GB1596935A - Method and apparatus for removing gas from powder - Google Patents

Description

(54) METHOD AND APPARATUS FOR REMOVING GAS FROM POWDER (71) We, A/S NIRO ATOMIZER, 305 Gladsaxevej, DK-2860 Soeborg, Denmark, a Danish company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a method of removing gas from a powder as a receptacle is being filled with the powder, and to an apparatus for carrying out the method.

When a powder is filled into a receptacle, e.g. a bag, ambient gaseous medium, e.g.

air, readily mixes with the powder with the result that the powder filled into the receptacle can contain a considerable quantity of air.

If the powder is transported to the receptacle with the aid of a flow of air, this conveying air contributes to the intermixing of air with the powder.

The air intermixed with the powder in a receptacle can cause inconvenience insofar as the receptacle can acquire an unnecessarily large volume and, where the receptacle is a bag, the bag can become unstable and difficult to transport, e.g. on a belt conveyor.

A method of removing gas from a powder as a receptacle is being filled with the powder is described in U.S. Patent Specification No.

2,922,443. According to the known method gas is removed from powder being fed to a receptacle in the form of a bag through a spout located in the upper part of the bag.

The spout is provided with openings for sucking away of air which accompanies the powder being discharged through the spout However, this arrangement has the drawback that it cannot prevent air mixing with the powder when the powder moves from the spout to the surface of the mass of powder which already has been fed into the bag and settled in it.

According to the present invention there is provided a method of removing gaseous medium from a powder being filled into a receptacle, comprising the steps of positioning a filter in the receptacle, applying suction to the filter to draw the gaseous medium through the filter as the powder is filled into the receptacle, and relatively moving the filter and receptacle to maintain the filter at substantially the same level as the powder in the receptacle as the receptacle is filled with powder.

The invention also provides an apparatus for carrying out the method comprising means for supporting a receptacle, feed means for feeding powder into a receptacle supported on the support means, a filter arranged to be received in a receptacle supported on the support means, a suction source connectable to one side of the filter, and means for effect ing relative displacement of the receptacle support means and the filter during filling of the receptacle to maintain the filter sub stantially at the level of the powder surface in the receptacle throughout the filling process.

By locating the filter at the surface of the powder which has already been filled into and settled in the receptacle, e.g. a bag, the gaseous medium which mixes with the powder during the last part of its movement down to the surface of the settled powder can also be removed.

The contact of gaseous medium in the powder can be further decreased if the communication between the filter and the suction source is interrupted periodically and ambient atmosphere pressure is applied to the filter instead.

When the filter is connected to the ambient atmosphere, a small quantity of gaseous medium will flow from the ambient atmosphere backwards through the filter and flush the side of the filter which faces the powder free of powder particles clogging the filter.

Though this gaseous medium enters the powder, the subsequent suction phase becomes more effective, so that the end result is a decrease in the content of gaseous medium in the powder in the receptacle.

An embodiment of the invention is des cribed in detail below, by way of example with reference to the accompanying drawings, in which: Figure 1 shows an apparatus for filling a powder into a bag; Figures 2 to 6 show different stages during the filling of a bag using the apparatus; and Figure 7 is a diagram showing how the pressure p varies with time t during the filling of the bag.

The apparatus shown in Figure 1 comprises a stationary tube 1 and a screw 2 rotatably journalled in the tube 1 for feeding a powder 3 to a bag 4. The powder 3 is supplied to the tube 1 from a hopper 5 located at the upper end of the tube 1. A conical body 7 is fastened to the lower end 6 of the tube 1 by arms 8. The tube 1 is surrounded by a sleeve 9 which is displaceable along the tube 1 by a piston-cylinder arrangement 10 coupled to the sleeve 9 via an arm 11. The outlet 12 of the tube 1 is controllable by the sleeve 9. To close the outlet 12 the sleeve 9 is moved downwards such that its lower end 13 rests on the body 7 and to open the outlet 12 the sleeve 9 is moved up to the position in which it is shown in Figure 1.

The body 7 is on its under side provided with a filter 14. One side 15 of the filter confines together with the body 7 a chamber 16 which communicates with a conduit 17 which passes through hollow shaft 18 of the screw 2.

The conduit 17 is connected to a suction source, e.g. a centrifugal fan 19, via a threeway valve 20. The fan 19 is connected to the valve 20 through a conduit 21, in which a vacuum is created by the fan 19. The valve 20 is also connected to an inlet 22 for ambient air. The valve 20 is controlled by a control means 23 to connect the chamber 16, via the conduit 17, to either the vacuum in conduit 21 or to the air inlet 22.

The conduit 17 is connected to a pressureair source 24 via a valve 25 which is controlled by a control means 26. A non-return valve 39 is arranged in the conduit between the valve 20 and the inlet 22. The valve 39 prevents pressurised-air from escaping through the inlet 22 when the valve 25 is opened.

The open end of the bag 4 is attachable to a bag holder 27 which is vertically displaceable outside the sleeve 9. The holder 27 is displaced by a screw 28, which acts in a threaded portion of an arm 29 of the holder 27 and is driven by a motor 30.

The screw 2 for feeding the powder is driven by a motor 31 via the shaft 18 of the screw and gear wheels 32 and 33.

The motors 30 and 31, the piston-cylinder arrangement 10 and the control means 23 and 26 are controllable by a central control unit 34.

When a bag 4 is to be filled with powder 3 the following procedure is adopted: With the feed screw 2 stationary, the bag holder 27 is in its lowermost position and the sleeve 9 closing the outlet 12, the bag is attached to the holder 27. The holder 27 is then raised to an upper position, see Figure 2, such that the filter 14 lies adjacent the bottom of the bag. The point of time is now Tl, see Figure 7, the inlet 22 communicating with the chamber 16 such that the pressure in the chamber 16 is equal to the atmospheric pressure p0.

The outlet 12 is opened by raising the sleeve 9 (Figure 3) and the feed screw 2 is brought to rotate so that powder is fed out through the outlet 12. The control means 23 is activated to control the valve 20 so that the vacuum pressure in conduit 21 and atmospheric pressure through inlet 22 are alternately communicated with the chamber 16 so that the pressure in the chamber 16 alternates between atmospheric pressure p0 and the vacuum pressure p,. The time interval t, may be 0.2--0.3 seconds and the time interval t, 0.5 seconds.As the bag is filled with powder the bag holder 27 is lowered, the rotational speed of the feed screw 2 and the lowering velocity of the bag being controlled by the control unit 34 so that the filter 14 is always located at substantially the same level as the surface 35 of the powder which has settled in the bag. During the time interval t,, e.g. 0.5 seconds, the bag may descend 10 cm.

When the bag holder 27 has reached its lowermost position (Figure 5) the feed screw 2 is stopped and the outlet 12 is closed by lowering the sleeve 9 (Figure 6). The valve 20 is set such that at time T, the chamber 16 again communicates continuously with the inlet 22.

At the point of time T, the pressure-air source 24 is connected for a short time to the chamber 16 for flushing the filter 14 clean of powder before filling the next bag. This flushing can take place before or after a filled bag has been taken away -from the bag holder (Figure 6) prior to the filling of a new bag.

When the filled bag has been removed from the bag holder 27, a new bag is attached to the bag holder, after which the bag holder is raised and the described filling procedure repeated.

The filter 14 may be a porous body, which is so formed and arranged that it shows a substantially plane outer face 36. Furthermore, the filter 14 has a substantially cylindrical side surface 37. The surface 35 of the powder which has settled in the bag will normally extend from the joint 38 between the filter 14 and the conical body 7 to the side of the bag 4.

During the phases when the chamber 16 is connected to the ambient atmosphere via the valve 20 and the inlet 22, air flows from the conduit 17 and the chamber 16 backwards through the filter, which air will flush the sides 36 and 37 free from powder, the ability of the apparatus to accomplish a compact filling of the powder in the bag thereby being improved. Of course air is removed from the powder in the bag during alternate phases when the chamber is connected to the fan 19 through valve 20 and conduit 21.

It will be appreciated that the bag holder could be stationary and the filter and the filling arrangement raised during the filling process.

WHAT WE CLAIM IS:- 1. A method of removing gaseous medium from a powder being filled into a receptacle, comprising the steps of positioning a filter in the receptacle, applying suction to the filter to draw the gaseous medium through the filter as the powder is filled into the receptacle, and relatively moving the filter and receptacle to maintain the filter at substantially the same level as the powder in the receptacle as the receptacle is filled with powder.

2. A method according to claim 1, wherein periodically during the filling of the receptacle the suction is interrupted and atmospheric pressure is applied to the filter instead.

3. Apparatus for carrying out the method of claim 1, comprising means for supporting a receptacle, feed means for feeding powder into a receptacle supported on the support means, a filter arranged to be received in a receptacle supported on the support means, a suction source connectable to one side of the filter, and means for effective relative displacement of the receptacle support means and the filter during filling of the receptacle to maintain the filter substantially at the level of the powder surface in the receptacle thoughout the filling process.

4. Apparatus accordng to claim 3, including means for periodically interrupting communication between the suction source and the filter and connecting the said one side of the filter to ambient atmosphere.

5. Apparatus according to claim 3 or 4, wherein the filter is stationarily mounted and the support means for the receptacle is arranged to move vertically downwards during the filling process.

6. Apparatus according to any one of claims 3 to 5, wherein the feed means comprising a helical element mounted in a vertical tube having a lower outlet end, and the filter is carried by a body which is located outside the outlet end of the tube, the side of the filter opposite said one side being facing substantially away from the outlet of the tube.

7. Apparatus according to claim 6, wherein the tube is surrounded by a sleeve which is displaceable along the tube and, in cooperation with the body, acts as a valve for shutting off the outlet of the tube.

8. Apparatus according to any one of claims 3 to 7, wherein means is provided for connecting the said one side of the filter to a gas pressure source at the end of the filling process.

9. A method of removing gaseous. medium from a powder as a receptacle is being filled with the powder substantially as herein described.

10. An apparatus for carrying out the method of claim 1, substantially as herein described.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (10)

**WARNING** start of CLMS field may overlap end of DESC **. During the phases when the chamber 16 is connected to the ambient atmosphere via the valve 20 and the inlet 22, air flows from the conduit 17 and the chamber 16 backwards through the filter, which air will flush the sides 36 and 37 free from powder, the ability of the apparatus to accomplish a compact filling of the powder in the bag thereby being improved. Of course air is removed from the powder in the bag during alternate phases when the chamber is connected to the fan 19 through valve 20 and conduit 21. It will be appreciated that the bag holder could be stationary and the filter and the filling arrangement raised during the filling process. WHAT WE CLAIM IS:-

1. A method of removing gaseous medium from a powder being filled into a receptacle, comprising the steps of positioning a filter in the receptacle, applying suction to the filter to draw the gaseous medium through the filter as the powder is filled into the receptacle, and relatively moving the filter and receptacle to maintain the filter at substantially the same level as the powder in the receptacle as the receptacle is filled with powder.

2. A method according to claim 1, wherein periodically during the filling of the receptacle the suction is interrupted and atmospheric pressure is applied to the filter instead.

3. Apparatus for carrying out the method of claim 1, comprising means for supporting a receptacle, feed means for feeding powder into a receptacle supported on the support means, a filter arranged to be received in a receptacle supported on the support means, a suction source connectable to one side of the filter, and means for effective relative displacement of the receptacle support means and the filter during filling of the receptacle to maintain the filter substantially at the level of the powder surface in the receptacle thoughout the filling process.

4. Apparatus accordng to claim 3, including means for periodically interrupting communication between the suction source and the filter and connecting the said one side of the filter to ambient atmosphere.

5. Apparatus according to claim 3 or 4, wherein the filter is stationarily mounted and the support means for the receptacle is arranged to move vertically downwards during the filling process.

6. Apparatus according to any one of claims 3 to 5, wherein the feed means comprising a helical element mounted in a vertical tube having a lower outlet end, and the filter is carried by a body which is located outside the outlet end of the tube, the side of the filter opposite said one side being facing substantially away from the outlet of the tube.

7. Apparatus according to claim 6, wherein the tube is surrounded by a sleeve which is displaceable along the tube and, in cooperation with the body, acts as a valve for shutting off the outlet of the tube.

8. Apparatus according to any one of claims 3 to 7, wherein means is provided for connecting the said one side of the filter to a gas pressure source at the end of the filling process.

9. A method of removing gaseous. medium from a powder as a receptacle is being filled with the powder substantially as herein described.

10. An apparatus for carrying out the method of claim 1, substantially as herein described.