Apparatus and method for adjusting member in extrusion tool

Abstract

The invention relates to a device for producing plastic pipes by means of an extrusion method, comprising: an extruder (1); the invention relates to an extrusion tool (2) which is connected to an extruder in the production direction and which consists of a base tool and a molding nozzle insert which is connected to the base tool and which has at least one sleeve (10) and a mandrel (11), a melt channel (9) having a circular outlet gap (18) being formed between the mandrel (11) and the sleeve (10), the sleeve (10) is adjustable relative to the mandrel (11). According to the invention, an adjusting element (12) is provided, which is operatively connected to the sleeve (10) and can be adjusted by means of at least one drive (14), said adjusting element (12) being in contact with a slide (19) having a spherical sliding surface (17). The invention also relates to a method for adjusting a sleeve (10) in relation thereto.

Description

Technical Field

[0001] This invention relates to an apparatus for manufacturing plastic pipes using an extrusion method, comprising: an extruder; and an extrusion tool connected to the extruder along a production direction, the extrusion tool consisting of a base tool and a forming nozzle insert connected to the base tool, the forming nozzle insert having at least one sleeve and a mandrel, wherein a melt channel with a circular exit slit is formed between the mandrel and the sleeve, the sleeve being adjustable relative to the mandrel. Furthermore, this invention relates to a method for adjusting the sleeve. Background Technology

[0002] A tube extrusion tool with a sleeve and mandrel is a device used to manufacture plastic tubes. The basic principle is that molten plastic is extruded through a melt channel, and the sleeve and mandrel form an output annular slit that approximates the desired shape of the tube.

[0003] The process begins by feeding plastic granules or melt into an extruder. The machine melts the plastic and forces it into a sleeve via a screw or piston. The sleeve has an opening that approximates the shape of the desired tube.

[0004] Molten plastic is forced through a sleeve by pressure generated by friction. Simultaneously, a mandrel is inserted into the sleeve to form a cavity in the tube. The mandrel is shaped to fit the internal space of the tube and ensures the plastic is in the correct position.

[0005] The basic principle of a tube extrusion tool with a sleeve and mandrel enables the manufacture of plastic tubes of different sizes and shapes. It is a highly efficient process that allows for the continuous production of large quantities of tubes in a short time.

[0006] The mandrel can be moved within the sleeve. This allows for the manufacture of tubes with different diameters or wall thicknesses. By moving the mandrel, the distance between the mandrel and the sleeve can be changed, which in turn affects the size of the tube's cavity. Precise adjustment of the mandrel depends on the specific requirements of the tube being manufactured. This enables flexible production and adaptation to different customer requirements.

[0007] The center position of the sleeve relative to the mandrel can be changed to suit the characteristics of the extruded tube. A stable mandrel center position results in a uniform wall thickness, while movement of the sleeve relative to the mandrel can lead to uneven wall thickness. This change in center position can be achieved using specialized tools. It is important to consider the impact of this change on the quality and characteristics of the extruded tube. This is particularly important when the so-called "bagging effect" occurs. The bagging effect occurs when the extruded tube has uneven wall thickness and the tube wall bulges or dents. Changing the center position of the sleeve relative to the mandrel can help counteract the "bagging effect."

[0008] By strategically moving the sleeve relative to the mandrel, the wall thickness of the tube can be made more uniform. The central position of the mandrel results in a uniform wall thickness, while movement allows for targeted adaptation of the wall thickness in certain areas.

[0009] Therefore, by changing the center position of the mandrel relative to the sleeve, the bagging effect can be minimized or avoided by achieving a more uniform wall thickness in the extruded tube.

[0010] An extrusion tool is provided with an electric motor adjustment device that can adjust the material gap and thus uniformly increase or decrease the outlet gap throughout the circumference. With the aid of a manual centering screw, the melt outlet can be made larger at one location and then naturally decrease at the opposite location. Summary of the Invention

[0011] The object of the present invention is to provide an apparatus and a method by means of which the position of the sleeve relative to the mandrel can be adjusted from outside the tool in a largely arbitrary manner so as to adapt the exit gap to a given requirement.

[0012] In conjunction with the preamble of claim 1, the solution to the problem is characterized by having an adjusting element operatively connected to the sleeve and adjustable via at least one drive device, wherein the adjusting element contacts a slider having a spherical sliding surface.

[0013] The drive mechanism moves the adjusting element on the slider and thus positions the sleeve relative to the mandrel in different positions, thereby changing the circular outlet gap.

[0014] According to the further improved design, a bolt is arranged between the drive unit and the adjusting element. The drive unit then first moves the bolt, normally along an axis equidistant from the extrusion axis, thereby causing the adjusting element and thus the sleeve to move relative to the mandrel.

[0015] According to a further improvement, a spring assembly is provided for pre-tightening the adjusting element. The spring assembly, preferably a plurality of sequentially arranged disc springs, is pre-tightened by a component, such as an internal hexagonal screw, and thus brings the adjusting element, sliding surface, etc., to a starting position, in which the naturally occurring gaps between the movable components are substantially eliminated. Therefore, a melt seal is achieved between the adjusting element and the sliding block.

[0016] Therefore, by means of the drive device, the adjusting element and thus the sleeve can move or tilt along the spherical sliding surface about the center point of the slider. With this design of the device, the sleeve can move three-dimensionally about this point and thus adapt to the outlet gap to achieve the desired pipe cross-section.

[0017] According to the further improvement plan, the drive unit is an electromechanical drive unit, such as a linear drive unit or, in particular, a lead screw drive unit. Lead screw drives, especially, offer a large transmission ratio within a very compact installation space. They require only small drive power and are extremely precise, as a minimum adjustment step of 0.05 mm is possible. Furthermore, very high adjustment forces of 10 t or more are possible.

[0018] The machine control unit can precisely display the current position or current movement path of the drive unit. Therefore, with relatively simple calculations, it can be determined how the sleeve adjusts from its initial position via one or more of the drive units. If the sleeve's adjustment is known, the geometry of the outlet gap can also be determined, because as the sleeve moves relative to the mandrel, it changes from an annular cross-section with the same wall thickness to a cross-section with different wall thicknesses. These reproducible adjustments can be used to specifically influence the tube being manufactured.

[0019] In conjunction with the preamble of claim 7, the solution of the method is characterized in that the adjusting element moves along the spherical sliding surface of the slider, wherein the driving device presses directly or indirectly against the adjusting element.

[0020] As explained above, the drive mechanism causes the adjusting element to move, and thus the sleeve relative to the spindle.

[0021] Further advantageous improvements are given in dependent claims 8 to 10.

[0022] The proposed invention enables external adjustment of the sleeve relative to the mandrel in the nozzle insert, wherein the adjustment is performed from an initial position and the adjustment performed is known and reproducible.

[0023] This has the following advantages: especially in extrusion equipment with primary wall thickness measurement, a control loop can be established or created by means of a mathematical model, and the control loop can be used to react to changes during the process and adjust the sleeve relative to the mandrel to achieve the desired wall thickness again, so as to ensure that the plastic tube maintains the same quality. Attached Figure Description

[0024] The device according to the invention is schematically shown in the accompanying drawings:

[0025] Figure 1 A typical extrusion line is shown.

[0026] Figure 2 A cross-sectional view of an extrusion tool with an adjustable sleeve is shown.

[0027] Figure 3 A cross-sectional view of an extrusion tool with an unadjusted sleeve is shown.

[0028] Figure 4 The schematic diagram shows the center position of the sleeve relative to the mandrel.

[0029] Figure 5 The concentric position of the sleeve relative to the mandrel is schematically shown.

[0030] Figure 6 The positions of the sleeve and mandrel in three-dimensional space are schematically shown.

[0031] Figure 7 An isometric view of the extrusion tool is shown. Detailed Implementation

[0032] Figure 1 This illustrates a typical extrusion line used today for profile extrusion, whether for producing window profiles or pipes. It shows an extruder 1 in which plastic is melted and continuously fed into an extrusion tool 2 for shaping. A calibration and cooling station 3 is connected to this; additional cooling stations may be used depending on the profile. Following the cooling station is a pull-out device 4. A cutting device 5 is then arranged to cut the endless profile 6 to the desired length. The extrusion axis is marked with position number 7, and the extrusion direction with position number 8.

[0033] Figure 2 A cross-sectional view is shown through an extrusion tool 2 with a nozzle insert, which consists of at least one sleeve 10 and a mandrel 11. A melt channel 9 is formed between the inner contour of the sleeve 10 and the outer contour of the mandrel 11, which forms an exit slit 18 at the exit of the extrusion tool 2. In this embodiment, the sleeve 10 moves upward from the extrusion axis 7, so that the melt channel 9 is smaller in the lower region than in the upper region. Therefore, the exit slit 18 no longer forms an annular cross-section. The movement of the sleeve 10 is achieved via an adjusting element 12, to which the sleeve is operatively connected. In this embodiment, a drive device 14 moves the bolt 13 (the drive device 14 may also act directly on the adjusting element 12), which in turn causes the adjusting element 12 to move along the spherical sliding surface 17 of the slider 19 and thus tilts the sleeve 10. Because the sliding surface 17 is a spherical cap, this results in a circle in the cross-section through the sphere, indicated by a thick dashed line. The extrusion direction is indicated by position number 8.

[0034] Figure 3 Also shows the basis Figure 2The extrusion tool 2. However, here, the sleeve 10 is not tilted relative to the mandrel 11. The sleeve 10 and the mandrel 11 are centered relative to each other, thereby forming an annular cross-section for the outlet slit 18. The mandrel 11 and the sleeve 10 are in a basic state as the starting position, which can be considered as the basic setup. In this embodiment, the spring assembly 15 is arranged in the adjusting element 12—other arrangements are also conceivable—which holds the adjusting element 12 in this initial position.

[0035] The existing gaps, especially between the adjusting element 12 and the slider 19, are eliminated by spring tension. The preload is chosen in such a way that the sliding of the adjusting element 12 is continued, but the spherical sliding surface 17 thus becomes a melt seal. The springs in the spring assembly 15 can be adjusted via the preload component 16. In this embodiment, the preload component 16 is a commercially available hex socket screw, but this can also be achieved using other components. The spring assembly 15 consists of a plurality of disc springs arranged in succession. The same positions are indicated by the same position number.

[0036] Figure 4 and Figure 5 A schematic diagram showing the position of the mandrel 11 relative to the sleeve 10. Figure 4 In the center, the mandrel 11 and sleeve 10 are centrally arranged, thereby the melt channel 9 and the outlet gap 18 having annular or identical wall thicknesses. Figure 5 In the schematic diagram, sleeve 10 is shown moving upwards and therefore eccentrically, and thus has been displaced from its concentric position. For comparison, the center position is shown as a dashed line.

[0037] Through the spherical sliding surface 17, the sleeve 10 can not only be adjusted relative to the spindle 11 in a plane, but also the sleeve 10 can pivot three-dimensionally in space about the center point 22 of the spherical sliding surface 17. Figure 6 A three-dimensional crosshair with axes x, y, and z is shown for illustration. The Z-axis corresponds to the extrusion axis 8, and the central axis of the mandrel 11 is schematically shown as arrow 20. Arrow 21 schematically represents the central axis of the sleeve 10, which pivots not only in the X direction on the Z-plane but also in the Y direction from the Z-plane.

[0038] Figure 7A perspective view of the extrusion tool 2 with extrusion direction 8 is shown. Electromechanical drive units 14 are present; four drive units 14 are shown in this embodiment. Even three drive units 14 are sufficient for three-dimensional adjustment along the spherical sliding surface 17. Even two drive units are sufficient if the drive units can be pulled and pushed. As already described, the drive units 14 cause the pins 13 to move, which in turn cause the adjusting element 12 to rotate about the center point 22 of the spherical sliding surface 17 of the slider 19, which in turn causes the sleeve 10 to adjust relative to the mandrel 11, thereby changing the geometry of the outlet slit 18 of the melt channel 9.

[0039] Therefore, the extrusion tool 2 includes the electromechanical centering according to the invention. This has the advantage of eliminating the need for manual centering. For the operator, the accurate centering position can be seen in the control panel of the equipment control device because the adjustment of the sleeve 10 is determined based on the movement performed by the electromechanical drive 14. Therefore, highly accurate and repeatable centering is possible. A program can also be created for the centering position, thereby enabling automatic centering with stepless wall thickness control.

[0040] List of reference numerals in the attached diagram:

[0041] 1 Extruder

[0042] 2 Extrusion tools

[0043] 3 Calibration and Cooling Stations

[0044] 4 Pull-out device

[0045] 5 Cutting device

[0046] 6 Endless Profiles

[0047] 7 Extrusion axis

[0048] 8 Extrusion direction

[0049] 9 Melt Channels

[0050] 10 sleeves

[0051] 11-axis mandrel

[0052] 12 regulating elements

[0053] 13 bolts

[0054] 14 is the drive unit for 13.

[0055] 15 spring groups

[0056] 16 is a component used for pre-tightening 15.

[0057] 17 Sliding Surfaces

[0058] 18 Exit Gap

[0059] 19 sliders

[0060] The central axis of 2011

[0061] The central axis of 2110

[0062] 22-ball center

[0063] x, y, z crosshairs

Claims

1. An apparatus for manufacturing plastic pipes by extrusion, comprising: an extruder (1); and an extrusion tool (2) connected to the extruder in a production direction, the extrusion tool comprising a base tool and a forming nozzle insert connected to the base tool, the forming nozzle insert having at least one sleeve (10) and a mandrel (11), wherein, A melt channel (9) with a circular outlet slit (18) is formed between the mandrel (11) and the sleeve (10), the sleeve (10) being adjustable relative to the mandrel (11), characterized in that an adjusting element (12) is provided, the adjusting element being operatively connected to the sleeve (10) and adjustable via at least one drive device (14), the adjusting element (12) being in contact with a slider (19) having a spherical sliding surface (17).

2. The device according to claim 1, characterized in that, A bolt (13) is arranged between the drive device (14) and the adjustment element (812).

3. The device according to claim 1 or 2, characterized in that, A spring assembly (15) is provided for pre-tightening the adjusting element (12).

4. The device according to claim 1, 2 or 3, characterized in that, With the aid of the drive device (14), the adjustment element (12) and thus the sleeve (10) can move about the center point (22) of the ball of the slider (19) having a spherical sliding surface (17).

5. The device according to at least one of the preceding claims, characterized in that, The drive device (14) is an electromechanical drive device.

6. The device according to claim 5, characterized in that, The drive device (14) is a lead screw stroke transmission device.

7. A method for adjusting the sleeve (10) in the extrusion tool (2), wherein, The sleeve (10) is moved from a concentric position to change the outlet gap (18) at the end of the melt channel (9), characterized in that the adjusting element (12) is moved along the spherical sliding surface (17) of the slider (19), wherein the driving device (14) presses directly or indirectly against the adjusting element (12).

8. The method according to claim 7, characterized in that, The adjusting element (12) is in a starting position relative to the slider (19), the starting position being held by at least one arranged spring assembly (15), the preload of the spring assembly (15) being adjusted by means of a preload component (16), the preload being adjusted so that the adjusting element (12) can slide on the spherical sliding surface (17), the preload being adjusted so that the spherical sliding surface (17) is melt-sealed between the adjusting element (12) and the slider (19).

9. The method according to at least one of claims 7 or 8, characterized in that, The position of the sleeve (10) relative to the mandrel (11) is determined by the state of the drive device (14), and the geometry of the outlet gap (18) is determined thereby.

10. The method according to any one of claims 7 to 9, characterized in that, By combining automatic wall thickness measurement, a control loop is determined, which continuously optimizes the wall thickness of the produced plastic pipes.

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