EP0092265B1

EP0092265B1 - Deaerator for automatic bag filling machines for particulate materials

Info

Publication number: EP0092265B1
Application number: EP83200458A
Authority: EP
Inventors: Mario Moltrasio
Original assignee: Car Ventomatic SpA
Current assignee: FLSmidth Ventomatic SpA
Priority date: 1982-04-16
Filing date: 1983-03-31
Publication date: 1987-07-22
Also published as: DE3372602D1; IT1151883B; ATE28434T1; EP0092265A3; EP0092265A2; IT8220789A0

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

The present invention relates to a deaerating device for removing air contained in particulate materials inside the automatic bag filling machines.
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.
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.
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.
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.
There are several systems for removing a certain quantity of air during the bag filling operation, generally using vacuum, such as the system disclosed in GB-A-1011489 wherein a certain quantity of air is removed from the material by providing inside the loading nozzle a porous duct and sucking air during passage of material, as well as by cleaning the porous duct blowing intermittently air in said duct instead of sucking the air. The prior art portion of claim 1 is based on the disclosure of this document. This latter system does not solve completely the problem as it did not practically give the expected results because a considerable amount of air was still left in the product.
The present invention as defined in claim 1, applicable only to turbine filling machines, completely solves the problem of removing most of the 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.
The invention consists in effecting continuously suction of air from the product before introducing the material in the nozzle, by making the wall of the area preceding the nozzle, where the material is placed before being pushed into the nozzle by the turbine blade, of a filtering material, thus adapted to be passed by air but not by the product to be bagged, such as porous material, filtering wires and so forth, and making under said wall a chamber where vacuum may be produced, so as to remove enclosed air from the material before it is pushed into the nozzle, said vacuum operation being interrupted from time to time by a pressurized air blow to be effected 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.
The invention will be better understood by 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 showing of the device of the present invention; and
Fig. 2 is a horizontal sectional view of the device of Fig. 1.

With reference now to Figs. 1 and 2 relating to a turbine fed nozzle, the system comprises a hopper 21, containing the fluidized material, a 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.
Operation is as follows: during actuation of the nozzle, i.e. when the turbine feeder is operative and fills the bag and also when the turbine is stopped, valve 30 is open and in the chamber 26 vacuum is produced, so as to suck air contained in the material which at that time is at the bottom of the hopper and must be pushed by the blade of turbine 23 to the nozzle mouth on the permeable wall 24.
At intervals fixed by trials, but always during the bag replacing stage, i.e. when the turbine feeder is stopped, valve 30 is closed and valve 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, and then valve 31 is at once closed again, valve 30 is again opened and suction of air contained in the material is resumed.

Claims

1. Deaerator for automatic bag filling machines for particulate materials provided with a hopper (21) and a nozzle (22), wherein deaeration takes place through a wall (24) made of air permeable or air filtering materials, being in turn enclosed in air impermeable walls (25) so as to form an intermediate chamber (26) therebetween, which is alternately connected to a vacuum source (28) so as to suck air contained in the material or to a pressurized air source (29) to clean the filtering wall (24), characterized in that the dearation area is on the bottom of the hopper (21) before the inlet of the nozzle (22), the material being fed by means of the blades of a turbine feeder (23) pushing the material to the nozzle (22), air being continuously sucked from the overlying material, with the exception of short intervals in which the vacuum is stopped and pressurized air is blown for cleaning the filtering baffle wall (24).

2. Deaerator according to Claim 1, characterized in that the air blowing phase is effected only during the bag change operation with turbine feeder (23) stopped.