Clamping device and tie bar

Abstract

To reduce a drive-in amount of a movable platen.SOLUTION: At least one tie bar 25 is shaped so as to have two or more different projected widths L1, L2 orthogonal to an axial direction of the tie bar 25 corresponding to those projected positions when projected from two or more different positions on its axial outer periphery. Furthermore, the tie bar 25 has, at least in a part between a fixed platen 21 and a toggle support 24, a cross-sectional area greater than an area of a virtual circle whose diameter is the smallest projection width L1 of the two or more different projection widths L1, L2. The increased cross-sectional area of the tie bar 25 increases the stiffness.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a clamping device and a tie bar. [Background technology]

[0002] Patent Document 1 discloses that an adjustment part that artificially increases the cross-sectional area of ​​a plurality of tie bars is attached to the tie bars in order to adjust the balance of the tie bars (see paragraphs 0014, 0016, Figures 4 and 5). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5808286 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to obtain a target clamping force, after the mold touch of the mold unit (i.e., the state in which the fixed mold and the movable mold are in contact with each other), it is required to further advance the crosshead of the toggle mechanism to move the movable platen in the clamping direction. The moving distance of the movable platen required to achieve the target clamping force is called the plunge amount (or the amount of pushing in) (see FIG. 10). If the plunge amount is large, there is a concern that the specifications of the drive system (e.g., the mold clamping motor and / or ball screw) used for this purpose will be high, or that a relatively large amount of power will be required each time the mold is clamped, making it difficult to reduce the power consumption of the mold clamping unit.

[0005] In view of the above-mentioned problems, the inventors of the present application have discovered a new object of reducing the amount of thrust of the movable platen. [Means for solving the problem]

[0006] A mold clamping device according to one aspect of the present disclosure includes a fixed platen, a movable platen, a toggle mechanism, and a toggle support, the toggle support and the movable platen are connected to each other via the toggle mechanism, and the movable platen can be advanced and retreated relative to the fixed platen based on an operation of the toggle mechanism, a plurality of tie bars extending between the fixed platen and the toggle support and connecting the fixed platen and the toggle support to each other; At least one of the plurality of tie bars is (i) configured to have two or more distinct projected widths perpendicular to the axial direction of the tie bar when illuminated with parallel light propagating in directions perpendicular to the axial direction and different from one another; and (ii) At least a portion between the fixed platen and the toggle support has a cross-sectional area larger than the area of ​​an imaginary circle having a diameter equal to the smallest projected width among the two or more different projected widths.

[0007] A tie bar of a mold clamping device according to one aspect of the present disclosure includes: A first end portion; A second end. a middle portion extending between the first and second ends; The intermediate portion is (i) configured to have two or more distinct projected widths perpendicular to the axial direction of the tie bar when illuminated with parallel light propagating in directions perpendicular to the axial direction of the tie bar and different from one another; and (ii) Over at least a portion of its entire length, it has a cross-sectional area larger than an imaginary circle having a diameter equal to the smallest projected width among the two or more different projected widths.

[0008] One aspect of the present disclosure facilitates reducing the amount of moving platen indentation. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing a general configuration of an injection molding machine according to one embodiment of the present disclosure. [Diagram 2]FIG. 1 is a perspective view showing a schematic configuration of a mold clamping device according to an embodiment of the present disclosure. [Diagram 3] FIG. 2 is a schematic side view of a tie bar according to one aspect of the present disclosure. [Figure 4] FIG. 11 shows that a thread groove is provided on the first insertion end of the tie bar. [Diagram 5] 5(c) are cross-sectional views of a tie bar, in which (a) shows a cross-sectional view of a first insertion end, (b) shows a cross-sectional view of a second insertion end, and (c) shows a cross-sectional view of an intermediate portion. In Fig. 5(c), circle C1 in Fig. 5(a) is shown by a dotted line, and circle C2 in Fig. 5(b) is shown by a dashed line. [Figure 6] FIG. 13 illustrates that the middle portion of the tie bar has a first projected width. [Figure 7] FIG. 13 shows that the middle portion of the tie bar has a second projected width. [Figure 8] FIG. 2 is a schematic diagram showing that the middle portion of the tie bar has a rectangular cross section and showing that a predetermined gap is set between the parallel extending tie bars. [Figure 9] 1 is a schematic top view of an intermediate portion of a tie bar, in which wide and narrow portions alternate in the axial direction of the tie bar. [Figure 10] 4 is a graph referred to for explaining the amount of thrust of the movable platen and its improvement. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, non-limiting embodiments and features of the present invention will be described with reference to Figs. 1 to 10. Those skilled in the art can combine the embodiments and / or features without the need for excessive explanation, and can also understand the synergistic effect of this combination. In principle, overlapping explanations between embodiments will be omitted. The reference drawings are primarily intended to describe the invention, and are simplified for the convenience of drawing. Each feature is not only effective for the mold clamping device disclosed in this specification, but is understood as a universal feature that is also applicable to various other mold clamping devices not disclosed in this specification.

[0011] As shown in FIG. 1, the injection molding machine 1 has a mold clamping unit 2 and an injection unit 3 mounted on a common or different base 4. The injection molding machine 1 continuously manufactures molded products based on the coordinated operation of the mold clamping unit 2 and the injection unit 3. The mold clamping unit 2 is configured to repeat a loop of mold closing, mold clamping, and mold opening. The injection unit 3 is configured to repeat a loop of a metering process, a filling process, and a pressure holding process. A mold unit 5 is attached to the mold clamping unit 2. The specific configuration of the mold unit 5 is determined by the shape, size, and number of injection molded products. The mold unit 5 may be of a two-plate type or a three-plate type. In some embodiments, the mold unit 5 has one or more fixed molds 51 and one or more movable molds 52.

[0012] The configurations and operations of the mold clamping unit 2 and the injection unit 3 will be described in more detail below. The mold clamping unit 2 includes a fixed platen 21, a movable platen 22, a toggle mechanism 23, a toggle support 24, a plurality of tie bars 25, a mold clamping motor 26, and a mold thickness adjustment mechanism 27. The toggle support 24 and the movable platen 22 are connected via the toggle mechanism 23, and the movable platen 22 can advance and retreat with respect to the fixed platen 21 based on the operation of the toggle mechanism 23. Specifically, the state of the toggle mechanism 23 changes due to the operation of the mold clamping motor 26, and the position of the movable platen 22 changes. When the gap between the fixed platen 21 and the movable platen 22 is large, the mold device 5 can be introduced into the space between the fixed platen 21 and the movable platen 22. In this state, the fixed and movable molds 51 and 52 are attached to the fixed and movable platens 21 and 22, respectively. After that, the movable platen 22 is moved toward the fixed platen 21 to close the mold device 5, followed by mold clamping, and finally mold opening. The mold closed state is a state in which the opposing surfaces of the fixed mold 51 and the movable mold 52 are in contact with each other, and the half-cavity of the fixed mold 51 and the half-cavity of the movable mold 52 are spatially connected. The mold clamped state is a state in which the movable mold 52 is pressed firmly against the fixed mold 51 to withstand the injection pressure of the material from the injection unit 3. The mold opened state is a state in which the opposing surfaces of the fixed mold 51 and the movable mold 52 are not in contact with each other, and a gap is provided between them.

[0013] The toggle mechanism 23 has a crosshead 23a that receives a driving force from a mold clamping motor 26, first and second links 23b, 23c pivotally connected between the toggle support 24 and the movable platen 22, and a third link 23d that connects the crosshead 23a and the first link 23b. A rotational force generated by the mold clamping motor 26 is converted into a linear thrust by a force conversion device such as a ball screw 262 via a belt 261 and applied to the crosshead 23a. For example, in response to the forward rotation of the output shaft of the mold clamping motor 26, the crosshead 23a moves straight toward the fixed platen 21, the angle between the first link 23b and the second link 23c becomes larger, and the movable platen 22 moves straight toward the fixed platen 21. In response to the reverse rotation of the output shaft of the mold clamping motor 26, the crosshead 23a is moved in a direction away from the fixed platen 21, the angle between the first link 23b and the second link 23c becomes smaller, and the movable platen 22 moves straight in a direction away from the fixed platen 21. Note that in the mold clamping unit 2, the direction in which the movable platen 22 and the movable mold 52 attached thereto move toward the fixed platen 21 and the fixed mold 51 attached thereto can also be defined as the front side or injection unit side, and the opposite direction can also be defined as the rear side or reflection injection molding unit side.

[0014] The toggle mechanism 23 operates to double the thrust applied to the crosshead 23a and transmit it to the movable platen 22. The magnification is also called the toggle magnification. The toggle magnification changes according to the angle between the first link 23b and the second link 23c. When the angle between the first link 23b and the second link 23c approaches 180°, the toggle magnification also increases.

[0015] The mold thickness adjustment mechanism 27 is configured to adjust the position of the toggle support 24 relative to the fixed platen 21 (the front-rear distance between them, in other words, the mold thickness). The mold thickness adjustment mechanism 27 includes a mold thickness adjustment motor 27a. A rotational force generated by the mold thickness adjustment motor 27a is transmitted to a nut screwed onto a screw shaft at the rear end of the tie bar 25 via a belt 271, changing the position of the toggle support 24 along the tie bar 25 and changing the position of the toggle support 24 relative to the fixed platen 21 (i.e., the distance between them). The rotational force of the mold thickness adjustment motor 27a is transmitted to the nut via a transmission element such as a belt and a gear (or directly).

[0016] The mold clamping device 2 includes an ejector device 28 for ejecting a molded product from the mold device 5. The ejector device 28 is attached, for example, to the rear of the movable platen 22. The ejector device 28 includes an ejector rod and an ejector motor that supplies power to the ejector rod. A rotational force generated by the ejector motor is converted into a linear force by a ball screw and transmitted to the ejector rod. When the ejector rod is advanced, it pushes the ejector plate of the mold device 5. The ejector pin pushes the molded product of the movable mold 52 and ejects it from the mold device 5. The injection molding machine 1 operates the ejector device in synchronization with mold opening.

[0017] The injection unit 3 supplies molten resin material to the mold unit 5 attached to the mold clamping unit 2. The injection unit may be of an in-line screw type or a pre-plasticizing type. In this specification, the injection unit will be described as being of an in-line screw type, but is not limited to this. The injection unit 3 has a cylinder 31, a screw 32, a heater 33, a metering motor 34, an injection motor 35, a moving motor 36, a guide rail 37, a first movable support 38, and a second movable support 39.

[0018] The cylinder 31 is a metallic tubular member that houses the screw 32, and has a cylinder body 31a and a nozzle 31b. The cylinder body 31a houses the screw 32. The nozzle 31b has a straight flow passage with a flow passage diameter smaller than that of the cylinder body 31a, and has a discharge port for discharging the molten plastic material supplied from the cylinder body 31a. The cylinder body 31a has a material supply port 31c for receiving a plastic material, such as pellets, supplied from a hopper 31f or an automated plastic material supply device. The pellets melt in response to heat transmitted from the heater 33 via the cylinder body 31a, and are transported toward the front side, i.e., the nozzle 31b, in response to the rotation of the screw 32. As will be understood from the explanation below, the movement direction of the screw 32 during filling is the front side, and the movement direction of the screw 32 during metering is the rear side.

[0019] The screw 32 has a shaft portion and a flight provided in a spiral shape on the outer periphery of the shaft portion, and conveys the solid and molten resin material to the front side of the cylinder 31 in response to the rotation of the screw 32. The screw 32 can rotate by receiving a rotational force from the metering motor 34. For example, the output shaft of the metering motor 34 and the screw 32 are mechanically connected via a belt 341. In addition, the screw 32 can move to the front side (the side approaching the nozzle portion 31b) and the rear side (the side moving away from the nozzle portion 31b) in the stationary cylinder 31 by receiving a driving force from the injection motor 35. For example, the output shaft of the injection motor 35 is connected to the screw shaft of the ball screw 351 via a belt 353. A first movable support 38 is fixed to a nut 352 of the ball screw 351. The screw 32 is rotatably attached to the first movable support 38. Similarly, the main body of the metering motor 34 is fixed to the first movable support 38. The first movable support 38 moves in response to the operation of the injection motor 35, and the screw 32 and the metering motor 34 move. The first movable support 38 is movably mounted on a guide rail 37 fixed to the base 4. The direction toward the mold clamping unit 2 can be referred to as the front, and the direction away from the mold clamping unit 2 can be referred to as the rear.

[0020] The cylinder 31 advances toward the mold clamping unit 2 upon receiving a driving force from the movement motor 36, and retreats away from the mold clamping unit 2. For example, the output shaft of the movement motor 36 is connected to the screw shaft of a ball screw 361. A second movable support 39 is connected to a nut 362 of the ball screw 361 via an elastic member (e.g., a spring) 363. The cylinder 31 is fixed to the second movable support 39 at its rear end. The second movable support 39 and the cylinder 31 move in response to the operation of the movement motor 36. The second movable support 39 is movably mounted on a guide rail 37 fixed to the base 4. Note that an instrument such as an encoder may be incorporated in each motor. The motor is feedback-controlled based on the output signal of the encoder.

[0021] A backflow prevention ring (not shown) is attached to the tip (front end) of the screw 32. The backflow prevention ring prevents the molten plastic material stored in the storage space 31e from flowing back when the screw 32 is moved toward the nozzle portion 31b inside the cylinder 31.

[0022] The heater 33 is attached to the outer periphery of the cylinder 31, and generates heat, for example, by feedback-controlled current flow. The heater 33 is attached in any manner to the outer periphery of the cylinder body portion 31a and / or the nozzle portion 31b.

[0023] The operation of the injection device 3 will be outlined below. Heat is applied to the cylinder 31 from the heater 33, and the pellets supplied into the cylinder body 31a through the hopper 31f are melted. The screw 32 rotates in the cylinder body 31a in response to the rotational force from the metering motor 34, and the plastic material is sent to the front along the spiral groove of the screw 32, and in the process, the plastic material is gradually melted. As the molten plastic material is supplied to the front side of the screw 32, the screw 32 retreats, and the molten plastic material is stored in the storage space 31e (called the "metering process"). The rotation speed of the screw 32 is detected using an encoder of the metering motor 34. In the metering process, in order to limit the sudden retreat of the screw 32, the injection motor 35 may be driven to apply back pressure to the screw 32. The back pressure to the screw 32 is detected, for example, using a pressure detector. The screw 32 retreats to a metering completion position, and a predetermined amount of molten plastic material is accumulated in the storage space 31e in front of the screw 32, and the metering process is completed.

[0024] Following the metering step, the screw 32 moves from the filling start position to the filling completion position toward the nozzle portion 31b in response to the driving force from the injection motor 35, and the molten plastic material stored in the storage space 31e is supplied into the mold device 5 through the discharge port of the nozzle portion 31b (called the "filling step"). The position and speed of the screw 32 are detected, for example, by using an encoder of the injection motor 35. When the position of the screw 32 reaches a set position, switching from the filling step to the pressure holding step (so-called V / P switching) is performed. The position where the V / P switching is performed is also called the V / P switching position. The set speed of the screw 32 may be changed according to the position of the screw 32, time, etc.

[0025] When the position of the screw 32 reaches a set position in the filling process, the screw 32 may be temporarily stopped at the set position, and then V / P switching may be performed. Immediately before V / P switching, instead of stopping the screw 32, the screw 32 may be slowly advanced or retreated. In addition, the screw position detector that detects the position of the screw 32 and the screw speed detector that detects the speed of the screw 32 are not limited to the encoder of the injection motor 35, and other types of detectors may be used.

[0026] Following the filling step, the holding pressure of the plastic material in front of the screw 32 is maintained at a set pressure in response to the forward movement of the screw 32, and the remaining plastic material is pushed out into the mold device 5 (called the "holding step"). The plastic material that is insufficient due to cooling contraction in the mold device 5 can be replenished. The holding pressure is detected, for example, using a pressure detector. The set value of the holding pressure may be changed according to the elapsed time from the start of the holding step. In the holding step, the plastic material in the cavity in the mold device 5 is gradually cooled, and when the holding step is completed, the entrance to the cavity is blocked by the solidified plastic material. This state is called a gate seal, and prevents the plastic material from flowing back from the cavity. After the holding step, the cooling step is started. In the cooling step, the plastic material in the cavity is solidified. In order to shorten the molding cycle time, the measuring step of the next molding cycle may be started during the cooling step.

[0027] Following the pressure holding step, the above-mentioned metering step is carried out.

[0028] The injection molding machine 1 has a control panel 7 (see FIG. 1) in which a control system for controlling the mold clamping device 2 and / or the injection device 3 is stored. The control system stored in the control panel 7 sequentially controls the mold clamping motor 26, the ejector motor, the metering motor 34, and the injection motor 35. The control system performs mold closing, mold clamping, and mold opening based on the control of the mold clamping motor 26. The control system performs metering, filling, and pressure holding based on the control of the metering motor 34 and the injection motor 35. The control system can eject a molded product from the movable mold 52 of the mold device 5 based on the control of the ejector motor. The control system can position the cylinder 31 at an appropriate position based on the control of the moving motor 36. In addition to the above-mentioned controls, the control system can also control the temperature adjustment of the heater 33 and the mold device 5.

[0029] For example, in one molding cycle, the metering process, mold closing process, mold clamping process, filling process, pressure dwell process, cooling process, mold opening process, and ejection process are performed in this order. The order described here is the order of the earliest start time of each process. The filling process, pressure dwell process, and cooling process are performed from the start of the mold clamping process to the end of the mold clamping process. The end of the mold clamping process coincides with the start of the mold opening process. Note that, in order to shorten the molding cycle time, multiple processes may be performed simultaneously. For example, the metering process may be performed during the cooling process of the previous molding cycle, and in this case, the mold closing process may be performed at the beginning of the molding cycle. Also, the filling process may be started during the mold closing process. Also, the ejection process may be started during the mold opening process.

[0030] 2 shows a simplified perspective view of the mold clamping unit 2, and in this case, the toggle mechanism 23 is omitted in order to show four tie bars 25. As shown in FIG. 2, the mold clamping unit 2 has one or more linear guides 29 on which the movable platen 22 is mounted. The linear guide 29 has a rail 29a and one or more running bodies 29b that can run on the rail 29a. The movable platen 22 is fixed to the running body 29b of the linear guide 29, and stable linear movement of the movable platen 22 is ensured. Note that the linear guide 29 is provided over the entire length between the fixed platen 21 and the toggle support 24, but this is not necessarily limited.

[0031] The movable platen 22 is supported by linear guides 29, and is not mechanically coupled to the tie bars 25, so to speak, in a free state. For example, the movable platen 22 is provided with holes through which the tie bars 25 are inserted, and the diameter of the holes is larger than the width of the portions through which the tie bars 25 are inserted. As a result, the movable platen 22 and the tie bars 25 are not in contact with each other. Of course, this is not the only possible embodiment, and the movable platen 22 may be mechanically coupled to the tie bars 25 by bushings.

[0032] The tie bars 25 extend between the fixed platen 21 and the toggle support 24 to connect the fixed platen 21 and the toggle support 24 to each other, and are manufactured by casting or by machining a cast metal material. The tie bars 25 are typically made of a single material such as a metal or an alloy.

[0033] As can be understood by referring to FIG. 3 in addition to FIG. 2, each tie bar 25 has a first insertion end (also simply referred to as the first end) 61 inserted into a hole provided in the toggle support 24, a second insertion end (also simply referred to as the second end) 62 inserted into a hole provided in the fixed platen 21, and an intermediate portion 63 extending between the first and second insertion ends 61, 62. The first and second insertion ends 61, 62 are both cylindrical portions. For example, the first insertion end 61 is a cylindrical portion provided with a screw groove for adjusting the mold thickness (see FIG. 4). The second insertion end 62 has one or two reduced diameter portions 62p in the axial direction of the tie bar 25, but this is not necessarily the case (see FIG. 3). The shape of the first insertion end 61 can be changed depending on the manner of connection with the toggle support 24. Similarly, the shape of the second insertion end 62 can be changed depending on the manner of connection with the movable platen 22. The boundary between the first insertion end 61 and the intermediate portion 63 is determined by the difference in cross-sectional shape between the two, but alternatively, it can be determined based on whether it is inserted into the fixed platen 21. The boundary between the second insertion end 62 and the intermediate portion 63 is determined by the difference in cross-sectional shape between the two, but alternatively, it can be determined based on whether it is inserted into the toggle support 24.

[0034] The cross-sectional shapes of the tie bar 25 in the planes PL1 to PL3 shown in FIG. 3 are shown in FIGS. 5(a) to (c). The planes PL1 to PL3 are parallel to each other and perpendicular to the axial direction of the tie bar (parallel to the mold clamping direction). As shown in FIG. 5(a), the cross-sectional shape of the first insertion end 61 is a circle with a diameter R1. When a screw groove is provided in the first insertion end 61, the apex position of the screw thread is included on the locus of the circle with the diameter R1. That is, the diameter R1 is the maximum diameter of the first insertion end 61. As shown in FIG. 5(b), the cross-sectional shape of the second insertion end 62 is a circle with a diameter R2. When a reduced diameter portion 62p is provided in the second insertion end 62, the cross-section is taken at a portion of the second insertion end 62 other than the reduced diameter portion 62p. That is, the diameter R2 is the maximum diameter of the second insertion end 62.

[0035] As shown in FIG. 5(c), the cross-sectional shape of the intermediate portion 63 is a square with a side length of L1 and a diagonal length of L2. JPEG0007666957000001.jpg1140 is established. In this embodiment, the tie bar 25 (particularly the intermediate portion 63) is shaped to have two or more different projected widths perpendicular to its axial direction when illuminated by parallel light propagating in different directions from each other perpendicular to its axial direction (e.g., a polygon with four or more sides).

[0036] As shown in Fig. 6, when parallel light is irradiated onto the middle portion 63 of the tie bar 25 from the top to the bottom in a direction parallel to the top-bottom direction, the parallel light is blocked by the tie bar 25, and a projected image is formed in accordance with the shape of the tie bar 25. Specifically, a projected image is formed with a projected width L1 equal to the length L1 of one side of the cross-sectional shape of the tie bar 25 described above. Note that this projected width L1 is the width in the direction perpendicular to the axial direction of the tie bar 25.

[0037] Similarly, when the intermediate portion 63 of the tie bar 25 is irradiated with parallel light in a direction at an angle of 45° to the top-bottom direction as shown in FIG. 7, the parallel light is blocked by the tie bar 25, and a projected image is formed in accordance with the shape of the tie bar 25. Specifically, a projected image with a projected width L2 equal to the length L2 of the diagonal of the cross-sectional shape of the tie bar 25 described above is formed. Note that this projected width L2 is the width in a direction perpendicular to the axial direction of the tie bar 25. Note that although the parallel light is set to propagate from the top side to the bottom side, it may be set to propagate in a lateral direction (direction relating to the operating side and the non-operating side of the injection molding machine 1) perpendicular to the top-bottom direction and the longitudinal direction of the tie bar 25, and in this case as well, the same characteristics as described below can be understood.

[0038] The cross-sectional area (= twice the length L1 of one side) of the middle part 63 of the tie bar 25 is larger than the area of ​​a virtual circle having a diameter equal to the smallest projection width L1 among the projection widths L1 and L2 shown in Figs. 6 and 7. In such a case, the rigidity of the middle part 63 of the tie bar 25 is increased (i.e., 4 / π times), and the reduction of the amount of penetration of the movable platen 22 is promoted. By reducing the amount of penetration, a drive system (e.g., a mold clamping motor and / or a ball screw) corresponding to a small amount of penetration can be adopted, and the cost of the mold clamping device can be reduced. In addition to or instead of this effect, the power required for mold clamping of the mold clamping device is reduced, and the power consumption of the mold clamping device can be reduced. In order to reduce the amount of penetration, it is effective to increase the rigidity of the tie bar 25, which is considered to be relatively large in deformation in the mold clamping direction.

[0039] The features described in the above paragraphs can be understood from the inscription of the circle C1 in Fig. 5(a) in the square K1 in Fig. 5(c), but it is not essential that the first insertion end 61 has a circular cross-sectional shape. A form in which the first insertion end 61 has the same cross-sectional shape as Fig. 5(c) is also envisioned. The area of ​​the square K1 in Fig. 5(c) is larger than the area of ​​the circle C2 in Fig. 5(b), but this is not necessarily the case.

[0040] The cross-sectional area (=2×L1) of the middle portion 63 of the tie bar 25 may be equal to or less than the area of ​​a virtual circle having a diameter equal to the maximum projected width L2 among the projected widths L1 and L2 shown in FIGS. 6 and 7. This allows the increase in the cross-sectional area of ​​the middle portion 63 of the tie bar 25 to be within an appropriate range. In some cases, the gap between the tie bars 25 (for example, the horizontal interval D1 (see FIG. 2)) is prevented from being shortened due to the increase in the cross-sectional area of ​​the middle portion 63 of the tie bar 25. If the horizontal interval D1 between the tie bars 25 is shortened, it may become difficult to attach the mold device 5 that has been used conventionally through the gap between the tie bars 25.

[0041] From the viewpoint of achieving both an increase in the rigidity of the tie bars 25 and securing a gap (for example, horizontal interval D1) between the tie bars 25, in some cases, the above-mentioned minimum projected width L1 is substantially equal to the diameter (for example, maximum diameter) R1 of the first insertion end 61. Additionally or alternatively, the above-mentioned maximum projected width L2 is 1.2 times (or the positive square root of 2 (root 2) times) or more and 3 times or less (although not necessarily limited to this upper limit) of the diameter (for example, maximum diameter) R1 of the first insertion end 61 in a cross section perpendicular to the axial direction of the tie bars 25, which promotes achieving both the rigidity and the gap. Note that being substantially equal means being within an error range of 5%. In other words, even if the side length L1 is different from the diameter R1, it can be said to be substantially equal to the diameter R1 as long as it is within the range of diameter R1 x 0.95 to diameter R1 x 1.05. Depending on the cross-sectional shape of the middle portion 63 of the tie bar 25 and whether or not it is chamfered, it is expected that the maximum projected width L2 will be within the range of 1.2 to 2 times the positive square root (root 2) of the diameter R1 of the first insertion end portion 61.

[0042] Traditionally or as a custom, the cross-sectional shape of the middle part 63 of the tie bar 25 is preferably circular and as thin as possible. This custom is considered to be due to various factors such as the attachment of the die assembly 5 via a gap between the tie bars 25, the formation of a screw groove for adjusting the die thickness, and the shaping of the tie bars. However, according to the study of the present inventor, such a custom is not necessarily required. For example, when the movable platen 22 is supported movably on the linear guide 29 and is in a free state (not mechanically connected) with respect to the tie bar 25, changing the cross-sectional shape of the middle part 63 of the tie bar 25 to a square or rectangular shape does not affect the movement. In addition, if the cross-sectional shape of the first insertion end 61 is selectively made circular and a screw groove for adjusting the die thickness is formed thereon, the die thickness can be adjusted as in the conventional case. In addition, by setting the cross-sectional area of ​​the middle part 63 of the tie bar 25 within an appropriate range, the use of the die assembly 5 that has been used in the past is not hindered.

[0043] The cross-sectional shape of the intermediate portion 63 of the tie bar 25 does not necessarily have to be a square, and may be a quadrangle other than a square (e.g., a rectangle or a parallelogram), or may be another polygon such as a pentagon or a hexagon. In the case shown in Fig. 8, the cross-sectional shape of the intermediate portion 63 of the tie bar 25 is a rectangle with a short side length L3, a long side length L4, and a diagonal length L5. The intermediate portions 63 of the tie bar 25 are oriented so that the short side is disposed or faces the top side or the bottom side, and the interval (e.g., horizontal interval D2) between the intermediate portions 63 of the tie bar 25 is prevented from becoming shorter than in a case where the short side is not disposed or faces the top side or the bottom side.

[0044] Similar to the considerations made with reference to Figs. 6 and 7, the rectangular cross-sectional shape of the middle portion 63 of the tie bar 25 shown in Fig. 8 can be considered. That is, when the middle portion 63 of the tie bar 25 in Fig. 8 is irradiated with parallel light from the top to the bottom in a direction parallel to the top-to-bottom direction, the tie bar 25 blocks the parallel light, forming a projected image corresponding to the shape of the tie bar 25. Specifically, a projected image with a projected width L3 equal to the length L3 of the short side of the cross-sectional shape of the tie bar 25 described above is formed. Similarly, when the middle portion 63 of the tie bar 25 in Fig. 8 is irradiated with parallel light in a horizontal direction that is at an angle of 90° to the top-to-bottom direction, the tie bar 25 blocks the parallel light, forming a projected image corresponding to the shape of the tie bar 25. Specifically, a projected image with a projected width L4 equal to the length L4 of the long side of the cross-sectional shape of the tie bar 25 described above is formed. It can also be understood that a projected image with a projected width L5 is formed depending on the angle of the parallel light with respect to the middle portion 63 of the tie bar 25.

[0045] 8, the cross-sectional area (=length of short side L3 × length of long side L4) of the middle portion 63 of the tie bar 25 is larger than the area of ​​an imaginary circle having a diameter equal to the smallest projected width L3 among the projected widths L3, L4, and L5. Similarly, the cross-sectional area of ​​the middle portion 63 of the tie bar 25 is equal to or smaller than the area of ​​an imaginary circle having a diameter equal to the largest projected width L5 among the projected widths L3, L4, and L5.

[0046] In the case of a rectangle, it is not desirable for the short side length L3 to be extremely smaller than the long side length L4. From this perspective, the maximum value L4 of the two or more different projection widths is set to 3 times, 2.5 times, 2 times, or 1.5 times or less of the minimum value L3 of the two or more different projection widths. The same can be considered for shapes other than rectangles.

[0047] Note that the short side length L3 of the rectangle shown in Fig. 8 is greater than the side length L1 of the square shown in Fig. 5(c). Similarly, the diagonal length L5 is greater than the diagonal length L2 of the square shown in Fig. 5(c). The cross-sectional area of ​​the rectangle in Fig. 8 is greater than the cross-sectional area of ​​the square in Fig. 5(c), further increasing the rigidity of the middle portion 63 of the tie bar 25.

[0048] Again, the cross-sectional shape of the intermediate portion 63 of the tie bar 25 can be a square, pentagon, hexagon, octagon, etc., and can be determined by a person skilled in the art. Just to be clear, the corners of the square, rectangle, or other polygon may or may not be chamfered. The chamfer may be a flat or curved surface. The intermediate portion 63 of the tie bar 25 shown in FIG. 3 has a chamfered square cross section. The chamfer is not shown in FIG. 5(c).

[0049] In the tie bar 25, the portion having a cross-sectional area larger than the area of ​​the above-mentioned virtual circle (i.e., a virtual circle having a diameter equal to the minimum projected width L1) is not limited to the entire length of the intermediate portion 63 of the tie bar 25, but may be a part of the intermediate portion 63 of the tie bar 25. Referring to FIG. 9 for explaining this characteristic point, in the intermediate portion 63 of the tie bar 25, wide portions 63m having a width L1 and narrow portions 63n having a width L9 are alternately provided in the axial direction of the tie bar 25 when viewed from the top side. In this way, various modifications of the intermediate portion 63 of the tie bar 25 are possible, and for example, only one of the multiple wide portions 63m shown in FIG. 9 may be left, and all the rest may be replaced with the narrow portions 63n. In this way, it is sufficient that at least a part of the intermediate portion 63 of the tie bar 25 has a cross-sectional area larger than the area of ​​the above-mentioned virtual circle (i.e., a virtual circle having a diameter equal to the minimum projected width L1), and it is not necessary for the tie bar 25 to have the cross-sectional area over its entire length.

[0050] Of course, it is preferable for the stiffness of the tie bar 25 to be increased if the portion of the cross-sectional area is provided longer in the intermediate portion 63. From this viewpoint, in some cases, when the toggle mechanism 23 is in the shortest contracted state (for example, the mold open state of the mold clamping device), the intermediate portion 63 of the tie bar 25 has a cross-sectional area larger than the area of ​​the above-mentioned imaginary circle (i.e., an imaginary circle having a diameter equal to the minimum projected width L1) at least in the entire length between the movable platen 22 (positioned corresponding to the state of the toggle mechanism 23) and the toggle support 24. In other cases, when the toggle mechanism 23 is in the longest extended state (for example, the mold clamping state of the mold clamping device), the intermediate portion 63 of the tie bar 25 has a cross-sectional area larger than the area of ​​the above-mentioned imaginary circle (i.e., an imaginary circle having a diameter equal to the minimum projected width L1) at least in the entire length between the movable platen 22 (positioned corresponding to the state of the toggle mechanism 23) and the toggle support 24.

[0051] As can be seen from the above description, the rigidity of the tie bars 25 is increased by increasing the cross-sectional area of ​​the tie bars 25, and in short, the deformation or distortion of the tie bars 25 that may occur when the movable platen is driven in is reduced. As a result, the amount of drive of the movable platen can be reduced, allowing the adoption of a corresponding drive system (e.g., a mold clamping motor and / or a ball screw) or promoting a reduction in power consumption of the mold clamping device. A reduction in the amount of drive means a reduction in the motor load, and therefore allows the adoption of a motor with a lower rated output. Also, a shorter ball screw is allowed to be adopted.

[0052] It is not essential that the first insertion end 61 have a different cross-sectional shape than the intermediate portion 63. Likewise, it is not essential that the second insertion end 62 have a different cross-sectional shape than the intermediate portion 63. It is also possible for the tie bar 25 to have a square cross-section as shown in Figure 5(c), a rectangular cross-section as shown in Figure 8, or another polygonal shape having four or more sides over the entire length of the first insertion end 61, the second insertion end 62, and the intermediate portion 63.

[0053] In FIG. 10, the required thrust amount when the middle part of the tie bar 25 has a circular cross-sectional shape with a diameter R1 can be understood from the solid line, and the required thrust amount when the middle part of the tie bar 25 has a square cross-sectional shape as shown in FIG. 5(c) can be understood from the dotted line. In this way, it is expected that the thrust amount of the movable platen 22 can be halved by increasing the cross-sectional shape of the tie bar 25. As an example, the target value of the mold clamping force is 1000 kN. Similar to the thrust amount, the thrust force of the crosshead 23a (shown by the dashed line in FIG. 10) is also reduced. The maximum thrust force of the crosshead 23a is reduced from 30 kN to around 18 kN.

[0054] The toggle mechanism 23 shown in FIG. 1 has two toggle mechanisms (which may be called sub-toggle mechanisms), one on the top side and one on the bottom side, provided on a common crosshead 23a, but one of the mechanisms can be omitted to form a single toggle mechanism.

[0055] The mold clamping device is not limited to a horizontal type in which the mold is opened and closed in a horizontal direction perpendicular to the top-bottom direction, but can also be used for a vertical type in which the mold is opened and closed in the top-bottom direction. [Explanation of symbols]

[0056] 2: Mold clamping device 21: Fixed platen 22: Movable platen 23: Toggle mechanism 24: Toggle Support 25: Tie bar 29: Linear guide 61: First insertion end 62: Second insertion end 63: Middle section

Claims

1. A mold clamping device comprising a fixed platen, a movable platen, a toggle mechanism, and a toggle support, the toggle support and the movable platen being connected to each other via the toggle mechanism, and the movable platen being movable forward and backward relative to the fixed platen based on an operation of the toggle mechanism, four solid tie bars extending between the fixed platen and the toggle support and connecting the fixed platen and the toggle support to each other; Each of the four tie bars is (i) is shaped with a rectangular cross section to have two or more distinct projected widths perpendicular to the axial direction of the tie bar when illuminated with collimated light perpendicular to the axial direction and propagating in different directions relative to each other; and (ii) having a cross-sectional area larger than an area of ​​an imaginary circle having a diameter equal to the smallest projected width among the two or more different projected widths at least in a portion between the fixed platen and the toggle support; A mold clamping device, wherein of the four sides of the quadrangle that is the cross-sectional shape of the tie bar, a first opposing side is arranged along the top-bottom direction, and a second opposing side is arranged along the horizontal direction.

2. 2. The mold clamping apparatus according to claim 1, wherein each of the four tie bars has a square cross-section that is chamfered or not chamfered at least in a portion between the fixed platen and the toggle support.

3. 3. The mold clamping apparatus according to claim 1, wherein each of the four tie bars has a square cross section, which may or may not be chamfered, at least in a portion between the fixed platen and the toggle support.

4. 4. The mold clamping device according to claim 1, wherein the cross-sectional area is smaller than an area of ​​an imaginary circle having a diameter equal to a maximum projected width among the two or more different projected widths.

5. 5. The mold clamping device according to claim 1, wherein a maximum value of the two or more different projection widths is three times or less than a minimum value of the two or more different projection widths.

6. The mold clamping device according to any one of claims 1 to 5, characterized in that each of the four tie bars has an insertion end that is inserted into a hole provided in the fixed platen or the toggle support, and the minimum projected width is substantially equal to a diameter of the insertion end in a cross section perpendicular to the axial direction of the tie bar.

7. The mold clamping device according to any one of claims 1 to 6, characterized in that each of the four tie bars has an insertion end portion that is inserted into a hole provided in the fixed platen or the toggle support, and the maximum projected width among the two or more different projected widths is 1.2 times or more and 3 times or less of a diameter of the insertion end portion in a cross section perpendicular to the axial direction of the tie bar.

8. 8. The mold clamping device according to claim 6, wherein the insertion end portion is a cylindrical portion having at least a partial helical thread formed therein.

9. The mold clamping device according to any one of claims 1 to 8, characterized in that each of the four tie bars has a cross-sectional area larger than the area of ​​an imaginary circle having a diameter equal to the minimum projected width over the entire length of its intermediate portion extending between the fixed platen and an insertion end portion inserted into each hole of the toggle support.

10. The mold clamping device according to any one of claims 1 to 9, further comprising a linear guide, the movable platen being movably supported by the linear guide and not mechanically coupled to the tie bars.

11. A clamping device as described in any one of claims 1 to 5, wherein each of the four tie bars has a first insertion end that is inserted into a hole provided in the toggle support, a second insertion end that is inserted into a hole provided in the fixed platen, and an intermediate portion extending between the first insertion end and the second insertion end, wherein the first and second insertion ends are each cylindrical portions, and the intermediate portion is shaped to have the rectangular cross section.

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