CN108247886B

CN108247886B - Door for opening and closing discharge port of rubber mixing mill

Info

Publication number: CN108247886B
Application number: CN201711446065.9A
Authority: CN
Inventors: 东孝祐; 福谷和久; 山根泰明; 宫坂和夫; 植村正昭
Original assignee: Kobe Steel Ltd
Current assignee: Kobe Steel Ltd
Priority date: 2016-12-28
Filing date: 2017-12-27
Publication date: 2020-05-05
Anticipated expiration: 2037-12-27
Also published as: JP2018108732A; DE102017131307A1; CN108247886A

Abstract

The invention provides a door for opening and closing a discharge port of a rubber mixing mill, which can inhibit rubber as a mixing object from being involved in a rotor. The gate (32) opens and closes a discharge port (37) formed in the bottom of the chamber (31) of the rubber kneading machine (100), and the side inserted into the chamber (31) is formed in a laterally symmetrical mountain shape. In a cross section orthogonal to the longitudinal direction, the mountain-shaped outer shape (1) of the door (32) is an arc (1a) that is recessed downward from a door lower end corner (32a) that contacts the inner open end of the outlet (37) toward the vertically highest door top (32b) to the halfway point, and a straight line (1b) that is inclined with respect to the horizontal direction is formed from the halfway point to the door top (32 b).

Description

Door for opening and closing discharge port of rubber mixing mill

Technical Field

The present invention relates to a door provided at a discharge port formed at the bottom of a chamber of a rubber kneading machine and opening and closing the discharge port.

Background

Examples of such doors include doors described in patent documents 1 and 2.

The door (discharge door) described in patent document 1 has a shape determined as follows. Lines (L) connecting the contact points (D, E) of the discharge port and the discharge gate of the closed mixing chamber and the rotation centers (A, B) of the kneading rotors₁)、(L₂) The centers (Q) of the radii (S) are respectively arranged. Arcs passing through the contacts (D, E) are drawn with the center (Q) as a fulcrum. The intersection of the arcs is defined as the front end (P) of the discharge gate. The tip of the discharge gate is shaped so that when an arc of radius (R) is drawn with the center of rotation (O) of the discharge gate as a fulcrum, the tip (P) does not interfere with the contact (D) and the tip of the rotating kneading rotor, and the center (Q) is as close as possible to the centers of rotation (A) and (B) of the kneading rotors.

Patent document 1 describes the following: the discharge gate having the above-described shape can effectively knead the compound in the closed mixing chamber, and even when the compound which is easily in close contact with the mixing chamber is kneaded, the compound can be simply and effectively discharged without being entirely discharged and being sandwiched between the peripheral edge of the discharge port and the discharge gate or adhering to the gap between the peripheral edge of the discharge port and the discharge gate when the compound is discharged.

The door (drop door) described in patent document 2 has a shape defined as follows, and the ratio α (═ h/R) between the height h of the drop door and the radius R of the chamber is set to 0.6 ≦ α ≦ 0.8.

Patent document 2 describes the following: the drop door having the above-described shape can improve the mixing and dispersing action in the kneading chamber, and can obtain a uniform kneaded product in a short time. Further, since the space formed by the upper part of the drop door and the rotor is also reduced, the retention, fixation, and the like of the compounding agent and the kneaded material are also reduced.

Prior art documents

Patent document

Patent document 1: japanese patent No. 2562396

Patent document 2: japanese laid-open patent publication No. 8-332630

Disclosure of Invention

Problems to be solved by the invention

In some cases, a sheet-shaped rubber (rubber sheet) is fed into a rubber kneader as a material to be kneaded and kneaded. The rubber sheet may be wound around a rotor (kneading rotor) in a solid state (sheet state) at the initial stage of charging the rubber sheet into the chamber.

In both of the gates described in patent documents 1 and 2, the inclined surface on the kneading chamber side in contact with the rubber is a smooth and continuous curved surface. In the door described in patent document 2, a small portion of the top is a straight line extending in the horizontal direction. In the case of a door having such a shape, adhesion of rubber to the door can be suppressed. However, when the material to be kneaded is a rubber sheet, it is difficult for the rubber to remain in the gate portion. Therefore, the winding of the rubber into the rotor is easily generated.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a door capable of opening and closing a discharge port of a rubber kneading machine while suppressing the entrainment of rubber to be kneaded into a rotor.

Means for solving the problems

The present invention is a door having a left-right symmetrical chevron shape on the side inserted into a chamber of a rubber kneading machine, the door opening and closing a discharge port formed in the bottom of the chamber. The mountain-shaped outer shape of the door is an arc that is recessed downward from a corner of a lower end of the door that is in contact with an inner open end of the outlet toward a vertically highest door top portion and reaches a middle portion, and a straight line that is inclined with respect to a horizontal direction from the middle portion to the door top portion, in a cross-section orthogonal to the longitudinal direction.

Effects of the invention

According to the door having the above-described structure, the rubber can be retained to some extent in the vicinity of the door in the chamber, and thereby the entanglement of the rubber into the rotor can be suppressed.

Drawings

Fig. 1 is a cross-sectional view of a rubber kneading machine including a gate according to an embodiment of the present invention.

Fig. 2 is a view showing an outer shape (mainly, only one side) of a mountain-shaped portion of a door according to a plurality of embodiments including the door shown in fig. 1.

Fig. 3 is a graph showing a CV value ratio of a door having a shape according to the embodiment of the present invention with respect to a door having a conventional shape.

FIG. 4 is a diagram for explaining a method of drawing a door profile (straight line) in the range of 0.75L. ltoreq. x.ltoreq.L.

FIG. 5 is a diagram for explaining a method of drawing a door profile (arc) in the range of 0. ltoreq. x.ltoreq.0.75L.

Fig. 6 is a cross-sectional view of a longitudinal center portion of the door according to the embodiment of the present invention.

Fig. 7 is a cross-sectional view of the door according to the embodiment of the present invention, taken along the longitudinal direction.

Description of the reference numerals

1 to 8 shape

1 a-8 a arc

1b to 8b straight line

31 chamber

32 door

32a door lower corner

32b door top

37 discharge port

38 recess

40 thermometer

100 rubber mixing mill

Detailed Description

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

(construction of rubber kneading machine)

The structure of a rubber kneading machine 100 including a gate 32 according to an embodiment of the present invention will be described with reference to fig. 1. The rubber to be kneaded by the rubber kneader provided with the gate of the present invention is not limited to rubber (rubber sheet) having a sheet shape.

The rubber kneading machine 100 is a device for kneading rubber as a material to be kneaded, and includes a supply unit 20 and a kneading unit 30. The supply unit 20 is a part that supplies the material to be kneaded to the kneading unit 30, and includes a hopper 21, a material supply cylinder 22, and a cylinder device 23.

The rubber (material to be kneaded) to be kneaded is fed from the outside of the rubber kneader 100 to the hopper 21. The material supply cylinder 22 is a cylinder through which the material to be kneaded can pass. The upper part of the material supply cylinder 22 communicates with the hopper 21.

The cylinder device 23 is a device for pressing the material to be kneaded from the material supply cylinder 22 into the kneading section 30 (a kneading chamber 33 described later). The cylinder device 23 is, for example, a pneumatic actuator. The cylinder device 23 includes a cylinder 24, a piston 25, a piston rod 26, and a floating weight 27.

The floating weight 27 connected to the lower end of the piston rod 26 is a member for pressing the material to be kneaded, which is fed from the hopper 21, into the kneading chamber 33.

The kneading section 30 is a section for kneading materials to be kneaded, and includes a chamber 31, a gate 32 for opening and closing (opening and closing) a discharge port 37 formed in the bottom of the chamber 31, and a pair of rotors 34 and 35 (kneading rotors).

The chamber 31 is a portion in which a kneading chamber 33 is formed, and a supply port 36 for a material to be kneaded is provided at an upper portion thereof. The floating weight 27 is lowered from above the supply port 36 toward the supply port 36.

The kneading chamber 33 is a space for kneading the materials to be kneaded. The longitudinal cross-sectional shape of the kneading chamber 33 is an eyebrow shape. The vertical cross-sectional shape is a cross-sectional shape of the kneading chamber 33 when viewed from the axial direction of the

rotors

34 and 35.

The door 32 is driven by an actuator to open and close the discharge port 37 of the chamber 31. The discharge port 37 of the chamber 31 is closed by the gate 32 during the kneading of the material to be kneaded, and the gate 32 is opened when the rubber (kneaded material) having been kneaded is discharged from the chamber 31. The actuator that drives the door 32 is, for example, a rotary actuator (rotary actuator). The gate 32 (gate shape) greatly affects the degree of kneading of the rubber kneaded by the

rotors

34 and 35 in the chamber 31 (in the kneading chamber 33).

The

rotors

34 and 35 are members for kneading the materials to be kneaded, and are disposed in the chamber 31 (in the kneading chamber 33). The

rotors

34, 35 rotate about their central axes. Fig. 1 shows the center of rotation C of the

rotors

34, 35. The

rotors

34 and 35 rotate in different directions from each other so that the facing portions move downward.

(shape of door)

The door 32 will be described in detail. The side of the door 32 inserted into the chamber 31 is formed in a mountain shape. The mountain shape is a bilaterally symmetric shape in a cross-sectional view orthogonal to the longitudinal direction of the door 32.

See, for example, the portion of door 32 in fig. 1 and outline 1 in fig. 2. In the door 32 according to the embodiment of the present invention, the mountain-shaped outer shape 1 is formed by an arc 1a recessed downward from a door lower end corner 32a contacting an inner opening end of the outlet 37 toward a door top 32b highest in the vertical direction to a middle portion, and a straight line 1b inclined from the middle portion to the door top 32b with respect to the horizontal direction in a cross section orthogonal to the longitudinal direction. That is, the outer shape 1 of the mountain-shaped portion of the door 32 is formed by only one arc 1a and one straight line 1b from the door lower end corner 32a toward the door top 32b between the door lower end corner 32a and the door top 32 b. Fig. 2 is a cross-sectional view of the door orthogonal to the longitudinal direction, showing the outer shape (mainly, only one side) of the mountain-shaped portion of the door. The one-dot chain line in fig. 2 is a center line.

Fig. 2 shows a total of eight door shapes from the outer shape 1 to the outer shape 8 according to the embodiment of the present invention. As shown in fig. 2, in the outer shapes 1 to 8, the door lower corner 32a and the door top are each formed by only one arc 1a to 8a and one straight line 1b to 8b from the door lower corner 32a toward the door top. Note that the outer shape of the door (the eccentric door) shown by the broken line labeled "prior art" in fig. 2 is a curved surface that is smoothly continuous throughout except for the top of the door. Note that a small portion of the top of the prior art door is a straight line extending in the horizontal direction.

The present inventors evaluated the total of eight gates having the outer shapes 1 to 8 shown in fig. 2 and the gate having the conventional shape shown in fig. 2 with respect to the entrainment of the rubber into the

rotors

34 and 35, the influence on the degree of kneading of the rubber, and the adhesion of the rubber to the gate. The evaluation results are shown in table 1. The rubber as the material to be kneaded is a rubber (rubber sheet) in which the rubber is in a sheet form in an initial state (a state at the time of charging).

[ TABLE 1 ]

Door with a door panel	Roll in	Influence on degree of mixing	Attachment of
				Prior Art	×	-	○
Outer shape 1	○	◎	○
				Outer shape 2	○	◎	○
Outer shape 3	○	○	○
				Outer shape 4	○	×	×
Outer shape 5	○	○	○
				Outer shape 6	○	○	○
Outer shape 7	○	◎	○
				Outer shape 8	○	○	×

[ description of Table 1 ]

Roll-in ○ has roll-in inhibiting effect

X: no rolling-in inhibiting effect

Mixing degree of ◎: Excellent

○ good

X: difference (D)

Attachment ○ No attachment

X: always has attachment

[ concerning the winding-in of rubber ]

In contrast, in the gate of the present invention, as in the outer shapes 1 to 8 shown in fig. 2, the inclined surface on the kneading chamber 33 side in contact with the rubber is formed as arcs 1a to 8a recessed downward from the gate lower end corner 32a toward the gate top portion to the halfway portion, and as in the outer shapes 1 to 8 shown in fig. 2, straight lines 1b to 8b inclined from the halfway portion to the gate top portion are formed, and by forming the gate top portion side as a straight line inclined from the horizontal direction, the rubber can be retained to some extent in the vicinity of the gate in the chamber 31 (in the kneading chamber 33), whereby the entanglement of the rubber into the

rotors

34 and 35 can be suppressed, that is, all eight gates in total in the outer shapes 1 to 8 have the effect of suppressing the entanglement of the rubber, while the gate in the prior art shape has no effect of suppressing the entanglement of the rubber, and this evaluation is shown by ○ × in table 1.

[ Effect on kneading degree ]

FIG. 3 is a graph showing CV value ratios of the doors having the outer shapes 1 to 8 of the embodiment of the present invention shown in FIG. 2 to the doors having the conventional shape shown in FIG. 2. Here, the CV value is an index by which the distribution mixing progress of the rubber can be judged as the smaller the value. The CV value ratio is a CV value (ratio of CV values) of each gate when the CV value of the gate having the conventional shape shown in fig. 2 is 1. The smaller the CV value ratio means, the more improved the distributive mixing of the rubber. Fig. 3 is a graph showing a CV value ratio after 10 rotations of

rotors

34 and 35 when flow analysis is performed on nine gates in total including the prior art.

As is apparent from fig. 3, the doors having improved CV values by 10% or more as compared with the doors (eccentric doors) of the prior art are three doors of the outer shape 1, the outer shape 2, and the outer shape 7, and the doors having improved CV values by less than 10% are four doors of the outer shape 3, the outer shape 5, the outer shape 6, and the outer shape 8, and it is noted that the doors of the outer shape 4 have slightly deteriorated CV values as compared with the doors of the prior art, and these results are represented by ◎, ○, and x in table 1.

[ adhesiveness to rubber ]

The adhesion of rubber to each gate was evaluated by flow analysis of a total of nine gates including the prior art. As shown in table 1, the adhesion of rubber was not observed in the doors of the prior art shape and the doors of the outer shapes 1 to 3 and 5 to 7 of the embodiments of the present invention, but was observed in the doors of the outer shapes 4 and 8 of the embodiments of the present invention.

[ regarding a more preferable door shape ]

As described above, in the cross-section orthogonal to the longitudinal direction, the outer shape of the mountain shape is an arc that is concave downward from the gate lower end corner 32a toward the gate top portion to the middle portion, and a straight line that is inclined with respect to the horizontal direction is formed from the middle portion to the gate top portion, whereby the rubber can be retained to some extent in the vicinity of the gate in the chamber 31 (in the kneading chamber 33), and the entrainment of the rubber into the

rotors

34 and 35 can be suppressed.

<1. door capable of improving distribution mixing of rubber while suppressing the entanglement of rubber >

A more preferable shape of the door will be described with reference to fig. 2, 4, and 5. Here, in a cross-section orthogonal to the longitudinal direction, the door lower end corner 32a is set as the origin O, the horizontal direction is set as the x-axis, and the direction from the door lower end corner 32a toward the door top in the horizontal direction is set as the positive x-axis (see the x-axis arrow in fig. 4 and 5). The vertical direction is defined as the y-axis, the direction from the door lower end corner 32a toward the door top in the vertical direction is defined as the positive y-axis (see the arrow on the y-axis in fig. 4 and 5), and the horizontal distance between the origin O and the door top is defined as L. In the shapes 1-8, the range of x being more than or equal to 0 and less than or equal to 0.75L is respectively set as an arc 1 a-8 a, and the range of x being more than or equal to 0.75L and less than or equal to L is set as a straight line 1 b-8 b.

In the distribution mixing (kneading) of rubber, the influence of the shape of the gate top side of the gate is large. Therefore, the mountain-shaped region of the door in the range of 0.75L. ltoreq. x.ltoreq.L is a region where the distribution mixing of the rubber is improved.

The door profile capable of improving the distribution mixing of rubber in the range of 0.75L-x-L of the door is a straight line which passes through a region satisfying the following formula (1) and is inclined with respect to the horizontal direction.

tan (theta +15) × x + b2 ≦ y ≦ tan (theta +13) × x + b1 … … formula (1)

θ: an inclination angle of a tangent line at an origin O of a circle having a radius R passing through the origin O with respect to a horizontal direction with a rotation center C of a rotor of the rubber kneading machine 100 as a center (see FIG. 4)

R: the radius of a circle passing through the origin O with the rotation center C of the rotor of the rubber kneading machine 100 as the center (see FIG. 4), and the radius of the circular portion of the inner wall surface of the chamber 31 (see FIG. 1)

b 1: an intercept (y-coordinate of the intercept) of a straight line having an inclination of tan (θ +13) and passing through a lower point P1 of two intersections of a circle having a radius R1 of 0.99R and passing through the gate top and a straight line x ═ L passing through the center C of rotation of the rotor (see fig. 4)

b 2: an intercept (y-coordinate of the intercept) of a straight line having an inclination of tan (θ +15) and passing through a lower point P2 of two intersections of a circle having a radius R2 of 1.06R and passing through the gate top and a straight line x ═ L passing through the center C of rotation of the rotor (see fig. 4)

Wherein the slope of the straight line is tan (theta-14) or more.

The straight line x ═ L passing through the gate top is also a perpendicular bisector of a line segment connecting the centers of the two

rotors

34 and 35. The left linear expression in expression (1) represents a straight line 8b of the outer shape 8 (see fig. 2), and the right linear expression in expression (1) represents a straight line 1b of the outer shape 1 (see fig. 2).

As can be seen from fig. 3 and table 1, the door of profile 4 is a door that does not improve the distributive mixing of the rubber. This is because the slope of the straight line 4b of the profile 4 is gentle, thereby stagnating the flow of rubber at the top of the door. The slope of the straight line 4b of the outline 4 is tan (θ -14). Therefore, the gate profile capable of improving the distributive mixing of the rubber in the range of 0.75L. ltoreq. x.ltoreq.L of the gate needs to be a straight line passing through the region satisfying the above formula (1) and having a slope of tan (θ -14) or more.

Then, the gate shape capable of improving the distributive mixing of the rubber in the range of 0. ltoreq. x.ltoreq.0.75L is an arc having a constant curvature passing through a region satisfying the following formula (2).

Wherein y satisfies the following formula (3).

θ: an inclination angle of a tangent line at an origin O of a circle having a radius R passing through the origin O with respect to a horizontal direction with a rotation center C of a rotor of the rubber kneading machine 100 as a center (see FIG. 5)

R: the radius of a circle passing through the origin O with the rotation center C of the rotor of the rubber kneading machine 100 as the center (see FIG. 5), and the radius of the circular portion of the inner wall surface of the chamber 31 (see FIG. 1)

The left-side circular arc formula in formula (2) is a partial circular arc formula of a circle having a center C2 and a radius R4 of 1.1R shown in fig. 5, and the right-side circular arc formula in formula (2) is a partial circular arc formula of a circle having a center C1 and a radius R3 of 0.9R shown in fig. 5. The left arc formula in formula (2) is an arc formula including an arc 7a of an outer shape 7 and an arc 8a of an outer shape 8 (see fig. 2), and the right arc formula in formula (2) is an arc formula including an arc 1a of an outer shape 1 and an arc 2a of an outer shape 2 (see fig. 2).

In the case of the gate shape capable of improving the distribution mixing of rubber while suppressing the entrainment of rubber into the

rotors

34 and 35, when the description is summarized, in the gate shape, the outer shape of the range of 0. ltoreq. x.ltoreq.0.75L is defined as an arc of constant curvature passing through the region satisfying the above expression (2) and the outer shape of the range of 0.75L. ltoreq. x.ltoreq.L is defined as a straight line passing through the region satisfying the above expression (1) with respect to the mountain-shaped portion of the gate. Wherein the slope of the straight line is tan (theta-14) or more.

<2 > door with less adhesion of rubber to the door while suppressing the entrainment of rubber and improving the distributive mixing of rubber >

According to table 1, of the outer shapes of the mountain-shaped portions of the door in which the entrainment of the rubber into the

rotors

34 and 35 can be suppressed and the distribution mixing of the rubber can be improved and the adhesion of the rubber to the door is difficult, the outer shape in the range of 0. ltoreq. x.ltoreq.0.75L is set as an arc of a constant curvature that further passes through the region satisfying the following expression (4), and the outer shape in the range of 0.75L. ltoreq. x.ltoreq.l is set as a straight line that further passes through the region satisfying the following expression (6).

Wherein y satisfies the following formula (5).

tan (theta +8) × x + b3 ≦ y ≦ tan (theta +13) × x + b1 … … formula (6)

b 3: an intercept (y-coordinate of the intercept) of a straight line having an inclination of tan (θ +8) and passing through a lower point P2 of two intersections of a circle having a radius R2 of 1.06R and passing through the gate top with a straight line x passing through the gate top equal to L (see fig. 4).

Wherein the slope of the straight line is tan (theta-14) or more.

θ, R, and b1 in the formulae (4) to (6) are the same as θ, R, and b1 in the formulae (1) to (3).

The left circular arc formula in formula (4) is a partial circular arc formula of a circle having a center C2 and a radius R4 of 1.05R shown in fig. 5, and the right circular arc formula in formula (4) is a partial circular arc formula of a circle having a center C1 and a radius R3 of 0.9R shown in fig. 5. The left arc formula in formula (4) is a arc formula including an arc 5a of an outer shape 5 and an arc 6a of an outer shape 6 (see fig. 2), and the right arc formula in formula (4) is a arc formula including an arc 1a of an outer shape 1 and an arc 2a of an outer shape 2 (see fig. 2).

The left linear expression in equation (6) represents a straight line 6b (see fig. 2) of the outer shape 6, and the right linear expression in equation (6) represents a straight line 1b (see fig. 2) of the outer shape 1.

<3 > door capable of further improving distribution and mixing of rubber than the door >

According to table 1, of the outer shapes of the mountain-shaped portions of the door where the rubber is less likely to adhere to the door, the outer shape in the range of 0.75L ≦ x ≦ L is set as a straight line passing through the region satisfying the following expression (7), while suppressing the entrainment of the rubber into the

rotors

34 and 35 and further improving the distribution mixing of the rubber.

tan (theta +1) × x + b4 ≦ y ≦ tan (theta +13) × x + b1 … … formula (7)

b 4: an intercept (y-coordinate of the intercept) of a straight line having tan (θ +1) as a slope of a lower point P2 out of two intersection points of a circle having a radius R2 of 1.01R and a straight line x passing through the gate top as a center of rotation C of the rotor is shown in fig. 4.

Wherein the slope of the straight line is tan (theta-14) or more.

θ in the formula (7) is the same as θ in the above-described formulas (1) to (3).

The left linear expression in equation (7) represents a straight line 2b (see fig. 2) of the outer shape 2, and the right linear expression in equation (7) represents a straight line 1b (see fig. 2) of the outer shape 1.

(thermometer mounting to door)

The installation of the thermometer 40 to the door 32 will be described with reference to fig. 6 and 7. As shown in fig. 6 and 7, the center portion in the longitudinal direction of the door top portion 32b is a recessed portion 38. A hole 39 is opened in the recess 38, and a thermometer 40 is inserted into the hole 39 and fixed (installed). The recess 38 is partially formed into a curved surface as shown in fig. 6.

In a cross-section orthogonal to the longitudinal direction, the mountain-shaped outer shape 1 of the door 32 at a portion other than the recess 38 is formed by an arc 1a and a straight line 1b over the entire length of the door 32 in the longitudinal direction. The thermometer 40 is provided so as not to protrude upward beyond the door top 32 b.

According to the above configuration, it is possible to prevent rubber from adhering to the vicinity of the door 32 where the thermometer 40 is provided.

Claims

1. A door for opening and closing a discharge port of a rubber kneading machine, which opens and closes a discharge port formed in the bottom of a chamber of the rubber kneading machine, and has a laterally symmetrical mountain shape on the side inserted into the chamber,

the mountain-shaped outer shape is an arc which is recessed downward from a corner portion of the lower end of the door contacting the inner open end of the discharge port toward the vertically highest door top portion to a middle portion thereof in a cross-sectional view orthogonal to the longitudinal direction, and a straight line which is inclined with respect to the horizontal direction from the middle portion to the door top portion,

in a cross-section orthogonal to the longitudinal direction, when the door lower end corner portion is set as an origin, the horizontal direction is set as an x-axis, a direction from the door lower end corner portion toward the door top portion in the horizontal direction is set as positive of the x-axis, the vertical direction is set as a y-axis, a direction from the door lower end corner portion toward the door top portion in the vertical direction is set as positive of the y-axis, and a distance between the origin and the door top portion in the horizontal direction is set as L, the outer shape in a range of 0. ltoreq. x.ltoreq.0.75L is set as the circular arc of a certain curvature that passes through a region satisfying formula (1), and the outer shape in a range of 0.75L. ltoreq. x.ltoreq.l is set as the straight line that passes through a region satisfying formula (3),

wherein the slope of the straight line is tan (theta-14) or more,

wherein y satisfies the following formula (2),

tan (theta +15) × x + b2 ≦ y ≦ tan (theta +13) × x + b1 … … formula (3)

θ: an inclination angle of a tangent line at the origin of a circle passing through the origin with respect to a horizontal direction centered on a rotation center of a rotor of a rubber kneading machine;

r: a radius of a circle passing through the origin with a rotation center of a rotor of the rubber kneading machine as a center, and a radius of a circular portion of an inner wall surface of the chamber;

b 1: an intercept of a straight line having a slope of tan (θ +13) and passing through a lower point of two intersection points of a circle having a radius of 0.99R and passing through a straight line x ═ L passing through the gate top, the circle having a center at a rotation center of the rotor;

b 2: and an intercept of a straight line having a slope tan (θ +15) and passing through a lower point of two intersection points of a circle having a radius of 1.06R and passing through the rotation center of the rotor and a straight line x ═ L passing through the gate top.

2. The door for opening and closing the discharge port of a rubber kneading machine according to claim 1,

the outline of the range of 0. ltoreq. x.ltoreq.0.75L is set as the circular arc of a certain curvature further passing through the region satisfying formula (4), and the outline of the range of 0.75L. ltoreq. x.ltoreq.L is set as the straight line further passing through the region satisfying formula (6),

wherein y satisfies the following formula (5),

b 3: and an intercept of a straight line having a slope of tan (θ +8) and passing through a lower point of two intersection points of a circle having a radius of 1.06R and passing through the gate top with a straight line x ═ L centered on the rotation center of the rotor.

3. The door for opening and closing the discharge port of a rubber kneading machine according to claim 2,

the outline in the range of 0.75L ≦ x ≦ L is set as the straight line further passing through the region satisfying formula (7),

b 4: and an intercept of a straight line having a slope tan (θ +1) and passing through a lower point of two intersection points of a circle having a radius of 1.01R and passing through the gate top with a straight line x ═ L centered on the rotation center of the rotor.

4. The door for opening and closing the discharge port of a rubber kneading machine according to any one of claims 1 to 3,

the central portion in the longitudinal direction of the door top is provided as a concave portion,

a thermometer is arranged in the concave part,

the mountain-shaped outer shape of the portion other than the concave portion is formed by the arc and the straight line in a cross-section orthogonal to the longitudinal direction.