AT522179A4 - 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

The invention relates to a plasticizing screw for a molding machine, in particular an injection molding machine or transfer 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 having a first, has a front stop in the injection direction, a second stop at the rear in the injection direction and a locking ring that can be moved 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 screw tip having several - in particular regularly spaced from one another - having radially protruding 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 further relates to a molding machine with a clamping unit and such

Injection unit.

In order to melt and convey plastic, plasticizing screws are usually used in molding machines. For molding machines, in particular for injection molding machines, a valve is often used for injection in the form of a so-called non-return valve consisting of a screw tip and a locking ring, in particular 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 together with the ring non-return valve moves backwards in the plasticizing cylinder, whereby the melted plastic moves freely

the locking ring can flow and into the channels of the tip in the antechamber

the screw tip formed.

An example of a non-return valve can be found in EP 0212 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. Due to these cams and the link control, this locking sleeve does not have any rotationally symmetrical about the longitudinal axis

trained contact surface to the pin.

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.

In the case of non-return valves with vanes in the area of the screw tip known from the prior art, the plasticizing screw rotates at a certain angle and a certain speed “point” in the plasticizing cylinder while the locking ring usually rotates at a lower speed or even stands, depending on the friction conditions. 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, so that high specific loads are transferred to the edges of the sliding surfaces during the deflections or tumbling movements. This can cause damage and premature

Failure of the non-return valve.

will.

This is achieved by a plasticizing screw with 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 wings at the tip of the non-return valve, more balanced surface loads and a

longer service life achieved.

According to a preferred embodiment, it is provided that the blades are designed to be resilient due to the cross-sectional tapering so that when the plasticizing screw is inclined or wobbly, a force of the locking ring resting against the first stop surface results in a resilient yielding of the blade by a deflection angle relative to a comes at right angles to the longitudinal axis aligned radial cutting plane. 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. The design of a better load distribution increases the service life or service life

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.

the end face at least partially form a concave curve.

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 that lies radially on the outside relative to the longitudinal axis and 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 (at least) in the area of the cross-sectional taper

rotationally symmetrical.

The wings can preferably be designed resiliently in such a way that the maximum deflection angle of each wing relative to the radial section plane oriented at right angles to the longitudinal axis is between 0.5 ° and 10 °, preferably between

1 ° and 7 °, particularly preferably between 1.5 and 5 °.

is releasably connected via a screw connection.

The base 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. There is a

Formed worm gear.

Furthermore, it is preferably provided that each wing has opposite side surfaces which delimit and co-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. That is, 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 clings to 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 corresponds at least in sections to the

first stop surface of the first, front stop is formed.

In contrast to this (more theoretical) variant, however, is preferred

provided that the screw tip contact surface is flat. Especially

Longitudinal axis aligned plane.

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

Locking ring a locking sleeve.

All essential components of the plasticizing screw are made of metal, preferably stainless steel. It can particularly preferably be provided that the

at least one first, front stop is laser-armored.

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

change.

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

Injection unit.

Further details and advantages of the present invention will become apparent from the description of the figures with reference to those shown in the drawings

Exemplary embodiments are explained in more detail below. Show in it:

1 shows a schematic side view of a molding machine including injection unit, FIG. 2 shows a partial longitudinal section through the non-return valve in

Increasing the dosage,

illustrated tumbling motion and resilient wing,

4 is a perspective view of the screw tip without the 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

FIG. 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 closing unit 13 has a stationary platen 16, a movable platen 17, a mold 18 mounted on the platen 16 and 17 and, when closed, forming at least one cavity, an end plate 19 and a drive device 20 for the

movable platen 17 on.

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 injecting the to one

The melted plastic starting material is the

The screw antechamber 22 enters the cavity C via the injection duct 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 one

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 apart 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 stop 6 with. These wings 9 include the back surface 9R, which also forms the first stop surface A6, the opposite end surface 9 $ S facing away from the locking ring 8 and the side surfaces 24 and 25. The side surfaces 24 and 25 delimit the surfaces passing between the wings 9

Longitudinal channels 31. The screw tip 4 also has the conical one

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 vestibule 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 causes the melt to flow back into the

Area of the base body 3 prevented. The entire, in the screw antechamber 22

Any melt that is present can therefore (for example after opening a shut-off needle blocking the injection channel 21) by moving the plasticizing screw 1 in

Injection direction E can be injected into cavity C.

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 the plasticizing screw 1 is dosed and rotated at the same time. 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 L7 or wobbles about it. This wobbling movement is illustrated by the angle B (shown exaggerated). 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 with previously known non-return valves 5

an early failure of the non-return valve 5 can lead.

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 v 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 from the fact that the maximum distance Dmax, measured in the direction of the longitudinal axis L in the area of the cross-sectional thickening, between the back surface 9R

and the end face is larger than the minimum, in the direction of the longitudinal axis L im

Distance Dwin, measured in the area of the cross-sectional taper, 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 9 $ S. The maximum distance is Dmax

is more than one and a half times the minimum distance dimin.

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 are the

Displacement body 29 and the (in this case three) wings 9 are shown.

FIG. 6 shows a schematic section A-A including the longitudinal axis L through the screw tip 4 in the area 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 in areas and thus a concave bulge W.

The dashed line B-B is also shown in FIG. 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 at right angles to

Longitudinal axis L aligned, radial cutting plane are located. The back surface 9R

and the end face 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 the back surface 9R and the end surface would be

9S lower.

The dashed line C-C is also shown in FIG. 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. That is to say, in a section plane oriented at right angles to the longitudinal axis L, the wings would widen from the outside inwards (as can also be seen in FIG. 4).

It is possible (unlike in FIGS. 7 and 8) that the back surface 9R and the front surface 9 $ 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 wing 9 that is effective for funding.

According to FIG. 10, the end face 9S and the back face 9R are both inclined.

The front surface 9S $ S and the back surface 9R run parallel to one another. Also

This results in a wing 9 that is effective for promotion.

List of reference symbols:

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 cylinders

12i inner wall of the plasticizing cylinder

13 clamping unit

14 Drive device for plasticizing screw 15 Filling funnel

16 fixed platen

17 movable platen

18 forming tool

19 faceplate

20 Drive device for the movable platen 21 injection channel

22 antechamber

24 side surface of the wings

25 side surface of the wings

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 9 $ S

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 Lz7 a angle of the wobbling movement of the locking ring

Innsbruck, April 25, 2019

Claims (3)

Claims 1. Plasticizing screw (1) for a molding machine (2), in particular one 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 cross-sectional taper and through the cross-sectional taper are resilient. 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 ) for a resilient yielding of the wing (9) by an angle of deflection (y) relative to a radial direction oriented at right angles to the longitudinal axis (L) Cutting plane comes. 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 a back surface (9R) facing away from the locking ring (8) Has end face (9S), the back face (9R) and / or the end face Form cross-sectional taper. 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 in a sectional plane enclosing the longitudinal axis (L) (9S) forms a concave curve at least in sections. Plasticizing screw according to Claim 3 or 4, characterized in that each wing (9) has a cross-sectional thickening which is radially outer relative to the longitudinal axis (L) and to the cross-sectional tapering, the maximum distance (Dmax.) Measured in the direction of the longitudinal axis (L) in the area of the cross-sectional thickening ) 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) im Distance (Dmin) between the back surface (9R) and the front surface (9S $) measured in the area of the cross-sectional taper. Plasticizing screw according to one of claims 3 to 5, characterized in that the minimum distance (Dmin) between the back surface (9R) and the front surface (9S) is formed around the longitudinal axis (L), cylindrical jacket-shaped section plane is consistently the same size. 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 cutting plane aligned at right angles to the longitudinal axis (L) is between 0.5 ° and 10 °, preferably between 1 ° and 7 °, particularly preferred between 1.5 and 5 °. Injection unit (11) for a molding machine (2), with a plasticizing cylinder (12) and a rotatable - in particular movable along a longitudinal axis (L) - arranged in the plasticizing cylinder (12) Plasticizing screw (1) according to one of Claims 1 to 7. Injection unit (11) according to Claim 8. Innsbruck, April 25, 2019