Plasticizing unit for a molding machine

Abstract

A plasticizing unit for a molding machine includes an injection cylinder and an axially movable plasticizing screw arranged in the injection cylinder. A filter device for filtering plasticized material, in particular plasticized plastic, is provided, and the filter device is or can be arranged axially movable in the injection cylinder.

Claims

1. A plasticizing unit for use in a molding machine, the plasticizing unit comprising: an injection cylinder; an axially movable plasticizing screw arranged in the injection cylinder; a backflow barrier arranged in the injection cylinder, the backflow barrier having a first axial end closest to the plasticizing screw and a second axial end farthest from the plasticizing screw; and a filter device configured to filter plasticized material, the filter device being arranged axially movable in the injection cylinder, wherein the filter device is located at the second axial end of the backflow barrier farthest from the plasticizing screw.

2. The plasticizing unit according to claim 1, wherein the filter device is axially and/or rotationally coupled to the plasticizing screw and/or the backflow barrier in a movement-locking manner.

3. The plasticizing unit according to claim 1, wherein the filter device includes a filter element, at least partially surrounding the plasticizing screw and/or the backflow barrier.

4. The plasticizing unit according to claim 1, wherein the filter device is configured such that the plasticized material flows through the filter device in a radial direction with respect to a longitudinal axis of the injection cylinder.

5. The plasticizing unit according to claim 1, wherein the filter device has a carrier configured to support a filter element of the filter device, the carrier being configured to channel the plasticized material through the filter element.

6. The plasticizing unit according to claim 5, wherein the carrier is connected to the backflow barrier and/or is part of the backflow barrier.

7. The plasticizing unit according to claim 5, wherein the carrier has a first channel and a second channel, wherein the second channel lies further radially inside in the carrier than does the first channel, and the first channel communicates with the second channel via the filter element.

8. The plasticizing unit according to claim 1, wherein the injection cylinder has an outlet opening in an area of the filter device.

9. The plasticizing unit according to claim 1, further comprising a sealing element configured to seal the filter device with respect to the injection cylinder.

10. The plasticizing unit according to claim 1, wherein the filter device has a filter element having a hole and/or filter structure configured to filter the plasticized material.

11. A molding machine comprising the plasticizing unit according to claim 1.

12. A method for operating the plasticizing unit, according to claim 1, the method comprising: plasticizing material to form a plasticized material in the injection cylinder and filtering the plasticized material using the filter device arranged axially movable in the injection cylinder.

13. The plasticizing unit according to claim 3, wherein the filter element is a filter ring.

14. The plasticizing unit according to claim 1, wherein the filter device is configured such that the plasticized material flows through the filter device in an axial direction with respect to a longitudinal axis of the injection cylinder.

15. The plasticizing unit according to claim 8, wherein the outlet opening is connected to a surrounding area of the injection cylinder by a shut-off valve.

16. The molding machine according to claim 11, wherein the molding machine is an injection-molding machine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages and details of the invention will be described below with reference to the drawings, in which:

(2) FIGS. 1 and 2 show a first embodiment of a plasticizing unit according to the invention,

(3) FIG. 3 shows a second embodiment of a plasticizing unit according to the invention,

(4) FIG. 4 shows a connection element between plasticizing screw and backflow barrier,

(5) FIGS. 5 and 6 show a third embodiment of a plasticizing unit according to the invention,

(6) FIGS. 7 through 9 illustrate a backflushing cycle of a plasticizing unit according to FIGS. 5 and 6,

(7) FIG. 10 shows a fourth embodiment of a plasticizing unit according to the invention, and

(8) FIG. 11 shows a molding machine with a plasticizing unit.

DETAILED DESCRIPTION OF THE INVENTION

(9) FIGS. 1 and 2 show a first embodiment of a plasticizing unit 1 according to the invention, which has an injection cylinder 3.

(10) An axially movable plasticizing screw (not represented in FIGS. 1 and 2 for reasons of clarity) and a backflow barrier 5 connected to the plasticizing screw 4 are provided in the injection cylinder 3.

(11) In this embodiment, the backflow barrier 5 is screwed to the plasticizing screw 4 in a movement-locking manner via the connection element 18.

(12) FIG. 1 shows a metered state of the plasticizing unit 1, in which the backflow barrier 5 with the plasticizing screw connected thereto is positioned in a pulled-back state, wherein a melt cushion consisting of plasticized material is present in the injection cylinder 3 between backflow barrier 5 and injection nozzle of the injection cylinder 3.

(13) FIG. 2 shows an injected state of the plasticizing unit 1, in which the plasticizing screw 4 with the backflow barrier 5 has been moved forwards in order to push the melt cushion out via the injection nozzle of the injection cylinder 3.

(14) The backflow barrier 5 of this embodiment is formed here via the sealing body 14 (a ball) and is also known as a ball-type backflow barrier 5 in the state of the art.

(15) Thusif plasticized material is conveyed in the direction of the backflow barrier 5 by the plasticizing screw 4the plasticized material is conveyed via the inlet channels 13 of the backflow barrier 5 in the direction of the sealing body 14. The sealing body 14 is pushed into a forward position by the plasticized material and clears a path in the direction of the space in front of the screw 17, wherein the plasticized material flows further via the outlet channels 15 of the backflow barrier 5.

(16) In this embodiment, a filter device 6 is provided downstream of the backflow barrier 5 in a flow direction of the plasticized material. In other words, the backflow barrier 5 has a first axial end closest to the plasticizing screw 4 (the backflow barrier being connected to the plasticizing screw 4 by the connection element 18), and has a second axial end farthest from the plasticizing screw 4 and at which the filter device 6 is located. In this embodiment, this filter device 6 is connected to the backflow barrier 5 in a movement-locking manner.

(17) To be precise, in this embodiment, the carrier 8 of the filter device 6 is connected to the backflow barrier 5 via a press fit.

(18) Alternatively or additionally, the filter device 6 with its carrier 8 is connected to the backflow barrier 5 in a material-bonding manner or by a thread.

(19) Thus, in this embodiment, the plasticized material conveyed via the outlet channels 15 of the backflow barrier 5 is supplied to the inlet channels 19 of the filter device 6. The carrier 8 is formed such that the plasticized material is guided radially with respect to a longitudinal axis 12 of the injection cylinder 3 from the inlet channels 19 to the outlet channels 16 via filter elements 7.

(20) In this embodiment, these filter elements 7 are implemented by holes which have a size such that the plasticized material can pass through the holes of the filter elements 7, but contaminants are collected on the holes.

(21) After the filtration of the plasticized material through the filter elements 7, the plasticized material is supplied to the space in front of the screw 17 via the outlet channels 16 of the filter device 6.

(22) The filtered, plasticized material accumulates in the space in front of the screw 17 and pushes the filter device 6, together with the backflow barrier 5 and the plasticizing screw 4, back into a side (an axial end) facing away from the injection nozzle.

(23) This process (the metering) is continued until a desired mass of plasticized material is achieved in the space in front of the screw 17. If this desired mass of plasticized material is achieved in the space in front of the screw 17, the plasticizing via the plasticizing screw 4 is ended by stopping a rotational movement of the plasticizing screw 4.

(24) An injection movement is then carried out via the plasticizing screw 4, in order to push the filtered, plasticized material collected in the space in front of the screw 17 out via the injection nozzle of the injection cylinder 3.

(25) For this, the plasticizing screw is moved along the longitudinal axis 12 in the direction of the injection nozzle by a linear drive, as a result of which due to the plasticized material flowing back, the sealing body 14 of the backflow barrier 5 moves into a blocking state and prevents the plasticized material from flowing back out of the space in front of the screw 17. Therefore, a pressure can be exerted on the plasticized material present in the space in front of the screw 17, and this plasticized material can thus be pushed out of the space in front of the screw 17 via the injection nozzle.

(26) After several plasticizing and injection cycles of the plasticizing unit 1, a greater filter blocking or filter coating of the filter device 6 can occur, as a result of which a filtration of the plasticized material by the filter elements 7 is only possible to a limited extent.

(27) In order to be able to clean the filter device 6, the injection cylinder 3 is equipped with an outlet opening 9 and a shut-off valve 10 provided in the outlet opening 9.

(28) Thus, to clean the filter device 6, plasticized material can first be conveyed via the plasticizing screw 4, the backflow barrier 5 and the filter device 6 into the space in front of the screw 17.

(29) For example, an injection nozzle of the injection cylinder 3 is closed or kept closed. Alternatively or additionally, a solidified sprue and/or check valves in a hot runner system or a flange/channel system provided separately for this could also be used for this purpose.

(30) The outlet opening 9 is then opened via the shut-off valve 10 and a pressure is exerted on the plasticized material present in the space in front of the screw 17 via the plasticizing screw 4 and the backflow barrier 5.

(31) As a result, the plasticized material flows back out of the space in front of the screw 17 through the filter elements 7 to the backflow barrier 5, which however closes because of the sealing body 14. Nevertheless, in order to be able to reduce the pressure, the plasticized material flows out of the injection cylinder 3 via the outlet opening 9, as a result of which the contaminants on the filter element 7 are detached and, carried by the plasticized material, can be removed from the injection cylinder 3.

(32) FIG. 3 shows a further embodiment of a plasticizing unit 1 according to the invention which, unlike the embodiment of FIGS. 1 and 2, additionally has a sealing element 11.

(33) This sealing element 11 is provided by a sealing ring which is placed against the carrier 8 of the filter device 6 along the circumference and adopts a position between the circumference of the filter device 6 and the inner wall of the injection cylinder 3.

(34) Due to a design of the filter element 7 with respect to the filter device 6 and the injection cylinder 3 which is dimensioned such that only a very small gap remains between injection cylinder 3 and sealing element 11, as well as sealing element 11 and filter device 6, through which gap the plasticized material cannot pass, the filter device 6 is sealed with respect to the injection cylinder 3.

(35) FIG. 4 shows an alternative embodiment of a connection element 18 which is formed to connect the backflow barrier 5 to the plasticizing screw 4. Via a positive-locking design, the backflow barrier 5 is mounted with respect to the plasticizing screw 4 in such a way that the backflow barrier 5 is connected linearly and in a movement-locking manner along the longitudinal axis 12 of the injection cylinder 3, but a rotational movement of the plasticizing screw 4 is not transmitted to the backflow barrier 5.

(36) FIGS. 5 and 6 show a third embodiment of a plasticizing unit 1 according to the invention. In this embodiment, a plasticizing screw 4 is again mounted axially in an injection cylinder 3 along a longitudinal extent of the injection cylinder 3, and can be driven rotationally.

(37) In the rear area, a material to be plasticized can be plasticized via the plasticizing screw 4 utilizing shearing, shear heat and optionally externally introduced heat. The plasticized material is then supplied to the filter device 6 via the inlet channel 13 of the backflow barrier 5 and the sealing body 14.

(38) The filter device 6 of this embodiment is carried by a screw extension of the plasticizing screw 4. The carrier 8 of the filter device 6 in turn carries the filter element 7 and diverts the plasticized material in such a way that the filter element 7precisely: a filter ring 7is run through in a radial direction relative to the longitudinal axis 12.

(39) After running through the filter element 7 of the filter device 6, the plasticized material is supplied to the space in front of the screw 17 along the longitudinal axis 12 via the screw tip 20.

(40) The carrier 8 has grooves in a radial direction in an area of the outlet opening 9 of the injection cylinder 3 in order to connect the outlet channel 15 of the backflow barrier 5 to an inner wall of the injection cylinder 3.

(41) A section slightly rotated about the longitudinal axis 12 of the embodiment of FIG. 5 is represented in FIG. 6, wherein a section through the grooves is chosen. This connection between inlet channel 15 of the backflow barrier 5 and the inner wall of the injection cylinder 3 becomes visible.

(42) A process for cleaning the filter device 6 is represented in more detail in the following FIGS. 7 to 9. First of all (see FIG. 7) plasticized material is supplied to the space in front of the screw 17 via the backflow barrier 5 and the filter device 6.

(43) Then an injection nozzle of the injection cylinder 3 is closed and an outlet opening 9 of the injection cylinder 3 is opened via a shut-off valve 10 (not represented here for reasons of clarity).

(44) In the next step, the plasticizing screw is moved in the direction of the injection nozzle of the injection cylinder 3 in the direction of the longitudinal axis 12 of the injection cylinder 3, in order to exert a pressure on the plasticized material which is present in the space in front of the screw 17.

(45) In response to the exerted pressure, the plasticized material flows back out of the space in front of the screw 17 via the filter element 7, as a result of which the filter element 7 is backflushed and cleaned of contaminants.

(46) After the plasticized material has flowed back into the inlet channel 19 of the filter device 6 or the outlet channel 15 of the backflow barrier 5 and the backflow barrier 5 closes, the plasticized material, together with the backflushed contaminants, is discharged from the injection cylinder 3 via the outlet opening 9 (for this see FIGS. 8 and 9).

(47) FIG. 10 shows a fourth embodiment of a plasticizing unit 1 according to the invention. Unlike the embodiment variants of FIGS. 5 to 9, in the embodiment of FIG. 10, the filter elements 7 of the filter device 6 do not radially enclose the plasticizing screw 4, but rather are formed in such a way that the plasticized material runs through the filter elements 7 in the direction of the longitudinal axis 12.

(48) The remaining aspects of the embodiment variant of FIG. 10 substantially correspond to those of the embodiment variant of FIGS. 5 to 9.

(49) The molding machine 2 represented by example in FIG. 11 is an injection-molding machine and has a plasticizing unit 1 and a clamping unit 30, which are arranged together on a machine frame 31. The machine frame 31 could alternatively also be formed multi-part.

(50) The clamping unit 30 has a fixed platen 23, a movable platen 22, and an end plate 21.

(51) The movable platen 22 is movable relative to the machine frame 23 via a symbolically represented knuckle joint mechanism 29.

(52) Mold halves of a mold 24 can be clamped or fitted (represented dashed) on the fixed platen 23 and the movable platen 22.

(53) The fixed platen 23, the movable platen 22 and the end plate 21 are mounted and guided relative to each other by the rails 25.

(54) The mold 24 represented closed in FIG. 11 has at least one cavity. An injection channel, via which a plasticized material can be supplied to the plasticizing unit 1, leads to the cavity.

(55) FIG. 11 shows a molding machine 2 with a plasticizing unit 1, wherein the plasticizing unit 1 shown in this embodiment has a plasticizing screw 4 formed as an injection screw, which is also used for injecting a material to be plasticized into the mold 24.

(56) The plasticizing unit 1 of this embodiment has an injection cylinder 3 and a plasticizing screw 4 arranged in the injection cylinder 3. This plasticizing screw 4 is rotatable about an axis of rotation as well as movable axially along the axis of rotation in the conveying direction.

(57) These movements are driven via a schematically represented drive unit 26. This drive unit 26 preferably comprises a rotary drive for the rotational movement and a linear drive for the axial injection movement.

(58) The plasticizing unit 1 (and thus the injection unit) is in signaling connection with a control or regulating unit 27. Control commands are for example output to the plasticizing unit 1 and/or the drive unit 26 by the control or regulating unit (controller) 27.

(59) The control or regulating unit 27 can be connected to an operating unit and/or a display device 28 or can be an integral constituent of such an operating unit and/or a display device 28.

LIST OF REFERENCE NUMBERS

(60) 1 plasticizing unit 2 molding machine 3 injection cylinder 4 plasticizing screw 5 backflow barrier 6 filter device 7 filter element 8 carrier 9 outlet opening 10 shut-off valve 11 sealing element 12 longitudinal axis 13 inlet channel of the backflow barrier 14 sealing body 15 outlet channel of the backflow barrier 16 outlet channel of the filter device 17 space in front of the screw 18 connection element 19 inlet channel of the filter device 20 screw tip 21 end plate 22 movable platen 23 fixed platen 24 mold 25 rail 26 drive unit 27 control or regulating unit 28 display device 29 knuckle joint mechanism 30 clamping unit 31 machine frame