JPS6357211B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a plastic molding method and apparatus suitable for molding materials containing glass fibers.

[Prior art]

Molding materials made by mixing polyester resin with glass fiber, etc., have various compositions and properties depending on the molding method and the purpose of the molded product, and the performance of the molded product also differs. In other words, the compression molding machine has
Since a sheet-shaped molding material called SMC (Sheet Molding Compound) is used, long glass fibers can be used, and the molded product can be expected to have excellent mechanical properties. However, with this type of molding machine, it is not only difficult to mold products with complex shapes or thick walls;
The drawback is that one molding cycle is long and efficiency is poor. In addition, the injection molding machine has dry BMC (Bulk
A chip-shaped molding compound called molding compound is used, and it is possible to mold products with complex shapes that cannot be molded with compression molding machines. The disadvantage is that the strength is reduced. In other words, in the case of an injection molding machine, resin is fed from a hopper type supply device to a screw in a hard-bottomed sleeve, and is injected into the mold from a nozzle as the screw rotates. Check rings and check valves are provided to prevent backflow of material during injection, which often creates waves in the material and breaks the glass fibers.

To solve this problem, an injection device equipped with a double cylinder and a special anti-reverse mechanism was proposed in JP-A-57-24228. Not only is the glass fiber prone to breakage between the screw and the cylinder, but also due to bending in the groove, reduction or expansion of the cross section at the check valve, reduction of the cross section at the injection nozzle, opening and closing of the stop valve, etc. However, there was a risk that the glass fibers would break, and a satisfactory effect could not be expected.

Furthermore, in order to prevent the glass fiber from breaking, attempts have been made to mold it using a transfer molding machine that does not use a screw, but it takes a long time to heat the resin before injection, resulting in a long cycle time. There were flaws.

[Summary of the invention]

The present invention has been made in view of the above points, and the resin pushed from the supply cylinder to the metering cylinder is compressed and measured between the supply cylinder and the plunger of the metering cylinder which is applied with back pressure, and after the resin is closed. This is further compressed by the plunger of the measuring cylinder, and the compressed resin is transferred to the dielectric heating device by the movement and extrusion of the measuring cylinder, where it is preheated, and then supplied to the mold injection port and injected into the mold by the injection cylinder. A plastic molding method and apparatus that improves the quality of molded products by reducing breakage of glass fibers, etc., and improves workability by shortening the molding cycle by preheating the injection resin. It provides: Embodiments of the present invention will be described in detail below with reference to the drawings.

〔Example〕

FIG. 1 is a longitudinal sectional view for explaining the plastic molding method according to the present invention and showing an embodiment of the plastic molding apparatus according to the present invention. In the figure, a fixed platen 3 connected to a cylinder platen (not shown) by four tie rods 2 is fixed on a base 1 fixed to the floor, and on the cylinder platen side of the fixed platen 3. A movable platen 4 that is movable along tie rods 2 is provided with a mold mounting surface facing a fixed platen 3. A fixed mold 5 and a movable mold 6 are mounted on the mold mounting surfaces of both platens 3 and 4 with their cavity surfaces 5a and 6a facing each other, respectively. Reference numeral 7 denotes an injection pipe fixed to the fixed mold 5, and has one end opened at the cavity surface 5a, and the other end penetrates the fixed platen 3 and is opened to the outside. Note that a supply hole 7a into which a resin mass can enter is provided above the portion of the injection tube 7 that is outside the fixed platen 3.

Diagonally above the machine configured as above, there is a
A material supply device, generally designated 8, is provided. This material supply device 8 includes a supply cylinder 9 and a hydraulic cylinder 10 that are formed in a cylindrical shape and are parallel to each other. The pistons 13 are fitted to each other so as to be able to reciprocate. Reference numeral 14 denotes a charging cylinder for charging resin into the supply cylinder 9, which is connected with an opening perpendicular to the circumferential surface of the supply cylinder 9, and has a reciprocating motion that pushes out the resin supplied from the resin inlet 15 into the supply cylinder 9. It is equipped with a freely adjustable plunger 16. At the raised position of the plunger 12, the glass fiber resin shown as an example of the resin introduced into the supply cylinder 9 by the injection cylinder 14 is compressed by lowering the plunger 12 by the hydraulic cylinder 10.
The lower end of the supply cylinder 9 is formed into a funnel shape, and a guide 17 is fixed to the flange at the lower end, and a drive cylinder 18 is fixed to this. Piston rod 1 of drive cylinder 18
A shutoff valve 20 as a resin shutoff mechanism is formed in a flat plate shape and is slidably supported by a guide 17 at the working end of the cylinder 9. By moving the piston rod 19 of the drive cylinder 18 forward and backward, the shutoff valve 20 is closed.
is configured to reciprocate to open and close the lower end opening of the supply cylinder 9.

What is generally designated by the reference numeral 21 is a measuring cylinder, which includes a driving part 23 into which the head end 22a of the plunger 22 is reciprocally fitted, and a measuring part 24 slidably supported at the upper end of this driving part 23.
The measuring section 24 includes a plunger 22.
A plunger head 22b is reciprocatably engaged. Further, a hydraulic cylinder 25 is fixed to the circumferential surface of the drive section 23, and its piston rod 2
The working end of the piston rod 6 is fixed to the measuring section 24, and by moving the piston rod 26 back and forth, the position where the measuring section 24 engages with the lower end of the supply cylinder 9 in a spigot-like manner and the position where the engagement is released are determined. It is configured to move forward and backward in between. This measuring cylinder 25 is rotatably supported by a pivot 27 on the body side, and the position where the measuring part 24 is opposed to the supply cylinder 9 as shown by the solid line in the figure, and the position where the measuring part 24 is opposed to the supply cylinder 9 as shown by the chain line in the figure will be described later. The dielectric heating device 28 is configured to selectively occupy one of the positions facing the dielectric heating device 28. By doing this, when the plunger 12 of the supply cylinder 9 advances with the shutoff valve 20 open and pushes the resin from the supply cylinder 9 into the metering section 24, a predetermined back pressure is applied to the plunger 22 on the metering cylinder 21 side. As a result, the resin is compressed between the plunger 12 and the plunger 22, and metering is performed in the metering portion according to the retreated position of the plunger 22. Also, after weighing, shutoff valve 2
0 is closed and the plunger 22 is advanced, the resin is further compressed between the plunger 22 and the shutoff valve 20.

The dielectric heating device 28 is a conventionally well-known heating device in which a heated object is positioned between a pair of upper and lower high-frequency electrodes 28a and 28b formed in a flat plate shape, and generates heat by the action of a high-frequency current. As the plunger 22 moves forward, a solid resin 29 is released from the measuring cylinder 21 facing the
It is pushed up and preheated. Also, the lower electrode 28b
is configured so that it can be moved between the front side of the figure and the back side of the paper, and the resin 29 that has finished preheating is released from the support by the movement of the lower electrode 28b and falls, and the resin 29 is released from the support provided in the injection pipe 7. A heater 30 is supplied into the injection pipe 7 from the hole 7a and provided on the outer periphery thereof.
It is heated and melted by Reference numeral 31 denotes an injection cylinder equipped with a plunger 32 that is reciprocated by hydraulic pressure.The head of the plunger is inserted into the injection pipe 7, and as the plunger 32 moves forward, the resin is injected into the molds 5 and 6. It is configured to be injected into the cavity of.

The molding operation by the molding machine configured as described above will be explained by taking as an example molding of bulk BMC, which is a thermosetting resin mixed with glass fibers. After the molds 5 and 6 are mounted on the platens 3 and 4 and the molds are clamped, pressure oil is fed into the head end of the hydraulic cylinder 10 to raise the piston 13 and plunger 12. Further, the metering portion of the metering cylinder 21 is engaged with the lower end opening of the supply cylinder 9, as indicated by the solid line in the figure, and the shutoff valve 20 is open. In this state, the resin supplied from the resin inlet 15 is introduced into the supply cylinder 9 by the injection cylinder 14, and the resin is pushed into the metering section 24 of the injection cylinder 21 by lowering the plunger 12 by the hydraulic cylinder 10. At this time, a predetermined back pressure is applied to the plunger 22 of the injection cylinder 21, so that the amount of resin corresponding to the size of the molded product is measured at the measuring section 22.
4, the plunger 22 stops retreating and the metering ends. When the shut-off valve 20 is then closed and the plunger 22 is advanced, the resin is further compressed between the plunger head 22b and the shut-off valve 20. When metering and compression are completed in this manner, the piston rod 26 of the hydraulic cylinder 25 is retracted, the metering portion 24 is separated from the lower end of the supply cylinder 9, and the plunger 22 is also slightly retracted to hold the resin within the tube. Thereupon, the metering cylinder 21 is rotated by a drive device (not shown) to the position indicated by the chain line in the figure to face the dielectric heating device 28, and the plunger 22 moves forward to push out the resin 29 onto the lower electrode 28b. The resin 29 is the upper and lower electrodes 28a and 28b.
However, in this case, since the resin 29 is further compressed after being measured, there are no gaps between the particles, and electricity can easily flow, promoting heating. In this case, the resin used is a thermosetting resin, and is cured at, for example, 150 to 160°C for 1 to 2 minutes. The curing time in step 6 is shortened, and the resin flows easily, making it easier to inject into the molds 5 and 6. The resin 29 that has been preheated is
As the lower electrode 28b moves, it is released from the support and falls into the injection pipe 7 through the supply hole 7a. In this case, a member (not shown) restricts the resin 29 from moving in the same direction together with the lower electrode 28b. Resin 29 that fell into injection pipe 7
is injected into the molds 5 and 6 as is, or is further preheated by the heater 30 and then injected into the molds 5 and 6. However, when using the heater 30, it is injected into the molds 5 and 6 in advance by the dielectric heating device 28. Since it is preheated,
Preheating time by heater 30 is shortened. The resin 29 in the injection tube 7 is injected into the cavities of the molds 5 and 6 by the advancement of the plunger 32 of the injection cylinder 31, and a molded product is obtained by heating and curing at, for example, 160° C. or higher. The molded product is taken out from the molds 5 and 6 after the mold is opened. From the second time onwards, the resin is heated and hardened in the molds 5 and 6, the molded product is taken out, and the next resin is measured, compressed, and preheated during mold clamping.

2 to 7 show other embodiments of the dielectric heating device according to the present invention, FIG. 2 is a schematic front view thereof, FIG. 3 is a schematic front view of another embodiment, and FIG. 4 is a schematic front view of the other embodiment. A plan view of the roller opening/closing mechanism applied to the embodiment, FIG. 5 is a front view from A in FIG. 4, FIG. 6 is a schematic vertical sectional view of another embodiment, and FIG. FIG. In the embodiment shown in FIG. 2, upper and lower electrodes 28a, 28b are provided as in the embodiment shown in FIG.
is supported by a pair of rollers 33 and 34. Further, in the embodiment shown in FIG. 3, the lower electrode 28b is not provided, and the rollers 33, 34
also serves as an electrode. A motor 35 fixed to the machine base side is directly connected to the roller 34 shown in FIGS. 2 and 3, and a hydraulic cylinder 36 fixed to the machine base side is connected to the shaft end of the roller 33. A piston rod 37 is connected. Furthermore, both rollers 33, 34 are connected by bendable links 38, 39, and both rollers 33, 34 are driven and connected by gears 40, 41, 42.
By doing this, when the piston rod 37 is moved forward as shown in the figure, the links 38 and 39 are bent and the gears 40, 41, and 42 are engaged, so that the motor 35
The rotation causes the rollers 33 and 34 to rotate in the same direction, and the resin 29 supported thereon also rotates and is uniformly preheated. When preheating is finished, by retracting the piston rod 37 of the hydraulic cylinder 36, the links 38 and 39 are extended and the gears 40 and 4 are
1 and 42 are released, the roller 33 separates from the fixed roller 34, and the resin 29 is released from the support and falls. In the case of the embodiment shown in FIG. 2, the lower electrode 2 is opened simultaneously with the release of the rollers 33 and 34.
8b is also moved.

In other embodiments shown in FIGS. 6 and 7,
The injection pipe 7 is formed of a part 7b on the side of the fixed platen 3 and a part 7c on the side of the injection cylinder 31, and these parts are arranged at a distance slightly wider than the length of the resin 29 to be injected and the rollers 33, 34. Part 7 of
b and 7c are integrally connected to each other at their lower sides by a member 7d. and both parts 7b, 7
rollers 33, 34 and resin 29 on them between c.
is now able to descend and enter. That is, once the resin 29 is preheated in the upper dielectric heating device 28, the dielectric heating device 28 is moved to the injection position, and as shown in FIG.
If it enters between both parts 7b and 7c, the plunger 32
moves forward to push the resin 29 into the portion 7b of the injection tube 7 and inject it into the molds 5 and 6. resin 2
9 is inserted into the portion 7b of the injection tube 7, the dielectric heating device 28 is returned to its original position.
At this time, the upper electrode 28a is raised directly upward as shown by arrow C in FIG. and return each other to their original positions. In this way, when the resin preheated in the dielectric heating device is transferred into the injection tube 7, it can be transferred quietly without dropping it, and the resin 29 and the injection tube 7 are not damaged, making it more practical. It is true.

The molding machine according to the present invention is particularly effective in molding resins mixed with glass fibers, etc., but it goes without saying that molding with various ordinary resins without glass fibers etc. can be carried out in the same way.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, in the plastic molding method and apparatus,
The resin pushed into the metering cylinder from the supply cylinder is compressed and measured between the plunger of the metering cylinder with back pressure applied, and after the resin is closed, it is further compressed by the plunger of the metering cylinder, and the compressed resin is transferred to the metering cylinder. By moving and extruding the resin, the resin is transferred to a dielectric heating device to be preheated, and then supplied to the mold injection port and injected into the mold with an injection cylinder. Since the resin movement path is straight and there is no change in the cross-sectional shape, breakage of glass fibers can be minimized when molding with glass fiber-containing resin, etc. The mechanical properties of the molded product, especially the impact strength, are significantly improved compared to conventional equipment equipped with the same equipment, and the performance of the raw material is not impaired. In addition, the resin pushed into the metering cylinder is compressed and metered between the plunger of the metering cylinder, which retreats according to the amount of injected resin under back pressure, so the filling state of the metering cylinder can be accurately determined. Controlled weighing is performed accurately and weighing accuracy is significantly improved. Furthermore, since the resin for injection is rapidly preheated using a dielectric heating device before injection, the heat curing time and molding cycle are shortened, improving workability, and by compressing the resin before preheating, preheating is efficient and uniform. This can further shorten the preheating time and improve the quality of the molded product. Furthermore, if the resin is supported while being rotated in the dielectric heating device, preheating can be performed more uniformly, improving efficiency and quality.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an embodiment of the plastic molding apparatus according to the present invention, and is shown for explaining the plastic molding method according to the present invention, and FIGS. FIG. 2 is a schematic front view thereof, FIG. 3 is a schematic front view of another embodiment, FIG. 4 is a plan view of a roller opening/closing mechanism applied to both of these embodiments, and FIG. 5 4 is a front view from A in FIG. 4, FIG. 6 is a schematic vertical sectional view of another embodiment, and FIG. 7 is a BB sectional view in FIG. 6. 5, 6... Mold, 7... Injection pipe, 7a... Supply hole, 9... Supply cylinder, 20... Shutoff valve, 2
1...Measuring cylinder, 22...Plunger, 28
...Dielectric heating device, 28a, 28b...Electrode, 2
9... Resin, 31... Injection cylinder, 32... Plunger, 33, 34... Roller.

Claims (1)

[Scope of Claims] 1. The resin charged into the supply cylinder is pushed into the measuring cylinder, compressed and measured between the plunger of the measuring cylinder which is retracted to a predetermined position by applying back pressure, and the resin is pushed in until the deadline. After that, the resin is further compressed with the plunger of the metering cylinder, and then the metering cylinder is moved to extrude the compressed resin into the dielectric heating device to preheat it.The resin is then supplied to the mold injection pipe and molded with the injection cylinder. A plastic molding method characterized by injection into a mold. 2. A supply cylinder equipped with a resin receiving port and a plunger for pushing, a dielectric heating device equipped with a high-frequency electrode and a resin support member that can be opened and closed, and a cylinder configured to selectively face either the supply cylinder or the dielectric heating device. a movably supported metering cylinder having a plunger for compressing, metering and extruding resin;
A resin shut-off mechanism that can be opened and closed is disposed between the supply cylinder and the metering cylinder, and a plunger head is movably connected to a resin injection pipe for a mold having an inlet for receiving resin supplied from the dielectric heating device. 1. A plastic molding device characterized in that it is provided with an injection cylinder.