JPH07270Y2 - Split type extruder screw - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a split type extruder screw for reducing stress concentration at a connecting portion.

(Prior Art) A screw of a twin-screw extruder is locally worn because the fiber and powder are kneaded in a resin. Further, in order to extrude different resins, optimum screw combinations are required. Therefore, the screw type is used. In order to further improve the performance, the screw is long, and the height of the screw tends to increase. Therefore, the torque that drives the screw becomes large, and a large concentrated stress is generated at the bottom of the spline groove of the screw, which faces a limit in strength.

The holes of the split type screw 2 and the screw shaft 1 consist of a spline (Fig. 9), a key 4 (Fig. 10), and a hexagonal cross-sectional shape (Fig.
It is fixed in the direction of rotation with (Fig. 11). And screw 2
The mating surfaces of the screw shaft 1 and the screw shaft 1 are axially straightened as shown in FIG.

Now, the resin is kneaded by the split type screw and moves toward the nozzle. At this time, a large torque is required for the screw shaft due to the viscous resistance of the resin, and a large torsional torque gradually acts from the tip of the nozzle side shaft to the drive side.

(Problems to be solved by the invention) This torsion torque has a split type screw,
Torsional torque will act on the key or spline shaft, and the shaft will be largely twisted. This causes a large concentrated stress to act on the keys or spline grooves on both ends of the screw,
There was a problem that the maximum driving torque was limited due to the strength of the groove bottom stress concentration of the screw.

The present invention aims to improve the reliability against damage by reducing the stress concentration on the individual end faces of the split screw, and the strength weak points of the entire screw shaft are improved. An object of the present invention is to provide a high-performance split extruder screw capable of increasing load torque.

(Means for Solving the Problems) Therefore, the present invention provides a screw for an extruder having a split type screw, and the screw and the screw shaft are engaged through a key or a spline groove. Is provided with a relief portion such as taper processing in the axial direction on the side surface portion of the end portion thereof, which serves as means for solving the problem.

(Function) By providing a relief part such as taper processing in the axial direction on the side surface of the end of the groove, a large concentrated stress does not act on the groove and the stress concentration on the end surface of each split screw is reduced. The reliability against breakage is improved, the allowable load torque is increased, and it becomes a powerful means for high performance.

(Embodiment) The present invention will be described below with reference to the embodiments of the drawings. FIGS. 1 to 6 show an embodiment of the present invention, and FIG. 1 is connected to a screw shaft 1, 1 of a twin-screw extruder. It is a side sectional view showing an engagement state of split type screw 2 and cylinder 3.

FIG. 2 shows the acting direction of the torsional torque acting on the shaft 1 in the split screw of the twin-screw extruder shown in FIG. Note that FIG. 2 shows a state in which one screw is arranged for convenience of explanation. 3 shows a left end view of FIG. 2, FIG. 4 shows a right end view, and FIG. 6 is a sectional view taken along line AA of FIG. 3, in which the spline groove 2a of the screw 2 is taper cut (tapering, etc.). The taper cut 2b has a taper angle α of 1 to 10 as shown in FIG.
And the length I is 3 to 20 mm. FIG. 12 is a case of the conventional screw corresponding to FIG. 6 and shows the engagement state between the spline crest 1a and the spline groove 2a of the screw 2.

Fig. 7 shows the surface pressure distribution of the contact surface generated by the screw shaft 1 twisted by the spline groove 2a and the spline crest 1a obtained by structural analysis, and the results are compared between the present invention (solid line) and the conventional (dotted line). And show it. As is clear from the figure, in the case where the contact surface of the spline crest 1a and the spline groove 2a are processed in parallel as in the conventional case (Fig. 12), a large surface pressure is applied to the end of the screw 2. I understand.

On the other hand, in the case where the taper cut 2b according to the present invention (Fig. 6) is provided, since the end faces of the spline crest 1a and the spline groove 2a do not come into contact with each other due to taper, there is no surface pressure on the end face and the peak of the surface pressure distribution in the axial direction The value occurs at the boundary portion X between the straight portion and the tapered portion, but the maximum surface pressure in this case is about half that of the conventional one. Further, the stress value generated at the bottom of the spline groove also tends to be similar to the surface pressure distribution, and the maximum stress value generated at the same torque is greatly reduced. FIG. 8 shows another embodiment of the present invention, in which the taper cut portion 2b of FIG. 5 is replaced by the step cut portion 2c.
However, there is no difference in action and effect.

(Effect of the Invention) As described in detail above, according to the present invention, since the relief portion such as the taper processing is provided in the axial direction on the side surface of the end portion of the key or the spline groove, the stress concentration at the screw end portion can be reduced. It is possible to improve the strength weakness of the screw. Therefore, the reliability of the product can be improved. Further, in order to achieve high performance, the required torque is inevitably increased, but according to the present invention, the allowable torque is increased, which is an effective means for achieving high performance. Further, according to the present invention, the stress reduction rate is 30 to 50%, and the breaking torque is
I could improve by 15-40%.

[Brief description of drawings]

FIG. 1 is a side sectional view of a twin-screw extruder having a split type screw, FIG. 2 is a side view of one split type screw showing an embodiment of the present invention, and FIG. 3 is a left end view of FIG. Figure 4 is second
FIG. 5 is a front view showing the taper cut portion on the side surface of the screw groove showing the embodiment of the present invention, and FIG.
FIG. 8 is a sectional view taken along line AA in FIG. 7, and FIG. 7 is a diagram showing the surface pressure distribution between the spline groove and the spline mountain in the present invention and the prior art.
The figure is a front view showing a stepped cut portion of another embodiment of the present invention,
FIG. 9, FIG. 10 and FIG. 11 are sectional views showing engagement states of a conventional screw and a screw shaft, respectively, and FIG. 12 is engagement of a conventional spline groove and a spline mountain corresponding to FIG. It is a side sectional view showing a state. Description of main parts of the figure 1 …… Screw shaft 1a …… Spline peak 2 …… Split type screw 2a …… Spline groove 2b …… Taper cut (relief) 2c …… Step cut 3 …… Cylinder

Claims (1)

[Scope of utility model registration request] 1. An extruder screw having a split type screw, and the screw and the screw shaft are engaged with each other through a key or a spline groove, wherein an axial taper is formed on a side surface of an end portion of the key or the spline groove. Split type extruder screw, which is provided with a relief part for processing.