GB1580124A

GB1580124A - Method and apparatus for cleansing soiled chips of synthetic plastics material

Info

Publication number: GB1580124A
Application number: GB11841/78A
Authority: GB
Original assignee: Maschinenfabrik Buckau R Wolf AG
Current assignee: BWS Technologie GmbH
Priority date: 1977-03-28
Filing date: 1978-03-23
Publication date: 1980-11-26
Also published as: DD136346A5; PL205587A1; DE2713730C2; FR2385513A1; DE2713730A1; FR2385513B1; CS203101B2; ATA109178A; PL112673B1; AT355528B; IT7821491A0; SU974928A3; IT1093879B

Description

(54) METHOD AND APPARATUS FOR CLEANSING SOILED CHIPS OF SYNTHETIC PLASTICS MATERIAL (71) We, MASCHINENFABRIK BUCKAU R. WOLF AKTIENGESELLSCHAFT, a German company, of Grevenbroich, Lindenstrasse 43, Germany, 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 and apparatus for cleansing soiled chips of synthetic plastics material.

According to one aspect of the present invention, there is provided a method of cleansing soiled chips of synthetic plastics material, comprising the steps of washing the material in a washing liquid in a state of turbulence and retained in a vessel containing a straining plate down through which dirt removed from the material is filtered, and then passing the material through an atmospheric zone which is in a state of turbulence and subjecting the material to rinsing.

According to another aspect of the present invention, there is provided an apparatus for carrying out the method of cleansing soiled chips of synthetic plastics material defined in the preceding paragraph, the apparatus comprising a vessel having a strainer plate which is sloped to extend below and above a level of washing liquid in the vessel in use thereof, an outlet below said plate for removal of dirt, an inlet for the plastics material to be cleansed above a lower region of the plate and an outlet for the cleansed plastics material above an upper region of the plate, there being a rotatable shaft above and extending parallel to the plate, said shaft carrying fluid turbulence-causing means to act on and transport said material from below the liquid level to above it, and there being means to rinse the material when it is above the liquid level and when acted on by said fluid turbulence causing means.

For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawing, in which: Figure 1 is a schematic sectional view of an apparatus for carrying out a method of cleansing soiled chips of synthetic plastics material, and Figure 2 is a view similar to Figure 1 and showing two possible modifications of the apparatus.

Referring to Figure 1, the apparatus illustrated is for cleansing soiled chips of synthetic plastics material by subjecting the material to a basic three-stage treatment, in which the chips are first of all washed in a liquid bath in order to soften the dirt on the chips. This operation is followed by a mechanical treatment, during which the chips are rubbed against one another outside the liquid bath, in order to detach the dirt from the chips. In the third stage, the detached dirt is washed off the chips and the cleansed chips are transported away.

Figure 1 shows a vessel in the form of a trough 1 filled up to a liquid level 3 with a washing liquid. A filter or straining plate 2 is fitted into the trough 1 at an angle to the horizontal so that it slopes so as to ascend from a material inlet zone to a material outlet zone of the trough, the plate 2 intersecting the surface of the liquid at 7 at an angle a. A rotating shaft 4 is arranged above and parallel to the plate 2, the shaft 4 being mounted at one end in a bearing 5 and being driven at its other end by a motor 6. A stirrer mechanism 8 is arranged on the shaft 4 in the material inlet zone of the trough, the mechanism 8 consisting of paddles 11 connected fast to the shaft 4 by respective arms 12. In the material outlet zone, the shaft 4 carries a worm or screw 9. Paddle-type screws or double screws may be provided instead of the paddles 11.The stirrer mechanism 8 constitutes a fluid turbulence-causing means which acts on and transports the chips of synthetic plastics material from below the liquid level 3 to above it and also acts on the chips of synthetic plastics material after it has left the liquid by producing a state of turbulence in the air.

In use of the apparatus, the soiled chips of synthetic plastics material to be cleansed enter the trough 1 through an inlet pipe 16 and fall freely into the inlet zone of the washing liquid.

However, should it be found that the free fall is disadvantageous, then a conveyor screw 17 (Figure 2) may be provided inside the inlet pipe 16, by means of which screw 17 the chips are introduced into the liquid in a controlled manner. The screw 17 may extend down into the liquid and is driven by a motor 20, which is seated beneath a hood or cover 19 in an inlet hopper 18 above the pipe 16.

By means of a weir or barrier 21, the chips are introduced into the liquid and, because of the rotating movement of the stirrer mechanism 8 pass into the liquid, where the chips are given a turbulent motion by the stirrer mechanism 8 and are slowly conveyed to the point of mtersection 7 between the plate 2 and the surface 3 of the washing liquid. By means of this treatment beneath the surface of the liquid, any dirt which is adhering to the chips is softened and fine dirt particles strain through the plate 2 to sink down the funnel-shaped surfaces of the trough to an outlet 39.

The washing time will be varied according to the degree of soiling of the chips.

Depending on the position of the paddles 11, the chips are fed slowly to a greater or lesser degree to a material outlet 24. This effect may be enhanced by baffle plates or checking members 13. Those foreign bodies which can easily be washed off and float and which are introduced with the chips are blocked in their movement by a weir 22 and are drawn off through a discharge pipe 23 which is arranged in the region of the liquid surface 3, the chips themselves sinking in the liquid.

The chips with the softened soiling substances clinging to them now pass into the region of that part of the filter or straining plate 2 which is arranged above the surface 3 of the liquid. Here, the chips are once again given a turbulent motion but this time in free air, by the stirrer mechanism 8, and as a result are rubbed against one another. In this zone, the softened dirt is detached from the chips and either moves forwardly onto the plate 2 or, if the dirt particles are smaller than the opening in the plate 2, they pass into a dirt collectin chamber 40 of the trough, the chamber 40 being disposed beneath the plate 2 and having a sludge or dirt discharge outlet 39. A valve (not shown) is opened at intervals for the discharge of the accumulated dirt from the trough.

The particles of dirt or soiling substances which have still not fallen off the chips are then treated in the region of the screw 9 with a washing liquid, which is sprayed from washing nozzles 10 onto the chips. At this point, all particles of dirt are washed free of the chips. The separated dirt and chips then pass together into the outlet 34.

The degree to which the chips are soiled is variable. As a consequence, the treatment has to be varied from time to time. With a dirt which is adhering in a particularly persistent manner, it is advantageous if the softening process is carried out over a longer period. One way this may be effected is by the slope of each paddle 11 being so adjusted that the chips are only transported slowly towards the outlet. Should the slope of the paddles and the slope of the baffle plates 13 (which may also be adjusted) not be sufficient, then it is possible for the entire trough 1 to be swung about a pivot point 14 and lowered or raised by means of a height-adjustment device 15. With a lowering of the trough 1, the liquid level 3 moves in an upward direction, so that the washing zone is thereby enlarged.Conversely, with a raising of the trough, the washing zone can be made smaller and as a result the subsequent treatment zone above the liquid in the region of the screw 9 can be increased in size.

The screw 9 transports the cleansed chips intermittently towards the outlet 24. The wet chips have to be separated completely from the remaining dirt and freed from water and dried. It is best economically for this subsequent operation to be carried out with a continuous flow. In order continuously to feed the chips to the drying stage, a discharge device 25 is arranged beyond the outlet 24. The device 25 consists of a vertical shaft 26, which is situated immediately beneath the outlet 24. This shaft 26 has an outlet pipe 44 which is closed by a valve (not shown). The shaft 26 is filled with a liquid to a level 29 which is caused to lie above an overflow edge 45 of the shaft (see below).

The chips descending from the outlet 24 fall together with the dirt into the liquid in the shaft 26. Since the apparatus is primarily intended for synthetic plastics not capable of floating, it is necessary for this purpose to maintain an upwardly-directed flow of liquid within the shaft 26. For this purpose, a liquid supply pipe 36 with a strainer hood 35 is Provided. The liquid flowing from the hood 35 is so adjusted that the chips which have been cleansed are kept thereby on or near the surface 29 and only allow the heavier particles of dirt to descend. The upward movement of the cleansed chips can be assisted by means of an additional supply of air. For this purpose, an air pipe 37 is led into the shaft 26, from which a by-pass pipe 38 can be extended to the pipe 36.By regulating the air flow through the by-pass pipe 38, the quantity of liquid supplied to the pipe 36 can be reduced.

A horizontally-extending cleansed material discharge duct 30 is arranged in the upper region of the shaft 26, with which duct 30 is associated a rotating filter or strainer drum 26.

This drum is mounted on a shaft 28 (driving and mounting means for the shaft 28 not being shown). The strainer drum 26 is so arranged that it projects only slightly above the liquid level 29 and into the discharge duct 30. Liquid flowing from the duct 26 over the edge 45 flows over a surface 30a onto and into the drum 27. The cleansed chips are taken up from the surface 30a by the rotating surface of the strainer drum and are carried away from the liquid and thereby fed over a surface 30b to a discharge pipe 31. The surface 30a, over which the chips are fed onto the drum, is at a lower level than the surface 30b, over which the chips are fed to the discharge pipe 31. A pneumatic conveying arrangement (not shown) is connected to the pipe 31 and serves to extract the cleansed chips.The liquid which flows into the strainer drum 27 is extracted through a lateral opening 34 and fed to a liquid-discharge pipe 33. Pipe connections may be so arranged that the liquid may from here be supplied from the liquid-discharge pipe 33 as circulation water to the pipe 36.

The construction shown in Figure 1, because the container 40 is funnel-shaped, requires a considerable overall height. In order to reduce this height, the vessel may take the form shown in Figure 2 in which a trough 41 is provided beneath the strainer plate 2, the trough receiving a conveyor screw 42 which acts to feed the dirt and sludge filtering through the filter plate 2 to the outlet 39. The screw 42 may be driven through a driving arrangement 43 from the screw shaft 4.

It will be appreciated that, instead of providing a stirrer mechanism 8 in the form shown the strainer plate may be in the form of a sieve-like vibratory channel, in which case the strainer plate 2 would consist of a U-shaped channel or duct, of which the bottom surface is in the form of a screen or sieve. The complete unit is suspended in an arrangement inside the trough 1 and is driven with an unbalanced motor. Accordingly, the chips are conveyed through the strainer by vibrations, so that the effect is the same as with the constructions illustrated. Thus, in this case also, the dirt adhering to the soiled plastics chips is initially softened below the liquid level, is mechanically detached above the liquid level and is then washed out in the sprinkler zone.

WHAT WE CLAIM IS: 1. A method of cleansing soiled chips of synthetic plastics material, comprising the steps of washing the material in a washing liquid in a state of turbulence and retained in a vessel containing a straining plate down through which dirt removed from the material is filtered, and then passing the material through an atmospheric zone which is in a state of turbulence and subjecting the material to rinsing.

2. A method as claimed in claim 1, wherein, after the rinsing step, the chips are transported in a non-uniform manner of flow to an outlet of the vessel and are thereafter conveyed for further treatment in a continuous manner of flow.

3. A method as claimed in claim 1 or 2, wherein the period of time the washing step takes and the period of time it takes to pass the material through said atmospheric zone are controllably variable.

4. A method of cleansing soiled chips of synthetic plastics material, substantially as hereinbefore described with reference to Figure 1, with or without one or more of the modifications shown in Figure 2 of the accompanying drawing.

5. An apparatus for carrying out the method of cleansing claimed in claim 1, comprising a vessel having a strainer plate which is sloped to extend below and above a level of washing liquid in the vessel in use thereof, an outlet below said plate for removal of dirt, an inlet for the plastics material to be cleansed above a lower region of the plate and an outlet for the cleansed plastics material above an upper region of the plate, there being a rotatable shaft above and extending parallel to the plate, said shaft carrying fluid turbulence-causing means to act on and transport said material from below the liquid level to above it, and there being means to rinse the material when it is above the liquid level and when acted on by saici fluid turbulence causing means.

6. An apparatus as claimed in claim 5, wherein said fluid turbulence-causing means comprises a stirrer mechanism, which is intended to extend below said liquid level, and a worm intended to be above said liquid level to convey said material whilst it is being rinsed, and after it has been rinsed to an outlet of the vessel.

7. An apparatus as claimed in claim 6, wherein said stirrer mechanism comprises paddles connected to said shaft.

8. An apparatus as claimed in claim 7, wherein each paddle has a slope which is adjustable in order to adjust the period of time that the washing step takes.

9. An apparatus as claimed in claim 6, 7 or 8, wherein baffles are arranged between parts of the stirrer mechanism.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. a by-pass pipe 38 can be extended to the pipe 36. By regulating the air flow through the by-pass pipe 38, the quantity of liquid supplied to the pipe 36 can be reduced. A horizontally-extending cleansed material discharge duct 30 is arranged in the upper region of the shaft 26, with which duct 30 is associated a rotating filter or strainer drum 26. This drum is mounted on a shaft 28 (driving and mounting means for the shaft 28 not being shown). The strainer drum 26 is so arranged that it projects only slightly above the liquid level 29 and into the discharge duct 30. Liquid flowing from the duct 26 over the edge 45 flows over a surface 30a onto and into the drum 27. The cleansed chips are taken up from the surface 30a by the rotating surface of the strainer drum and are carried away from the liquid and thereby fed over a surface 30b to a discharge pipe 31. The surface 30a, over which the chips are fed onto the drum, is at a lower level than the surface 30b, over which the chips are fed to the discharge pipe 31. A pneumatic conveying arrangement (not shown) is connected to the pipe 31 and serves to extract the cleansed chips.The liquid which flows into the strainer drum 27 is extracted through a lateral opening 34 and fed to a liquid-discharge pipe 33. Pipe connections may be so arranged that the liquid may from here be supplied from the liquid-discharge pipe 33 as circulation water to the pipe 36. The construction shown in Figure 1, because the container 40 is funnel-shaped, requires a considerable overall height. In order to reduce this height, the vessel may take the form shown in Figure 2 in which a trough 41 is provided beneath the strainer plate 2, the trough receiving a conveyor screw 42 which acts to feed the dirt and sludge filtering through the filter plate 2 to the outlet 39. The screw 42 may be driven through a driving arrangement 43 from the screw shaft 4. It will be appreciated that, instead of providing a stirrer mechanism 8 in the form shown the strainer plate may be in the form of a sieve-like vibratory channel, in which case the strainer plate 2 would consist of a U-shaped channel or duct, of which the bottom surface is in the form of a screen or sieve. The complete unit is suspended in an arrangement inside the trough 1 and is driven with an unbalanced motor. Accordingly, the chips are conveyed through the strainer by vibrations, so that the effect is the same as with the constructions illustrated. Thus, in this case also, the dirt adhering to the soiled plastics chips is initially softened below the liquid level, is mechanically detached above the liquid level and is then washed out in the sprinkler zone. WHAT WE CLAIM IS:

1. A method of cleansing soiled chips of synthetic plastics material, comprising the steps of washing the material in a washing liquid in a state of turbulence and retained in a vessel containing a straining plate down through which dirt removed from the material is filtered, and then passing the material through an atmospheric zone which is in a state of turbulence and subjecting the material to rinsing.

10. An apparatus as claimed in any one of claims 5 to 9, wherein said means to rinse the

material comprises spray nozzles.

11. An apparatus as claimed in any one of claims 5 to 10, wherein said vessel is in the form of a trough which is pivotally mounted at one end, a height-adjustment device being provided to lower or raise the trough by swinging it about this pivot.

12. An apparatus as claimed in any one of claims 5 to 11, wherein means are provided to control the supply of the soiled chips of synthetic plastics material to the vessel.

13. An apparatus as claimed in claim 12, wherein said means to control the supply of soiled chips is in the form of a conveyor screw provided within said inlet.

14. An apparatus as claimed in any one of claims 5 to 13. wherein a device is provided in the region where the soiled chips of synthetic plastics material are introduced to the washing liquid, this device comprising a weir to trap floating foreign bodies which have been washed off the chips and a discharge pipe for removal of these foreign bodies.

15. An apparatus as claimed in any one of claims 5 to 14, wherein a discharge device arranged for continuously feeding the chips to a drying stage is positioned beyond an outlet of the vessel.

16. An apparatus as claimed in claim 15, wherein said discharge device comprises a hollow vertical shaft situated immediately beneath said vessel outlet and arranged to be filled with a liquid, into which the chips fall in use of the apparatus, this shaft being provided to separate any remaining dirt from the chips, the discharge device further comprising a rotatable filler or strainer drum having a horizontal axis and being disposed adjacent said hollow shaft so that part of it projects, in use, above the liquid level in said hollow shaft so that the chips can overflow from said hollow shaft onto the face of said drum to drain thereon.

17. An apparatus as claimed in claim 16, wherein means are provided to collect liquid drained through said drum and to recirculate this liquid into said hollow shaft.

18. An apparatus as claimed in claim 16 or 17, wherein an overflow edge for said hollow shaft adjoins a surface over which surplus liquid and the chips from the hollow shaft can pass to reach the surface of said drum, the said surface being at a lower level than a further surface over which the chips are fed from the drum after draining.

19. An apparatus as claimed in any one of claims 15 to 18 and further comprising a pneumatic conveying arrangement provided to extract the cleansed chips from said discharge device.

20. An apparatus as claimed in any one of claims 15 to 19, wherein said hollow shaft is provided with means to maintain an upwardly-directed flow of liquid within it.

21. An apparatus as claimed in claim 20, wherein said means for maintaining an upwardly-directed flow of liquid within said hollow shaft comprises a liquid supply pipe capped by an upwardly-directed strainer hood.

22. An apparatus as claimed in claim 20 or 21 and further comprising an air supply which is supplied directly into said hollow shaft and/or into said means for maintaining an upward-directed flow of liquid. in the latter case air being discharged with the liquid in use of the apparatus.

23. An apparatus as claimed inany one of claims 5 to 22, wherein said vessel is funnel-shaped to provide a dirt collecting chamber at the base of which said outlet below said plate is provided.

24. An apparatus as claimed in any one of claims 5 to 23, wherein said outlet below said plate is provided with a valve for control of discharge through the outlet.

25. An apparatus as claimed in any one of claims 5 to 22, wherein the vessel beneath said strainer plate is in the form of a trough which receives a conveyor screw which acts to feed dirt and sludge filtering through the strainer plate to said outlet below said plate.

26. An apparatus as claimed in claim 25. wherein said conveyor screw in said trough is operably connected through a driving arrangement from said rotatable shaft.

27. An apparatus for carrying out the method of cleansing claimed in claim 1, 2 or 3, substantially as hereinbefore described with reference to Figure 1, with or without one or more of the modifications shown in Figure 2 of the accompanying drawing.