PLASTICIZING UNIT FOR A SHAPING MACHINE AND METHOD FOR OPERATING ONE

Abstract

Plasticizing unit for a moulding machine having at least one plasticizing screw for plasticizing a plasticizable material and injecting it into at least one mould cavity, which at least one plasticizing screw is rotationally and axially movable in relation to a screw axis, wherein at least one filter is provided, which is arranged downstream of the at least one plasticizing screw in a direction of flow of a mass flow of the plasticizable material.

Claims

1. A plasticizing unit for a moulding machine, the plasticizing unit comprising at least one plasticizing screw for plasticizing a plasticizable material and injecting it into at least one mould cavity, the least one plasticizing screw being rotationally and axially movable in relation to a screw axis; and at least one filter arranged downstream of the at least one plasticizing screw in a direction of flow of a mass flow of the plasticizable material.

2. The plasticizing unit according to claim 1, further comprising at least one actuator for conveying the plasticizable material against the direction of flow of the mass flow in order to effect a pressure relief of a pressure of the plasticizable material bearing on the at least one filter.

3. The plasticizing unit according to claim 2, wherein the at least one actuator is formed by the at least one plasticizing screw and/or by a piston/cylinder unit, preferably in the form of a melt accumulator.

4. The plasticizing unit according to claim 3, wherein the piston/cylinder unit is arranged fluidically between the at least one filter and the plasticizing screw, or is arranged fluidically after the at least one filter.

5. The plasticizing unit according to claim 1, further comprising a filter-changing device formed to move the at least one filter out of the mass flow of the plasticizable material by a first linear movement and/or rotary movement, and/or to move the at least one filter into the mass flow of the plasticizable material by a second linear movement and/or rotary movement.

6. The plasticizing unit according to claim 5, wherein the filter-changing device is formed as a slide-plate screen changer, piston screen changer, cassette screen changer and/or belt filter.

7. The plasticizing unit according to claim 2, further comprising an open- or closed-loop control unit for activating the actuator and the filter-changing device, the open- or closed-loop control device being formed to activate the actuator to pull back against a direction of flow of the plasticizable material in order to effect a pressure relief of a pressure of the plasticizable material bearing on the at least one filter and/or to effect a backflushing of the at least one filter.

8. The plasticizing unit according to claim 7, wherein the open- or closed-loop control unit is formed to activate the filter-changing device during the pressure relief to move the at least one filter out of the mass flow of the plasticizable material and/or to move the at least one filter into the mass flow of the plasticizable material.

9. The plasticizing unit according to claim 1, further comprising at least one removal device with which plasticizable material present between at least one plasticizing screw and at least one filter is at least partially removable.

10. The plasticizing unit according to claim 9, wherein the at least one removal device has at least one discharge screw, at least one piston/cylinder unit and/or at least one outlet valve.

11. The plasticizing unit according to claim 7, wherein the open- or closed-loop control unit is formed to remove plasticizable material present between the at least one filter and the at least one plasticizing screw during the pressure relief by activating at least one removal device.

12. The plasticizing unit according to claim 1, wherein a manifold—preferably a pressure manifold—is arranged after the at least one plasticizing screw and before the at least one filter in a direction of flow of the mass flow of the plasticizable material.

13. The plasticizing unit according to claim 1, wherein the at least one filter has a screen and/or a woven fabric and/or a perforated filter unit.

14. The plasticizing unit according to claim 1, further comprising at least one scraping device for scraping the at least one filter.

15. The plasticizing unit according to claim 1, further comprising at least one seal for sealing the at least one filter against the environment.

16. The plasticizing unit according to claim 1, further comprising at least one dosing device for additives—preferably at least one gas injector—arranged before the at least one filter in a direction of flow of the mass flow of the plasticizable material.

17. A moulding machine comprising the plasticizing unit according to claim 1.

18. A method of operating the plasticizing unit according to claim 1, wherein a plasticizable material is plasticized by a rotating movement of the at least one plasticizing screw in relation to the screw axis, and the plasticizable material is injected into the at least one mould cavity by an axial movement of the at least one plasticizing screw in relation to the screw axis, wherein the mass flow of the plasticizable material is filtered with the aid of at least one filter, which is arranged downstream of the at least one plasticizing screw in a direction of flow of a mass flow of the plasticizable material.

19. The method according to claim 18, wherein the mass flow of the plasticizable material is conveyed against the direction of flow by means of at least one actuator—preferably the at least one plasticizing screw—and thus a pressure relief of a pressure of the plasticizable material bearing on the at least one filter is effected.

20. The method according to claim 19, wherein the at least one filter is moved out of and/or into the mass flow of the plasticizable material via a filter-changing device during the pressure relief.

Description

[0082] Further advantages and details of the invention follow from the figures as well as the associated description of the figures. There are shown in:

[0083] FIG. 1 a first embodiment example according to the invention of a plasticizing unit,

[0084] FIGS. 2a, 2b a filter-changing device for a plasticizing unit,

[0085] FIG. 3 a further embodiment example of a plasticizing unit,

[0086] FIG. 4 an alternative embodiment of a plasticizing unit,

[0087] FIGS. 5a, 5b embodiment variants of a plasticizing unit with several filters,

[0088] FIGS. 6a, 6b the provision of a manifold in a filter,

[0089] FIG. 7 an embodiment example of a scraping device, and

[0090] FIG. 8 a moulding machine with a plasticizing unit.

[0091] FIG. 1 shows a first embodiment example according to the invention of a plasticizing unit 1 for a moulding machine 2.

[0092] The plasticizing unit 1 has a plasticizing screw 3, which is arranged in a mass cylinder 13. The plasticizing screw 3 is drivable via a drive unit 15, wherein the plasticizing screw 3 is formed to carry out a rotary movement about the screw axis 5 and an axial linear movement along the screw axis 5, which movements can be induced by the drive unit 15.

[0093] The drive unit 15 can be controlled or regulated via an open- or closed-loop control unit 9, which open- or closed-loop control unit 9 is not represented in FIG. 1 for reasons of clarity.

[0094] Via a feed device 14, a plasticizable material can be fed to the plasticizing screw 3, wherein the plasticizable material can be plasticized by a rotary movement of the plasticizing screw 3 and can be collected in a space in front of the screw 25.

[0095] Via a subsequent axial movement of the plasticizing screw 3, the plasticized material can be pushed out of the injection cylinder 13 via the mass flow-way 12, wherein the mass flow 7 of plasticizable material is guided to a filter 6, wherein the mass flow 7 of the plasticized material can be filtered by the filter 6 and thus freed of contaminants before the mass flow 7 of the plasticized material is guided further via the mass flow-way 12 and, for example, fed to a mould cavity 4 of a moulding machine 2.

[0096] FIGS. 2a and 2b show a filter-changing device 8 for a plasticizing unit 1.

[0097] It can be seen how a material that is plasticizable via the feed device 14 can be plasticized by the plasticizing screw 3 in the mass cylinder 13 by a rotary movement and the resulting shear heat.

[0098] This plasticization can additionally be supported by band heaters 24 arranged on the mass cylinder 13, which are formed to introduce additional heat for plasticization into the mass cylinder 13.

[0099] The plasticized mass is then collected in the space in front of the screw 25 until, by a linear, axial movement of the plasticizing screw 3 along the screw axis 5, the plasticized mass is pushed out in the form of a mass flow 7 and passed through the filter 6.

[0100] In this embodiment example this filter 6 is formed as a slide-plate filter, which can be changed by the filter-changing device 8.

[0101] In order to carry out the change of the filter 6, an actuator 26 is provided, as can be seen from FIG. 2a.

[0102] In order to carry out a filter change, it can be provided that a pressure relief of the filter 6 is performed by the plasticizing screw 3, as shown by FIG. 2b.

[0103] Thus, it can be provided that pressure on the filter 6 is relieved by a linear movement of the plasticizing screw 3 in an axial direction along the screw axis 5 against the direction of flow of the mass flow 7 of the plasticizable material by pulling the mass flow 7 of the plasticizable material causing the pressure prevailing on the filter 6 back into the mass cylinder 12.

[0104] As soon as this pressure relief on the filter 6 takes place, it can be provided that the actuator 26 is activated in order to change the filter 6, wherein filter 6 is moved out of the mass flow 7 and a further filter 6 is moved into the mass flow 7 by the movement of the actuator 26.

[0105] Such a filter change can be carried out for example by an open- or closed-loop control unit 9, which is formed to control or regulate the plasticizing screw 3 (or the drive unit 15 of the plasticizing screw 3) as well as the filter-changing device 8 (via the actuator 26).

[0106] It can be provided that a corresponding filter change, as shown by FIGS. 2a and 2b, is carried out during the ongoing operation of the plasticizing unit 1, wherein the ongoing production process does not have to be stopped especially for a filter change.

[0107] Seals 27 are provided in order to seal the filter-changing device 8 against the environment.

[0108] It can also be provided that the plasticizing screw 3 is pulled back along its screw axis 5 against the direction of flow of the mass flow 7 of the plasticizable material to a greater extent in order to perform a backflushing of the filter 6, wherein material that has already been plasticized by the filter 6 is pulled back through the filter 6 in order to remove deposits that have accumulated on the filter 6.

[0109] In this embodiment example the seal 27 is pressed into a sealing position by the mass flow 7 of material to be plasticized, wherein in the sealing position the seal 7 seals the filter 6 against an environment (and thus an uncontrolled leakage of part of the mass flow 7 is prevented).

[0110] The load on the seal 27 can be relieved by a pressure relief and/or a backflushing, whereby a filter change of the filter 6 is made possible without damaging the seal 27.

[0111] FIG. 3 shows a further embodiment example of a plasticizing unit 1, wherein a piston/cylinder unit 29 is additionally provided as an actuator for conveying the plasticizable material against the direction of flow of the mass flow 7 in order to carry out a pressure relief of a pressure of the plasticizable material bearing on the filter 6 or a backflushing of the filter 6.

[0112] In this embodiment, an already plasticized, filtered material can be pushed back through the filter 6 by the piston/cylinder unit 29 in addition or as an alternative to the plasticizing screw 3.

[0113] In order to ensure that the plasticized material is pushed back through the filter 6 by means of the piston/cylinder unit 29, the shut-off valve 30 can be provided, which can be closed for pressure relief or for backflushing of the filter 6 by the piston/cylinder unit 29.

[0114] FIG. 4 shows an alternative embodiment of a plasticizing unit, wherein the additional actuator is represented in the form of a piston/cylinder unit 29.

[0115] This piston/cylinder unit 29 is arranged downstream of the plasticizing screw 3 in the direction of flow of the mass flow 7 of the plasticizable material and is arranged between plasticizing screw 3 and filter 6.

[0116] The piston/cylinder unit 29 of the embodiment example of FIG. 4 can actively carry out a backflushing or can be used in addition, in a supporting manner, to an axial movement of the plasticizing screw 3.

[0117] FIGS. 5a and 5b show embodiment variants of a plasticizing unit 1 in which several filters 6 are provided for filtration of a mass flow 7 of plasticized material.

[0118] In these embodiment variants, a plasticizable material is again plasticized via a plasticizing screw 3 and fed to a filter 6 via a mass flow-way 12, wherein a manifold 10 is arranged in the mass flow-way 12 between mass cylinder 13 and filters 6 in order to divide the mass flow 7 of the plasticizable material onto the filters 6.

[0119] Thus, for example, it can also be provided that the manifold 10 selectively guides the mass flow 7 further to one or more filters 6, whereby the possibility is created that the load on at least one filter 6 is temporarily relieved and the filtration is taken over by the remaining filters 6, with the result that the load-relieved filter 6 can be cleaned or replaced without the plasticizing unit 1 having to interrupt production.

[0120] FIGS. 6a and 6b show the provision of a manifold 10, more precisely a pressure manifold, in the application in the case of a filter 6.

[0121] Thus, for example, it can be seen in FIG. 6a that a mass flow 7 of plasticizable material is led to the filter 6, wherein the mass flow 7 can be distributed homogeneously over the entire filter 6 via the manifold 10, which is formed by flow-guiding means, with the result that the entire filter cross-section of the filter 6 can be utilized.

[0122] The embodiment example shown in FIG. 6a uses a manifold 10 which reduces or enlarges the flow cross-section in corresponding regions of the filter 6 in order to distribute the mass flow 7 as homogeneously as possible over the entire filter 6, for which purpose a flow resistance of the mass flow 7 in the individual channels is adjusted correspondingly.

[0123] As can be seen in FIG. 6b, a corresponding manifold 10, more precisely a pressure manifold, can also be arranged on either side of the filter 6 in order also to distribute an incoming mass flow 7 over the entire filter cross-section of the filter 6 during a backflushing of the filter 6.

[0124] FIG. 7 shows an embodiment example of a scraping device 11, which can be utilized in order to remove contaminants with the aid of an output device 32, which is preferably formed as a discharge screw.

[0125] In this embodiment example these scraping devices 11 of FIG. 7 are formed as positionally stable projections, which abut the filter 6. If the filter 6 is now moved relative to the scraping devices 11, a sharp edge of the scraping devices 11 is passed along the filter surface, which scrape and/or scratch off the deposits and contaminants accumulating on the filter 6.

[0126] It could, of course, also be provided that the filter 6 is formed stationary and the scraping devices 11 are movably guided against the filter 6 to scrape it.

[0127] It is also conceivable that this piston/cylinder unit 29 of FIG. 3 and FIG. 4 is used as a removal device 32. When a backflushing is carried out by the filter 6, wherein contaminants that have accumulated on the filter 6 are flushed back into the mass flow-way 12 between filter 6 and mass cylinder 13, these contaminants can be removed for example via the piston/cylinder unit 29, wherein in this embodiment example the removal device 32 formed as piston/cylinder unit 29 can, as it were, suck up the contaminants.

[0128] After contaminants have been removed by the piston/cylinder unit 29, they can be discharged from the piston/cylinder unit 29 to an environment by, for example, connecting the piston/cylinder unit 29 to the mass flow-way 12 and/or the environment via a corresponding valve circuit.

[0129] FIG. 8 shows a moulding machine 2 with a plasticizing unit 1, which can be formed for example corresponding to one of the embodiment variants shown above.

[0130] A moulding machine 2 is schematically represented in FIG. 8. This moulding machine 2 has a plasticizing unit 1 and a clamping unit 17, which are arranged on a machine frame 23.

[0131] The clamping unit 17 has a fixed moulding plate 19, a movable moulding plate 20 and an end plate 21.

[0132] In contrast to the horizontal three-plate machine represented, the clamping unit 17 could also be formed as a two-plate machine or a vertical machine.

[0133] The movable moulding plate 20 is movable relative to the machine frame 23 via a drive unit 22. A drive device 22 of this type can have for example a toggle clamp mechanism.

[0134] Mould halves of a moulding tool 18, which form a mould cavity 4 (represented by dashed lines), can be clamped or mounted on the fixed moulding plate 19 and the movable moulding plate 20.

[0135] The moulding tool 18, which is represented closed in FIG. 8, has at least one cavity 4. An injection channel, via which a plasticized mass can be fed to the plasticizing unit 1, leads to the cavity 4.

[0136] The plasticizing unit 1 has a plasticizing screw 3 arranged in an mass cylinder 13, which are formed for plasticizing a plasticizable material.

[0137] The mass flow 7 of plasticized material from the plasticizing unit 1 is then guided via the filter 6 to an injection unit 16, wherein the injection unit 16 has a degassing device 31, wherein the mass flow 7 of plasticized material can still be degassed by the degassing device 31 before being injected by the injection unit 16.

[0138] Following the degassing device 31 for degassing the plasticized material, the plasticized material is fed to the injection unit 16.

[0139] The injection unit 16 of this embodiment example has a further mass cylinder and an injection screw arranged in this mass cylinder. This injection screw is rotatable about its longitudinal axis as well as axially movable along the longitudinal axis in the injection direction.

[0140] These movements are injected via a schematically represented drive unit 15. The drive unit 15 preferably comprises a rotary drive for the rotary movement and a linear drive for the axial injection movement, as well as the drive unit 15 of the plasticizing unit 1.

[0141] The plasticizing unit is in signal-conducting connection with an open- or closed-loop control unit 9. The open- or closed-loop control unit 9 issues control commands to the plasticizing unit 1 as well as to the injection unit 16.

[0142] It can furthermore be provided that the open- or closed-loop control unit 9 is connected in a signal-conducting manner to a filter-changing device 8 in order to control or regulate the filter-changing device 8.

[0143] The open- or closed-loop control unit 9 can be connected to an operating unit or can be an integral component of such an operating unit.

LIST OF REFERENCE NUMBERS

[0144] 1 Plasticizing unit [0145] 2 Moulding machine [0146] 3 Plasticizing screw [0147] 4 Mould cavity [0148] 5 Screw axis [0149] 6 Filter [0150] 7 Mass flow [0151] 8 Filter-changing device [0152] 9 Open- or closed-loop control device [0153] 10 Manifold [0154] 11 Scraping device [0155] 12 Mass flow-way [0156] 13 Mass cylinder [0157] 14 Feed device [0158] 15 Drive unit [0159] 16 Injection unit [0160] 17 Clamping unit [0161] 18 Moulding tool [0162] 19 Fixed moulding plate [0163] 20 Movable moulding plate [0164] 21 End plate [0165] 22 Clamping mechanism [0166] 23 Machine frame [0167] 24 Band heater [0168] 25 Space in front of the screw [0169] 26 Actuator [0170] 27 Seal [0171] 28 Further manifold [0172] 29 Piston/cylinder unit [0173] 30 Shut-off valve [0174] 31 Degassing device [0175] 32 Removal device