DE202011000322U1 - injection molding - Google Patents

Abstract

Injection molding device with a plastic feed device (16), a cylinder (18, 20) for receiving a plastic supplied via the plastic feed device, a screw (28) for conveying the plastic within the cylinder (18, 20) to an outlet opening of the cylinder, a first motor (42), preferably an electric servomotor, for rotating the worm (28), a second motor (52), preferably an electric servomotor, for rotating a nut component (50) which is connected to a spindle (38) carrying the worm (28) in this way It is operative that when the nut component (50) and the spindle (38) rotate at different speeds, an axial movement of the worm (28) is caused; characterized by a regulating device for regulating the torque of the second motor (52), the torque of the second motor being regulated to a value corresponding to the pressure in order to apply a predetermined pressure to a plastic located in the cylinder.

Description

The present invention relates to an injection molding apparatus for plasticizing and injecting thermoplastic material.

Previous state of the art

From the Austrian utility model AT 004 744 U1 a method for monitoring the injection process of an injection molding machine is known in which the pressure in the plastic is constantly monitored. From the EP 1 344 623 A1 as well as from the US 4,851,171 are each related to methods of controlling back pressure in injection machines operated by an electric motor. In the two methods, a sensor for direct measurement of the pressure is used in each case.

The pressure generated during plasticizing must be precisely monitored in order to be able to control the drive of the machine. The use of a pressure sensor has disadvantages. For example, the pressure sensors used are error-prone.

In the DE 101 35 539 A1 a method for controlling the dynamic pressure in an injection molding machine is described. The injection molding machine comprises an injection unit with a first motor for axially displacing a plasticizing screw and a second motor for rotating the screw, both motors acting on the screw via a common shaft. According to this method, a default value for the rotational speed of the one engine (metering motor) is determined in a first control loop, and this value is fed to another control circuit for the other engine (injection engine) as a setpoint specification. From a target-actual difference for the dynamic pressure, a speed difference is determined, which is added to the setpoint specification and used to control the injection motor. Thus, speed setpoints are set or set in a first control loop and position-dependent pressure data are determined in a second control loop. Both motors initially receive the same default value for the speed. Subsequently, the speed difference required for a pressure setpoint is determined and added to the speed setpoint. According to this method, it is thus provided first to measure the back pressure (actual value (p _ist )) and to compare it with a desired dynamic pressure (nominal value). According to this difference, a required speed difference is adjusted to provide the desired pressure.

From the JP 61-0 16 826 A An injection molding machine emerges. According to this injection molding machine is provided to determine the position of the screw from the cumulative difference of the rotational frequencies of the two motors. In this case, the location or the position of the worm is thus determined from the speed difference of the motors.

In the DE 10 2004 045 493 A1 is described a drive for an injection molding machine. This drive has two electric motors, which are arranged coaxially to each other. One of the motors is designed as a hollow shaft motor. By using a hollow shaft motor, a more compact design of the electric machine should be possible because the two motors can be nested inside each other. Furthermore, position encoders are provided for control. A first position sensor is provided for determining the position position of the first electric motor and a second position sensor is provided for determining the position of the second electric motor. By means of the position sensor, the motors are adjustable in their position or speed.

In the EP 13 21 837 A2 a method for controlling two motors is described. According to this document servo inverters are used.

In the US 47 55 123 A a method for controlling an injection molding machine is described. In this case, the rotational speed and the back pressure of the spindle should be controllable in dependence on the position of the screw by means of a torque limitation, in order to obtain an optimum state of plastification of the molten material.

In the DE 20 2004 010 812 U1 An injection molding machine with an integrated displacement measuring system is described. This position measuring system comprises a position sensor and an active position transducer for measuring a position of the position sensor, which is integrated in a linear guide.

In the AT 0 02 813 U1 a control device for an injection molding machine is described. In this case, a control line separated from a field bus is to be used to transmit a setpoint value of a controlled variable of a servomotor.

Summary of the invention

The object of the present invention is to avoid the disadvantages of the prior art. In particular, it is an object of the invention to provide an injection molding apparatus which is simple, reliable and responsive in terms of injection pressure and / or back pressure adjustable.

At least part of the above objects is solved by the features of the independent claims. Preferred embodiments and further developments of the invention, which Solve special subtasks form the subject of the dependent claims.

According to one aspect of the present invention, an injection molding apparatus comprises: a plastic supply means, a cylinder for receiving a plastic supplied through the plastic supply means, a screw for conveying the plastic inside the cylinder to an exit port of the cylinder, a first motor, preferably an electric servomotor, for rotating the worm, a second motor, preferably an electric servomotor, for rotating a nut member operatively engaged with a shaft carrying the worm such that when the nut member and the worm shaft rotate at different speeds, axial movement of the worm is caused a control means for controlling the torque of the second motor, wherein for applying a predetermined pressure to an in-cylinder plastic, the torque of the second motor is controlled to a value corresponding to the pressure.

The inventors have found that when the cylinder is filled with plastic, the axial force of the screw is generated or held solely by the rotation of the second motor. The axial force is thus proportional to the torque of the second motor. The axial force, in turn, determines the pressure exerted by the worm on the plastic, the pressure resulting from the axial force divided by the cross-sectional area of the worm.

The relationship between the torque of the second motor and the pressure in the cylinder is still by further effects and sizes, such. B. the friction of the individual components and the pitch of the screw. Despite these influences, the relationship between the torque of the second motor and the pressure in the cylinder is linear. This makes it easy to adjust the pressure in the cylinder based on the torque of the second motor.

It is surprising that the pressure in the cylinder is independent of the torque generated by the first motor, which also acts on the worm. However, this torque alone acts against frictional forces, which are also understood to mean the internal forces in the plastic to knead the plastic mass in the cylinder. Essential for the present invention is the knowledge that only the second motor, the axial force is generated on the worm shaft and thus on the worm. Based on this knowledge, it is possible to precisely regulate the pressure in the cylinder based on the torque of the second engine without the pressure in the cylinder being measured with a pressure sensor.

With the invention, the back pressure or injection pressure is not measured with a sensor and regulated in a closed loop, but adjusted by specifying the torque of the second motor. The pressure is thus controlled and not regulated. Only the torque at the second motor can be controlled.

The injection molding apparatus may be constructed such that at least one, preferably each of the first and second motors is a torque motor. Under a torque motor is understood in the context of the invention, a servo motor with a hollow shaft. Torque motors can be mounted directly on the drive shafts of the machines without mechanical intermediate elements such as gears, clutches, belts or the like. They are characterized by a consistently high torque over the entire speed range. The elimination of mechanical intermediate elements leads to a reduction in space requirements, the total weight and maintenance costs and to increase the rigidity and dynamics of the construction. Torque motors can be water-cooled and are equipped as standard with a rotor position and speed signal generator. The direct torque transmission, the rigidity of the overall structure and the detection of the pressure across the speed difference cooperate in the sense of a precise control of the drive elements of the injection molding together in an advantageous manner.

It can be provided that each of the motors is assigned a servo inverter.

Particularly preferably, it can be provided that both servo inverters are combined in a common servo inverter unit for both motors.

The servo-controller can be designed with a safety function that shuts off the respective motor when a certain preset torque is exceeded. Preferably, the shutdown of the engine by being de-energized, in particular by interrupting a contact, in particular a relay. Furthermore, the motor can be alternatively or additionally braked electrically or mechanically when the torque is exceeded. Such a brake is useful if it is to be prevented that due to the prevailing pressure, the screw should not move further. Servo motors with servo inverters, in which such a safety function is integrated, is, for example, from the manual ACOPOSmulti with SafeMC, user manual, Version 1.00, Order No .: MAACPMSAFEMC-GER of the company Bernecker + Rainer Industrie-Elektronik Ges.m.b.H. known. This function is described in chapter 4.2 Functional Fail Safe state (pages 176 to 179).

This safety function is preferably designed so that when a certain torque is exceeded by the second motor, at least the second motor and preferably both motors are turned off.

The injection molding apparatus may be configured to include a displacement detecting means for detecting an axial displacement of the screw. With the path detection device, the location of the screw and thus the filling volume of the cylinder can be determined.

Preferably, it can be provided that the path detection device has an angle difference detection device for detecting an angular difference between a rotation angle of the first motor and a rotation angle of the second motor. If the starting position of the motors and the worm are known ("zeroing" of the angular difference), the difference between the angles of rotation of the two motors corresponds to the axial displacement of the worm.

Additionally or alternatively, it can be provided that the displacement detection device has a displacement transducer, preferably a magnetorestrictive non-contact displacement transducer. A transducer may be used to solely determine the axial displacement of the worm, or to zero the angular difference detection, or to control and compensate for adder errors in angular difference detection. Magnetorestrictive displacement sensor are, for example, constructed so that in a central tube, a wire is arranged, which is set in vibration. On the tube, a magnetic ring is slidably disposed, wherein the ring may contain a plurality of individual magnets or may be a monolithic magnet. This magnet influences the resonance behavior of the wire located in the central tube. From this, the location of the magnetic ring can be determined. The resolution is very precise and can be up to 0.02 mm. The magnetic ring may be coupled to the spindle via a non-magnetic disk. As a result, the location of the spindle can be detected in a comparatively simple and cost-effective manner. Particularly preferably, the displacement transducer can be arranged like the end of the spindle within the first motor designed as a torque motor or servomotor. These torque motors are, as mentioned above, hollow, which makes the entire structural arrangement very compact.

Particularly preferably, it can be provided that the displacement transducer has a digital output and this is directly connected to the servo controller. If the transducer has an analog output, the analog signal must be supplied to a controller, which then generates a control signal for driving the servo.

Particularly preferably, it can be provided that the servo inverters have an analog signal processing section for processing analog signals as controlled variables. If the servo-inverter can process only digital signals, an analog signal of a displacement sensor must be fed to a control device, which then generates a (digital) control signal for driving the servo-converters. With the embodiment according to the invention analog sensor signals can be used directly, whereby the pressure to be set in the cylinder can also be specified by an analog signal and can be integrated into a control loop.

The invention may also be embodied as a method of operating an injection molding apparatus.

Brief description of the drawings

Other aspects, advantages and features of the present invention will become apparent from the following description and the accompanying drawings of a particularly preferred embodiment of the invention. In the figures show:

1 an overall view of an injection unit in a preferred embodiment of the invention;

2 is a detail view of a detail II in 1 with a nozzle end of the injection unit of 1 ; and

3 is a detail view of a detail III in 1 with a in the injection unit of 1 built-in displacement sensor.

Description of a preferred embodiment

A particularly preferred embodiment of the invention will be explained below with reference to the accompanying drawings. It shows 1 an overall view of an injection unit 10 in a preferred embodiment of the invention, and 2 and 3 show details.

As shown in 1 has an injection unit 10 a plasticizing section 12 and a drive section 14 on. The plasticizing section 12 has a hopper 16 , a front cylinder part 18 and a rear cylinder part 20 on. The front cylinder part 18 and the rear cylinder part 20 are firmly connected and together form a cylinder in the sense of Invention. The front cylinder part 18 has an end nozzle 22 on.

The rear cylinder part 20 has a filling opening 20a on. At the height of the filling opening 20a is at the rear cylinder part 20 a filler neck 24 Flanged, and this is in turn the hopper 16 flanged. To the front cylinder part 18 around are some heating and cooling facilities 26 arranged.

In the cylinder 18 . 20 runs a screw conveyor 28 , The screw section of a connection point of the filler neck 24 to the front end of the screw conveyor 28 runs (see also 2 ). At its rear end is the screw conveyor 28 connected to a drive train, which will be explained later. First, the front end of the injection unit 10 based on the illustration in 2 explained.

In 2 is the nozzle end of the front cylinder part 18 shown enlarged in longitudinal section. The section shown corresponds approximately to one by a dashed line II in 1 marked detail.

As shown in 2 has the front cylinder part 18 a longitudinal bore 18a on. The longitudinal bore 18a runs essentially over the entire length of the front cylinder part 18 and takes the auger 28 on. In a face 18b of the front cylinder part 18 are a threaded blind hole 18c and from the bottom of an exit channel 18d educated. The nozzle 22 has a threaded pin 22a and a nozzle channel 22b with an exit taper 22c on. The threaded pin 22a is in the thread blind hole 18c the nozzle 22 screwed. The end face of a threaded pin 22a and the hole bottom of the threaded blind hole 18c are close together. The nozzle channel 22b has the same diameter as the outlet channel 18d of the front cylinder part 18 up and aligned with this. Between a front face 28a the screw conveyor 28 and the end of the longitudinal bore 18a is a compression space 30 defined for conveyed by the screw conveyor and plasticized sprayed.

As shown in 1 becomes the front cylinder part 32 through a bearing block 32 held on a solid base (machine bed, fixed floor or the like). The rear cylinder part 20 is through a bearing block 34 and a connecting collar flanged thereto 36 held on the solid surface.

The following is a description of the drive section 14 of the injection unit 10 , The drive section 14 has a drive spindle 38 and two electric motors 42 . 52 whose interaction will be explained in the course of the following description.

The screw conveyor 28 is at its rear end to a drive spindle 38 connected, which at its other end a wedge 38a having. The axial connection of the drive spindle 38 with the screw conveyor 28 done by means of a long tie rod screw 40 passing through an axial bore in the drive spindle 38 passes through. A connecting sleeve 41 ensures a torsionally rigid connection between the drive spindle 38 and the screw conveyor 28 , The drive of the drive spindle 38 via a water-cooled torque motor (rear torque motor) 42 standing by a bearing block 44 is held on the firm surface. Torque motors are electric servomotors with a hollow shaft, which can be mounted directly on the drive shafts of the machines without mechanical intermediate elements such as gears, clutches, belts or the like. The rear torque motor 42 is in the context of this description as a spindle motor 42 referred to as the drive spindle 38 of the injection unit 10 drives. For this purpose, the wedge pin engages 38a the drive spindle 38 in a splined bush 46 connected to the hollow shaft of the spindle motor 42 via a coupling member 48 connected is. The keyway bush 46 and the wedge 38a can transmit torques, but are mutually axially displaceable.

The drive spindle 38 has an external thread in its main area 38b on. On the external thread 38b a mother sits 50 (also as spindle nut 50 referred to) by a second torque motor 52 (also as mother engine 52 designated) is driven. For this purpose, the spindle nut 50 via a coupling member 54 with the hollow shaft of the mother motor 52 connected. The mother engine 52 is also a water-cooled torque motor and is supported by a bearing block 56 held on the solid surface. When the drive spindle 38 in the spindle nut 50 turns, the drive spindle 38 perform a translational, axial movement. The spindle nut 50 is a parent component within the meaning of the invention.

By controlling the mother motor 52 can the spindle nut 50 be set in rotating motion. The rotational movement of the spindle nut 50 is about the external thread 38a in a translational, axial movement of the drive spindle 38 translated. In this way, the screw conveyor 28 axially displaced and the volume of the compression chamber 30 at the tip of the screw ( 2 ) to be changed. If the mother engine 52 and the spindle motor 42 rotate at the same speed, there is no axial displacement of the screw conveyor 28 ,

Torque motors have a rotor with permanent magnets and a stator with winding poles. The stator has a plurality of poles, whereby a high torque can be generated. Torque motors are characterized by consistently high torque across the entire speed range and have proven to be space-saving and efficient drive elements in systems engineering, which can generate high torques even at low speeds right up to standstill. The torque motors 42 . 52 are equipped with a signal transmitter for rotor position and speed. Servo inverters (not shown in detail in the figures) control the torque motors 42 . 52 with respect to the rotational speed and / or torque, wherein both parameters can be controlled or regulated simultaneously. The two engines 42 . 52 can be controlled by the same parameters or by different parameters. Thus, one of the two motors Drehzal- and the other motor can be torque-controlled. The invention was successfully tested with torque motors of the type designation 1FW3 from Siemens AG. These torque motors are delivered fully assembled as complete motors.

The axial displacement of the drive spindle 38 , the axial displacement of the screw conveyor 28 corresponds, is by means of a transducer 60 with the rear end of the trunnion 38a coupled, recorded or measured. The transducer 60 is by means of a lid 62 on the bearing block 44 of the spindle motor 42 attached.

For controlling and regulating the injection unit 10 is a central computer and / or decentralized electronic control units are provided, which are connected to each other via data lines or individually. The control units can be embodied in the (programmable) servo inverters. It is also conceivable that a single servo inverter for both torque motors 42 . 52 is provided jointly. In this case, there is also a servo inverter unit for both motors within the meaning of the invention.

In 3 is the drive end of the drive spindle 38 or their pivot pin 38a shown enlarged in longitudinal section. The section shown corresponds approximately to one by a dashed line III in 1 marked detail.

3 shows in particular the construction and installation of the transducer 60 , At the injection unit 10 The present invention uses a magnetorestrictive non-contact transducer with analog or digital output. This magnetorestrictive non-contact transducer 60 has a projecting from a Einschraubgehäuse in which the actual measuring electronics, projecting central tube 62a on. In the pipe 62a There is a wire (not shown), which is set by the measuring electronics in vibration. On the pipe 60a is a magnetic ring 60b slidably disposed, wherein the ring may contain a plurality of individual magnets or may be a monolithic magnet. This magnet ring 60b influences the resonance behavior of the central tube 60a located wire. The magnetic ring 60b is about a non-magnetic disk 60c with the rear end of the drive spindle 38 or the wedge 38a coupled. From the vibrational response of the wire, the location of the magnetic ring 60b be determined. The invention has been successfully tested with a magnetorestrictive transducer of the type IK1 A GEFRAN spa. These transducers have an analog output. The resolution is very precise and can be up to 0.02 mm. As a result, in a relatively simple and inexpensive manner, the location of the drive spindle and thus the screw conveyor 28 be detected.

It should be noted that the magnetic ring 60b during the process turns. This affects the functionality of the transducer 60 according to experience with a first prototype of the present invention. The present arrangement is structurally very compact, since the position transducer 60 as well as the end of the spindle 38 ( 38a ) within the worm motor 42 ( 1 ) are arranged. These torque motors are hollow, which makes the overall structure very compact.

If a displacement transducer is used with analog output, the analog signal must be supplied to a control device, which then generates a control signal for driving the servo controller. If a sensor with digital output is used, it can be connected directly to the servo inverter, shortening the control loop and allowing fast and precise control. With correspondingly designed servo inverters, it is also possible to process analog signals directly as a controlled variable.

The injection unit is operated and controlled as follows.

About the hopper 16 , the filler neck 24 and the filling opening 20a becomes the rear cylinder part 20 a sprayed material (plastic granules or the like) supplied. By controlling the spindle motor 42 becomes the drive spindle 38 set in rotating motion, and over the hopper 16 etc. fed by the screw conveyor 28 in the front area of the front cylinder part 18 promoted and thereby plasticized, it being about the heating and cooling units 26 on a desired temperature is maintained. In the compression room 30 collects the plasticized sprayed material is compacted and homogenized there and passes through the outlet channel 18d and the nozzle channel 20b . 20c out.

The spindle motor 42 is driven during the plasticizing with a predetermined speed NS or a predetermined torque TS.

The mother engine 52 stops while filling the cylinder parts 18 . 20 a certain, small torque TM0, so that the spindle nut 50 with the same rotational speed as the screw conveyor 28 turns, provided that on the screw conveyor 28 no axial force acts. This torque TM0 only serves to overcome the frictional forces. Would the spindle nut 50 not by the mother engine 52 would be turned, the screw conveyor 28 due to a relative rotational movement between the spindle nut 50 and the drive spindle 38 move in the axial direction.

When a motor is driven at a particular speed or torque, it means that a controller controls the motor to rotate at the predetermined speed, or so that the motor generates the predetermined torque. The control device can be integrated, for example, in the servo controller.

When the cylinder parts 18 . 20 are filled with plastic, then builds up due to the plasticizing in the plastic mass, a pressure p on which the screw conveyor 28 applied with a rearward force Fp. If you continue to drive the mother engine only with the small torque T0, then this would lead to the screw conveyor 28 through the spindle nut 50 would be pushed backwards.

This filled state of the cylinder parts 18 . 20 you can detect. For example. you can detect the speed of the mother motor and the spindle motor, and the screw conveyor 28 is moved to the rear, then sets a speed difference of the two engines, which is determined by the two detected speeds. On the other hand, you can also the movement of the screw conveyor with the transducer 60 detect.

When the filled state of the cylinder parts 18 . 20 is detected, then the mother engine 52 operated with a torque T1. With this torque T1, the pressure in the plastic mass is counteracted. Therefore, the torque T1 corresponds to the pressure p in the plastic mass. The torque T1 is proportional to the pressure p in the plastic mass, as will be explained in more detail below.

The volume to be injected is transmitted through the transducer 60 measured way measured. The injection unit 10 can also be used so that in the mold injected plastic compound is tracked during cooling. During cooling, the plastic mass shrinks in the mold. Therefore, it is expedient to track the plastic compound with a certain pressure. This pressure is in turn controlled by controlling the screw conveyor 28 applied torque T1 (of the spindle motor 42 ) generated.

In a starting situation, the screw conveyor is located 28 in their front end position (as in 1 shown).

The spindle motor 42 turns over the keyway bush 46 the wedge 38a and thus the drive spindle 38 and the coupled auger 28 , Due to the rotational movement, plastic granulate is conveyed in the direction of the screw tip, in the heated front cylinder part 18 melted and accumulates in the compression chamber 30 in front of the screw tip (end face 30 in 2 ). When the compression space 30 filled with plastic compound, then the filled state is reached and the torque of the mother motor 52 is switched from the small torque T0 to a larger torque T1.

The resulting pressure pushes the screw back until a preselected capacity is reached. (This process is known per se.) In the torque-controlled operation of the mother motor 52 leaves the spindle nut 50 an axial movement of the screw conveyor 28 to.

By the mother engine 52 generated counter-torque, via the spindle nut 50 an axial counterforce on the drive spindle 38 and thus on the screw conveyor 28 exerts a backflow in the plastic melt, which leads to the improvement of the homogeneity and allows a very accurate metering of the melt.

A dosage tolerance of 0.3 g per 100 g shot weight is currently possible.

As soon as the preselected filling quantity has been reached, the supply of further plastic granules is terminated and the pressure in the plastics material is terminated by the torque T1 of the mother motor 52 held.

When opening the nozzle, the plasticized plastic mass is extruded from the compression chamber, wherein the mother motor 52 about the spindle nut 50 and the drive spindle 38 the screw conveyor 28 moved axially forward to the starting position. The plastic melt exits the injection unit at high pressure. Here, the screw conveyor 28 not rotated, that is, the spindle motor is controlled at the speed 0.

The pressure generated during plasticizing must be set exactly. This is already known from the prior art and is monitored in the prior art by means of a pressure sensor, which experience has shown is very error-prone. According to the invention, the pressure on the torque T1 of the mother engine 52 eingstellt. It has been shown that the regulation of the torque of the mother motor 52 much faster than a pressure control with a pressure sensor via a control loop.

In the plasticizing and dosing described above, a control of the torque of the mother motor 52 used.

The relationship between the parent engine 52 and the pressure p, which is in the compression space 30 can be represented as follows: T _M = k · p · A · r · tanφ where T _{M is} the parent motor torque, φ the pitch angle of the spindle 38 is, r the length of the lever arm of the spindle 38 where A is the cross-sectional area, p is the pressure in the compression space 30 and k is a correction factor, which is the moment when moving the empty auger 28 represents. The correction factor k is determined in advance when turning the empty conveyor screw.

Furthermore, applies A = D2 · π / 4 where D is the diameter of the cylinder, and tanφ = h / (d · π) where d is the diameter of the spindle 28 is and h is the pitch of the spindle 28 is. The pressure p was measured at different engine torques and represents a linear relationship to the moment.

The operator presets the setpoint. The actual value is calculated from the motor torque via a conversion factor, consisting of the screw diameter and spindle pitch, included in the control system and displayed. The manipulated variable is the torque of the mother motor.

This arrangement allows a very high accuracy of the setting of the pressure of better than 1%, since the torque of the mother motor can be controlled accordingly precise.

The present injection unit 10 is mechanically very simple, since neither gear nor clutches or the like are provided. The control takes place exclusively via the servo inverters of the motors 42 . 52 , which control the speed or torque of the two motors by means of voltage and frequency. The adjustment of the pressure and the measurement of the location are very precise and are fed back very quickly, so that the injection unit 10 works very precisely and can inject plastic quantities very accurately.

A method of operating an injection molding apparatus having a plastic supply means, a cylinder for receiving a plastic supplied through the plastic supply means, and a feed screw for conveying the plastic inside the cylinder to an exit port of the cylinder, a first motor, preferably an electric servomotor, for rotating the screw, and a second motor, preferably electric servomotor, for rotating a nut, which is in operative engagement with a shaft carrying the worm, that, when the nut does not rotate at the same speed as the shaft, an axial movement of the worm causes, Adjusting the torque of the second motor, so that by means of the torque a predetermined pressure in the plastic is adjusted. This process is preferably carried out with the cylinder filled during the plasticizing of the plastic. This method does not require a pressure sensor in the cylinder.

In this method, preferably the first motor ( 42 ) is driven at a predetermined speed (NS) or a predetermined torque (TS).

Furthermore, in this method, no pressure sensor in the cylinder is used to adjust the pressure in the cylinder.

It is understood that the invention is also applicable when using other motors as torque motors.

The invention may be briefly summarized as follows:
An injection molding apparatus comprises: a plastic supply device, a cylinder for receiving a plastic supplied through the plastic supply device, a screw for conveying the plastic within the cylinder to an exit port of the cylinder, a first motor, preferably an electric servomotor, for rotating the A worm, a second motor, preferably electric servomotor, for rotating a nut member, which is in operative engagement with a shaft carrying the worm, so that, when the nut member and the worm shaft do not rotate at unequal speed, an axial movement of the worm is caused in which a control device is provided for regulating the torque of the second motor, wherein the torque of the second motor is regulated to a value corresponding to the pressure for applying a predetermined pressure to an in-cylinder plastic.

LIST OF REFERENCE NUMBERS

10

An injection unit

12

plasticizing

14

driving section

16

hopper

18

front cylinder part

18a

axial bore

18b

face

18c

Threaded blind hole

18d

outlet channel

20

rear cylinder part

20a

fill opening

22

jet

22a

threaded pin

22b

nozzle channel

22b

rejuvenation

24

filler pipe

26

Heating and cooling equipment

28

Auger

28a

face

30

compression chamber

32

bearing block

34

bearing block

36

connection sleeve

38

drive spindle

38a

tang

38b

external thread

38c

axial bore

40

anchor screw

41

connecting sleeve

42

spindle motor

44

bearing block

46

spline bush

48

coupling part

50

spindle nut

52

mother engine

54

coupling part

56

bearing block

58

thrust

60

transducer

60a

pipe

60b

magnetic ring

60c

disc

62

cover

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• AT 004744 U1 [0002]
• EP 1344623 A1 [0002]
• US 4851171 [0002]
• DE 10135539 A1 [0004]
• JP 61-016826A [0005]
• DE 102004045493 A1 [0006]
• EP 1321837 A2 [0007]
• US 4755123 A [0008]
• DE 202004010812 U1 [0009]
• AT 002813 U1 [0010]

Claims (12)

Injection molding device with a plastic supply device ( 16 ), a cylinder ( 18 . 20 ) for receiving a supplied via the plastic supply means plastic, a screw ( 28 ) for conveying the plastic inside the cylinder ( 18 . 20 ) to an outlet opening of the cylinder, a first motor ( 42 ), preferably electric servomotor, for rotating the screw ( 28 ), a second engine ( 52 ), preferably electric servomotor, for rotating a parent component ( 50 ), that with a the snail ( 28 ) carrying spindle ( 38 ) is in operative engagement, that when the parent component ( 50 ) and the spindle ( 38 ) at different speeds, an axial movement of the screw ( 28 ) is caused; characterized by a regulating device for regulating the torque of the second motor ( 52 ), wherein for applying a predetermined pressure to an in-cylinder plastic, the torque of the second motor is controlled to a value corresponding to the pressure. Apparatus according to claim 1, characterized in that the control means converts a predetermined pressure value of the pressure in the cylinder into a torque value of the torque (T1) of the second motor and the torque of the second motor ( 52 ) according to this torque value. Device according to claim 1 or 2, characterized in that at least one, preferably each of the first and second motors ( 42 . 52 ) is a torque motor. Apparatus according to claim 3, characterized in that at least the torque motor has a water cooling. Device according to one of claims 1 to 4, characterized in that each of the motors ( 42 . 52 ) is associated with a servo inverter Apparatus according to claim 5, characterized in that both servo inverters are combined in a common servo inverter unit for both motors. Device according to one of claims 1 to 6, characterized in that a displacement detection device for detecting an axial displacement of the screw is provided. Apparatus according to claim 7, characterized in that the path detecting means comprises an angle difference detecting means for detecting an angular difference between a rotation angle of the first motor and a rotation angle of the second motor. Device according to claim 7 or 8, characterized in that the path detection device comprises a displacement sensor ( 60 ), preferably a magnetorestrictive non-contact transducer, which preferably within the torque motor designed as a first motor ( 42 ) is arranged. Device according to one of claims 7 to 9, characterized in that the displacement transducer has a digital output and this is directly connected to the servo inverter. Device according to one of claims 7 to 9, characterized in that the servo inverters have an analog signal processing section for processing analog signals as controlled variables. Device according to one of claims 1 to 11, characterized in that the injection molding device is designed such that when exceeding a certain torque on the second motor at least the second motor and preferably both motors are stopped.

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