JPH01174430A - Ejecting device for injection molding machine - Google Patents

Abstract

PURPOSE:To reduce the whole device in size and the action to be rendered rapid by providing a compression hydraulic cylinder within the inner part of a moving plate being movable back and forth with respect to a fixing plate and inwardly mounting a protrusion hydraulic cylinder in the piston of the compression hydraulic cylinder. CONSTITUTION:Resin is injected into a cavity from the nozzle 10 of a fixing die 7 and compression is effected such that an injection cylinder 13 is operated and a die attaching plate 51 is moved. After the solidification of the resin, the moving plate 11 is moved back and the article comes to the ejection position in a state of being adhered to the moving die 7. Herein, a protruding cylinder 39 is so operated that a protruding plate 40 is advanced, and an ejection pin 47 is thrust out of a core rod 24 in order that an ejector pin 50 provided in the moving die 7 is protruded so as to stick out the article. Inasmuch as the protrusion cylinder 39 is inwardly provided in the piston 21 of the compression hydraulic cylinder 13 in this ejection device, the whole device can be reduced in size and the molding efficiency can also be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to an ejection device used in an injection molding machine to peel and eject a molded product from a mold.

[Prior Art] Fig. 1θ shows a conventional toggle type injection molding machine, in which a fixed plate 1 and an end plate 2 are erected on a pedestal 3 in a state facing each other. A movable plate 5 is supported by a tie bar 4 horizontally installed between end plates 2 so as to be movable back and forth. A fixed mold 6 and a movable mold 7 are fixedly installed on the opposing surfaces of the fixed platen l and the movable platen 5, and a mold M is constituted by both of them. A toggle mechanism 8 is disposed between the end plate 2 and the movable plate 5, and when this toggle mechanism 8 is operated by a hydraulic cylinder 9 disposed at the center of the i-node plate 2, the movable plate 5 is moved. It moves to close and open the mold. Behind the stationary plate l, there is an injection tube (shown in the figure) that holds the molten plastic raw material, and a screw (not shown) that is installed inside this injection tube and injects the plastic raw material from the injection tube into the mold through the nozzle lO. A series of operating operations such as the closing operation of the mold M, the clamping operation during injection, and the opening operation of the mold M are continuously controlled while controlling the movement speed. At the same time, the pressure applied to the screw is controlled to keep the resin pressure in the mold at an appropriate value during solidification, so as to obtain a dense molded product.

Then, when the mold is opened, the molded product moves while remaining attached to the movable mold 7, and is ejected and removed by a protruding mechanism attached to the movable platen 11. As such a protrusion mechanism, a mechanism using a hydraulic cylinder as a drive mechanism is usually used, and this is attached to the rear of the movable platen 11.

'By the way, in recent years, in order to meet the demand for products that require precision molding such as compact discs, or products that require thick and precise molding, the mold volume is contracted after injection and the mold is further clamped. There is a method (compression molding method) that performs stronger compression. This compression molding method includes the sandwich press method, in which the mold is filled with resin without the toggle fully extended, and then the toggle is extended and the mold is clamped, and the sandwich press method, in which the initial mold clamping force is relatively weak. There is a low-links method in which after resin is filled, the cavity is expanded by the resin injection pressure and further compressed. In all of these compression methods, the entire movable mold is moved relative to the fixed mold (full surface compression method), but for example, if the thickness of the molded product is uneven, the compression ratio will be lower than the thickness of the thin part. , and sufficient compression cannot be achieved. Therefore, there is a micro molding method in which only the core portion constituting the cavity of the mold is partially movable, and a movable platen is provided with a hydraulic device (hydraulic cylinder) that compresses only the core portion.

[Problems to be Solved by the Invention] However, in the conventional technology as described above, the hydraulic cylinder has a shape that protrudes from the rear of the movable plate, so a space is required to incorporate it, and the device itself is There are problems such as increased size and reduced flexibility in design due to the conflict with the above-mentioned toggle mechanism. In particular, in the micromolder type injection molding machine as described above, it is necessary to provide an ejection hydraulic cylinder in series behind the compression hydraulic cylinder.
The above-mentioned negative effects have become even stronger.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a fixed platen, a movable platen that is movable back and forth with respect to the fixed platen, and a movable platen inside the movable platen. A compression hydraulic cylinder is provided, and an ejection hydraulic cylinder is installed inside the piston of the compression hydraulic cylinder.

[Function] In the ejecting device of the injection molding machine configured as described above, the ejecting hydraulic cylinder of the compression hydraulic cylinder is installed internally, so that the ejecting hydraulic cylinder does not protrude to the rear of the movable platen. , the entire device can be made compact, the total weight of the moving platen can be reduced, and the operation can be made faster.

Since the piston rod of the ejection hydraulic cylinder is short, the piston rod can be made thinner.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

In FIG. 1, reference numeral 11 denotes a movable plate, which faces a fixed plate (not shown) on the right side of the figure, and moves by being inserted through a tie rod 12 installed between an end plate (not shown) on the left side of the figure and the fixed plate. It is set freely. The movable platen 11 is formed in the shape of a thick plate, and a toggle mechanism as described above is interposed between the movable platen 11 and the end plate to drive the movable platen 11.

A compression cylinder 13 is configured inside the movable platen 11 . That is, in the center of the movable platen 11, there is a through hole 14 that opens to the front and rear surfaces (hereinafter, the side facing the mold is referred to as the front surface, and the end plate side is referred to as the rear surface), and the diameter increases as it goes from the rear side to the front side. It is formed with a first step 15 and a second step 16. An annular holding member 17 is fixed to this second step 16 with a bolt 18, and as a result, the through hole 1
4 is formed with diameter-reducing steps extending from the rear surface to the front surface, and the portion sandwiched between these steps serves as a hydraulic chamber 19. The through hole 14 has a small diameter portion 2 with a step similar to that of the through hole 14.
0, piston 21. A sliding member 23 integrally formed with the piston rod 22 is fitted, and a core rod 24 is fixed to the front surface of the piston rod 22 with bolts 25. Oil passages 26 and 27 leading to an external oil pressure source are opened before and after the oil pressure chamber 19.
By supplying hydraulic pressure to the piston 21, the piston 21 is moved back and forth.

A cylindrical first stopper 28 for regulating the retreating position of the sliding member 23 is provided in a small diameter portion on the rear side of the through hole 14, and a fine thread 29 is formed on the inner and outer surfaces of the through hole 14 and the first stopper 28. It is screwed on and attached so that its position can be adjusted. The rear end of the first stopper 28 is set to protrude from the through hole 14 , and a key 31 extending back and forth is attached to this protrusion 30 . A sprocket 32 having an inner groove that fits into the key 31 is attached to the sprocket 32 so as to be prevented from moving back and forth by a support plate 33. This sprocket 32 is connected to a drive shaft (path shown) by a chain. The piston 21
is set to have a thickness shorter than the length of the hydraulic chamber 19, so that the piston 21 can move by the difference. The value of this difference can be changed by replacing the holding member 17. A fine thread 34 is formed on the outer peripheral surface of the small diameter portion 20, and the sliding member 2
Positioning nut (second stopper) that regulates the forward limit of 3.
35 is screwed on. A slit 36 is formed in this positioning nut 35, and after rotating the nut, the bolt 3
7 compresses the slit 36 to elastically deform the nut 35 and prevent its movement.

Inside the sliding member 23, there is a protruding cylinder 3 on the rear end side.
9 is provided, and a housing chamber 41 for accommodating the protrusion plate 40 is formed on the front end side with the front side open. The ejection cylinder 39 has a hydraulic chamber 42 formed to extend back and forth.
and a second piston 43 fitted in this hydraulic chamber 42, and the hydraulic chamber 42 is formed with oil passages 44 (the rear end side not shown) open at the front and rear ends, respectively. The second piston 43 is connected to the protrusion plate 40 via a piston rod 46, and the protrusion plate 40 has five protrusion pins 47 disposed in the center and on the circumference. 47 is inserted into a pin hole 48 formed in the core rod 24. A ring-shaped bushing 49 is attached to the opening of the pin hole 48, so that the ejecting pin 47 can be precisely aligned. Second piston 43
A dog 38 is fixedly attached to the movable plate 11, and the dog 38 penetrates the rear wall of the hydraulic chamber 42 and protrudes to the rear side of the movable plate 11. It is designed to operate a limit switch (path shown). Note that 45 is an oil passage that supplies lubricating oil around the dog 38.

A mold mounting board 51 is slidably supported by tie bars 12 on the front side of the movable board 11.

This mold mounting board 51 has the piston rod 2 in the center.
2 and a slightly larger diameter than the core rod 24.
2 is formed, and an annular step 53 having an outer diameter approximately equal to that of the piston rod 22 is formed around the rear opening, into which a spacer ring 54 is removably attached. . Bolts 55 are screwed into the bolt holes 56 of the mold mounting plate 51 and the piston rod 46 to fix the two through the step 53, and to the mold mounting plate 51 and the moving plate 11, the bolts 55 are screwed into the bolt holes 56 to fix the two. bolt 5
7 bolt holes 58 are formed.

Next, the operation of the ejection device of the injection molding machine configured as described above will be described.

First, a mounting method for full-surface compression will be explained. In the case of full-scale compression, as shown in the upper half of FIG. At the same time, the bolts 57 for connecting the mold mounting board 51 and the movable board 11 are removed. In this case, the step 53 of the insertion hole 52 is a kind of flange, and the mold mounting plate 51 and the piston rod 22 are easily and firmly connected.

Next, the first stopper 28 and the second stopper 3 determine the relative backward and forward limits of the sliding member 23 with respect to the movable platen 11.
Adjust 5. That is, when the drive shaft is driven to rotate the sprocket 32 via the chain, the rotation is transmitted to the first stopper 28 by the engagement of the inner curvature of the sprocket 32 and the key 31, and the fine thread 29 moves the sprocket 32 in the front and back direction. . As a result, the first stopper 28 projects to the inner surface of the through hole 14 and pushes the piston 21. As a result, the mold mounting plate 51 is also pushed by this amount of protrusion, so that a gap is created between it and the movable plate 11 (see FIG. 3). Adjustment of the second stopper 35 is performed using the positioning nut 3.
5 and tighten the bolt 37. 1st
The gap between the stopper 28 and the second stopper 35 provides a margin for movement of the piston 21. The mold M is fixed to the mounting surface of the mold mounting board 51 using a fixing board or the like.

Below, the entire compression injection molding process is shown in Figures 3 to 5.
This will be explained using figures. The toggle mechanism is operated to advance the movable plate 11 to form a cavity between the movable mold 7 and the fixed mold 6 (mold clamping process, see FIG. 3). Here, mold 6.7
There is a compression margin between them. Next, resin is injected into the cavity from the nozzle lO of the fixed mold 7, and at an appropriate timing after or during injection, the compression cylinder 13 is activated to move the mold mounting plate 51, and the compression is performed. (compression step, see Figure 4). In the compression process, the core rod 24 and the mold mounting plate 51 move forward together,
Pressure is applied uniformly to the entire surface of the mold M, and the second stopper 35
comes into contact with the first stopper 28 and stops. By adjusting the position of the second stopper 35, the final thickness of the molded product can be precisely set.

After the resin solidifies, the toggle mechanism operates and moves the moving plate 1.
1 retreats, and the product reaches the ejecting position with the product attached to the movable mold 7 (mold opening process). Here, the ejection cylinder 3
9 is activated, the ejector plate 40 moves forward, the ejector pin 47 protrudes from the core rod 24, and the ejector bin 50 provided on the movable mold 7 is ejected to eject the product (ejecting process, see FIG. 5). After this, both the ejection cylinder 39 and the compression cylinder 13 are returned to their original positions, and the mold clamping process is started again.

Next, a mounting method for performing core compression will be explained with reference to the lower half of FIG. Remove the bolts 55 that connect the mold mounting board 51 and the piston rod 22, and remove the spacer ring 54.
At the same time, the mold mounting board 51 is fixed to the movable board 11 by inserting the bolts 57 into the bolt holes 58. In this case, the bolts 55 and 57 are exposed on the front surface of the mold mounting board 51, making attachment and detachment easy. Moreover, since the mold mounting board 51 is supported by the tie bars 12 and the movable board 11 is movable by a toggle mechanism, it is easy to open both. As shown in FIG. 6, the movable mold 7a is used for core compression, and the core mold 7b is fixed to the core rod 24. The method of adjusting the stoppers 28, 35 is the same as in the case of full-plane compression, and is carried out in the order shown in FIGS. 6 and 7. In this case, the mold mounting plate 51 and the core rod 24 are separated, so when the first stopper 28 is advanced, the core rod 24 is separated.
4 protrudes, the core mold 7b moves forward, and the second
The stopper 35 also restricts the forward position of only the core rod 24.

The injection molding process for core compression will be explained below with reference to FIGS. 7 to 9. The mold clamping process is the same as the full-surface compression, but there is no need for a compression margin between the molds 6.7a (7th
(see figure). Next, injection is performed, and the compression cylinder 13 is operated to perform a compression process. In this case, the core mold 7b
Since only the mold 7a is moved relative to the mold 7a to compress the cavity, sufficient compression can be performed partially even if the mold is thick only at the center and thin at the periphery, as shown in this example. Can be done. As in the case of full-surface compression, the cavities before and after compression can be precisely set by both stoppers 28 and 35. The mold opening and ejection steps are the same as described above.

In the ejecting device as described above, since the ejecting hydraulic cylinder 39 is installed inside the piston 21 of the compression hydraulic cylinder 13, the piston rod 46 can be relatively short, and therefore even a small diameter rod can be used. Can withstand bending stress. Furthermore, for the same reason, the weight of the members driven by the ejection hydraulic cylinder 39 can be reduced, so the moment of inertia of these members is small.
The time required to take these items in and out can be shortened,
Molding efficiency can be increased. In addition, the bushing 49 attached to the opening of the bottle hole 48 allows the ejector pin 47 to be precisely centered and ejected accurately. Prevents load from being applied.

In addition, in this embodiment, when the mold mounting plate 51 is attached to the working end (piston rod) 22, the compression device compresses the mold mounting plate 51 to perform full compression, and when the connection is removed, the mold core Core compression can be performed by pressing only the part. Therefore, if the shape of the molded product is relatively simple and only needs to be compressed over the entire surface, it is possible to mass produce multiple molds in one process by arranging the cavities over the entire surface of the mold, and it is also possible to mass produce multiple molded products in a single process by arranging cavities over the entire surface of the mold. For complex shapes, core compression can be used to obtain sufficient compression, and can be used depending on the purpose. Furthermore, the insertion hole 52 of the mold mounting plate 51 is made smaller in diameter than the outer diameter of the working end 22, and an annular step 53 larger than the outer diameter of the working end 22 is formed at the peripheral edge of the insertion hole 52 on the working end 22 side. By sandwiching the spacer 54 between the mold mounting plate 51 and the working end 22 with the bolts 55, the mold mounting plate 51 and the working end 22 can be easily and firmly fixed. This method has the advantage of reducing work effort and improving efficiency, as well as eliminating looseness between each member to obtain a molded product of good quality, and making it easy to switch between full-surface compression and core compression. are doing.

[Effects of the Invention] As detailed above, the present invention includes a fixed platen, a movable platen that is movable back and forth with respect to the fixed platen, and a compression hydraulic cylinder configured inside the movable platen. Since the ejection hydraulic cylinder is built into the piston of the compression hydraulic cylinder, the ejection hydraulic cylinder does not protrude behind the movable platen, and the distance between the fixed platen and the end plate of the injection molding machine can be shortened. The entire device can be made compact, and the total weight of the movable platen is reduced, which speeds up the operation and increases molding efficiency. Similarly, in ejecting hydraulic cylinders, the piston rod is short, so the bending load is small, which allows the piston rod to be made thinner, reducing the total weight of the ejecting member, and improving molding efficiency by speeding up the operation. It has excellent effects such as:

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the main parts of an ejection device of an injection molding machine according to an embodiment of the present invention, FIGS. 2 to 9 are schematic diagrams showing its operation, and FIG. 1θ is a schematic diagram showing the configuration of a conventional example. be. 11...Moveable board! 3... Compression cylinder, 21... Piston, 28... First stopper, 35... Second stopper.

Claims (1)

[Claims] A fixed plate, a movable plate provided to be movable back and forth with respect to the fixed plate, and a compression hydraulic cylinder configured inside the movable plate, and a piston of the compression hydraulic cylinder is provided with an ejection hydraulic cylinder. An ejection device for an injection molding machine, characterized in that it is equipped with a