AT518422B1 - Storage container for a molding machine - Google Patents

Abstract

Storage container (1), in particular plasticizing unit or shot-pot unit, for a shaping machine (13), with a cylinder (2), which has a longitudinal axis (L), a piston (3) rotatably mounted in the cylinder (2) Adjusting device (4) for adjusting the position (x) of the piston (3) relative to the cylinder (2) along the longitudinal axis (L) of the cylinder (2) and a gap measuring device (5) for measuring one between the cylinder (2) and the Piston (3) existing gap (s), wherein the position (x) of the piston (3) via the adjusting device (4) in dependence of the gap measuring device (5) measured gap (s) is adjustable.

Description

Description: The present invention relates to a storage container, in particular plasticizing unit or a shot-pot unit, for a forming machine, comprising a cylinder having a longitudinal axis, a cylinder rotatably mounted in the piston and an adjusting device for adjusting the position of the piston relative to the cylinder along the longitudinal axis of the cylinder. In addition, the invention relates to a molding machine with such a storage container.

A general injection device with a simple adjustment for adjusting a distance between the screw tip and cylinder inner wall is apparent from WO 2014/157711 A1. In this case, the gap is adjusted via a nut in the rear area of the screw.

In other previously known adjusting devices for adjusting the position of the plasticizing screw, the front injection position of the screw is set via a displacement measuring system. An example of this is DE 196 19 730 C2, in which a sensor is arranged in the rear region of the screw and monitors a distance between a cylinder plate and a carrier plate. This indirectly draws a conclusion between a gap between the screw tip and the injection piston. By monitoring the gap, it is possible to control the constant mass supply to the screw. The maximum gap width is fixed by retaining bolts and nuts. A disadvantage of such displacement measuring systems is that thermal expansions and tolerances are not taken into account. Although mechanical stops ensure collision freedom, the entire system is usually not tuned. That is, the columns are not currently being set. In the case of thermally unstable or strongly wall-adhering melts, deposits that are too low and, as a consequence, thermal degradation occur.

In JP 2012-192694 A must first be driven to stop with the worm cylinder for detecting the size of the gap, resulting in a detected by the load cell (load cell) "limit position" results. Then the screw is retracted until a certain preset distance has been covered. This distance is detected by an encoder. At this preset distance, adhesion and deterioration of the melt quality are avoided. This avoids varying the gap size. That is, with each injector, this gap is adjusted properly via a test run. Thus, no fixed relative axial position between the worm and the cylinder is established, but before or during the first operation of each injection device the machine-to-machine limit position (stop between the worm and the cylinder) is determined and, starting from this limit position, the worm is moved backwards is detected up to the specified gap value, which relative position between the screw and cylinder is given when reaching the specified gap value. This relative position is then used as a value for further operation. Thus, although an individual setting is possible with each machine, but this method is more like an estimation method. That is, the actual size of the gap value is unknown. Rather, the gap value is determined approximately only indirectly via a force transducer. Heat expansions, tolerances and changes in other parameters between injection cycles can not be taken into account, which can lead to adverse injection results, since the estimated gap value no longer (or at least not always) coincides with the actual gap value.

The object of the present invention is to provide a comparison with the prior art improved or alternative to the prior art storage container. In particular, the mentioned disadvantages should be avoided. In particular, the molded part quality should be consistent over a variety of production cycles.

This is achieved by a storage container having the features of claim 1. Accordingly, according to the invention, a gap measuring device is provided for measuring a gap existing between the cylinder and the piston, wherein the position of the piston is adjustable via the adjusting device as a function of the gap measured by the gap measuring device. Thus, not only is an estimated or indirectly determined gap value approximately detected, but a direct measurement of the gap is performed. Based on this specific measured value, a possible adaptation of the gap via the adjusting device can then be carried out continuously, as a result of which the desired amount of melt can be applied, which in turn contributes to a constant quality of the molded part.

Although a measuring sensor is already known from AT 510 024 B1, with which the distance between plasticizing and plasticizing screw can be measured, however, it can only be deduced on the wear of the screw.

Further advantageous embodiments of the present invention are specified in the dependent claims.

In order to measure the gap which influences the final component quality, it is provided according to a preferred embodiment that the piston has a piston tip which tapers at least partially, wherein the gap measuring device measures the distance or the gap between the cylinder and the at least one partially tapered piston tip of the piston takes place. In principle, the piston tip can taper substantially uniformly. This results in a conical shape of the piston tip. The surface of the piston tip may be formed in section but at least partially parabolic. Other forms of the piston tip are possible as long as a discharge of melt from the storage container is thereby made possible.

Furthermore, it is preferably provided that the piston has a arranged at the front end of the piston return flow block. This is particularly useful when the piston is designed as a plasticizing screw and thus the plasticizing screw melts by turning both supplied starting material in the screw flights of the screw body as well as injected by a longitudinal movement relative to the plasticizing the molten material into a mold. In such an embodiment, the non-return valve forms the tapered piston tip. The use of a gap measuring device for gap control has the advantage that regardless of different operating conditions and temperatures of components such as pistons and mass cylinder, especially in large Plastifizierag-gregaten, the gap between the mass cylinder flange and the backflow valve regulated and thus influencing the cleaning behavior by changing the flow conditions Variation of the gap can be brought about. Backflow barriers are not necessary, for example, in the treatment and injection of PVC.

The adjusting device for adjusting the position of the piston may be formed, for example, such that via a drive unit, a support plate on which a drive motor for rotatably driving the piston is mounted relative to a base plate to which the cylinder is mounted, movable is.

For measuring, it is preferably provided that the gap measuring device has a measuring sensor and an evaluation unit. In principle, this measuring sensor can be arranged in the piston, in particular in its return flow blocking device. Preferably, however, it is provided that the measuring sensor is arranged in the cylinder, preferably in a nozzle flange of the cylinder.

For a meaningful measurement result of the measuring sensor is directed to the tapered piston tip, whereby the distance between the piston tip and cylinder inner wall is measurable.

In principle, the measuring sensor, in particular its tip, can form the inner wall of the cylinder. However, the measuring sensor is preferably arranged in a blind bore formed in the cylinder. As a result, between the tip of the measuring sensor and the cavity in the cylinder is still a distance of preferably a few millimeters, whereby the measuring sensor is not exposed to the high pressures and temperatures in the cavity of the cylinder.

Particularly preferably it is provided that the measuring sensor is an ultrasonic measuring sensor or a magnetostrictive sensor. Alternatively, the measuring sensor can also be designed as an induction sensor. This can also be changed in his position.

Although the gap measuring device can detect a direct contact between the piston and cylinder, but the measurement is not based (only) on a stop from the piston on the cylinder. Rather, a size different from 0 of the gap between the piston and cylinder is measured via the gap measuring device.

According to a preferred embodiment, the storage container on a control or regulating unit for controlling or regulating movements of the storage container. This control unit can also control or regulate the entire forming machine. For a simple operation of the storage container can be provided that the adjustment device can be controlled or regulated via the control unit. In addition, the control unit can be connected to the evaluation unit of the measuring device or the educate unit along. Thus, the adjusting device is controlled or regulated via the control or regulating unit as a function of the gap measured by the gap measuring device, so that the corresponding position of the piston is adjusted relative to the cylinder.

In addition, a measuring device for measuring a change in length of the piston may also be provided. In order to be able to achieve an even more constant quality of the molded part, the position of the piston via the adjusting device is additionally adjustable as a function of the change in length of the piston measured by the measuring device.

Protection is also desired for a molding machine, in particular for an injection molding machine or a spray press, with a storage container according to the invention. Such a shaping machine has a closing unit in addition to the storage container. This closing unit comprises a fixed platen, a movable platen, a drive unit for moving the movable platen and a mold arranged on the platen. The mold halves of this mold form at least one cavity into which molten melt is injected via the storage container. After curing of the injected melt, the mold is opened and the cured molded part (injection molded part) ejected.

Further details and advantages of the present invention will be explained in more detail below with reference to the description of the figures with reference to the embodiment shown in the drawing. 1 shows a section through a storage container, and [0022] FIGS. 2 and 3 show alternative arrangements of the measuring sensor.

In Fig. 1, a cross section through a front portion of a storage container 1 is shown in detail. In addition, other components are shown schematically. The storage container 1 (in this case, a plasticizing unit) forms, together with a closing unit, not shown, a shaping machine 13, for example an injection molding machine or injection press.

The storage container 1 has a piston 3 (in this case a plasticizing screw) with a piston body 19 and a return flow lock 7. The return flow lock 7, in turn, is composed of the piston tip 6 connected to the piston body 19, for example via a screw connection, and the sleeve 20 partially surrounding the piston tip 6. The cylinder 2 of the storage container 1 has, as essential components, the cylinder housing 14, the nozzle flange 10 and the channel element 15. Around the cylinder 2 heating bands 16 are arranged. In the cylinder 2, the piston 3 is rotatable and arranged linearly displaceable along the longitudinal axis L. The linear displaceability is achieved by a, preferably hydraulic, hydromechanical or electrical adjusting device 4. It is schematically illustrated that the adjusting device 4 is fastened to a carrier 17. This Trä ger 17 is in turn firmly connected to the cylinder 2. The adjusting device 4 may, for example, have a rotatable nut with an internal thread. Only the axial adjustment of the position x is shown here. If the piston 3 is designed as a plasticizing screw, then a rotary drive for this plasticizing screw is also provided (not shown here). By turning said nut, the position x of the piston 3 along the longitudinal axis L is changed via a corresponding external thread on the piston 3. As a result, the gap s also changes between the surface of the piston 3 and the inner wall of the cylinder 2. This gap s is measured via a gap measuring device 5. In particular, the measuring sensor 8 of this gap measuring device 5 is arranged in a blind bore 18 of the nozzle flange 10. Thus, the measuring sensor 8 is arranged at a distance from the cavity filled with melt in the cylinder 2. In this case, the gap s is measured perpendicular to the surface of the piston tip 6. From the measuring sensor 8, a corresponding signal via a signal line 21 to the evaluation unit 9 of the gap measuring device 5 is transmitted. In this case, this evaluation unit 19 is part of a control or regulation unit 11 of the shaping machine 13. Via this control or regulation unit 11, the adjustment device 4 can also be activated via a signal line 22. In particular, therefore, the position x of the piston 3 is adjustable via the adjusting device 4 as a function of the gap s measured by the gap measuring device 5. In addition, it is also possible to provide a schematically indicated measuring device 12 for measuring the change in length of the piston 3, whereby this measurement can also be included in the setting of the position x.

In Fig. 2, the piston 3 is shown in a rear position xh in the cylinder 2. In addition, it is illustrated that the measurement of the gap s via the measuring sensor 8 can also be radial. Dashed line is also indicated that a measurement of the gap s can be performed as axially.

Fig. 3 shows the piston 3 still in its forward position xv in the cylinder 2, whereby the - has decreased in this case radially measured - gap s. REFERENCE LIST: 1 storage container 2 cylinder 3 piston 4 adjustment device 5 gap measuring device 6 piston tip 7 backflow barrier 8 measuring sensor 9 evaluation unit 10 nozzle flange 11 control unit 12 measuring device of length change 13 forming machine 14 cylinder housing 15 channel element 16 heating tapes 17 carrier 18 blind bore 19 piston body 20 sleeve 21 signal line 22 signal line L longitudinal axis x position of the piston xh rear position xv front position s gap

Claims (14)

claims 1. Storage container (1), in particular plasticizing unit or shot-pot unit, for a shaping machine (13), having - a cylinder (2) which has a longitudinal axis (L), - a piston (2) rotatably mounted in the cylinder (2) 3), and - an adjusting device (4) for adjusting the position (x) of the piston (3) relative to the cylinder (2) along the longitudinal axis (L) of the cylinder (2), characterized by - a gap measuring device (5) for measuring a gap (s) present between the cylinder (2) and the piston (3), wherein the position (x) of the piston (3) via the adjusting device (4) depends on the gap (s) measured by the gap measuring device (5) is adjustable. 2. Storage container according to claim 1, wherein the piston (3) has an at least partially tapered piston tip (6), wherein by the gap measuring device (5) measuring the gap (s) between the cylinder (2) and at least partially tapering Piston tip (6) of the piston (3). 3. Storage container according to at least one of the preceding claims, wherein the piston (3) has a return flow lock (7). 4. Storage container according to claim 2 and 3, wherein the return flow lock (7) forms the tapered piston tip (6). 5. Storage container according to at least one of the preceding claims, wherein the gap measuring device (5) has a measuring sensor (8) and an evaluation unit (9). 6. Storage container according to claim 5, wherein the measuring sensor (8) in the cylinder (2), preferably in a nozzle flange (10) of the cylinder (2), is arranged. 7. Storage container according to claim 5 or 6, wherein the measuring sensor (8) is directed to the tapered piston tip (6) and the distance between the surface of the piston tip (6) and inner wall of the cylinder (2) is measurable. 8. Storage container according to at least one of claims 5 to 7, wherein the measuring sensor (8) is an ultrasonic measuring sensor or a magnet-based, preferably a magnetostrictive, sensor. 9. Storage container according to at least one of the preceding claims, with a control or regulating unit (11) for controlling or regulating movements of the storage container (1). 10. Storage container according to claim 9, wherein the adjusting device (4) via the control or regulating unit (11) is controlled or regulated. 11. Storage container according to claim 9 or 10, wherein the control or regulating unit (11) with the evaluation unit (9) of the gap measuring device (5) is connected or the evaluation unit (9) mitbildet. 12. Storage container according to at least one of the preceding claims, with a measuring device (12) for measuring a change in length of the piston (3). 13. Storage container according to claim 12, wherein the position (x) of the piston (3) via the adjusting device (4) in dependence of the measuring device (12) measured length change of the piston (3) is adjustable. 14. shaping machine (13), in particular injection molding machine or injection press, with a storage container (1) according to at least one of the preceding claims. For this 2 sheets of drawings