JPS6012210B2 - Plasticizing device for injection molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an injection molding machine used for molding synthetic resin, and particularly to an apparatus for plasticizing pellets.

In the plasticizing device of the injection molding machine that has been commonly used, the inner diameter of the heating cylinder and the outer diameter of the plasticizing screw flight are approximately equal, and the rear end of the supply softening zone where the hopper is attached The gap between the inner diameter of the heating cylinder and the outer diameter of the valley of the plasticizing screw, which extends from the measuring zone to the metering zone, is also formed by the groove depth of the plasticizing screw.

For this reason, in the case of an injection molding machine with a large injection volume, the outer diameter of the plasticizing screw becomes large and the gap between them becomes large, which makes it difficult to plasticize plastic pellets with normal particle size. However, in a small injection molding machine having a plasticizing screw with an extremely small injection amount of 1 to 10 blocks, the screw groove volume in the melting range, that is, the resin retention Due to the desire to reduce the volume and to increase measurement accuracy, a plasticizing screw with an extremely small outer diameter of 16 ribs or less is required, and as a result, the inner diameter of the heating cylinder and the outer diameter of the valley of the plasticizing screw must be adjusted. Since the gaps are also extremely small, it is difficult to use pellets of generally commercially available particle sizes as they are.

In order to use a pellet of normal particle size in a small injection molding machine, the groove depth in the V supply zone of the plasticizing screw needs to be at least 3 skins deep. However, when trying to design a plasticizing screw using conventional technology,
For example, if the outer diameter of the V-supply zone is 1 ship, the diameter of the valley will be 4 ribs, and the handling stress due to rotational force will become large, resulting in destruction. Furthermore, since the groove depth of the metering zone cannot be made proportionally larger, the compression ratio becomes too large as a result, making it impossible to obtain proper plasticization. Therefore, in the past, the plasticizing screw was designed within a range that did not address the above problems, and either special small-sized mugwort pellets were prepared, or ordinary pellets were ground into small particles and used.

However, such pellets are 20 to 40% more expensive than regular pellets even though they are of the same grade, making the product expensive. The present invention eliminates the above-mentioned conventional drawbacks and provides an apparatus that can sufficiently plasticize pellets of normal particle size even in an injection molding machine where the injection amount is limited to an extremely small amount.

Note that pellets come in various shapes, such as spherical, cylindrical, and prismatic, but the particle size of the pellet refers to the size of the pellet that can be transferred with a gap of at most 4 mm.
Refers to the dimension between the smallest opposing surfaces.

This invention for the above-mentioned purpose is characterized in that the inner diameter of the supply softening zone of the heating cylinder is formed larger than the inner diameter of other zones, and the supply softening zone is formed between the outer diameter of the valley of the plasticizing screw and the inner wall of the heating cylinder. The gap is made large enough to at least allow pellets to be transferred in the form of particles, and even if the gaps in other zones are made smaller than the particle size of the pellets due to plasticization, the pellets from the hopper are After the pellet begins to soften due to the heat of the heater around the heating cylinder, the gap between the inner diameter of the heating cylinder and the outer diameter of the valley of the plasticizing screw is narrowed and the pellet is transferred under pressure to the measuring section. The aim is to obtain appropriate plasticization and measurement accuracy.

The present invention will be explained in more detail below with reference to illustrated examples.

In the figure, reference numeral 1 denotes a heating cylinder having an injection nozzle at its tip, and a heater 2 is attached to the outer periphery. A plasticizing screw 3 is installed inside the heating cylinder 1 so that it can rotate and move forward and backward.

The outer diameter of the flight of this plasticizing screw 3 is extremely small, about 6 to 16 sides, and the depth of the groove formed between it and the groove becomes shallower toward the tip, similar to a normal plasticizing screw. It has been formed. Supply softening zone A of the heating cylinder 1
The inner diameter of zone B is larger than the inner diameter of the other zones B including the plasticizing and metering zones.

In addition, the groove depth in the supply softening zone A of the plasticizing screw 3 is 4 mm deeper than the minimum grain size (3 to 4 ribs) of a normal pellet a, and the outer diameter of the flight is the same in all parts. In zone B, the inner circumferential wall of the heating cylinder 1 is slid. Also, the gap 4 of the supply softening zone A formed between the inner diameter of the heating cylinder 1 and the outer diameter of the valley of the plasticizing screw 3 has a size sufficient to feed a normal pellet a, for example, the plasticizing screw The groove depth of 3 plus 1'2, which is the difference in the inner diameter between the supply V supply softening zone A and the other zone B of the heating cylinder 1, is larger than the minimum dimension of the normal pellet a. .

5 is a hopper.

In the above example, the compression appears to be too large, but when the pellet a is completely solid, the transfer force is smaller than when it is semi-molten, so there is no oversupply, and as a result, the compression ratio is large. There is no such thing as too much.

In the present invention having the above configuration, the gap 4 of the supply softening zone A is formed so that the inner diameter of the heating cylinder 1 is larger than the inner diameter of the other zones B, so that at least the pellets a can be transferred in the form of particles. Therefore, even in an injection molding machine where the outside diameter of the plasticizing screw 3 is extremely small, pellets with a normal particle size can be used as the molding material, and there is no need to arrange special pellets with a small particle size as in the past. do not have.

In addition, the product does not become expensive due to the use of ordinary pellets, and the plasticizing screw can be designed in the same way as before.

[Brief explanation of drawings]

The drawing is a schematic longitudinal sectional view showing an embodiment of a plasticizing device for an injection molding machine according to the present invention. 1... Heating tube, 2... Heater, 3... Plasticizing screw, 4... Gap, 5... Hopper, A... Supply softening zone, B... Others Zone, a...
・Berrett.

Claims (1)

[Claims] 1. The inner diameter of the supply softening zone of the heating cylinder containing the plasticizing screw with the same outer diameter of the flight is made larger than the inner diameter of the other zones, so that there is a gap between the outer diameter of the valley of the plasticizing screw and the inner wall of the heating cylinder. 1. A plasticizing device for an injection molding machine, characterized in that a gap in a supply softening zone formed in the plasticizing zone is made large enough to at least transport pellets in granular form.