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

Abstract

Provided is a mold clamping device with which it is easy to attach and detach a strain sensor.　An open part 21 in which a peripheral surface of a tie bar 12 is exposed is provided in the part of a fixed board 16 through which the tie bar 12 penetrates, and a strain sensor 23 is attached to the peripheral surface of the tie bar 12 exposed in the open part 21.

Description

Clamping device and injection molding device including the same

[0001] The present invention relates to a clamping device and an injection molding device including the clamping device.

[0002] An injection molding device for molding a synthetic resin molded product mainly includes a bed, an injection device disposed on the bed, and a clamping device also disposed on the bed, as shown in Patent Document 1. The clamping device clamps the mold, and a synthetic resin material is injected into the mold from the injection device to obtain a molded product.

[0003] The clamping device includes a fixed platen fixed to the bed, a pressure receiving platen disposed on the bed, four tie bars extending between the fixed platen and the pressure receiving platen, a movable platen movably attached to the tie bars, a toggle link extending between the movable platen and the pressure receiving platen to move the movable platen, and toggle driving means for driving the toggle link.

[0004] The clamping device is configured to movably attach the movable platen to the tie bars, expand and contract the toggle link with the toggle driving means, and open and close the mold attached to the movable platen and the mold attached to the fixed platen.

[0005] In an injection molding device, when the toggle driving means of the clamping device is driven to clamp the mold, a tension due to the reaction force of the clamping force is generated in each tie bar. Due to the tension, each tie bar is elastically deformed and a strain occurs in the tie bar. The injection molding device acquires the strain of the tie bar from a strain sensor, and controls the clamping force by a control unit based on the acquisition result so that a uniform clamping force is applied to the mold, thereby preventing the molding accuracy of the molded product from deteriorating.

[0006] As a method for measuring the strain generated 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 generated in the tie bar is measured by the strain sensor.

[0007] Japanese Patent No. 6329517 JP-A-2008-114513 JP-A-11-240055

[0008] However, conventional mold clamping devices have a configuration in which strain sensors are attached to the tie bars between the fixed platen and the movable platen. This means that the strain sensors protrude from the mold mounting surface of the fixed platen, and there is a problem in that the strain sensors must be installed so as not to interfere with the mold.

[0009] Therefore, in view of the above circumstances, the present invention aims to provide a mold clamping device that can be mounted so as not to interfere with the mold.

[0010] The present invention relates to a mold clamping device comprising a fixed platen, a pressure receiving platen, a tie bar provided between the fixed platen and the pressure receiving platen, and a movable platen movably attached to the tie bar, wherein the movable platen and the fixed platen clamp a mold, the fixed platen having a through hole through which the tie bar passes, an open portion provided in a part of the fixed platen through which the tie bar passes, in which the circumferential surface of the tie bar is exposed, and a strain sensor attached to the circumferential surface of the tie bar exposed in the open portion.

[0011] Furthermore, the present invention is characterized in that the fixed platen is formed from a mold side platen portion and an injection device side platen portion, and the opening portion is provided between the through hole of the mold side platen portion and the through hole of the injection device side platen portion.

[0012] Furthermore, the present invention is characterized by the provision of a cover that can be opened and closed to cover the aforementioned opening.

[0013] Furthermore, the present invention is an injection molding apparatus characterized by comprising the aforementioned mold clamping device.

[0014] According to the present invention, the fixed platen of the clamping device has through holes through which tie bars pass, and an open portion is provided in the part through which the tie bars pass, exposing the circumferential surface of the tie bars, and a strain sensor is attached to the open portion, so that the strain sensor is not located between the fixed platen and the movable platen.

[0015] This prevents the strain sensor from protruding towards the mold mounting surface, allowing it to be installed without interfering with the mold. Therefore, the strain sensor can be easily attached to and detached from the tie bar.

[0016] Furthermore, according to the present invention, the fixed platen is formed from a mold side platen and an injection device side platen, and the opening is provided between the through hole of the mold side platen and the through hole of the injection device side platen, so the opening can be easily formed.

[0017] Furthermore, according to the present invention, since a cover is attached that can be opened and closed over the opening, the strain sensor can be prevented from being unintentionally contacted by covering the opening with the cover as needed.

[0018] Furthermore, since the injection molding apparatus is equipped with the mold clamping device, the strain sensor can be attached without interfering with the mold, and the strain sensor can be easily attached and detached.

[0019] This is a side view of the injection molding apparatus as seen from the side. This is an explanatory diagram showing an enlarged view of the fixed platen 10. This is an explanatory diagram showing an enlarged view of the fixed platen 10. This is a diagram showing the fixed platen, where (a) is an explanatory diagram showing the fixed platen as seen from the mold mounting surface side, and (b) is an explanatory diagram showing the fixed platen as seen from the side. This is an explanatory diagram showing the fixed platen as seen from the side according to another embodiment. This is a diagram illustrating the fixed platen according to another embodiment. This is a diagram illustrating the fixed platen according to another embodiment, where (a) shows the mold side platen as seen from the mold side, and (b) shows the injection device side platen as seen from the mold side platen side. This is an explanatory diagram showing the open part covered with a cover.

[0020] Figure 1 is a side view of the injection molding apparatus 1 according to the present invention. The injection molding apparatus 1 comprises a bed 2, an injection device 3 positioned on the upper surface of the bed 2, and a clamping device 4 positioned on the upper surface of the bed 2.

[0021] The injection device 3 comprises a heating cylinder 7 having a nozzle 5 at its tip and a screw 6 built inside, a hopper 8 that supplies resin material into the heating cylinder 7, and a rotary drive means 9 that rotates the screw 6 and moves it back and forth in the forward and backward directions, injecting resin material from the nozzle 5 each time the screw 6 moves forward.

[0022] The clamping device 4 comprises a fixed platen 10 fixed to the bed 2, a pressure receiving platen 11, a tie bar 12 positioned 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 movable in the longitudinal direction of the tie bar 12, a toggle link 14 spanning between the pressure receiving platen 11 and the movable platen 13, and a toggle driving means 15 for driving the toggle link 14.

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

[0024] The tie bar 12 consists of four rod-shaped bars, with one pair provided on the upper side and one pair on the lower side, and is stretched between the fixing plate 10 and the pressure receiving plate 11.

[0025] A fixed mold 16 is attached to the fixed platen 10. A movable mold 17 is attached to the movable platen 13. The fixed mold 16 and the movable mold 17 form a mold 18. The mold 18 is clamped when the movable mold 17 is pressed against the fixed mold 16 by the operation of the mold clamping device 4, and the mold is opened when the movable mold 17 is separated from the fixed mold 16.

[0026] Figure 2A is an enlarged explanatory diagram showing the fixed platen 10. A through hole 19 is opened in the corner of the fixed platen 10, penetrating the clamping device 4 in the longitudinal direction. One end of the tie bar 12 is inserted through the through hole 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 locks into the fixing plate 10, thereby fixing the end of the tie bar 12 on the injection device 3 side to the fixing plate 10.

[0028] An opening 21 is provided in a portion of the fixed plate 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 that corresponds 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 section 21. Each sensor unit 24 is attached to the circumferential surface of the tie bar 12 by wrapping a band 25 around it in the circumferential direction, so that each sensor unit 24 is in close contact with the circumferential surface.

[0030] Figure 2B is an explanatory diagram showing an enlarged view of the fixed platen 10. As a modification 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 12, with a smaller diameter than the portion located inside the through hole 19 of the tie bar 12 or the portion extending 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 consists of 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] In addition to using the band 25, the strain sensor 23 may be attached to the tie bar 12 by, for example, using a magnet, a bolt, or by fixing it in place with an adhesive.

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

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

[0035] Figures 2A and 2B show only one upper corner of the fixed platen 10. In the mold clamping device 4 of this embodiment, when viewed from the mold mounting surface side, through holes 19, openings 21, tie bars 12, constricted portions 22, and strain sensors 23 are arranged at both upper and lower corners, respectively, and the amount of strain of the tie bars 12 is measured by the strain sensors 23 located in each opening 21.

[0036] In any position, the position of the strain sensor 23 corresponds to the opening 21, making it easy to check the mounting status of the strain sensor 23, and the strain sensor 23 can be attached, detached, or maintained at the opening 21.

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

[0038] The fixing plate 10 is formed in the shape of a rectangular plate, and through holes 19 extending through in the thickness direction are formed at both upper corners of the fixing plate 10. Through holes 19 extending through in the thickness direction are also formed at both lower corners of the fixing plate 10. Tie bars 12 are inserted through each of the through holes 19. Legs 26 are integrally provided below the fixing plate 10, and the legs 26 are fixed to the bed 2.

[0039] Figure 3(b) shows one side of the fixing plate 10, but the other side is formed similarly. As shown in Figure 3(b), an opening 21 is provided in a portion through which the tie bar 12 passes. The constricted portion 22 of the tie bar 12 is provided to correspond to the portion of the opening 21 (see Figure 2B).

[0040] In this embodiment, the fixed platen 10 is manufactured by making a recess in the portion corresponding to the opening 21, thereby forming the opening 21. However, the present invention is not limited to the above-described embodiment for manufacturing the fixed platen 10 having the opening 21.

[0041] Figure 4 is an explanatory diagram showing a fixed platen 10A according to another embodiment, viewed from the side. In the fixed platen 10A, an open portion 21 is formed by cutting a portion through which the tie bar 12 passes at both upper and lower corners.

[0042] Another embodiment of the fixed platen 10 is the fixed platen 10B. Figure 5 is a diagram illustrating the fixed platen 10B. Figure 6 is a diagram illustrating the fixed platen 10B, where Figure 6(a) shows the mold side platen portion 27 as seen from the mold side, and Figure 6(b) shows the injection device side platen portion 28 as seen from the mold side platen portion 27 side. The fixed platen 10B is formed from the mold side platen portion 27 and the injection device side platen portion 28.

[0043] The fixed platen 10B is formed by overlapping the mold-side platen portion 27 and the injection device-side platen portion 28 and joining the mold-side platen portion 27 and the injection device-side platen portion 28. The open portion 21 is defined by overlapping the mold-side platen portion 27 and the injection device-side platen portion 28.

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

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

[0046] FIG. 7 is a view 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 always open, and a cover 30 capable of opening and closing the open portion 21 may be provided. The cover 30 is provided so as to be able to open and close the open portion 21, and when an operator checks the mounting state of the strain sensor 23 or performs the attachment / detachment operation of the strain sensor 23 itself, the cover 30 can be opened to access the open portion 21.

[0047] By covering the open portion 21 with the cover 30, it is possible to prevent an accident of inadvertently contacting the strain sensor 23 and improve the aesthetic feeling.

[0048] The cover 30 may be configured to be detachable from the fixed platen 10 using a magnet, and may also be attached to the fixed platen 10 using a hinge member so as to be able to open and close the open portion 21. Further, it is also possible to attach the cover 30 so as to be slidable along the frontage direction of the open portion 21, and the attachment method of the cover 30 is not limited.

[0049] In the above embodiment, the tie bar 12 was described as having a constricted portion 22. However, the present invention is not limited to the tie bar 12 having a constricted portion 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, making maintenance of the strain sensor 23 easier. Furthermore, since the strain sensor 23 is provided in the open section 21, the mold thickness adjustment range is not restricted by the installation of the strain sensor 23. In addition, since the strain sensor 23 is attached to the tie bar 12 exposed in the open section 21, it is possible to suppress an increase in the size of the mold clamping device.

[0051] 1…Injection molding machine 2…Bed 4…Clamping device 10…Fixed platen 11…Pressure receiving platen 12…Tie bar 13…Movable platen 18…Mold 19…Through hole 21…Open section 22…Neck section 23…Strain sensor 24…Sensor section 27…Mold side platen section 28…Injection machine side platen section 30…Cover

Claims

1. A mold clamping device comprising a fixed platen, a pressure receiving platen, a tie bar provided between the fixed platen and the pressure receiving platen, and a movable platen movably attached to the tie bar, wherein the movable platen and the fixed platen clamp a mold, the fixed platen having a through hole through which the tie bar passes, an open portion provided in a part of the fixed platen through which the tie bar passes, in which the circumferential surface of the tie bar is exposed, and a strain sensor attached to the circumferential surface of the tie bar exposed in the open portion.

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

3. The clamping device according to claim 1 or 2, which is provided with a cover that can be opened and closed to cover the opening.

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

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