AT522179B1 - Plasticizing screw for a molding machine - Google Patents

Abstract

Plasticizing screw (1) for a molding machine (2), in particular an injection molding machine or transfer press, with a base body (3) extending along a longitudinal axis (L), a screw tip (4) connected to the base body (3), which extends in the injection direction (E ) is arranged after the base body (3), and a non-return valve (5), the non-return valve (5) having a first stop (6) at the front in the injection direction (E) and a second stop (7) at the rear in the injection direction (E) and a locking ring (8) which can be moved to a limited extent along the longitudinal axis (L) between the two stops (6, 7), the first, front stop (6) having a stop surface (A6) facing the base body (3) and the locking ring (8) ) for the locking ring (8), wherein the screw tip (4) has several - in particular regularly spaced apart - radially protruding wings (9) and each wing (9) forms a first, front stop (6), the wings (9 ) in Ric respect of the longitudinal axis (L) have a cross-sectional taper and are designed to be resilient due to the cross-sectional taper.

Description

description

The invention relates to a plasticizing screw for a molding machine, in particular an injection molding machine or injection press, with a base body extending along a longitudinal axis, a screw tip connected to the base body, which is arranged in the injection direction after the base body, and a non-return valve, the non-return valve has a first, front stop in the injection direction, a second, rear stop in the injection direction and a locking ring that is movable to a limited extent along the longitudinal axis between the two stops, the first, front stop having a stop surface for the locking ring facing the base body and the locking ring, the The screw tip has a plurality of - in particular regularly spaced apart - radially projecting wings and each wing forms a first, front stop. In addition, the invention relates to an injection unit for a molding machine, with a plasticizing cylinder and a rotatable plasticizing screw, in particular movable along a longitudinal axis, arranged in the plasticizing cylinder. The invention also relates to a molding machine with a clamping unit and such an injection unit.

In order to carry out a melting and conveying of plastic, plasticizing screws are mostly used in molding machines. For molding machines, especially for injection molding machines, one often uses a valve in the form of a so-called non-return valve consisting of a screw tip and a locking ring, particularly cylindrical or sleeve-shaped, movably mounted between two stops, which closes and seals during injection. In other words, a non-return valve is arranged in the front area of the plasticizing screw in order to also enable injection with the plasticizing screw. The non-return valve prevents the melt from flowing back during a forward movement (injection movement) of the plasticizing screw along the longitudinal axis. When the dosage is increased, the plasticizing screw moves backwards in the plasticizing cylinder together with the ring non-return valve, whereby the melted plastic can flow freely through the locking ring and into the channels in the tip of the screw antechamber. These channels of the screw tip are formed between radially protruding wings of the screw tip.

[0003] An example of a non-return valve can be found in EP 0 212 224 B1, according to which the mobility of the locking sleeve is limited by a driver formed by a pin. A pressure surface for the pin is formed on the locking sleeve. In the side view of the locking sleeve, the pressure surface is a curved line and causes the locking sleeve to be controlled by the pin. At the end of the pressure surface, a cam is arranged on the locking sleeve. These cams form a final stop for the pin and cause the locking sleeve to close. As a result of these cams and the link control, this locking sleeve just does not have any contact surface for the pin that is rotationally symmetrical about the longitudinal axis.

DE 102 41 262 B4, DE 10 2007 036 441 B3 and EP 0 853 541 B2 each show non-return valves with cylindrical or sleeve-shaped locking rings. The screw tips each have several radially protruding wings. These wings each form a front stop for the locking ring. Similar devices emerge from DE 198 49 472 A1, JP S63-43713 U and US Pat. No. 5,441,400.

In the case of non-return valves with wings in the area of the screw tip known from the prior art, the plasticizing screw rotates when metering at a certain angle and a certain speed "point" in the plasticizing cylinder, while depending on the friction conditions, the locking ring usually rotates at a lower speed or even stands. Under these conditions, sliding friction occurs between the locking ring and the wing surface (front stop). In addition, due to the annular gap and the play of the plasticizing screw, the plasticizing screw and locking ring make spatially rolling movements that are similar to a tumbling movement. In known non-return valves, the front stops (wing surfaces) are conical or flat, which means that during the deflections or tumbling movements

high specific loads are transmitted at the edges of the sliding surfaces. This can lead to damage and premature failure of the non-return valve.

[0006] The object of the present invention is therefore to create an improved plasticizing screw. In particular, the known disadvantages are to be eliminated. Above all, as little damage as possible should occur in the area of the non-return valve. The service life of the non-return valve is to be extended.

This is achieved by a plasticizing screw having the features of claim 1. Accordingly, the invention provides that the wings have a cross-sectional tapering in the direction of the longitudinal axis and are designed to be resilient due to the cross-sectional tapering. Due to the elasticity of the blades at the tip of the non-return valve, more balanced surface loads and a longer service life are achieved.

According to a preferred embodiment it is provided that the wings are resiliently formed by the cross-sectional tapering that there is an inclined position or wobbling movement of the plasticizing screw by a force of the locking ring on the first stop surface to a resilient yielding of the wing by a deflection angle comes relative to a radial section plane aligned at right angles to the longitudinal axis. This means that the forces are distributed as evenly as possible across all wings. The maximum contact pressure is limited by the spring constant of the wing times the path. By designing a better load distribution, the service life or service life of the non-return valve is extended.

Furthermore, it is preferably provided that each wing has a back surface facing the locking ring and encompassing the first contact surface, and an end surface facing away from the locking ring. It can certainly be provided that (only) the back surface or (only) the front surface are flat or even have a convex curve in sections. However, it is preferably provided that the back surface, the front surface or both surfaces (back surface and front surface) have / have a concave curvature and thereby form the cross-sectional taper.

Specifically, it can be provided that the concave curvature is designed in such a way that the back surface and / or the end surface at least partially form a concave curve in a sectional plane including the longitudinal axis.

The cross-sectional tapering means that the blades, measured in the longitudinal direction, have at least one radially inner, narrower area and one radially outer, thicker area. Specifically, it can be provided that each wing has a cross-sectional thickening located radially outward relative to the longitudinal axis and to the cross-sectional tapering, the maximum distance between the back surface and the front surface measured in the direction of the longitudinal axis in the area of the cross-sectional thickening being 1.2 times as large, preferably 1. 4 times as large, particularly preferably 1.7 times as large, as the minimum distance, measured in the direction of the longitudinal axis in the area of the cross-sectional taper, between the back surface and the front surface.

The wings can have narrower and wider areas in a circular direction (that is, in a circular direction around the longitudinal axis). For example, the wings can be centrally thicker in the circular direction and have flattened outer areas. It can thus be provided that the first stop surface has a convex curvature facing the locking ring (for example, this curvature can be convex or spherical). As a result, constant surface loads and a longer service life are achieved. However, it is preferably provided that the minimum distance between the back surface and the end surface in a cylindrical jacket-shaped sectional plane formed around the longitudinal axis is the same size throughout. This means that the cross-sectional taper has the same minimum thickness throughout each wing. In other words, the wings are designed to be rotationally symmetrical (at least) in the area of the cross-sectional taper.

The wings can preferably be designed resiliently in such a way that the maximum deflection angle of each wing relative to the radial section oriented at right angles to the longitudinal axis

plane between 0.5 ° and 10 °, preferably between 1 ° and 7 °, particularly preferably between 1.5 and 5 °.

[0014] The plasticizing screw can per se be formed in one piece. For simpler manufacture and easier assembly, it is preferably provided that the base body and the screw tip are designed as separate components, the screw tip being detachably connected to the base body, preferably via a screw connection.

The basic body is that area of the plasticizing screw in which the mostly granular plastic is melted. For the melting and conveying of the plastic it is provided that at least one helically designed screw flight is formed on the base body. A screw flight is formed between the screw flights.

Furthermore, it is preferably provided that each wing has opposite side surfaces which delimit and help to form the longitudinal channels passing through between the wings. The side surfaces can be straight. The side surfaces are preferably designed to be bent in a cross-sectional plane at right angles to the longitudinal axis, the distance between the two opposite side surfaces tapering radially outward. This means that the wings are thicker in the area close to the axis than in the area remote from the axis.

So that the screw tip contact surface (sliding surface) of the locking ring nestles against the first, front stop surface, it could be provided that the screw tip contact surface has a concave curvature. It could also be provided that this concave curvature describes an annular section of a negative torus surface or an annular section of a negative, preferably spherical, dome. In this context, negative means that this surface is curved inwards and thus corresponds (at least in some areas) to the inner surface of a jacket of a torus or a dome. It could also be provided that the concave curvature of the screw tip contact surface is designed at least in sections to correspond to the first stop surface of the first, front stop.

In contrast to this (rather theoretical) variant, however, it is preferably provided that the screw tip contact surface is flat. Particularly preferably, the flat worm tip contact surface forms a plane oriented at right angles to the longitudinal axis.

For the formation of the locking ring it is preferably provided that the locking ring, in addition to the screw tip contact surface, has an annular base body contact surface facing the second stop, a cylinder jacket-shaped outer surface and a cylinder jacket-shaped inner surface. The locking ring thus forms a locking sleeve.

All essential components of the plasticizing screw consist of metal, preferably of stainless steel. It can particularly preferably be provided that the at least one first, front stop is laser-armored.

All information given herein with regard to the plasticizing screw refer to the brand-new condition in which the plasticizing screw is delivered, since there is of course wear and tear in operation. This means that the surfaces in contact with one another can change during operation due to the high loads.

Protection is also sought after for an injection unit for a molding machine, with a plasticizing cylinder and a plasticizing screw according to the invention which is rotatable - in particular movable along a longitudinal axis - arranged in the plasticizing cylinder. In addition, protection is sought for a molding machine with a clamping unit and such an injection unit.

Further details and advantages of the present invention are explained in more detail below on the basis of the description of the figures with reference to the exemplary embodiments shown in the drawings. Show in it:

1 shows a schematic side view of a molding machine including an injection unit,

[0025] FIG. 2 shows a partial longitudinal section through the non-return valve during metering,

3 shows a partial longitudinal section through the non-return valve with the wobbling movement and resilient wing illustrated,

4 shows the screw tip in perspective without a locking ring,

5 shows a front view of the screw tip,

6 shows the section A-A according to FIG. 5,

7 shows the section B-B according to FIG. 5,

8 shows the section C-C according to FIG. 5,

9 shows the section similar to FIG. 8 with an inclined back surface and

10 shows the section similar to FIG. 8 with an inclined back surface and front surface.

In Fig. 1, a molding machine 2 is shown schematically. This molding machine 2 comprises a clamping unit 13 and an injection unit 11.

The clamping unit 13 has a stationary platen 16, a movable platen 17, a mold 18 which is mounted on the platen 16 and 17 and forms at least one cavity when closed, an end plate 19 and a drive device 20 for the movable platen 17.

The injection unit 11 has a plasticizing cylinder 12 and a plasticizing screw 1 movably mounted in the plasticizing cylinder 12. The plasticizing screw 1 is mounted in the plasticizing cylinder 12 so as to be rotatable about the longitudinal axis L. In addition, the plasticizing screw 1 is mounted so that it can move linearly along the longitudinal axis L in the injection direction E. The plasticizing screw 1 is driven by a drive device 14, preferably an electric motor. The injection unit 11 also has a filling funnel 15 through which, preferably granular, plastic starting material is introduced into the plasticizing cylinder 12. By rotating the plasticizing screw 1 and by heating the plasticizing cylinder 12, the plastic starting material is melted in the area of the screw flights 10. For the injection of the plastic starting material melted into a melt, the plasticizing screw 1 is moved in the injection direction E, whereby the melt reaches the cavity C from the screw antechamber 22 via the injection channel 21.

The plasticizing screw 1 has the base body 3 and the screw tip 4. These two components can be formed in one piece. These two components are preferably designed as separate components which are detachably connected to one another. In the area of the base body 3, a helical screw flight 10 is formed by way of example. The screw tip 4 has a non-return valve 5. This non-return valve 5 comprises a first stop 6 at the front in the injection direction E, a second stop 7 at the rear in the injection direction E and a locking ring 8 that can be moved to a limited extent along the longitudinal axis L between the two stops 6 and 7. The first, front stop 6 has a Base body 3 and the locking ring 8 facing first stop surface A6 for the locking ring 8. The locking ring 8 has an annular screw tip contact surface A8 that faces the first, front stop 6 and is rotationally symmetrical about the longitudinal axis L. In addition to the screw tip contact surface A8, the locking ring 8 has an annular base body contact surface A3 facing the second stop 7 (including the second contact surface A7), a cylinder jacket-shaped outer surface Za and a cylinder jacket-shaped inner surface Zi.

Fig. 2 shows the screw tip 4 in a side view, the locking ring 8 and the plasticizing cylinder 12 are shown in section. It can be seen that the cylinder jacket-shaped outer surface Za of the locking ring 8 is spaced from the inner wall 12i of the plasticizing cylinder 12 by the distance s. The locking ring 8 rests with its, preferably flat, worm tip contact surface A8 on the first stop surface A6 of the first, front stop 6. In the exemplary embodiment shown, the screw tip 4 has a plurality of radially protruding blades 9 that are regularly spaced apart from one another. Each of these wings 9 forms a first, front one

Stop 6 with. These wings 9 include the back surface 9R, which also forms the first stop surface A6, the opposite end surface 9S facing away from the locking ring 8, and the side surfaces 24 and 25. The side surfaces 24 and 25 delimit the longitudinal channels 31 passing through between the wings 9. The screw tip 4 also has the conical displacement body 29 (this can also be dome-shaped). Between the displacement body 29 and the vanes 9 there is an annular radial recess 28. If there is no displacement body 29 - for example in the case of a three-bladed screw tip - several (specifically three) melt strands result. This leads to so-called welding lines in the injection-molded product. These weld lines arise where the melt strands meet again. The melt is mixed by the displacement body 29 in such a way that no weld lines arise in the product. This is particularly important for transparent products.

In FIG. 2, the injection unit 11 is currently performing the dosing. This metering takes place in that the plasticizing screw 1 is moved backwards relative to the plasticizing cylinder (see large arrow), that is, against the injection direction E. As a result, the melt located in the region of the screw flights 10 of the base body 3 is pressed in an injection direction E (see the large number of small arrows). As a result of the melt pressure, the locking ring 8 is moved forward relative to the plasticizing cylinder 12 in the injection direction E until the screw tip contact surface A8 rests against the first stop surface A6 of the first, front stop 6. As a result, the melt can initially flow through the gap between the locking ring 8 and the second stop surface A7. The melt then flows between the locking ring 8 and the narrower neck area 26 of the screw tip 4 and passes through the longitudinal channels 31 delimited by the blades 9 into the screw antechamber 22. This metering continues until the plasticizing screw 1 reaches its rearmost position and the screw antechamber 22 is completely filled with melt.

For the injection, the plasticizing screw 1 is then moved in the injection direction E relative to the plasticizing cylinder 12. Due to the melt in the screw antechamber 22, the locking ring 8 cannot (initially) move with the plasticizing screw 1, so that the locking ring 8 reaches a position in which the base body contact surface A3 is in contact with the second stop surface A7 of the second, rear stop 7 the non-return valve 5 arrives. This concern prevents the melt from flowing back into the area of the base body 3. The entire melt located in the screw antechamber 22 can therefore be injected into the cavity C by moving the plasticizing screw 1 in the injection direction E (e.g. after a shut-off needle blocking the injection channel 21 has been opened).

In Fig. 3 it is illustrated how it can come to relative movements between the components due to the relatively fast movements and due to the pressure prevailing in the plasticizing cylinder 12, especially when dosing up and a simultaneous rotary movement of the plasticizing screw 1 (see large arrow). Above all, tumbling movements occur. On the one hand, the plasticizing screw 1 can perform a tumbling movement about the longitudinal axis L7 of the plasticizing cylinder 12. This means that the longitudinal axis L of the plasticizing screw 1 deviates from the longitudinal axis Lz or wobbles about it. This tumbling movement is illustrated by the (exaggerated) angle β. On the other hand, the locking ring 8 of the non-return valve 5 can also perform a tumbling movement about the longitudinal axis L7 of the plasticizing cylinder 12 and / or about the longitudinal axis L of the plasticizing screw 1. This tumbling movement is illustrated by the (exaggerated) angle α. This tumbling movement (s) results in high surface loads due to the deflections between the locking ring 8 and the first, front stop 6, especially in the case of previously known non-return valves 5, which can lead to an early failure of the non-return valve 5.

In order to counteract this, it can be seen in FIG. 3 that the wings 9 are designed to be resilient. Specifically, the blades 9 have a cross-sectional tapering in the direction of the longitudinal axis L for this purpose. Due to this cross-sectional tapering, the wings 9 are designed to be resilient. If the plasticizing screw 1 is inclined or wobbly, the force of the locking ring 8 against the first stop surface A6 results in a resilient yielding of the

Wing 9 by a deflection angle y relative to a radial section plane oriented at right angles to the longitudinal axis L. The resilient deflection of the wing 9 is illustrated by the dashed lines. The cross-sectional tapering can be seen in FIG. 3 in that the maximum distance Dmnax between the back surface 9R and the end face, measured in the direction of the longitudinal axis L in the area of the cross-sectional thickening, is greater than the minimum distance measured in the direction of the longitudinal axis L in the area of the cross-sectional taper Dmin between the back surface 9R and the front surface 9S.

In Fig. 4 a screw tip 4 is shown in perspective. The annular radial recess 28 is located between the displacement body 29 and the blades 9. The locking ring 8 is not shown in FIG. This locking ring 8 would be arranged around the narrow neck area 26 including the conical area 27 of the screw tip 4. The base body 3 is also missing in this FIG. 4. However, the connection area 30 is shown in FIG. This connecting area 30 can have an external thread, for example, which corresponds to an internal thread formed in the base body 3. The longitudinal channels 31 are located between the wings 9. The wings 9 are formed by the side surfaces 24 and 25, the back surface R9 and the end surface 9S. The maximum distance Dmax is more than one and a half times as large as the minimum distance Diin-

FIG. 5 shows a schematic front view of the plasticizing screw 1 according to FIG. 4. This FIG. 5 serves primarily to illustrate the sections shown and described in the following figures. Specifically, the displacement body 29 and the (in this case three) vanes 9 are shown.

6 shows a schematic section A-A, including the longitudinal axis L, through the screw tip 4 in the region of a wing 9 (see dashed line A-A in FIG. 5). It can be seen that both the end face 9S and the back face 9R form a concave curve and thus a concave curvature W in some areas.

In Fig. 5, the dashed line B-B is shown. This forms a cylindrical jacket-shaped cut surface formed around the longitudinal axis L. If the cut surface is spread out and "flattened", the result is the schematic and simplified section B-B according to FIG. 7. This section B-B leads through a radially outer thickened area and shows the two side surfaces 24 and 25 as well as the back surface 9R and the end surface 9S. In this case, the wing 9 (at least in the area of the section B-B) is designed to be rotationally symmetrical, since the back surface 9R and the end surface 9S are each located in a radial section plane aligned at right angles to the longitudinal axis L. The back surface 9R and the front surface 9S have the same distance from one another throughout this section B-B. So they are arranged parallel to each other. In the case shown, the (partially) circular section B-B leads precisely through the area of the wing 9 where the maximum distance Dmax between the back surface 9R and the front surface 9S is given. If the section B-B were further radially outside or radially inside, the distance between back surface 9R and front surface 9S would be smaller.

In Fig. 5, the dashed line C-C is shown. This forms a cylindrical jacket-shaped cut surface formed around the longitudinal axis L. If the cut surface is spread out and "flattened", the result is the schematic and simplified section C-C according to FIG. 8. This section C-C leads through the radially inner cross-sectional taper and shows the two side surfaces 24 and 25 as well as the rear surface 9R and the end surface 9S. In this case, the wing 9 (at least in the area of the section C-C) is designed to be rotationally symmetrical, since the back surface 9R and the end surface 9S are each located in a radial section plane oriented at right angles to the longitudinal axis L. The back surface 9R and the end surface 9S have the same distance from one another throughout this section C-C. So they are arranged parallel to each other. In the case shown, the (partially) circular section C-C leads precisely through the area of the wing 9 where the minimum distance Dmin between the back surface 9R and the front surface 9S is given. In contrast to what is shown, in this section C-C the side surfaces 24 and 25 could be further apart than in section B-B. The

that is, in a sectional plane aligned at right angles to the longitudinal axis L, the wings would widen from the outside to the inside (as can also be seen in FIG. 4).

It is possible (unlike in FIGS. 7 and 8) that the back surface 9R and the end surface 9S are not aligned straight and not parallel to one another. The back surface 9R and / or the front surface 9S could comprise concave, convex or inclined areas in the (partially) circular sectional planes B-B and C-C. For example, FIG. 9 shows that the end face 9S is oriented obliquely to the back face 9R. This results in a delivery-effective wing 9. According to FIG. 10, the end face 9S and the back face 9R are both inclined.

The front surface 9S and the back surface 9R run parallel to one another. This also results in a wing 9 that is effective for promotion.

REFERENCE CHARACTERISTICS LIST:

1 plasticizing screw

2 forming machine

3 base bodies

4 snail tip

5 non-return valve

6 first, front stop 7 second, rear stop 8 locking ring

9 blades

9R back surface 9S front surface 10 screw flight 11 injection unit 12 plasticizing cylinder 12i inner wall of plasticizing cylinder 13 closing unit 14 drive device for plasticizing screw 15 filling funnel 16 fixed mold clamping plate 17 movable mold clamping plate 18 molding tool 19 front plate 20 drive device for movable mold clamping plate 21 injection channel 22 side surface of the wing antechamber 24 screw antechamber

26 throat area

27 conical section

28 annular radial recess

29 conical displacement body

30 Connection Area

31 longitudinal channels

A3 base body contact surface

A6 first stop surface

A7 second stop surface

A8 screw tip contact surface

L longitudinal axis

Lz longitudinal axis of the plasticizing cylinder

E direction of injection

Y deflection angle

W concave bulge

Dmax Maximum distance between 9R and 9S Dmin Minimum distance between 9R and 9S Za cylinder jacket-shaped outer surface

Zi cylinder jacket-shaped inner surface

Ss distance from locking ring to plasticizing cylinder

C cavity

ß angle of the wobbling movement of the longitudinal axis L about the longitudinal axis Lz a angle of the wobbling movement of the locking ring

Claims (9)

Claims 1. Plasticizing screw (1) for a molding machine (2), in particular an injection molding machine or injection press, with - A base body (3) extending along a longitudinal axis (L), - A screw tip (4) connected to the base body (3) and arranged downstream of the base body (3) in the injection direction (E), and - A non-return valve (5), the non-return valve (5) having a first stop (6) at the front in the injection direction (E), a second stop (7) at the rear in the injection direction (E) and one along the longitudinal axis (L) between the has two stops (6, 7) with limited movement of the locking ring (8), the first, front stop (6) having a stop surface (A6) for the locking ring (8) facing the base body (3) and the locking ring (8), wherein the screw tip (4) has several - in particular regularly spaced apart - radially protruding wings (9) and each wing (9) forms a first, front stop (6), characterized in that the wings (9) in the direction of the longitudinal axis (L) have a transverse Have sectional taper and formed resiliently by the cross-sectional taper are, the wings (9) measured in the longitudinal direction at least one radially inner the, narrower area and a radially outer, thicker area. 2. The plasticizing screw according to claim 1, characterized in that the wings (9) are designed to be resilient due to the cross-sectional tapering so that, in the event of an inclined position or wobbling movement of the plasticizing screw (1), a contact force of the locking ring (8) on the first stop surface (A6 ) comes to a resilient yielding of the wing (9) by a deflection angle (yv) relative to a radial section plane aligned at right angles to the longitudinal axis (L). 3. Plasticizing screw according to claim 1 or 2, characterized in that each wing (9) has a back surface (9R) facing the locking ring (8) and comprising the first contact surface (A6) and an end face (9S) facing away from the locking ring (8) , wherein the back surface (9R) and / or the end surface (9S) have a concave curvature (W) and thereby form the cross-sectional taper. 4. Plasticizing screw according to claim 3, characterized in that the concave curvature (W) is designed in such a way that the rear surface (9R) and / or the end surface (9S) at least partially forms a concave curve in a sectional plane including the longitudinal axis (L). 5. Plasticizing screw according to claim 3 or 4, characterized in that each wing (9) has a cross-sectional thickening located radially on the outside relative to the longitudinal axis (L) and to the cross-sectional tapering, the maximum distance measured in the direction of the longitudinal axis (L) in the area of the cross-sectional thickening (Dmax) between the back surface (9R) and the front surface (9S) is 1.2 times as large, preferably 1.4 times as large, particularly preferably 1.7 times as large, as the minimum in the direction of the longitudinal axis (L ) Distance (Dmin) between the back surface (9R) and the front surface (9S) measured in the area of the cross-sectional taper. 6. plasticizing screw according to one of claims 3 to 5, characterized in that the minimum distance (Din) between the back surface (9R) and the end surface (9S) in a cylindrical jacket-shaped sectional plane formed around the longitudinal axis (L) is consistently the same. 7. Plasticizing screw according to one of claims 2 to 6, characterized in that the maximum deflection angle (v) of each wing (9) relative to the radial section plane oriented at right angles to the longitudinal axis (L) is between 0.5 ° and 10 °, preferably between 1 ° and 7 °, particularly preferably between 1.5 and 5 °. 8. Injection unit (11) for a molding machine (2), with a plasticizing cylinder (12) and a rotatable - in particular movable along a longitudinal axis (L) - plasticizing screw (1) according to one of claims 1 to 7 arranged in the plasticizing cylinder (12) . 9. Molding machine (2) with a clamping unit (13) and an injection unit (11) according to claim 8. In addition 5 sheets of drawings