DE1197611B - Screw press for injectable materials such as B. Plastics - Google Patents

Description

Screw press for injectable materials such as plastics The invention relates to a screw press for injectable materials, such as thermoplastics.

There are known screw presses in the area of the screw tip an annular gap adjustable in cross section between the screw tip and a Have narrowing of the compression channel, so that by axial displacement of the screw the throttling effect can be adjusted to achieve the required melt pressure can. Furthermore, vented extruders are known in which a throttle point - in Direction of the material flow as seen - directly in front of the degassing opening through a Annular bead of the screw on the one hand and an annular groove in the wall of the press channel on the other hand is formed. In this case, too, the throttling effect is axial Shifting of the press screw changed.

It has been shown that, especially with difficult to process Plastics, these known throttling options are not sufficient to achieve a qualitative to achieve high quality product.

The invention is based on the object of a screw press for To create injectable materials with the help of which the quality of the injection-molded product can be significantly improved even with plastics that are difficult to process. This is done in a screw press with a throttle point at the screw tip in the form of an adjustable annular gap between one centrally through the screw guided, axially displaceable needle and a narrowing of the compression channel provided is achieved in that between the screw tip and the feed opening a second throttle point is provided for the material through the screw on the one hand and the wall of the compression channel on the other hand is formed and that the The screw press is mounted so that it can be moved in the axial direction according to the invention thus has two throttle options which can be set as desired on, so that the mass pressure in a wide range on each to be processed Plastic can be matched, and so it is possible to find the cheapest in each case Achieve result. It is particularly useful - if there is a degassing opening between the second throttle point and the screw tip in the immediate vicinity the second throttle point is located. But even if there is no special vent opening is provided, the second, previous throttle point is advantageous because the at the pressing temperature gaseous constituents for the most part upstream of the throttle point return- held and pushed back into the funnel when it accumulates will. The screw press according to the invention also has the advantage that both throttling points centrally from the end of the screw by the operator can be adjusted.

It is already a screw press with one in the screw axial displaceably guided needle and a narrowing provided in the area of the needle tip of the press channel known. The needle has a thickened kneading head at its tip on, which, like the constriction, is provided with ribs, so that in the case of the intended Rotation of the needle a mixing effect is achieved. The by shifting the needle The throttling effect that can be achieved is, however, particularly even with the narrowest gap setting with regard to the ribs on the mixing head and on the opposite surface of the Narrowing and the intended rotation of the mixing head only slightly.

In a further embodiment of the invention, the screw can over support a thrust bearing on a piston, which is held displaceably in a cylinder and the one with a hydraulic or pneumatic adjustable pressure source communicates. The screw can be moved axially by adjusting the pressure ad the throttling effect and the melt pressure inside the screw press will. Advantageously, the highest pressure build-up can be applied to the baling channel in the area pressure measuring devices must be connected to one or all of the throttle points, those with mechanical, hydraulic or pneumatic drive devices for axial displacement of the worm and / or the needle are connected in such a way that that the position of the screw depends on the measured pressure value or the measured pressure value and / or the needle is automatically controllable.

In the drawing, an embodiment of the invention is shown, the further features - can be found in the invention. 1 shows a screw press according to the invention, partly in view, partly in section, FIG. 2 is a partial section through the press cylinder of the screw press according to FIG. 1, -F i g. 3 a partial section through the press cylinder of the screw press according to Fig. 1, with the needle and screw are shown in a different position.

As shown in FIG. 1, there is the screw press according to the Invention of a housing 1 in which a press cylinder is provided. The press cylinder has an opening 3 for introducing the material to be pressed; which is followed by a filler box 4 at the top. He - is also with a second Provided opening 5, which serves as a degassing opening and a degassing shaft per se 6 connects. At the mouth of the press cylinder, a press head 7 is flanged in This is held in the embodiment, a Donn 8, which is used to shape the to be pressed Hoses is used. The press head 7 is also designed so that it is close to the mouth of the press cylinder 2 has a point with a particularly small diameter and here a constriction 9 of the; Forms compression channel.

In the press cylinder 2 narrow press screw 10 is rotatable and axially displaceable held. The screw ends with its - tip 'shortly before the constriction 9 of the press head7. At its other end, the screw is supported by an annular collar 11 on a pressure sleeve 2 away. Riie connection of collar 11 and pressure sleeve is such that the collar and so that the worm is taken along when the pressure sleeve 12 rotates.

The pressure sleeve 12 engages in a longitudinal groove 4 with the aid of a wedge 13 a rotating sleeve 15. The groove 14 is formed so long that an axial displacement the pressure sleeve 12 compared to the rotary sleeve 15 is possible. The rotary sleeve is with the help a bearing 16 rotatably held in the machine housing. There is a drive pinion on it 18 attached for the rotary drive of the screw 10, the one not shown Drive motor is connected.

The pressure sleeve 12 is supported by a tapered roller bearing Pressure bearing 19 on a piston 20, which is longitudinally displaceable in a cylinder 21 is held. The interior of the cylinder 21 is via a line 22 with a Oil pressure pump as a pressure source 23 in connection. By changing the oil pressure, the position of the screw 10 can be changed in the axial direction.

The screw 10 has a central longitudinal bore along its entire length provided through which a needle 23 is passed. At the end of the screw is a guide a longitudinal sleeve 24 is provided which protrudes into the annular collar 11 of the screw.

The needle 23 is supported at its end opposite the tip on a thrust bearing 25, which is in a pressure body designed as an adjusting sleeve 26 is held. The adjustment sleeve is threaded on its circumference and engages into a corresponding thread of a stationary part 27 of the machine housing a. When turning the sleeve, the needle is displaced in the axial direction. For turning the sleeve can be one in the Motor 28 indicated by dash-dotted lines is provided be that via a chain or belt drive 29 with a pinion or a pulley 30 of the sleeve 26 is in communication.

The screw press shown in the drawing has two throttle points on whose free cross-section can be changed, so that an adjustment of the Melt pressure prevailing in front of the throttle points is possible. One of those throttling points is provided in the area of the screw tip. It is caused by the narrowing9 of the Pressing head on the one hand and formed by the tip of the needle 23 on the other hand. Will the needle 23 is withdrawn by a corresponding rotation of the sleeve 26, so the free cross-section between the needle tip and the constriction9 is enlarged. In 2 shows the needle 23 in this open position. A twist of the Sleeve 26 in the opposite direction has a displacement of the needle 23 to the left result, so that the free cross-section between the needle tip and the constriction 9 is increasingly reduced. A corresponding position of the needle 23 is shown by F i G. 3. The mass pressure in front of the constriction 9 is high in this case.

The second throttle point is shown in the exemplary embodiment Screw press seen in the direction of the material flow shortly before the degassing opening 5 provided. It consists of an annular groove 31 of the press cylinder 2 on the one hand and a corresponding annular bead 32 of the screw 10 on the other hand. Depending on the position the screw 10 and thus the annular bead 32 to the annular groove31 can have the free cross-section of the annular gap between groove 31 and bead 32 can be changed as a function of this the mass pressure prevailing in front of this throttle point increases or decreases. 2 shows a position of the screw, in which the cross section of the annular gap between groove 31 and bead 32 is greatest. 3 shows the screw 10 in one Position in which the free cross-section between groove 31 and bead 32 is reduced is, so that a higher throttling effect and thus a higher mass pressure in front of this Throttle point is effected.

Both throttle points are in the screw press according to the invention completely independently adjustable. The cross section of the throttle point the screw tip can, as mentioned, be changed by rotating the sleeve 26. Since the needle 23 has only a relatively small cross section, it prepares there is no displacement of the needle against the melt pressure, even during operation Difficulties so that this can be done by hand. But it is also as in the exemplary embodiment adjustment by mechanical devices is possible.

Since the snail has a larger size due to its larger cross-section Absorbs part of the melt pressure, it is adjusted appropriately as in the exemplary embodiment by hydraulic or mechanical or pneumatic aids. The independent Setting both throttling points enables the auger to respond very well to changing Set operating conditions and with different material and throughput to achieve the best mixing and degassing effect in each case.

To with changing operating conditions, z. B. fluctuating feed quantity etc., in order to be able to maintain the optimal operating conditions, it is advisable to seen in the direction of the estate stream in front of one or both throttle points To connect pressure measuring devices to the baling channel and with the mechanical, hydraulic or pneumatic drive devices for axial displacement of the screw or to connect the needle in such a way that depending on the pressure reading the position the screw and / or the needle can be controlled. This is e.g. B. in Fig. 1 with reference shown on the throttle point at the top of the press. A pressure gauge 33 is in connection with the baling channel shortly before the constriction 9 via a pressure line 34, so that the measuring device shows the mass pressure prevailing there. The engine28 that goes to Rotation of the sleeve 26 is used for the axial displacement of the needle 23, has a control device 35, to which the measured values of the measuring device 33 are fed via a line 36 and that the action of the engine 28, e.g. B. controls in such a way that the pressure before the constriction9 is constantly constant by a corresponding displacement of the needle 23 is held. A corresponding measuring and control device can also be used in connection be provided with the throttle point present in front of the degassing opening 5 and the position of the screw 10 via the hydraulic pump 23 or a corresponding one control another drive device.

The control, in particular the axial position of the press screw, can also depend on other factors, such as throughput rate, screw speed and the like.

Claims (4)

Claims: 1. Screw press for injectable materials, such as B. thermoplastics, in which a throttle point at the screw tip in the form of an adjustable annular gap between one centrally through the screw guided, axially displaceable needle and a narrowing of the Press channel provided is, d adur ch e k e n n -draws that between the screw tip and the feed opening (3) a second throttle point (31, 32) is provided for the material through the screw (10) on the one hand and the wall of the press channel on the other hand is, and that the worm is mounted for itself displaceably in the axial direction. 2. Screw press according to claim 1, characterized by a degassing opening (5) between the second throttle point (31, 32) and the screw tip in the immediate vicinity Near the second throttling point. 3. Screw press according to claim 1 or 2, characterized in that that the screw (10) is supported on a piston (20) via a thrust bearing (19), which is held displaceably in a cylinder (21), and that the cylinder (21) with a hydraulic or pneumatic, adjustable pressure source in connection stands. 4. Screw press according to one of the preceding claims, characterized characterized in that on the press channel in the area of the highest pressure build-up on one or all throttle points pressure measuring devices (33) are connected with mechanical, hydraulic or pneumatic drive devices (28,35) for axial displacement of the screw (10) and / or the needle (23) in such a connection stand that depending on the measured pressure value or the measured pressure values, the position the screw and / or the needle is automatically controllable. Documents considered: German Auslegeschrift No. 1 047417; German utility model No. 1 805 842; French patent specification no. 901 31, 168 923, 1192493; U.S. Patent Nos. 2449652, 2,970,341.