JPH0222267Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to a gland sealing device for an extruder.

(B) Prior Art As a device for sealing the gland portion of an extruder, a device in which a gland packing is provided between the inner diameter portion of the cylinder and the gland portion of the screw is generally used. This prevents resin from leaking inside the cylinder.

(c) Problems that the invention aims to solve However, although the conventional gland sealing device of an extruder using a gland packing can prevent resin leakage, air can enter from the outside and oxygen in the air can Therefore, there is a problem in that the resin deteriorates in the flight part of the screw, and the deteriorated resin mixes into the product pellets, degrading the quality.
Air enters into the cylinder because the inside of the cylinder becomes discontinuously and instantaneously in a negative pressure state during operation. That is, in the hopper portion, a state filled with resin and a state in which resin is being sucked are discontinuously repeated, and positive pressure and negative pressure are repeatedly applied within the cylinder. When the pressure becomes positive, the resin inside the cylinder tends to leak, but this is prevented by the gland packing. However, when the inside of the cylinder becomes a negative pressure state, the gland packing cannot prevent air from being sucked in, and air enters the cylinder. Therefore, the resin deteriorates as described above. In order to prevent such air from entering, there is a gland sealing device for an extruder that provides an inert gas layer on the outside of the gland packing.
96615, Japanese Unexamined Patent Publication No. 60-241579), such an apparatus is complicated and expensive because of the provision of an inert gas layer. The present invention aims to solve these problems.

(d) Means for solving the problem This invention solves the above problem by actively leaking a small amount of resin to constantly generate resin pressure in the gap in the gland, thereby preventing air from entering. This is an attempt to resolve the issue. That is, the extruder gland sealing device according to the present invention includes a circumferential groove provided on the outer periphery of the gland portion of the screw, and a circumferential groove provided on one axial side of the circumferential groove so as to communicate with the circumferential groove. and an inclined groove provided on the other axial side of the circumferential groove so as to communicate with the circumferential groove, and the inclined directions of both inclined grooves are opposite to each other and the screw The material is set in the direction in which the material is sent toward the circumferential groove when rotated.

(e) Action When the screw rotates, the inclined groove on the hopper side feeds the resin into the circumferential groove. Therefore, the circumferential groove is filled with resin. The resin in the circumferential groove tends to leak to the outside, but is pushed back toward the circumferential groove by the inclined groove provided at the opposite side of the circumferential groove from the hopper. Therefore, the amount of resin leaking to the outside is extremely small. Since the inclined groove acts to constantly supply resin to the circumferential groove, the resin in the circumferential groove generates a predetermined pressure. Since this pressure is actively generated by the rotation of the inclined groove, it is possible to prevent air from entering from the outside even if the inside of the cylinder temporarily becomes a negative pressure state. Note that the amount of resin leaking to the outside of the gland portion can be adjusted by adjusting the flow path area using a gap adjustment piece provided in the inclined groove.

(f) Example Figures 1 and 2 show a gland sealing device for an extruder according to the present invention. A screw 14 is provided on the inner diameter of a cylinder 12 provided with a hopper portion 10. A circumferential groove 18 having a predetermined depth and width is provided in the ground portion 16 of the screw 14. Four inclined grooves 20 are provided at 90 degree intervals closer to the hopper portion 10 than the circumferential groove 18. The inclined direction of the inclined groove 20 is arranged so as to have a reverse thread direction with respect to the rotational direction of the screw 14. The rear end side (left end side in FIG. 1) of the inclined groove 20 communicates with the circumferential groove 18, and the front end side (right end side in FIG. 1) of the inclined groove 20 communicates with the opening of the hopper portion 10. It is located on the front side of the end portion 10a and exposed to the hopper portion 10. A clearance adjustment piece 22 is provided on the front end side of this inclined groove 20.
are attached by bolts 24, as shown enlarged in FIG. The depth of the inclined groove 20 on the front end side is reduced by the thickness of the clearance adjustment piece 22. On the rear side of the circumferential groove 18, that is, on the opposite side to the side where the inclined groove 20 is provided,
Four inclined grooves 26 are provided at 90 degree intervals.
The inclined direction of the inclined groove 26 is opposite to that of the inclined groove 20, that is, the inclined groove 26 is provided in a normal thread direction with respect to the rotational direction of the screw 14. The front end side of the inclined groove 26 communicates with the circumferential groove 18 . The depth of the inclined groove 26 becomes shallower as it moves away from the circumferential groove 18.

Next, the operation of this embodiment will be explained. While the extruder is in operation, the screw 14 rotates and feeds the resin material in the hopper section 10 forward. Screw 1
4 causes a pumping action of the inclined groove 20, and a portion of the resin is sent rearward. That is, resin is continuously supplied to the circumferential groove 18. Therefore, the resin pressure in the circumferential groove 18 increases, and the resin in the circumferential groove 18 tries to move further rearward, but this time, due to the pumping action of the inclined groove 26, the resin in the circumferential groove 18 Pushed back to the 18 side. For this reason,
The resin in the circumferential groove 18 is always maintained at a predetermined pressure state. Note that by setting the pumping action of the inclined groove 20 to be slightly larger than the pumping action of the inclined groove 26, a portion of the resin leaks to the outside through the gap between the gland part 16 and the inner diameter part of the cylinder 12. do. The strength of the pumping action of the inclined groove 20 can be adjusted by changing the thickness and shape of the gap adjustment piece 22. As described above, a predetermined resin pressure is always applied in the circumferential groove 18, so even if the hopper part 10 side of the inner diameter part of the cylinder 12 is temporarily in a negative pressure state,
Air is prevented from entering through the outer periphery of the gland portion 16. Therefore, the resin is prevented from deteriorating due to oxygen in the air. This allows high quality extruded products to be obtained. According to the results of actual tests, by setting the amount of leakage from the gland to 0.01 to 0.05% of the extrusion amount (for example, the amount of leakage is 1 to 5 kg/h for an extrusion amount of 10 t/h). , we were able to obtain high-quality extruded products. Note that the shape of the gap adjustment piece 22 is changed depending on the resin material, extrusion conditions, etc., and adjusted so that a predetermined amount of resin enters the inclined groove 20.
The resin pressure (that is, the amount of resin leakage) of No. 8 can be adjusted. Note that if it is assumed that the device is always used under constant conditions, the gap adjustment piece 22 may not be provided. Further, since the amount of resin leakage changes depending on the viscosity of the resin, the amount of resin leakage can be appropriately adjusted by adjusting the temperature of the jacket in the gland section and the temperature of the screw.

(G) Effect of the invention As explained above, according to the invention, resin pressure is constantly generated in the circumferential groove by providing the circumferential groove and the inclined grooves on both sides of the circumferential groove in the gland part of the screw. Therefore, it is possible to prevent air from entering from the outside and prevent deterioration of the resin. Moreover, the gland sealing device of this extruder has a simple structure that can be constructed by machining the screw gland, and is very inexpensive.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a gland sealing device for an extruder according to the present invention, and FIG. 2 is a sectional view taken along the line -- in FIG. 10...Hopper part, 12...Cylinder, 14
... Screw, 16... Grand Department, 18...
Circumferential groove, 20... Inclined groove, 22... Gap adjustment piece, 26... Inclined groove.

Claims (1)

[Claims for Utility Model Registration] 1. A circumferential groove provided on the outer periphery of the gland portion of the screw; and an inclined groove provided on one axial side of the circumferential groove so as to communicate with the circumferential groove;
an inclined groove provided on the other axial side of the circumferential groove so as to communicate with the circumferential groove, and the inclined directions of both inclined grooves are opposite to each other, and when the screw rotates, the material A sealing device for the gland section of an extruder that is set in the direction of feeding the material into the circumferential groove. 2. The gland sealing device for an extruder according to claim 1, wherein the inclined groove on the hopper side is provided with a gap adjustment piece that can adjust the flow path area.