an impermeable wall 5 so as to form between them a chamber 6 to which is connected a pipe 7 which is divided into two lines 8 and 9, which can be shut off by valves 10 and 11. Line 8 is connected to a vacuum source and line 9 to a source of pressurized air.

[0012] Referring now to Figs. 3 and 4 relating to a turbine fed nozzle, the system comprises hopper 21, nozzle 22, a vertically arranged turbine 23 actuated by a pulley 32 connected to a suitable motor (not shown), a permeable wall 24 closed to the outside by an impermeable wall 25 so as to form an intermediate chamber 26 to which a pipe 27 is connected, which is divided into two lines 28 and 29 which can be shut off by valves 30 and 31, of which line 28 is connected to a vacuum source and line 29 to a source of pressurized air.

[0013] Operation is as follows: during actuation of the nozzle, i.e. when the screw or turbine feeder is operative and fills the bag, valve 10 or 30 is open and in the chamber 6 or 26 vacuum is produced, so as to suck air contained in the material which is flowing on the permeable wall 4 or 24 to the nozzle mouth.

[0014] When the bag is filled and the screw or turbine feeder is stopped, valve 10 or 30 is closed at the same time and valve 11 or 31 is opened for a very short time (fraction of a second), so as to give an air blow in the reverse direction to the filtering baffle and to clean it from the particles of material that during air suction could have clogged the ducts of passage of said air. When the filling operation is resumed, valve 10 or 30 is again opened and air contained in the material is again sucked.

[0015] In the above description of the operation, the air blow is being given at each bag filling step. However, this is not indispensable and since the frequence of such a counterflow cleaning operation of the filtering baffle mainly depends upon the kind of material to be handled, said cleaning operation may be effected also after a certain number of filling steps, or it may be suitably timed, or the counterflow pressurized air blow may be released only when a suitable known device detects that the filtering baffle reached a predetermined clogging degree, e.g. when the vacuum level in the chamber 5 or 25 goes beyond a fixed level.

[0016] It is to be understood that the described embodiments were only illustrative and non limiting examples and many other practical embodiments may fall within the scope of the invention as defined in the appended claims.

Claims

1) Deaerator for automatic bag filling machines for particulate materials, characterized by the fact that the walls of the area through which flows the material to enter the bag filling nozzle, are made with air permeable or air filtering materials, said walls (4, 24) being in turn enclosed by air impermeable walls (5, 25), so as to form an intermediate chamber (6, 26) which is alternately connected to a vacuum source (8, 28) or to a pressurized air source (9, 29), so that during the bag filling step vacuum is produced in said chamber (6, 26), sucking away air from said particulate material through said filtering walls (4, 24), while at the time interval between discharge of a filled bag and insertion of a new empty bag, a counterflow air blow is produced for a very short time, in order to clean the filtering wall (4, 24).

2) Deaerator according to Claim 1, characterized by the fact that the action of cleaning the filtering area (4, 24) by means of a pressurized air blow is not required to take place at every bag filling step, but it may be effected from time to time after a certain number of bag filling steps according to the filter clogging degree dependent upon the kind of particulate material being handled, the frequence of the cleaning action being determined by a timer or like known devices, or by the detection through known means of the increase beyond a fixed level, of the vacuum degree in the chamber for sucking air contained in the particulate material.

3) Deaerator according to Claim 1, characterized by the fact that it may be generally applied to all kinds of presently used nozzles and relevant devices for feeding the particulate materials.

Drawing