JPS6230084B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an injection molding method for synthetic resin or the like in which a gate portion is not integrally formed in a molded product.

Conventionally, in the injection molding method for synthetic resins, etc., a method has been proposed in which molten resin is injected into a cavity and then the resin is sealed and solidified. It is as shown in the figure. That is, in Figure 1,
Reference numeral 4 denotes a fixed plate, which is fixed to a fixed side mounting plate 3 having a spring pusher 1 and a locate ring 2 attached to the center thereof. 9 is a movable plate, spacer block 1
2. Movable platen 17 via movable side mounting plate 16
is attached to. 5 is a fixed insert fitted into a groove provided on the fixed plate 4; 6 is a movable insert fitted loosely into a groove provided on the movable plate 9; when the mold is clamped, the fixed insert 5 A cavity 21 is formed between the two. 8 is a compression rod, the upper end of which is connected to the movable insert 6
The lower end is compressed by the plate 10, 1.
It is clamped and fixed to 1. The compression plates 10 and 11 are housed in the recesses of the spacer block 12, and both ends of their lower surfaces are engaged with the shoulders of the recesses. 1
Reference numerals 3 and 14 denote gate shaft plates, which are housed in the lower recess of the spacer block 12 and have their lower ends engaged with the movable mounting plate 16, and between their upper surfaces and the lower surfaces of the compression plates 10 and 11. It is configured to form a predetermined gap a. Reference numeral 15 denotes a compression rod attached to the lower surface of the gate shaft plate 14, which is housed in an opening provided in the movable side mounting plate 16, and is connected to the upper surface of the step provided on the outer periphery of the compression rod 15 and the lower surface of the shoulder of the opening. A predetermined gap b is formed between the two. . A compression piston 18 is slidably housed in a cylinder bored in the movable platen 17, and the upper end surface of the compression piston is brought into contact with the lower surface of the compression rod 15. Both ends of the cylinder are connected to a hydraulic pump 20 via a hydraulic switching valve 19. Reference numeral 7 designates a gate shaft pin whose base end is fixed to the gate shaft plates 13 and 14, and whose distal end extends toward the gate portion 22 communicating with the cavity 21. Gate 22 is
It is communicated with the nozzle through a runner 25 and a sprue 24.

In the conventional injection compression molding apparatus configured as described above, after the fixed plate 4 and the movable plate 9 are brought into close contact with each other on the parting line 23 surface and the mold is clamped, molten resin is injected through the nozzle pusher 1. Then, the resin is filled into the cavity 21 from the gate 22 through the sprue 24 and the runner 25, and the filling pressure presses the movable insert 6 downward, and the resin is applied to the compression plate 10 via the compression rod 8. , 11 are crimped onto the shoulders of the spacer block 12. Further, the gate shaft pin 7 is also pressed by the resin pressure, presses the gate shaft plates 13 and 14, presses its lower surface to the upper surface of the movable mounting plate 16, and connects the lower surface of the compression plate 11 and the gate. A predetermined gap a is formed between the upper surface of the shutter plate 13 and the upper surface of the stepped portion of the compression rod 15 connected to the lower surface of the gate shaft plate 14 and the movable side mounting plate 16.
A predetermined gap b is formed between the opening and the shoulder of the opening. When the cavity 21 is completely filled with the molten resin, the hydraulic switching valve 19 is switched to close the compression piston 1.
Push up 8. As a result, the gate shaft pin 7 is pushed up and operated via the compression rod 15 and the gate shaft plates 13 and 14, and the tip of the gate shaft pin 7 closes the gate portion 22. When the gate shaft plate 13 moves by the gap a,
The movable insert 6 is pressed through the compression rod 8 which is in contact with the compression plate 11 and is fixed to the compression plates 10 and 11, thereby compressing the molten resin within the cavity 21. The amount of operation of the movable insert 6 is the amount corresponding to the volumetric contraction of the resin filled in the cavity 21, and the amount of operation b of the compression rod 15 is the amount corresponding to the volume contraction of the resin filled in the cavity 21.
and an amount corresponding to the volumetric contraction of the resin, which is the same as the operating amount of the tip of the gate shaft pin 7.

However, the conventional injection molding apparatus configured as described above has the following drawbacks. That is,
(1) Because the gate shaft pin is placed at a distance from the cavity part for mold structure reasons such as mold strength, the gate is closed with a part of the gate part communicating with the cavity part. (2) Since a part of the gate part is formed integrally with the molded product, after the molding process is finished, the gate part may be smaller than the molded product. There were disadvantages such as the need for processing work to remove.

Furthermore, conventionally, Japanese Patent Application Laid-Open No. 50-21054 includes a piece that separates the resin in the cavity from the resin in the mold runner part and the sprue part immediately before the molten resin filled in the cavity enters the compression process. An injection compression molding machine is shown in which the gate part is cut and then compressed and solidified. In this machine, the piece is pressed to cut the resin at the gate part and close the gate part, as the piece moves. Since the spool bush and nozzle are moved, a mechanism for moving them is required, which not only increases the size of the device but also requires extra driving force. Since the part where the gate part of the bridge is cut corresponds to the outer peripheral edge of the spool bushing, the distance from the spool part to the cavity becomes long, and the volume of the runner part is formed to be large. Therefore, since a cylinder with a large injection capacity is required, the resin remains in the cylinder for a long time, and is subjected to a large amount of thermal history, which tends to cause deterioration of the resin, that is, deterioration of the performance of the molded product.

Further, the cavity in this device is constituted by a cavity portion formed by directly processing a fixed mold and a movable mold. Therefore, each mold is large compared to the cavity part, so a large processing machine is required when machining the cavity part, which not only makes high-precision machining difficult, but also causes damage to the mold due to machining errors in the cavity part. There is a problem that the entire product ends up being defective. In particular, when a molded product is configured to have multiple cavities, the pieces that close the gate are located in the center of the mold, so the cavities are distributed radially, and as a result, the mold Furthermore, the size becomes larger, and the above-mentioned problems become more noticeable.

Furthermore, when compressing the molded resin, since the cavity is formed directly on the mold, galling of the molds is likely to occur when cutting off the outer periphery of the molded product. In order to prevent this, it is necessary to perform a hardening process, and if this hardening process is applied to the galling portion, the periphery of the cavity will be deformed, and for example, if the molded product is a lens, the precision of the lens surface will deteriorate. For this reason, if the entire mold that forms the cavity is heat-treated, not only will it be difficult to process the cavity, but the mold will also be deformed, and as a result, the precision of the molded product cannot be improved. This is what happens.

The present invention was made in order to eliminate the drawbacks of the conventional injection molding method, and includes a gate forming and closing part provided at the outer end and a cavity forming part provided inside, and is attached to a fixed plate. a movable sleeve having a cylindrical end portion having a gate forming/occluding portion that engages with the gate forming/occluding portion of the fixing member; and a movable sleeve disposed inside the movable sleeve so as to be movable relative to each other. A movable piece having a cavity forming part at its tip and movable members slidably supported by a movable plate are arranged facing each other, and both gate forming and closing parts form a gate, and both cavity forming parts form a cavity. After injecting and filling the molten resin into the cavity through the gate, the movable sleeve of the movable member is pressed to cut the resin at the gate and close the gate, and then the molten resin in the cavity is solidified. The object of the present invention is to provide an injection molding method for synthetic resins, etc., which is characterized by the following.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIGS. 2 and 3 show an embodiment of an apparatus for carrying out the injection molding method according to the present invention. In the figure, reference numeral 32 denotes a fixed plate, which is attached to the fixed side mounting plate 31. The fixing plate 32 is provided with a hole, into which the outer fixing sleeve 33, into which the fixing piece 35 is inserted and fixed via the inner fixing sleeve 34, is fitted so that its tip protrudes. It's stuck. As shown in FIGS. 4A and 4B, the outer fixing sleeve 33 has a gate forming and closing convex portion 55 formed on its lower end surface, which has the function of cutting the resin of the gate part, and also has a protrusion 55 for forming and closing the gate. The sleeve 34 is longer than the outer sleeve 33, as shown in FIG. . A movable plate 39 is supported by a receiving plate 42, which is attached to a movable mounting plate 51 via a spacer block 48, and the movable mounting plate 51 is attached to a movable platen 53.
In the upper part of the space formed by the receiving plate 42, the spacer block 48, and the movable side mounting plate 51, gate shutter plates 44 and 45 are installed, and the compression plate 4 is installed in the lower part.
9,50 are arranged. Movable plate 39 and receiving plate 4
2 is provided with a communicating hole, and as shown in FIGS. A movable sleeve 40 provided with a recess 56 and having the same diameter as the outer fixed sleeve 33 is slidably inserted through the sleeve, and its lower end is inserted into the gate shaft plates 44, 4.
It is clamped and fixed with 5. The gate shaft plate 45 is connected to a gate shaft piston 46 operated by a hydraulic switching valve 47, and when the piston 46 is inactive, as shown in FIG.
A predetermined gap a is formed between the lower surface of the receiving plate 42 and the upper surface of the gate shutter plate 44. A movable piece 41 is movably fitted into the movable sleeve 40 , and its upper end surface corresponds to the lower end surface of the fixed piece 35 to form the lower surface of a cavity 54 , and its lower end is connected to the compression rod 43 . The lower end of the compression rod 43 is clamped and fixed to the compression plates 49 and 50. Reference numeral 52 denotes a protruding rod that is in contact with the lower surface of the compression plate 50, and is slidably arranged in a hole bored in the movable side mounting plate 51 and the movable platen 55, and its lower end is connected to a protruding rod operation part (not shown). connected.

Next, the operation of the device configured in this way will be explained. First, by a mold clamping operation, the fixed plate 32 and the movable plate 39 are brought into close contact with each other, and the parting line is closed.
At this time, the tip of the inner fixing sleeve 34 holding the fixing piece 35, which is incorporated into the outer fixing sleeve 33 supported by the fixing plate 32 so that its tip protrudes, can slide into the movable plate 39. The cavity 54 is inserted into the movable sleeve 40 supported by the movable sleeve 40, and forms a cavity 54 with the distal end of the movable piece 41 which is slidably fitted into the movable sleeve 40. The convex portion 55 of the outer fixed sleeve 33 and the concave portion 56 of the movable sleeve 40 do not fit tightly together, and form a passage for the molten resin to the cavity 54 .
Further, a gap a is maintained between the gate shutter plate 44 and the lower surface of the receiving plate 42, as shown in FIG.

In this state, when molten resin is injected through the nozzle, the injection pressure causes the resin to reach the sprue 3.
6. Through the gate 38 formed between the tip and bottom of the runner 37 and the loose fit between the convex portion 55 and the concave portion 56 provided on the outer fixed sleeve 33 and the movable sleeve 40, respectively, The cavity 54 is filled. The state is shown in FIG.
When the filling of the resin into the cavity 54 is completed, as shown in FIG. 3, the hydraulic switching valve 47 is operated to push up the gate shaft piston 46.
Gate shaft plate 4 connected to this
5, the movable sleeve 40 is pushed up. When the movable sleeve 40 is pushed up, the convex portion 55 of the outer fixed sleeve 33 and the concave portion 5 of the movable sleeve 44
6 are tightly fitted together, cutting the resin present in the gate portion 38 and closing the gate, allowing the resin filled in the cavity 54 to be removed from the cavity 54.
It is completely trapped inside and solidified. Then, when the resin in the cavity has cooled and solidified, the mold is opened and the molded product is taken out. In addition, at this time, the compression plate 50
By pushing out the molded product with the protruding rod 52, the movable piece 41 is pushed up via the compression rod 43, and the molded product is discharged from the cavity. Next, the hydraulic switching valve 47 is operated to return the gate shaft piston 46 to its initial state, and one cycle is completed.

FIG. 8 shows the gate shutter plates 44, 45.
Another example of the pushing-up operation means is shown in which a cam 46' is provided on the lower surface of the gate shaft plate 45, and the cam 46' is connected to a hydraulic device, pneumatic device, electromagnetic device, or other mechanical pressurizing device 47. ', and the gate shaft plates 44, 4
A return spring 57 is installed between the receiving plate 42 and the plate 44 for returning the part 5.

Further, the shape of the cavity is not limited to that shown in FIG. 2, etc., but can also be applied to various shapes as shown in FIGS. 9A, B, and C, for example. In addition, the outer and inner fixation sleeves and fixation pieces are
Although shown as being formed separately, they can operate in the same way even if they are formed integrally.

As described above in detail based on the embodiments, the present invention provides a fixing member attached to a fixing plate that includes a gate forming and closing part provided at the outer end and a cavity forming part provided inside. , a movable sleeve having a cylindrical end portion having a gate forming/occluding portion that engages with the gate forming/occluding portion of the fixed member; and a cavity forming portion at the distal end movably disposed inside the movable sleeve. A movable piece having a movable piece and a movable member slidably supported by a movable plate are arranged facing each other, and both gate forming and closing parts form a gate, and both cavity forming parts form a cavity, and the above-mentioned material is passed through the gate. After the cavity is injected and filled with molten resin, the movable sleeve of the movable member is pressed to cut the resin at the gate, close the gate, and solidify the molten resin in the cavity. Unlike the method in which the resin is solidified with the gate part communicating with the cavity, the gate part does not communicate with the cavity part during molding, resulting in good mass balance and stable dimensional accuracy. In addition, there is no need for the removal process of the gate part, which is required when the gate part is integrally molded into the molded product, and therefore, scratches, dirt, and dust generated during the removal process can be avoided. Effects such as being able to prevent adhesion etc. can be obtained.

In addition, the present invention cuts the resin at the gate and closes the gate by a simple method of pressing the movable sleeve without moving the sprue, runner, etc., so that the sprue, runner, etc. The resin of the gate portion can be cut and the gate can be closed by a simple operation method without requiring a moving mechanism for the members to be moved, and without requiring extra driving force. Further, the present invention performs injection molding using a cavity and a gate formed by a fixed member attached to a fixed plate and a movable member consisting of a movable sleeve and a movable piece slidably supported by a movable plate. These fixed members and movable members are individually made with high precision using small processing machines, and can be individually heat-treated, so injection molding can produce high-precision molded products. The law can be easily implemented.

Furthermore, in the present invention, since the fixed member and the movable member constituting the cavity are separately attached to the fixed plate and the movable plate, they can be easily replaced, and the movable sleeve, movable piece, etc. can be easily replaced. This makes it possible to mold products of various shapes and wall thicknesses with high precision, and when using a multi-cavity injection molding method, it is possible to individually adjust the members that make up each cavity. For example, the size of the movable sleeve can be easily adjusted to correspond to the movable piece.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway plan view of a conventional injection molding device, and FIG. 2 is a partially cutaway plan view showing the state of the device during injection for carrying out an embodiment of the injection molding method according to the present invention. 3 is a partially cutaway plan view showing the state of the device shown in FIG. 2 when the gate is closed. FIGS. 4A and 4B are a partially cutaway plan view and front view of the outer fixing sleeve. Fig. 4C is a partially cutaway plan view of the inner fixed sleeve, Figs. 5A and B are a partially cutaway plan view and front view of the movable sleeve, Fig. 6 is an enlarged view of the main part of Fig. 2, and Fig. 7 is an enlarged view of the main part of FIG. 3, FIG. 8 is a partially cutaway plan view of a modification of the device shown in FIGS. 2 and 3, and FIGS. 9A, B, and C are views of the cavity, respectively. It is a figure which shows deformation|transformation of a shape. In the figure, 31 is a fixed mounting plate, 32 is a fixed plate, 33
is an outer fixing sleeve, 34 is an inner fixing sleeve,
35 is a fixed piece, 36 is a sprue, 37 is a runner, 38 is a gate, 39 is a movable plate, 40 is a movable sleeve, 41 is a movable piece, 42 is a receiving plate, 43 is a compression rod, 44 and 45 are gate shaft plates , 46 is a gate shaft piston, 47 is a hydraulic switching valve, 48 is a spacer block, 49, 5
0 is a compression plate, 51 is a movable side mounting plate, 52 is a protruding rod, 53 is a movable platen, 54 is a cavity, 5
5 is a convex part for forming and closing a gate, 56 is a concave part for forming and closing a gate, 46' is a gate shutter cam, 4
Reference numeral 7' indicates a gate shutter pressurizing device, and reference numeral 57 indicates a gate shutter plate return spring.

Claims (1)

[Claims] 1 For a fixing member attached to a fixing plate that has a gate forming/occluding part provided at the outer end and a cavity forming part provided inside, the gate forming/occluding part of the fixing member is attached to the cylindrical end. a movable sleeve having a gate-forming and closing part that engages with the movable sleeve; and a movable piece having a cavity-forming part at its tip disposed so as to be mutually movable inside the movable sleeve, and slidably supported by the movable plate. After arranging the movable members facing each other, forming a gate with both gate forming/closing parts and a cavity with both cavity forming parts, and injecting and filling the cavity with molten resin through the gates, the movable sleeve of the movable member is formed. A method for injection molding synthetic resin, etc., characterized in that the resin at the gate part is cut by a pressing operation and the gate is closed, and then the molten resin in the cavity is solidified.