JPS61249727A - Injection molding machine - Google Patents

Abstract

PURPOSE:To block a resin flow path so that injected resin does not flow backward by making a plasticizing cylinder communicate with an injection cylinder, by providing a needle blocking the resin flow path and a sliding hole capable of moving forwardly and rearwardly. CONSTITUTION:When a needle 10 is moved backward to a B position blocking a needle sliding hole 9 from an A position blocking an outlet of a resin flow path 8 by a pulling-in action of a rod of an opening and closing cylinder 11, a plasticizing cylinder 6 is communicated with a resin storing chamber 4 of the tip part of an injection cylinder 1 through the resin flow path 8. When the needle 10 is moved forward from the B position to the A position by a protruding action of the rod of the opening and closing cylinder 11, an outlet of the resin flow path 8 is blocked through the needle 10 and a detecting part of a thermocouple 14 is held within said resin flow path 8. Then when an injection plunger 2 is moved forward through the protruding action of a rod of an injection driving cylinder 5, molten resin in the injection cylinder 1 and an injection nozzle 3 is injected and filled out in a mold without flowing backward to the resin flow path 8 and an injection processing is completed.

Description

[Detailed Description of the Invention] ←Field of Industrial Application) The present invention relates to a pre-glazing type injection molding machine that performs plasticization and injection in separate cylinders.0 (Prior art) Screw-in-line type or plunger type injection molding machine In the molding machine,
A backflow prevention ring or backflow prevention pole check pulp is installed on the injection screw or injection plunger to prevent the backflow of resin during injection. A port check valve is installed at the top of the cylinder to prevent backflow of resin during injection.In addition, in any injection molding machine, the resin temperature in the resin storage chamber at the tip of the injection cylinder is measured using a generally inexpensive sheath type. This is done using a thermocouple.

(Problem that the invention attempts to solve) However, regarding backflow prevention, the backflow prevention ring, bolts, and balls of the tsuku valve move due to the resin pressure after injection starts! Because the structure prevents resin from flowing backwards,
At the beginning of the injection process, the actual flow speed of the resin into the mold changes, and the timing of the resin passing through the gate in a multi-piece mold changes, and the way the resin flows changes.In the case of precision molding, the molded product clearly changes. The dimensions, surface condition, and condition of the product will be adversely affected. In the case of plunger-type and pre-plastic injection molding machines, resin leaks inside the injection cylinder in the former case, and in the resin flow path from the plasticizing cylinder to the injection cylinder in the latter case, but the stagnant part cannot be easily cleaned and the resin is replaced. There is an inconvenience that it takes time to change one color.

In order to measure the resin temperature, the detection part of the thermocouple is either embedded in a torpedo or the like inside the nozzle, or it is made to protrude into the nozzle. In the latter case, heat is generated due to friction between the sheath and the resin during injection, making it impossible to accurately measure the resin temperature.

SUMMARY OF THE INVENTION An object of the present invention is to provide a pre-plastic injection molding machine equipped with a needle valve mechanism that can solve the above-mentioned conventional problems at once.

(Means for solving problems). In the injection molding machine of the present invention, a resin storage chamber side wall k at the tip of the injection cylinder into which the injection plunger is fitted is provided with a resin flow path and a needle sliding hole which are concentric and have the same diameter and open opposite to each other, and At the needle sliding hole side of the cylinder tip, an m-dol that closes the resin flow path and the needle sliding hole is provided so as to be movable back and forth, and a plasticizing cylinder is connected to the resin flow path of the injection cylinder tip, The purpose is to move the plasticizing needle backward to communicate the plasticizing cylinder and the injection cylinder via the resin flow path, and to move the injection needle forward to close the resin flow path so that the resin does not flow backwards.

(Example) An example of the present invention will be described below with reference to a drawing showing a screw pre-plastic injection molding machine.

In the figure, 1 is an injection cylinder, 2 is an injection plunger, 3 is an injection nozzle, 4 is a resin storage chamber, 5 is an injection drive cylinder, 6 is a plasticizing cylinder, and 7 is a plasticizing screw.

A resin flow path 8 and a needle sliding hole 9 are provided on the side wall of the resin storage chamber 4 at the tip of the injection cylinder 1, which open to face each other.

On the side of the needle sliding hole 9 at the tip of the injection cylinder l, there is a needle 10 that closes the resin flow path 8 and the needle sliding hole 9.
This is provided so that it can be moved forward and backward by an opening/closing cylinder 11 attached to the tip of the rod.

The piston of the opening/closing cylinder 11 is provided with an operating piece 12 that extends to the outside of the cylinder toward the side opposite to the rod. The opening/closing cylinder 11 is provided with a detection section 13 (limit switch in the embodiment) for detecting the amount of movement of the needle 10 via the operating piece 12.

A sheath type thermocouple 14 as thin as possible is provided passing through the needle lO, the rond of the opening/closing cylinder 11, the piston, and the operating piece 12, and is made to protrude from the tip of the needle 10 as long as possible, more than four times the sheath diameter.

There is a resin flow path 8 on the resin flow path 8 side at the tip of the injection cylinder l.
A plasticizing cylinder 6 is provided which is connected in communication with the plasticizing cylinder 6 .

Note that 15 and 16 are heaters.

(Function) ■ When the needle 10 is retracted from the A position where the outlet of the resin flow path 8 is closed to the B position where the needle sliding hole 9 is closed by the rod retraction operation of the opening/closing cylinder 11, the plasticizing cylinder 6 moves into the resin flow path. 8, it communicates with the resin storage chamber 4 at the tip of the injection cylinder l. Next, when the plasticizing screw 7 is rotated, the molten resin is filled into the injection cylinder l and the injection nozzle 3 through the resin flow path 8.

In parallel with this, the injection plunger 2 is retreated to a preset position by the rod retraction operation of the injection drive cylinder 5, thereby completing the plasticizing process.

Since the detection part of the thermocouple 14 is located in the molten resin at a distance of four or more times the sheath diameter from the tip of the needle 10 at position B, the resin temperature can be accurately measured.

(2) When the needle 10 is advanced from the B position to the A position by the Ron protruding operation of the opening/closing cylinder 11, the exit of the resin flow path is blocked by the needle 10, and a thermoelectric current is generated in the resin flow path 8. Pairs of 14 detection units are housed. Next, when the injection plunger 2 is advanced by the rod protrusion operation of the injection drive cylinder 5, the injection cylinder 1
The molten resin in the injection nozzle 3 is injected and filled into a mold (not shown) without flowing back to the resin flow path 8 (without damaging the detection part of the thermocouple 14), and the injection process is completed. .

In order to prevent the detection part of the thermocouple 14 from being damaged by the high-pressure, high-speed flow during injection, it is preferable that the needle movement amount detection part 13 be interlocked to prevent injection when the needle 10 is between the A and B positions.

(2) Resin change When changing colors, the stagnant portion of the resin flow path 8 is cleaned by moving the needle 10 back and forth several times in an arbitrary range between positions A and C using the opening/closing cylinder 11.

(Effect of the invention) Since the present invention has the above configuration, it has the following effects.

(1) Since the needle valve mechanism can reliably prevent resin backflow even before injection, the actual resin inflow speed can be stabilized and molding quality can be improved.

(2) High-cycle precision molding is possible because the plasticizing device and injection device are independent, and a thick plasticizing screw or plunger can shorten the plasticizing time, while a thin injection plunger can improve metering accuracy. .

(3) Strength can be improved because it is possible to use a □ plasticizing screw with an integral structure without a threaded portion of the screw head or an injection plunger with an integral structure with a plunger.

(4) By using the needle valve mechanism and attaching an inexpensive thermocouple, it has become possible to measure resin temperature more accurately.

[Brief explanation of drawings]

The drawing is a sectional view showing an injection molding machine according to an embodiment of the present invention. l...Injection cylinder, 2...Injection plunger, (F
I) 3... Injection nozzle, 4... Resin storage chamber, 5... Injection drive cylinder, 6... Plasticizing cylinder, 7... Plasticizing screw, 8... Resin flow path, 9 ... Needle sliding hole, 10... Needle, 11... Opening/closing cylinder □ cylinder, 12... Operating piece, IS... Detection section, 14... Thermocouple.

Claims (1)

[Scope of Claims] 1) A resin flow path and a needle sliding hole are provided on the side wall of the resin storage chamber at the tip of the injection cylinder into which the injection plunger is inserted, and which are concentrically and with the same diameter and open opposite each other, so that the injection cylinder A needle that closes the resin flow path and the needle slide hole is provided on the needle sliding hole side of the tip portion so as to be movable back and forth, and a plasticizing cylinder is connected to the resin flow path of the injection cylinder tip portion. injection molding machine. 2) The injection molding machine according to claim 1, characterized in that a thermocouple is attached to the tip of the needle.