JPH0419010B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a method for sequentially clamping a plurality of molds and injecting resin into the molds, such as in a rotary table injection molding machine. It relates to injection molding machines.

[Prior Art] In a conventional injection molding machine, for example, a rotary table injection molding machine, a plurality of molds are installed, and the molds are sequentially clamped and molten resin is poured into the molds. For example, while resin is being injected into one mold, the resin in another mold is cooled and the molded product is taken out from the mold. There is a known method that improves molding productivity.

As a mold clamping device for clamping a mold, for example, one disclosed in Japanese Patent Application Laid-Open No. 189916/1983 is known.

This mold clamping device is provided one for each of the plurality of molds, and is configured to open/close and clamp each mold. Therefore, after injection, the resin in each mold can be cooled while maintaining the mold clamping force, and during this time the resin can be injected into other molds. . Therefore, it is effective in improving molding productivity.

However, since each mold is provided with a separate mold clamping device, the injection molding machine itself inevitably becomes large in size and has a complicated structure.

For this reason, an injection molding machine shown in FIGS. 9 to 12 has been provided which eliminates the above-mentioned drawbacks (for example, Japanese Patent Application Laid-open No. 50-60554).

In these figures, 101 is a rotary table formed in the shape of a disk, and this rotary table 101 is adapted to be rotated around its axis. A mold clamping device 102 is provided at the station of the rotary table 101, and a mold opening/closing device 103 is provided at the station.

Further, a plurality of molds 104 are provided on the rotary table 101, and these molds 104
is provided with a small cylinder 105 for maintaining mold clamping force in the mold 104 itself. Therefore, in the mold 104, even after the mold clamping force is released by the mold clamping device 102, the mold clamping force by the small cylinder 105 is maintained.

In the injection molding machine configured as above,
A mold 104 is clamped by a mold clamping device 102 at a station. At this time, the mold 10
Inject the resin into 4. Further, when the mold 104 is in the mold clamped state by the mold clamping device 102, the small cylinder 105 is also kept in the mold clamped state. Then, the mold 104 is moved to the mold clamping device 1
Even when the mold clamping force at step 02 is released and the rotary table 101 moves from station to station, the mold clamping force is maintained. For this reason, the mold 10
While the mold 4 moves from station to station, the resin in the mold 104 is cooled in a clamped state. Then, the mold 104 is opened by the mold opening/closing device 103 at the station position, and the molded product solidified within the mold 104 is taken out. Next, the mold 104 is closed again by the mold opening/closing device 103 and sent to the mold clamping device 102 .

Therefore, in the injection molding machine configured as described above, separate mold clamping devices are not provided for each of the plurality of molds.
Compared to the injection molding machine shown in Japanese Patent No. 189916, this injection molding machine has the advantage that it can be made smaller in size and its structure can be simplified.

[Problem to be solved by the invention] Therefore, in the above conventional injection molding machine,
Also in what is shown in Japanese Patent Application Laid-Open No. 61-189916,
Furthermore, in the method disclosed in Japanese Patent Application Laid-open No. 50-60554, when molding a resin that expands after injection, such as foamed resin, the mold is maintained in a clamped state by a force that counteracts the pressure of the expansion. Since the mold can be cooled while the resin is being injected into other molds during the cooling process, the molding efficiency can be improved.

However, when injection molding ordinary resin,
In order to compensate for the shrinkage of the resin as it cools, a pressure holding process is required to supply the resin into the mold at a predetermined pressure immediately after injection. The drawback is that the rotary table cannot be rotated to move the mold to a predetermined position. There was also the problem that the thicker the molded product, the longer the time required for cooling, which lowered productivity.

The present invention has been made in view of the above circumstances, and aims to improve productivity of molded products by eliminating wasted time due to holding pressure.

[Means for Solving the Problems] In order to achieve the above object, the present invention sequentially moves a plurality of molds each forming a cavity with a pair of molds in front of a heating cylinder, and clamps the molds with a mold clamping device. In an injection molding machine that injects resin into the cavity of the mold from a nozzle of a heating cylinder through a resin introduction groove and a gate groove, each of the molds is provided with a mold closing holding mechanism that maintains the mold in a closed state. Each of the molds is individually attached, and one of the molds is provided with a compression mechanism and a compression core that compresses the resin in the cavity by the compression mechanism.

[Function] The mold closing and holding mechanisms individually attached to each mold hold the mold in a closed state. The compression core is moved by a compression mechanism to compress the resin in the cavity and maintain it at a predetermined pressure. Therefore, the mold, which has been clamped by the mold clamping device and injected resin into the cavity, can be immediately moved from in front of the heating cylinder, thereby improving productivity.

[Example] Hereinafter, an example in which the present invention is applied to a rotary table injection molding machine is shown in FIGS. 1 to 8.
This will be explained with reference to the figures.

1 and 2, 1 is a rotary table (hereinafter abbreviated as table) of a rotary table injection molding machine, and this table 1
is formed into a disk shape and rotates around its center. The molds 2 are attached to the upper surface of the table 1 at predetermined radial positions from the center of rotation and at positions equally divided into four in the circumferential direction.

The mold 2, as shown in FIGS. 3 and 4,
It consists of a lower mold unit 4 fixed to a table 1 with mold attachment bolts 3, and an upper mold unit 5 placed separably on the lower mold 4.

The lower mold 4 is attached to the table 1 using the mold mounting bolts 3 mentioned above.
The lower mold mounting plate 6 fixed to the lower mold mounting plate 6
A lower mold block 7 is connected to the lower mold block 7 by bolts 6b.

An insertion hole 6a is formed in the lower die mounting plate 6 at a position coinciding with the axis of the die 2, into which a rod of an ejector cylinder, which will be described later, is inserted.

Further, an ejector recess 7a communicating with the insertion hole 6a is formed in the center of the lower end surface of the lower mold mounting plate 6, and the ejector recess 7a is provided with an ejector recess 7a that is movable in the vertical direction. An Ector plate 8 is provided.

Furthermore, a lower molding recess 7b in which the molded product is molded is formed on the upper surface of the lower mold block 7.
A through hole 7c into which an ejector pin 9 (described later) is inserted is formed between the lower molding recess 7b and the ejector recess 7a.

Further, an ejector pin 9 is connected to the ejector plate 8, and the ejector pin 9 is formed to be slidably and tightly fitted into the through hole 7c.

Further, on the upper surface of the lower mold block 7, there is a resin introduction groove 7d that forms a sprue, a runner, etc. when the lower surface of the upper mold 5 is brought into close contact with the resin introduction groove 7d;
A gate groove 7e is formed to form a gate communicating from the runner etc. to the lower molding recess 7b.

The upper mold 5 is provided at its upper end with a pressing plate 10 that receives pressing force from a movable platen 29, which will be described later, and a cylinder member 11 is connected to the lower side of the pressing plate 10 with bolts 10a.

The cylinder member 11 is connected to the press plate 10 by the bolts 10a with the cylinder head 13 in close contact with the upper surface of the cylinder block 12. A piston head side passage 13a communicating with the axis of the lower surface of the piston head 13 is formed.

Further, the cylinder block 12 has a large diameter hole 12a and a small diameter hole 12b connected and penetrated from the upper surface at the axial center position, and the large diameter hole 12a and the small diameter hole 12b are connected and penetrated from the outer surface at the lower end position of the large diameter hole 12a. A piston rod side flow path 12c communicating therein is formed.

Further, an O-ring groove 12d is formed at an intermediate position in the vertical direction of the small diameter hole 12b, and an O-ring 14 is fitted into the O-ring groove 12d. A piston (compression mechanism) 15 is slidably and tightly fitted into the large diameter hole 12a, and a piston (compression mechanism) 15 is tightly fitted into the large diameter hole 12b.
A rod 16 connected to a piston 15 is slidably and tightly fitted to the piston 15.

The piston 15 has an O-ring groove 15a on its outer periphery.
is formed, and an O-ring 17 is fitted into the O-ring groove 15a. In addition, the above rod 1
A compression core 18 is connected to the lower end of the rod 16 so as to be aligned with the axis of the rod 16, and a compression core 18 is tightly fitted to the lower side of the cylinder block 12 so as to be able to slide freely around the outer periphery of the compression core 18. An upper template 19 having a fitting hole 19a is connected by a bolt 19b.

The compression core 18 is formed so that the height of its outer circumferential surface is equal to the thickness of the upper mold plate 19, and the outer circumferential surface 18
The lower end portion of a is formed to tightly fit into the inner circumferential surface of the lower molded recess 7b. The lower side of the outer peripheral surface 18a is reduced through a stepped portion 18b, so that a cavity 20 is formed between it and the lower molded recess 7b.

Further, as shown in FIG. 4, a mold closing block 21 is provided on the outer circumferential surface of the cylinder block 12 at an axial center position in a plane parallel to the resin introduction groove 7d. In the outer position of
A column 22 and a clamper 2 serve as a mold closing holding mechanism.
3 is provided.

The column 22 is erected on the table 1, and the clamper 23 is fixed to the upper end of the column 22 and presses the mold closing block 21 downward. Then, when pressure oil is supplied to the hydraulic cylinder 23b of the clamper 23, the claw 23
The tip side of the claw 23a is rotated and moved to the upper surface side of the mold closing block 21, and the claw 23a is pressed against the upper surface of the mold closing block 21 to hold the mold 2 in a closed state, or the tip side of the claw 23a is held in a closed state. By rotating the mold closing block 21 away from the upper surface thereof, the mold 2 can be separated in the vertical direction.

Furthermore, this clamper 23 is controlled by a switching valve 24 for keeping the mold closed, as shown in FIG. That is, when the solenoid 24a of the switching valve 24 for mold closing holding is energized, pressure oil flows into the hydraulic cylinder 23b so as to press the pawl 23a against the mold closing block 21, closing the mold 2, and energizing the solenoid 24b. Then, pressure oil flows into the hydraulic cylinder 23b so as to separate the pawl 23a from the mold closing block 21, and the mold 2 can be separated in the vertical direction.

Further, the piston head side flow path 13 of the upper die 5
The piston rod side flow path 12c is connected to the A and B ports of the resin compression switching valve 25, respectively.

The resin compression switching valve 25 allows pressurized oil to flow through the piston head side flow path 1 when the solenoid 25a is energized.
3a, the compression core 18 is moved downward to compress the resin in the cavity 20, and the solenoid 2
5b is excited, pressure oil is supplied to the piston rod side flow path 12c, the compression core 18 is moved upward, and the capacity of the cavity 20 is returned to the initial setting state.

Further, a pressure reducing valve D is arranged in front of the pressure port P of the switching valve 25 for resin compression, so that the compression pressure of the resin can be arbitrarily selected.

Further, at the rotation center position and two outer positions of the table 1, tie bars 26, 26, 26 are erected at positions forming an equilateral triangle in a planar state, as shown in Figs. 1 and 2. , the axis of the mold 2 installed on the table 1 passes through the center of the equilateral triangle. At the upper ends of these tie bars 26, there is an equilateral triangular mold clamping cylinder mounting plate 27 whose corners are fixed to each tie bar 26.
A mold clamping cylinder mold clamping device 28 is provided at the center of the mold clamping cylinder mounting plate 27.

The mold clamping cylinder 28 is installed on the mold clamping cylinder mounting plate 27 so that its rod 28a hangs down, and a movable platen 29 that presses against the upper surface of the upper mold 5 of the mold 2 is provided at the tip of the rod 28a. It is provided.

Further, a holding member 30 is provided below the table 1 and aligned with the axis of the mold clamping cylinder 28 .

This holding member 30 is provided with a sliding plate 30a on its upper end that slides smoothly on the lower surface of the table 1, and when the mold 2 is clamped between the table 1 and the movable platen 29. , the table 1 is held from below.

In addition, the rotation center of table 1 and mold clamping cylinder 2
A heating cylinder 31 and a mold separation device 32 are provided on a line connecting the axis of the table 1 with the rotation center of the table 1 in between.

The heating cylinder 31 is installed outside the mold clamping cylinder 28, and is used to knead and melt resin using a screw arranged inside the heating cylinder 31, and inject the resin from a nozzle 31a. The entire heating cylinder 31 is installed in a direction from the axis of the mold clamping cylinder 28 toward the rotation center of the table 1, and a nozzle 31a is inserted into the axis of the mold clamping cylinder 28 by a hydraulic cylinder (not shown). It is possible to move freely in the direction of approaching and separating.

The mold separation device 32 is installed on the opposite side of the mold clamping cylinder 28 with respect to the rotation center of the table 1, and uses a mold gripping device 32a that moves in the vertical direction to remove the upper mold 5 of the mold 2. It is designed to be separated from the lower mold 4 and lifted. An ejector cylinder 33 is provided below the table 1 directly below the mold gripping device 32a, making it possible to eject the molded product within the mold 2.

Next, the operation of the rotary table injection molding machine configured as described above will be explained.

In this injection molding machine, table 1 is set at 90°.
The molds 2 are sequentially moved directly below the movable platen 29 by rotating one by one. Then, at a position directly below the movable platen 29, the mold 2 is clamped as shown in FIG. 6, and the heating cylinder 31 is inserted into the clamped mold 2 as shown in FIG. Inject the resin. When clamping the mold 2, pressure oil is supplied to the mold clamping cylinder 28 to extend the rod 28a, and the mold 2 is compressed between the table 1 held by the holding member 30 and the movable platen 29. Furthermore, when injecting the resin, the tip of the nozzle 31a of the heating cylinder 31 is pressed against the sprue part of the mold, and the molten resin in the heating cylinder 31 is transferred to the resin introduction groove 7.
d, inject into the cavity 20 through the gate groove 7e. When the resin is completely filled into the cavity 20, the solenoid 25a of the resin compression switching valve 25 is energized to supply pressure oil to the piston head side flow path 13a. Then, as shown in FIG. 8, the piston 15 moves downward and the compression core 18 is pushed downward. At this time,
The gate groove 7 is formed by the outer peripheral surface 18a of the compression core 18.
e is closed, and the pressure of the resin within the cavity 20 increases. The compression pressure of this resin is appropriately set by a pressure reducing valve D. With the resin compressed in this way, the rod 28a of the mold clamping cylinder 28 is then retracted to achieve the mold clamping state, and the table 1 is rotated 90 degrees. Then, the mold 2 moved directly below the movable platen 29 is clamped, and resin is injected in the same manner as above. However, before releasing the mold clamping state of the mold 2 as described above, the solenoid 2 of the mold closing holding switching valve 24
a is excited and the mold 2 is held in a closed state by the clamper 23. Thereby, even after the mold clamping by the mold clamping cylinder 28 is released, the mold closed state is maintained.
Then, while the table 1 rotates and the mold 2 moves to the position of the mold separation device 32, the resin in the outer mold 2 is cooled and solidified. Mold separation device 32
At the position, the solenoid 25b of the resin compression switching valve 25 is energized to open the piston rod side flow path 12c.
Pressure oil is supplied to push the piston 15 upward, and the compression core 18 is raised to the initial setting position.
As a result, the pressure of the resin within the cavity 20 is released. Next, the solenoid 24b of the switching valve 24 for mold closing maintenance is energized, and the claw 2 of the clamper 23 is activated.
3a is separated from the mold closing block 21, and the upper mold 5 can be separated upward. And the mold gripping device 32
The upper mold 5 is grabbed and moved upward by a, the rod of the ejector cylinder 33 is extended, and the molded product is ejected upward through the ejector plate 8 and ejector pin 9.

In the rotary table injection molding machine configured as described above, immediately after filling the cavity 20 with resin, the piston 15 is pushed down to compress the resin in the cavity 20 with the compression core 18. Therefore, the pressure holding process using a screw in the heating cylinder 31, which was conventionally performed to compensate for the shrinkage of the resin during cooling, can be omitted.
Accordingly, the productivity of molded products can be improved.

Further, when the compression core 18 moves downward, the gate groove 7 is moved by the outer peripheral surface 18a of the compression core 18.
Since it closes the gate, there is no need to take the trouble to provide a mechanism to close the gate, and the cavity 20
The resin inside can be compressed. Therefore,
The structure of the mold becomes simpler and the manufacturing cost of the mold can be reduced.

Furthermore, since the resin can be held in a compressed state until it solidifies, it is possible to obtain a molded product that is dense and has fewer sink marks compared to a holding operation that makes it difficult to replenish resin after gate sealing. can.

[Effects of the Invention] As explained above, a plurality of molds each forming a cavity by a pair of molds are sequentially moved in front of a heating cylinder and clamped by a mold clamping device, and the cavity of the mold is In an injection molding machine that injects resin from a nozzle of a heating cylinder through a resin introduction groove and a gate groove, each of the above molds is individually attached with a mold closing holding mechanism that keeps the mold in a closed state. One of the molds is equipped with a compression mechanism and a compression core that compresses the resin in the cavity by the compression mechanism, so a heating tube is used to compensate for the shrinkage of the resin when it cools. The pressure holding step using the screw can be omitted, and the mold can be moved from the heating cylinder immediately after resin is injected into the cavity, improving the productivity of molded products.

[Brief explanation of drawings]

1 to 8 are views showing one embodiment of the present invention, in which FIG. 1 is a plan view of the main parts of a rotary table injection molding machine, and FIG. 2 is a main part of the rotary table injection molding machine. A side view, FIG. 3 is a sectional view of the mold, FIG. 4 is a view taken in the direction of the arrow in FIG. 3, FIG. 5 is a hydraulic circuit diagram for controlling the compression core and clamper, and FIG.
The figure is a cross-sectional view showing the mold in a clamped state, Figure 7 is a cross-sectional view showing the state in which the cavity of the same mold is filled with resin, and Figure 8 is a cross-sectional view showing the state in which the mold is unclamped after filling with resin. 9 to 12 are sectional views showing the mold, FIG. 9 is a plan view of the turntable section, FIG. 10 is a sectional view of the mold clamping device, and FIG. 11 is a sectional view showing the mold. 12 is a sectional view of the mold opening/closing device, and FIG. 12 is a side view of the mold. 2... Mold, 15... Piston (compression mechanism),
22...Column body, 23...Clamper.

Claims (1)

[Claims] 1 A plurality of molds 2 in which a cavity 20 is formed by a pair of single molds 4 and 5 are sequentially moved in front of a heating cylinder 31 and clamped by a mold clamping device 28, and the cavity 20 of the mold 2 is heated. In an injection molding machine that injects resin from a nozzle 31a of a cylinder 31 through a resin introduction groove 7d and a gate groove 7e, each of the molds 2 has mold closing and holding mechanisms 22 and 23 that keep the mold 2 in a closed state.
are individually attached, and one mold unit 5 of each mold 2 includes a compression mechanism 15 and a compression mechanism 15.
An injection molding machine characterized by being provided with a compression core 18 that compresses the resin in the cavity 20.