JPH04262848A - Die clamping device for injection molding - Google Patents

Abstract

PURPOSE:To eliminate any gap between a die and a platen at the time of clamping the dies. CONSTITUTION:To both the fixed platen 2 and the movable platen 6 or only to the fixed platen 2, a cylinder hole 2b opened to the die side is disposed. In this cylinder hole 2b, a ram cylinder 24 providing a ram 29 protruded from the cylinder hole 2b with fluid pressure is embedded. By working of the ram cylinder, surfaces of the dies 8, 9, which are apt to be bent at the time of clamping the dies, is made horizontal.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a mold clamping device for injection molding, which is attached to an injection molding device such as a die casting machine or an injection molding machine, and clamps the mold by moving a movable mold forward and backward relative to a fixed mold. .

0002

[Prior Art] Injection molding machines such as die casting machines and injection molding machines are classified into vertical clamping dies and horizontal clamping dies depending on the mold clamping direction. Die-casting machines are classified into two types: horizontal injection type and horizontal injection type. Among these, for example, a vertical injection type die-casting machine is generally configured as follows. That is, tie rods are erected at the four corners of a fixed platen fixed on a machine base, and a cylinder platen whose plane faces the plane of the fixed platen is supported at the upper end step of these tie rods. This cylinder platen is fixed with a nut screwed onto the threaded portion of the tie rod. In addition, a movable platen is slidably fitted into the holes of the four tie rods, and this movable platen is operated by a main ram that moves forward and backward using hydraulic pressure in a ram hole provided in the center of the cylinder platen. The ends are fixed. A fixed mold and a movable mold with their planes facing each other are mounted on opposing surfaces of the fixed platen and the movable platen, respectively. Furthermore, the plunger tip on the injection cylinder side, which is disposed below the fixed platen, is fitted into the injection sleeve supported on the injection cylinder side so as to be able to move forward and backward, and this injection sleeve is fitted into the fixed sleeve on the fixed platen side. They are removably joined, and the inner hole of the fixed sleeve is communicated with the cavity of the mold via the runner of the fixed mold.

With this structure, when the main ram moves forward hydraulically, the movable mold fixed to the movable platen, which is integrated with the main ram, descends and is clamped against the fixed mold, thereby preventing injection. When molten metal is injected into the sleeve and joined to the fixed sleeve, and the plunger tip is advanced by the hydraulic pressure of the injection cylinder, the molten metal in the injection sleeve passes through the fixed sleeve and the runner and is injected into the cavity of the mold. After the molten metal in the cavity has solidified, when the piston rod of the mold clamping cylinder is moved back, the movable mold is moved back and the mold is opened. By taking it out, one molding cycle is completed.

0004

[Problems to be Solved by the Invention] However, in such a conventional mold clamping device for injection molding, when the mold clamping cylinder lowers the movable platen and clamps the movable mold against the fixed mold for injection. , the fixed platen holding the fixed mold is pressed more strongly at the center than at the outer periphery, causing the fixed platen to curve, albeit slightly. In a large injection molding apparatus with a mold clamping force of 2,500 to 4,000 tons, the center of the upper surface of the fixed platen is curved so as to be deformed by 1 to 2 mm. At the same time, the fixed mold also curves, changing the shape of the mold cavity, making it impossible to obtain a molded product with accurate dimensions, and causing molten material to eject from the mating surfaces of the fixed mold and movable mold. . In particular, if small foreign matter adheres or scratches occur near the outer periphery of the mating surfaces of the mold, molten material may leak forcefully from the gaps in the mold, which is dangerous and may damage the molded product due to the solidification of the leaked molten material. There is a problem in that burrs are formed and work efficiency after product removal is reduced.

The present invention was made in view of the above points, and an object of the present invention is to provide a mold clamping device for injection molding that prevents the mold from curving even if the platen is slightly curved during mold clamping and injection. The purpose is

[0006]

[Means for Solving the Problems] In order to achieve such an object, the present invention provides a structure in which a hydraulic power source is connected near the center axis of a mold holding platen, which has tie rods provided at a plurality of corners. A cylinder hole is provided that opens to the mold side.
A fluid pressure cylinder equipped with a ram that protrudes from the cylinder hole using fluid pressure was embedded in this cylinder hole.

[0007]

[Operation] When the movable platen moves forward due to the fluid pressure of the mold clamping cylinder, the movable mold fixed to this movable platen moves forward and is clamped against the fixed mold, so molten metal is injected into the injection sleeve and fixed. Join to sleeve. When the mold clamping is finished and the injection sleeve is being poured,
When the ram of the fluid pressure cylinder embedded in the platen is moved forward, the reaction force causes the mold to move slightly away from the center of the platen, correcting the curvature of the mold due to mold clamping and straightening the mold. Therefore, even if the molten material is injected into the mold cavity after this, the molten material will not leak from between the fixed mold and the movable mold, and the mold cavity will not be deformed, so the shape will be maintained. , molded products with accurate dimensions can be obtained reliably and easily.

[0008]

[Example] This example shows an example in which the present invention is implemented in a vertical injection type die casting machine. Fig. 1 is a partially cutaway front view of a die casting machine in which the invention is implemented, and Fig. 2 is a plan view of a fixed platen. Figure 3 is a cross-sectional view taken along III-III in Figure 2;
FIG. 4 is a longitudinal sectional view of a hydraulic cylinder embedded in a fixed mold. In the figure, tie rods 3 are installed at the four corners of a fixed platen 2 fixed to a machine base 1, and cylinders whose planes face the planes of the fixed platen 2 are installed at the upper end portions of these tie rods 3. A platen 4 is supported, and the cylinder platen 4 is fixed with a nut 5 screwed onto a threaded portion of the tie rod 3. Further, a movable platen 6 is supported by the four tie rods 3 by slidably fitting holes into the movable platen 6.
The operating end of a main ram 7, which moves forward and backward by hydraulic pressure in a ram hole provided in the center of the cylinder platen 4, is fixed. A fixed mold 8 and a movable mold 9, whose planes face each other, are mounted on opposing surfaces of the fixed platen 2 and the movable platen 6, respectively. Furthermore, below the fixed platen, an injection cylinder 10 as a fluid pressure cylinder is swingably supported by a bracket 11 in the pit, and the action of a piston rod 12 that moves forward and backward by the hydraulic pressure of the injection cylinder 10. A plunger 14 is fixed to the end via a coupling 13.

Reference numeral 15 denotes a plurality of ram rods implanted on the end face of the injection cylinder 10, and these ram rods 15 are connected to the sleeve base 1 with an injection sleeve 16 integrally formed at the tip.
The plunger tip 14a at the tip of the plunger 14 is fitted into the inner hole of the injection sleeve 16 so as to be able to move forward and backward. On the other hand, a fixed sleeve 18 is fitted into the sleeve hole of the fixed mold 8, and by supplying oil to the bottom of the ram hole formed in the sleeve stand 17, the sleeve stand 17 is raised. The upper end surface of the injection sleeve 16 is configured to contact and be pressed against the lower end surface of the fixed sleeve 18. Also,
A cavity 19 is formed in the mating surfaces of the fixed mold 8 and the movable mold 9, and the cavity 19 on the fixed mold 8 side
is connected to the fixed sleeve 18 by a runner 20.

Further, the working end of a piston rod 22 that moves forward and backward with the hydraulic pressure of a tilting cylinder 21 pivotally supported on the machine base 1 side is pivotally attached to the injection cylinder 10, and the injection sleeve 16 is removed from the fixed sleeve 18. By moving the piston rod 22 back and forth in this state, the injection cylinder 1
The entire injection device 23 from 0 to the injection sleeve is configured to stand up and tilt between the solid line position and the chain line position in FIG. 1, and the molten metal is injected into the injection sleeve 16 in the tilted position. Note that the fixed platen 2 includes an injection device 21.
A U-shaped notch 2a is formed to allow the holder to tilt.

[0011] This apparatus is also provided with a device for correcting the curvature of the fixed mold 8 during mold clamping. That is, in the central axis of the stationary platen 2 on the fixed mold 8 side plane and in the vicinity of the central axis, for example, as shown in FIG. These cylinder holes 2b are provided at appropriate intervals, and are designated by the reference numeral 2 as a whole inside each of these cylinder holes 2b.
A ram cylinder indicated by 4 is buried there. As shown in FIG. 4, the ram cylinder 24 includes a cylindrical cylinder 25 that is fitted into the cylinder hole 2b and secured with bolts, and is fitted into the lower end of the inner hole of the cylinder 25 via an O-ring 26. An O-ring 28 is attached to the bottom plate 27 and the inner hole of the cylinder 25.
A ram 29 is fitted to the ram 29 so that the ram 29 can move forward and backward through the ram 29.
A recessed hole 29a is provided in the lower half of the ram 29 and communicated with a port 30 connected to a hydraulic power source (not shown) through an oil passage 31.
is provided. A spring shaft 32 having a flange is fixed to the bottom plate 27 with adhesive and housed in the recessed hole 29a. A compression coil spring 33 that biases the ram 29 toward the bottom plate 27 is interposed between them. By doing this, when oil is sent into the concave hole 29a from the port 30, the ram 29 protrudes from the upper end surface of the fixed mold 2 against the spring force of the compression coil spring 34, and the oil in the concave hole 29a is drained. Accordingly, the ram 29 is configured to be retracted from the upper end surface of the fixed mold 2 by the spring force of the compression coil spring 33. 35 is a labyrinth groove.

The operation of the die casting machine constructed as above will be explained. When the main ram 7 is lowered by hydraulic pressure from the state shown in FIG. 1, the movable platen 6 with the movable mold 9 mounted thereon is lowered and clamped against the fixed mold 8. Therefore, the injection sleeve 1 of the injection device 23 in the tilted position
The molten metal is injected into the injection device 2 by the tilting cylinder 21.
3, the injection sleeve 16 is raised by supplying oil to the tip side of the ram rod 15 and raising the sleeve stand 17.
is joined to the fixed sleeve 18, and the plunger tip 14a is advanced by the hydraulic pressure of the injection cylinder 10 to inject the molten metal in the injection sleeve 16 into the cavity 19. When the mold is clamped, as described above, the movable mold 9 is pressed against the fixed mold 8 with a large force, so that only the central part of the fixed mold 8 and the fixed platen 2 are pressed, so that the fixed platen 2 is curved so that the center of the upper surface is lowered, for example, by about 1 to 2 mm, and the fixed mold 8 is also curved.

In order to correct this curvature, in the present device, a plurality of ram cylinders 24 buried in the fixed platen 2 are installed when or before the injection sleeve 16 is being poured after mold clamping. Since oil of the same pressure is supplied to each concave hole 29a, all the rams 29 rise against the elastic force of the compression coil spring 34, and protrude from the upper surface of the fixed platen 2 by, for example, about 2 mm, with the tips of the rams 29 rising. The lower surface of the fixed mold 8 is pressed with a large force, and the surface of the fixed mold 8 that is about to curve becomes a horizontal plane, eliminating the gap between the fixed mold 8 and the movable mold 9. After this, the molten metal is poured into the cavity. 1
Even when injected into the mold 9, a molded product with accurate shape and dimensions can be reliably and easily obtained, and the molten metal will not leak from the mating surfaces of the molds 8 and 9.

[0014] If the mold clamping force and injection force are known,
Since the deformation dimensions of the central part of the axis of the fixed mold 8 and the fixed platen 2 can be known in advance by calculation or experiment, the amount of advance and pressure of the ram 29 at each position can be determined in advance according to these values. . Of course, by detecting the amount of deformation of the surface of the fixed mold 8 using, for example, ultrasonic waves, phototubes, piezoelectric elements, etc., and controlling the amount of advance of each ram 29 according to the detected amount, the amount of deformation of the surface of the fixed mold 8 can be detected. It is also possible to prevent 8 from deforming.

After the molten metal in the cavity 19 has solidified,
When the main ram 7 is hydraulically raised to raise the movable mold 9 together with the movable platen 6 and the mold is opened, the cavity 1 is opened.
The solidified product in the mold 9 is held by the movable mold 9 and rises, so the product is pushed out by the extrusion pin and taken out of the machine by the product take-out device, thereby completing the injection cycle.

In this embodiment, an example was shown in which the ram cylinder 24 was provided only on the fixed platen 2, but it would be more effective if it was provided on both the fixed platen 2 and the movable platen 6. In addition, although this embodiment shows an example in which the present invention is applied to a vertical mold-clamping vertical injection die-casting machine, the mold-clamping direction and the injection direction are not limited, and the same applies to plastic injection molding machines. The same effect can be obtained. The effects of the present invention are particularly great in horizontal mold clamping devices where the rear surface of the fixed platen is a space.

[0017]

As is clear from the above explanation, according to the present invention, in a mold clamping device for injection molding, tie rods are provided at a plurality of corners near the center axis of a mold holding platen. , a cylinder hole connected to a hydraulic power source and opened toward the mold side is provided, and a fluid pressure cylinder equipped with a ram that protrudes from the cylinder hole using fluid pressure is embedded in this cylinder hole, so that the platen is clamped by mold clamping force. Even if the mold is curved, the center part of the rear surface of the mold can be pressed to prevent it from curving, so a molded product with accurate shape and dimensions can be reliably and easily obtained. Moreover, the melt does not leak from between the molds during injection, improving safety. Furthermore, no burrs are generated due to solidification of leaked melt, and the quality of the product is improved.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway front view of a die casting machine embodying the present invention.

FIG. 2 is a plan view of a fixed platen.

FIG. 3 is a sectional view taken along line III-III in FIG. 2;

FIG. 4 is a longitudinal sectional view of a hydraulic cylinder embedded in a fixed mold.

[Explanation of symbols]

2 Fixed platen 2b Cylinder hole 3 Tie rod 4 Cylinder platen 6 Movable platen 8 Fixed mold 9 Movable mold 24 Ram cylinder 25 Cylinder 29 Ram

Claims (1)

[Claims] Claim 1: A cylinder hole that is connected to a hydraulic power source and opens toward the mold side is provided near the center axis of a mold holding platen that is provided with tie rods at a plurality of corners; A mold clamping device for injection molding, characterized in that a fluid pressure cylinder equipped with a ram that protrudes from a cylinder hole using fluid pressure is embedded therein.