Drive for a mold clamping unit of an injection molding machine as well as mold clamping unit or injection molding machine with such a drive

Abstract

A drive for a mold clamping unit (10) of an injection molding machine (20) for processing plastics and other plasticizable materials comprises an operationally immovable adjustment plate (90) that can be mounted on the injection molding machine (20), a drive motor (80), a spur gear (70), and a screw drive (60) that has a rotating spindle nut (50) and a non-rotating threaded spindle (40) and connects them to one another in a force-fitting manner. The non-rotating threaded spindle (40) can be connected to an operationally movable crosshead (30) of the mold clamping unit (10), the rotating spindle nut (50) is mounted on the operationally immovable adjustment plate (90) and is connected to the spur gear (70), which is connected to the drive motor (80).The screw drive (60) and the spur gear (70) are arranged in a lockable cavity (100) of the adjustment plate (90) and the screw drive (60) and the spur gear (70) have a common oil bath lubrication.

Description

Field of the invention

[0001] The present invention relates to a drive for a mold closing unit of an injection molding machine for processing plastics and other plasticizable materials having the features according to the preamble of claim 1, a mold closing unit for an injection molding machine having the features according to the preamble of claim 10, and an injection molding machine for processing plastics and other plasticizable materials having the features according to the preamble of claim 11. State of the art

[0002] Conventional drives for mold clamping units often feature hollow-shaft motors, which are complex and expensive due to the additional measurement technology required, or a rotating threaded spindle that interacts with a spindle nut attached to a crosshead. The drive is usually connected to a standard motor via a belt. Currently available drives are generally complex, prone to wear, and require a lot of space, thus restricting the freedom of movement of other components of the mold clamping unit. Especially during the start-up phase of the injection molding machine, these solutions can lead to temperature-related changes in the drive train, which can impact the reject rate of the produced components.

[0003] EP 0 164 419 B1 discloses a clamping device for closing molds of an injection molding apparatus, comprising a servomotor and a power transmission mechanism. The clamping device has a threaded bolt and a spindle nut mechanism for converting a rotational force of the servomotor into a linearly acting force. The clamping device further includes a joint mechanism in the form of a toggle lever mechanism, which can be actuated by the power transmission mechanism to close the molds. When joints of the joint mechanism are in an extended state, thereby closing the molds, the servomotor can be operated with a current that is lower than a normal operating current to keep the joints in the extended state.

[0004] DE 199 64 087 B4 discloses a clamping device for an injection molding machine for plastics, comprising a stationary support platen connected to a movable mold clamping plate via a drive. At least two spindles arranged in series are provided, with the first spindle operatively connected to a platen and the second spindle to the drive, with the thread pitches of both spindles running in opposite directions. A sleeve-shaped power transmission part is arranged concentrically to the spindles, and spindle nuts are provided at the head end of each power transmission part, which are operatively connected to both the sleeve-shaped power transmission part and the spindles.The stationary support plate is connected to the movable tool clamping plate via a crank or toggle mechanism, which is driven by a spindle that is translationally moved by a hollow-shaft motor with the interposition of a spindle nut. The hollow-shaft motor is connected to the sleeve-shaped power transmission part in an axially movable manner. At least one shaped element is provided on the motor housing of the hollow-shaft motor, which supports the motor housing and prevents it from twisting.

[0005] JP H 05345339 A discloses a mold clamping device comprising: (a) a screw fixed to a movable platen and consisting of a screw conveyor having, for example, a square or trapezoidal thread; (b) a nut member engaged with a rotary motor and with the screw; (c) a lubricating device for supplying oil to the contact surfaces of the threads of the screw and the nut member; (d) a mold clamping member supported in its axial direction by a movable back platen and movable by a predetermined amount to rotatably support the nut member; (e) a mold clamping hydraulic fluid chamber for moving the mold clamping member in the mold closing direction during the mold closing operation; and (f) a mold releasing hydraulic fluid chamber (A) for moving the mold clamping member in the mold opening direction during the mold opening operation.This enables miniaturization of the device, increase of the stationary load capacity, precise execution of the mold opening process and reduction of noise.

[0006] KR 100360912 B1 shows a clamping device of an injection molding machine, which serves to actuate a locking rod in a clamp housing forward and backward by the forward and reverse drive of a servo motor. It comprises an upper and a lower transparent plug made of a glass material through which the interior of the clamping device can be viewed. It is mounted at a position below a central portion of the outer peripheral surface of the clamp housing and at a position below the central portion to check whether a correct amount is injected into the clamp housing. An oil reservoir is provided for storing and supplying oil injected into the clamp housing, so that the spindle nut can be moved back and forth along the roller screw on the upper part of the clamp housing.

[0007] DE 10 2010 048 560 A1 discloses a mold clamping unit of an injection molding machine for processing plastics, comprising at least one injection mold that can be accommodated between a stationary mold carrier and a movable mold carrier. The mold carriers are moved by means of at least one toggle lever pairing with two toggle lever mechanisms, each driven independently of one another by a drive unit in a closing direction. The toggle lever mechanisms are mounted on a bearing plate. The bearing plate is movably mounted on the injection molding machine along guides, and the drive units are mounted on the movable bearing plate, on which the actuating elements for the at least two toggle lever mechanisms are mounted.

[0008] DE 10 2004 053 855 A1 discloses a method for manufacturing an injection molding machine with at least one direct drive, as well as an injection molding machine manufactured using this method. The direct drive comprises a stator and a rotor rotatably mounted or accommodated therein. A component of the injection molding machine is provided with a statorless housing, the interior of which is dimensioned such that the stator can be accommodated therein, and a housingless stator is subsequently fitted into the housing.

[0009] JP 2016-088034 A discloses a toggle-type mold clamping device for producing molded parts. The device comprises a cylindrical holding element whose front end is fixed to the rear side of an end plate, while a ball screw mechanism is housed inside. A hollow component is rotated by an electric motor via a rotation transmission unit. A nut member is rotated by a rotary drive of the hollow component. A screw shaft is driven in the mold closing direction by the rotary drive of the nut member. The mold closing movement drives the crosshead attached to the front end of the screw shaft.

[0010] AT 12 643 U1 discloses a spindle drive for an injection molding machine, comprising a rotationally fixed spindle and a rotationally driven spindle nut, which are movable relative to each other. A two-part drip tray is arranged below the spindle, comprising a stationary part and a movable part arranged above the stationary part and movable together with the spindle nut or the spindle. The stationary part has at least one lubricating oil drain opening. Description of the invention

[0011] The invention is based on the object of specifying a drive for a mold closing unit of an injection molding machine, which can be manufactured with little effort and is low-wear and has a space-saving design, wherein the reject rate of the produced components is preferably minimized at all times, in particular during a start-up phase of the injection molding machine.

[0012] This object is achieved with a drive according to the features of claim 1. The drive comprises an operationally immovable adjustment plate, which can be mounted on a machine stand of the injection molding machine, a drive motor, a spur gear, and a screw drive, which has a rotating spindle nut and a non-rotating threaded spindle and connects them to one another in a force-locking manner. The non-rotating threaded spindle can be connected to an operationally movable crosshead of the mold clamping unit; the rotating spindle nut is mounted on the operationally immovable adjustment plate and is connected to the spur gear, which is connected to the drive motor. The screw drive and the spur gear are arranged in a lockable cavity of the adjustment plate, and the screw drive and the spur gear share an oil bath lubrication system.The drive, and in particular the spur gear, offers the advantage that, unlike a belt used in the prior art, there are no wearing parts in the drive train, and the virtually backlash-free gear solution enables more precise control of the drive movement. By using a shared oil bath lubrication system for the screw drive and the spur gear, wear can be significantly reduced and maintenance requirements reduced. Furthermore, the oil bath provides thermal advantages through a larger radiating surface and better temperature distribution.

[0013] The object is also achieved with a mold clamping unit for an injection molding machine with a drive according to one of claims 1 to 9 according to the features of claim 10. The mold clamping unit comprises a drive according to the invention, which is connected by means of a crosshead to a first end of a joint mechanism, with a second end of the joint mechanism being connected to a movable mold carrier. The drive, the crosshead, the joint mechanism, the movable mold carrier, and the immovable mold carrier form a mold opening and closing mechanism.

[0014] Furthermore, the object is also achieved with an injection molding machine for processing plastics and other plasticizable materials according to the features of claim 11. It comprises a drive according to one of claims 1 to 9 for a mold clamping unit according to claim 10.

[0015] Advantageous further training is the subject of dependent claims.

[0016] In a preferred embodiment of the drive, which advantageously improves the design of the drive and simplifies the design of the drive motor, the spur gear is arranged on a side of the rotating spindle nut facing the mold clamping unit. This connects the rotating spindle nut and the drive motor in parallel, which advantageously results in a significantly shorter design.

[0017] Preferably, a further embodiment of the drive advantageously simplifies its design by arranging the spur gear on a side of the rotating spindle nut facing away from the mold clamping unit. This eliminates the need for an intermediate gear in the spur gear, making the drive smaller and also enabling the production of a gear ratio in a space-saving area. This results in a larger gear ratio, which equates to a lower torque on the motor input side, allowing the use of a smaller motor and converter, thus contributing to cost savings. Furthermore, integration into the adjustment plate is significantly simplified.

[0018] Because the screw drive and the spur gear are enclosed in a common housing that can be inserted into the lockable cavity of the adjustment plate, another embodiment of the drive advantageously facilitates the integration of the screw drive and the spur gear, which are pre-assembled in a housing, into the adjustment plate, which also improves their pre-testability. A further advantage of this embodiment is that the pre-assembled unit has direct contact with the adjustment plate at only a very few connection points, and that the optimal selection of connection points prevents deformation of the adjustment plate under the influence of the clamping force of the mold clamping unit from affecting the remaining parts of the drive.

[0019] A preferred embodiment of the drive improves its design by connecting the drive motor to the spur gear either on the side of the rotating spindle nut facing the mold clamping unit or on the side of the rotating spindle nut facing away from the mold clamping unit. This advantageously allows for an optimally sized installation space within the mold clamping unit or the injection molding machine, depending on the type of drive or the design of the injection molding machine, and the design of the other components of the mold clamping unit.

[0020] In a further embodiment of the drive that simplifies the design of the drive motor, the spur gear preferably has at least one intermediate gear. The use of an intermediate gear advantageously enables a higher spur gear ratio, which allows for a simpler design of the drive motor.

[0021] Preferably, the spur gear is configured such that it has a free space, preferably a free space in the center of the spur gear, through which the threaded spindle passes or can pass. The use of the spur gear advantageously creates the possibility of laterally displacing the drive motor and simultaneously creating space in the gear, preferably in the center of the gear, so that the threaded spindle can pass through the gear in the axial direction. Preferably, the drive motor can be arranged parallel to the passing threaded spindle, so that by utilizing the free space in the center of the gear for the threaded spindle, the overall length of the mold clamping unit can be advantageously significantly reduced.

[0022] In another preferred embodiment of the drive, the reject rate of the produced components is advantageously reduced, especially during the start-up phase of the injection molding machine, by the fact that the shared oil bath lubrication system is temperature-controlled. This allows the injection molding machine to reach process equilibrium more quickly.

[0023] Preferably, another embodiment of the drive advantageously improves its condition monitoring by having the shared oil bath lubrication system with sensors for monitoring temperature, oil cleanliness, and / or oil aging. This allows maintenance to be initiated in a timely manner if it is detected that the condition of the oil bath lubrication could increase wear within the drive.

[0024] The features listed individually in the patent claims can be combined with one another in a technologically meaningful manner and can be supplemented by explanatory facts from the description and by details from the figures, whereby further embodiments of the invention are shown.

[0025] The invention will now be explained in more detail using an exemplary embodiment. Shown are: Fig. 1 an overall view of an injection molding machine, Fig. 2 an isometric view of the mold clamping unit of the injection molding machine according to Fig. 1, Fig. 3 a sectional view of the drive with a spur gear with intermediate gear on the body of the spindle nut, wherein the spur gear is arranged on a side of the rotating spindle nut facing the mold closing unit and with a view in the direction of arrow A, Fig. 4 a sectional view through Fig. 3 transverse to the machine's longitudinal axis showing the space for oil bath lubrication and a spur gear solution with intermediate gear, Fig. 5 a sectional view of the drive with a spur gear in a second embodiment without an intermediate gear, wherein the spur gear is arranged on a side of the rotating spindle nut facing away from the mold closing unit, as well as with a view in the direction of arrow B, Fig. 5A is a sectional view of the drive with a spur gear in a third embodiment without an intermediate gear, wherein the spur gear and the drive motor are arranged on a side of the rotating spindle nut facing the mold closing unit, as well as a view in the direction of arrow B, Fig. 6 a sectional view of the drive in a fourth embodiment, wherein the screw drive and the spur gear are arranged in a separate housing, as well as with a view in the direction of arrow C. Description of preferred embodiments

[0026] Before describing the invention in detail, it should be noted that it is not limited to the specific components of the device and the specific method steps, as these components and methods may vary. The terms used herein are intended solely to describe particular embodiments and are not intended to be limiting. Furthermore, when the singular or indefinite articles are used in the description or claims, this also refers to the plural of these elements, unless the overall context clearly indicates otherwise.

[0027] The Fig. 1 shows an injection molding machine 20 for processing plastics and other plasticizable materials with a machine stand 150, an injection molding unit 160 mounted on the machine stand 150 and a mold clamping unit 10 also mounted thereon.

[0028] The structure and operation of an injection molding machine are generally known to those skilled in the art. Plastics or other plasticizable materials are fed to the injection molding machine 20, which are mixed, plasticized, and homogenized in a plasticizing cylinder of the injection molding unit 20. During the plasticizing process, plasticized material is metered in front of a conveyor. Subsequently, an axial movement of the conveyor injects the plasticized material into a mold cavity of an injection mold (not shown in the drawing), which, in operation, is held between a movable mold carrier 130 and a stationary mold carrier 140. During the injection process, the injection mold is closed by the mold clamping unit 10. As soon as the injected plasticized material has hardened in the mold cavity, the injection mold is reopened by the mold clamping unit 10 so that the finished molded part can be removed.This process occurs cyclically.

[0029] The Fig. 2 shows a section of the Fig. 1 with a part of the machine stand 150 and the mold clamping unit 10 mounted thereon with its drive. In addition to the Fig. 2 is in the Fig. 3 shows the drive for the mold clamping unit 10 of the injection molding machine 20 in detail. This comprises an operationally immovable adjustment plate 90, which is mounted on the machine stand 150 of the injection molding machine 20, a drive motor 80, a spur gear 70, and a screw drive 60, which has a rotating spindle nut 50 and a non-rotating threaded spindle 40 and connects them non-positively. The non-rotating threaded spindle 40 is connected to an operationally movable crosshead 30 of the mold- clamping unit 10. The rotating spindle nut 50 is mounted on the operatively immobile adjustment plate 90 and is connected to the spur gear 70, which in turn is connected to the drive motor 80. Operationally movable or immobile refers to the production operation of the injection molding machine 20.

[0030] The adjustment plate 90 or parts mounted thereon can also be height-adjustable relative to the machine stand 150 during setup of the injection molding machine 20 for fine adjustment of the mold clamping unit 10, for example. The screw drive 60 and the spur gear 70 are arranged in a lockable cavity 100 of the adjustment plate 90, and the screw drive 60 and the spur gear 70 share a common oil bath lubrication. In addition to the advantage of virtually backlash-free and positionally precise control of the drive, this also reduces wear and maintenance frequency.

[0031] Advantageously, the spur gear 70 can be arranged on a side of the rotating spindle nut 50 facing the mold closing unit 10, as shown in the Fig. 3 and Fig. 4. This allows the rotating spindle nut and the drive motor to be connected in parallel, resulting in a significantly shorter design. Another design advantage is that the use of an intermediate gear allows for a higher gear ratio in the transmission, which reduces the motor's footprint.

[0032] However, the spur gear 70 can also be arranged on a side of the rotating spindle nut 50 facing away from the mold clamping unit 10, as in Fig. 5. The gear ratio or the gears, i.e. only the pinion and output gear without an intermediate gear 75, are selected such that a distance is maintained between the drive motor 80 and the threaded spindle 40, which extends through to the rear. However, the use of an additional intermediate gear is fundamentally possible. By connecting the pinion to the output gear, the gear ratio can be realized in smaller ranges, which nevertheless results in a downsizing of the drive train. Furthermore, the integration of the gear technology into the adjustment plate 90 is significantly simplified; the unit is essentially mounted on the rear, and the adjustment plate 90 only needs to be minimally hollowed out, thus weakening its stability only slightly.

[0033] The use of the spur gear 70 also makes it possible to offset the drive motor laterally and simultaneously create space within the gear, preferably in the center of the gear, so that the threaded spindle 40 can penetrate the gear in the axial direction (see the dashed representation of the threaded spindle in the figures). Furthermore, the drive motor 80 can be arranged parallel to the threaded spindle 40, so that by utilizing the free space in the center of the gear for the threaded spindle, the overall length of the mold clamping unit can be significantly reduced.

[0034] In a further advantageous embodiment of the drive according to Fig. 6, the screw drive 60 and the spur gear 70 are enclosed by a common housing 110, which can be inserted into the lockable cavity 100 of the adjustment plate 90. The entire drive can thus be inserted as a module into the adjustment plate 90, which offers significant advantages in terms of the testability and maintainability of the drive. Testing and maintenance of the drive can thus be carried out outside and independently of the mold clamping unit 10 or injection molding machine 20. Replacing the drive is also made easier, e.g., in the event of a drive malfunction or if the performance of the drive needs to be adjusted. Operational disruptive forces that arise within the adjustment plate 90 and deform it are also isolated and are not transmitted to the drive, or are only transmitted to a minimal extent. This reduces wear on the drive.

[0035] In principle, an oil bath lubrication can be located either in the lockable cavity 100 or in the housing 110, which can be inserted into the lockable cavity 100 of the adjustment plate 90.

[0036] It has also proven particularly advantageous that the drive motor 80 with the spur gear 70 is mounted either on the side of the rotating spindle nut 50 facing the mold clamping unit 10 (see Fig. 5A) or the side of the rotating spindle nut 50 facing away from the mold clamping unit 10 (see Fig. 5 and Fig. 6). Depending on the type of drive or design of the injection molding machine 20 and the design of the other components of the mold clamping unit 10, a large space can be provided within the mold clamping unit 10 or the injection molding machine 20 to enable improved accessibility to the individual elements of the mold clamping unit 10.

[0037] The spur gear 70 may have at least one intermediate gear 75 (see e.g. Fig. 3). This allows for a higher spur gear ratio, which allows for a simpler design of the drive motor 80 and higher gear ratios.

[0038] Wear on the screw drive 60 can be significantly reduced by implementing it as a ball screw, roller screw, or planetary roller screw, which offer significantly improved properties compared to a trapezoidal screw. The ball screw or roller screw allows for high drive precision, whereas the planetary roller screw, particularly due to its very large number of contact points, enables significantly higher load ratings than ball screws. Furthermore, they are axially stiffer because the crown radii of the roller flanks are considerably larger than the ball radius of a comparable ball screw.

[0039] It is of great advantage if the shared oil bath lubrication of the screw drive 60 and the spur gear 70 is temperature-controlled. By using a temperature-controlled, oil-bath-lubricated spur gear 70, a thermal equilibrium can be established via an oil bath temperature control unit 170, which allows heating during a start-up phase and cooling during continuous operation, allowing the injection molding machine 20 to reach process equilibrium more quickly and thus minimize the reject rate, especially during run-up operation.

[0040] It is also advantageous if the shared oil bath lubrication system is equipped with sensors S for monitoring temperature, oil cleanliness, and / or oil aging. This avoids unnecessary maintenance, and any abnormalities in the oil bath lubrication that could increase wear are quickly and reliably detected, enabling wear-based maintenance.

[0041] An injection molding machine 20 with a mold clamping unit 10 can thus advantageously be equipped with a drive according to the invention. The mold clamping unit 10 comprises the drive, which is connected by means of the crosshead 30 to a first end of a joint mechanism 120, with a second end of the joint mechanism 120 being connected to a movable mold carrier 130. The drive, the crosshead 30, the joint mechanism 120, the movable mold carrier 130, and a stationary mold carrier 140 form a mold opening and closing mechanism.

[0042] Furthermore, the above-described injection molding machine 20 with a mold clamping unit 10 driven by a drive according to the invention can be operated by a method by which the injection molding machine 20 is maintained at all times, particularly during a start-up phase of the injection molding machine 20, in a process state in which a reject rate of produced components, which depends on the temperature of the oil bath lubrication, is minimized. The injection molding machine 20 has a controller configured to regulate the temperature of the oil bath lubrication. List of reference symbols 10 mold clamping unit, 20 injection molding machines, 30 crosshead, 40 threaded spindle, 50 spindle nut, 60 screw drive, 70 spur gears, 75 intermediate gear, 80 drive motor, 90 adjustment plate, 100 cavity, 110 housings, 120 joint mechanism, 130 movable mold carrier, 140 non-movable mold carrier, 150 machine stands, 160 injection molding unit, 170 Oil bath temperature control unit S sensors.

Claims

[1] Drive for a mold clamping unit (10) of an injection molding machine (20) for processing plastics and other plasticizable materials, comprising an operationally immovable adjustment plate (90) which can be mounted on a machine stand (150) of the injection molding machine (20), a drive motor (80), a spur gear (70), a screw drive (60) which has a rotating spindle nut (50) and a non-rotating threaded spindle (40) and connects them to one another in a force-locking manner, wherein the non-rotating threaded spindle (40) can be connected to an operationally movable crosshead (30) of the mold clamping unit (10), the rotating spindle nut (50) is mounted on the operationally immovable adjustment plate (90) and is connected to the spur gear (70) which is connected to the drive motor (80), characterized by , that the screw drive (60) and the spur gear (70) are arranged in a lockable cavity (100) of the adjusting plate (90) and that the screw drive (60) and the spur gear (70) have a common oil bath lubrication. [2] Drive according to claim 1, characterized by that the spur gear (70) is arranged on a side of the rotating spindle nut (50) facing the mold closing unit (10). [3] Drive according to claim 1, characterized by that the spur gear (70) is arranged on a side of the rotating spindle nut (50) facing away from the mold closing unit (10). [4] Drive according to one of the preceding claims, characterized by that the screw drive (60) and the spur gear (70) are surrounded by a common housing (110) which can be inserted into the lockable cavity (100) of the adjusting plate (90). [5] Drive according to one of the preceding claims, characterized bythat the drive motor (80) is connected to the spur gear (70) either on the side of the rotating spindle nut (50) facing the mold closing unit (10) or on the side of the rotating spindle nut (50) facing away from the mold closing unit (10). [6] Drive according to one of the preceding claims, characterized by that the spur gear (70) has at least one intermediate gear (75). [7] Drive according to one of the preceding claims, characterized by that the spur gear (70) is designed such that it has a free space, preferably a free space in the center of the spur gear (70), through which the threaded spindle (40) passes or can pass. [8] Drive according to one of the preceding claims, characterized by that the common oil bath lubrication can be tempered by an oil bath tempering unit (170). [9] Drive according to one of the preceding claims, characterized bythat the common oil bath lubrication system has sensors (S) for monitoring the temperature, oil cleanliness and / or oil ageing. [10] A mold closing unit (10) for an injection molding machine (20) comprising a drive, an operatively movable crosshead (30), a joint mechanism (120), a movable mold carrier (130) and a non-movable mold carrier (140), wherein the drive is connected by means of the crosshead (30) to a first end of the joint mechanism (120) and a second end of the joint mechanism (120) is connected to the movable mold carrier (130), and wherein the drive, the crosshead (30), the joint mechanism (120), the movable mold carrier (130) and the non-movable mold carrier (140) form a mold opening and closing mechanism, characterized by that the drive of the mold closing unit (10) is designed according to one of the preceding claims. [11] Injection moulding machine (20) for processing plastics and other plasticisable materials, characterized by that it has a drive designed according to one of claims 1 to 9 for a mold closing unit (10) according to claim 10.

Images