PLASTICIZING UNIT FOR A SHAPING MACHINE AND METHOD FOR OPERATING OF SUCH ONE

Abstract

A plasticizing unit for a shaping machine for plasticizing a material to be plasticized, wherein at least one plasticizing screw is rotatably mounted in a plasticizing cylinder and stationarily mounted in relation to a longitudinal axis of the plasticizing cylinder, wherein the plasticizing cylinder has at least one opening at a periphery of the plasticizing cylinder, and that at least one opening connects the plasticizing cylinder to at least one mass storage means, and that there is provided an actuator for expelling a storage mass which can be stored in the at least one mass storage means.

Claims

1. A plasticizing unit for a shaping machine for plasticizing a material to be plasticized, wherein at least one plasticizing screw is rotatably mounted in a plasticizing cylinder and stationarily mounted in relation to a longitudinal axis of the plasticizing cylinder, wherein the plasticizing cylinder has at least one opening at a periphery of the plasticizing cylinder, and that at least one opening connects the plasticizing cylinder to at least one mass storage means, and that there is provided an actuator for expelling a storage mass which can be stored in the at least one mass storage means.

2. A plasticizing unit as set forth in claim 1, wherein the plasticizing unit has at least one discharge opening, wherein a plasticized material can be discharged from the plasticizing unit by way of the at least one discharge opening, wherein the at least one discharge opening is configured spaced from the at least one opening.

3. A plasticizing unit as set forth in claim 1, wherein the plasticizing unit has a feed device, wherein the material to be plasticized can be fed to the plasticizing unit by way of the feed device, with the feed device being configured spaced from the at least one opening.

4. A plasticizing unit as set forth in claim 1, wherein the at least one mass storage means is in the form of a piston-cylinder unit.

5. A plasticizing unit as set forth in claim 4, wherein the at least one opening is substantially of the same dimensions as the internal dimensions of the piston-cylinder unit.

6. A plasticizing unit as set forth in claim 4, wherein a piston of the piston-cylinder unit is adapted to an internal contour of the plasticizing cylinder, wherein, in an extended position of the piston-cylinder unit, the piston closes the at least one opening.

7. A plasticizing unit as set forth in claim 4, wherein a piston of the piston-cylinder unit is adapted to an external geometry of the at least one plasticizing screw, wherein in an extended position of the piston-cylinder unit the piston joins the at least one plasticizing screw.

8. A plasticizing unit as set forth in claim 4, wherein the at least one opening and/or preferably a piston of the piston-cylinder unit is of a diameter, with that diameter being in a ratio to a diameter of the at least one plasticizing screw of 0.5 to 1.1, preferably 0.8 to 1, particularly preferably 0.9.

9. A plasticizing unit as set forth in claim 1, wherein the at least one plasticizing screw is in the form of an individual plasticizing screw or in the form of a double-screw extruder.

10. A plasticizing unit as set forth in claim 1, wherein the plasticizing cylinder has at least one further opening at the periphery of the plasticizing cylinder and that at least one further opening connects the plasticizing cylinder to at least one further mass storage means, and wherein there is provided a further actuator for expelling a storage mass which can be stored in the at least one mass storage means, wherein preferably a longitudinal axis of the at least one further mass storage means and a longitudinal axis of the mass storage means are at an angle (2α) of 0° to 180° to each other.

11. A plasticizing unit as set forth in claim 1, wherein the at least one opening on the plasticizing cylinder is spaced from one end of the plasticizing cylinder, at which preferably the at least one discharge opening is arranged, by 0.2 to 4 times a diameter of the at least one plasticizing screw.

12. A plasticizing unit as set forth in claim 1, wherein the at least one mass storage means has a hydraulic and/or electrical actuation.

13. A plasticizing unit as set forth in claim 1, wherein there is provided at least one temperature-control device, preferably a heating device, wherein the at least one temperature-control device is adapted to temperature control a storage mass which can be stored in the at least one mass storage means.

14. A plasticizing unit as set forth in claim 1, wherein the actuator is adapted to specifically increase a volume of the at least one mass storage means for the feed of the plasticized material so that plasticized material can be conveyed out of the plasticizing cylinder by way of the at least one opening.

15. A shaping machine comprising a plasticizing unit as set forth in claim 1.

16. A method of operating a plasticizing unit as set forth in claim 1, including the following steps: continuously plasticizing a material to be plasticized using the at least one plasticizing screw, feeding plasticized material by way of the at least one opening in the plasticizing cylinder into the at least one mass storage means, and expelling the storage mass out of the at least one mass storage means using the actuator, wherein plasticized material is expelled from the plasticizing unit.

17. A method as set forth in claim 16, wherein the actuator is actuated for the feed of the plasticized material to specifically increase a volume of the at least one mass storage means so that plasticized material is conveyed out of the plasticizing cylinder by way of the at least one opening.

18. A method as set forth in claim 16, wherein the actuator is actuated during the feed of the plasticized material in such way that substantially no plasticized material leaks from the plasticizing unit during a period of time of the feed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Further examples, advantages and details of the invention are illustrated in the specific description hereinafter and in the Figures in which:

[0070] FIGS. 1a and 1b show a first embodiment of a plasticizing unit according to the invention,

[0071] FIGS. 2a and 2b show a second embodiment of a plasticizing unit according to the invention,

[0072] FIG. 3 shows a third embodiment of a plasticizing unit according to the invention, and

[0073] FIG. 4 shows a fourth embodiment of a plasticizing unit according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0074] FIGS. 1a and 1b show a first embodiment of a plasticizing unit 1 according to the invention, with the plasticizing unit comprising a plasticizing screw 3 arranged in the plasticizing cylinder 4.

[0075] The plasticizing screw 3 can be driven in rotation by a rotary drive 15 in the plasticizing cylinder 4 to plasticize a material 2 to be plasticized.

[0076] In this embodiment, the plasticizing screw 3 is mounted stationarily along the longitudinal axis 5 of the plasticizing cylinder 4 and carries out a continuous plasticization of the material 2 to be plasticized.

[0077] A material 2 to be plasticized is fed to the plasticizing unit 1 by way of the feed device 12 in the form of a feed hopper, wherein the plasticizing screw 3, along its screw flights, then plasticizes the material 2 to be plasticized by the rotation and the shearing heat generated thereby.

[0078] In addition, arranged along the longitudinal axis 5 of the plasticizing cylinder 4 are heating bands 16 which promote additional heating and thus plasticization of the material 2 to be plasticized.

[0079] The plasticization can be monitored and if needed closed-loop controlled by way of sensors 17 (temperature sensors).

[0080] The plasticized material 11 can then be discharged from the plasticizing unit 1 by way of the discharge opening 10 of the plasticizing unit 1, with the discharge opening being arranged at an end of the plasticizing cylinder 4, that faces away from the rotary drive 15.

[0081] In addition, the plasticizing cylinder 4 has an opening 6 at the periphery of the plasticizing cylinder 4, with that opening connecting the plasticizing cylinder 4 to a mass storage means 7.

[0082] That opening 6 is arranged at the periphery of the plasticizing cylinder 4 in a region of the discharge opening 10, wherein material 11 which has already been plasticized can pass into the mass storage means 7.

[0083] The storage mass 9 (plasticized material 11) which is stored in the mass storage means 7 can be expelled by way of the actuator 8 which in this embodiment is in the form of a hydraulic cylinder.

[0084] The mass storage means 7 in this embodiment is in the form of a piston-cylinder unit having a piston 13, with a volume of the mass storage means 7 being variable by way of the piston 13 by means of the actuator 8.

[0085] FIG. 1a shows a side view of the plasticizing unit 1 and FIG. 1b shows a section through the plasticizing cylinder 4 and the mass storage means 7.

[0086] The plasticizing screw 3 of the embodiment in FIGS. 1a and 1b is in the form of a single plasticizing screw 3.

[0087] The mass storage means 7 is connected directly to the opening 6 of the plasticizing cylinder 4, with the opening 6 being spaced by 0.5 times the diameter of the plasticizing screw 3 from one end of the plasticizing cylinder 4 at which the discharge opening 10 is arranged.

[0088] In operation mode of the plasticizing unit 1 material 2 to be plasticized can now be continuously plasticized by way of the plasticizing screw 3 and fed to the mass storage means 7, wherein the volume of the mass storage means 7 can be increased by specifica open-loop or closed-loop control of the actuator 8 in such way that the material plasticized by the plasticizing screw 3 is guided or drawn by an underpressure into the mass storage means 7.

[0089] As soon as the mass storage means has received a defined storage mass 9 of plasticized material 11, the storage mass 9 can be expelled again by way of the actuator 8 and be driven back into the plasticizing cylinder 4, with that plasticized material 11 (or storage mass 9) being expelled by way of the discharge opening 10.

[0090] By virtue of such a procedure, in spite of continuous plasticization of the plasticizing unit 1, discontinuous expulsion of plasticized material 11 through the discharge opening 10 can take place.

[0091] As can be seen from FIG. 1b, the diameter of the piston-cylinder unit is adapted to the diameter of the opening 6 so that the opening 6 transitions almost seamlessly into the cylinder of the piston-cylinder unit of the mass storage means 7.

[0092] The piston 13 of the piston-cylinder unit of the mass storage means 7 is of the same dimensions as the internal dimensions of the plasticizing cylinder 4 so that—when the piston 13 of the mass storage means 7 is in an extended position—it joins the inner peripheral surface of the plasticizing cylinder 4 and embraces the plasticizing screw 3 (as can be seen from FIG. 1b).

[0093] The piston 13 of the piston-cylinder unit is adapted to an external geometry of the plasticizing screw 3, the piston 13 fitting to the plasticizing screw 3 in the extended position of the piston-cylinder unit.

[0094] This therefore creates the possibility that, when the piston 13 completely expels the mass storage means 7, all residues and deposits from the mass storage means 7 accumulate at the end face of the piston 13 as well, with the geometrical configuration of that end face of the piston 13 and the approach movement of the piston 13 to the plasticizing screw 3 providing that the end face of the piston 13 is shearingly cleaned by the plasticizing screw 3.

[0095] This therefore provides that the mass storage means 7 cleans itself by suitable open-loop or closed-loop control, possibly in each cycle.

[0096] FIGS. 2a and 2b show a second embodiment of a plasticizing unit 1 according to the invention, wherein there is a double screw extruder 14 having two plasticizing screws 3 rotating in opposite relationship.

[0097] Here, too, the mass storage means 7 is again provided by a piston-cylinder unit, wherein the piston 13 is adapted to the geometrical configuration of the double-screw extruder 14.

[0098] FIG. 3 shows a third embodiment of a plasticizing unit 1 according to the invention, wherein there is once again provided a double-screw extruder 14 having two plasticizing screws 3 rotating in opposite relationship.

[0099] In this case, however, there are two mass storage means 7 (the mass storage means and a further mass storage means), wherein respectively one mass storage means 7 connects to respectively one opening 6 in the plasticizing cylinder 4.

[0100] The openings 6 (the opening and the further opening) of the plasticizing cylinder 4 are arranged in such way that they each can be associated with a respective plasticizing screw 3 of the double-screw extruder 14.

[0101] The mass storage means 7 each are again provided by a piston-cylinder unit, with the piston 13 being adapted to the geometrical configuration of the double-screw extruder 14.

[0102] The mass storage means 7 are at an angle 2α of about 60° relative to each other, with their longitudinal extents.

[0103] FIG. 4 shows an embodiment according to the invention of a plasticizing unit 1 which substantially corresponds to FIG. 1 but shows the actuator 8 and its open-loop or closed-loop control in a somewhat higher degree of detail.

[0104] The actuator in FIG. 4 for actuation of the mass storage means 7 is in the form of a hydraulic cylinder, a hydraulic piston subdividing the hydraulic cylinder into a first chamber 22 and a second chamber 23.

[0105] The chambers 22, 23 of the actuator are connected to the hydraulic system 18, by means of which a pressure p.sub.1 in the first chamber 22 and/or a pressure p.sub.2 in the second chamber can be varied, wherein the piston can be moved by different pressures p.sub.1 and p.sub.2 (having regard to the respective piston areas) and thus serves as the actuator 8 for the mass storage means 7 and can exert a corresponding pressure on the storage mass 9 in the mass storage means 7.

[0106] The hydraulic system for open-loop or closed-loop control of the actuator has a pump 20, a tank 21 and a hydraulic valve 19.

[0107] In the specific example in FIG. 4, a pressure p.sub.2 can be built up in the first chamber 22 by way of the illustrated position of the hydraulic valve 19 by means of the pump 20 through which the volume of the mass storage means 7 increases and plasticized material 11 can be conveyed out of the plasticizing cylinder 4 into the mass storage means 7.

[0108] Such a procedure provides that the material conveyed by the plasticizing screw 3 is preferably completely accommodated in the mass storage means 7 and particularly preferably the volume in the mass storage means 7 increases more quickly than the subsequently conveyed plasticized material 11 in the plasticizing cylinder.

[0109] This way a reduced pressure can be created for the plasticized material 11 in the mass storage means 7 and discharge of a plasticized material 11 by way of the discharge opening can be stopped or even reversed.

LIST OF REFERENCES

[0110] 1 plasticizing unit [0111] 2 material to be plasticized [0112] 3 plasticizing screw [0113] 4 plasticizing cylinder [0114] 5 longitudinal axis of the plasticizing cylinder [0115] 6 opening [0116] 7 mass storage means [0117] 8 actuator [0118] 9 storage mass [0119] 10 discharge opening [0120] 11 plasticized material [0121] 12 feed device [0122] 13 piston [0123] 14 double-screw extruder [0124] 15 rotary drive [0125] 16 heating band [0126] 17 sensor [0127] 18 hydraulic system [0128] 19 hydraulic valve [0129] 20 pump [0130] 21 tank [0131] 22 first chamber [0132] 23 second chamber [0133] α angle [0134] p.sub.1 pressure in the first chamber [0135] p.sub.2 pressure in the second chamber [0136] p.sub.3 pressure in the storage mass