JPH01286816A - Rotary die for extrusion molding - Google Patents

Abstract

PURPOSE:To make a plurality of lines of protrusions to be formed among a plurality of lines of spiral grooves into a radial state precisely, by a method wherein a plurality of lines of molding grooves are tilted at a fixed angle in a turning direction of a die to a shaft center direction extending to resin outlet side from a resin inlet side. CONSTITUTION:A molding groove 2 of a rotary die 1 for extrusion molding is tilted in a turning direction of the rotary die 1 for extrusion molding to a shaft center extending to a resin outlet 1b side from an inlet 1a side. When the tilting angle is alpha, since the rotary die 1 for extrusion molding is turning, a speed of resin of a top part of the molding groove 2 in the resin outlet 1b becomes Vb obtained by compounding v1 and V1. Since the alpha can be set up so that an ingredient of a circumferential direction of the Vb becomes equal to V'1, a protrusion can be formed precisely radially by eliminating a twist of the protrusion. A matter where the ingredient of a circumferential direction of the Vb becomes equal to the V'1 means that a difference V between the V'1 and V1 becomes equal to an ingredient of the circumferential direction of the V'1.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a long resin molded product having a plurality of spiral grooves on the outer peripheral surface and a reinforcing linear body arranged in the center. The present invention relates to a rotating die for extrusion molding used for extrusion molding products.

(Prior Art) When extruding a long resin molded product having a plurality of spiral grooves on the outer circumferential surface, such as a spacer for laying an optical fiber cable, conventionally, Figs.
A rotating die 51 for extrusion molding as shown in the figure was used. A plurality of forming grooves 52 along the axial direction are formed on the inner peripheral surface of the extrusion molding rotary die 51 over the entire length, and while the extrusion molding rotary die 51 is rotated around the axis, reinforcement By passing the linear body and the resin at the same time, a resin molded product 54 as shown in FIG. 11 is obtained. A plurality of spiral grooves 55 are formed on the outer peripheral surface of the resin molded product 54.
are formed, and a spiral protrusion 56 is formed between each of these spiral grooves 55. These protrusions 56 correspond to the forming grooves 52 of the extrusion molding rotary die 51,
The height of the protrusion 56 is from the bottom 52a of the molding groove 52 to the top 5.
2b, that is, the depth of the forming groove 52. However, since the resin molded product 54 shrinks after passing through the extrusion molding rotary die 51, the extrusion molding rotary die 5
1, and the height of the protrusion 56 is slightly smaller than the depth of the forming groove 52. Resin molded product 54
A reinforcing linear body 57 is embedded on the axis of the
This linear body 57 is constructed by twisting a plurality of steel wires 58 together.

For example, by accommodating a plurality of optical fiber cables in each spiral groove 55 of the resin molded product 54 and wrapping a tape or the like around the outer periphery of the resin molded product 54, the optical fiber cables can be supported and protected.

(Problems to be Solved by the Invention) When the above-mentioned conventional extrusion molding rotary die 51 is used, the protrusions 56 of the resin molded product 54 are not accurately radial, and the optical fiber cable is not inserted into the spiral groove 55, etc. may cause inconvenience. That is, both sides 56 of the protrusion 56
a and 56b are the widthwise center of the protrusion 56 and the resin molded product 5
The rotary die 5 for extrusion molding during molding is not symmetrical with respect to the straight line passing through the axis of the extrusion molding die 5 as shown in FIG. 11.
It was tilted in the rotation direction of 1. This tendency is particularly noticeable when high-speed molding is performed.

The reason for this will be briefly explained below. It is assumed that the flow of the resin at the resin outlet of the extrusion molding rotary die 51 follows Newtonian flow, and that there is no slippage between the resin and the extrusion molding rotary die 51 and the linear body 57. Even if you consider this, there is no problem as long as the rotational speed of the extrusion molding rotary die 51 and the advancing speed of the linear body 57 are low. Now, calculate the diameter of a circle that passes through the bottom 52a of the forming groove 52 and is centered on the axis of the rotating die 51 for extrusion molding.

, the diameter of a circle centered on the axis of the extrusion molding rotary die 51 and passing through the top 52b of the forming groove 52 is DI, the diameter of the linear body 57 is d, and the rotation speed of the extrusion molding rotary die 51 is N.
[r, p, ff1. The velocity of the linear body 57 is v [m
/mln], the velocity V in the circumferential direction of the resin at the bottom 52a portion of the molding groove 52 at the resin outlet of the extrusion molding rotary die 51. is V −πN D .

Here, if the linear body 57 does not exist, the velocity distribution of the resin in the circumferential direction is as shown by a solid line a, and the velocity v1' of the resin in the circumferential direction at the top 52b portion is V + '-πND
.

become. However, in reality, the linear body 57 passes through the center of the extrusion molding rotary die 51, so the resin is transferred to the linear body 57.
As a result of being restrained by the surface of 7, the velocity distribution becomes as shown by the solid line, and the velocity V+ of the resin in the circumferential direction at the top portion 52b is V −1lyrND (D d) / (Do
d) become. Therefore, the difference between the two is ΔV′″V + 'V I −x N d (D D ) / (Do d
), the resin is twisted and the protrusion 56 is tilted.

The velocity distribution of the resin in the axial direction at the resin outlet of the extrusion molding rotary die 51 is as shown by the solid line C in FIG. 13, and the velocity Vl of the resin in the axial direction at the top portion 52b is v - v (D-D) / (Do d)
It is. Therefore, the velocity Va of the resin at the top portion 52b at the resin outlet of the extrusion molding rotary die 51 is the 14th
As shown in the figure, the speed v1 in the circumferential direction and the speed Vl in the axial direction
It is a vectorial composition of

(Means for Solving the Problems) In order to solve the above problems, the rotating die for extrusion molding of the present invention has a plurality of spiral grooves on the outer peripheral surface and a reinforcing linear body is arranged in the center. In a rotary extrusion die that is used for extrusion molding a long resin molded product, a plurality of molding grooves are formed on the inner circumferential surface over the entire length in the axial direction, and the extrusion molding die is rotated around the axis during molding. A plurality of protrusions formed between the plurality of spiral grooves by inclining the plurality of molding grooves at a predetermined angle in the die rotation direction with respect to the axial direction from the resin population side to the resin outlet side. The structure is such that a resin molded product having exactly radial shapes can be obtained.

(Function) Since the plurality of molding grooves are inclined at a predetermined angle in the die rotation direction with respect to the axial direction from the resin inlet side to the resin outlet side, the top of the molding groove at the resin outlet of the extrusion molding rotary die is The speed of the resin in the circumferential direction is higher than that in the case where the molding grooves are along the axial direction. This increase in speed can be set arbitrarily by changing the inclination angle of the molding groove, so by appropriately selecting the inclination angle of the molding groove, it is possible to eliminate twisting of the protruding part of the resin molded product and make it radial accurately. .

(Example) Hereinafter, an example of the present invention will be described based on FIGS. 1 to 7.

FIG. 1 is a longitudinal sectional side view of a rotating die for extrusion molding according to an embodiment of the present invention, FIG. 2 is a front view of the same, and FIG. A plurality of molding grooves 2 are formed on the inner peripheral surface of the rotating die 1 over the entire length in the axial direction. These forming grooves 2 extend from the resin population 1a side of the extrusion molding rotary die 1 to the resin outlet 1b side at a predetermined angle in the rotational direction of the extrusion molding rotary die 1 shown by the arrow in FIG. 1 with respect to the axial direction. It is sloping.

In FIG. 3, 2a is the bottom of the forming groove 2, 2b is the top of the forming groove 2, and the diameter of the bottom 2a is the same. Binding,
Let DI be the diameter of the top portion 2b.

FIG. 4 is a cross-sectional view of an extrusion molding machine equipped with the above-mentioned rotary die 1 for extrusion molding. 4 is a casing, and inside this casing 4, a cylindrical nipple holder 6 is mounted around the axis by a bearing 5. It is rotatably supported. A substantially conical nipple 7 is screwed into the tip of the nipple holder 6, and a linear body insertion hole 8 is formed in the nipple holder 6 and the nipple 7 over the entire length on the axis.

A cylindrical flow guide 9 is fitted to the outer periphery of the tip of the nipple holder 6. The rear end of this flow guide 9 is screwed into the nipple holder 6, and the inner periphery of the tip is fitted to the tip of the nipple holder 6. It faces the outer periphery with a slight gap. The flow guide 9 is rotatably supported around its axis by bearings 10 and 11, and a rotating die 1 for extrusion molding is attached to the tip via a substantially cylindrical spacer 12. That is, a substantially cylindrical die holder 13 that loosely fits around the outer periphery of the spacer 12 and the extrusion molding rotary die 1 is screwed onto the tip of the flow guide 9, and the spacer 12 and the extrusion molding rotary die 1 are connected to the flow guide. It is supported by being inserted between the tip of the die holder 9 and the tip of the die holder 13.

A plurality of resin flow holes 14 are formed at appropriate intervals in the circumferential direction at the tip of the flow guide 9, and the resin supplied to the resin supply holes 15 formed in the casing 4 is
It passes through the resin flow hole 14 and reaches the gap between the outer circumference of the tip of the nipple holder 6 and the inner circumference of the tip of the flow guide 9;
Furthermore, it passes between the outer periphery of the nipple 7 and the inner periphery of the spacer 12 and reaches the rotating extrusion die 1 . An annular heater 17 is attached to the casing 4 via a heater support 16, and this heater 17 is attached to the die holder 13.
It fits loosely around the outer periphery. The heater 17 heats the resin passing through the extrusion molding rotary die 1 and maintains it at a predetermined temperature. The nipple holder 6 is rotated about its axis by a drive device such as an AC servo motor (not shown) via a power transmission mechanism such as a chain or sprocket.

FIG. 5 is a cross-sectional view of a resin molded product molded by an extrusion molding machine equipped with the above extrusion molding rotary die 1, and is a long resin molded product in which one linear body as a reinforcing member is embedded in the center. 20 has a plurality of spiral grooves 21 formed on its outer peripheral surface. In this resin molded product 20, a plurality of spiral protrusions 22 formed between a plurality of spiral grooves 21 are accurately radial. That is, no matter where the resin molded product 20 is cut diametrically at any position in the axial direction, both side surfaces 22a and 22b of the protrusion 22 are aligned with the protrusion 2 at the cut end surface.
2 and the axis of the resin molded product 20. The linear body 19 is made by twisting a plurality of steel wires 23 together, and has a diameter d. As the linear body 19, one steel wire 23 may be used, or FRP or the like may be used.

When producing the resin molded product 20, first, one linear body is passed through the linear body insertion hole 8 shown in FIG. 4, and the linear body 19 is positioned on the axis of the extrusion molding rotary die 1. Next, the nipple holder 6 is moved around the axis by a drive device by N [r,p
, Il, ] in a predetermined direction. As a result, the nipple 7, the flow guide tube, the spacer 12, the extrusion molding rotary die 1, and the die presser 13 rotate together with the nipple holder 6. Further, in synchronization with the rotation of the nipple holder 6, the linear body 19 is moved toward the distal end side of the linear body insertion hole 8 at a speed v [m/ml1nl]. In this state, a resin such as quick-drying high-density polyethylene is supplied to the resin supply hole 15 at a predetermined pressure. As a result, the resin passes from the resin supply hole 15 through the resin distribution hole 14 and reaches the annular space between the outer periphery of the tip of the nipple holder 6 and the inner periphery of the tip of the flow guide 9, and further reaches the outer periphery of the nipple 7 and the spacer 12. The resin enters the extrusion molding rotary die 1 from the resin population 1a side through the space between the inner periphery and is extruded to the resin outlet 1b side. At this time, since the linear body 19 is located on the axis of the rotating extrusion die 1, the resin molded product 2 with the linear body 19 embedded in the center
0s are formed continuously. In addition, the extrusion molding rotary die 1 has a plurality of molding grooves 2 formed on its inner circumferential surface and rotates together with the nipple holder 6, so that the resin molded product 2 can be
A plurality of spiral grooves 21 are formed on the outer peripheral surface of 0.

As shown in FIG. 5, the resin molded product 20 thus formed has a plurality of spiral protrusions 22 that are accurately radial. That is, no matter where the resin molded product 20 is cut diametrically at any position in the axial direction, at the cut end surface,
Both side surfaces 22a and 22b of the protrusion 22 are symmetrical to each other with respect to a straight line passing through the center of the protrusion 22 in the width direction and the axis of the resin molded product 20. This will be explained below.

As shown in FIG. 6, the molding groove 2 of the rotary die 1 for extrusion molding is inclined in the opposite direction to the spiral groove 21 of the resin molded product 20. That is, from the resin population 1a side to the resin outlet 1b side, it is inclined in the rotation direction of the extrusion molding rotary die 1 with respect to the axis. Therefore, if the inclination angle is α, the velocity of the resin at the top 2b of the molding groove 2 at the resin outlet 1b is v as shown in FIG. 7, assuming that the extrusion molding rotary die 1 is not rotating. , /become. And since the extrusion molding rotary die 1 is actually rotating,
The velocity of the resin at the top 2b of the molding groove 2 at the resin outlet 1b is vb, which is the vectorial combination of v' and vl. By setting α so that the circumferential component of vb is equal to VI', twisting of the protrusion 22 can be eliminated and the protrusion 22 can be accurately formed radially. The fact that the circumferential component of vb is equal to V+' means that, as is clear from Figure 7, the difference ΔV between V' and vI is equal to the circumferential component of ■1'. be. Here, the circumferential component of v1' is Vlianα, and ■1 is v −v (
D −D ) / (Do −d), and Δ■ is ΔV−πNd (D −D
)/(Do-d)vI, so a-jan-1(πNd/v).

When we actually manufactured and experimented with the rotating die 1 for extrusion molding, we found that by making a slight modification to α, the resin molded product 2
It was possible to make the protruding portions 22 of 0 accurately radial. As a result of experiments, it was confirmed that α should be made slightly larger than the above calculation formula. This is considered to be because the flow of the resin does not actually follow a Newtonian flow, and also because slippage occurs between the extrusion molding rotary die 1 or one linear body and the resin. Furthermore, as a result of the experiment, the inclination angle α of the forming groove 2 was determined to be jan-1(πNd
/v) <a and α<3tan (πNDo/v). Naori o is -Do-411,28(πD/4-d)+d according to the general die hole diameter design formula
]/π. Here, D is the outer diameter of the resin molded product 20 as a finished product.

(Another Embodiment) FIG. 8 shows another embodiment. In this way, by using a rotary die 26 for extrusion molding with a hole shape and a substantially rectangular cross section, a spiral groove with the same groove depth can be formed. When molding a resin molded product 20 having a hole shape of 21, it is easier to ensure the wall thickness compared to the extrusion molding rotary die 1 whose hole shape is approximately circular in cross section.
Therefore, the rotating die 26 for extrusion molding can be made compact.

(Effects of the Invention) As explained above, according to the present invention, a long resin molded product having a plurality of spiral grooves on the outer peripheral surface and a reinforcing linear body arranged in the center is extruded. In a rotary die for extrusion molding, in which a plurality of molding grooves are formed on the inner circumferential surface over the entire length in the axial direction and are rotated around the axis during molding, the plurality of molding grooves are connected to the resin inlet. By inclining at a predetermined angle in the die rotation direction with respect to the axial direction from the side to the resin outlet side, a resin molded product in which the plurality of protrusions formed between the plurality of spiral grooves form an accurate radial shape can be obtained. In order to achieve this, multiple molding grooves are inclined at a predetermined angle in the die rotation direction with respect to the axial direction from the resin inlet side to the resin outlet side, so that molding at the resin outlet of the rotary die for extrusion molding is possible. The resin at the top of the groove is smaller than when the molded groove runs along the axial direction.
The speed in the circumferential direction is increased, and therefore, by appropriately selecting the inclination angle of the molding groove, the protrusion of the resin molded product can be made untwisted and accurately radial. In addition, this twisting of the protrusion becomes especially noticeable during high-speed molding, so high-speed molding could not be performed in the past, but according to the present invention, the twist of the protrusion can be ensured even when high-speed molding is performed. Since it can be removed quickly, high-speed molding is possible and productivity can be improved.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional side view of a rotary die for extrusion molding according to an embodiment of the present invention, FIG. 2 is a front view of the same, FIG. 3 is an explanatory diagram of a forming groove of the rotary die for extrusion molding, and FIG. FIG. 5 is a cross-sectional view of an extrusion molding machine equipped with a rotary die for extrusion molding, and FIG.
The figure is an explanatory diagram of the relationship between the slope of the molding groove of the rotary die for extrusion molding and the slope of the spiral groove of the resin molded product. Figure 7 shows the velocity of the resin at the top of the molding groove at the resin outlet of the rotary die for extrusion molding. FIG. 8 is an explanatory diagram of the hole shape of a rotary die for extrusion molding in another embodiment, FIG. 9 is a longitudinal cross-sectional side view of a conventional rotary die for extrusion molding, FIG. 10 is a front view of the same, and FIG. Figure 11 is a cross-sectional view of a resin molded product formed using the same extrusion molding rotary die, and Figures 12 to 14 are cross-sectional views of the resin molded product at the resin outlet of the extrusion molding rotary die during molding of the same resin molded product. It is an explanatory diagram of speed. 1.26... Rotating die for extrusion molding, 1a... Resin inlet, 1b... Resin outlet, 2... Molding groove, 19...
- Linear body, 20... Resin molded product, 21... Spiral groove,
22... Protrusion patent applicant Mitsubishi Cable Industries Co., Ltd. No. 1 Figure 2 Figure 3 Figure 5 Figure 6 No. 6? Figure 10 Figure 11 Figure 12

Claims (1)

[Claims] 1. Used to extrude a long resin molded product that has multiple spiral grooves on the outer circumferential surface and a reinforcing linear body arranged in the center, and has multiple spiral grooves on the inner circumferential surface. In a rotary die for extrusion molding in which a groove is formed over the entire length in the axial direction and is rotated around the axis during molding, the plurality of molding grooves are formed in the die in the axial direction from the resin inlet side to the resin outlet side. A rotary die for extrusion molding, characterized in that the die is tilted at a predetermined angle in the direction of rotation to obtain a resin molded product in which a plurality of protrusions formed between the plurality of spiral grooves form an accurate radial shape. .