Vertical mold clamping device and vertical injection molding machine

Abstract

To provide a vertical mold clamping device with which jamming of foreign matter can be precisely detected to protect a metal mold.SOLUTION: A vertical mold clamping device (2) includes: a stationary platen (9); an upper movable platen (10) above the stationary platen; a lower movable platen (11) below the stationary platen; and a plurality of rod-shaped members (12) connecting the upper movable platen (10) and the lower movable platen (11). The present disclosure employs, as the rod-shaped members (12), a ball spline (12) made up of a spline shaft (22) and a ball retainer (23) that accommodates a ball and slides the spline shaft (22). The upper movable platen (10) and the lower movable platen (11) are connected by the spline shaft (22), and the ball retainer (23) is disposed with respect to the stationary platen (9).SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a vertical mold clamping device that opens and closes the mold vertically, and a vertical injection molding machine.

Background Art

[0002] A vertical injection molding machine includes a vertical mold clamping device that opens and closes the mold in the vertical direction and an injection device. As described in Patent Document 1, the vertical mold clamping device includes a fixed platen fixed to a frame, an upper movable platen provided above the fixed platen, and a lower movable platen provided below. The upper movable platen and the lower movable platen are connected by a plurality of tie bars, and a mold clamping mechanism, for example, a toggle mechanism, is provided between the lower movable platen and the fixed platen.

[0003] An upper mold is provided on the upper movable platen, and a lower mold is provided on the fixed platen. However, in many models of the vertical mold clamping device, a rotatable turntable is provided on the fixed platen. When a turntable is provided, a plurality of lower molds are provided on the turntable. That is, the turntable is rotated to align one of the lower molds with the upper mold for mold clamping.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] During the molding cycle, foreign matter may become trapped between the upper and lower molds. For example, some resin may remain in the parting line. Or, in the case of insert molding, the insert may protrude from the recess where it should be inserted. If the mold is clamped without noticing this foreign matter trapping, the mold will be damaged. Therefore, the driving force required for mold closing and clamping is monitored and detected. For example, if the clamping mechanism is a toggle mechanism, the crosshead is driven by a ball screw mechanism and a mold opening / closing motor. The normal change pattern of the mold opening / closing motor's torque during mold closing and clamping is obtained in advance. During the molding cycle, the change in the mold opening / closing motor's torque is monitored, and if it deviates from the normal change pattern during mold closing and clamping, it is determined that foreign matter trapping has occurred.

[0006] However, even if the torque of the mold opening / closing motor is monitored, it is not always possible to detect foreign objects getting caught in the mold with high accuracy. This is because there is sliding resistance in each component of the vertical mold clamping device, which affects the accuracy of torque monitoring. In other words, there are challenges in protecting the mold.

[0007] This disclosure provides a vertical mold clamping device and a vertical injection molding machine that can accurately detect foreign matter entrapment and protect the mold.

[0008] Other challenges and novel features will become apparent from the description and accompanying drawings in this specification. [Means for solving the problem]

[0009] The vertical clamping device comprises a fixed platen, an upper movable platen and a lower movable platen provided above and below it, a plurality of rod-shaped members connecting the upper movable platen and the lower movable platen, and a clamping mechanism provided between the fixed platen and the lower movable platen. This disclosure provides a spline shaft as the rod-shaped member, inside The ball is stored By the rolling motion of the ballA ball spline is employed, consisting of a spline shaft and a ball retainer that slides along it. The upper and lower movable plates are connected by the spline shaft, and the ball retainer is mounted relative to the fixed platen. [Effects of the Invention]

[0010] This disclosure enables accurate detection of foreign objects trapped in molds, thereby protecting them. [Brief explanation of the drawing]

[0011] [Figure 1] This is a front view of a vertical injection molding machine according to the first embodiment. [Figure 2] This is a front view of a vertical injection molding machine according to a second embodiment. [Figure 3] This is a top view of a vertical clamping device according to the first embodiment. [Figure 4] This is a top view of a vertical clamping device according to a second embodiment. [Figure 5] This is a front view of a vertical injection molding machine relating to a comparative example. [Modes for carrying out the invention]

[0012] The following describes specific embodiments in detail with reference to the drawings. However, the embodiments are not limited to those described below. For clarity, the following descriptions and drawings have been simplified as appropriate. In each drawing, the same elements are denoted by the same reference numerals, and redundant explanations have been omitted where necessary. Also, hatching has been omitted in some parts of the drawings to avoid clutter.

[0013] [First Embodiment] <Vertical injection molding machine> The vertical injection molding machine 1 according to the first embodiment, as shown in Figure 1, comprises a vertical clamping device 2, an injection device 3 provided on the upper part of the vertical clamping device 2, and a control device 4 for controlling these.

[0014] <Vertical mold clamping device> The vertical mold clamping device 2 comprises a fixed platen 9 fixed to the bed 7, an upper movable platen 10 located above the fixed platen 9, and a lower movable platen 11 located within the bed 7. In the first embodiment, the upper movable platen 10 and the lower movable platen 11 are connected by three rod-shaped members 12, 12, ... The rod-shaped members 12, 12, ... will be described later. In the vertical mold clamping device 2, a toggle mechanism 14 is provided as a mold clamping mechanism between the lower movable platen 11 and the fixed platen 9. A turntable 15 is provided on top of the fixed platen 9. As shown in Figure 3, the turntable 15 rotates around a single central rod-shaped member 12. The turntable 15 is driven by a drive mechanism consisting of a turntable servo motor 25, a drive pulley 26, and a timing belt 27.

[0015] As shown in Figure 1, the toggle mechanism 14 is driven by a ball screw mechanism 17 and a type switching motor 18 that drives the ball screw mechanism 17. The control device 4 controls the type switching motor 18 and monitors its torque.

[0016] The upper movable platen 10 is equipped with one upper mold 19, and the turntable 15 is equipped with multiple lower molds 20, 20, in this embodiment. However, in Figure 1, the two lower molds 120, 20 are arranged in an overlapping position for drawing purposes, so only one is shown. In the top view of Figure 3, two lower molds 20, 20 are shown.

[0017] <Rod-shaped member> In the first embodiment, ball splines 12, 12,... are adopted for the rod-shaped members 12, 12,.... As shown in FIG. 1, the ball splines 12, 12,... are composed of spline shafts 22, 22,... and ball retainers 23, 23,... that slide on these spline shafts 22, 22,.... Although not shown in the figure, a large number of balls are held inside the ball retainers 23, 23,.... Due to the rolling of these balls, the ball retainers 23, 23,... slide smoothly on the spline shafts 22, 22,.... The ball retainers 23, 23,... are provided on the fixed plate 9, and the upper movable plate 10 and the lower movable plate 11 are connected by the spline shafts 22, 22,.... Therefore, the upper movable plate 10 and the lower movable plate 11 slide with almost no sliding resistance against the fixed plate 9.

[0018] <Injection device> The injection device 3 is provided on the upper movable plate 10 of the vertical mold clamping device 2. The injection device 3 includes a heating cylinder 31, a screw 32 provided in the heating cylinder 31, a screw drive mechanism 33 for driving the screw 32, and a lifting device 35 for lifting and lowering the entire injection device 3. The injection device 3 rotates the screw 32 to melt the injection material and drives the screw 32 in the axial direction to inject the injection material.

[0019] <Mold protection> The vertical injection molding machine 1 according to the first embodiment detects whether there is any foreign matter sandwiched between the molds 19 and 20 when the mold is closed and clamped. Specifically, it is as follows. The molds 19 and 20 are pre-closed and clamped in a normal state, and the torque of the mold opening / closing motor 18 at that time is detected and recorded in the control device 4. That is, the change pattern of the torque at the time of mold closing and clamping in the normal state, that is, the normal change pattern, is recorded in the control device 4. Thereafter, when implementing the molding cycle, the control device 4 monitors the torque of the mold opening / closing motor 18 at the time of mold closing and clamping and compares it with the normal change pattern. If the torque of the mold opening / closing motor 18 deviates from the normal change pattern, for example, if it becomes larger than a predetermined value or larger than a predetermined ratio, it is determined that foreign matter has been sandwiched, and the mold opening / closing motor 18 is stopped. This protects the molds 19 and 20.

[0020] By the way, when the mold opening / closing motor 18 opens and closes the vertical mold clamping device 2, the sliding resistance between the rod-shaped members 12, 12,... and the fixed platen 9 affects the torque of the mold opening / closing motor 18. That is, the mold opening / closing motor 18 needs to open and close against the sliding resistance, and thus the torque of the mold opening / closing motor 18 needs to be increased accordingly. The greater the sliding resistance, the greater the influence on the torque, which affects the accuracy of detecting whether there is any foreign matter sandwiched between the molds 19 and 20. The vertical injection molding machine 1 according to the first embodiment has the rod-shaped members 12, 12,... composed of ball splines 12, 12,.... Therefore, the sliding resistance between the rod-shaped members 12, 12,... and the fixed platen 9 is very small. That is, the influence of the sliding resistance on the torque of the mold opening / closing motor 18 can be almost ignored. Therefore, it is possible to accurately detect whether there is any foreign matter sandwiched between the molds 19 and 20.

[0021] [Second Embodiment] <Vertical Injection Molding Machine> The vertical injection molding machine 1A according to the second embodiment, as shown in Figure 2, comprises a vertical clamping device 2A, an injection device 3 provided on the upper part of the vertical clamping device 2A, and a control device 4 for controlling them. The injection device 3 is configured in the same way as the vertical injection molding machine 1 according to the first embodiment (see Figure 1), so the same reference numerals are used for the same components and their descriptions are omitted.

[0022] <Vertical mold clamping device> The vertical clamping device 2A according to the second embodiment shown in Figure 2 is configured similarly to the vertical clamping device 2 according to the first embodiment, except for some components. Therefore, the same components are given the same reference numerals and their descriptions are omitted, and only the differences are described.

[0023] The vertical mold clamping device 2A according to the second embodiment differs primarily in its mold clamping mechanism. The mold clamping mechanism of the vertical mold clamping device 2A according to the second embodiment consists of a ball screw mechanism 40, a mold opening / closing motor 18A, and a rotation transmission mechanism 44. The ball nut 42 of the ball screw mechanism 40 is provided on the lower movable platen 11, and the ball screw 41 is rotatably provided between the fixed platen 9 and the ball nut 42. The mold opening / closing motor 18A rotates the ball screw 41 via the rotation transmission mechanism 44. Therefore, when the mold opening / closing motor 18A is driven, the vertical mold clamping device 2A opens and closes the mold. The ball nut 42 is provided on the lower movable platen 11 via a load cell 43, so the mold clamping force is detected by the load cell 43.

[0024] The vertical clamping device 2A according to the second embodiment differs from the first embodiment in the shape of the upper movable platen 10A and the number of rod-shaped members 12, 12, ..., i.e., the number of ball splines 12, 12, ..., as shown in Figure 4. The upper movable platen 10A is roughly rectangular, and four ball splines 12, 12, ... are arranged at each vertex of the rectangle. In the first embodiment, the ball splines 12, 12, ... are arranged in this way, so the turntable 15A also differs slightly from that of the first embodiment. In the vertical clamping device 2A according to the second embodiment, the turntable 15A rotates around the rotation axis 46, as shown in Figure 4, and there are no ball splines 12 at the center of rotation.

[0025] In the first embodiment, the vertical mold clamping device 2 (see Figure 3) had three ball splines 12, 12, ... whereas in the second embodiment, there are four ball splines 12, 12, ... as shown here. In other words, the sliding resistance is increased by the equivalent of one spline. However, since the sliding resistance of the fixed platen 9 during mold opening and closing is minimal, the sliding resistance can be ignored even with four splines. In other words, it does not affect the accuracy of detecting foreign matter trapped in the molds 19 and 20.

[0026] The clamping mechanism employed in the vertical clamping device 2A according to the second embodiment can detect the pinching of foreign objects in the molds 19 and 20 with greater accuracy than the toggle mechanism 14 (see Figure 1) in the first embodiment. This will be explained below.

[0027] The toggle mechanism 14 employed in the vertical mold clamping device 2 according to the first embodiment has a different expansion ratio depending on its bending and extending state, with the expansion ratio being larger when the mold is closed or clamped. As a result, even if foreign matter is caught between the molds 19 and 20, the large expansion ratio during mold closing or clamping means that the change in torque in the mold opening / closing motor 18 is small. Therefore, in order to detect foreign matter being caught, it is necessary to detect small changes in torque. In other words, the detection accuracy is not high.

[0028] In contrast, the clamping mechanism employed in the vertical clamping device 2A of the second embodiment (see Figure 2), which consists of a ball screw mechanism 40, a mold opening / closing motor 18A, and a rotation transmission mechanism 44, has a constant magnification ratio. Therefore, when foreign matter is trapped between the molds 19 and 20 during mold closing or clamping, the torque change in the mold opening / closing motor 18A becomes relatively large. In other words, in the second embodiment, it is easy to detect changes in torque and it is possible to detect foreign matter trapped between the molds 19 and 20 with high accuracy.

[0029] [Comparative Example] Figure 5 illustrates the comparative example of the vertical injection molding machine 51. In the comparative example of the vertical injection molding machine 51, devices or components configured in the same way as those in the vertical injection molding machine 1 according to the first embodiment (see Figure 1) are given the same reference numerals and their descriptions are omitted.

[0030] The difference between the comparative example's vertical injection molding machine 51 and the vertical injection molding machine 1 according to the first embodiment is the rod-shaped members 55, 55, ... that connect the upper movable platen 10 and the lower movable platen 11 in the vertical clamping device 52. In the comparative example's vertical clamping device 52, three tie bars 55, 55, ... connect the upper movable platen 10 and the lower movable platen 11. The tie bars 55, 55, ... pass through the fixed platen 9, and the fixed platen 9 is provided with bushes 57, 57, ... that allow the tie bars 55, 55, ... to slide.

[0031] In the comparative example vertical injection molding machine 51, sliding resistance occurs between the tie bars 55, 55, ... and the bushes 57, 57, ... when the mold is opened and closed. In other words, sliding resistance occurs between the tie bars 55, 55, ... and the fixed platen 9. This sliding resistance is larger than that of the ball splines 12, 12, ... in the first embodiment (see Figure 1). Therefore, in the comparative example vertical injection molding machine 51 (see Figure 5), when monitoring the torque of the mold opening / closing motor 18 to detect whether or not foreign matter is trapped in the molds 19, 20, this relatively large sliding resistance reduces the detection accuracy.

[0032] [experiment] An experiment was conducted to compare the accuracy of detecting foreign matter trapped in molds 19 and 20 using a vertical injection molding machine 1A according to the second embodiment (see Figure 2) and a vertical injection molding machine 51 according to a comparative example (see Figure 5).

[0033] <Experiment details> In both the vertical injection molding machine 1A according to the second embodiment and the vertical injection molding machine 51 according to the comparative example, a paper cup with a height of 74.0 mm was placed on the turntable 15 instead of the lower mold 20. The vertical mold clamping devices 2A (see Figure 2) and 52 (see Figure 5) were adjusted so that the position where the upper mold 19 touches the paper cup was the mold closing position. In addition, the rotation speed of the mold opening / closing motor 18 was set to 10% of the normal speed near the mold closing position. In other words, the mold protection speed was set to 10%. Under these conditions, the mold closing was performed while monitoring the torque of the mold opening / closing motor 18, and the indentation of the paper cup when foreign matter was detected was observed. In the vertical injection molding machine 1A according to the second embodiment, a foreign object was detected when the height of the paper cup reached 72.8 mm (a reduction of 1.2 mm), and in the vertical injection molding machine 51 according to the comparative example, a foreign object was detected when the height of the paper cup reached 72.0 mm (a reduction of 2.0 mm).

[0034] A similar experiment was conducted with the mold protection speed set to 20%. In the vertical injection molding machine 1A according to the second embodiment, the paper cup was detected as a foreign object when its height reached 72.6 mm (a decrease of 1.4 mm), and in the vertical injection molding machine 51 according to the comparative example, the paper cup was detected as a foreign object when its height reached 70.7 mm (a decrease of 3.3 mm).

[0035] When the same experiment was conducted with the mold protection speed set to 40%, 60%, 80%, and 100%, the paper cup was detected as a foreign object in all cases in the vertical injection molding machine 1A according to the second embodiment. Specifically, when the height of the paper cup reached 72.2 mm (1.8 mm reduction), 71.6 mm (2.4 mm reduction), 71.1 mm (2.9 mm reduction), and 70.8 mm (3.2 mm reduction), it was detected as a foreign object and the mold opening / closing motor 18 stopped. However, in the vertical injection molding machine 51 according to the comparative example, no foreign object was detected at any of the settings, and the mold opening / closing motor 18 did not stop.

[0036] The vertical injection molding machine 1A (see Figure 2) according to the second embodiment was able to detect foreign matter trapped in the molds 19 and 20 while the paper cup was still small, compared to the vertical injection molding machine 51 (see Figure 5) according to the comparative example. In other words, it was confirmed that the accuracy of detecting foreign matter trapped in the molds was high and that the molds 19 and 20 could be properly protected.

[0037] The present invention has been described in detail above based on embodiments, but it goes without saying that the present invention is not limited to the embodiments already described, and various modifications are possible without departing from the spirit of the invention. The multiple examples described above can also be implemented in combination as appropriate. [Explanation of Symbols]

[0038] 1 Vertical injection molding machine 2 Mold clamping device 3. Injection device 4. Control device 7 beds 9 fixed plate 10 Upper movable plate 11 Lower movable plate 12 Ball spline 14 Toggle mechanism 15 Turntable 17 Ball screw mechanism 18 Type opening / closing motor 19 Upper mold 20 Lower mold 22 Spline shaft 23 Ball holder 25 Servo motor for turntable 26 Drive pulley 27 Timing belt 31 Heating cylinder 32 Screw 33 Screw drive mechanism 35 Lifting device 40 Ball screw mechanism 41 Ball screw 42 Ball nut 43 Load cell 44 Rotational transmission mechanism 46 Rotation axis

Claims

1. Fixed plate and An upper movable plate is provided above the aforementioned fixed plate, A lower movable plate is provided below the fixed plate, Multiple rod-shaped members connecting the upper movable platen and the lower movable platen, A clamping mechanism is provided between the fixed platen and the lower movable platen, Each of the aforementioned rod-shaped members is made of a ball spline. The aforementioned ball spline consists of a spline shaft and a ball holder which houses a large number of balls and slides along the spline shaft due to the rolling of the balls. A vertical clamping device in which the ball holder is provided on the fixed platen and the spline shaft connects the upper movable platen and the lower movable platen.

2. The vertical clamping device according to claim 1, wherein the clamping mechanism comprises a ball screw mechanism provided between the fixed platen and the lower movable platen, and a clamping servo motor that drives the ball screw mechanism.

3. Vertical clamping device, It consists of an injection device installed on the aforementioned vertical clamping device, The aforementioned vertical clamping device comprises a fixed plate and An upper movable plate is provided above the aforementioned fixed plate, A lower movable plate is provided below the fixed plate, Multiple rod-shaped members connecting the upper movable platen and the lower movable platen, A clamping mechanism is provided between the fixed platen and the lower movable platen, Each of the aforementioned rod-shaped members is made of a ball spline. The aforementioned ball spline consists of a spline shaft and a ball holder which houses a large number of balls and slides along the spline shaft due to the rolling of the balls. A vertical injection molding machine in which the ball holder is provided on the fixed platen and the spline shaft connects the upper movable platen and the lower movable platen.

4. The vertical injection molding machine according to claim 3, wherein the clamping mechanism comprises a ball screw mechanism provided between the fixed platen and the lower movable platen, and a clamping servo motor that drives the ball screw mechanism.

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