Rotor with anti-wear device and means for attaching same

Abstract

In the field of mixing rubber mixtures, the invention is directed to a rotor (100) for use in an internal mixer having a mixing vessel in which the rotor rotates, the rotor having one or more blades (104), each blade having a tip (104a) with a profile having a predefined curvature; and an anti-wear device detachably fixed to the tip (104a) of at least one blade, the anti-wear device including a plate (110) with a profile defined by a lower surface (112) with a curvature complementary to that of the tip 104a and an upper surface (114) with a curvature complementary to that of a wall of the vessel to define, between them, a zone of minimum distance that allows passage of the mixture between the plate (110) and the wall of the vessel. The invention is also directed to an internal mixer having at least one mixing vessel in which the disclosed rotor (100) rotates.

Claims

1. A rotor for use in an internal mixer having a mixing vessel in which the rotor rotates, the rotor comprising: one or more blades, each blade having a tip, the profile of which has a predefined curvature; and an anti-wear device detachably fixed to the tip of at least one blade, the anti-wear device comprising a plate with a profile defined by a lower surface with a curvature complementary to the curvature of the tip and an upper surface with a curvature complementary to a curvature of a wall of the vessel to define, between them, a zone of minimum distance that allows a passage of a mixture between the plate and the wall of the vessel, wherein the plate comprises one or more cooling channels that extend axially along a length of the plate, the cooling channels being arranged along the profile of the plate and connecting to supply conduits that convey a corresponding coolant to the plate from a main conduit of the rotor.

2. The rotor of claim 1, wherein the profile of the plate is defined by a radius of curvature of the plate that is increasingly progressive in a clockwise direction so that the profile of the plate resembles a spiral.

3. The rotor of claim 1, further comprising an O-ring that is placed in a corresponding groove of the plate to effect sealing with respect to one of the supply conduits.

4. The rotor of claim 3, wherein the groove is a trapezoidal groove.

5. The rotor of claim 1, further comprising one or more retaining screws inserted into the plate to engage the rotor.

6. The rotor of claim 5, further comprising a mechanical fastening system.

7. The rotor of claim 6, wherein the mechanical fastening system comprises a positioning key and one or more worm gear systems.

8. The rotor of claim 7, wherein the positioning key comprises a parallel key with a top surface that engages a corresponding reinforcement of the lower surface of the plate, the positioning key engaging a corresponding top groove.

9. The rotor of claim 7, wherein the worm gear system comprises a gear wheel, a screwed axial locking member and a screw tangentially inserted into the rotor and axially locked by the screwed axial locking member so that rotation of the screw causes the gear wheel to rotate.

10. The rotor of claim 5, wherein each retaining screw consists of a screw head placed toward the upper surface of the plate.

11. The rotor of claim 10, further comprising a screw plug with a cylindrical structure having a thread that engages a corresponding thread of the rotor.

12. The rotor of claim 11, wherein the screw plug comprises a clamping member extending from an outer surface of the cylindrical structure to facilitate clamping of the screw plug relative to the rotor.

13. The rotor of claim 11, wherein the screw plug is placed toward the upper surface of the plate.

14. The rotor of claim 1, wherein the rotor comprises two blades and the blades are inclined in mutually opposite directions.

15. An internal mixer having at least one mixing vessel in which a rotor of claim 1 rotates.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The nature and the various advantages of the invention will become more obvious when reading the following detailed description, together with the attached drawings, in which the same reference numbers designate identical parts everywhere, and in which:

(2) FIG. 1 represents a planar section, taken perpendicular to the axis of rotation of the rotor of a known internal mixer.

(3) FIG. 2 represents a profile view of a one-piece rotor of the prior art.

(4) FIG. 3 represents a partial exploded view of a rotor and an anti-wear device of the invention.

(5) FIG. 4 represents a perspective view of a representative rotor with which the anti-wear device of FIG. 3 is used.

(6) FIG. 5 represents a perspective view of another representative rotor with which the anti-wear device of FIG. 3 is used.

(7) FIG. 6 represents a transparent perspective view, and FIG. 7 represents a partial perspective view, of the rotor and the anti-wear device of the invention.

(8) FIG. 8 represents a partial transparent view, and FIG. 9 represents a partial cross-sectional view, of the rotor and the anti-wear device of the invention.

(9) FIG. 10 represents a partial cross-sectional view of an embodiment of the invention that uses a sealing means between the rotor and the anti-wear device.

(10) FIG. 11 represents a partial cross-section view of the rotor and the anti-wear device fixed with a mechanical fastening system.

(11) FIG. 12 represents a worm gear system of the mechanical fastening system of FIG. 11.

(12) FIG. 13 represents a sectional view of a worm gear of the worm gear system of FIG. 12.

(13) FIGS. 14 and 15 represent an embodiment of the invention with a screw plug.

DETAILED DESCRIPTION

(14) Referring now to the figures, in which the same numbers identify identical components, FIG. 3 represents a rotor 100 supplied with an anti-wear device to increase the service life of the rotor and to increase its ability to resist abrasion by the rubber mixture. The rotor 100 is shown as a one-piece rotor as described above, this one with one or more blades 104. It is understood that the rotor may be selected from a configuration known in the art (for example, the rotor may be a tangential rotor, a meshing rotor, or an equivalent rotor). The rotor 100 is made of a metallic material such as steel (normal steel or high-strength steel). It is understood that another metal or equivalent material may be used (for example, stainless steel, titanium, etc.). A known chemical protective coating can be added on any part of rotor 100.

(15) The placement and attachment of the anti-wear device is realized with reference to a tip 104a of the blade 104. The rotor 100 is machined to create a tip 104a of the blade 104 that allows the connection with a plate 110. In a plane perpendicular to the axis of rotation of the rotor 100, a curvature of the profile of the 104a is defined by a center of curvature and a radius of curvature of the rotor.

(16) Referring again to FIG. 3 and furthermore to FIGS. 4 and 5, and also to FIG. 9, the anti-wear device includes a plate 110 that is detachably fixed to the rotor 100. A profile of the plate 110 is defined by a lower surface 112 and an upper surface 114 of the plate. The lower surface 112 has a curvature complementary to that of the tip 104a to facilitate direct placement of the plate 110 on the blade 104 (and/or on the blade 104′ in some embodiments). In FIG. 9, it is understood that the junction of the surfaces 112 and 104a can be circular, which facilitates the machining of the rotor 100 and the plate 110.

(17) The upper surface 114 has a curvature complementary to that of the vessel wall to define, between them, a zone of minimum distance that allows a passage of the mixture between the plate 110 and the vessel wall. In a plane perpendicular to the axis of rotation of the rotor 100, the profile of the plate 110 is defined by a predefined center of curvature of the plate and a predefined radius of curvature of the plate. In the embodiment shown, the profile of the plate 110 is defined by a radius of curvature that is increasingly progressive in a clockwise direction so that the plate profile resembles a spiral (i.e., the curve formed along the lower surface 112 rotates around a longitudinal axis).

(18) The profile of the plate 110 is therefore complementary to the rotor geometry and the vessel geometry as understood by a skilled person. Referring to FIG. 4, the representative rotor 100 has one machined blade 104 with an anti-wear device attached and a second unmachined blade 104′, and both blades have identical profiles. Referring to FIG. 5, the representative rotor 100 has two machined blades 104 with an anti-wear device attached to a first blade. The second blade is machined to ensure immediate attachment of an anti-wear device (not shown) so that both blades have identical profiles. For the two representative rotors 100, a rotor profile resembles the profile of a one-piece rotor.

(19) Referring again to FIGS. 3 to 5 and in addition to FIGS. 6 to 9, the plate 110 has cooling channels 120 that extend axially along a length of the plate 110. The cooling channels 120 are arranged along the profile of the plate 110 (see FIG. 9) and connect to supply conduits 122. The supply conduits 122 deliver a corresponding coolant (such as water or other known coolant) to the plate 110 from a main conduit 124 of the rotor 100 (see FIG. 8). The cooling channels 120, supply conduits 122 and main conduit 124 together form a control circuit within the plate 110 to regulate the temperature of the mixture during a mixing cycle as understood by the skilled person. For the embodiment shown, the plate 110 has four cooling channels 120, but the number of cooling channels can be adapted as needed.

(20) In some embodiments, the invention is also directed to sealing systems between the plate 110 and the rotor 100. Referring again to FIG. 9 and furthermore to FIG. 10, one embodiment of the invention includes a sealing means having an O-ring 150 that is placed in a groove 152 to effect the sealing with respect to a supply conduit 122. In this embodiment, the groove 152 is a trapezoidal groove in order not to lose the seal during assembly/disassembly of the anti-wear device. It is understood that the O-ring can be replaced by an equivalent seal or by another equivalent sealing means. It is also understood that the groove can be formed with another useful geometry.

(21) Referring again to FIGS. 3 to 10 and in addition to FIGS. 11 to 13, the plate 110 is detachably fixed to the tip 104a of the blade 104. In order to achieve torque transmission, this fixation is made by a mechanical fastening system including a positioning key (or “key”) 130 and one or more worm gear systems. It is understood that other mechanical fastening systems of the screw assembly type may be used.

(22) The key 130 is represented by a parallel key with a predetermined total length being fixed at the tip 104a by key screws 131 (see FIGS. 6 and 7). The key 130 engages in a corresponding groove (not shown) in the tip 104a so that an upper surface 130a of the key can engage a corresponding reinforcement 112a of the lower surface 112 of the plate 110. It is understood that the keying can be performed by an equivalent key (e.g., a parallel key of type A, B or C or a disc key).

(23) To detachably fix the plate 110 to the rotor 100, worm gear systems are used to tighten the corresponding retaining screws 137. The retaining screws 137 are inserted into the plate 110 to engage the rotor 100 (e.g., by engaging in a threaded fastener 141 of the rotor 100). Each retaining screw 137 has a screw head 137a that corresponds to the outer shape of the upper surface 114 of the plate 110, avoiding any mixture retention areas (see, for example, FIGS. 6 and 7).

(24) The worm gear system includes a gear wheel 143 (see FIGS. 11 and 12) with a screwed axial locking element 144 and a screw 145 (see FIGS. 12 and 13). The worm gear system may have guide elements 147 as understood by a skilled person. The screw 145 is inserted tangentially into the rotor 100 and is axially locked by the screwed axial locking element 144 so that rotation of the screw 145 causes the gear wheel 143 to rotate. The inside of the gear wheel 143 has an internal thread in which the screw 145 engages. In this configuration, the rotation of the toothed wheel will cause the tightening and loosening of the screw 137, allowing the fixation or release of the plate 110 and therefore its replacement if necessary.

(25) Referring again to FIGS. 14 and 15, in an embodiment of the invention, each screw 145 includes a screw plug 145a that protects the screw (see, for example, FIGS. 6 and 7). The screw plug 145a includes a clamping element 145b that extends from an outer surface 145c of a cylindrical structure 145d (see FIG. 14). The cylindrical structure 145d has a thread that will be screwed into a corresponding thread 149 of the rotor 100 (see FIG. 13). The clamping element 145b can have any geometry to facilitate the tightening of the screw plug 145a (for example, a hexagonal geometry can be chosen). To ensure a smooth surface of the outer surface 145c, the clamping element 145b breaks when the tightening reaches the desired torque (see FIG. 15). When loosening the worm gear assembly, the plug 145a will be destroyed to allow access to the screw 145.

(26) The screw heads 137a and the plug 145a are placed towards the upper surface 114 of the plate 110 according to its profile. The screw heads 137a and the plugs 145a are themselves part of the anti-wear device.

(27) The addition of an anti-wear device such as the plate 110 results in the same geometry as a one-piece rotor. Thus, the effects of the micro-dispersion of additives (provided by the passage between the blade and the vessel wall) and the distribution of components (achieved by the mass transfer of material between the vessels along the rotor 100 in each vessel) are not compromised.

(28) When the plate 110 is worn (either with heads and plugs or without heads and plugs), an in-situ intervention is carried out to change it. In addition, the fact that the worn parts of the rotors can be changed more easily, will allow more frequent changes and thus limit the gap variations between the vessel wall and the rotor. Downtime and associated costs are thus limited while rubber dispersion, rubber mixing performance and rubber mixture quality are preserved.

(29) The wear problem is simply solved with an anti-wear device that is easily machined and customized according to the precise rotor dimensions. The disclosed plate can be applied to newly purchased rotors as well as to already used rotors with a very short re-commissioning time. Replacement rotors that are needed to guarantee industrial production without loss of production can be limited only to the anti-wear devices of the invention. The plates and rotors can be supplied in one or more kits including at least one additional plate with each rotor. The plates are therefore available as needed to reduce the time and investment associated with the expected assembly/disassembly. In addition, the use of rotor tip plates does not change the operating parameters of the rotor.

(30) The addition of some coatings is not possible for the monobloc type rotors or for other known rotor types with a size and weight that prevent the addition of coatings (for example, in vacuum furnaces with limited dimensions). The disclosed invention makes it possible to apply on the anti-wear device coatings that include, for example, without limitation, physical vapor deposition (PVD) (e.g., chromium nitride), chemical vapor deposition (CVD) (e.g., titanium nitride) and their equivalents. Devices already having coatings incorporated therewith can be added in kits to give users more choice.

(31) The terms “at least one” and “one or more” are used interchangeably. Ranges that are presented as “between a and b” include the values “a” and “b”.

(32) While specific embodiments of the disclosed device have been illustrated and described, it is understood that various changes, additions and modifications may be made without deviating from the spirit and scope of this disclosure. Consequently, no limitations should be imposed on the scope of the invention described except those set forth in the claims annexed hereto.