DE2245551A1 - PLASTICS PROCESSING MACHINE WITH A DEVICE FOR THE CONTROL OF SETTING SIZES ON CONTROL VALVES - Google Patents

Description

DEMAG Aktiengesellschaft, 41 Duisburg

Plastic processing machine with a device for Control of setting variables on control valves.

The invention relates to a plastics processing machine with a device for controlling setting variables on control valves, consisting of a stationary Housing and a part movable therein, with control signals being converted into a mechanical movement of a certain length.

Plastics processing machines are understood to mean machines which deals with the processing of plastics into plastic products deal. In such machines, during a functional sequence, i. H. Plasticizing, mold closing, nozzle feed, Injection, a large number of control processes are carried out, whereby there is also an exact setting of control valves arrives. With control valves of this type, hydraulic pressures and hydraulic quantities are predominantly the respective corresponding ones Adjusted to requirements. Were such values that one for the respective plastic to be processed and that accordingly plastic product to be manufactured empirically determined, previously set and readjusted by hand, then one goes in the course of the advancing automation of plastics processing machinery more and more about programming the function sequence. For this purpose, the once empirically determined operating parameters, which - as mentioned - also include pressures and quantities, are used as a target

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data stored in a data carrier. This can e.g. B. over a logic circuit can be made by means of which this Operating variables via a function type selector switch in memory locations a digital memory made up of integrated circuits. These entered Target data, which can also be corrected manually at any time according to the functional sequence of the machine in the memory, can be downloaded from of the machine or entered manually. The machine is optimally adjusted and controlled by means of these values. The mentioned storage of operating parameters for programming a machine was only for general understanding addressed, is therefore not the subject of the invention and therefore does not need to be explained in more detail.

The setpoint data that are sent to the machine and the values of which the control valves are to be set to must be in strokes implemented »so that they can be processed by the control valves. This can be the case with a plastics processing machine z. B. to the setting of a valve for pressure regulation during the plasticizing process to act accordingly set the correct dynamic pressure for the material to be processed. This dynamic pressure to be set exactly has an essential. lent influence on the feed and melting conditions of the the plastic to be processed and the quality of the plastic product made from it. The ones mentioned here Valves / z. B. for pressure adjustment and readjustment to a required value, can be set in such a way that - illustrated schematically - a displaceable in the valve housing

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under variable spring force standing conical Element has a flow cross-section defined in the inflow area releases. If it is necessary to change the set values, the spring preload is changed by means of a stroke adjustment via a piston arranged in the valve housing. These The stroke adjustment must be carried out very precisely so that the required values are precisely adhered to. To control such control valves special solenoids are known in which the armature executes a stroke according to the size of the applied voltage. This is an analog control device, since a movement takes place according to the respective voltage magnitude. Such Facilities have considerable disadvantages because, on the one hand, the. applied voltage values are not always reproducible in the Required stroke lengths are implemented and, on the other hand, that these devices are affected by the counterforce of the control valve to be set are dependent. Furthermore, there must be no fluctuations in the applied voltage values because they are not exact constant, this immediately results in a deviation from the required stroke length to be set. With increasing stroke lengths there is an ever increasing tolerance in the areas to be adhered to. Values on. Since the establishment also largely from the opposing force depends on the control valve to be set, the force of the actuating magnet must be matched to the control valve to be set are, in turn, inaccuracies in the stroke setting occur when the valve is a little stiff is to use. Occurring temperature fluctuations also result in deviations in the end result. To address these disadvantages Compensating for the well-known institutions, one is already

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went over to it, constantly via a special additional device Compare the setpoint with the actual value and identify deviations to compensate for a readjustment device. As a result, a considerable additional effort is required, in addition to the high costs of the actuating magnet gives an extra indolence.

The invention has therefore set itself the task of creating a device through which control valves for controlling plastic Processing machines with the required precision and reproducibility, eliminating the aforementioned disadvantages, can be set, whereby an essential feature of the task is the elimination of the influence of the opposing force of the control valve is on the control process. According to the invention, this object is achieved in that, in contrast, in a housing a restoring force movable piston-cylinder units are arranged one behind the other, which are directly connected to each other in the Are in contact so that the piston with the piston rod of one unit is in contact with the cylinder of the adjacent unit touches and one of the two external piston-cylinder units is in communication with an outwardly movable element arranged in the housing, each piston-cylinder unit having a predetermined one Stroke is assigned and the piston-cylinder units each individually via control signals by releasing pressure medium are controllable, the stroke or strokes of the piston-cylinder units as the sum of the outwardly movable element without influencing the end result by the opposing force of the to regulating valves can be reproducibly transferred. lim an exact Adjustment of the setting device to the particular one to be controlled

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To achieve the control valve of the plastics processing machine advantageously included that one of the external piston-cylinder units is in contact with an adjusting screw arranged in the housing, via which the piston-cylinder units can be adjusted to the required zero position.

The embodiment according to the invention is particularly characterized by a problem-free mode of operation with high reliability and Accuracy required for controlling control valves on plastic Processing machines are required so that, not least, inadmissibly high loads are avoided with certainty the correct functioning is still guaranteed and thus high-quality plastic certificates are obtained. The one for precise control and adjustment of the control valves various required setting strokes are adapted to this by 'the' piston cylinder units arranged in the setting device already specified exactly and now only need to be controlled accordingly to achieve the required stroke to be transferred to the control valve. This is very advantageous to any readjustment or position feedback device that was previously necessary to achieve the desired stroke, waived.

Another important advantage of the invention is that the adjusting device is independent of the required strokes the different force with which a control valve, depending on the make and the function to be fulfilled, the setting process counteracts, reliably adjusts. This in the functional

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Structure of the setting device-justified advantage is achieved in that the piston-cylinder units with a pressure medium be applied to such a level that all disturbance variables that occur are compensated for with certainty. In more advantageous In an embodiment of the invention, the piston-cylinder units are designed as pressure cells for this purpose.

Further details and advantages of the present invention are given below in exemplary embodiments with reference to the drawings explained in more detail.

In the drawings shows:

1 shows a longitudinal section through a device according to the invention · ...

FIG. 2 shows a longitudinal section corresponding to FIG. 1, from which, as an exemplary embodiment, a stroke adjustment by actuation two piston-cylinder units emerges and

3 shows an injection molding machine operating according to the invention, in which, in accordance with the stroke adjustment in FIG Use case is shown.

From Fig. 1, a housing 1 can be seen in which four cylinders 2, 3, 4, 5 arranged one behind the other with the same outer diameter are slidably mounted, each of which in turn has one. Piston 2 ', 3', 4 ', 5 ^{1 is assigned} with the same dimensions.

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On these pistons there are piston rods 6, 7, 8, 9 with increasing Length arranged according to the required strokes, in each case the piston with the piston rod of the one unit with the Cylinder of the adjacent unit is in direct contact, that is, the rod 6 of the piston-cylinder unit 2, 2 * rests directly on the cylinder 3 of the subsequent piston-cylinder unit 3, 3 'and in a corresponding manner the number of piston-cylinder units consecutively. The housing is on one side by a housing cover 10, which means Screws 11 is attached and in which an adjusting screw 12 is arranged with lock nut 13, completed. On the other On the side of the housing, a housing cover 14 provided with a thread 15 is flanged with screws 16, in which a movable Element 17 arranged with an annular extension 18 is. A restoring force constantly acts on the piston-cylinder units, which holds the units in the starting position in the non-actuated state, as well as after actuation of one or more Units will automatically move them back to their starting position. For this purpose, a spring 19 is provided, which is arranged around the movable element 17 and at one end of the annular Approach 18 and at the other end of a recess 20 in the housing cover 14, in which the spring 19 engages, limited will. Furthermore, a distributor block 21 for the hydraulic supply is arranged on the housing 1, which can be electrically operated Multi-way valves 22, 23, 24, 25 are assigned. In the distributor block 21, a central supply line 26 is provided, which is from a pump, not shown here, is supplied with pressure medium and furthermore a collecting line 27 to the tank via which

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on the one hand, the hydraulic medium flowing back when the pressure in the piston-cylinder units is relieved and, on the other hand, the excess hydraulic medium can be diverted in the event of leakage oil losses. A branch 28 each leads from the central supply line 26 to the individual multi-way valves 22, 23, 24, 25, via which the multi-way valves are constantly under pressure. A feed line 29 leads from the individual multi-way valves 22, 23, 24 to the respectively adjoining annular space 30, which is formed by a recess in each cylinder 2, 3, 4, 5 and the adjoining housing wall of the housing 1. These individual annular spaces 30 are designed so that their expansion corresponds to the sum of all strokes and the resulting displacement of the individual cylinders 2, 3, 4, 5 in the> housing 1, so that with each cylinder displacement, the connection between the respective Supply line 29 and the associated annular space 30 remains. From the respective annular space 30, the pressure medium passes on through the bore 31 arranged in each cylinder 2, 3, 4, 5 for direct action on the respectively controlled pistons 2 ¹ , 3 ', 4 ¹ , 5'. The individual strokes of the pistons 2 ', 3 ¹ , 4 ¹ , 5 ¹ are predetermined by the corresponding different lengths of the piston rods 6, 7, 8, 9. The movement of the piston rod of the respectively acted upon piston is limited in its defined length in that the corresponding piston comes to a stop on the cylinder cover 32 of the associated cylinder. The cylinder covers 32, which are fastened to the respective cylinder with fastening bolts 33, serve in addition to the task of partially closing the cylinders 2, 3, 4 and thus also to the piston

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To precisely lock pressurization in the end position in order to largely avoid oil leakage, the cylinders 2, 3, A, 5, which slide with their outer wall on the inner wall of the housing 1, are provided with corresponding seals 34.

As can be seen in more detail from Fig. 2 *, in this embodiment, the piston-cylinder units 3, 3 ¹ and 5, 5 ^{1 are} acted upon with pressure medium, whereby the movable element 17 moves by the required total stroke, which corresponds to the sum of the two precisely specified individual strokes, moved outwards. This required stroke adjustment, with which, according to the application example in Fig. 3, a pressure setting valve 35 for back pressure regulation of an injection molding machine is set / is a precise adjustment of the cylinders 2, 3, 4, in the housing 1 and thus the movable element 17 in adaptation by means of the setting screw 12 preceded by the conditions at the pressure adjustment valve 35. The control signals arriving at the magnets 36 of the multi-way valves 23 and 25 cause these multi-way valves to be switched from the zero position centered by springs 37 to the actuating position. As a result, the pressure medium now flows into the respectively released supply lines 29 and reaches the bores 31 via the annular spaces 30 for the direct application of pressure to the two pistons 3 ¹ and 5 '. As a result, the piston 3 'comes to a stop on the cylinder cover 32, the associated piston rod having moved outward by the predetermined amount. As a result of the movement of the piston rod 7, the piston-cylinder units 4, 4 'and 5, 5 ¹ in the housing 1 are simultaneously moved by the stroke of the piston rod

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22A5551

displaced, with the piston rod 9 being displaced outward by the predetermined amount at the same time by the application of pressure. The two added strokes of the piston rods 7 and 9 are transmitted to the outwardly movable element 17, whereupon the spring 19 arranged to generate the restoring force is pretensioned accordingly. The movable element, which is a plunger 17 in an embodiment according to the invention, has moved outward by the required total stroke, which is equal to the sum of the two individual strokes. According to the four piston-cylinder units arranged in the housing 1 according to the exemplary embodiment, which in an advantageous embodiment according to the invention are designed as pressure cells 2, 2 ', 3, 3 ¹ , 4, 4 ¹ , 5, 5 ¹ , it is possible by controlling the Pressure cells individually or in total according to the underlying law of 2 ⁿ - 1 possible to achieve 15 adjustment strokes, where η = number of pressure cells. The adjustment options can be considerably expanded by arranging additional pressure cells. The strokes can advantageously be provided in such a way that the respective predetermined stroke of the individual pressure cell is preferably twice the previous pressure cell, the pressure cell 5, 5 ¹ with the largest predetermined stroke being directly connected to the plunger 17 arranged in the housing 1 stands. In addition, depending on the respective requirements, it is also possible to assign the strokes to the pressure cells within other limits. For this purpose, the actual device can easily remain in place, with only the piston rods needing to be screwed out of the piston and exchanged for others with a different stroke length. Should the one driven outwards by a defined stroke

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If the plunger 17 is now brought back into the starting position, the control signals at the Menrwegeventilen 23 and 25 are removed, whereupon the two multiway valves are switched to the zero position via the applied spring pressure of the springs 37. Then by the multipath% ^r alves the connections 23 and 25 between the central lead 26 and the lead will be 'interrupted, whereupon the spring acting as a restoring force 19, the pressure cans 4, 4' 29 to the two pressurized containers 3/3 * and 5, 5 and 5 _r 5 ¹ moves back into the starting position. The pressure medium in the cylinders 3 and 5 is now conveyed via the line 29 to the return line 38 and further via the collecting line to the tank. Corresponding quantities of leakage oil that accumulate between the pressure cells and in the housing are also discharged via the respective annular spaces 39 to the collecting line 27 to the tank.

The injection molding machine shown in Fig. 3, on which after Invention a pressure adjustment valve 35 for regulating the back pressure is controlled, is in this embodiment on the injection unit 40 with partially shown injection mold 41 has been restricted. Enter that into the material hopper 42 Plastic material is fed by the plasticizing screw 43, which is rotatably and axially displaceably mounted in the plasticizing cylinder 44, is drawn in and conveyed in the direction of the spray nozzle 45. The rotational movement of the plasticizing screw 43 is via a corresponding drive motor, which is arranged in the housing 46, made. The axial displacement of the screw 43 is by pressurizing the piston 47 in the injection cylinder 48 is arranged, achieved. On the execution of the

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Drive motor and its coupling to the plasticizing screw as well as the functioning of the axial displacement of the screw by actively applying pressure to the piston 47 is not intended here will be discussed in more detail.

The screw 43 tends to move forward due to the plastic mass constantly being conveyed by it - in accordance with the Rotational movement - to move axially backwards continuously. In this way it reaches the collecting space in front of the screw head Plastic compound, among other requirements, is not sufficiently compressed and homogenized, which affects the quality of the plastic part to be manufactured has an adverse effect. In which addressed plasticizing process, efforts are made to reduce the intake and To optimize melting conditions for the plastic material as much as possible. For this it is necessary to use the plasticizing screw 43, which is located at the beginning of the plasticizing process in front position is located in the plasticizing cylinder 44, an adjustable Oppose resistance. This adjustable resistance of the different plastic masses to be processed and must be precisely adapted and adjusted to the corresponding injection molding requirements, is done by a so-called passive back pressure achieved. For this purpose, the pressure medium located in the piston-side space 50 of the injection cylinder 48, with which via the pump 51, the line 52, the three-way valve 53 and the line 54 was pressurized during the injection process of the piston 47, included. The three-way valve 53 gives this only the connection of the line 54 to the pressure adjustment valve 35, the so-called back pressure valve, is free. This pressure adjustment valve 35 is, as already described under FIG. 2, by means of

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the setting device 1 ', into which the stored control signals of a program are entered, are set exactly to the fed-in values. The hydraulic medium, which is pressed by the continuously moving back plasticizing screw 43 from the space 50 of the injection cylinder 48 via the line 54 to the back pressure valve 35 and from there to the tank line 59 in the tank 60, stops the axial movement of the screw required resistance. Due to the hydraulic medium flowing into the back pressure valve 35, the valve cone 55 has lifted itself from its valve seat by a defined amount, against the spring force of the spring 56, in order to release the flow cross section that corresponds to the set back pressure. If the dynamic pressure is to be varied, corresponding signals are sent to the setting device I ¹ , which are converted into a longitudinal displacement of the plunger 17 and, via the plunger, move the control rod 58 on the adjusting piston 57 of the dynamic pressure valve 35 accordingly During the plasticizing process, the plasticizing screw 43 with the injection plunger is in the rear position, whereupon the control signals from the setting ^{device I 1 are} removed and both the plunger 17 and the pressure setting valve 35 return to their starting position can convey the space 50 and the plasticized plastic is thereby injected into the mold 41.

The control signals that are processed by the setting ^{device I 1} are, according to the exemplary embodiment, electrical signals that, for. B. via a transistor logic of an injection molding program

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are further processed until they are used as control signals for the multi-way valves Activate 22, 23, 24, 25. Beyond that, it's after the invention possible to use a pneumatic logic instead of a transistor logic, by means of which the programmed Control signals are then fed pneumatically to corresponding pneumatic valves, which also precisely control the pressure cells. In consistent continuation of this control option, the hydraulic pressure medium can also be dispensed with, since the pressure cans can easily be pressurized with compressed air while maintaining the functional accuracy, Another important advantage of the invention is, in addition to the high level of adjustment accuracy, without being influenced by variable counter-forces of the individual control valves to be set can be reproduced exactly, independence from voltage fluctuations the control signals. Since the size of the control signals no longer has any influence on the stroke lengths to be set, only needs just make sure that the respective directional control valve is activated. This is synonymous with the pneumatic control closed, in which pressure fluctuations at the pneumatic directional control valve have no influence on an exact stroke adjustment to have.

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Claims (9)

Claims 1. Plastics processing machine with a device for steering y tion of setting variables on control valves, consisting of a stationary housing and a movable part therein, with control signals being converted into a mechanical movement of a certain length, characterized in that piston-cylinder units (2, 2 ·, 3, 3 ' _T 4, 4', 5, 5 ') are arranged one behind the other, which are in direct contact with one another in such a way that the piston with piston rod of one unit touches the cylinder of the adjacent unit and one of the two outer piston-cylinder units is connected to an outwardly movable element (17) arranged in the housing (1), each piston-cylinder unit (2, 2 ¹ , 3, 3V, 4, 4 '/ 5, 5' ) a predetermined stroke is assigned and the piston-cylinder units can each be individually controlled via control signals by releasing pressure medium, with the stroke or strokes of the piston-cylinder units ( 2, 2 \, 3, 3 *, 4, 4 ', 5, 5 ¹ ) can be reproducibly transferred as the sum to the outwardly movable element (17) without influencing the end result by the counterforce of the valves to be controlled. 2. Plastic processing machine with a device according to Claim 1, characterized in that one of the external piston-cylinder units is arranged with one in the housing (1) 4098 13/0597 - 15 - ■ Adjusting screw (12) is in contact , via which the piston-cylinder units (2, 2 ·, 3, 3 ¹ , 4, 4 ¹ , 5, 5 ') can be adjusted to the required zero position. 3. Plastics processing machine with a device according to claim 1, characterized in that the piston rods (6, 7, 8, 9) are designed to be interchangeable with such of any size for the purpose of changing the individual strokes. 4. Plastics processing machine with a device according to one or more of claims 1, 2 and 3, characterized in that the piston-cylinder units as pressure cells (2, 2 ¹ , 3, 3 ¹ , 4-, 4 ', 5, 5') are trained. 5. Plastics processing machine with a device according to one or more of the preceding claims, characterized in that the cylinders (2, 3, 4, 5) of the individual pressure cans (2, 2 ¹ , 3, 3 ', 4, 4', 5, 5 ') are sealed on the inner wall of the housing (1) by means of seals (34). 6. Plastic processing machine with a device according to one or more of claims 1, 2 and 4, characterized in that that the respective predetermined stroke of the individual pressure cell is preferably twice the previous one Pressure cell, the pressure cell (5, 5 ') with the largest predetermined stroke directly with the one arranged in the housing (1), outwardly movable element (17) is in connection. 40981 3/0597 7. Plastics processing machine with a device according to claim 1 or 6, characterized in that the outwardly movable element is a plunger (17). 8. Plastic processing machine with a device according to Claim 1, characterized in that the control signals from an electrical control to electrically actuatable Directional valves (22, 23, 24, 25) or from a pneumatic control to pneumatically operated directional valves will. 9. Plastics processing machine with a device according to claim 1, characterized in that the restoring force for moving the piston-cylinder units (2, 2 ¹ , 3, 3 ¹ , 4, 4 ', 5, 5 ¹ ) in the starting position by means of a spring ( 19) is generated. A09813 / 059 Blank page