Clamping device for injection molding machines

Abstract

A mold closing device (16) of an injection molding machine (10) is provided with a ball screw (26e) that is rotated by a motor (26a), a cross head (28) that is disposed between a rear platen (22) and a movable platen (24) and is moved in an axial direction of a connecting rod (34) by rotation of the ball screw, a toggle link (30) that moves the movable platen in the axial direction in accordance with movement of the cross head, and a cross head pressing mechanism (PM) that presses the cross head in a manner that the cross head is moved toward the rear platen side.

Description

Technical Field

[0001] This invention relates to a mold closing device for an injection molding machine. Background Technology

[0002] Injection molding machines have a mold-closing device that opens and closes metal molds (fixed mold and moving mold). The mold-closing device generates a closing force, for example, by extending a toggle mechanism (toggle link, etc.) using a drive mechanism. Here, to suppress energy consumption of the drive mechanism, it is preferable that the toggle mechanism is fully extended when generating the closing force. However, if this extended state continues for a long time, the toggle mechanism may become fixed due to oil film rupture, etc. As a result, the mold-closing device cannot operate. Japanese Patent Application Publication No. 11-198202 discloses a countermeasure as follows: before stopping the mold-closing device, the movable pressure plate is retracted from its contact position with the metal mold. Summary of the Invention

[0003] However, due to power outages or malfunctions, the drive mechanism may fail to operate, resulting in the inability to retract the movable pressure plate. Therefore, it is preferable to be able to retract the movable pressure plate and release the extended state of the toggle mechanism even if the drive mechanism fails to operate.

[0004] The purpose of this invention is to solve the aforementioned problem.

[0005] One method involves a clamping device for an injection molding machine comprising: a fixed pressure plate that holds a fixed mold; a rear pressure plate; a plurality of connecting rods that connect the fixed pressure plate and the rear pressure plate; a movable pressure plate disposed between the fixed pressure plate and the rear pressure plate, holding the movable mold in such a way that the movable mold and the fixed mold are opposite to each other, and movable along the axial direction of the connecting rods; a ball screw that is rotated by a motor; a crosshead disposed between the rear pressure plate and the movable pressure plate, and movable along the axial direction by the rotation of the ball screw; a toggle mechanism that moves the movable pressure plate along the axial direction according to the movement of the crosshead; and a crosshead pressing mechanism that presses the crosshead by moving the crosshead toward the rear pressure plate side.

[0006] According to the present invention, a mold closing device for an injection molding machine is provided that can release the extended state of the toggle mechanism even when the drive mechanism for driving the toggle mechanism is not operational. Attached Figure Description

[0007] Figure 1 This is a diagram illustrating an injection molding machine used in an embodiment.

[0008] Figure 2 This is a perspective view showing the state of the crosshead as observed from the movable pressure plate in the injection molding machine of the embodiment.

[0009] Figure 3 This is a top view showing the state of the crosshead as observed from the upper toggle link in the injection molding machine of the embodiment.

[0010] Figure 4 This is a top view showing the state of the crosshead as observed from the upper toggle link in the injection molding machine of Modified Example 1.

[0011] Figure 5 This is a top view showing the state of the crosshead as observed from the upper toggle link in the injection molding machine of Modified Example 2.

[0012] Figure 6 This is a top view showing the state of the crosshead as observed from the upper toggle link in the injection molding machine of Modified Example 3. Detailed Implementation

[0013] The mold clamping device of the injection molding machine according to the embodiment will be described in detail below.

[0014] Figure 1 This is a diagram illustrating an injection molding machine 10 according to an embodiment. The injection molding machine 10 includes a base 12, a mold clamping device 16 for opening and closing a metal mold 14, and an injection device (not shown) for injecting molten resin into the metal mold 14. Additionally, in Figure 1 The text shows the up-down and front-back directions.

[0015] The base 12 is a platform for mounting the mold clamping device 16 and the injection device. The mold clamping device 16 has a fixed pressure plate 20, a rear pressure plate 22, a movable pressure plate 24, a drive mechanism 26, a crosshead 28, a toggle link 30, and a crosshead link 32.

[0016] The fixed pressure plate 20 and the rear pressure plate 22 are disposed on the base 12 and are connected to each other by four connecting rods 34. The four connecting rods 34 extend parallel to each other in the front-back direction and pass through the movable pressure plate 24. The front-back direction is the axial direction of the four connecting rods 34. The movable pressure plate 24 is disposed on the base 12 between the fixed pressure plate 20 and the rear pressure plate 22 via a sliding part 36. A guide rail 38 is disposed on the base 12 in the front-back direction. The sliding part 36 can move along the guide rail 38. Thus, the movable pressure plate 24 can move forward and backward relative to the fixed pressure plate 20 in the front-back direction. In addition, the four connecting rods 34 function as guiding members and mold clamping force generating members. The guiding members guide the movement of the movable pressure plate 24 in the front-back direction. When the toggle link 30 extends, the mold clamping force generating member generates a predetermined mold clamping force on the metal mold 14 through a reaction force.

[0017] A metal mold 14 is disposed between the fixed pressure plate 20 and the movable pressure plate 24. The metal mold 14 has a fixed mold 14a and a movable mold 14b. The fixed mold 14a is mounted on the side of the fixed pressure plate 20 facing the movable pressure plate 24. The movable mold 14b is mounted on the side of the movable pressure plate 24 facing the fixed pressure plate 20.

[0018] The drive mechanism 26 causes the crosshead 28 to move forward and backward in the front-back direction. The drive mechanism 26 includes a mold opening and closing motor 26a (drive source), a drive pulley 26b, a belt 26c, a driven pulley 26d, a ball screw 26e, and a nut 26f.

[0019] The drive pulley 26b is capable of rotating integrally with the rotating shaft of the mold opening / closing motor 26a. The driven pulley 26d is capable of rotating integrally with the ball screw 26e. The belt 26c is attached to the drive pulley 26b and the driven pulley 26d. The belt 26c transmits the rotational force of the drive pulley 26b to the driven pulley 26d. The ball screw 26e extends in the front-rear direction parallel to the axis of the connecting rod 34. The nut 26f is fixed to the crosshead 28 and screwed onto the ball screw 26e.

[0020] The mold-opening and closing motor 26a rotates the ball screw 26e via the drive pulley 26b, belt 26c, and driven pulley 26d. When the ball screw 26e rotates relative to the nut 26f, the nut 26f moves forward and backward along the ball screw 26e. Thus, as the ball screw 26e rotates, the crosshead 28 moves forward and backward together with the nut 26f.

[0021] Here, the nut 26f is moved forward and backward by rotating the ball screw 26e, but the configuration and function of the ball screw 26e and nut 26f can also be reversed as follows. First, the nut 26f is rotated by the die-opening motor 26a. With the rotation of the nut 26f, the ball screw 26e, which is screwed to the nut 26f, moves forward and backward. As a result, the crosshead 28 can move forward and backward. In short, by rotating the ball screw 26e relative to the nut 26f, the crosshead 28 moves in the back-and-forth direction.

[0022] To stabilize the forward and backward movement of the crosshead 28, the crosshead 28 is guided by a guide rod 40 extending in the front-to-back direction. The guide rod 40 is held in a guide rod bracket 42 provided on the rear pressure plate 22.

[0023] Two toggle links 30 and two crosshead links 32 are positioned at the top. Additionally, two toggle links 30 and two crosshead links 32 are positioned at the bottom. That is, a total of four toggle links 30 and four crosshead links 32 are provided. Here, two toggle links 30 and two crosshead links 32 are shown above and below the surface of the paper. The two toggle links 30 and two crosshead links 32 on the inner side of the paper are hidden behind. Each toggle link 30 has a first link 30a, a second link 30b, a first toggle pin 30c, a second toggle pin 30d, and a third toggle pin 30e.

[0024] One end of the first link 30a is rotatably connected to the movable pressure plate 24 via the first toggle pin 30c. One end of the second link 30b is rotatably connected to the rear pressure plate 22 via the second toggle pin 30d. The other ends of the first link 30a and the second link 30b are rotatably connected to each other via the third toggle pin 30e. The second link 30b is connected to the crosshead 28 via the crosshead link 32.

[0025] The toggle link 30 is connected to the crosshead 28 via the crosshead link 32. The toggle link 30 extends or bends in response to the forward and backward movement of the crosshead 28, thereby causing the movable pressure plate 24 to move forward and backward in the same direction. The toggle link 30 and the crosshead link 32 are toggle mechanisms that increase the forward and backward driving force of the crosshead 28 and transmit this increased driving force to the movable pressure plate 24. As the crosshead 28 moves forward, the toggle link 30 extends. As a result, the movable pressure plate 24 moves forward. Conversely, as the crosshead 28 moves backward, the toggle link 30 bends and retracts. As a result, the movable pressure plate 24 moves backward. Furthermore, even when the toggle link 30 is extended, the closing force of the metal mold 14 can be maintained even if the forward movement of the crosshead 28 by the mold opening / closing motor 26a stops.

[0026] As described above, the ball screw 26e is rotated by the mold opening and closing motor 26a, thereby causing the crosshead 28 to move forward and backward. As the crosshead 28 moves forward and backward, the toggle link 30 extends or bends. As a result, the movable pressure plate 24 moves forward and backward, and the metal mold 14 opens and closes in the front-to-back direction.

[0027] The mold clamping device 16 includes a crosshead pressing mechanism PM. The crosshead pressing mechanism PM presses the crosshead 28 by moving the crosshead 28 toward the rear pressure plate 22. As described above, if the toggle mechanism (toggle link 30 and crosshead link 32) remains in a fully extended state for an extended period, the toggle mechanism may become fixed due to oil film rupture, etc. As a result, the mold clamping device 16 cannot operate. The crosshead pressing mechanism PM is a mechanism used to release the extended state of the toggle mechanism even when the mold opening / closing motor 26a is not used. Furthermore, oil film rupture refers to the loss of the oil film (lubricating oil film) formed between sliding parts. That is, the sliding parts are in direct contact with each other. For example, the sliding parts are between the first link 30a and the first toggle pin 30c. If the toggle mechanism extends, the oil film between, for example, the first link 30a and the first toggle pin 30c is forced out by pressure, thus easily causing oil film rupture.

[0028] The following is a detailed description of the crosshead 28, the guide rod 40, and the crosshead pressing mechanism PM. Figure 2 This is a perspective view showing the state of the crosshead 28 as observed from the movable pressure plate 24 in the injection molding machine 10 of the embodiment. Additionally, Figure 3 This is a top view showing the state of the crosshead 28 as observed from the upper toggle link 30 in the injection molding machine 10 of the embodiment. Additionally, in Figure 2 In the diagram, for ease of understanding, connecting rod 34 is represented by an imaginary line instead of a solid line. The following is basically based on... Figure 3 Please provide an explanation.

[0029] The crosshead 28 has a central portion 28a, two arms 28b extending upward and downward from the central portion 28a, and two arms 28c extending to the left and right from the central portion 28a. A crosshead connecting rod 32 is connected to the arms 28b, but... Figure 2 and Figure 3 For ease of understanding, the description of the crosshead connecting rod 32 has been omitted. Two guide rods 40 are inserted into each of the two arms 28c. That is, the crosshead 28 is guided by the two guide rods 40 extending in the front-back direction, allowing it to move forward and backward in that direction.

[0030] Two guide rods 40 are respectively positioned on the left and right sides of the ball screw 26e. The two guide rods 40 extend in the front-to-back direction. The rear ends of the two guide rods 40 are supported by the rear pressure plate 22. The front ends of the two guide rods 40 are respectively supported on two guide rod supports 42. The two guide rod supports 42 have a generally U-shaped form. Each of the two guide rod supports 42 has two bases 42a and a support portion 42b. The two bases 42a are fixed to the front surface of the rear pressure plate 22 and protrude forward. The support portion 42b is located at the front end of the two bases 42a. The support portion 42b supports the guide rods 40.

[0031] The mold clamping device 16 includes two crosshead pressing mechanisms PM. Each crosshead pressing mechanism PM has a threaded component 44 and a support component S, which is screwed onto and supports the threaded component 44. In this embodiment, the support portion 42b of the guide rod bracket 42 functions as the support component S. Therefore, the support portion 42b has an internal thread (threaded hole) 42c that engages with the threaded component 44.

[0032] The threaded component 44 is shaped to extend in the front-to-back direction and has an external threaded portion 44a and a head 44b. The external threaded portion 44a engages with the internal threaded portion 42c of the support component S (support portion 42b). The head 44b is fixed to the end of the external threaded portion 44a, causing the external threaded portion 44a to rotate. By holding a tool such as a wrench on the head 44b, the head 44b is rotated relative to the support portion 42b. As a result, the threaded component 44 moves rearward relative to the support portion 42b. Consequently, the threaded component 44 presses against the crosshead 28, causing the crosshead 28 to move rearward.

[0033] Thus, even in the event of a malfunction or power outage in the mold opening / closing motor 26a, the crosshead 28 can be retracted by rotating the threaded component 44. This releases the extended state (e.g., locked state) of the toggle mechanism. The locked state occurs when the toggle link 30 extends beyond a predetermined distance, resulting in a clamping force between the fixed mold 14a and the moving mold 14b. By releasing the extended state of the toggle mechanism, the clamping force is released. Consequently, it prevents the toggle mechanism from becoming stuck due to issues such as oil film rupture. The threaded component 44 of the crosshead pressing mechanism PM can output the force (axial force) required to release the locked state. Normally, when clamping force is generated, the friction between the sliding components within the toggle link 30 increases. By applying a large torque to the threaded component 44 of the crosshead pressing mechanism PM using a tool, the friction at the toggle link 30 is overcome, and the force (axial force) required to release the locked state is output from the threaded component 44 to the crosshead 28.

[0034] Here, the two crosshead pressing mechanisms PM (threaded component 44 and support component S) are symmetrically arranged relative to the ball screw 26e in the width direction (left-right direction) of the mold clamping device 16, which is orthogonal to the front-back direction. As a result, a symmetrical pressing force in the width direction is applied to the crosshead 28 from the two crosshead pressing mechanisms PM. This facilitates the movement of the crosshead 28.

[0035] (Variation Example 1)

[0036] The injection molding machine 10 of modified example 1 will be described. Figure 4 This is a top view showing the state of the crosshead 28 as viewed from the upper toggle link 30 in the injection molding machine 10 of Modified Example 1. Furthermore, elements identical to those in the embodiment are labeled with the same reference numerals, and descriptions are omitted.

[0037] The injection molding machine 10 in Modification 1 has a support member 46. The support member 46 functions as a support member S for the threaded member 44 by engaging with the threaded member 44. That is, the guide rod bracket 42 does not function as a support member S here. The support member 46 is fixed to the guide rod bracket 42. The support member 46 has two internal threads 46a (threaded holes) that engage with the two threaded members 44. Thus, the crosshead pressing mechanism PM can also have a support member S, which is fixed to the guide rod bracket 42 and does not directly contribute to the support of the guide rod 40. Except for the points mentioned above, Modification 1 is substantially the same as the embodiment, so detailed description is omitted.

[0038] (Variation Example 2)

[0039] The injection molding machine 10 of modified example 2 will be described. Figure 5 This is a top view showing the state of the crosshead 28 as viewed from the upper toggle link 30 in the injection molding machine 10 of Modified Example 2. Furthermore, elements identical to those in the embodiment are labeled with the same reference numerals, and descriptions are omitted.

[0040] In Modification 2, the support member S of the crosshead pressing mechanism PM is supported on a base member 48 fixed to the rear pressure plate 22. The support member S has an internal thread Sa (threaded hole) that engages with the threaded member 44. The base member 48 is a different member from the guide rod support 42. Thus, the crosshead pressing mechanism PM can also have a support member S that is not fixed to the guide rod support 42. Apart from the points mentioned above, Modification 2 is substantially the same as the embodiment, so detailed description is omitted.

[0041] (Variation Example 3)

[0042] The injection molding machine 10 of modified example 3 will be described. Figure 6 This is a top view showing the state of the crosshead 28 as viewed from the upper toggle link 30 in the injection molding machine 10 of Modified Example 3. Furthermore, elements identical to those in the embodiment are labeled with the same reference numerals, and descriptions are omitted.

[0043] The crosshead pressing mechanism PM of Variation Example 3 has a rod 52, a drive unit 54, and a support member S (support member 42b). The rod 52 has a shape that extends in the front-rear direction. The drive unit 54 is, for example, a linear electric motor or a hydraulic cylinder that moves the rod 52 in the front-rear direction. The support member S (support member 42b) supports the drive unit 54. The support member S has a through hole 42d through which the rod 52 passes. Alternatively, the drive unit 54 may be a combination of an electric motor and a conversion mechanism that converts rotary motion into linear motion. Thus, the crosshead pressing mechanism PM may also have a drive unit 54. The drive unit 54 of the crosshead pressing mechanism PM overcomes the friction at the toggle link 30 and outputs the force (axial force) required to release the locked state. Except for the points mentioned above, Variation Example 3 is substantially the same as the embodiment, so detailed description is omitted.

[0044] (Other variations)

[0045] In the above embodiments and variations, two crosshead pressing mechanisms PM are provided, but the number of crosshead pressing mechanisms PM can be one or more. Using one or more crosshead pressing mechanisms PM, the crosshead 28 can be pressed and retracted.

[0046] In addition, in the implementation and variations, the crosshead pressing mechanism PM is provided on the rear pressure plate 22, but the crosshead pressing mechanism PM can also be provided on other components such as the base 12.

[0047] In Modification 3, the drive unit 54 is supported by the support part 42b of the guide rod bracket 42, but it can also be supported by the support member 46 or the support member S shown in Modification 1 or Modification 2.

[0048] [Modified Implementation]

[0049] This invention is not limited to the embodiments described herein, and various structures can be adopted without departing from the spirit of this invention.

[0050] (Invention derived from implementation methods)

[0051] Hereinafter, inventions that can be mastered according to the described embodiments and variations will be described.

[0052] [1] The mold closing device 16 of the injection molding machine 10 includes: a fixed pressure plate 20 that holds a fixed mold 14a; a rear pressure plate 22; a plurality of connecting rods 34 that connect the fixed pressure plate and the rear pressure plate; a movable pressure plate 24 that is disposed between the fixed pressure plate and the rear pressure plate, holds the movable mold 14b facing the fixed mold, and is movable along the axial direction of the connecting rods; a ball screw 26e that is rotated by a motor (mold opening and closing motor 26a); a crosshead 28 that is disposed between the rear pressure plate and the movable pressure plate and moves along the axial direction by the rotation of the ball screw; toggle mechanisms 30 and 32 that move the movable pressure plate along the axial direction according to the movement of the crosshead; and a crosshead pressing mechanism PM that presses the crosshead by moving the crosshead toward the rear pressure plate side. Therefore, even in the event of motor failure or power outage, the crosshead can be moved towards the rear pressure plate by pressing the crosshead pressing mechanism. As a result, the movable pressure plate moves, causing the moving mold to separate from the fixed mold and releasing the mold closing force.

[0053] [2] The crosshead pressing mechanism has a threaded member 44 extending along the axial direction; and a support member (S, 46, support portion 42b) screwed to and supporting the threaded member, wherein the threaded member rotates relative to the support member, thereby pressing the crosshead. Thus, by rotating the threaded member, the crosshead can be pressed and moved.

[0054] [3] The crosshead pressing mechanism includes: a rod 52 extending along the axial direction; a drive unit 54 that moves the rod along the axial direction; and a support member (S, support unit 42b) that supports the drive unit, wherein the rod presses the crosshead. Thus, the rod can press the crosshead and move it by means of the drive unit.

[0055] [4] The support member is fixed to the rear pressure plate. Thus, the crosshead can be moved by pressing it with the threaded part or drive part held by the support member fixed to the rear pressure plate.

[0056] [5] A guide rod 40 extending along the axial direction and guiding the crosshead is provided, and the support member supports the guide rod. Thus, the support member can support the guide rod and the threaded component (or drive unit).

[0057] [6] In the width direction of the mold clamping device orthogonal to the axis direction, a plurality of crosshead pressing mechanisms are provided symmetrically with respect to the ball screw. Therefore, a symmetrical pressing force in the width direction can be applied to the crosshead using the plurality of crosshead pressing mechanisms symmetrical with respect to the ball screw.

[0058] [7] The crosshead pressing mechanism releases the toggle mechanism from its predetermined extension and creates a locking state of mold-closing force between the fixed mold and the moving mold. This releases the mold-closing force and prevents the oil film of the toggle mechanism from rupturing, thereby preventing the toggle mechanism from becoming stuck.

Claims

1. A mold clamping device for an injection molding machine, characterized in that, The mold clamping device of this injection molding machine includes: A fixed pressure plate is used to hold the mold in place. Rear pressure plate; Multiple connecting rods connect the fixed pressure plate to the rear pressure plate; A movable pressure plate is disposed between the fixed pressure plate and the rear pressure plate, which holds the moving mold in such a way that the moving mold and the fixed mold face each other, and can move along the axial direction of the connecting rod; A ball screw, which is rotated by an electric motor; A crosshead is disposed between the rear pressure plate and the movable pressure plate and moves along the axial direction by the rotation of the ball screw; The toggle mechanism moves the movable pressure plate along the axial direction according to the movement of the crosshead; as well as A crosshead pressing mechanism that presses the crosshead by moving it toward the rear pressure plate. The crosshead pressing mechanism has a threaded component extending along the axial direction and a support component screwed to and supporting the threaded component. The threaded component rotates relative to the support component, thereby moving the threaded component in a direction from the movable pressure plate toward the crosshead and pressing the crosshead by abutting against it.

2. A mold clamping device for an injection molding machine, characterized in that, The mold clamping device of this injection molding machine includes: A fixed pressure plate is used to hold the mold in place. Rear pressure plate; Multiple connecting rods connect the fixed pressure plate to the rear pressure plate; A movable pressure plate is disposed between the fixed pressure plate and the rear pressure plate, which holds the moving mold in such a way that the moving mold and the fixed mold face each other, and can move along the axial direction of the connecting rod; A ball screw, which is rotated by an electric motor; A crosshead is disposed between the rear pressure plate and the movable pressure plate and moves along the axial direction by the rotation of the ball screw; The toggle mechanism moves the movable pressure plate along the axial direction according to the movement of the crosshead; as well as A crosshead pressing mechanism that presses the crosshead by moving it toward the rear pressure plate. The crosshead pressing mechanism includes: a rod extending along the axial direction; a drive unit that moves the rod along the axial direction; and a support member that supports the drive unit, wherein the rod moves in a direction from the movable pressure plate toward the crosshead and abuts against the crosshead, thereby pressing the crosshead.

3. The mold clamping device of the injection molding machine according to claim 1 or 2, characterized in that, The support component is fixed to the rear pressure plate.

4. The mold clamping device of the injection molding machine according to claim 3, characterized in that, The mold clamping device of the injection molding machine includes a guide rod that extends along the axial direction and guides the crosshead. The support component supports the guide rod.

5. The mold clamping device of the injection molding machine according to claim 1 or 2, characterized in that, In the width direction of the mold clamping device, which is orthogonal to the axis, a plurality of crosshead pressing mechanisms are arranged symmetrically with respect to the ball screw.

6. The mold clamping device of the injection molding machine according to claim 1 or 2, characterized in that, The crosshead pressing mechanism releases the toggle mechanism and extends it beyond a predetermined point, thereby creating a locking state of mold closing force between the fixed mold and the moving mold.

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