PLASTICIZING UNIT

Abstract

The application relates to a plasticizing unit with a cylinder and a screw that is rotatably mounted in the cylinder and has a screw section which is designed as a shearing section and in which a blocking web encircling the screw core in a helical manner and a main screw thread enclosed by the blocking web are provided. A shearing web runs in the main screw thread parallel to the blocking web at a lower height than the blocking web. In this manner, two screw threads are produced which run parallel to each other and are separated by the shearing web. The threads are designed in the form of wave screw threads. Each wave screw thread is equipped with one or more wave peaks with a surface which is designed in the form of a plateau and forms a wave peak shearing surface, wherein the wave peak shearing surface is located at the same height as the surface of the shearing web in the region. The shearing web surface section which lies in the region of a wave peak shearing surface constitutes a shearing web sharing surface. A wave peak shearing surface and a shearing web shearing surface together form a total shearing surface. A specified total shearing surface together with the inner wall of the cylinder forms a shearing gap in accordance with a shearing gap size specified for the total shearing surface.

Claims

1.-15. (canceled)

16. A plasticizing unit (1) for a plastic-processing machine, in particular for an injection moulding machine or an extrusion system, comprising a cylinder (2) and a screw (3) arranged rotatably therein, wherein the screw (3) has a screw section formed as a shearing section (B), wherein in the shearing section (B) the screw (3) has a blocking web (4) encircling the screw core in a helical manner, and a main screw thread (5) enclosed by the blocking web (4), wherein in the main screw thread (5) a shearing web (6) is arranged, preferably running parallel to the blocking web (4), wherein the shearing web (6) has at least in part a smaller height than the blocking web (4) and in these sections the surface (6a) of the shearing web (6) forms a shearing web shearing surface (SF.sub.S), wherein in the main screw thread (5) two wave screw threads (7, 8) are provided, running parallel and spaced apart from one another by the shearing web (6), wherein each of these wave screw threads (7, 8) has a thread base (15, 16), running in a wave-shaped manner in conveying direction of the melt, wherein the wave peaks (9) of the one wave screw thread (7), viewed in conveying direction of the melt, lie offset with respect to the wave peaks (10) of the other wave screw thread (8), wherein in each wave screw thread (7, 8) one or more wave peaks (9, 10) are provided with a surface (9c, 10c) configured as a plateau and forming a wave peak shearing surface (SF.sub.W), and wherein the length (L.sub.W) of a wave peak shearing surface (SF.sub.W), viewed in conveying direction of the melt, is formed to be comparatively long, in particular compared to the width (B.sub.4) of the blocking web, and/or the width (B.sub.6) of the shearing web (6) is configured at least in part to be comparatively wide, in particular compared to the width (B.sub.4) of the blocking web and preferably in the sections of the surface (6a) of the shearing web (6) formed as shearing web shearing surface (SF.sub.S), wherein one or more wave peak shearing surfaces (SF.sub.W) are situated at the same height as the surface (6a) of the shearing web (6), wherein the section of the surface (6a) of the shearing web (6) which lies in the region of a wave peak shearing surface (SF.sub.W), represents an associated shearing web shearing surface (SF.sub.SZ), wherein a wave peak shearing surface (SF.sub.W) and an associated shearing web shearing surface (SF.sub.SZ) together form an overall shearing surface (SFn), wherein a specified overall shearing surface (SFn) forms with the inner wall of the cylinder (2) a shearing surface shearing gap (Sz) according to a predetermined shearing gap size Δn (n=1, 2, 3 . . . ) for this overall shearing surface (SFn), and wherein in both wave screw threads (7, 8) several overall shearing surfaces (SFn) are present and the shearing gap size Δn (n=1, 2, 3 . . . ) becomes smaller in conveying direction of the melt.

17. The plasticizing unit according to claim 16, characterized in that with respect to the screw diameter D, the length (L.sub.W) of a wave peak shearing surface (SF.sub.W), viewed in conveying direction of the melt, has a dimension of at least 0.15×D, preferably greater than or equal to 0.20×D, most particularly preferably greater than or equal to 0.30×D, and/or that the width (B.sub.6) of the shearing web (6) has at least in part a dimension of at least 0.15×D, preferably greater than or equal to 0.20×D, most particularly preferably greater than or equal to 0.30×D, wherein the width (B.sub.6) of the shearing web (6) preferably has the above-mentioned dimension in the sections of the surface (6a) of the shearing web (6) formed as shearing web shearing surface (SF.sub.S).

18. The plasticizing unit according to claim 16, characterized in that the surface (6a) of the shearing web (6) forms with the inner wall of the cylinder (2) a shearing web shearing gap, that the surface (9c, 10c) of a wave peak shearing surface (SF.sub.W) forms with the inner wall of the cylinder (2) a wave peak shearing gap, and that the size of the shearing web shearing gap at least in the region of a shearing web shearing surface (SF.sub.S) has a value between 0.2 mm to 2.0 mm, preferably between 0.3 mm to 0.9 mm, most particularly preferably between 0.4 mm to 0.8 mm and/or the size of the wave peak shearing gap has a value between 0.2 mm to 2.0 mm, preferably between 0.3 mm to 0.9 mm, most particularly preferably between 0.4 to 0.8 mm.

19. The plasticizing unit according claim 16, characterized in that one or more wave peak shearing surfaces (SF.sub.W) at least in the region of a shearing web shearing surface (SF.sub.S) lie at the same height as the surface (6a) of the shearing web (6), and/or that one or more wave peak shearing surfaces (SF.sub.W) at least in the region of a shearing web shearing surface (SF.sub.S) lie lower than the surface (6a) of the shearing web (6) and/or that one or more wave peak shearing surfaces (SF.sub.W) at least in the region of a shearing web shearing surface (SF.sub.S) lie higher than the surface (6a) of the shearing web (6).

20. The plasticizing unit according to claim 16, characterized in that the surface (6a) of the shearing web (6), viewed in conveying direction of the melt, has a profile, in particular a step-shaped or a wave-shaped profile, wherein the profile is preferably configured such that the surface (6a) of the shearing web (6) in the region of a wave peak (9, 10) lies lower than in the other regions, and that in the region of a wave trough the surface (6a) of the shearing web (6) preferably lies at the same height as the surface of the blocking web (4).

21. The plasticizing unit according to claim 16, characterized in that the size of the shearing web shearing gap and/or the size of the wave peak shearing gap become smaller in conveying direction of the melt.

22. The plasticizing unit according to claim 16, characterized in that in the region of an overall shearing surface (SFn), the width (B.sub.6) of the shearing web (6) at its surface (6a) is smaller than or equal in size to the length L.sub.W of a wave peak shearing surface (SF.sub.W), viewed in conveying direction of the melt, wherein the width (B.sub.6) preferably has a lower threshold value of between 50% and 60% and an upper threshold value of between 80% and 90% of the length L.sub.W.

23. The plasticizing unit according to claim 16, characterized in that the arrangement of the wave peak shearing surfaces (SF.sub.W) and the length L.sub.W of the wave peak shearing surfaces (SF.sub.W) is such that the wave peak shearing surfaces (SFW.sub.7) of the one wave screw thread (7) and the wave peak shearing surfaces (SFW.sub.8) of the other wave screw thread (8), viewed in conveying direction of the melt, are spaced apart from one another, wherein preferably there is associated with a wave peak shearing surface (SF.sub.W) in the one wave screw thread (7, 8) a wave trough (12) in the other wave screw thread (8, 7).

24. The plasticizing unit according to claim 16, characterized in that a wave peak (9, 10), viewed in conveying direction of the melt, has an ascending flank (13) lying in front of the wave peak shearing surface (SF.sub.W), and a descending flank (14) lying after the wave peak shearing surface (SF.sub.W), wherein the rising flank (13) forms a first angle (α) with the surface (6a) of the shearing web (6), wherein the descending flank (14) forms a second angle (β) with the surface (6a) of the shearing web (6), and wherein the first angle (α) is smaller than the second angle (β).

25. The plasticizing unit according to claim 16, characterized in that the cylinder with the screw formed with a shearing portion (B) constitutes a first cylinder (18) with a first screw (19), that in addition to the first cylinder (18) a second cylinder (26) is provided with a second screw (27), that the second cylinder (26) has at its front end a melt outlet (28), which is in fluidic connection with a melt inlet (29) in the rear region of the first cylinder (18), that the second cylinder (26) is provided for the production of a melted plastic material (P), wherein the melted plastic material (P) can be transferred from the second cylinder (26) into the first cylinder (18), that at the first cylinder (18) an inlet is provided for the addition of filler, in particular of fibre material (F), preferably for cut fibre granulate, and that at the first cylinder (18) the inlet for the plastic material (P) and the inlet for the filler, viewed in conveying direction of the melt, are arranged in front of the shearing portion (B).

26. An injection moulding machine with a clamping unit (30) and with a plasticizing and injecting unit (15), wherein the plasticizing and injecting unit (15) has a plasticizing unit according to claim 16, and wherein the screw (3) is operatively connected to a rotary drive (23) and a linear drive (24).

27. An injection moulding machine with a clamping unit (30) and with a plasticizing and injecting unit (17), wherein the plasticizing and injecting unit (17) has a plasticizing unit according to claim 25, wherein the first screw (19) in the first cylinder (18) is operatively connected to a rotary drive (23) and to a linear drive (24), and wherein the second screw (27) in the second cylinder (26) is operatively connected to a second rotary drive (34).

28. An extrusion system with a plasticizing unit according to claim 16, wherein an extrusion tool and, if applicable, further system parts of an extrusion system are arranged downstream of the cylinder (2) viewed in conveying direction of the melt, wherein the concern is with system parts according to an extrusion product which is to be produced.

Description

[0039] The invention is to be described more closely below with the aid of example embodiments and with reference to FIGS. 1 to 11. There are shown:

[0040] FIG. 1 schematic illustration of a plasticizing unit

[0041] FIG. 2 cutout of the shearing section B of the screw of FIG. 1

[0042] FIG. 3 perspective illustration of a flattened portion of the shearing section B of the screw of FIG. 1

[0043] FIG. 4 section V-V in FIG. 3

[0044] FIG. 5 section X-X in FIG. 3

[0045] FIG. 6 section Y-Y in FIG. 3

[0046] FIG. 7 section Z-Z in FIG. 3

[0047] FIG. 8 course of the size of the shearing gap SP

[0048] FIG. 9 injection moulding machine with first embodiment of a plasticizing- and injecting unit according to the invention

[0049] FIG. 10 injection moulding machine with a second embodiment of a plasticizing- and injecting unit according to the invention

[0050] FIG. 11 further embodiment of a plasticizing unit according to the invention

[0051] In the following embodiments, a fibre material is to be used as filler. FIG. 1 shows in schematic illustration a plasticizing unit 1, marked as a whole by reference number 1, comprising a cylinder 2 and a screw 3 with a screw web 4 encircling in a helical manner. When the plasticizing unit 1 is to be embodied as a component of an injection moulding machine, the screw 3 is formed as a reciprocating screw and can be rotated by means of a suitable drive unit and moved in longitudinal direction. When the plasticizing unit 1 is to be embodied as a component of an extrusion machine, only a rotary drive is necessary for the screw 3.

[0052] The screw 3 has several sections A and B. In a first section A a plastic material P, which is introduced via a feeding hopper, is drawn in and melted. Via this feeding hopper, a fibre material F is also added. The section A is embodied in the manner of a three-zone screw and thus has a feed zone, a compression zone and a metering zone. Viewed in conveying direction of the melt, a shearing section B according to the invention adjoins. At the start of the section B, a mixture of melted plastic material P and fibre material F is present. Plastic material P and fibre material F can be fed into the cylinder 2 via one and same feeding hopper, as in FIG. 1. The fibre material F can, however, also be added after the plastic material P, viewed in conveying direction. The mixture of melted plastic material P and fibre material F is conveyed through the section B by rotation of the screw 3. The section B is formed according to the invention as shearing section B, as is explained more closely further below. At the end of the section B, a mixture of melt of plastic material P and fibre material F distributed therein is present, wherein the fibre material F, owing to the action in section B has become dispersed such that the individual filaments of the fibre material F are present distributed in a largely homogeneous manner in the mixture. A screw with a shearing section configured according to the invention can also be designated here as a shear energy screw.

[0053] The configuration of the shearing section B is to be described more closely in the following with the aid of FIGS. 2 to 7.

[0054] FIG. 2 shows a cutout of a screw 3 with shearing section B configured according to the invention, and FIG. 3 shows a perspective illustration of a flattened partial portion of the shearing section B of the screw 2. The screw web 4 is formed as a shearing web, i.e. it forms with the cylinder inner wall a blocking gap SP. The size of the blocking gap SP is dimensioned so that no or only a little melt can flow through this blocking gap SP. The size of this gap corresponds to half the screw clearance in the cylinder 2. The encircling blocking web 4 forms a main screw thread 5 of the thread width G.sub.5. In the main screw thread 5, a further web is provided as shearing web 6, and is arranged in the main screw thread 5 so that two screw threads 7 and 8 are present on both sides of the shearing web 6. As is explained more closely further below, the two screw threads 7 and 8 are formed with a thread base configured in a wave-shaped manner, viewed in conveying direction of the melt, i.e. in the manner of a so-called wave screw. Therefore, these screw threads are also to be designated here as wave screw threads 7 and 8. The thread widths G.sub.7 and G.sub.8 of the wave screw threads 7 and 8 are of equal size. The course of the wave screw threads 7 and 8 is such that a wave peak 9 in the wave screw thread 7 and a wave trough 12 in the wave screw thread 8 occur together at a position on both sides of the shearing web 6 or over a portion on both sides of the shearing web 6. Provision is also made that a wave peak 10 in the wave screw thread 8 and a wave trough 11 in the wave screw thread 7 occur together at a position on both sides of the shearing web 6 or via a portion on both sides of the shearing web 6. This course of the wave screw threads 7 and 8 is analogous to the principle as is known in the so-called double-wave screws of the prior art named in the introduction (U.S. Pat. Nos. 4,285,600 and 4,356,140).

[0055] According to the invention, on the one hand the width B.sub.6 of the shearing web 6 is distinctly greater than the width B.sub.4 of the blocking web 4. Furthermore, the height of the wave peaks 9, 10 is dimensioned such that in each wave screw thread 7, 8 there is a portion in which the surface of the shearing web 6 and the surface of a wave peak form a shared surface. In addition, the wave peaks are formed with a plateau, i.e. there is a surface of a wave peak which in conveying direction of the melt has a length L.sub.W and the width of which corresponds to the thread width G.sub.7, G.sub.8 of a wave screw thread 7, 8. The above-mentioned shared surface of shearing web 6 and wave peak 9, 10 is therefore present over the entire length Lw of the area of a wave peak 9, 10. The width of the shared surface corresponds to the sum of the width B.sub.6 of the shearing web 6 and of the thread width G.sub.7, G.sub.8 of the wave peak 9, 10 respectively involved in the shared surface.

[0056] The function of the above-mentioned shared surface consists in exerting a shear effect on the mixture of plastic material P and fibre material F which is present in a wave screw thread and flowing up a wave peak, and in dividing this mixture according to flow such that a portion continues to flow over the plateau of the wave peak and remains in the wave screw thread in which the mixture has arrived, and that another portion flows over the shearing web away into the adjacent wave screw thread. Therefore, the shared surface is also to be designated in the following as overall shearing surface SF. This overall shearing surface SF is therefore composed of a shearing surface SFw corresponding to the surface of the plateau of a wave peak 9, 10 and a shearing surface SFs of a shearing web 6, which corresponds to the product of the length Lw of the shearing surface SFw and the width B.sub.6 of the shearing web 6, i.e. SFs=Lw×B.sub.6.

[0057] Depending on whether the shearing surface SFw is present with a wave peak 9 in the wave screw thread 7 or with a wave peak 10 in the wave screw thread 8, the following shearing surfaces can be differentiated.

SFw.sub.7=Lw×G.sub.7 (shearing surface with wave peak in wave screw thread 7)

SFw.sub.8=Lw×G.sub.8 (shearing surface with wave peak in wave screw thread 8)

[0058] The configuration of the wave screw threads 7 and 8 and of the shearing web 6 is such that the width B.sub.6 of the shearing web 6 is smaller than or equal to the length Lw of a shearing surface SFw with a wave peak. In a preferred embodiment, the width B.sub.6 can assume a value of 50% of Lw and greater. Most particularly preferably, the lower limit of B.sub.6 lies between 50% and 60% of Lw and the upper limit of B.sub.6 lies between 80% and 90% of Lw. Suitable numerical values are directed to which plastic material P and which fibre material F is to be processed. The ratio of width B.sub.6 to length Lw should be such that for the material which is to be processed in the region of an overall shearing surface SF a division of the material stream results, according to which at least half of the incoming material flows via the shearing web 6 into the adjacent wave screw thread.

[0059] Viewed in flow direction, in each of the wave shear threads 7, 8 several wave peaks 9 or respectively 10 are to follow one another. An arrangement with two to five wave peaks following one another can be regarded as sufficient for most applications. However, it may also occur that a greater number of wave peaks is necessary.

[0060] FIG. 3 shows a perspective illustration of a flattened partial portion of the shearing section B of the screw 2. It can be seen there how a wave peak in the wave screw thread and a wave trough in the other wave screw thread lie adjacent to one another. The lengths of the Lw in the plateaus of the wave peaks is dimensioned so that the shearing surfaces SFw.sub.7 of the wave peaks 9 in the wave screw thread 7 and the shearing surfaces SFw.sub.8 of the wave peaks 10 in the wave screw thread 8 have a sufficient distance from one another. Owing to the offset of the shearing surfaces, a partial flow occurs from one wave screw thread into the other and back, and namely always via the shearing surface SFs of the shearing web 6, which forms with the respective shearing surface of a wave peak a shared surface or respectively overall shearing surface SF.

[0061] The length Lw of a wave peak shearing surface, viewed in conveying direction of the melt, is configured to be comparatively long, in particular compared to the width of the blocking web and/or the width of the shearing web is configured to be at least partially comparatively wide, in particular compared to the width of the blocking web and namely preferably in the portions of the surface of the shearing web formed as a shearing web shearing surface.

[0062] According to an embodiment, provision can be made that with respect to the screw diameter D the length Lw of a wave peak shearing surface, viewed in conveying direction of the melt, has a dimension of at least 0.15×D, preferably greater than or equal to 0.20×D, most particularly preferably greater than or equal to 0.30×D. Additionally or alternatively thereto, provision can be made that the width of the shearing web has at least in part a dimension of at least 0.15×D, preferably greater than or equal to 0.20×D, most particularly preferably greater than or equal to 0.30×D. The width of the shearing web can preferably have the above-mentioned dimension in the portions of the surface of the shearing web configured as shearing web shearing surface (SFs).

[0063] FIG. 4 shows a section along the line V-V in FIG. 3 and namely in a view from the direction of the arrow to the line V-V in FIG. 3. Consequently, in the wave screw thread 7 the thread base is formed ascending in flow direction (from right to left in FIG. 4) and adjoins the surface 6a of the shearing web 6 with an angle α. This is the start 9a of the plateau of the wave peak 9. From there, the surface 9c of the wave peak 9 runs over a length Lw at the same height as the surface 6a of the shearing web 6. Starting from the end 9b of the plateau of the wave peak 9, the wave peak 9 descends with an angle β in the direction of the thread base of the wave screw thread 7, until the valley floor of the wave screw thread 7 is reached, which is designated in FIG. 3 by reference number 11. In viewing direction behind the shearing web 6 the portion of the blocking web 4 projecting beyond the shearing web 6 can be seen. The wave peaks are configured such that a slowly ascending flank 13 and a steeply descending flank 14 are produced, i.e. α<β.

[0064] In FIGS. 5, 6 and 7 further sections from FIG. 3 are illustrated, which are selected so that, viewed in flow direction of the melt, they lie one behind the other.

[0065] FIG. 5 shows a section along the line X-X in FIG. 3, where it can be seen that in the wave screw thread 8 the plateau of the wave peak 10 is present with its surface 10c, and the thread base of the wave screw thread 8 therefore lies at the same height as the surface 6a of the shearing web 6. In the wave screw thread 7, on the other hand, a wave trough 11 is present, i.e. the thread base in the wave screw thread 7 has its lowest level at this point. The dashed lines mark the connection points between blocking web 4, wave screw threads 7, 8 and shearing web 6.

[0066] FIG. 6 shows a section along the line Y-Y in FIG. 3, where it can be seen that at this point of the screw in both wave screw threads 7 and 8 the respective thread base has a height which lies below the surface 6a of the shearing web 6. The thread base in the wave screw thread 7 lies slightly higher than the thread base in the wave screw thread 8, because in the wave screw thread 7 the line Y-Y intersects the ascending surface 13 of the wave peak 9 and in the wave screw thread 8 a wave trough 12 is present there.

[0067] FIG. 7 shows a section along the line Z-Z in FIG. 3, where it can be seen that in the wave screw thread 7 the plateau of the wave peak 9 is present with its surface 9c, and the thread base of the wave screw thread 7 therefore lies at the same height as the surface 6a of the shearing web 6. In the wave screw thread 8, on the other hand, a wave trough 12 is present, i.e. the thread base in the wave screw thread 8 has its lowest level at this point.

[0068] The surface of the shearing web forms with the inner wall of the cylinder a shearing web shearing gap, and the surface of a wave peak shearing surface forms with the inner wall of the cylinder a wave peak shearing gap. According to a configuration of the invention, the size of the shearing web shearing gap at least in the region of a shearing web shearing surface can have a value of between 0.1 mm to 1.2 mm and/or the size of the wave peak shearing gap can have a value of between 0.1 mm to 1.2 mm. Depending on which shearing gap (shearing web shearing gap/wave peak shearing gap) has which value, different case constellations can be present. Thus, one or more wave peak shearing surfaces at least in the region of a shearing web shearing surface can lie at the same height as the surface of the shearing web (see FIGS. 3, 5 and 7) and/or one or more wave peak shearing surfaces at least in the region of a shearing web shearing surface can lie lower than the surface of the shearing web and/or one of more wave peak shearing surfaces at least in the region of a shearing web shearing surface can lie higher than the surface of the shearing web. Furthermore, the size of the shearing web shearing gap and/or the size of the wave peak shearing gap can become smaller in conveying direction of the melt.

[0069] Between an overall shearing surface SF and the inner wall of the cylinder 2, a gap SZ is present, which is also to be designated in the following as shearing gap SZ. The size of this shearing gap SZ with a specified shearing surface SFn (n=1, 2, . . . ) is to be designated in the following by Δn (n=1, 2, 3, . . . ). The screw 2 is configured such that the shearing gap SZ becomes smaller, viewed in flow direction, i.e. Δ1>Δ2>Δ3 and so on. Thereby, the following effect is achieved: Through the reduction of the shearing gap SZ, an increase of the shear deformation is produced, which leads to an improvement of the dispersive and distributive mixing effect with the aim of further dispersing the agglomerates which are becoming smaller over the length of the process.

[0070] In FIG. 8 an embodiment is illustrated in which the surface 6a of the shearing web 6, viewed in conveying direction of the melt, is formed with a profile, therefore does not have the same height continuously as in FIGS. 3 to 7. The profile can be, in particular, a step-shaped profile or a wave-shaped profile. Preferably, the profile is configured such that the surface 6a of the shearing web 6 in the region of a wave peak 9, 10 lies lower than in the other regions and that in the region of a wave trough the surface 6a of the shearing web 6 preferably lies at the same height as the surface of the blocking web 4. Such a profile—as a stepped profile—is illustrated in FIG. 8.

[0071] FIG. 9 shows an example embodiment of an injection moulding machine with a plasticizing- and injecting unit 15 and a clamping unit 30, which are both supported on a machine bed 40. The plastic material P and the fibre material F are fed together via a feeding hopper 20 into the cylinder 2. Here, a finished premixture can be used or—as illustrated—the plastic material P and the fibre material F are delivered to the feeding hopper 20 via separate metering devices, namely a fibre material metering device 21 and a plastic material metering device 22. The screw 2 is configured as a reciprocating screw, i.e. it is operatively connected at its rear end with a rotary drive 23 and with a linear drive 24. The clamping unit 30 can be in accordance with a known type of construction and is therefore only illustrated schematically. It comprises substantially a fixed platen 31 and a movable platen 32, movable with respect thereto. Furthermore, a movable mould half 33a and a fixed mould half 33b of an injection moulding tool are provided, which in closed state form one or more cavities. When the plasticizing- and injecting unit 15 is docked onto the fixed mould half 33b, a mixture of plastic material P and fibre material F can be injected into the cavity in a known manner.

[0072] FIG. 10 shows an example embodiment of an injection moulding machine with a plasticizing- and injecting unit 16 and with a clamping unit 30, which are both supported on a machine bed 40. In contrast to the plasticizing- and injecting unit 15 of FIG. 9, here the plastic material P and the fibre material F are fed separately into the cylinder 2. The plastic material P is fed into the cylinder 2 via a first feeding hopper 20 at the rear end of the plasticizing- and injecting unit 16. Downstream, viewed in conveying direction of the melt, but before the start of the shearing section B, the fibre material F is fed into the cylinder 2. The fibre material F is delivered via a fibre material metering device 22 to a screw conveyor 25, which is flanged horizontally or vertically onto the cylinder 2.

[0073] FIG. 11 shows a variant for a spatial separation for the addition of the plastic material P and the addition of the fibre material F. This structure enables the separation of the plasticizing process from the homogenizing process of the fibre material and thereby promotes the mechanical stressing of the latter. The plasticizing- and injecting unit 17 of the third type of construction, illustrated here, comprises a first cylinder 18 with a screw 19 and a second cylinder 26 with a second screw 27. The cylinder 18 contains the screw 19, formed with a shearing section B. The additional, second cylinder 26 has at its front end a melt outlet 28, which is in fluidic connection with a melt inlet 29 in the rear region of the first cylinder 18, for example via a pipeline 35. For the second screw 27, only a rotary drive 34 is provided. The first screw 19 can be in operative connection with a rotary drive 23 and with a linear drive 24, as described above, so that a rotary and a linear movement of the screw 19 are possible, as is illustrated by the arrows at the rear end of the screw 19. The second cylinder 26 is provided for the production of a melted plastic material (P), wherein the melted plastic material (P) is transferred from the second cylinder 26 into the first cylinder 18. At the first cylinder 18 an inlet is provided for the adding of fibre material (F), in particular for cut fibre granulate. The inlet for the melted plastic material (P) and the inlet for the fibre material (F) are arranged on the first cylinder 18, viewed in conveying direction of the melt, before the start of the shearing section B.

LIST OF REFERENCE NUMBERS

[0074] 1 plasticizing unit [0075] 2 cylinder [0076] 3 screw [0077] 4 blocking web [0078] 5 main screw thread [0079] 6 shearing web [0080] 6a surface of the shearing web 6 [0081] 7 first wave screw thread [0082] 8 second wave screw thread [0083] 9 wave peak in wave screw thread 7 [0084] 9a start of the shearing surface of wave peak 9 [0085] 9b end of the shearing surface of wave peak 9 [0086] 9c surface of wave peak 9 (shearing surface) [0087] 10 wave peak in wave screw thread 8 [0088] 10c surface of wave peak 10 [0089] 11 wave trough in wave screw thread 7 [0090] 12 wave trough in wave screw thread 8 [0091] 13 ascending flank [0092] 14 descending flank [0093] 15 plasticizing and injecting unit of first type of construction [0094] 16 plasticizing and injecting unit of second type of construction [0095] 17 plasticizing and injecting unit of third type of construction [0096] 18 first cylinder of plasticizing and injecting unit 17 [0097] 19 first screw of plasticizing and injecting unit 17 [0098] 20 feeding hopper [0099] 21 plastic material metering device [0100] 22 fibre material metering device [0101] 23 rotary drive [0102] 24 linear drive [0103] 25 screw conveyor [0104] 26 second cylinder of plasticizing and injecting unit 17 [0105] 27 second screw of plasticizing and injecting unit 17 [0106] 28 melt outlet [0107] 29 melt inlet [0108] 30 clamping unit [0109] 31 fixed platen [0110] 32 movable platen [0111] 33a movable mould half [0112] 33b fixed mould half [0113] 34 rotary drive for second screw 27 [0114] 35 pipeline [0115] 40 machine bed [0116] A first screw section [0117] B second screw section [0118] C third screw section [0119] P plastic material [0120] F fibre material [0121] G.sub.5 thread width of main screw thread 5 [0122] G.sub.7 thread width of wave screw thread 7 [0123] G.sub.8 thread width of wave screw thread 8 [0124] B.sub.4 web width of blocking web 4 [0125] B.sub.6 web width of shearing web 6 [0126] Lw length of the plateau of a wave peak 9, 10 [0127] SF shearing surface [0128] SFs shearing surface of shearing web 6 [0129] SFw shearing surface of a wave peak 9, 10 [0130] SFw.sub.7 shearing surface of a wave peak in wave screw thread 7 [0131] SFw.sub.8 shearing surface of a wave peak in wave screw thread 8 [0132] Δ gap size between shearing surface and cylinder inner wall [0133] SP gap between blocking web and cylinder inner wall [0134] SZ gap between shearing surface and cylinder inner wall [0135] α angle between ascending flank and surface of the shearing web [0136] β angle between descending flank and surface of the shearing web