JPH0639964Y2 - Fluid transport device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a tandem type extrusion molding machine, a pre-plastic type tandem injection molding machine, and other devices for transporting a liquid phase fluid by a screw, and particularly a liquid phase from a screw base. TECHNICAL FIELD The present invention relates to a fluid transportation device provided with an improved screw seal for preventing fluid leakage.

(Prior Art) FIG. 3 shows a conventional tandem extruder, in which the liquid phase resin supplied from the raw material hopper 11 and plasticized by the first-stage screw 12 is transferred to the second-stage cylinder 14 through the connecting pipe 13. It is supplied to the liquid-phase resin supply port 15, further kneaded and homogenized by the second-stage screw 16, and transported, and is molded into a predetermined shape and extruded by the die 17 attached to the tip of the cylinder.

By the way, in this type of extruder, the following measures are taken in order to prevent resin leakage from the screw base.

In FIG. 4, 14 is a second-stage cylinder, 15 is a liquid-phase fluid supply port to which the liquid-phase resin is supplied from the first-stage cylinder via the connecting pipe 13, and the supply port 15 is of the second-stage cylinder 14. It is provided at a portion facing the rear end of the main screw 16 '. Second
The base of the stepped screw 16 has a groove (θa, Ha, Wa) smaller than any of the lead angle (θb), groove depth (Hb) and groove width (Wb) of the groove of the main screw 16 ′. Is provided with a booster screw 6.

In the above configuration, the liquid phase resin supplied from the liquid phase fluid supply port 15 and flowing to the rear end portion of the screw 16 is the second stage screw 16
It is pushed back toward the main screw 16 'while being boosted by the pressure boosting screw 6 part. At this time, at the tip of the pressure-increasing screw 6, the liquid phase resin that has been plasticized and sufficiently pressurized prevents the high-pressure liquid phase resin 15a flowing from the liquid phase fluid supply port 15 from flowing into the screw base end. Second stage screw
There is no leakage of molten resin at the base of 16.

FIG. 5 shows another conventional example, and the structure of the second stage screw 16 is the same as the screw structure of the conventional example shown in FIG. 4, and in this conventional example, the first stage cylinder and the second stage cylinder 14 are used. A branch pipe 13a is provided in a connection pipe 13 that connects the pipe and a supply port 2a provided in the screw base portion of the second stage cylinder 14 via a throttle valve 130, and is connected by a pipe 13b.

In this conventional device, the high-pressure molten resin supplied from the first-stage cylinder is throttled by the throttle valve 130 and a part of it is sent to the supply port 2a. Is once lowered, repressurized by the pressure screw 6 and extruded to the main screw 16 'side. Therefore, the screw base of the second-stage cylinder 14 is always kept at a low pressure, the high-pressure molten resin supplied from the first-stage cylinder does not reach the screw base, and leakage at the same is prevented.

Further, FIG. 6 (Japanese Patent Application No. 61-288713 (Japanese Patent Application Laid-Open No. 63-141717)
No.)), the solid resin 3a is supplied from the screw base separately from the liquid phase resin, and the solid resin 3a is plasticized by the pressure rising screw 6 part and sent out in the direction of the main screw 16 ', and the resin sent out is the main stream liquid. A method of preventing leakage of the phase resin has also been proposed.

(Problems to be solved by the invention) Thus, conventionally, a screw type seal has been used as a rotary shaft seal of a liquid phase fluid such as the above-mentioned molten resin. May increase twice or more as compared with the case where it does not shake, and besides the amount of liquid leakage, there is a risk of metal contact between the shaft seal part and the cylinder.

More specifically, in the conventional flight, the screw behavior in the cylinder changes depending on the type of raw material resin and the operating condition of the molding machine, and the lubrication action on the flight top and the cylinder wall surface becomes extremely poor. That is, a whirling phenomenon may occur in which the screw turns with eccentricity at a cycle of about 1/2 of the screw rotation cycle.At this time, in the conventional flight, there is lubrication between the flight top and the cylinder wall. Almost no pressure is generated. Therefore, wear often occurs due to direct contact between the flight top and the cylinder wall surface. Therefore, stable extrusion operation cannot be performed due to damage to the screw or cylinder, deterioration of extrudate, and the like.

The present invention has been made for the purpose of solving such a conventional problem, and is intended to improve the flight structure to suppress whirling of a rotary shaft and to secure a sealing function.

(Means for Solving the Problem) Therefore, in the present invention, in a device for transporting liquid phase fluid supplied to the cylinder base side to the tip of the cylinder by a screw, the screw portion upstream of the liquid phase fluid supply port is It has a leak-prevention groove, and has a step land in the width direction that is formed on the flight top side of the screw at the tip end side with a constant width and the same outer diameter as that of the base and is lower than the base side. Is a means for solving the problem.

(Operation) As described above, in the normal flight shape, when the rotating shaft whirls, a non-parallel load is generated, and almost no lubricating pressure is generated between the flight top and the cylinder wall, and galling occurs between the screw and cylinder. Occur.

In order to cope with such a trouble, in the present invention, since the flight structure has the above-mentioned structure, a lubricating pressure is generated in the step portion accompanying the rotation of the screw, and the screw is constantly positioned on the center side without being offset. It is said that when the screw is biased to one side of the cylinder, the amount of leakage is about three times as large as when the screw is located in the center of the cylinder. As a result, the amount of leakage is reduced, and the mechanical contact between the screw and the cylinder is reduced, so that mechanical damage can be prevented.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

1 and 2 show an embodiment of the present invention.

FIG. 1 is a sectional view of an essential part of a tandem extruder having a screw seal portion according to the present invention, and FIG. 2 is a detailed view of the seal portion.

In the figure, 1 is a second-stage cylinder, 4 is a liquid-phase fluid supply port to which a liquid-phase resin is supplied from the first-stage cylinder via a connecting pipe 13, and the supply port 4 is the main screw of the second-stage cylinder 1. 5'is provided at a portion facing the rear end portion. The lead angle of the groove of the main screw 5 '(θ
b), groove depth (Hb) and groove width (Wb) are provided with a booster screw 10 having a smaller value (θa, Ha, Wa).
Moreover, as shown in FIG. 2, the step land 2 in which the step S having the width W ₂ (W ₂ > W ₁ ) is formed on the flight top of the booster screw 10.
Is provided.

The step S is set to 0.5 mm or less, preferably 0.1 mm or less. It is more preferable that the width W ₂ of the step S has a relationship of W ₂ ≧ 1/2 W with respect to the width W of the flight top.

When the step land is formed on the flight top of the booster screw as described above, a relatively large lubricating pressure is generated near the closest contact point between the flight top and the cylinder wall surface as the screw rotates, and contact between the flight top and the cylinder wall surface occurs. To prevent.

As a result, the action of reducing the eccentricity between the screw and the cylinder works, and the whirling of the screw shaft is reduced, so that liquid leakage and metal contact can be prevented.

(Effects of the Invention) As described above in detail, according to the present invention, the step due to the step in the width direction is formed on the screw flight top portion at the tip end side of the screw and has an outer diameter equal to a certain width and lower than that of the base portion. By forming the land, the lubricating pressure is generated in the resin that has entered the step land portion, and the screw
The function of reducing the eccentricity between the cylinders works, and liquid leakage and metal contact can be eliminated.

[Brief description of drawings]

FIG. 1 is a side sectional view of a seal structure part of a tandem extruder showing a typical embodiment of the present invention, FIG. 2 is an enlarged view of a main part of the structure, and FIG. 3 is a conventional tandem extruder. Side sectional view of
FIG. 4 is a side sectional view of a conventional second stage screw and a screw base portion, FIG. 5 is a side sectional view showing another conventional example, and FIG. 6 is a side sectional view showing yet another conventional example. Description of main parts of the figure 1 ... Second stage cylinder, 2 ... Step land 5 ... Second stage screw, 5 '... Main screw 10 ... Booster screw, S ... Step

Claims (1)

[Scope of utility model registration request] 1. In a device for transporting a liquid phase fluid supplied to a cylinder base side to a cylinder tip by a screw, a screw portion upstream of a liquid phase fluid supply port has a liquid leakage preventing groove, and a flight thereof. A fluid transportation device characterized in that a step land is formed in the width direction formed on the tip side of the top portion in the front end direction of the screw with the same outer diameter as that of a constant width and lower than that of the base side in the width direction.