JPH0374892B2 - - Google Patents

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a pressure holding device for an injection molding machine, which is composed of a mold clamping unit and an injection unit, and is attached to the mold clamping device of an injection molding machine. It is widely used.

(Prior art) As the prior art related to the present invention,
There is a publication of No. 45153 "Pressure holding device for injection molding machine".

As shown in Fig. 3, this is a screw type injection molding machine in which a cylinder 21 and a cylinder head 22 attached to the tip thereof are connected so as to be openable and closable by a valve 23, and the cylinder head 22 is equipped with a hydraulic cylinder 26. A pressure holding device for an injection molding machine to which a pressure holding cylinder 25 is attached is disclosed.

This pressure holding device is designed to shorten the time required for one cycle of injection, holding pressure, cooling, or plasticization in an injection molding machine, or to reduce the long holding time when molding thick-walled products. In order to prevent resin leakage from the nozzle and to relieve pressure from the hot runner mold, the cylinder head 22 and the cylinder 21 are separated by the valve 23 in the pressure holding process of the conventional injection molding machine, and the cylinder head The pressure inside the mold is maintained by the pressure holding cylinder 25 provided at 22, and at the same time, the screw 27 rotates within the cylinder 21 and starts plasticizing. It is completely separated from other operations and shortens the one cycle time.

The details of each step of this one cycle are shown in FIG. 4, where A shows the steps of a general injection molding apparatus consisting of a mold clamping unit and an injection unit.

The operation on the mold clamping unit side is shown in solid lines in parentheses, and the operation on the injection unit side is shown in white in parentheses.

As one cycle of the molding equipment, on the mold clamping unit side, after the mold is clamped, the mold is injected from the injection device, followed by a pressure holding process, and then the mold clamping unit cools, and in parallel, plasticization is performed in the injection unit. Furthermore, in the mold clamping unit, after cooling, one cycle of mold opening, mold removal, and mold clamping is performed.

B in Fig. 4 is a process diagram of the cylinder of the injection unit provided with a pressure holding cylinder 25 (Jikkosho).
57-45153), and compared to A, holding pressure and plasticization are performed in parallel.

(Problems to be Solved by the Invention) However, the pressure holding cylinder 2 for an injection molding machine having the above structure
5. The hydraulic cylinder 26 is directly fixed to the cylinder 21, and since there is a time difference in the time until plasticization is completed depending on the resin material, plasticization takes a long time, and if the plasticization time is longer than the cooling time, the maintenance Because plasticization begins under pressure, the mold opening time is faster, resulting in a shorter molding cycle, but
If the cooling time is long, there is no need for a pressure holding device, and furthermore, the cylinder head tip 24 cannot be retracted from the mold until the resin completes the gate sealing, and therefore the molding cycle time is shortened. The problem is that it cannot be shortened.

The present invention provides an injection molding machine comprising a plurality of mold clamping units and one injection unit, which can shorten the molding cycle time regardless of the length of the plasticizing time and cooling time of the resin, which is the problem mentioned above. The purpose is to provide opportunities.

[Structure of the invention]

(Means for solving the problems) The technical measures taken to solve the above technical problems are as follows. That is, the present invention provides an injection molding machine comprising an injection unit and a mold clamping unit, in which a pressure holding device comprising a hydraulic cylinder and a pressure holding cylinder is attached to a fixed die plate provided on the side facing the injection unit. , the molten resin passage of the pressure holding device is capable of communicating with an opening of a cavity provided in the fixed die plate, and the hydraulic cylinder and the pressure holding cylinder are disposed approximately at right angles in the molten resin passage, A shut-off valve is disposed between the opening of the molten resin passage and the pressure holding cylinder, and after the nozzle of the injection unit comes into contact with the opening of the pressure holding device, the molten resin is discharged from the nozzle. It has a pressure holding device that is characterized by the fact that it is injected.

Furthermore, several mold clamping units with the pressure holding devices fixed to the fixed die plate are arranged in parallel, the injection units are placed on the rails, and one injection unit is moved laterally into the mold of the mold clamping unit. The molded product is formed by sequentially injecting, applying pressure holding by a pressure holding device, cooling and opening the mold, and then moving the injection unit.

(Operation) The technical means operates as follows. In other words, the nozzle of the injection unit contacts the fixed die plate and the molten resin is injected, filling the cavity, the passage of the pressure holding device, and the lower part of the pressure holding cylinder, and the hydraulic cylinder and pressure holding cylinder of the pressure holding device. acts, the resin cools in the mold, and even if the resin shrinks in the cavity, the pressure of the holding pressure cylinder supplies the shrinkage amount of molten resin, thus molding a molded product without bubbles, sink marks, etc. It is something to do.

Furthermore, since a shut-off valve is provided in the molten resin passage of the pressure holding device, in the case of a resin material with a low melt viscosity, a dripping phenomenon called drawling does not occur from the molding machine nozzle. This allows the shut-off valve to prevent backflow of molten resin. Furthermore, unlike conventional pressure holding devices, holding pressure can be applied even if the nozzles are not in contact with each other, so the injection unit can be retracted while plasticizing upon completion of injection, thereby shortening the molding cycle. In addition, the nozzle can be retracted and plasticized during the cooling time, so
This makes it possible to shorten the cycle.

In addition, when multiple mold clamping units are arranged and molding is performed with one injection unit, the injection unit can simultaneously perform the plasticizing action and lateral movement after injection is completed, reducing the time for one cycle and facilitating continuous production. is possible.

(Example) The following is a specific example of an injection molding machine with a capacity of 450 TON.
The following explains the case where the weight of the molded product is approximately 450g.

In FIG. 1, A is a mold clamping unit, B is an injection unit, and there is an injection device (not shown).

1 is a cylinder, 2 is a nozzle, 3 is a screw, and 4 is a rotary valve. 5 is a movable mold of the mold in the mold clamping unit, 6 is a fixed mold, and 7 is a movable mold of the mold in the mold clamping unit.
is a cavity, 7a is an opening of a cavity passage, 8 is a shut-off valve of the cavity, and 9 is a fixed die plate. 10 is a pressure holding device fixed to the fixed die plate 9, and this pressure holding device 10 has a hydraulic cylinder 11 attached to the fixed die plate 9 on the side where the nozzle 2 comes into contact.
A pressure holding device 10 consisting of a pressure holding cylinder 12 and a pressure holding cylinder 12 is installed, so that when the nozzle 2 comes into contact with the pressure holding device 10, the molten resin passage 13 of the pressure holding device 10 communicates with the nozzle 2, the mold clamping unit A, and the cavity 7. A shut-off valve 15 is provided on the nozzle side of the molten resin passage 13. Further, the hydraulic cylinder 11 and the pressure holding cylinder 12 are arranged so as to be able to press against the molten resin passage 13 in a substantially perpendicular direction.

In the above structure, when the nozzle 2 of the injection unit B moves forward and comes into contact with the opening 14 of the pressure holding device 10, the shutoff valve 8
and 15 are opened and resin is injected. The molten resin passes through the open valve 4 and fills the passage 13 of the pressure holding device and the cavity 7 of the mold, and also fills the lower part 16 of the pressure holding cylinder. do.

After filling the cavity, the three valves 4 and 15 are closed, and the molds 5 and 6 are opened while maintaining the pressure in the two cylinders, the hydraulic cylinder 11 and the pressure holding cylinder 12.
By cooling the cavity, the cavity is cooled and solidified, and the shrinking resin is compensated for by the pressure holding cylinder 16.

In this case, the injection unit B is separated from the mold clamping unit A by the pressure holding device 10 at the point where the injection process is completed, so that the plasticization process can be started immediately. In this way, the injection nozzle 1 constantly repeats the plasticizing process and the injection process except during forward and backward movement, and can be used extremely effectively.

This is shown in the process diagram C in FIG. In comparison with B, the pressure holding device is located in the mold clamping unit, so the pressure holding process is performed on the mold clamping unit side.

Next, as shown in FIG. 2, the mold clamping unit A
1, A2, A3... are arranged in parallel, and the injection unit B1 is moved laterally on the rails 17a, 17b. After injection into the mold clamping unit A1 from the nozzle 2, the pressure holding device 10 acts, and the mold By separating the clamping unit and the injection unit, the injection unit moves laterally on the rail, contacts the mold clamping unit A2, and performs injection, and this operation is repeated one after another.

This process diagram is shown in FIG. 4D. After mold clamping, molten resin is injected from the injection unit, the mold clamping unit progresses from holding pressure → cooling → mold opening → ejecting, and the injection unit moves horizontally at the same time as plasticizing, and after completing the horizontal movement, plasticizes. When this is completed, the mold clamping of the next mold clamping unit D1 is completed and injection is immediately performed, and the same operation is thereafter performed on D2 as well. If the cycle of three mold clamping units is P1, as shown in D, D1, and D2 in FIG. 4, three molded products are molded during P1.

In Fig. 4E, the pressure holding device shown in Fig. 4B is provided on the injection unit side as in the conventional example, and three mold clamping units are arranged.If the molding cycle in this case is P2, then P2 >P1, and comparing D and E, in the case of the embodiment, P2-P1≈20 seconds, which makes it possible to significantly shorten the process by about 20 seconds in continuous production.

[Effects of the Invention] The present invention has the following unique effects. That is,
A large number of mold clamping units equipped with pressure holding devices are arranged.
When manufacturing molded products by continuously injecting into the mold clamping unit using the injection unit on the table, the production time per piece can be considerably shortened and costs can be reduced compared to the conventional method. In addition, in the conventional type, the contact between the nozzle tip and the fixed die plate is longer due to the pressure holding process, and therefore heat transfer easily occurs between the two, causing temperature changes in the molten resin and the mold, which causes variations in quality. It is becoming.

In the present invention, the injection unit moves immediately after injection when the pressure holding device is activated, so there is no heat transfer between the fixed die plate and the nozzle tip, and the cavity is therefore thermally stable and has good quality. Molded products with no variations can be molded.

[Brief explanation of drawings]

Fig. 1 is a partially cutaway explanatory diagram of this embodiment, Fig. 2 is an explanatory diagram of the main part of a plurality of units of this embodiment arranged, and Fig. 3 is an explanatory sectional view of a conventional example. , Fig. 4 is a process explanatory diagram of the mold clamping unit and the injection unit, A to B are explanatory diagrams of the conventional example, and C is an explanatory diagram of the process of the mold clamping unit and the injection unit.
are explanatory diagrams of the present embodiment, D to D2 are explanatory diagrams of the continuous production process of the present embodiment, and E to E2 are explanatory diagrams of the continuous production process of the conventional example. A, A1, A2, A3...Mold clamping unit, B,
B1... Injection unit, 2... Nozzle, 9... Fixed die plate, 10... Pressure holding device, 11... Hydraulic cylinder, 12... Pressure holding cylinder, 17a, 1
7b...Rail.

Claims (1)

[Claims] 1. Mold clamping unit A having fixed die plate 9
In an injection molding machine consisting of a hydraulic cylinder 11 and an injection unit B, a pressure holding device 10 consisting of a hydraulic cylinder 11 and a pressure holding cylinder 12 is mounted on a fixed die plate 9 provided on the side facing the injection unit B, and the above-mentioned The molten resin passage 13 of the pressure holding device 10 can communicate with the opening 7a of the cavity 7 provided in the fixed die plate 9, and the molten resin passage 13 is connected to the hydraulic cylinder 1.
1 and the pressure holding cylinder 12 are arranged substantially at right angles,
A shut-off valve 15 is disposed between the opening 14 of the molten resin passage 13 and the pressure holding cylinder 12, and the nozzle 2 of the injection unit B is connected to the opening 14 of the pressure holding device 10. An injection molding machine having a pressure holding device, characterized in that molten resin is injected from a nozzle 2 after contact. 2 Mold clamping unit B equipped with the pressure holding device 10
2. An injection molding machine having a pressure holding device according to claim 1, wherein a plurality of injection molding units B are arranged in parallel and the injection unit B is arranged horizontally movably on a rail.