THERMOKINETIC MIXER FOR MELT-MIXING WASTE PLASTIC PRODUCTS

Abstract

A thermokinetic mixer for melt mixing plastics waste includes a housing enclosing a mixing chamber, and a shaft protruding through the mixing chamber and connectable to a drive unit. In the mixing chamber, Y-shaped mixing blades protrude radially from the shaft, wherein the free end of the mixing blades protruding into the mixing chamber is cuboid, and the end opposite the free end of the mixing blades has two legs in each case having at least one through bore. The shaft has polygonal recesses, in which recesses the legs can be fastened by a fastener protruding through the through bores.

Claims

1. A thermokinetic mixer (1) for melt mixing plastics waste, comprising a housing (2) enclosing a mixing chamber (10), a shaft (6) protruding through the mixing chamber (10) and connectable to a drive unit and Y-shaped mixing blades (15) protruding radially from the shaft (6) in the mixing chamber (10), wherein the free end of the mixing blades protruding into the mixing chamber (10) is cuboid, and the end opposite the free end of the mixing blades (15) has two legs in each case having at least one through bore (22), wherein polygonal recesses (16) are provided in the shaft (6), in which recesses the legs (20) can be fastened by means of fastening means (17) protruding through the through bores (22).

2. The thermokinetic mixer (1) according to claim 1, wherein the mixing blades (15) are made from hard steel, chilled cast iron, Hardox or a combination thereof.

3. The thermokinetic mixer (1) according to claim 1, wherein the legs (20) of the mixing blades (15) form a wedge-shaped recess (21).

4. The thermokinetic mixer (1) according to claim 1, wherein the shaft (6) is designed so as to be round at least in portions.

5. The thermokinetic mixer (1) according to claim 1, wherein the shaft (6) is designed to be polygonal at least in portions and the recesses encompass surfaces of the polygonal portions.

6. The thermokinetic mixer (1) according to claim 1, wherein, in each of the surfaces of the polygonal portions, at least one bore is provided for receiving a fastening means (17) protruding through the mixing blades (15).

7. The thermokinetic mixer (1) according to claim 1, wherein cooling is provided in the housing (2).

8. The thermokinetic mixer (1) according to claim 1, wherein a wall of the housing (2), which wall forms the mixing chamber (10) and can be brought into contact with the mix material, comprises a wear plate made in particular from hard steel, chilled cast iron, Hardox or a combination thereof.

9. The thermokinetic mixer (1) according to claim 1, wherein the mixing blades (15) are arranged in the mixing chamber (10) in such a way that their base surfaces (24) lie in a plane aligned transversely to the shaft (6).

10. The thermokinetic mixer (1) according to claim 1, wherein the mixing blades (15) are arranged on the shaft (6) in such a way that adjacent mixing blades (15) are arranged so as to be offset by 90° from one another.

11. The thermokinetic mixer (1) according to claim 1, wherein the mixing blades (15) are provided in the mixing chamber (10) so as to be arranged one behind the other in rows and the base surfaces (24) of the mixing blades (15) are aligned parallel to one another.

12. The thermokinetic mixer (1) according to claim 1, wherein the mixing chamber (10) is cylindrical and comprises a mixing trough (13) and a mixing chamber cover which can be fastened to the mixing trough (13).

13. The thermokinetic mixer (1) according to claim 1, wherein the mixing trough (13) has an openable flap through which the mix material can be discharged.

14. The thermokinetic mixer (1) according to claim 1, wherein the housing (2) comprises at least three side walls (3, 4, 5) arranged axially one behind the other, which walls are aligned substantially parallel to one another and can be fastened to a housing base plate aligned substantially perpendicularly to said walls.

15. The thermokinetic mixer (1) according to claim 1, wherein the first side wall (3) and the second side wall (4) form side walls of the mixing chamber (10).

16. The thermokinetic mixer (1) according to claim 1, wherein a feed chamber (11) is connected upstream of the mixing chamber (10).

17. The thermokinetic mixer (1) according to claim 14, wherein the feed chamber (11) has an opening (12) on its upper side for feeding mix material.

18. The thermokinetic mixer (1) according to claim 1, wherein the first side wall (3) and the second or third side wall (4, 5) each have a bearing (9) for supporting the shaft (6).

Description

[0030] The invention is explained in more detail below using an embodiment of the invention which is shown in the drawing, in which:

[0031] FIG. 1 is a perspective view of a preferred embodiment of a mixer,

[0032] FIG. 2 is a perspective view of a shaft,

[0033] FIG. 3 is a perspective view of a shaft with mixing blades,

[0034] FIG. 4 is a perspective view of a mixing blade and

[0035] FIG. 5 is a further perspective view of a mixing blade with fastening means.

[0036] FIG. 1 shows a perspective view of a preferred embodiment of a mixer. The mixer 1 is designed as a thermokinetic mixer 1. The housing 2 of the mixer 1 has three side walls 3, 4, 5 which are aligned parallel to one another and are arranged one behind the other, each of which has an opening for a shaft 6 protruding through the side walls 3, 4, 5. The side walls 3, 4, 5 can be fastened in a simple manner to a base plate (not shown). For fastening to the base plate, a flange 7 with bores 8 can be provided.

[0037] The shaft 6 can be operatively connected to a drive unit, for example via a shaft coupling. A gear motor in foot, flange or slip-on design can be used as the drive. The use of an electro-hydraulic drive or a pure electric motor is also possible.

[0038] The shaft 6 is secured by bearings 9 fitted into the openings in the first side wall 3 and third side wall 5. Due to the short construction and the small distance between the bearings, vibrations of the shaft 6 can be minimised and a high level of flexural rigidity is achieved. Depending on the embodiment, the bearings 9 can also be arranged in the openings in the first side wall 3 and second side wall 4, so that the bearing spacing is shortened again, which has a positive effect on the flexural rigidity of the shaft 6.

[0039] The first side wall 3 and the second side wall 4 of the housing 2 can at the same time form side walls of a mixing chamber 10.

[0040] A cylindrical feed chamber 11, which is enclosed by the second and third side walls 4, 5, is arranged adjacent to the mixing chamber 10. On the upper side, the feed chamber 11 has a duct-shaped opening 12, via which the mix material can be introduced into the feed chamber 11. The feed chamber 11 can be arranged horizontally, wherein the feed chamber 11 can also be inclined. The feed chamber 11 can have different sizes depending on the delivery rate and can be made from stainless steel, for example. For conveying the mix material from the feed chamber 11 into the mixing chamber 10, a conveying means (not shown) is provided in the feed chamber 11. This can be, for example, a worm conveyor which has a worm thread firmly connected to the shaft 6. The worm thread can be welded to the shaft 6, connected thereto via webs or manufactured in one part with the shaft 6. Alternatively, the worm conveyor can be fastened to a sleeve, which in turn can be slipped onto the shaft 6. The sleeve can in turn be connected to the shaft 6 by means of screws or in some other way. Instead of a worm conveyor, a spiral conveyor without a shaft can also be used. In this embodiment, the bearings 9 of the shaft 6 would have to be integrated in the first side wall 3 and the second side wall 4. The worm thread can be designed as a full-blade worm with a continuous thread, as a band thread or as a blade worm.

[0041] The mix material is conveyed from the feed chamber 11 through the opening in the second side wall 4 into the mixing chamber 10 connected downstream of the feed chamber 11. For the embodiment that the shaft 6 is secured by bearings provided in the first and second side walls 3, 4, the feed chamber 11 can, for example, be arranged at an angle so that mix material falls into the mixing chamber 10 by gravity. Alternatively, a conveying means can be provided that conveys the mix material from the feed chamber 11 through an opening in the side wall 4 into the mixing chamber 10, for example a slide.

[0042] The mixing chamber 10 is designed so as to be cylindrical and comprises a mixing trough 13 and a mixing chamber cover (not shown), which are fastened to one another via a flange connection 14. The mixing chamber 10 can also be designed in one piece, in which case an opening that can be closed with a closure means can be provided in the upper side of the mixing chamber 10 so that the mixing chamber 10 is accessible. An opening (not shown) is integrated in the mixing trough 13 and can be closed with a closure means, for example a cover. The opening and closing of the opening in the mixing trough 13 can take place automatically or manually. Mix material can be removed through the opening in the mixing trough 13. In the mixing chamber 10, sensors can be provided which, for example, determine the temperature of the mix material.

[0043] The shaft 6 protruding through the mixing chamber 10 preferably rotates about the axis of the mixing chamber 10. As shown in FIG. 1 and also in FIG. 2, the shaft 6 is designed so as to be multi-sided or polygonal in portions and can have different shaft diameters. For example, a shaft portion in the feed chamber 11 can have a larger shaft diameter than a shaft portion in the mixing chamber 10.

[0044] As can be seen in FIGS. 1 and 3, mixing blades 15 are arranged on the shaft 6 and extend radially from the shaft 6 protruding through the mixing chamber 10. The number of mixing blades 15 can be varied depending on the application. The mixing blades 15 can consist of Hardox, for example. As shown in FIG. 2, the shaft 6 has recesses 16 which are designed to be polygonal, i.e. in which polygonal portions are provided and which are used to receive the mixing blades 15. The mixing blades 15 can be fastened in the bores 18 by means of fastening means 17. The recesses 16 can be milled into a round shaft, for example.

[0045] In the embodiment according to FIG. 2, the shaft 6 has square recesses 16, between which annular portions 19 are provided which can arise through a non-machined region of the shaft 6. The width of the annular portions 19 can be varied depending on the application and, for example, correspond to the width of the recesses 16 or be a multiple thereof. It can also be provided that there are no annular portions between the recesses 16. Two oppositely arranged mixing blades 15 can be fastened in the square recesses 16.

[0046] As can be seen in FIG. 4 and FIG. 5, the mixing blades 15 are Y-shaped and have two legs 20 which, for example, are at an angle of 90° to one another and thereby form a wedge-shaped recess 21.

[0047] The wedge-shaped recess 21 is designed in such a way that it fits flush into the recess 16 of the shaft 6. In other words, the width and length of the legs 20 are adapted to the width and length of the polygonal recesses 16. A square recess 16 comprises in particular four surfaces which can be brought into contact with contact surfaces of the legs 20. For fastening the mixing blades 15 into the recesses 16, fastening means 17 can be used, which fastening means are screwed through through bores 22 provided in the legs 20 and are screwed to the bores 18 in the recesses 16, as shown in FIG. 4, for example. The through bores 22 are designed to be coaxial with the bores 18 in the recesses 16. In particular, two mixing blades 15 can be fastened diametrically to a square recess 16, the fastening being carried out in such a way that the leg ends of the mixing blades 15 fastened opposite each other do not exert any pressure on one another. This can be achieved, for example, in that there is still a free space between the leg ends of the opposing mixing blades 15.

[0048] The mixing blades 15 are cuboid and can have straight or inclined longitudinal sides 23. It can be advantageous if the mixing chamber 10 comprises a combination of different mixing blades 15, for example with mixing blades 15 with inclined and straight side surfaces 23. In addition, they can be designed to be slightly tapered, i.e. the narrow side 25 provided at the free end of a mixing blade 15 is designed to be slightly wedge-shaped. The narrow side can also run straight.

[0049] The base surfaces 24 of a mixing blade 15 are preferably located in a plane aligned transversely axially to the longitudinal axis of the shaft 6. In addition, the base surfaces 24 of the mixing blades 15 provided in the mixing chamber 10 are parallel to one another, so that basically the base surface 24 of one mixing blade 15 is opposite the base surface 24 of the next-but-one mixing blade 15. The mixing blades 15 arranged in adjacent recesses 16 are advantageously offset from one another at an angle of 90°. This results in, for example, four rows of mixing blades 15 arranged one behind the other in the mixing chamber 10, the rows being at an angle of 90° to one another, as shown in FIG. 3. In the embodiment shown, the mixing blades 15 of every third recess 16 are opposite one another.

[0050] In order to prevent the rotating mixing blades 15 from rubbing against the side walls 3, 4, a spacer sleeve which is pushed onto the shaft 6 can be arranged on each of the shaft ends provided in the mixing chamber 10.

[0051] The mixer 1 is used as a thermokinetic mixer 1. Substantially any plastics waste including, for example, mixed plastics material, polymer mixtures, thermoplastics, and thermoset waste materials can be used. After the melt mixing using the mixer 1, the compound can be discharged from the mixer 1 and processed in further steps to usable products, such as railway sleepers. The plastics parts are introduced into the feed chamber 11 through the opening 12. The introduced plastics parts then reach the mixing chamber 10 using a conveying means. The speed of rotation of the shaft 6 can vary from below 1500 revolutions per minute to over 4000 revolutions per minute. The choice of shaft rotation speed depends on the plastics parts and process parameters used.

[0052] Due to the rapidly rotating shaft 6 and consequently the mixing blades 15, the plastics parts are mixed and comminuted. On the one hand, the plastics parts are sheared by the mixing blades 15 rotating rapidly with the shaft 6. On the other hand, there are collisions between plastics parts, between plastics parts and the mixing blades 15, and between plastic parts and the inner wall of the mixing chamber 10. This results in the heating and melting of the plastics parts, so that a melted mixture of the plastics parts is created. Depending on the plastics parts introduced, the process parameters are selected in such a way that the process is stopped after a defined process time or when a defined temperature is reached. The melt-mixed material can be removed from the mixing chamber 10 via an opening arranged on the underside of the mixing trough 13 and designed as an outlet opening. Since the mix material is in a viscous state, it is possible for the mix material to flow out through the opening. The mix material can be removed from the mixing chamber 10 during operation, i.e. while the shaft 6 is rotating, it being advantageous to reduce the speed of rotation. At the same time, new mix material can be fed from the feed chamber 11 to the mixing chamber 10 with the aid of the conveying means.

[0053] A substantial advantage of the invention is that, for example, for maintenance of the shaft 6 or the mixing blades 15, the housing cover can be removed and the mixing blades 15 can be exchanged simply by loosening the fastening means 17. This allows individual mixing blades 15 to be exchanged in a simple manner. In addition, only a few fastening means 17 for fastening to the shaft 6 are necessary for the Y-shaped mixing blades 15 with the legs 20. Furthermore, the mixing blades 15 can be turned over; in other words, if, for example, one side, in particular a base surface 24, of a mixing blade 15 is damaged or worn, the mixing blade 15 can be turned around and used again.