JPH0346891Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a press molding machine for press-molding a molten thermoplastic resin supplied onto an open mold surface by clamping the resin with a mold.

[Conventional technology and its problems]

In a conventional thermoplastic resin molding machine, as shown in FIG. An injection method is known in which molten resin is injected under high pressure and the molten resin is cooled in contact with molds 3 and 5 to form the mold.

In this type of molding machine, since the molten resin is press-fitted into the cavity 7, the resin is oriented and residual strain remains in the molded product, which tends to cause deformation such as twisting and distortion in the molded product. Strong distortion remains and becomes a physical weakness. Further, it is necessary to apply a large pressure to inject the resin into the cavity 7, which increases the size of the apparatus. Furthermore, as the molten resin shrinks in volume as it cools, a slight gap may be formed between the upper mold 3 and the resin surface, which may cause the molded product to become curved or have a rough surface. becomes.

In order to improve the above-mentioned drawbacks, a press molding machine as shown in FIGS. 9a and 9b has been proposed. This is done by keeping the upper mold 3 and the lower mold 5 apart from each other by a large distance as shown in FIG. After the molten resin 6 is supplied to a predetermined area of the press molding surface of the lower mold 5 and the nozzle 4 is retreated, the upper and lower molds 3 and 5 are pressed together as shown in FIG. 9b. It is designed to be molded.

However, this press molding machine has a problem in that it takes time to supply the molten resin 6 through the resin supply nozzle 4, which increases the cycle time.

Therefore, as shown in FIGS. 10a and 10b, a hot runner 8 serving as a resin supply path is provided in the lower mold 5, and the hot runner 8 is opened approximately at the center of the press molding surface 5A of the lower mold. A press molding machine has been proposed in which molten resin 6 is supplied to the press molding machine. Note that FIG. 10a is a sectional view of the press molding machine when the molten resin 6 is being supplied, and FIG. 10b is an enlarged sectional view showing a part of the upper and lower molds when the molds are clamped.

However, in the press molding machine shown in Fig. 10,
The resin supply port 8A of the hot runner 8 is provided with a piston 8B that opens and closes the supply port 8A according to the pressure difference within the hot runner 8.
A and the tip of the piston 8B form part of the press molding surface 5A of the lower mold 5, and come into contact with the resin surface during press molding. As a result, there was a problem in that flow marks were left on the molded product where it was in contact with these 8A and 8B, resulting in poor appearance. In addition, although the supply port 8A and the piston 8B are at high temperatures, the molded product being clamped is in contact with them even during mold clamp cooling, so uneven cooling may cause the supply port 8A, piston 8B of the molded product to Another problem was that the gloss of the contact area with the piston 8B was different from that of the surrounding area.

The present invention was devised in view of the problems of the prior art, and it is an object of the present invention to provide a press molding machine that can produce press molded products with good appearance in a short period of time.

[Means for solving problems]

Next, the present invention will be explained with reference to drawings (FIGS. 1 to 3) showing embodiments of the present invention.

A resin supply path that opens toward a gap C1 formed between press molding surfaces 44 and 46 of upper and lower molds 43 and 45 of a press molding machine, and supplies molten resin to the gap C1 between the press molding surfaces 44 and 46. A hot runner 30 is provided. The opening 30A of the hot runner 30 to the gap C1 is connected to the upper and lower molds 43, 45.
It is provided at a position that is closed by the sliding movement of the upper mold 43 or the lower mold 45 when the resin is clamped by the mold.

[Effect]

During mold clamping, the upper mold 43 descends and closes the opening 30A of the hot runner 30, so the resin press-molded by the upper and lower molds 43, 45 is mixed with the resin in the hot runner 30 and the hot runner opening 30.
It will be in a state where it is reliably separated from A.

〔Example〕

Next, a first embodiment of the present invention will be described based on FIGS. 1 to 6.

FIG. 1 is a diagram showing the overall configuration of a press molding apparatus using a press molding machine according to the present invention, in which an extruder 10
The resin extruded in a molten state is temporarily stored in an accumulator 20, and is supplied into a press molding machine 40 via a hot runner 30, which is a resin supply path. The reference numeral 22 is a hydraulic unit for slidingly operating the piston 21 in the accumulator 20, and the reference numeral 24 is a kettle provided in the middle of the hot runner 30, which controls the supply and stopping of resin into the press molding machine 40 to the accumulator 20. It is controlled in cooperation with the In FIG. 1, the press molding machine 40 is shown with the upper die omitted.

FIG. 2 shows a longitudinal cross-sectional view of the press molding machine 40, in which an upper mold 43 attached to an upper platen and a lower mold 45 attached to a lower platen are arranged facing each other, and are driven by hydraulic or motor drive. This allows the upper mold 43 to slide in the vertical direction of the arrow in FIG. Press molding surfaces 44 and 46 are formed on opposing surfaces of the upper and lower molds 43 and 45, and are uneven surfaces that match the outer peripheral shape of the molded product. By pressurizing the molding surfaces 44 and 46, a predetermined press-molded product can be obtained.

The hot runner 30 is composed of a cylindrical hot runner block 32 and a heater 34 provided around the hot runner block 32. The hot runner 30 is made up of a cylindrical hot runner block 32 and a heater 34 provided around the hot runner block 32. It is designed to be supplied to the gap C1 sandwiched between 46 and 46. The hot runner 30 penetrates the side wall 45A of the lower mold 45 and press-molding surfaces 4 of the upper mold 43 and the lower mold 45.
4 and 46, and a second
As shown in the figure, molten resin 12 is supplied. The opening 30A of the hot runner is
It is provided at a position above the lower edge 44A of the side wall surface 43A of the upper mold 43 when the mold is clamped (see FIG. 3 and FIG. 6). As a result, the opening 22A of the hot runner is closed. Side wall surface 4 which is the sliding surface on the hot runner side of the upper mold 43
3A is the hot runner opening 30A during mold clamping.
A recess 43B is formed at a position opposite to the recess 43B to ensure that when the upper mold 43 is lowered to cut and separate the molten resin at the hot runner opening 30A position, the recess 43B
The presence of B makes it difficult for the molten resin 12 in the hot runner 30 to come into contact with the mold 43 during mold clamping. Also, when clamping the mold, use the accumulator 20.
to lower the resin pressure inside the hot runner 30,
By retracting the resin end face 12A in the hot runner opening 44A in the direction of the arrow as shown in FIG.
Care is taken so that the upper mold 43 does not come into contact with the upper mold 43.

Next, the operation of the press molding machine according to this embodiment will be explained in the fourth section.
This will be explained with reference to FIGS.

First, as shown in FIG. 4, the upper mold 43 is slid upward to be separated from the lower mold 45 to create a gap between the press molding surfaces 44 and 46 so that the molten resin 12 can be smoothly supplied. Form C1 in advance. At this time, the opening 30A of the hot runner 30 opens toward the gap C1 between the press molding surfaces 44 and 46. Next, the pot 24 is opened and the accumulator 20 is operated to supply the molten resin 12 to the gap C1 between the press molding surfaces 44 and 46 via the hot runner 30, as shown in FIG. As shown in FIG. 5, when the supply of the molten resin 12 into the gap C1 is completed, the upper mold 43 is lowered. As shown in FIGS. 3 and 6, the upper mold 43 closes the hot runner opening 30A and pressure-forms the resin 12 located between the press molding surfaces 44 and 46 into a predetermined shape. When the upper mold 43 reaches the position where it closes the hot runner opening 30A, the accumulator 20 is operated to slightly lower the resin pressure inside the hot runner 30, and as shown in FIG. The upper mold 43 is pulled back so that the tip of the molten resin does not come into contact with the upper mold 43. When the predetermined mold clamping time has ended and the resin (molded product) has solidified, the upper mold 43 is raised and the molded product is taken out. By repeating the same operations as described above, molded products can be manufactured one after another.

The embodiment described above has the following effects.

Since press molding is performed using the upper and lower molds 43 and 45, uniform pressure is applied to the resin (molded product) surface by the press molding surfaces 44 and 46 until the resin solidifies, so there is no deformation and surface roughness is achieved. Small molded products can be obtained.

Since the high pressure required for injection molding is not required, the hydraulic unit 22 can be made smaller.

Since the resin is supplied into the press molding machine 40 by the hot runner 30, the cycle time can be shortened compared to the conventional example (see FIG. 9) which uses the resin supply nozzle 4.

Since the resin to be press-molded can be reliably separated from the molten resin in the hot runner opening 30A and the hot runner 30, a press-molded product with a good appearance and no traces such as flow marks on the surface can be obtained. Further, since the resin (molded product) that is clamped is less susceptible to the effects of heat from the hot runner 30, the resin (molded product) solidifies more quickly and the time required for mold clamping can be shortened.

FIG. 7 is a sectional view of a main part of a second embodiment of the present invention.

In the first embodiment, the upper mold 43 can be slid vertically relative to the lower mold 45, but in this embodiment, the lower mold 45 can be moved vertically relative to the upper mold 43. It is designed to be able to slide in any direction. Note that the reference numeral 45B is the reference numeral 43 of the first embodiment.
A recessed part shown by B has a similar function, and the lower mold 45
It is set in. The rest is the same as the first embodiment, and the same reference numerals are used to omit the explanation.

[Effect of idea]

As is clear from the above description, according to the present invention, a molded product with an extremely good appearance can be obtained in a short time.

[Brief explanation of drawings]

FIG. 1 is a plan view showing the overall configuration of a press molding apparatus using a press molding machine according to the present invention, and FIG. 2 is a longitudinal sectional view of the first embodiment of the present invention, taken along the line shown in FIG. 1. 3 is an explanatory diagram showing the operating state of the first embodiment, and FIGS. 4 to 6 are explanatory diagrams explaining the operating state of the first embodiment of the present invention. 7 is a longitudinal sectional view of another embodiment of the present invention, and FIGS.
Figure 0 shows a conventional molding machine, Figure 8 is a sectional view of an injection molding machine, Figure 9a is a sectional view of a press molding machine, and Figure 9b is a partial sectional view of the mold during clamping. ,
Fig. 10a is a sectional view of another press forming machine;
Figure b is a partial sectional view of the mold during clamping. 12... Molten resin, 20... Accumulator,
30...Hot runner, 30A...Hot runner opening, 32...Hot runner block, 40...
...Press molding machine, 43...Upper mold, 43B...Recess, 44, 46...Press molding surface, 45...Lower mold, 45A...Lower mold side wall.

Claims (1)

[Scope of utility model registration request] A pair of molds consisting of an upper mold and a lower mold each having a press molding surface formed on opposing surfaces, and an opening toward a gap formed between the press molding surfaces by separating the upper and lower molds, A press molding machine comprising a resin supply path for supplying molten resin to the gap between the press molding surfaces, and clamping the mold by upper and lower molds after the molten resin is supplied to the gap between the press molding surfaces, A press molding machine characterized in that the opening of the resin supply path to the gap between the press molding surfaces is formed at a position where it is closed by an upper mold or a lower mold when the mold is clamped.