Mold clamping device and injection molding device equipped with the mold clamping device

Abstract

To provide a mold clamping device in which a strain sensor can be easily attached and detached. [Solution] An opening (21) is provided in a part of the fixed plate (16) through which the tie bar (12) passes, exposing the circumferential surface of the tie bar (12), and a strain sensor (23) is attached to the circumferential surface of the tie bar (12) exposed in the opening (21).

Description

[Technical Field]

[0001] The present invention relates to a mold clamping device and an injection molding apparatus equipped with the mold clamping device. [Background technology]

[0002] As shown in Patent Document 1, an injection molding apparatus for molding synthetic resin molded products has as its main components a bed, an injection unit placed on the bed, and a mold clamping unit also placed on the bed. The mold is clamped by the mold clamping unit, and a synthetic resin material is injected into the mold from the injection unit to obtain a molded product.

[0003] The mold clamping device comprises a fixed platen fixed to the bed, a pressure-receiving platen placed on the bed, four tie bars stretched between the fixed platen and the pressure-receiving platen, a movable platen movably attached to the tie bars, a toggle link stretched between the movable platen and the pressure-receiving platen to move the movable platen, and a toggle drive means for driving the toggle link.

[0004] The mold clamping device is configured such that a movable platen is movably attached to the tie bars, and the toggle link is extended and contracted by a toggle drive means, thereby enabling the mold attached to the movable platen and the mold attached to the fixed platen to be opened and closed.

[0005] In an injection molding machine, when the toggle drive means of the mold clamping device is driven to clamp the mold, tension is generated in each tie bar due to the reaction force of the mold clamping force. This tension causes each tie bar to elastically deform, resulting in distortion. The injection molding machine acquires the distortion of the tie bars from a strain sensor and controls the mold clamping force using a control unit based on the acquired data, thereby applying a uniform mold clamping force to the mold and preventing a decrease in the molding precision of the molded product.

[0006] As a method for measuring the strain occurring in the tie bar, for example, as shown in Patent Documents 2 and 3, a strain sensor is provided on the tie bar between the fixed platen and the movable platen, and the strain occurring in the tie bar is measured by the strain sensor. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 6329517 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-114513 [Patent Document 3] Japanese Patent Application Publication No. 11-240055 Summary of the Invention [Problem to be solved by the invention]

[0008] However, in conventional mold clamping devices, the strain sensor is attached to the tie bar between the fixed platen and the movable platen, which means that the strain sensor protrudes toward the mold mounting surface of the fixed platen, creating the problem that the strain sensor must be installed so as not to interfere with the mold.

[0009] In view of the above circumstances, an object of the present invention is to provide a mold clamping device in which a strain sensor can be attached without interfering with the mold. [Means for solving the problem]

[0010] The present invention provides a mold clamping device that includes a fixed platen, a pressure-receiving platen, tie bars provided between the fixed platen and the pressure-receiving platen, and a movable platen movably attached to the tie bars, and that clamps a mold between the movable platen and the fixed platen, the fixed platen has through holes through which the tie bars pass, an opening portion through which the tie bar passes is provided in the fixed platen, and a peripheral surface of the tie bar is exposed; The mold clamping device is characterized in that a strain sensor is attached to the circumferential surface of the tie bar exposed at the open portion.

[0011] Further, in the present invention, the fixed platen is formed of a mold side platen portion and an injection unit side platen portion, The opening is provided between the through hole of the mold side platen and the through hole of the injection unit side platen.

[0012] Furthermore, the present invention is characterized in that a cover is provided to cover the open portion in an openable and closable manner.

[0013] The present invention also provides an injection molding apparatus comprising the above-described mold clamping device. [Effects of the Invention]

[0014] According to the present invention, the fixed platen of the mold clamping device has a through hole through which the tie bar passes, and an opening is provided in the part through which the tie bar passes, exposing the circumferential surface of the tie bar, and a strain sensor is attached to the opening, so that the strain sensor is not located between the fixed platen and the movable platen.

[0015] This prevents the strain sensor from protruding onto the mold mounting surface side, and allows the strain sensor to be mounted without interfering with the mold. Therefore, the strain sensor can be easily attached and detached to the tie bar.

[0016] According to the present invention, the fixed platen is formed of a mold side platen portion and an injection unit side platen portion, Since the opening is provided between the through hole of the mold side platen and the through hole of the injection unit side platen, the opening can be easily formed.

[0017] Furthermore, according to the present invention, a cover that can be opened and closed is attached to cover the open portion, so that by covering the open portion with the cover as needed, it is possible to prevent undesired contact with the strain sensor.

[0018] Furthermore, the present invention provides an injection molding apparatus that is equipped with the above-mentioned mold clamping device, and therefore can install a strain sensor without interfering with the mold, and can easily attach and detach the strain sensor. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 2 is a side view of the injection molding apparatus. [Figure 2A] FIG. 2 is an explanatory diagram showing an enlarged view of the fixed platen 10 portion. [Figure 2B] FIG. 2 is an explanatory diagram showing an enlarged view of the fixed platen 10 portion. [Figure 3] 1A and 1B are diagrams showing a fixed platen, where FIG. 1A is an explanatory diagram showing the fixed platen as viewed from the mold mounting surface side, and FIG. 1B is an explanatory diagram showing the fixed platen as viewed from the side. [Figure 4] FIG. 10 is an explanatory view showing a stationary platen according to another embodiment as viewed from the side. [Figure 5] 10A and 10B are diagrams illustrating a fixed platen according to another embodiment. [Figure 6] 10A and 10B are diagrams illustrating a fixed platen according to another embodiment, in which FIG. 10A shows a mold-side platen portion as viewed from the mold side, and FIG. 10B shows an injection unit-side platen portion as viewed from the mold-side platen portion side. [Figure 7] FIG. 10 is an explanatory diagram showing a state in which the open portion is covered with a cover. DETAILED DESCRIPTION OF THE INVENTION

[0020] 1 is a side view of an injection molding apparatus 1 according to the present invention. The injection molding apparatus 1 includes a bed 2, an injection unit 3 disposed on the upper surface of the bed 2, and a mold clamping unit 4 disposed on the upper surface of the bed 2.

[0021] The injection device 3 is equipped with a heating barrel 7 having a nozzle 5 at the tip and a screw 6 built in, a hopper 8 that supplies resin material to the inside of the heating barrel 7, and a rotation drive means 9 that rotates the screw 6 and moves it back and forth, and the resin material is injected from the nozzle 5 each time the screw 6 moves forward.

[0022] The mold clamping device 4 is composed of a fixed platen 10 fixed to the bed 2, a pressure-receiving platen 11, a tie bar 12 arranged between the fixed platen 10 and the pressure-receiving platen 11, a movable platen 13 attached to the tie bar 12 so as to be freely movable in the longitudinal direction of the tie bar 12, a toggle link 14 stretched between the pressure-receiving platen 11 and the movable platen 13, and a toggle drive means 15 that drives the toggle link 14.

[0023] The fixed platen 10 is fixed to the bed 2. The pressure-receiving platen 11 is disposed on the upper surface of the bed 2.

[0024] The tie bars 12 are made up of four rod-shaped bars, one pair of which is provided on the upper side and one pair of which is provided on the lower side, and are stretched between the fixed platen 10 and the pressure-receiving platen 11.

[0025] A fixed mold 16 is attached to the fixed platen 10. A movable mold 17 is attached to the movable platen 13. A mold 18 is formed by the fixed mold 16 and the movable mold 17. The mold 18 is clamped by pressing the movable mold 17 against the fixed mold 16 through the operation of the mold clamping device 4, and is opened by moving the movable mold 17 away from the fixed mold 16.

[0026] 2A is an explanatory view showing an enlarged view of the fixed platen 10. At the corners of the fixed platen 10, through-holes 19 are opened, penetrating in the longitudinal direction of the mold clamping unit 4. One end of a tie bar 12 is inserted into the through-holes 19.

[0027] A fixing nut 20 is screwed onto the end of the tie bar 12 on the injection device 3 side, and the fixing nut 20 is engaged with the fixed platen 10, thereby fixing the end of the tie bar 12 on the injection device 3 side to the fixed platen 10.

[0028] An opening 21 is provided in a portion of the fixed platen 10 through which the tie bar 12 passes. The circumferential surface of the tie bar 12 is exposed in the opening 21. A strain sensor 23 is attached to the circumferential surface of the tie bar 12 at a portion corresponding to the opening 21.

[0029] The strain sensor 23 has multiple sensor units 24 arranged at intervals on the circumferential surface of the portion corresponding to the open portion 21. Each sensor unit 24 is attached by wrapping a band 25 around the circumferential surface of the tie bar 12 so that each sensor unit 24 is in close contact with the circumferential surface.

[0030] 2B is an explanatory diagram showing an enlarged view of the fixed platen 10. As a modified example of the tie bar 12, an example can be given in which a constricted portion 22 is formed in the portion of the tie bar 12 corresponding to the open portion 12a of the tie bar 12, the constricted portion 22 having a smaller diameter than the portion located inside the through hole 19 of the tie bar 12 and the portion spanning between the fixed platen 10 and the pressure-receiving platen 11. The inner diameter of the through hole 19 is larger than the outer diameter of the tie bar 12.

[0031] In this case, a strain sensor 23 is attached to the circumferential surface of the constricted portion 22. The strain sensor 23 has multiple sensor units 24 arranged at intervals on the circumferential surface of the constricted portion 22. Each sensor unit 24 is attached by wrapping a band 25 around the circumferential direction of the constricted portion 22 so that each sensor unit 24 is in close contact with the circumferential surface.

[0032] The strain sensor 23 may be attached using the band 25, or may be fixed to the tie bar 12 with a magnet, a bolt, or an adhesive or the like.

[0033] The strain sensor 23 outputs the measured strain amount to a control unit (not shown). The injection molding device controls the mold clamping force based on the output information so that an appropriate mold clamping force acts on the mold 18 during mold clamping.

[0034] As described above, the position of the strain sensor 23 corresponds to the open portion 21, so that the strain sensor 23 can be attached / detached and maintained at the open portion 21.

[0035] 2A and 2B show only one upper corner of the fixed platen 10, but in the clamping device 4 of this embodiment, when viewed from the mold mounting surface side, through holes 19, open portions 21, tie bars 12, constricted portions 22, and strain sensors 23 are arranged at each of the upper and lower corners, and the strain sensors 23 arranged at each open portion 21 measure the amount of strain in the tie bars 12.

[0036] In either position, the position of the strain sensor 23 corresponds to the opening 21, making it easy to check the installation state of the strain sensor 23, and the strain sensor 23 can be attached, detached, and maintained at the opening 21.

[0037] Figure 3 shows the fixed platen 10, where Figure 3(a) is an explanatory diagram showing the fixed platen 10 as viewed from the mold mounting surface side, and Figure 3(b) is an explanatory diagram showing the fixed platen 10 as viewed from the side.

[0038] The fixed plate 10 is formed in a square plate shape, and through-holes 19 are formed in both upper corners thereof, penetrating in the thickness direction. Through-holes 19 are also formed in both lower corners of the fixed plate 10, penetrating in the thickness direction. Tie bars 12 are inserted into each of the through-holes 19. Legs 26 are integrally formed on the lower part of the fixed plate 10, and the legs 26 are fixed to the bed 2.

[0039] Fig. 3(b) shows one side of the fixed platen 10, but the other side is formed in the same way. As shown in Fig. 3(b), an opening 21 is provided in a portion through which the tie bar 12 passes. A narrowed portion 22 of the tie bar 12 is provided so as to correspond to the opening 21 (see Fig. 2B).

[0040] In this embodiment, the stationary platen 10 is manufactured with a recess in the portion corresponding to the open portion 21, thereby forming the open portion 21, but the method of manufacturing the stationary platen 10 having the open portion 21 in the present invention is not limited to the above-described embodiment.

[0041] 4 is an explanatory side view of a fixed platen 10A according to another embodiment. In the fixed platen 10A, openings 21 are formed by cutting portions through which tie bars 12 pass at both upper and lower corners.

[0042] Another embodiment of the fixed platen 10 is a fixed platen 10B. Fig. 5 is a diagram illustrating the fixed platen 10B. Fig. 6 is a diagram illustrating the fixed platen 10B, with Fig. 6(a) showing the mold-side platen portion 27 as viewed from the mold side, and Fig. 6(b) showing the injection unit-side platen portion 28 as viewed from the mold-side platen portion 27 side. The fixed platen 10B is formed from the mold-side platen portion 27 and the injection unit-side platen portion 28.

[0043] The fixed platen 10B is formed by overlapping a mold-side platen portion 27 and an injection unit-side platen portion 28 and joining the mold-side platen portion 27 and the injection unit-side platen portion 28. The overlapping of the mold-side platen portion 27 and the injection unit-side platen portion 28 defines an open section 21.

[0044] The injection device side platen portion 28 has concave portions 29 formed in the thickness direction of the fixed platen 10B at the upper and lower corners facing the mold side platen portion 27, and through holes 19 are formed in the upper and lower corners corresponding to the concave portions 29.

[0045] When the mold side platen 27 and the injection unit side platen 28 are overlapped and joined, concave portions 29 are located between each corner of the mold side platen 27 and each corner of the injection unit side platen 28, and an open portion 21 consisting of the concave portions 29 is formed between the through hole 19 of the mold side platen 27 and the through hole 19 of the injection unit side platen 28.

[0046] 7 is a diagram showing a state in which the open portion 21 of the fixed platen 10 is covered with a cover 30. The open portion 21 does not necessarily have to be open all the time, and a cover 30 that can open and close the open portion 21 may be provided. The cover 30 is provided so that the open portion 21 can be opened and closed, and an operator can access the open portion 21 by opening the cover 30 when checking the installation status of the strain sensor 23 or when performing work to attach or detach the strain sensor 23 itself.

[0047] By covering the open portion 21 with the cover 30, accidents such as accidentally touching the strain sensor 23 can be prevented and aesthetics can be improved.

[0048] The cover 30 may be configured to be detachable from the fixed platen 10 using a magnet, or may be attached to the fixed platen 10 using a hinge member so that it can openably and closably cover the opening 21. The cover 30 may also be attached so that it can slide along the width direction of the opening 21, and the method for attaching the cover 30 is not limited.

[0049] In the above embodiment, the tie bar 12 has been described as having a constricted portion 22, but the present invention is not limited to tie bars 12 having constricted portions 22, and the present invention can be implemented even if the tie bar 12 does not have a constricted portion 22.

[0050] According to the embodiment of the present invention described above, the strain sensor 23 attached to the tie bar 12 can be easily accessed, facilitating maintenance of the strain sensor 23. Furthermore, since the strain sensor 23 is provided in the open portion 21, the mold thickness adjustment range is not limited by attaching the strain sensor 23. Furthermore, since the strain sensor 23 is attached to the tie bar 12 exposed in the open portion 21, it is possible to prevent the mold clamping device from becoming larger. [Explanation of symbols]

[0051] 1...Injection molding equipment 2. Bed 4…Mold clamping device 10…Fixed plate 11...Pressure plate 12...Tie bar 13…Movable plate 18...Mold 19...Through hole 21...Open part 22...Constriction 23...Strain sensor 24...Sensor section 27…Mold side panel part 28…Injection device side panel part 30...Cover

Claims

1. A mold clamping device comprising a fixed platen, a pressure-receiving platen, tie bars provided between the fixed platen and the pressure-receiving platen, and a movable platen movably attached to the tie bars, wherein the movable platen and the fixed platen clamp a mold, the fixed platen has through holes through which the tie bars pass, an opening portion through which the tie bar passes is provided in the fixed platen, and a peripheral surface of the tie bar is exposed; A mold clamping device characterized in that a strain sensor is attached to the circumferential surface of the tie bar exposed at the open portion.

2. the fixed platen is formed of a mold side platen portion and an injection unit side platen portion, The mold clamping device according to claim 1 , wherein the opening is provided between the through hole of the mold side platen and the through hole of the injection device side platen.

3. The mold clamping device according to claim 1 or 2, further comprising a cover that covers the open portion in an openable and closable manner.

4. An injection molding apparatus comprising the mold clamping device of claim 1.

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