FR3108866A1 - Rubber cooling system and mixer using such a system. - Google Patents

Abstract

COOLING SYSTEM FOR A RUBBER MIXER AND MIXER USING SUCH A SYSTEM. The invention relates to a cooling system which comprises a rotor 1 mounted on a spindle 10, the rotor forming with the spindle a cooling chamber 27 in which a cooling liquid is supplied and then evacuated by a cooling circuit 30-37 formed in the pin. Figure for abstract: figure 6

Description

Rubber cooling system and mixer using such a system.

The invention lies in the field of laboratory mixers and in particular bis-roll mixers.

Roll mixers are used to mix small quantities of substantially viscous materials, including plastics or rubbers. For example, in some cases, the objective is to homogenize a mixture composed of rubber and a complementary additive, and this automatically.

Such mixers comprise a mixing chamber and, in this chamber, two tangential rotors between which the material to be mixed is introduced. These rotors are mounted synchronously and counter-rotating, around respective axes parallel to each other. The rotors include wings through which the materials to be mixed are kneaded. Such mixers are known in particular from document FR 2 736 561 (A1) and EP 0 346 680 0 (B1).

As particularly illustrated by document EP 1 383 593 (B1), it is preferred to use for each rotor, a rotor comprising 4 alternately large and small wings.

The invention relates more particularly to a mixer using two rotors that are substantially identical to one another and arranged head to tail, each rotor comprising two small wings alternating with two large wings.

In a first phase, the materials undergo distributive mixing, that is to say at the macroscopic scale. The ingredients are evenly distributed in the mixer bowl; the materials travel between the different wings of the rotors.

In a second phase, the materials undergo dispersive mixing. The materials are each reduced to the microscopic scale.

In a third phase of mixing, the mixture is rolled as it passes at the end, where the space is narrow, in particular between the tank and the top of a wing or between two wings of respective rotors. There, the torque associated with the rotation of the rotors causes the different layers of the mixture to stretch, making the mixture laminar.

It also appears necessary to maintain a suitable temperature in the mixing chamber.

An object of the invention is to propose a mixer system and an associated mixing process which make it possible to optimize the mixing phases, in particular the distributive mixing and the dispersive mixing.

It appears that during distributive mixing, when using a rotor which comprises two large wings and two small alternate wings, the ratio of length between large and small wings, as well as the developed angle formed by each of the wings, takes on a particular importance.

It also appears that during dispersive mixing, the shape of the wing tip strongly affects the quality of the mixing. A large angle formed with the tangent shears the material little and promotes the overall distribution of the mixture within the mixing chamber; a small angle formed with this tangent promotes better dispersion but the shear stresses and the normal stresses increase.

It appears that during rolling, the top shape of the wings is of particular importance.

A second object of the invention is to provide means which make it possible to regulate the temperature in the chamber.

According to a first object of the invention, a rotor for a material mixer, in particular for forming a rubber, and intended to be mounted in rotation around a longitudinal axis comprises two large wings and two substantially helical small wings, one geometry of which, in a common cross section is defined from a base line and a median perpendicular to each other and secant to each other on the longitudinal axis, by a geometry line formed of a succession of segments including an approach segment and a top segment such as:

- the top segment extends perpendicular to the median at a distance equal to K.R9 (K times R9) from the longitudinal axis over a distance equal to K.LS3, where:

- R9 is between 55 and 70 millimeters, preferably substantially equal to 60 millimeters; And,

- LS3 is between 1 and 5 millimeters, preferably substantially equal to 2 millimeters;

- the approach segment extends in the extension and in front of the summit segment, in the normal direction of rotation of the rotor, it is circular and of radius K.RS2 around a center CS2 carried by the median, where RS2 is between 20 and 23 millimeters, preferably substantially equal to 23 millimeters;

where K is a proportionality coefficient preferably between 0.8 and 2, preferably approximately equal to 1.

Preferably, the approach segment extends below an intermediate straight line forming an angle with the base line and around the longitudinal axis, this angle being between 70 and 80 degrees of angle, preferably substantially equal to 75 degrees.

Preferably, the geometry line also comprises a pre-approach segment which extends in the extension and in front of the approach segment, circular and of radius K.RS1 around a center carried by the line base, where RS1 is between 70 and 75 millimeters, preferably substantially equal to 72 millimeters.

Advantageously, the line of geometry further comprises a trailing segment and a post-trailing segment such as:

- the post-leakage segment is circular, of radius RS1 around the point of intersection between the baseline and the median and extends, behind the median, between the baseline and an intermediate straight line, where :

- the intermediate straight line forms an angle, with the baseline and around the longitudinal axis, between zero and 40 degrees of angle, preferably between 25 and 35 degrees, even more preferably around 30 degrees; And,

- the radius of the post-leakage segment is between 35 and 45 millimeters, preferably substantially equal to 40 millimeters;

- the trailing segment connects the top segment and the post-trailing segment and extends to the rear of the top segment, is circular and of radius K.RS4, where RS4 is between 145 and 155 millimeters, preferably substantially equal at 149 millimeters.

Preferably, each small wing extends from a first transverse face of the rotor and comprises a crest line which forms with this face an angle of between 52 and 58 degrees, preferably approximately 55 degrees.

Preferably, each large wing extends from a second transverse face of the rotor and comprises a crest line which forms with this face an angle of between 42 and 48 degrees, preferably about 45 degrees.

Preferably, the small wings wrap around the longitudinal axis in a direction opposite to that in which the large wings wrap.

A longitudinal extension ratio between a longitudinal extension of the small wings relative to a length of the rotor is advantageously between 37% and 43%, preferably around 40%.

A longitudinal extension ratio between a longitudinal extension of the large wings relative to a length of the rotor is advantageously between 57% and 63%, preferably around 60%.

Preferably, the start of a small wing is out of phase, with respect to the start of a large wing which precedes it, by an angle measured around the longitudinal axis substantially equal to the angular course of this large wing.

The invention also relates to a mixer using two rotors according to the invention, mounted head to tail and in counter-rotation.

According to a second object of the invention, a rotor for a mixer of a material, in particular for forming a rubber, intended to be mounted in rotation about a longitudinal axis and intended to be mounted on a spindle comprises an axial passage, this passage comprising two bearings, each of the bearings being provided to come into engagement with a respective counter-bearing of the said pin, and an enlargement between the bearings. The enlargement is preferably formed such that a thickness between the enlargement is substantially constant.

According to a third object of the invention, a cooling system for a mixer comprising a rotor according to the invention and a spindle which forms, with the widening, a cooling chamber and means for circulating a cooling liquid in this bedroom.

The spindle advantageously comprises a constriction between the two counter-bearings, this constriction forming the chamber with the widening of the rotor.

The cooling means advantageously comprise a cooling circuit formed in the spindle to supply the cooling chamber with cooling liquid.

Means of circulation may include:

- an axial and blind bore formed in the spindle;

- a cannula mounted axially in the bore; And,

- a seal mounted between the cannula and the bore, to separate this bore into an upstream part, into which the cannula opens, and a downstream part, around the cannula, below this seal;

- at least one upstream crosspiece to connect the upstream part of the bore with the narrowing and at least one downstream crosspiece to connect the narrowing with the downstream part of the bore.

The invention also relates to a mixer using a cooling system according to the invention.

Embodiments and variants will be described below, by way of non-limiting examples, with reference to the appended drawings in which:

schematically represents a perspective view of a rotor according to the invention for a mixer;

is a half-view from above representing two rotors according to the invention in the mixing position:

is a longitudinal view of the rotor of Figure 1;

is an unrolling of the rotor of FIG. 1;

is a cross-sectional view along the plane VV of Figure 3;

is a descriptive diagram of the geometry of a tooth according to the section of FIG. 5;

is a longitudinal view of the rotor mounted on a spindle;

is an axial section of the rotor mounted on the spindle; And,

is a partial view of the section of Figure 8, illustrating a mode of cooling for the rotor.

Figure 1 illustrates a rotor 1 according to the invention. The rotor extends along a longitudinal axis X1. It includes four 2, 4 wings, including a pair of 2 small wings and a pair of 4 large wings. Each wing of a pair is identical to the other wing of the same pair, the wings of a same pair being arranged at 180 degrees from each other around the X1 axis. The pairs of wings each form a helix around the longitudinal axis X1, one twisted around the longitudinal axis X1 in a first direction F1, the other in a second direction F2 opposite to the first.

Each wing has a substantially triangular cross-section, with an enlarged base, closest to the longitudinal axis, and forms a crest 9, 92, 94 at its distal end. A wing shape is described in more detail later in this description with reference to Figures 4 to 6.

Each small wing 2 extends from a front face 6 of the rotor, visible in FIG. 1. Each large wing extends from a rear face 7 of the rotor, hidden in FIG. 1. The crest 9, 92, 94 of each wing, large or small, extends substantially to a common transverse plane PC, as particularly illustrated in Figures 3 and 4.

The common plane PC is located at a distance L2 from the front face 6, this distance L2 corresponding to a longitudinal dimension L2 of the crest 92 of a small wing 2. The common plane PC is located at a distance L4 from the rear face 7, this distance L4 corresponding to a longitudinal dimension L4 of the crest 94 of a large wing 4. The addition of the crest lengths L2, L4 corresponds to the longitudinal distance between the front and rear faces of the rotor 1; the addition of the peak lengths L2, L4 also corresponds to the overall length L1 of the rotor, i.e. L1=L2+L4.

Figure 2 partially illustrates a mixer 2 according to the invention. This mixer comprises two rotors 1; only a half-view of each of the rotors is shown. Each rotor is mounted integral with a respective spindle 10. Each rotor 1 and its respective spindle 10 are mounted in rotation F, FC around a respective longitudinal axis X1. The two X1 axes are parallel to each other. The rotors are mounted counter-rotating, i.e. one rotates in a direction F around its axis X1 and the other rotates in a contrary direction FC around its respective axis X1. Thus, the mixture moves between the rotors being sheared as shown by the arrows M.

We will now describe a preferred external geometry for the wings, in particular with reference to Figure 6. The description is made in the V-V section plane marked in Figure 5. The same description is valid for each of the wings in their current section, that is, with the exception of the vicinity of the plane like PC and the vicinity of the anterior face 6 and the posterior face 7.

The description is made relative to a baseline LB of the plane V-V. The baseline LB intersects the longitudinal axis X1 at a central point CC. A center line H extends up the figure from the center point CC.

The exterior geometry of the 2.4 wing is defined by a line LG consisting of a succession of segments S1-S5, circular or straight.

A first segment S1, called pre-approach segment, extends, to the left of the median H, between the base LB and a first intermediate line G12. The line G12 forms an angle AS1 with the base LB, around the central point CC. The first segment S1 is circular with radius RS1, around a center CS1. The center CS1 of the first segment is carried by the base LB and located to the right of the median H.

A second segment S2, called the approach segment extends, to the left of the median H, in the extension of the first segment S1, up to a third segment S3. The first segment and the second segment have a common tangent at their junction on the first intermediate line G12. The second segment S2 is circular with radius RS2, around a center CS2. The center CS2 of the first segment is carried by the median H.

The third segment S3, called the summit segment, extends perpendicularly to the median H, in the embedding of the second segment. It is distributed equally on either side of the median H. As particularly illustrated in Figure 5, the third segment has a length LS3 and is at a distance R9 from the base LB. The distance R9 corresponds to the overall radius R9 of rotor 1.

A fourth segment S4, called trailing segment, extends in the extension of the third segment, to the right of the median H, up to a second intermediate straight line G45. The junction point of the fourth segment and the third segment is a point of the ridge 9. The fourth segment S4 is circular with radius RS4.

A fifth segment S5, called the post-leakage segment, extends in the extension of the fourth segment S4, between the second intermediate line G45 and the base LB. The fifth segment and the fourth segment have a common tangent at their junction on the second intermediate line G45. The fifth segment S5 is circular with radius RS5, around the central point CC.

The first intermediate line G12 forms an angle AS1 with the base LB, to the left of the median H. The second intermediate line forms an angle AS5 with the base LB, to the right of the median H.

The first segment S1 and the second segment S2 constitute a leading edge for the wing; the fourth segment S4 and the fifth segment S5 constitute a trailing edge thereof.

To complete the geometric description of the wings, we will now describe their relative positions, relative to each other and relative to the longitudinal axis X1, with reference to Figure 4.

Figure 4 is a schematic developed figure of the envelope cylinder E of radius R9 around the longitudinal axis X1. The traces, on this cylinder E, of the crests 92 of the small wings 2 and crests 94 of the large wings 4, are represented there by segments.

The small wings 2 form an angle A2 with the anterior face 6 and the large wings 4 form an angle A4 with the posterior face 7. The start of a small wing 2 is out of phase by an angle AD, around the axis longitudinal X1, substantially equal to the angular path of the large wing 4 which precedes it.

In the example shown, the geometry of the wings is defined by the following approximate dimensions:

- angle A2 of a small wing with the front face 6: 55 degrees

- angle A3 of a large wing with the rear face 7: 45 degrees

- axial length L2 of a small wing 2: 60 millimeters,

- axial length L4 of a small wing 4: 90 millimeters,

- phase shift AD between large and small wing:

- overall length L1 of the rotor: 150 mm,

- overall radius of the R9 rotor: 60 millimeters,

- angle AS1 of the first intermediate line G12: 75 degrees,

- angle AS5 of the second intermediate line G45: 30 degrees,

- radius RS1 of the first segment S1: 72 millimeters,

- radius RS2 of the second segment S2: 23 millimeters,

- length LS3 of the third segment S3: 2 millimeters,

- RS4 radius of the fourth segment S4: 149 millimeters,

- radius RS5 of the fifth segment S5: 40 millimetres.

We will now describe a cooling system for the rotor 1. Indeed, the mixing causes a strong heating of the mixed material. To avoid an excessive rise in the temperature of the mixed material, the invention proposes a cooled rotor, so that it can sufficiently evacuate the heat.

The rotor comprises an axial passage 20 which extends from the front face 6 to the rear face 7 between them. The passage 20 comprises two cylindrical bearings 21 each close to a respective face 6, 7 and a widening 22 between the bearings. The enlargement has a length L22 substantially 60% of the length L1 of the rotor. The widening 22 is formed so that a thickness E22 between the widening and the outside of the rotor is substantially constant between the bearings 21, that is to say that it varies as little as possible according to a technique of manufacture used. Preferably, over the length of the enlargement, the thickness E22 of the rotor varies in a proportion of plus or minus 20%.

The spindle 10 comprises two cylindrical counter-bearings 23 arranged so that in the mounting position illustrated in Figures 7 to 9, each bearing 21 of the rotor is in sliding engagement on a respective counter-bearing 23 of the spindle 10. Keys 24 make it possible to maintain the rotor and the spindle integral with each other, in translation as in rotation. The spindle comprises, between the two counter-bearings 23, a constriction 26.

In the assembly position, the widening 22 and the narrowing 26 face each other, so that together they form a cooling chamber 27 between the bearings.

Pin 10 also includes a blind axial bore 30, that is to say axially closed by a bottom 31. Bottom 31 is formed at an anterior end 32 of bore 30. The pin also includes four upstream crosspieces 33 and four downstream crosspieces 34. The crosspieces 33, 34 connect the axial bore 30 to the outer surface of the spindle. The crosspieces are arranged so that they open into the chamber 27. The upstream crosspieces 33 are directed from front to rear from the axial bore 30, so that they open in the vicinity of the front bearing 21. The downstream crosspieces 34 are directed from rear to front from the axial bore 30, so that they open into the chamber 27, in the vicinity of the rear bearing 21.

The cooling system further comprises a cylindrical cannula 36, mounted coaxially in the bore 30. A clearance J36 is formed around the cannula 36 in the bore 30. A seal 37 is mounted around the cannula, between the cannula and the inner wall of the bore 30. Thus, the seal 37 ensures the maintenance of an anterior end of the cannula 36 and the regularity of the clearance J36 which separates the cannula from the wall of the bore. In addition, seal 37 divides bore 30 into an upstream zone 30A, between seal 37 and bottom 31, and a downstream zone 30B consisting of the annular space around the cannula, below seal 37. The cannula opens into the upstream zone 30A.

To cool the rotor 1, a cooling liquid is introduced through the cannula 36 into the upstream zone 30A. The liquid continues its way through the upstream crosspieces 33 into the chamber 37, where it is recovered from the heat generated by the mixing. The liquid then leaves the chamber 27 through the downstream crosspieces 34. The liquid is then evacuated through the downstream zone 30B.

Of course, the invention is not limited to the examples which have just been described. On the contrary, the invention is defined by the following claims.

It will indeed appear to those skilled in the art that various modifications can be made to the embodiments described above, in the light of the teaching which has just been disclosed to them.

Claims (7)

Rotor (1) for mixing a material, in particular for forming rubber, provided to be mounted for rotation about a longitudinal axis (X1) and provided to be mounted on a spindle (10), said rotor comprising an axial passage (20), said passage comprising two bearings (21), each of said bearings being arranged to engage a respective counter-bearing of said pin, and an enlargement (22) between the bearings. Rotor according to Claim 1, characterized in that the enlargement (22) is formed so that a thickness (E22) between the said enlargement and the exterior of the said rotor (1) varies in a proportion comprised between plus or minus 20% . Cooling system for a material mixer comprising a rotor according to one of Claims 1 and 2 and the spindle (10), characterized in that the said spindle (10) forms, with the widening (22), a cooling chamber (27) and means (30-37) for circulating a cooling liquid in said chamber (27). System according to Claim 3, characterized in that the spindle (10) comprises a constriction (26) between the two counter-bearings (23), the said constriction forming the chamber (27) with the widening (22) of the rotor (1 ). System according to one of Claims 3 and 4, characterized in that the circulation means (30-37) comprise a cooling circuit formed in the spindle (10) to supply the cooling chamber with cooling liquid. System according to one of Claims 3 and 4, characterized in that the circulation means (30-37) comprise:
- an axial bore (30) and blind formed in the spindle (10);
- a cannula (36) mounted axially in said bore; And,
- a seal (37) mounted between said cannula and said bore, to separate this bore into an upstream part (30A), into which said cannula opens, and, a downstream part, around the cannula, below said seal ; And,
- at least one upstream crosspiece (33) for connecting said upstream part (30A) of the bore with the narrowing and at least one downstream crosspiece (34) for connecting said narrowing with said downstream part (30B) of the bore. Material mixer, characterized in that it comprises at least one cooling system according to one of Claims 3 to 6.