JPS6141519A - Tip heater apparatus of hot runner for molding synthetic resin - Google Patents

Abstract

PURPOSE:To make it possible to prevent the abrasion due to a flowing melted resin thereby prolonging the life of a heater function, by arranging a stepped tip heater to extend to the forward end of the inside of a cone section without exposing the heater. CONSTITUTION:A stepped heater 7 of a heater material H in the shape of a semicircle in cross section has three step sections (a), (b), (c) whose crosssectional areas are successively decreased to change the electric resistance. The tip of the step section having the smallest crosssectional area is turned 180 deg. to be overlapped to form an arrow in the shape of a circle, an insulating material R is placed in the overlapped part, and the whole body is inserted in a small through- hole section 9 of a cone section 2a to extend into the farmost tip of the cone section 2a. A hot runner main body 1 is provided with heat effective circumferentially via a cylindrical trunk 3 by a heater as well as heat effectively through the circumferential surface of the cone section 2a from the stepped heater 7 in the direction in which the cone section 2a is extended near a gate section of a mold.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a chip heating device for a hot runner for synthetic resin molding.

(Prior Art) Conventionally, a chip heating device for a hot runner for molding synthetic resin of this type has a configuration shown in FIG. To explain the drawings, reference numeral 1 denotes a hot runner main body having a roughly cannonball shape, which includes a conical part 2 and a cylindrical body part 3 and has a body heater 4 built therein, and 5 a sharp end of the conical part 2. A chip heater formed to protrude is shown. This chip heater 5 has a special structure in which a substantially semicircular heater wire is bent 180 degrees and subjected to insulation treatment 6, and is operated by thermoplastic synthetic resin injection molding by the action of a controller (not shown). Each time, the chip heater 5 generates heat to melt the synthetic resin at the gate that communicates with the mold cavity, opening the gate to enable injection molding operations, and then stopping the heat generation of the chip heater 5 at the end of the injection molding operation. Alternatively, the temperature may be lowered to cool and solidify the synthetic resin in the gate section, thereby closing the gate.

Therefore, there is no risk that the molten resin flowing through a part of the runner will be constantly heated in the outer peripheral direction of the cylindrical body 3 by the body heater 4 and cooled and solidified. A runnerless injection molding method called a runnerless injection molding method can be effectively implemented.

By the way, in this hot runner described above, since the tip heater 5 is provided at the tip of the conical part 2 to protrude outward, it is subjected to continuous rubbing action of the resin when the molten resin is injected and distributed. When a chip heater 5 having relatively low strength is used, there is a problem that it is often worn out and cannot be used for a long period of time.

(Summary of the Invention) The invention was made by focusing on a point on paper, and the chip heater is arranged as a stepped heater so as to face the inner tip of the conical part without exposing it to the outside. This prevents the rubbing effect of the molten resin in circulation and is expected to extend the life of the heater function. It is also suitable for injection molding operations of special thermoplastic resins containing fillers, glass fibers, etc. An object of the present invention is to provide a chip heating device for a runner.

(Example) do.

Note that the same or equivalent parts as in the conventional example are represented by the same reference numerals, and detailed explanation thereof will be omitted.

Reference numeral 7 indicates a stepped heater arranged along the inside of the conical part 2a, and is arranged in a small passage part 9 continuous to the front of a hollow part 8 with a hole structure provided in the central axis direction of the hot runner body 1. It is set up.

This stepped heater 7 uses a heater material H having a semicircular cross section in three stages a, b, c2! il- gradually reduces the cross-sectional area and changes the electrical resistance, and the tip with the smallest cross-sectional area is folded back 180 degrees to overlap the whole into a circular cross-sectional shape, and the overlap is made narrower. Insulating material R is interposed.

The entire part is inserted into the small passage 9 of the conical part 2a and faces deeply into the tip of the conical part 2a.

S is a temperature sensor provided as necessary, l is one lead wire of the body heater 4, and the other is connected to the body ground through the hot runner main body 1. Reference numeral 10 indicates the lead wires of the stepped heater γ.

Since the hot runner main body 1 has a configuration on paper, effective heat is supplied by the body heater 4 in the circumferential direction via the cylindrical body 3, and the conical part 2a near the gate part of the mold faces the hot runner main body 1. In this direction, the heat from the stepped heater 7 is transmitted through the circumferential surface of the conical portion 2b, and acts extremely effectively to supply heat.

In particular, in the gate part, which is an extremely narrow conical part 2a whose tip faces out, the useful heater 7 is installed in a step-wise manner, so that heat can be supplied extremely quickly and effectively. At the same time, the stepped heater 7 is not directly rubbed by the hot molten resin flowing around it, resulting in wear and tear.

It can withstand long-term use without any inconveniences such as wear and tear.

Next, the structure and operation when installed in the mold shown in FIGS. 4 and 5 will be explained.

In the drawing, 11 is a distributor hole for the molten resin injected from an injection molding mechanism (not shown), 12 is a part of the runner in which the hot runner main body 1 is installed vertically, 13 is the gate of cavity C, and 14 is the runner hole. The hot runner main body 1 is split vertically by a steady rest pin provided at the front part of the section 12.
The hot runner main body 1, which holds the front part of the hot runner and holds the base 1a firmly, reduces the inconvenience of vibration in the runner part 12 during injection molding operations.

By the way, the body heater 4 of the hot runner main body 1 is
The winding state of the nichrome wire is made denser or denser depending on the position, thereby controlling the level of heat supplied to the cylindrical body 3.

In other words, the number of turns of the nichrome wire is increased for the thin P that contacts the steady rest pin 14, and in consideration of the thermal energy escaping through the pin 14, the molten resin of the pin 14 is Care must also be taken to ensure that the necessary amount of heat can be supplied. Furthermore, the number of turns of the nichrome wire is increased in the narrow P2 near the distributor hole 11 in order to maintain melting of a larger amount of molten resin than necessary facing the distributor hole 11.

Of the dense and dense structure of the number of turns of this nichrome wire, the part P corresponding to the steady rest pin 14 is varied in order to effectively supply heat. Sufficient supply is not possible with only a single body heater 4. This is because in order to supply sufficient heat to the tip of the conical portion 2, it is also necessary to supply heat to the steady rest pin 14 side, which requires excessive winding.

This is because a temperature high enough to burn out the molten resin is generated, making smooth runnerless injection molding of the resin impossible.

In this embodiment, the stepped heater 7 is provided separately from the body heater 4, so that the temperature of the resin near the gate portion can be centrally controlled by the stepped heater 7.

Incidentally, the stepped heater 7 preferably has a multi-stage configuration such as two-stage or three-stage configuration, but it goes without saying that it also includes a case where the heater 7 changes gradually as much as possible.

(Effects) According to the present invention, the stepped heater provided in the conical part of the hot runner main body does not come into direct contact with the outside, and therefore can withstand long-term use and can prevent solid materials such as glass fibers. It is suitable for molding the blended thermoplastic synthetic resin, and since a stepped heater with a multi-stage structure is provided inside the conical part, the tip of the stepped heater can reach the tip of the conical part sufficiently. , has the effect of quickly and effectively supplying heat at the required temperature.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional side view showing an embodiment of a hot runner for molding synthetic resin equipped with a chip heating device according to the present invention, FIG. 2 is an enlarged sectional view of the same upper step heater, and FIG. A front view of the same as above, Fig. 4 is a longitudinal cross-sectional explanatory view showing the main structure when assembled into a mold for molding synthetic resin, Fig. 5 is a cross-sectional explanatory view of the steady rest pin portion of the same as above, and Fig. 6 is a vertical side view of a conventional example. 1...Hot runner main body 4 including conical parts 2, 2a and cylindrical body part 3...Body heater 5...・Chip heater 7...Stepped heater 8...Hollow part 12...Runner part 14...Steady rest pin R・......Insulating material S...Sensor h...Heater wire H...Heater material section Tomb section To section To w& faction

Claims (1)

[Claims] A cylindrical body is provided next to the conical part, and the hot runner body has a roughly cannonball shape with a built-in heater inside. A chip heating device for a hot runner for synthetic resin molding, which heats a chip in a conical part by varying the electrical resistance and disposing a stepped heater formed by folding back the tip.