JPH02202416A - Preplasticizing type injection molding machine - Google Patents

Abstract

PURPOSE:To enable constitution of the above machine without providing a check valve causing retention of a plasticizing material, by a method wherein a feed path is opened directly before a front end of an injection plunger so that the feed path is made cloggable directly after a forward movement of the injection plunger. CONSTITUTION:In constitution where a feed path 30 is opened almost flush with a front end of an injection plunger 22, a plasticizing material fed to a resin rich area from a preplasticizing cylinder 28 through the feed path 30 cannot help being caused to flow in the direction of a nozzle. In other words, there is no room to flow rightward a plasticizing material from an opening of the feed path 30 and only a rightward flow, that is, the flow in the direction of the nozzle is generated. Then, when a pressurizing medium such as hydraulic oil is fed to an injection cylinder 24 from a flow path 36, the hydraulic oil pushes rightward the injection plunger 22 and moves forward. In other words, there is a room generating only a unidirectional (direction of the nozzle) flow. Therefore, the plasticizing material which has been fed to a resin rich area 18 through the feed path 30 does not remain, but flows in the direction of the nozzle according to a forward movement of the injection plunger 22 and injected to the cavity of a mold through the nozzle 32.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pre-plastic injection molding machine that performs plasticization and injection of a plastic material in separate processes.

[Conventional technology]

In injection molding, a plastic material such as a resin (Plasti-2) is heated and melted, injected under pressure into a mold cavity, and after cooling, is taken out from the cavity as a molded product. Recently, new materials such as ceramics have also been plasticized and molded using water, resin, etc. as inclusions. In the molding process, it is necessary to mold a molded product of a constant quality with no variation, especially in the technologically advanced and precise industry. The need is high.

Therefore, in the conventional technology, mechanical molding conditions (injection pressure, injection speed, injection amount, heating temperature, screw rotation speed, back pressure, (holding pressure, etc.) are computer-controlled using closed-loop control.

The conditions for moving the plastic material to uniformly heat, melt, and plasticize the plastic material and the conditions for moving the plastic material for injection do not necessarily match, but in an in-line screw type injection molding machine, the conditions for moving the plastic material Since plasticization and injection are performed in the same process, it is not easy to control the mechanical molding conditions, and the range of molding conditions is narrow.

Therefore, it is difficult to maintain optimal conditions and it is difficult to maintain constant quality of molded products.

On the other hand, in a pre-plastic type injection molding machine, a pre-plastic mechanism is separately provided, and the plastic material is plasticized by this pre-plastic mechanism. With this configuration, plasticization and injection can be performed in separate processes, and the conditions for moving the plastic material for plasticizing and the conditions for moving the plastic material for injection are
Can be controlled individually. Therefore, mechanical molding conditions can be easily controlled and molding conditions can be set over a wide range. Therefore, optimal conditions can be maintained accurately, and molded products of constant quality without variation can be molded.

[Problem to be solved by the invention]

In a pre-plastic type injection molding machine, the plastic material plasticized by the pre-plastic mechanism is supplied from the pre-plastic ring of the pre-plastic mechanism to the resin reservoir at the front of the plunger cylinder via a supply path. As the plastic material is supplied to the resin reservoir, the injection plunger is retracted, and when the resin reservoir is fully supplied with plastic material and the injection plunger is retracted to the initial position, the supply of plastic material to the resin reservoir is stopped. .

Then, the injection plunger moves forward, and as the injection plunger moves forward, the plastic material is pressurized and injected from the resin reservoir into the mold cavity through the nozzle.

Here, the plastic material pressurized as the injection plunger moves forward has a higher pressure than the plastic material in the pre-plastic ring. Then, the plastic material in the resin reservoir flows into the supply channel,
There is a risk that the flow will flow back into Puri Plus Ring. Therefore, a check valve is provided in the supply path to prevent backflow and to ensure that a certain amount of plastic material is accurately injected from the resin reservoir into the cavity.

Usually, a check valve is attached to the opening of the supply path to the resin reservoir. However, in order to install the check valve, the shape of the supply channel near the opening has to become complicated, and plastic material tends to accumulate near the complicated supply channel opening. If this occurs, it becomes difficult to maintain a constant quality of the molded product. Furthermore, if the plastic material stays near the opening of the supply channel, it is not easy to replace the plastic material for changing colors, and it takes a long time to change colors, which reduces work efficiency.

Furthermore, the check valve must be replaced periodically due to wear, damage, etc., and maintenance of the check valve is not easy.

An object of the present invention is to provide a pre-plastic injection molding machine that can be configured without providing a check valve that causes retention of plastic material.

[Means to solve the problem]

In order to achieve this object, in the present invention, the supply path for supplying the plastic material from the pre-plastic mechanism to the resin reservoir opens substantially flush with the front end of the injection plunger in the initial position. That is, the supply path opens immediately before the front end of the injection plunger so that it can be closed immediately after the injection plunger moves forward.

〔Example〕

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

As shown in FIG. 1, according to the present invention, the pre-plastic type injection molding machine 1O is configured with a plunger injection method, and supplies the plunger cylinder 14 around which the band heater 12 is wound, and the hole and hole 16. A pre-plastic mechanism 20 that heats and melts a plastic material, such as a resin, and sends the molten resin to a so-called resin reservoir 18 at the top of a heating cylinder.
And, press the injection plunger 22! The injection cylinder 24 is movably housed. In the embodiment, the pre-pla mechanism 20 is constructed of a screw pre-plastic type having a pre-plus screw 26, but it may be a plunger pre-plastic type using a pre-pla plunger instead of the pre-plus screw.

The pre-pla mechanism 20 has a known configuration, and a band heater 12 is also arranged around the pre-pla ring 28 of the pre-pla mechanism. The resin supplied to the hopper 16 is kneaded by the rotation of the pre-plus cream 26,
Heated and melted. Then, the plastic material heated, melted and pressurized by the rotation of the Pre-Plastic Screw 28 is transferred to the resin reservoir 18 at the front of the plunger cylinder via the supply path 30 between the Pre-Plastic ring 28 and the plunger cylinder 14. sent to.

In FIG. 1, the injection plunger 22 is in the retracted position;
In other words, it has retreated to its initial position. and.

As can be clearly seen from FIG. 1, with respect to the injection plunger 22 in the initial position, the supply passage 30 opens substantially flush with the front end of the injection plunger. In other words, the supply path 30
is opened just before the front end of the injection plunger so that it can be closed immediately after the injection plunger 22 moves forward. Here, "evenly aligned" refers to a state where they match completely or are shifted left and right by about a few square feet.

In this way, in the configuration in which the supply path 30 opens substantially flush with the front end of the injection plunger 22, the pre-plastic injection ring 28
The plastic material supplied from the supply channel 30 to the resin reservoir 18 has no choice but to flow in the nozzle direction, that is, there is no room for the plastic material to flow to the right from the opening of the supply channel 30.
Flow only occurs to the left, that is, toward the nozzle.

Then, when a pressurized medium, for example pressurized oil, is supplied to the injection cylinder 24 from the wave path 3B, the pressurized oil pushes the injection plunger 22 to the left and moves it forward. As mentioned above, there is room for flow to occur in only one direction (nozzle direction), so the plastic material supplied to the resin reservoir 18 via the supply path 30 does not stagnate and is transferred to the injection plunger 2.
2 flows toward the nozzle, and is injected into a mold cavity (not shown) through the nozzle 32.

In other words, according to the present invention, the plastic material in the resin reservoir 18 is smoothly injected into the cavity of the mold in sequence from the old plastic material supplied to the resin reservoir first to the newly supplied plastic material. In addition, as will be described later, the shape of the vicinity of the opening of the supply path 30 is simplified, so that the plastic material does not accumulate near the opening. Variations in the quality of the molded product due to stagnation are less likely to occur, and the quality of the molded product can be maintained constant. In addition, the plastic material can be easily replaced for color change, and color change can be done quickly and easily, so high workability can be ensured.

Here, since the supply path 30 opens just before the front end of the injection plunger 22, as can be clearly seen from FIG.
It is closed immediately after the injection plunger 22 moves forward. Therefore, there is no time for the plastic material in the resin reservoir 18 to flow into the supply path 30, and backflow of the plastic material into the pre-plastic ring 28 is sufficiently prevented.

Therefore, there is no need to provide a check valve in the supply path 30.

Check valve can be omitted.

Unlike known configurations in which the opening shape of the supply path becomes complicated due to the attachment of the check valve, in the present invention, the check valve is omitted, so the opening shape of the supply path is simplified. Therefore,
There is no risk of the plastic material remaining near the opening of the supply path, and the number of parts is reduced by omitting the check valve, and the structure is simplified, so the injection molding machine 10 can be produced at low cost. Furthermore, since no check valve is used, there is no need to consider maintenance.

In the known pre-plastic type injection molding machine, the injection plunger is located at the opening of the supply channel even in the forward position.
The injection plunger moves forward and injects the plastic material from the resin reservoir, and the plastic material flows from the pre-plastic ring to the supply channel. When the resin reservoir is newly supplied through the plastic material, the injection plunger is pushed back to the initial position.

In contrast, in the present invention, the opening of the supply path 3o is closed immediately after the injection plunger moves forward, so that the injection plunger 2
2 cannot be pushed back.

Therefore, in this invention, the pressurized medium, for example,
Pressurized liquid is supplied to the injection cylinder 24 through the flow path 38, thereby retracting the injection plunger 22 to the initial position.

The above-mentioned embodiments are for illustrating the present invention, and do not limit the present invention in any way, and all modifications and modifications within the technical scope of the present invention are included in the present invention. Needless to say, it will be done.

For example, the opening of the supply passage 30 may not be a perfect circle, but may have a shape such as an ellipse or a long hole with the long side perpendicular to the axis of the injection plunger 22. With this configuration, the supply passage can be quickly blocked. It becomes possible.

〔Effect of the invention〕

As described above, according to the present invention, since the supply channel is closed immediately after the injection plunger moves forward, there is no room for the plastic material in the resin reservoir to flow into the supply channel, and backflow to the pre-plastic syringe is prevented. Therefore, a check valve can be omitted. In addition, since the check valve is omitted, the opening shape of the supply channel is simplified, and there is no risk of the plastic material remaining near the opening of the supply channel.The number of parts is reduced by omitting the check valve. Since the structure is simplified, injection molding machines can be produced at low cost. Furthermore, since no check valve is used, there is no need to consider maintenance.

Since the supply channel opens almost flush with the front end of the injection plunger, the plastic material supplied from the pre-plastic ring to the resin reservoir via the supply channel has no choice but to flow toward the nozzle, and the plastic material flows into the resin reservoir. The plastic material is pushed from the old plastic material previously supplied to the resin reservoir to the newly supplied plastic material, and is smoothly injected into the cavity of the mold one after another, without causing any accumulation of plastic material. As mentioned above, the opening shape of the supply channel is simplified, and there is no possibility that the plastic material will accumulate near the opening of the supply channel.Therefore, there will be variations in the quality of the molded product due to the accumulation of plastic material. To <<,
The quality of molded products can be maintained at a constant level.

Furthermore, the plastic material can be easily replaced for color change, and color change can be performed quickly and easily, ensuring high workability.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of the main parts of the pre-plastic type injection molding machine according to the present invention at the initial position (retracted position). FIG. 2 is a partial vertical cross-sectional view of the main parts of the pre-plastic type injection molding machine during forward movement. It is a front view. 10: Pre-plastic injection molding machine, 14 nib run cylinder, 18: resin reservoir, 20: Pre-plastic mechanism 22
: injection plunger, 24: injection cylinder, 2B=puri-plus creu, 28: pre-plus cylinder, 30: supply passage, 32: nozzle, 36.38: flow passage.

Claims (2)

[Claims] (1) A supply path that communicates between the pre-plastic cylinder and the resin reservoir at the front of the plunger cylinder and supplies plastic material from the pre-plastic mechanism to the resin reservoir opens almost flush with the front end of the injection plunger in the initial position. Pre-plastic type injection molding machine. (2) The supply path, which communicates the pre-plastic cylinder and the resin reservoir at the front of the plunger cylinder and supplies plastic material from the pre-plastic mechanism to the resin reservoir, can be closed immediately after the injection plunger moves forward, so that the supply path is located just before the front end of the injection plunger. A pre-plastic injection molding machine with an opening.