GB1601568A

GB1601568A - Material feed device and plastics recovery installation including such device

Info

Publication number: GB1601568A
Application number: GB4763777A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-05-25
Filing date: 1978-05-25
Publication date: 1981-10-28

Description

(54) MATERIAL FEED DEVICE AND PLASTICS RECOVERY INSTALLATION INCLUDING SUCH DEVICE (71) I, JOHN ALBERT WARD, a British Subject of 15, Westfield Groove, Finchfield, Wofverhampton WV3 8EX, do hereby declare the invention, for which I pray that a patent may be granted to me, 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 material feed device and a plastics recovery installation, more particularly such a device and installation as described and claimed in my British Patent Application No. 51281/74, serial No. 1527714 filed 27th November 1974. The present invention concerns an improvement or modification of the invention described therein.

The feed device disclosed therein comprises a material receiving receptacle having a substantially flat bottom wall with a generally central outlet, a rotary scraper having at least one blade disposed within the receptacle adjacent to said outlet and so shaped and arranged that, during its rotational movement, it imparts to said material collected on the bottom wall of said receptacle a movement in direction towards the receptacle outlet, and a screw conveyor at said outlet through which said material is to be conveyed from the receptacle.Such a feed device is particularly suitable for incorporation in an installation for re-cycling scrap plastics material arising from a production process in which portions of said material are trimmed off to produce scrap strips such installation comprising means for collecting such scrap strip and feeding it through such a material feed device back into fresh raw material for said production purposes.

In use the scrap material is transferred by the screw conveyor from the receptacle into a hopper to be mixed with fresh plastics material which is itself to be fed into a production machine, typically the machine producing the product from which the scrap Is itself recovered.

In the arrangement described and illustrated in that earlier Application, the screw of the conveyor is arranged in a tube which terminates at a position somewhat above a discharge opening of the hopper and the screw itself extends beyond the end of the tube towards that opening. Thus, in use, the feed device delivers the recycled material to a position immediately adjacent the outlet of the hopper, where it is mixed with the fresh material and fed to the production machine.

Whilst this arrangement can work satisfactorily, I have found that certain difficulties can arise under some circumstances. In particular, the comminuted material, depending on its nature, tends to a greater or lesser degree to become compacted into a solid mass during its passage along the screw conveyor. In an extreme case it can become so firmly compacted as to prevent further rotation of the screw. More commonly, the degree of compaction is such that the recycled material simply binds together and fails to mix uniformly with the fresh material. This can lead to a plug or core of recycled material coming from the end of the conveyor and being fed straight into the outlet so as, in some cases, substantially to prevent the fresh material flowing into the outlet. This can lead to an undesirably high concentration of recycled matenal being fed into the process machine at times.

In accordance with the present invention these drawbacks are overcome by providing at the lower end of the screw a deflector which acts to cause the material delivered by the screw to be dispersed outwardly away from the latter. In this way, the recycled material cannot flow directly to the outlet and has a greater opportunity to mix with the fresh material in the hopper.

In the above-described installation, the screw is accordingly terminated at a position which is spaced at a substantial distance above the hopper outlet and, as a result, since the length of the screw conveyor may be less than it would otherwise have been, the risk of the recycled material becoming compacted with the tube can be reduced.

A stirrer may additionally be provided to assist dispersion of the recycled material within the fresh material, and conveniently such stirrer may be mounted on a common shaft with the screw.

In addition to, or instead of, such a stirrer it is preferred to provide at a position close to the outlet of the hopper an agitator to prevent, or at least reduce the incidence of, "bridging" by the material at.

the mouth of the outlet.

The invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a general schematic view of an installation including a feed device in accordance with the invention, and Figure 2 is a view taken along the line A-A of Figure 1.

Referring to the drawings, these show a feed device comprising a receptacle 1 of generally cylindrical shape having a tangentially disposed inlet 2 through which is fed, at high velocity e.g. several thousand feet per minute (typically 3,000 fpm) in the direction of the arrow Y (Figure 2), a stream of air in which is entrained material such as waste plastics or granules. An outlet 3 is formed in a substantially flat bottom wall la of the receptacle and a screw conveyor 6 is provided at the outlet. The conveyor 6 includes a discharge tube 4 which may, as shown, include an inlet portion 5 of relatively larger diameter, and a screw 7.

The bottom wall la is desirably formed with a plurality of radial ribs 3a. The screw 7 is rotated by a shaft 8 from a motor 9 through a gear box 10 which is disposed above the receptacle. Rotation of the screw moves material from the outlet 3 along the discharge tube 4 in the direction of the arrow X (Figure 1). As can be seen from Figure 1, the screw 7 extends into the receptacle 1 for a short distance and the screw conveyor 6 extends into a hopper 15 which is disposed beneath the receptacle 1.

The shaft 8 also carries a scraper or feeder blade 11 which, as will be seen more clearly from Figure 2, is of curved configuration in a plane parallel to the adjacent bottom wall of the receptacle and extends transversely of the shaft from its connection therewith so that its free end 12 is adjacent to the side wall of the receptacle.

At the upper end of the receptacle a top wall lb affords a central opening 2a and supports a concentric skirt 13 extending downwardly to form an exhaust for air separated from the incoming stream.

In operation, the shaft rotates in the direction indicated by arrow F (Figure 2) and drives the screw 7 and feeder blade 11 at the same rate. A mixture of air and finely divided plastics material is introduced through the inlet 2 at high velocity and swirls around the space between the side wall of the receptacle 1 and the skirt 13. As the velocity of the mixture decreases, the solid material tends to fall towards the bottom wall of the receptacle, whilst the air is allowed to escape upwardly through the skirt 13.

The latter preferably, as shown, includes an internal rib or web 14 of spiral configuration extending upwardly in a direction counter to the direction in which the stream of air is projected into the receptacle through the inlet 2. Such rib or web affords a barrier to the upward movement of the air to reduce its velocity still further and thereby assist in the separation of any articles still entrained therein.

In this way, the plastics material is separated from the air and falls onto the bottom wall la of the receptacle. The feeder blade 11 is spaced slightly above said bottom wall so as to clear the ribs 3a. The direction of rotation of the blade 11 is such that its concave face constitutes the forward edge thereof and this serves to gather the plastics material resting on the bottom wall la and scoop it towards the outlet 3. The radial ribs 3a assist by reducing any tendency for the blade to sweep the material circumferentially around the receptacle. The material on the bottom wall la is fed towards the screw 7 where it protrudes through the outlet 3.

Conveniently, as shown, the screw 7 extends up to the upper edge of the blade 11.

The rate of rotation of the screw is relatively slow, typically about 70 rpm so as not unduly to disturb the air within the receptacle, but is fast enough to ensure that the material is swept from the bottom wall of the receptacle at substantially the same rate at which it accumulates. This avoids the problem encountered in previous installations, when substantial quantities of such material are stored in a hopper, because the material tends to "bridge" and not flow freely under gravity even when agitated in some way.

As can be seen, the discharge tube 4 which leads from the receptacle 1 terminates at a position which is spaced at a substantial distance above the outlet opening 15a of the hopper 15. The screw 7 extends somewhat beyond the lower end of the tube 4, and an extension 8a extends downwardly beyond the end of the screw and up to the outlet opening 15a. Adjacent the lower end of the screw 7, the shaft 8a carries a deflector 7a in the form of a frustoconical mixing head with curved outwardly extending ribs 7b on its upper surface.

These ribs engage the material which is fed down the screw conveyor 6 and positively displace such material outwardly away from the shaft. This firstly tends to brake up any conglomerations of the material leaving the tube 4, and secondly disperses such material outwardly into material already within the hopper 15, the latter having a main infeed opening 17 adjacent to the receptacle 1 for reception of material with which the material delivered by the screw conveyor is to be mixed within the hopper.

If desired, the shaft 8a may carry at a position beneath the deflector 7a one or more stirrers designed to improve mixing of the two materials. Whether or not such stirrers are provided, it is preferred to provide at the lower end of the shaft 8a an agitator 8b which, as shown, may simply take the form of one or more rods bent so that the ends thereof lie in spaced parallel relation to the side wall of the hopper 15 adjacent to the outlet 15a thereof. The agitator 8h serves to prevent the material "bridging" at the mouth of the outlet 15a, as might otherwise happen as a result of compaction of the material by virtue of gravitational compression.However, it is not intended that the agitator 8b should in any way urge the mixed material into the outlet -15a and indeed a further advantage of the present invention is that no force, other than gravitational, is applied to the material during its passage through the outlet, thereby reducing the risk of compaction of material in the outlet.

In use, the feed device and hopper shown in the accompanying drawings may be incorporated into a plastics recovery installation in which scrape plastics trimming from a production process is recycles and mixed with fresh raw material for that process. Thus, the recycled scrap material, after suitable comminution may be fed into the inlet 2 and the receptacle I and fresh raw material in substantially larger amounts may be fed into the hopper 15 through the main infeed opening 17.

Normally, the level of material in the hopper 15 will be at least up to, und usually above, the screw conveyor outlet. Thus, the scrap material delivered by the conveyor 6 is able to disperse in the fresh material as it flows gravitationally through the hopper towards the production machine connected to the outlet 15a.

Whilst the blade 11, screw 7, deflector 7a and agitator 8h are conveniently carried on a common shaft driven by the motor 9, it would be possible for the deflector and agitator to be carried by a separately driven shaft. Alternatively, the deflector 7a could be carried bv the tube 14 so as to be nonrotatable.

WHAT I CLAIM IS: 1. A material feed device comprising a material receiving receptacle having a substantially flat bottom wall with a generally central outlet, a rotary scraper having at least one blade disposed within the receptacle adjacent to said outlet and so shaped and arranged that, during its rotational movement, it imparts to said material collected on the bottom wall of the receptacle a movement in a direction towards the receptacle outlet, and a vertically disposed screw conveyor at said outlet through which material is to be conveyed from the receptacle, a deflector being arranged adjacent to the lower end of the screw conveyor to cause material delivered by the screw conveyor to be dispersed outwardly from the latter.

2. A material feed device according to Claim 1 wherein the deflector is spaced below the outlet end of a tube within which the screw of the screw conveyor is enclosed.

3. A material feed device according to Claim 2 wherein the screw of the screw conveyor extends beyond the end of the tube and to the deflector.

4. A material feed device according to any one of Claims 1 to 3 wherein the deflector is rotatable about an axis coincident with that of the screw of the screw conveyor.

5. A material feed device according to Claim 4 wherein the deflector and the screw of the screw conveyor are driven by a common drive shaft at the same rate.

6. A material feed device according to Claim 5 wherein the scraper is also driven by said common drive shaft.

7. A material feed device according to any one of Claims 1 to 6 wherein said drive shaft extends downwardly beyond the deflector and carries a laterally extending agitator at its lower end.

8. A material feed device according to Claim 7 wherein said agitator includes at least one pair of arms which are inclined upwardly away from the end of the drive shaft.

9. A material feed device according to any. one of Claims 1 to 8 wherein said receptacle is provided with an inlet through which said material can be delivered from a pipe along which it is conveyed by a flow of air, the receptacle having a skirt disposed generally centrally therein between said inlet and an air outlet arranged to act as an exhaust for air separated from a stream of air/material mixture entering the receptacle through said inlet.

10. An installation as claimed in Claim 14 of Application No. 51281/74 (Serial No.

1,527,714) wherein said material feed device comprises a device as claimed in any one of the preceding claims herein.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. These ribs engage the material which is fed down the screw conveyor 6 and positively displace such material outwardly away from the shaft. This firstly tends to brake up any conglomerations of the material leaving the tube 4, and secondly disperses such material outwardly into material already within the hopper 15, the latter having a main infeed opening 17 adjacent to the receptacle 1 for reception of material with which the material delivered by the screw conveyor is to be mixed within the hopper. If desired, the shaft 8a may carry at a position beneath the deflector 7a one or more stirrers designed to improve mixing of the two materials. Whether or not such stirrers are provided, it is preferred to provide at the lower end of the shaft 8a an agitator 8b which, as shown, may simply take the form of one or more rods bent so that the ends thereof lie in spaced parallel relation to the side wall of the hopper 15 adjacent to the outlet 15a thereof. The agitator 8h serves to prevent the material "bridging" at the mouth of the outlet 15a, as might otherwise happen as a result of compaction of the material by virtue of gravitational compression.However, it is not intended that the agitator 8b should in any way urge the mixed material into the outlet -15a and indeed a further advantage of the present invention is that no force, other than gravitational, is applied to the material during its passage through the outlet, thereby reducing the risk of compaction of material in the outlet. In use, the feed device and hopper shown in the accompanying drawings may be incorporated into a plastics recovery installation in which scrape plastics trimming from a production process is recycles and mixed with fresh raw material for that process. Thus, the recycled scrap material, after suitable comminution may be fed into the inlet 2 and the receptacle I and fresh raw material in substantially larger amounts may be fed into the hopper 15 through the main infeed opening 17. Normally, the level of material in the hopper 15 will be at least up to, und usually above, the screw conveyor outlet. Thus, the scrap material delivered by the conveyor 6 is able to disperse in the fresh material as it flows gravitationally through the hopper towards the production machine connected to the outlet 15a. Whilst the blade 11, screw 7, deflector 7a and agitator 8h are conveniently carried on a common shaft driven by the motor 9, it would be possible for the deflector and agitator to be carried by a separately driven shaft. Alternatively, the deflector 7a could be carried bv the tube 14 so as to be nonrotatable. WHAT I CLAIM IS:

1. A material feed device comprising a material receiving receptacle having a substantially flat bottom wall with a generally central outlet, a rotary scraper having at least one blade disposed within the receptacle adjacent to said outlet and so shaped and arranged that, during its rotational movement, it imparts to said material collected on the bottom wall of the receptacle a movement in a direction towards the receptacle outlet, and a vertically disposed screw conveyor at said outlet through which material is to be conveyed from the receptacle, a deflector being arranged adjacent to the lower end of the screw conveyor to cause material delivered by the screw conveyor to be dispersed outwardly from the latter.

11. An installation according to Claim 10

wherein the screw conveyor has its lower end disposed within the interior of a hopper having an outlet and an infeed opening for the reception of fresh raw material, the lower end of the screw conveyor being spaced at a substantial distance above the hopper outlet.

12. An installation comprising a material feed device according to Claim 1 arranged above a hopper with the screw conveyor extending downwardly into the hopper and with the lower end of the screw conveyor spaced at a substantial distance above an outlet which is provided at the base of the hopper, the hopper also affording an infeed opening adjacent to said feed device for the reception of further material with which the material delivered by the screw conveyor is to be fixed within the hopper.

13. An installation according to Claim 12 wherein the deflector is spaced below the outlet end of a tube within which the screw of the screw conveyor is enclosed.

14. An installation according to Claim 13 wherein the screw of the screw conveyor extends beyond the end of the tube and to the deflector.

15. An installation according to any one of Claims 12 to 14 wherein the deflector is rotatable about an axis coincident with that of the screw conveyor.

16. An installation according to Claim 15 wherein the deflector and the screw of the screw conveyor are driven by a common drive shaft at the same rate.

17. An installation according to Claim 16 wherein the scraper is also driven by said common drive shaft.

18. An installation according to Claim 17 wherein said drive shaft extends downwardly beyond the deflector to the outlet of the hopper and carries a laterally extending agitator at its lower end.

19. An installation according to Claim 18 wherein said agitator includes at least one pair of arms which are inclinded upwardly away from the end of the drive shaft so as to extend from the hopper outlet and generally parallel to the sides of the hopper adjacent tq the outlet.

20. An installation according to Claim 12 substantially as hereinbefore described with reference to and as shown in the accompanying drawings.