JP2009090544A - Compression screw extruder and compression extruding method of unvulcanized rubber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stably qualified tire by supplying rubber by determinate quantities to a die (or a mouth piece) without providing a gear pump in an extruder of unvulcanized rubber. <P>SOLUTION: A compression screw extruder 1 is equipped with a cylinder 12, a screw 11 rotatably supported within the cylinder 12 and the die (or the mouth piece) 14 mounted to the tip (or the right end of the figure) of the cylinder 12. The transfer space volume of the unvulcanized rubber formed by the screw 11 and the inner peripheral wall of the cylinder 12 reduces toward the tip side of the screw 11 from its rear end side, resulting in developing back flow in the transferring unvulcanized rubber. Owing to the reaction force to this back flow, the pressure applied to the unvulcanized rubber to be transferred to the die 14 is risen up to the desired pressure which enables the unvulcanized rubber to be fed by determinate quantities to the die 14 and, at the same time, this back flow itself acts for sealing the pressure of the boosted feed rubber, resulting in surely maintaining the boosted pressure. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a compression screw extruder capable of increasing the extrusion pressure for unvulcanized rubber without using a gear pump and stably discharging the unvulcanized rubber, and a compression extrusion method for unvulcanized rubber.

  Generally, a tire is composed of a plurality of rubber members for tires. For example, each part such as an inner liner, a tread part, and a sidewall part is formed of unvulcanized rubber corresponding to required characteristics. . The rubber member constituting each part of these tires is obtained by extruding unvulcanized rubber from an extruder equipped with a die corresponding to the cross-sectional shape of each rubber member. It is formed by cutting to a length or winding it on a tire molding drum.

In such a rubber extruder, if the extrusion amount fluctuates due to insufficient pressure when extruding unvulcanized rubber (hereinafter simply referred to as rubber), the molded rubber gauge (thickness) fluctuates and becomes uniform. Since a rubber member having a shape cannot be formed, it is necessary to make the pressure for extruding rubber, that is, the extrusion amount of rubber constant.
As a solution to this problem, there is known an extrusion device in which a gear pump is provided in front of the die of the extrusion device to increase the pressure of the rubber to a necessary pressure and the rubber pump is used to extrude the rubber by a certain amount (for example, patents). Reference 1).

FIG. 7 is a cross-sectional view of a conventional rubber extrusion apparatus described in Patent Document 1.
The rubber extrusion apparatus 100 includes a hopper 113 for feeding rubber together with a material to be kneaded, a screw 111 for feeding the rubber fed to the hopper 113 while kneading, a cylinder 112, two gears 122a, and their bearings 122b. And a die head 124 for forming rubber to be extruded into a desired cross-sectional shape.

  In this rubber extrusion device, the rubber charged from the hopper 113 is transferred by the rotating screw 111 and discharged to the rubber retention part 115, and the rubber that has once retained in the rubber retention part 115 is fed from the die head 124 by the gear pump 122 by a fixed amount. Extruded into a predetermined shape.

By the way, in this rubber extrusion device, in addition to daily maintenance such as refueling the rotating part, high-pressure rubber discharged from the cylinder 112 enters the gap between the gear 122a and the bearing 122b of the gear pump 122 and causes a bearing failure. When a bearing breaks down, there is a problem that a large maintenance burden is required for the repair.
JP 2001-150515 A

  The present invention has been made in order to solve the above-described conventional problems, and an object of the present invention is to provide an unvulcanized rubber extruder without providing a gear pump as in the prior art and using rubber as in the conventional case. It is to supply tires of stable quality by supplying a fixed amount to a die.

The invention of claim 1 has an inlet for introducing unvulcanized rubber on one end side, and a discharge port for unvulcanized rubber on the other end side. A compression screw extruder comprising a screw that is kneaded and transferred, a cylinder that accommodates the screw, and a die that is directly connected to the cylinder and that extrudes unvulcanized rubber discharged from the discharge port. The volume of the unvulcanized rubber transfer space formed by the inner peripheral wall of the cylinder is reduced from the charging port side toward the discharge port side, and the unvulcanized rubber is quantitatively supplied from the discharge port to the die. The pressure is increased to a possible predetermined pressure.
According to a second aspect of the present invention, in the compression screw extruder according to the first aspect, the space volume for transfer is gradually reduced from the charging port side toward the discharge port side.
According to the invention of claim 3, unvulcanized rubber introduced from the inlet on one end side of the cylinder passes through the unvulcanized rubber transfer space formed by the screw and the cylinder inner peripheral wall to the other end side outlet. A method of compressing and extruding unvulcanized rubber, comprising a step of transporting and a step of supplying and extruding unvulcanized rubber discharged from a discharge port to a die, wherein the space volume for transfer is set on the inlet side And a pressurizing step of increasing the pressure to a predetermined pressure at which the unvulcanized rubber can be quantitatively supplied to the die.
According to a fourth aspect of the present invention, in the method for compressing and extruding unvulcanized rubber according to the third aspect, the unvulcanized rubber is reduced by reducing the space volume for transfer from the inlet side toward the outlet side. The step of pressurizing is characterized in that the space volume for transfer is reduced stepwise.
According to a fifth aspect of the present invention, in the method for compressing and extruding an unvulcanized rubber according to the third or fourth aspect, a backflow of the unvulcanized rubber is generated in the space for transferring the unvulcanized rubber to generate the vulcanized rubber. And a step of sealing the pressure of the pressed unvulcanized rubber.

  According to the present invention, since an unvulcanized rubber extruder does not use a gear pump as in the prior art, not only the maintenance work of the extruder can be greatly reduced, but also the equipment cost can be reduced. Further, a stable quality tire can be obtained as in the prior art without providing a gear pump.

Hereinafter, a compression screw extruder according to an embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic sectional view of a compression screw extruder according to this embodiment.
The compression screw extruder 1 includes a cylinder 12, a screw 11 rotatably supported inside the cylinder 12, a die 14 attached to the front end (right end in the figure) of the cylinder 12, and the rear part of the cylinder 11. A hopper 13 provided on the upper side (left side in the figure) and a rotation drive device 16 such as a motor for rotating the screw 11 are provided.

  The cylinder 12 accommodates the screw 11 and the rotary drive device 16 therein, and the inner surface thereof has a cylindrical shape having a diameter corresponding to the diameter of a blade portion 21 described later of the screw 11. On the upper side of the rear part of the cylinder 12, a supply port 12 a for taking in the feed rubber introduced into the hopper 13 into the cylinder 12 is formed.

  The cylinder 12 is provided with temperature adjusting means 15 for adjusting the temperature of the feed rubber transferred by the screw 11. The temperature adjusting means 15 is composed of a heater and a cooling device (not shown), and is disposed in the screw accommodating portion of the cylinder 12 so as to surround the screw 11. The temperature adjusting means 15 is provided inside the cylinder 12 by adjusting the temperature of the cylinder 12 itself. The rubber around the screw 11 is heated and cooled.

The hopper 13 is connected to the supply port 12a with its width gradually becoming narrower from the top in order to guide the fed rubber to the supply port 12a of the cylinder 12.
The die 14 is fixed to the tip of the cylinder 12 by a fixing means such as a screw (not shown) and is configured to be detachable from the cylinder 12.

  The screw 11 is composed of a screw shaft 20 and a spiral wing portion 21 provided on the outer periphery of the screw shaft 20, and a rear end portion thereof is connected to an output shaft of the rotary drive device 16 shown in FIG. . The rotation drive device 16 rotates the screw shaft 20 to transfer the feed rubber introduced from the hopper 13 in the direction of the die 14. During this transfer, the feed rubber is heated and kneaded by heating by friction with the wing portion 21.

The diameter of the screw shaft 20 is uniform, and the tip portion on the die 14 side has a conical shape. In the shaft of the screw shaft 20, temperature adjusting means different from the temperature adjusting means 15 for circulating hot water for adjusting the temperature of the rubber to be transferred is provided.
The diameter of the spiral blade portion 21 is substantially the same as the inner diameter of the cylinder 12 so that the unvulcanized rubber does not enter the gap between the outer peripheral surface of the blade portion 21 and the inner surface of the cylinder 12.

FIG. 2 is an enlarged view of the screw 11 shown in FIG.
The screw 11 is a five-stage screw in which the volume of the feed rubber transfer space per unit time by the screw 11 (here, the space volume per round of the screw 11) is different, that is, the rear end (left end in the figure). To the first stage screw 11a, the second stage screw 11b, the third stage screw 11c, the fourth stage screw 11d, and the fifth stage screw 11e.

  The angles (hereinafter referred to as screw angles) and pitches of the wings 21a to 21e of the wings 21a to 21e with respect to the direction orthogonal to the screw central axis are different from each other. The pitch is configured to gradually decrease toward the die 14.

FIG. 3 is a diagram (graph) showing a change in screw angle with respect to the screw length of the screw 11 according to the present embodiment.
In this figure, the vertical axis represents the screw angle θ (θ ₁ , θ ₂ , θ ₃ , θ ₄ , θ ₅ ), and the horizontal axis represents the screw length L (L ₁ , L ₂ , L ₃ , L ₄ , L ₅ ). , Showing the relationship between the two.
As shown in the figure, the screw angle θ at each stage is constant, but gradually decreases toward the die 14.

  Further, as the screw angle θ is decreased, the pitch of the blade portions 21a to 21e in each stage is reduced. The volume of the transfer space of the feed rubber surrounded by the portions 21a to 21e and the inner peripheral wall of the cylinder 12 shown in FIG. 1 is reduced.

FIG. 4 is a diagram (graph) showing a change in the volume of the feed rubber transfer space according to this embodiment.
This figure shows the relationship between the volume V of the transfer space on the vertical axis and the transfer path length l on the horizontal axis. Incidentally, the transfer path length of the screw 11a~11e of each stage in the figure, represented by _{l 1, l 2, l 3} , l 4, l 5 , respectively.
As shown in the figure, the volume V of the transfer space of the present embodiment is decreased step by step for each stage screw, thereby reducing the volume of the feed rubber transfer space step by step. The pressure is increased stepwise while feeding toward the die 14.

FIG. 5 is a diagram showing the volume movement amount (transfer amount) per one screw rotation of the rubber transferred by the screws 11a to 11e of each stage.
In the present embodiment, the amount of rubber transferred per screw rotation of each stage of the screws 11b to 11e excluding the screw 11a is designed to be about 70% of that of the preceding stage.

That is, in this embodiment, it is designed so that a back flow (back flow) of about 30% is generated in each stage of the screws 11a to 11e except the screw 11a. That is, when the amount of feed rubber fed into the hopper 13 is 100, the discharge amount of the fifth stage screw 11e is theoretically about 24 (100 × 0.7 × 0.7 × 0.7 × 0.7). It becomes.
The pressure applied to the feed rubber transferred to the die 14 by the reaction force due to the backflow is increased to a desired pressure at which the feed rubber can be supplied to the die 14 in a fixed amount, and the pressure of the feed rubber with the backflow itself increased. As a result, the increased pressure is reliably maintained.

A method of extruding the feed rubber in the compression screw extruder 1 having the above configuration will be described with reference to FIGS. 1 and 2.
First, the compression screw extruder 1 is turned on, and the screw 11 is rotated at a constant speed by the rotation driving device 16 shown in FIG.

Next, feed rubber is introduced from the hopper 13 and kneaded, heated, and heated while being fed with the first to fifth stage screws 11a to 11e shown in FIG. At the same time, by gradually reducing the volume of the transfer space from the first stage screw 11a to the fifth stage screw 11e, the pressure of the transferred rubber is gradually increased, and a predetermined discharge pressure in the fifth stage screw 11e. Boost up to
The rubber discharged from the fifth stage screw 11e is molded by the die 14, goes out of the machine, and is vulcanized in the subsequent vulcanization process.

  The temperature of the feed rubber transferred by the screw of each stage is appropriately adjusted by the temperature adjusting means 15 and about 90 ° C. and the pressure is about 40 MPa (megapascal) when discharged from the fifth stage screw 11e. It is desirable that the pressure has been increased to about 1.

  As described above, in the present embodiment, the back flow of the amount of feed rubber is reduced by the configuration in which the volume of the transfer space of the screws 11a to 11e of each stage decreases step by step as the latter stage screw is obtained. The reaction force of this backflow increases the pressure of the feed rubber and rotates the screw 11 at a constant speed, so that the pressure applied to the feed rubber can be maintained at a high pressure, and the feed rubber can be discharged in a fixed amount. it can.

  The compression screw extruder 1 according to the present embodiment does not require the gear pump described above, so that not only can the equipment cost be reduced, but naturally there is no need for maintenance of the gear pump, which was conventionally required. Further, since the above-mentioned rubber staying portion when using a gear pump is not necessary, when changing the type of unvulcanized rubber to be extruded by the compression screw extruder 1, the screw 11 is reversed so that the inside of the cylinder 12 As a result, almost all of the rubber can be taken out, and the rubber type can be easily and quickly switched.

Further, since no gear pump is used, the rubber transfer path of the head portion of the cylinder 12 can be made shorter than when a conventional gear pump is used, and there is an advantage that pressure loss is reduced in addition to downsizing.
Since the pressure applied to the rubber can be increased by increasing the number of stages and the number of rotations of the screw 11, the pressure can be easily adjusted. Further, although the compression screw extruder 1 is used over a long period of time, it is inevitable that the screw 11 and the cylinder 12 are worn and the pressure is lowered. However, the pressure drop is corrected by the multistage compression means, so the influence of the wear is Less than conventional rubber extrusion equipment.

  In order to increase the rubber extrusion pressure to a predetermined pressure and to keep the amount of extrusion constant, it is designed to reduce the volume of the rubber transfer space step by step as in this embodiment. Although it is easy to manufacture, it has a shape that continuously reduces the volume of the rubber transfer space from the rear end side to the front end side of the screw 11, that is, a shape that continuously reduces the screw angle of the blade portion 21 of the screw 11. There may be.

  Moreover, in the above embodiment, by changing the screw pitch stepwise, the space volume for the transfer rubber (space volume per circumference) composed of the screw and the cylinder is changed, but the pitch is not necessarily limited. For example, as shown in FIG. 6, the space volume can be changed by changing the depth of the spiral groove of the screw.

It is a schematic sectional drawing of the compression screw extruder which concerns on this embodiment. It is an enlarged view of a screw. It is a figure showing the change of the screw angle with respect to the screw length of a screw. It is a figure which shows the change of the volume of the transfer space of feed rubber. It is a figure which shows the volume moving amount (transfer amount) per rotation of the screw of the rubber which the screw of each stage transfers. It is a schematic sectional drawing of the compression screw extruder which concerns on other embodiment. It is sectional drawing of the rubber extrusion apparatus described in patent document 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Compression screw extruder 11, 111 ... Screw, 11a ... 1st stage screw, 11b ... 2nd stage screw, 11c ... 3rd stage screw, 11d ... 4th Stage screw, 11e ... 5th stage screw, 12 ... Cylinder, 13, 113 ... Hopper, 14, 124 ... Dies, 15 ... Temperature adjusting means, 16 ... Rotation drive device, 20, 20a, 20b, 20c, 20d, 20e ... screw shaft, 21, 21a, 21b, 21c, 21d, 21e, ... wing part, 100 ... rubber extrusion device, 115 ... rubber staying part 122 ... gear pumps, 122a ... gears, 122b ... bearings.

Claims (5)

An inlet for introducing unvulcanized rubber on one end side, a screw having a discharge port for unvulcanized rubber on the other end side, and kneading and transferring unvulcanized rubber introduced from the inlet; A compression screw extruder comprising a cylinder that houses the screw, and a die that is directly connected to the cylinder and that extrudes unvulcanized rubber discharged from the discharge port,
The volume of the unvulcanized rubber transfer space formed by the screw and the cylinder inner peripheral wall is decreased from the charging port side toward the discharge port side, and the unvulcanized rubber is transferred from the discharge port to the die. A compression screw extruder characterized in that the pressure is increased to a predetermined pressure capable of supplying a fixed amount. The compression screw extruder according to claim 1,
A compression screw extruder, wherein the space volume for transfer is gradually reduced from the inlet side toward the outlet side. A step of transferring unvulcanized rubber introduced from an inlet on one end side of the cylinder to a discharge port on the other end through the unvulcanized rubber transfer space formed by the screw and the cylinder inner peripheral wall; A method of compressing and extruding unvulcanized rubber, comprising a step of supplying the unvulcanized rubber discharged from a die to extrusion molding,
It has a pressurizing step of decreasing the transfer space volume from the charging port side toward the discharging port side and increasing the unvulcanized rubber to a predetermined pressure that can be quantitatively supplied to the die. Compression extrusion method for unvulcanized rubber. In the method of compression extrusion of unvulcanized rubber according to claim 3,
The step of pressurizing unvulcanized rubber by decreasing the transfer space volume from the inlet side toward the discharge port side reduces the transfer space volume stepwise. Rubber extrusion method. In the compression extrusion method of unvulcanized rubber according to claim 3 or 4,
A step of generating a backflow of the unvulcanized rubber in the space for transferring the unvulcanized rubber and sealing the pressure of the pressurized unvulcanized rubber. Compression extrusion method.

Images