DE10000938A1 - Mixing unit for plastic melts has a rotor with alternating mixing and dividing rings, one having a groove system connecting axially with a bore system in the other - Google Patents

Abstract

A housing(3) has a rotor(4) with a ring assembly(5) forming alternating mixing(15) and dividing rings(16). At the periphery of the mixing rings are axial mixing grooves(19) forming a groove system(17). A bore system(18) in the dividing rings(16) has bores(20) connecting axially with the mixing grooves to divert and divide the melt flow during transfer from mixing grooves to the bores.

Description

The invention relates to a device for mixing a plastic melt according to the preamble of claim 1.

Such a device for mixing a polymer melt Homogenization and / or the admixture of additives is from the US 4,128,342 known.

In the known device, a rotor is rotatable in a housing arranged. On the circumference of the rotor and on the inner wall of the housing introduced a groove system, the grooves partially overlap. As a result, the melt passes alternately from the grooves of the rotating Groove system in the rotor in the grooves of the fixed groove system of the housing and vice versa. This creates an intensive distribution or mixing the melt reached. With such a design of the mixer, this is not rotating groove system in the housing is relatively complex to manufacture. The Relative movement between the groove systems causes shearing of the Melt flow and thus a resulting temperature increase in the melt.

The invention is based on the object, the mixer mentioned to develop in such a way that while maintaining the achievable quality of Mixing results as little warping as possible. Another one The aim of the invention is to provide a dynamic mixer with the simplest possible Creating structure.  

This object is achieved by a mixer with the features of claim 1 solved.

In the known mixer, the rotating groove system is circumferential in one of the rotor arranged ring pack introduced. The ring package consists of several mixing rings arranged alternately one behind the other and Dividing rings. In the mixing rings there are several axial mixing grooves on the circumference introduced, which are each interrupted by the dividing rings. According to the invention, the dividing rings have a plurality of bores Form the bore system in the ring package, which together with the groove system allow migration through the melt. This is a melt flow deflected and divided at the transition from the mixing grooves to the bores. There the groove system and the bore system none according to the invention Executing relative movement to each other is the one to be performed by the rotor Shear work particularly low. The mixing device is therefore particularly suitable for Suitable cases in which a polymer or an additive is added essentially constant melt temperature must take place.

For current sharing, it is proposed that the mixing grooves be adjacent Mixing rings each through at least two holes in the between the Mixing rings arranged dividing ring are connected. Here is a particularly favorable distribution achieved in that the melt flow starting from a mixed groove through the two holes in two separate Mixing grooves of an adjacent mixing ring is performed. In cases where a Homogenization of the melt is desired, the melt flow can be also advantageously lead from the two holes into a common mixing groove.

In a particularly advantageous development of the invention, this is Hole system introduced by several on the circumference of the dividing rings Longitudinal grooves expanded. There is a mixed groove for melt flow division in axial direction each have a longitudinal groove and at least one of the bores  assigned. This allows an even better redistribution of the melt during Walking through the ring packet can be achieved.

The longitudinal grooves are advantageously uniform on the circumference of the dividing rings distributed, with two axially aligned depending on the course of the longitudinal grooves consecutive mixing grooves of adjacent mixing rings or two at an angle opposite mixing grooves of adjacent mixing rings are connected.

To ensure that a sufficient distribution of the melt flow at Every transition from a mixed groove is initially carried out, it is proposed free flow cross-section of the longitudinal grooves smaller than the free Flow cross section of the mixing grooves.

To get a further improvement in the distribution of the melt flow is the training is particularly advantageous, in which the longitudinal grooves of a Graduation ring by a circumferential groove on the circumference of the graduation ring are interconnected. It is particularly advantageous if the transverse groove runs obliquely over the surface line of the graduation ring, so that by rotating the Ring package a promotional effect can be achieved.

In a particularly advantageous development of the invention The holes in the drilling system are in each device Circumferential direction offset from the mixing grooves of the groove system. The Connection between the holes and the mixing grooves are through additional inclined grooves on the end faces of the mixing rings manufactured. This will further improve the distribution of the melt reached.

In order to spread the melt currents as much as possible when dividing the current to obtain the oblique grooves on the opposite end faces of a  Mixing ring arranged to a mixing groove that in the side projection Angle between the oblique grooves is included.

In order to avoid dead spaces, it is proposed to use a groove semicircular cross section. In particular, it can also be used achieve easy manufacture of the groove system.

In a particularly advantageous development of the invention The drilling system consists of holes in the dividing rings and Bores formed in the mixing rings. The groove system also consists of Mixing grooves in the mixing rings and mixing grooves in the dividing rings. Here the dividing rings and the mixing rings are arranged alternately in such a way that an alternating bore and a mixed groove face each other. By a ring packet formed in this way ensures that with each transition from a mixing ring to a dividing ring and vice versa a melt division as well as a melt deflection. This will make it even better Mixing of the melt reached. The dividing rings and mixing rings can advantageously be identical, being offset in relation to one another Ring packet are arranged. The mixing rings point to the circumference evenly distribute mixing grooves in which on the end faces introduced oblique grooves open. In addition, between the ends of the Oblique grooves each have a hole drilled in the mixing rings. The Dividing rings are identical to the mixing rings. The ring packet will now put together in such a way that each an oblique groove end of a mixing ring corresponds to a hole in the adjacent dividing ring and vice versa. The mixing grooves formed on the circumference of the mixing rings can both run parallel as well as diagonally to the end faces to ensure an optimal To get mixing.

Further advantageous developments of the invention are in the subclaims Are defined.

The invention will now be described with reference to the accompanying drawings described in more detail using some exemplary embodiments.

They represent:

FIG. 1 shows a mixing device according to the invention at the outlet of an extruder;

FIG. 2 shows an exemplary embodiment of a mixing ring of the ring packet from FIG. 1;

Fig. 3 shows an embodiment of a partition ring of the ring stack of Fig. 1. In Fig. 1, an embodiment of the device according to the invention is shown in cross-section schematically. Here, the mixer 1 is arranged immediately afterwards at the outlet of an extruder 2 . The cylinder of the extruder is denoted by 6 and the extruder screw having the helical screw flight 8 is denoted by 7 .

The mixer 1 consists of a rotor 4 which has a threaded shoulder 13 at one end. The threaded neck 13 is screwed to the extruder screw 7 , so that the rotor 4 is driven directly by the extruder screw 7 . The rotor 4 is concentrically enclosed by a housing 3 . The housing 3 of the mixer is connected to the cylinder 6 of the extruder 7 by a flange 14 . A ring package 5 is arranged on the circumference of the rotor 4 . The ring packet 5 consists of a plurality of mixing rings 15 and dividing rings 16 . The mixing rings 15 and the dividing rings 16 are alternately joined together to form the ring packet 5 . The ring packet 5 is connected in a rotationally fixed manner to the rotor 4 via a feather key 11 . By means of a bracing element 10 fastened to the free end of the rotor 4 , the ring packet 5 is braced axially against a shoulder 9 at the opposite end of the ring packet 5 on the rotor 4 . For this purpose, the rotor 4 is connected to the bracing element 10 via the threaded shoulder 12 .

On the inlet side, the ring packet 5 is delimited by an inlet ring 24 opposite the outlet of the extruder. An annular inlet chamber 26 is formed between the housing 3 and the ring pack 5 by the outlet ring 24 . The inlet ring 24 has a plurality of distributed holes 25 on the circumference, which connects the inlet chamber 26 with a groove system 17 of the ring pack. The groove system 17 is formed by grooves 19 and 22 in the mixing rings 15 . The mixing ring 15 is shown in FIG. 2 and is explained in more detail elsewhere on the basis of this drawing. The mixing grooves 19 of the groove system 17 in the ring assembly 5 are connected to one another by a bore system 18 . The bore system is formed by a plurality of bores 20 and a plurality of longitudinal grooves 21 in the dividing rings 16 . The dividing ring 16 is shown in FIG. 3 and is explained elsewhere on the basis of this drawing. At the end of the ring packet, an outlet chamber 27 is formed between the housing 3 and the bracing element 10 . The outlet chamber 27 is connected to the outlet 29 of the mixer via a plurality of outlet grooves 28 in the bracing element 10 .

In the device shown in FIG. 1, a melt flow generated by the extruder screw 7 is conveyed at the outlet of the extruder into the inlet chamber 26 of the mixer. The melt flow passes from the inlet chamber 26 into the mixing grooves 9 of the groove system 17 via a plurality of bores 25 . When the melt flow passes from the mixing grooves 9 in the first mixing ring 15 to the bores 20 and grooves 21 of the first dividing ring 16 , the melt flow is further divided and deflected. The process is repeated depending on the number of pairings of mixing rings 15 and dividing rings 16 . At the end of the ring packet 5 , the melt flow from the bores 20 and grooves 21 of the last dividing ring 16 enters the adjacent outlet chamber 27 . The melt flow passes from the outlet chamber 27 via a plurality of outlet grooves 28 to the outlet 29 of the mixer.

The distribution of the melt flows within the ring packet 5 is determined by the groove system 17 and the bore system 18 . The groove system 17 is formed by grooves in the mixing rings. In FIG. 2, the view is shown of a mixing ring. The mixing ring 15 is annular. The inner diameter of the mixing ring 15 serves to receive the mixing ring on the rotor 4 . For rotation and fastening, the mixing ring 15 has a feather key groove 30 on the inside diameter. A plurality of axially extending mixing grooves 19 are introduced on the circumference of the mixing ring 15 . The mixing grooves 19 have a semicircular cross section. The mixing grooves 19 are arranged on the circumference at the same distance, which is characterized by the pitch angle α, from one another. On the end faces of the mixing ring 15 , an inclined groove 22.1 and an inclined groove 22.2 are introduced for each mixing groove 19 . The oblique grooves 22.1 and 22.2 extend over half the pitch angle α, which defines the circumferential pitch of the mixing grooves 19 with respect to one another. The oblique grooves 22.1 and 22.2 each open into a mixing groove 19 . The opposite ends of the oblique grooves 22.1 and 22.2 are each in the range of a pitch diameter d that is smaller than the outer diameter of the mixing ring. The oblique grooves 22.1 of the front end face of the mixing ring 15 shown in FIG. 2 are mirror images of the oblique grooves 22.2 of the opposite end face. Thus, the oblique grooves 22.1 and 22.2 of a mixing groove 19 enclose an angle in the side projection.

The mixing ring 15 shown in FIG. 2 is combined with the dividing ring shown in FIG. 3 to form the ring packet shown in FIG. 1.

In Fig. 3, the division ring 16 is shown in a view. The dividing ring 16 is also ring-shaped with a receiving bore for the rotor 4 . The receiving bore of the graduation ring 16 is expanded by a feather key 31 . On the circumference of the dividing ring 16 , a plurality of longitudinal grooves 21 are made running in the axial direction. The longitudinal grooves 21 are made at a uniform distance from one another on the circumference. The pitch angle α corresponds to the pitch angle of the mixing grooves 19 of the mixing ring 15 . The longitudinal grooves 21 are thus aligned with the mixing grooves 19 in the ring package 5 . The longitudinal grooves 21 have a semicircular cross section, which is, however, significantly smaller than the cross section of the mixing grooves 19 . A plurality of bores 20 are made in the dividing ring 16 by half a pitch angle to the longitudinal grooves 21 . A bore 20 is provided between two longitudinal grooves 21 . The bores 20 are arranged on the pitch circle diameter d. The bores 20 thus correspond to the end regions of the oblique grooves 22 of the mixing ring 19 .

In order to clarify the function of the current division, the bores 20 were moved into the sectional plane of the longitudinal groove 21 in the sectional view in FIG. 1.

The mixing ring 19 and the dividing ring 16 are - as shown in Fig. 1 - joined together to form the ring packet 5 . The mixing rings 19 and the dividing rings 16 have an equally large diameter, so that the ring packet is guided through the rotor 4 in the housing 3 with little play. The mixing grooves 19 and the longitudinal grooves 21 are therefore limited by the housing wall of the housing 3 . At the beginning of the ring package, the melt from the extruder is divided into the mixing grooves 19 of the first mixing ring via the inlet ring 24 . If we now consider a mixing chamber 19 , part of the melt will flow axially directly into the longitudinal groove 21 of the dividing ring 16 . Another part passes through the inclined groove 22 in the mixing ring 15 to the bore 20 of the dividing ring 16 in the longitudinal groove. The partial flow 21 now reaches in the axial direction directly into the mixing groove 19 of the second mixing ring lying behind it. The partial flow in the bore 20 , on the other hand, is guided on the end face of the second mixing ring 15 via an oblique groove 22 to a mixing groove adjacent to the circumference of the second mixing ring. As a result, in the mixing ring arranged behind the dividing ring in the flow direction, partial flows are mixed in the individual mixing grooves of this mixing ring, which come from adjacent mixing grooves of the mixing ring arranged upstream of the dividing ring. A very intensive distribution or mixing of the melt is thus achieved.

In order to obtain an additional mixture resulting from the rotary movement of the rotor, transverse grooves can advantageously be introduced on the circumference of the dividing ring 16 or the mixing ring 15 . To illustrate, a transverse groove is shown in FIG. 1 and FIG. 3 in phantom 23 arranged in the individual division rings 16. The transverse groove 23 runs in a surface line of the dividing ring inclined to the normal plane. This increases the dynamic component when the melt is mixed.

It is also possible to form a worm gear on the circumference of one or more dividing rings 16 or on one or more mixing rings 15 on the circumference. The play formed between the housing 3 and the respective dividing ring or mixing ring is increased by the height of the worm gear. An advantageous conveying effect can thus be generated in the mixer.

The rings of the ring package 5 shown in Fig. 2 and Fig. 3, by way of example to look at. The inventive idea can also be realized by other arrangements of the grooves and bores in the mixing rings and dividing rings. For example, the longitudinal groove 21 in the dividing ring 16 shown in FIG. 3 can be replaced by a hole, so that the current is divided by two holes. Likewise, the inclined grooves 22 shown in FIG. 2 can be introduced in the dividing ring 20 instead of in the mixing ring 15 .

The invention is characterized by its high flexibility in the arrangement of the Mixing elements. They are therefore particularly suitable to immediately Output of an extruder to absorb and exit the emerging melt stream  mix. However, it is also possible to use the mixer independently of one Connect extruder to a melt guide. The rotor is going through driven an independent drive.  

Reference list

1

mixer

2nd

Extruder

3rd

casing

4th

rotor

5

Ring package

6

cylinder

7

Extruder screws

8th

Snail gear

9

paragraph

10th

Bracing element

11

adjusting spring

12th

Thread approach

13

Thread approach

14

flange

15

Mixing ring

16

Graduation ring

17th

Groove system

18th

Drilling system

19th

Mixed groove

20th

drilling

21

Longitudinal groove

22

Oblique groove

23

Cross groove

24th

Inlet ring

25th

drilling

26

Inlet chamber

27

Outlet chamber

28

Outlet groove

29

Outlet

30th

Feather keyway

31

Feather keyway

Claims (13)

1. Device for mixing a plastic melt with a cylindrical housing ( 3 ) and with a rotor ( 4 ) rotatable in the housing ( 3 ) with a small radial clearance, which has a cylindrical circumference consisting of several mixing rings ( 15 ) and dividing rings () 16 ) carries the existing ring pack ( 5 ), the ring pack ( 5 ) being connected in a rotationally fixed manner to the rotor ( 4 ) and having a groove system ( 17 ) formed on the circumference by a plurality of axial mixing grooves ( 19 ) in the mixing rings ( 15 ), characterized in that that a bore system ( 18 ) formed by a plurality of bores ( 20 ) in the dividing rings ( 16 ) is contained in the ring assembly ( 5 ) and that the bores ( 20 ) of the bore system ( 18 ) with the mixing grooves ( 19 ) of the groove system ( 17 ) are connected to one another in the axial direction such that a melt flow is deflected and divided during the transition from the mixing grooves ( 19 ) to the bores ( 20 ). 2. Device according to claim 1, characterized in that the mixing grooves ( 19 ) of adjacent mixing rings ( 15 ) are each connected by at least two bores ( 20 ) in the dividing ring ( 16 ) arranged between the mixing rings ( 15 ), the two bores ( 20 ) open into one or two separate mixing grooves ( 19 ). 3. Device according to claim 1 or 2, characterized in that the bore system ( 18 ) is extended by a plurality of longitudinal grooves ( 21 ) introduced on the circumference of the dividing rings ( 16 ), a mixing groove ( 19 ) in the axial direction being one of the longitudinal grooves ( 21 ) and at least one of the bores ( 20 ) is assigned for the purpose of melt flow division. 4. The device according to claim 3, characterized in that the longitudinal grooves ( 21 ) are arranged distributed uniformly on the circumference of the dividing rings ( 16 ) and between two mixing grooves ( 19 ) of adjacent mixing rings ( 15 ) parallel or obliquely to the center of the axis of the dividing ring ( 16 ) . 5. Apparatus according to claim 3 or 4, characterized in that the free flow cross section of the longitudinal groove ( 21 ) is smaller than the free flow cross section of the mixing groove ( 19 ). 6. Device according to one of claims 3 to 5, characterized in that the longitudinal grooves ( 21 ) of a dividing ring ( 16 ) by a circumferential groove on the circumference of the dividing ring ( 16 ) ( 23 ) are interconnected. 7. Device according to one of the preceding claims, characterized in that the dividing rings ( 16 ) each have a plurality of on a pitch circle (d) arranged at the same distance from each other axial bores ( 20 ). 8. Device according to one of claims 1 to 7, characterized in that the bores ( 20 ) of a dividing ring ( 16 ) offset in the circumferential direction to the axial mixing grooves ( 19 ) of the adjacent mixing rings ( 15 ) and that the mixing rings ( 15 ) for each mixing groove ( 19 ) on the opposite end faces each have an oblique groove ( 22 ) which forms the connection between the mixing groove ( 19 ) and at least one bore ( 20 ) of the adjacent dividing ring ( 16 ). 9. Apparatus according to claim 8, characterized in that the opposing inclined grooves (22) in such a manner open into the end faces of the mixing ring (15) in the Mischnut (19) that an angle is included in the Seitenprojizierung between the inclined grooves (22). 10. Device according to one of the preceding claims, characterized in that the grooves ( 19 , 22 ) of the groove system ( 17 ) have a semicircular cross section. 11. Device according to one of the preceding claims, characterized in that the ring packet ( 5 ) is limited on an inlet side by an inlet ring ( 24 ) which through holes ( 25 ) an inlet chamber ( 26 ) with the mixing grooves ( 19 ) of an adjacent mixing ring ( 15 ) connects. 12. Device according to one of the preceding claims, characterized in that the rotor ( 4 ) and the housing ( 3 ) are arranged at the end of an extruder ( 2 ), the rotor ( 4 ) being drivable by an extruder screw ( 7 ). 13. The apparatus according to claim 1, characterized in that the Hole system from holes in the dividing rings and Bores are formed in the mixing rings and that the Groove system consisting of mixed grooves in the mixing rings and mixed grooves in the dividing rings is formed, the dividing rings and Mixing rings are put together in such a way that one alternates Face the hole and a mixing groove.