WO2023110663A1 - Double screw conveyor - Google Patents

Abstract

A double screw conveyor is known, comprising a screw housing and two conveyor screws, which are arranged parallel to one another in a screw chamber of the screw housing and which are rotatably mounted relative to the screw housing, comprising a drive system for driving the conveyor screws, as well as comprising a synchronisation device for synchronising the rotational movement of the conveyor screws. According to the invention, each conveyor screw has two respective screw sections conveying in opposing directions to one another, extending axially from opposing axial end regions of each conveyor screw to the centre of each conveyor screw and designed in such a way that a conveying of corresponding conveying materials occurs from the outside to a centre of the screw chamber, and the screw housing has at least two axially opposing external inlets for the conveying materials to be conveyed, as well as at least one axially inwardly shifted outlet for the conveyed material, in particular arranged in a central region of the screw space.

Description

twin screw conveyor

The invention relates to a twin screw conveyor with a screw housing and with two screw conveyors, which are arranged parallel to one another in a screw space of the screw housing and are rotatably mounted relative to the screw housing, with a drive system for driving the screw conveyors, and with a synchronizing device for synchronizing the rotary movements of the screw conveyors.

Such a twin screw conveyor is known in the form of a melt pump from EP 2 889 118 A1. The known melt pump has a housing in which two screw conveyors are arranged parallel to one another and are rotatably mounted in the housing. The screw conveyors are positively coupled via a gear to ensure that the screw conveyors run synchronously. The screw conveyors are driven synchronously with one another via an electric drive motor that is connected to the gearbox. The gear is arranged next to the housing in the axial direction of the axes of rotation of the screw conveyors. Both screw conveyors have a shaft extension that protrudes through an end face of the housing toward the gear unit, so that both shaft extensions protrude through the housing on the same side of the housing. The shaft extensions are coupled to corresponding output shafts of the transmission. On the opposite side of the housing to the end face of the housing supporting the shaft extensions of the screw conveyors, the housing is connected to a tool through which a plastic melt compressed by the screw conveyors can be pressed in order to obtain corresponding plastic moldings.

The object of the invention is to create a twin screw conveyor of the type mentioned at the outset, which has a simple and inexpensive structure and still has good functionality.

This object is achieved in that each conveyor screw has two screw sections conveying in opposite directions to one another, which extend from opposite axial end regions of each conveyor screw axially towards the center of each conveyor screw and are designed in such a way that a corresponding conveyed mass can be conveyed axially from the outside to a center of the Screw space takes place, and that the screw housing has at least two axially opposite external inlets for the conveyed mass to be conveyed and at least one axially inwardly offset outlet, in particular arranged in a central region of the screw space, for the conveyed mass. The terms "Axial" and "radial" refer to the longitudinal axes of the screw chamber and the screw conveyor. Depending on the length of the screw sections conveying in opposite directions to one another, the outlet, which is offset axially inwards, is positioned where the screw sections converge in terms of conveyance. If the screw sections are at least largely of the same length, then the outlet is arranged in the central region of the screw space. The middle area is to be understood as meaning a middle area of the screw space which, starting from an exact center, takes up additional space on both axial sides. This means that the outlet can be arranged either exactly in the middle of the screw housing or slightly offset from the middle of the screw space in the screw housing. According to the invention, the two screw sections of each conveyor screw have screw geometries that convey in opposite directions towards the center, and the inlets for the conveyed mass to be conveyed are each provided on opposite, axially outer areas of the screw chamber, so that the conveyed mass to be conveyed is fed to the screw geometries of the screw halves at the axial ends and is transported towards the center within the snail space. In the case of screw sections of approximately the same length, these are also referred to as screw halves, since they each extend at least largely over one half of the respective screw conveyor. This builds up a conveying pressure for the conveying mass in the axial direction towards the center of the worm chamber and the conveyed conveying mass is then discharged in this center through the outlet out of the worm chamber and thus also out of the worm housing. Due to the solution according to the invention, there is almost no pressure during operation of the twin screw conveyor on the opposite end faces of the screw chamber, on which at least one of the two screw conveyors is mounted, so that corresponding end bearings can be designed very simply and inexpensively. In this case, the respective screw conveyor can only be mounted on one side in the area of one end face of the screw housing or on the opposite end faces of the screw housing. Each of the two screw conveyors is advantageously driven by its own drive unit, with the two drive units being synchronized with one another via the synchronization device. Advantageously, each drive unit has an electric motor and an associated gear, with which a corresponding shaft extension of the screw conveyor to be driven is coupled for drive transmission. The twin-screw conveyor according to the invention can be designed both as a twin-screw extruder for conveying a plastic melt and for conveying other conveying masses as well as for melting plastic granules. Thus, the twin screw conveyor is intended both for conveying cold conveyed mass and for conveying hot conveyed mass, depending on the additional functional requirements for the twin screw conveyor. Depending on Functional requirements are assigned to the worm housing of the twin screw conveyor heating and/or cooling devices. The screw housing of the twin screw conveyor can also be designed to supply additives radially in the area of the screw space or to discharge gases radially from the conveying mass. A length of the screw space and diameters and lengths of the screw conveyors vary depending on a corresponding application.

In an embodiment of the invention, the screw sections conveying in the opposite direction towards the central area of the screw space are mirror-symmetrical with respect to their screw geometry to a central radial plane of the screw space. In this configuration, the screw sections form screw halves. The screw geometries of the two screw halves of each screw conveyor are thus mirrored in relation to one another, but are otherwise identical to one another. This ensures that the same conveying pressures are built up from the opposite sides towards the middle, which means that the pressures that occur are neutralized with regard to the front bearings of the conveyor screws.

In a further embodiment of the invention, screw geometries of the screw sections are designed differently, in particular in terms of diameter and axial length, and the at least one outlet is arranged axially offset relative to a central region of the screw chamber, depending on the different axial lengths of the screw sections. This configuration includes screw sections of the same length and different lengths and/or different diameters or different pitches of the screw sections. This configuration also includes a slight twisting of the screw geometry in the area of a screw section of a screw conveyor around its own axis, with screw sections nevertheless having the same length, i.e. screw halves. In addition to different screw pitches and different screw diameters of the various screw sections, the term differently designed screw geometries also includes other conveying parameters. The position of the at least one outlet relative to the screw chamber is coordinated in such a way that the at least one outlet is positioned in the region of the ends of the opposite screw sections on the delivery side.

In a further embodiment of the invention, the at least two inlets are arranged radially to a longitudinal axis of the screw housing. The two inlets on the screw housing are advantageously provided at identical distances relative to a center of the screw space, but on opposite sides. The at least two inlets advantageously protrude radially parallel to one another away from the screw chamber. The conveying mass will accordingly, during operation of the twin screw conveyor, it is fed to the screw space evenly divided between the two inlets. The inlets are preferably designed as passages in the screw housing.

In a further embodiment of the invention, the at least one outlet arranged in the central area is arranged radially to the longitudinal axis of the screw housing. The outlet is advantageously provided radially opposite to the axially offset inlets. The outlet is preferably designed as a passage in the screw housing.

In a further embodiment of the invention, the synchronization device is designed mechanically or electronically. In the case of a mechanical design, the two screw conveyors are preferably mounted on opposite end faces in the worm housing, so that a corresponding gear is provided on each opposite end face of the worm housing. In each case, a drive motor is also provided opposite each other and is assigned to a gear in each case. A mechanical synchronization device extends parallel to the longitudinal extent of the screw housing between the opposite gears and mechanically couples them for a desired synchronized run of the screw conveyors. If the synchronizing device is designed electronically, electric drive motors of the two drive units for the two screw conveyors can be provided on opposite end faces of the screw housing. The electric drive motors are then electronically synchronized with one another by wire or wirelessly.

In a further embodiment of the invention, the screw conveyors are driven in the same direction or in opposite directions to one another. Depending on whether a parallel or counter-rotating drive is provided, the screw geometries of the two screw halves of each screw conveyor are adjusted accordingly. In both cases, it is crucial that the conveyed mass is fed in axially from the outside, conveyed towards the center and discharged again from the screw chamber in the center area.

In a further embodiment of the invention, the screw conveyors are arranged vertically one above the other or horizontally next to one another in the screw housing. The respective variant is selected depending on the function, the material of the conveying mass and the need. In a further embodiment of the invention, the screw housing has at least one degassing outlet axially between an outer inlet and the outlet which is offset axially inwards. The respective degassing outlet is aligned radially with respect to the longitudinal axis of the screw housing and can be arranged radially as desired in the circumferential direction, in particular at the top, bottom, front or rear of the screw housing. The at least one degassing outlet allows the gases contained in the conveying mass to escape from the screw space to the outside at a suitable point. In this case, at least one outlet is advantageously provided at the same distance from a center of the screw space for the opposite screw halves of the screw conveyors.

In a further embodiment of the invention, at least one degassing outlet is provided in a storage area of at least one screw section. In this configuration, the degassing takes place via the screw shaft of the respective screw conveyor.

In a further embodiment of the invention, each screw conveyor is assigned at least one deflection element axially in the area of the outlet of the screw housing, which is provided for deflecting the conveyed mass conveyed by the screw geometry to the center of the screw chamber towards the outlet and/or for radial support of the screw conveyor in the manner of a plain bearing . The latter is advantageous for screw conveyors that are operated at high speeds and/or have a large length in relation to their screw diameter. The respective deflection element is used for axial support of the conveyed mass that is conveyed axially in the direction of the outlet and also for the radial deflection of the conveyed mass into the radial outlet. In addition, the respective deflection element for the respective screw conveyor in the area of the central outlet of the screw housing forms a radial support to an inner wall of the screw housing in the manner of a plain bearing. The respective deflection element can be arranged firmly on the screw core and can be supported in a sliding manner on the corresponding inner wall of the screw housing. Alternatively, the respective deflection element can be arranged in a stationary manner relative to the inner wall of the screw housing and can enclose the screw core of the conveyor screw in a ring-shaped and slidable manner. Finally, the respective deflection element can be positioned radially and floating in the circumferential direction both relative to the screw core and relative to the inner wall of the screw housing. For this floating arrangement, it is only necessary to ensure that an axial limit is provided for the corresponding deflection element, which prevents the deflection element, which is rotatable both relative to the inner wall of the screw housing and relative to the outer circumference of the screw core, from migrating in the axial direction of the screw housing. The worm housing can be designed in several parts with corresponding partial sections, which are designed to be particularly wear-resistant in the area of the at least one deflection element on the inside, ie on their inner section forming the inner wall of the worm housing. Such deflection elements are particularly advantageous for a conveying mass in the form of a plastic melt, with the deflection elements supporting the respective plastic melt flow and deflecting it in the direction of the outlet.

In a further embodiment of the invention, several deflection elements, preferably three deflection elements, are provided on the two screw conveyors, with at least one deflection element of one screw conveyor engaging radially in an axial gap of two adjacent deflection elements of the other screw conveyor in the manner of a tongue and groove principle. The central deflection element thus engages exactly in the middle between the two deflection elements of the other screw conveyor, which, in addition to sealing, results in the desired axial support of the conveyed masses conveyed axially in the direction of the outlet and also the radial deflection of the conveyed masses into the radial outlet. In addition, the deflection elements for the respective screw conveyor form a radial support to the screw space, i.e. to an inner wall of the screw housing, in the manner of a sliding bearing.

In a further embodiment of the invention, the at least one deflection element is designed in the form of a ring around a worm core of the respective conveyor worm and is arranged fixedly on the worm core or is rotatably mounted relative to the worm core. Accordingly, each ring-shaped deflection element protrudes circumferentially radially relative to the respective screw core. Advantageously, the deflection elements of the two screw conveyors are axially slightly offset from one another so that they do not touch one another when the screw conveyors are in operation. The respective deflection element is preferably formed in one piece with the screw core and together with the manufacture of the conveyor screw. Alternatively, the deflection element is produced as a separate ring part and then attached to the screw core or stationary to the screw housing, but rotatably mounted to the screw core or both relative to the screw housing and rotatable relative to the screw core. In all variants, the at least one deflection element is fixed axially relative to the screw core or the screw housing in order to prevent the deflection element from moving axially.

In a further embodiment of the invention, each deflection element has radially inner and/or outer grooves which are aligned axially or obliquely relative to an axis of rotation of the screw conveyor. The grooves allow a Lubrication through appropriate conveying mass, so that a reliable plain bearing function of the respective deflection element is guaranteed. Appropriate grooves allow permanent renewal of a plastic melt film between the deflection element and the wall of the screw space or the screw core during operation of a twin-screw extruder, since the melt film is discharged via the grooves. This prevents a plastic melt film from remaining longer between the contact surfaces of the deflection element and the adjacent wall and thereby degrading, ie breaking down. The grooves can be provided on the inner wall of the worm chamber, preferably in a wear protection bushing described below, on an outer diameter or an inner diameter of the deflection element or on an outer circumference of the worm core of the respective screw conveyor.

In a further embodiment of the invention, the screw space has wear-resistant wall sections in the area of the outlet, which are provided for the radial support of the deflection elements. The wall sections can be formed by separate, wear-resistant components that are part areas of a multi-part worm housing. Alternatively, the wall sections are formed in one piece with the worm housing and by a wear-resistant surface layer in the worm chamber. The wall sections are advantageously made of wear-resistant material, preferably as wear-protection bushings. In particular, a non-ferrous, metallic anti-wear alloy is provided as the wear-resistant material, preferably a nickel alloy matrix with dispersed tungsten carbide particles or a cobalt-based alloy. Alternatively, a nickel-rich iron-boron alloy or an iron-boron alloy with a higher chromium content can also be provided. Non-ferrous metallic anti-wear alloys are also advantageous for the screw conveyor and the deflection element, such as in particular hard alloys based on cobalt and chromium.

In a further embodiment of the invention, a screw geometry of each screw section of each screw conveyor has different functional zones over its axial length. Corresponding functional zones of the screw halves can be designed for a pressure build-up of the conveying mass. In order to prevent the conveyed mass in the area of the respective inlet from being conveyed axially outwards, a locking thread can be designed as a closure in the direction of the drive unit arranged on the front side in each case. The screw geometry can have a degassing zone, in which case grooves can optionally be provided in corresponding screw flights of the screw geometry of the screw halves. In addition, inlet areas with compression or return elements for compression can be designed as functional zones. In a further embodiment of the invention, the screw housing is designed as a one-part or multi-part cylinder component, and a drive unit for each screw conveyor is flanged to opposite front ends of the cylinder component. The two drive units for the two screw conveyors are therefore provided on opposite end faces of the screw housing. A one-piece cylinder component is particularly robust and easy to assemble. The cylinder component can also be made in several parts. In the case of a multi-part design, the cylinder component is advantageously provided with a central division in the region of the central outlet.

Further advantages and features of the invention result from the claims and from the following description of preferred exemplary embodiments of the invention, which is illustrated using the drawings.

1 shows a schematic longitudinal sectional view of an embodiment of a twin screw conveyor according to the invention with two conveyor screws arranged vertically one above the other,

Fig. 2 schematically shows a first perspective representation of the twin screw conveyor according to Fig. 1,

3 shows another perspective representation of the twin screw conveyor according to FIGS. 1 and 2,

4 shows an enlarged view of a partial area of a conveyor screw in the area of a ring-shaped deflection element according to a further embodiment of a twin-screw conveyor according to the invention, the deflection element being provided with axial grooves on the outside,

5 shows a partial area of a further screw conveyor of a further embodiment of a twin screw conveyor according to the invention similar to FIG. 4, but with oblique grooves on an outer circumference of the deflection element,

6 shows a further screw conveyor of a further embodiment of a twin screw conveyor according to the invention in a representation similar to FIGS. 4 and 5, with a deflection element being mounted such that it can rotate relative to a screw core of the screw conveyor, 7 shows a cross section through the conveyor screw according to FIG. 6 in the area of the deflection element,

8 shows a sectional view analogous to FIG. 1 of a further embodiment of a twin screw conveyor according to the invention with a multi-part screw housing,

9 shows a central partial area of the twin screw conveyor according to FIG. 8 in an enlarged sectional view,

10 shows one half of the worm housing according to FIGS. 8 and 9,

11 shows a sectional view through half of the worm housing according to FIG. 10 in a sectional plane along a central longitudinal axis of the worm housing in FIG. 8, but orthogonally to the plane of the drawing according to FIG. 8,

FIG. 12 shows a perspective view of the twin screw conveyor according to FIG. 8,

Fig. 13 in a further representation from a perspective opposite to Fig. 12 the

Twin screw conveyor according to Fig. 12,

14 shows another embodiment of a twin screw conveyor according to the invention, similar to FIG. 1, schematically in a longitudinal section;

15 shows an enlarged view of a section of a longitudinal section with screw conveyors that have different diameters,

Fig. 16 shows a cross section along line XVI-XVI in Fig. 15,

17 in a longitudinal section a further embodiment of a twin screw conveyor according to the invention similar to FIG. 1 or 14, with different screw geometries and with three deflection elements, and

18 shows an enlarged view of a section of the two screw conveyors according to FIG. 17 in the area of the three deflection elements according to FIG. A twin-screw conveyor in the form of a twin-screw extruder according to FIGS. 1 to 3 has a cylindrical screw housing 1 which is provided on the inside with a screw space which is designed to accommodate two parallel screw conveyors 2a, 2b. The screw chamber is designed in such a way that a wall of the screw chamber is spaced evenly from the outer contours of corresponding screw geometries of both screw conveyors 2a, 2b. The twin-screw extruder according to FIGS. 1 to 3 is designed to convey plastic mass. Plastic mass is to be understood as meaning both plastic melt and plastic granulate. Both screw conveyors 2a and 2b have the same length and essentially cylindrical screw cores that have identical diameters. The screw geometries are formed in the two conveyor screws 2a, 2b by helical screw threads, which are delimited by correspondingly helical screw webs.

As can be seen in FIG. 1, both the screw conveyor 2a and the screw conveyor 2b each have two screw halves 3a, 4a; 3b, 4b, the screw geometries of the two screw halves 3a, 4a and 3b, 4b being designed in opposite directions to one another. Both screw halves 3a, 4a; 3b, 4b of both screw conveyors 2a and 2b are designed with regard to their screw geometries and thus with regard to their screw threads in such a way that a conveying mass to be conveyed, in this case a plastic melt, is conveyed axially from the outside inwards towards the center of the screw space according to the arrows shown in Fig. 1 becomes. A delivery pressure of up to several hundred bar builds up towards the middle, whereas there is almost no delivery pressure axially on the outside. The terms “axial” and “radial” refer to a longitudinal extension of the screw space of the screw housing 1 and thus to the longitudinal extensions of the axes of rotation of the screw conveyors 2a and 2b.

The twin-screw extruder is provided with suitable heating devices in a manner not shown, which, depending on the intended use, ensure melting or tempering of the plastic mass, with the heating devices being provided on the outside around the screw space. In addition, cooling devices can be provided for a suitable temperature control of the plastic mass in the screw space. Both heating devices and, if necessary, cooling devices are provided in pairs, with each pair part being assigned to one screw half 3a, 4a; 3b, 4b is assigned.

As can be seen from FIG. 1, the two screw conveyors 2a and 2b on opposite end faces of the screw housing 1 are each driven by a drive unit 6a, 7a; 6b, 7b driven. For this purpose, the screw conveyor 2a has an axial shaft extension which protrudes axially from the end face of the screw housing 1 by means of a shaft extension 5a. The screw conveyor 2b has a corresponding shaft extension 5b, which protrudes from this worm housing 1 on the opposite end face of the worm housing 1 . Both shaft extensions 5a, 5b extend coaxially to the longitudinal axis of the respective screw conveyor 2a, 2b. The two shaft extensions 5a, 5b are each coupled to a gear 6a, 6b, shown only schematically. Each gear 6a, 6b is driven by an electric drive motor 7a, 7b. The two electric drive motors 7a, 7b are synchronized with one another by means of an electronic synchronizing device S in such a way that synchronized synchronism of the two screw conveyors 2a, 2b is ensured.

As can be seen from FIGS. 1 to 3, the respective drive unit consisting of a gear 6a, 6b and an electric drive motor 7a, 7b is firmly connected to the worm housing 1 via an annular flange 8 in each case. The two annular flanges 8 are attached to the opposite end faces of the worm housing 1 on this.

The worm chamber and thus the worm housing 1 are assigned two inlets 10 at opposite axial end sections of the worm chamber for supplying the plastic melt serving as the conveying mass, which inlets are designed radially as passages in the worm housing. The two inlets 10 are each at the same distance from opposite sides relative to a center of the worm housing 1 and thus relative to a center of the worm chamber—also to be understood here as axial. As can be seen in FIG. 3, both inlets 10 are aligned radially parallel to one another.

In addition, an outlet 11 is provided axially centrally on the worm housing 1 and is directed radially outwards from the worm chamber opposite the inlets 10 .

According to the double arrows in FIGS. 2 and 3, plastic mass is supplied via the two inlets 10 in a uniform distribution, which is then discharged radially again at the central outlet 11 after being conveyed and processed by the two conveyor screws 2a and 2b. In order to support the discharge of the processed plastic mass, each conveyor screw 2a, 2b has a ring-shaped deflection element 9 in the middle, which is arranged circumferentially on the screw core of the conveyor screw 2a, 2b and is in one piece with it, and which is radially separated from the screw core of the respective conveyor screw 2a , 2b protrudes outwards and seals largely tightly with the wall of the screw chamber. The of The plastic melt conveyed towards the middle of the respective screw half of both screw conveyors 2a, 2b is thus necessarily supported on the deflection elements 9 and is deflected radially outwards, so that the plastic melt can exit from the outlet 11. In addition, the deflection elements 9 are used for radial support of the respective screw conveyor 2a, 2b on a wall of the screw chamber, in order to serve as a slide bearing when the screw conveyor is rotating, which ensures perfect concentricity of the screw conveyors, especially in the case of long screw conveyors or at high speeds of the screw conveyors, even in their middle areas allowed.

As can be seen from FIG. 2, the screw chamber also has two degassing openings (degassing outlets 12) which allow gases to escape radially from the screw chamber. The two degassing openings (degassing outlets 12 ) are designed as passages in a wall of the worm housing 1 , radially in the same direction as the outlet 11 and at equal axial distances opposite a center of the worm chamber. The two inlets 10 and the outlet 11 are each designed as passages in the housing wall of the screw housing 1 .

In the twin-screw extruder according to FIGS. 1 to 3, the two screw conveyors (2a, 2b) are driven in opposite directions to one another and via an electronic

Synchronizing device synchronized with each other.

Different configurations of deflection elements 9', 9" and 9"" for a conveyor screw 2'a, 2'b, 2"a, 2"b;2"'a,2"'b, which can be used as an alternative to a deflection element 9 that can be seen in FIG. The screw conveyors 2'a, 2'b;2"a,2"b;2"'a,2"'b are parts of a twin-screw extruder in the same way as the screw conveyors 2a and 2b with the deflection elements 9 according to FIG. 1. The screw conveyors 2'a, 2'b;2"a,2"b;2"'a,2"'b are designed in the same way as the screw conveyors 2a, 2b according to FIG. 1, so that for the representations according to FIGS is referred to Figs. 1 to 3 to avoid repetition. The differences between the screw conveyors 2'a, 2'b;2"a,2"b;2"'a,2"'b received. Both in the case of the conveyor screw 2'a, 2'b and the respective conveyor screw 2"a, 2"b of a corresponding twin-screw extruder, the deflection elements 9', 9" are in the same way together with the conveyor screw 2'a, 2'b;2"a,2"b are made in one piece, as is the case with regard to the screw conveyors 2a, 2b and the deflection elements 9. However, the deflection elements 9′, 9″ are additionally provided with several over an outer circumference of the respective Deflection element 9 ', 9 "distributed grooves Ni, N2 provided. In the embodiment according to FIG. 4, the grooves Ni are designed as axial grooves. In the exemplary embodiment according to FIG. 5, the grooves N2 are designed as oblique grooves.

In the case of the screw conveyors 2"'a, 2"'b according to FIGS. 6 and 7, on the other hand, the deflection element 9"" is rotatably mounted on a screw core of the screw conveyor 2"'a, 2"'b. In addition, the deflection element 9″″ has several grooves N3 on the inside on an inner circumference of the ring-shaped deflection element 9″″, which are distributed uniformly over the inner circumference and which can be designed as axial or oblique grooves. Radially on the outside, the deflection element 9″ can be fixed either axially on an inner wall of the screw chamber or in the circumferential direction. Alternatively, the deflection element 9"" can also be rotatable in the circumferential direction relative to the inner wall of the screw chamber. For the latter case, an axial fixation for the deflection element 9'' is provided either in the area of the screw core or in the area of the inner wall of the screw space, which prevents the deflection element 9'' during operation of the twin-screw extruder and thus during the rotating operation of the screw conveyor 2'''a, 2"'b migrates axially on the snail core.

A twin-screw extruder according to FIGS. 8 to 13 is also provided for conveying plastic mass and, apart from the differences described below, has an identical structure to the twin-screw extruder according to FIGS. 1 to 3. To avoid repetition, reference is therefore made to the explanations the twin screw extruder according to Figs. 1-3. Functionally identical components or sections are provided with the same reference numbers, but increased by a power of 10, unless three-digit reference numbers have been assigned to them.

The two screw conveyors 200a and 200b each have two screw halves 300a, 400a; 300b, 400b, which are designed identically to the screw halves 3a, 4a; 3b, 4b of the screw conveyors 2a, 2b.

A difference in the twin-screw extruder according to FIGS. 8 to 13 is that the screw housing 100 is designed in several parts. It is made up of two worm housing halves 101 which are mirror-symmetrical to one another but are otherwise identical in design. The worm housing halves 101 are each firmly connected on their outer end faces with flanges 80, on each of which a drive unit with a gear 60a, 60b and an electric drive motor 70a, 70b is held. The snail housing 100 is divided in the middle, ie in the In the area of the central outlet 111, the inner end faces of the two screw housing halves 100 butt against one another.

As can be seen in particular from FIGS. 9 and 10, these open end faces of the screw housing halves 101 are provided with wear protection bushings 102 which, together with the housing walls of the screw housing halves 101, define the central outlet 111. The wear protection bushings 102 are made of highly wear-resistant metallic material and serve to support the two deflection elements 90 radially on the outside during the rotating operation of the screw conveyors 200a, 200b in the manner of a sliding bearing. The high wear resistance ensures reliable and consistent radial support for the deflection elements 90, which are integrally formed on the screw cores of the screw conveyors 200a, 200b. The two-part screw housing 100 has two inlets 110 and two degassing outlets 120 in the same way, with one inlet 110 and one degassing outlet 120 being provided radially opposite each other on a screw housing half 101 in each case. The central outlet 111 is formed by both worm housing halves 101 together. In order to connect the two worm housing halves 101 firmly to one another in the middle, two annular flanges F are provided which are firmly connected to the outer circumference of the respective worm housing halves 101 in the area of the inner end faces. On the other hand, the two flanges F are firmly connected to one another in order to create a worm housing 100 that is dimensionally stable throughout.

A twin screw conveyor according to FIG. 14 largely corresponds to the twin screw conveyor described above according to FIGS. 1 to 3. For the sake of simplicity, the

Double screw conveyor according to FIG. 14 provided with the same reference numerals as the

Twin screw conveyor according to FIGS. 1 to 3. The comments on the

Twin screw conveyors according to FIGS. 1, 2 and 3 apply in the same way to the twin screw conveyor according to FIG. 14, with the exception of the differences described below.

The essential difference in the twin screw conveyor according to FIG. 14 is that the two screw conveyors 2a and 2b have screw sections 3a, 4a and 3b, 4b of different lengths. Correspondingly, an outlet (not shown) on the worm housing 1 is not in the central area, but rather offset to the right according to the drawing according to FIG. 14 and is located at the height of the two deflection elements 9. The screw shafts of the two screw conveyors 2a and 2b are designed in particular in the area of the shaft extensions 5a and 5b in such a way that degassing of the screw space is made possible via the screw shafts.

In a twin screw conveyor according to FIGS. 15 and 16, which in terms of structure and function can be designed either according to FIGS. 1 to 3 or according to FIG. 14, the adjacent screw conveyors 2a and 2b are provided with screw diameters of different sizes. The screw chamber of the screw housing 1 is also adapted in a corresponding manner, in that the screw conveyor 2a is accommodated in a smaller section of the screw chamber than the screw conveyor 2b underneath. The twin-screw conveyor according to FIGS. 15 and 16 thus has, analogously to the twin-screw conveyors according to FIGS. 1 to 3 and 14, conveyor screws 2a and 2b lying vertically one above the other. In this embodiment, too, the same reference numerals have been used as in the case of the twin-screw conveyors according to FIGS. 1 to 3 and 14, in order to avoid reference numeral complications.

In the twin screw conveyor according to FIGS. 17 and 18, which is also provided with the same reference numbers despite its different design to the twin screw conveyors described above, the two left screw sections 3a and 3b of the two conveyor screws 2a and 2b are provided with the same diameters, but larger are than the two right screw sections 4a and 4b of the two screw conveyors 2a and 2b. In the twin screw conveyor according to FIGS. 17 and 18, a total of three deflection elements 9 are provided in the area of an outlet (not shown), which interlock according to the tongue and groove principle. This can be clearly seen from FIG. One deflection element 9 of the lower screw conveyor 2b engages exactly in the middle radially and axially between the two adjacent deflection elements 9 of the screw conveyor 2a, so that the desired radial and axial deflection functions of the deflection elements 9 result. In addition, at least the lower deflection element 9 and the deflection element 9 on the right in FIG.

Claims

Claims Twin screw conveyor with a screw housing (1) and with two screw conveyors (2a, 2b), which are arranged parallel to one another in a screw space of the screw housing (1) and are mounted rotatably relative to the screw housing (1), with a drive system for driving the screw conveyors ( 2a, 2b), and with a synchronizing device (S) for synchronizing the rotational movements of the screw conveyors (2a, 2b), characterized in that each screw conveyor (2a, 2b) has two screw sections (3a, 4a; 3b, 4b) conveying in opposite directions to one another which extend from opposite axial end regions of each conveyor screw (2a, 2b) axially towards the center of each conveyor screw (2a, 2b) and are designed in such a way that a corresponding conveyor mass is conveyed axially from the outside towards a center of the screw space, and that the screw housing (1) has at least two axially opposite external inlets (10) for the conveyed mass to be conveyed and at least one outlet (11) for the conveyed mass which is offset axially inwards and is arranged in particular in a central area of the screw chamber. Twin screw conveyor according to Claim 1, characterized in that the screw sections (3a, 4a; 3b, 4b) conveying in opposite directions towards the central area of the screw space are mirror-symmetrical to a central radial plane of the screw space with regard to their screw geometry. Twin screw conveyor according to claim 1, characterized in that screw geometries of the screw sections are designed differently, in particular in terms of diameter and axial length, and that the at least one outlet (11) is arranged axially offset relative to a central region of the screw space, depending on the different axial lengths of the screw sections. Twin screw conveyor according to claim 1, 2 or 3, characterized in that the at least two inlets (10) are arranged radially to a longitudinal axis of the screw housing (1). Twin screw conveyor according to one of the preceding claims, characterized in that the at least one outlet (11) arranged in the central area is arranged radially to the longitudinal axis of the screw housing. Twin screw conveyor according to one of the preceding claims, characterized in that the synchronizing device (S) is mechanical or electronic. Twin screw conveyor according to one of the preceding claims, characterized in that the conveyor screws (2a, 2b) are driven in the same direction or in opposite directions to one another. Twin screw conveyor according to one of the preceding claims, characterized in that the conveyor screws (2a, 2b) are arranged vertically one above the other or horizontally next to one another in the screw housing (1). Twin screw conveyor according to one of the preceding claims, characterized in that the screw housing (1) has at least one degassing outlet (12) axially between an outer inlet (10) and the outlet (11) offset axially inwards. Twin screw conveyor according to one of Claims 1 to 8, characterized in that at least one degassing outlet is provided in a storage area of at least one screw section. Twin screw conveyor according to one of the preceding claims, characterized in that at least one deflection element (9) is assigned to each conveyor screw (2a, 2b) in the area of the outlet (11) of the screw housing (1), which is used to deflect the through the screw geometry to the center of the screw space conveyed conveying mass is provided towards the outlet (11) and/or to support the conveyor screw in the manner of a plain bearing. Twin screw conveyor according to Claim 11, characterized in that several deflection elements (9), preferably three deflection elements, are provided on the two screw conveyors (2a, 2b), with at least one deflection element of one screw conveyor (2a) being radial in the manner of a tongue and groove principle engages in an axial gap of two mutually adjacent deflection elements of the other screw conveyor (2b). Twin screw conveyor according to claim 11 or 12, characterized in that the at least one deflection element (9) annularly around a screw core of - 18 - the respective screw conveyor (2a, 2b) and is arranged fixedly on the screw core or is mounted so that it can rotate relative to the screw core. Twin screw conveyor according to one of Claims 11 to 13, characterized in that each deflection element has grooves which are located radially on the inside and/or on the outside and which are aligned axially or at an angle relative to an axis of rotation of the conveyor screw. Twin screw conveyor according to one of Claims 11 to 14, characterized in that the screw space has wear-resistant wall sections in the area of the outlet, which are provided for radial support of the deflection elements. Twin screw conveyor according to one of the preceding claims, characterized in that a screw geometry of each screw section (3a, 4a; 3b, 4b) of each screw conveyor (2a, 2b) has different functional zones over its axial length. Twin screw conveyor according to one of the preceding claims, characterized in that the screw housing (1) is designed as a one-part or multi-part cylinder component, and in that a drive unit (6a, 7a; 6b, 7b) for each screw conveyor (2a , 2b) is flanged.