Abstract:
A closed kneader mixing machine including a tilting mixing chamber and a pair of counter-rotating intermeshing rotors rotatably mounted within the tilting mixing chamber. The counter-rotating intermeshing rotors may be synchronous rotors.

Description:
[0001]     This application claims priority to provisional application Ser. No. 60/596,510, filed Sep. 29, 2005, the disclosure of which is hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     This invention relates generally to batch type polymer mixers and more particularly to a kneader mixer with intermeshing rotors.  
         [0003]     There are two different types of internal mixers used in the industry at large. The first type is more commonly known as a “Banbury” type intensive mixer and the second type is known as a “Kneader”. The primary difference between the two types of mixers is the rotor, throat, chamber and floating weight design. Banbury® mixers also discharge the batch through a bottom door where as the kneader tilts to discharge the batch.  
         [0004]     A closed kneader is composed of a kneading tank or chamber for holding kneaded material, a pair of rotors, which are provided at both ends with rotor drive shafts passing through side walls of the chamber, and which consist of a rotor shaft forming a rotor blade for kneading the material kneaded in the chamber, and a pressure cover. When kneading material, the kneaded material is poured into the chamber when the pressure cover is opened upward. The pressure cover is let down and the rotors are rotatably driven with a driving means such as a motor, etc., connected, to the rotor drive shafts.  
         [0005]     Traditional kneaders have two counter rotating rotors with each mixing rotor having two thin wings affixed on it. The two wing rotors typically rotate at different speeds through connecting gears. The wings move material from one portion of the chamber to the other while also providing material movement along the rotor axis. These kneaders do not have intermeshing rotors and therefore can have differential rotor speeds.  
         [0006]     Typically, conventional kneaders have a one piece rotor design that includes a rotor shaft with two wings welded on the shaft. The conventional kneader&#39;s blades are typically long, high and narrow. Water cooling is provided through a passage in the rotor shaft and small jackets in each wing. This cooling method is usually not sufficient for single pass mixing.  
         [0007]     During kneading, heat is produced within the kneaded material, in the chamber and also by the rotor shaft because of internal heat generation due to shearing, dispersion, etc., during kneading. For these reasons, insufficient cooling often occurs in the inner part of the kneaded material with respect to the kneading speed, i.e., the speed of heat generation, in the case of a kneaded material of large thickness and low thermal conductivity (especially rubber, etc.), even if cooling water is circulated through the chamber wall and the rotor shaft.  
         [0008]     While sufficient cooling can be provided for the kneaded material with little increase of internal temperature in the kneaded material by using a kneader with a small mixing volume, such a machine is inferior in productivity and therefore unrealistic as a mass production unit.  
         [0009]     In the closed kneader, while a general kneading process is divided into a primary kneading for mixing without containing any vulcanizing agent, and a secondary kneading for performing kneading by mixing the kneaded material, which has already been subjected to a certain kneading process in the primary kneading, with a vulcanizing agent, the kneading material temperature must be kept below a certain level (variable depending on the material) for mixing in the vulcanizing agent.  
         [0010]     Generally, convention kneaders require processing a batch in two passes. Either by stopping the mixing and allowing the batch to cool before completing the mixing, or by discharging the batch into a second kneader.  
         [0011]     Conventional kneaders typically use pneumatic pressure to push the batch down into the rotors and mixing chamber with a floating weight (ram). This pneumatic system can be unreliable and inconsistent. The pneumatic ram moves uncontrollably with the ram position being typically controlled by the rotor dragging force as well as the size of rubber or polymer pieces being forced into the rotors.  
         [0012]     The foregoing illustrates limitations known to exist in present kneader mixers. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.  
       SUMMARY OF THE INVENTION  
       [0013]     A closed kneader mixing machine is disclosed that comprises: a tilting mixing chamber having an open upper end; a pair of counter-rotating intermeshing rotors rotatably mounted within the tilting mixing chamber. The intermeshing rotors may also be synchronous.  
         [0014]     The closed kneader mixing machine rotors may be formed from a hollow cylinder with a spiral wing extending radially outward from the outer surface of the hollow cylinder. The spiral wing can extend from one end of the hollow cylinder towards the other end of the hollow cylinder. The spiral wing has a width that is greater than the radial extent of the spiral wing. The rotor may further include poly-sided nogs on the hollow cylinder. In one embodiment, a pair of poly-sided nogs are provided. The poly-sided nogs may have a pentagon shape. Nogs of other shapes may be provided on the rotor.  
         [0015]     The rotor may have a spiral cooling groove on an interior surface thereof. The spiral cooling groove may further extend into at least one of the spiral wing and at least one nog.  
         [0016]     In addition, a closed kneader mixing machine is disclosed that comprises: a tilting mixing chamber tiltable between an upright position and a tilted downward discharge position; and at least one hydraulic locking pin engaging the tilting mixing chamber when the tilting mixing chamber is in the upright position.  
         [0017]     In one embodiment, the mixing chamber comprises two semi-circular sub-chambers and the radius of each rotor being about 60 to about 80%, or about 70% of the sub-chamber radius. Alternatively, or in addition, each rotor has a wing extending radially towards the other rotor to between 3 mm and 6 mm of the outer surface of the other rotor, or to between 3 mm and 14 mm of the outer surface of the other rotor.  
         [0018]     Alternatively, this may be accomplished by providing a closed kneader mixing machine comprising: a tilting mixing chamber tiltable between an upright position and a tilted downward discharge position, the tilting mixing chamber having an open upper end; a movable ram, the movable ram being movable between a position closing the tilting mixing chamber open upper end and a position distal the tilting mixing chamber open upper end; and a hydraulic operator biasing the movable ram to the position closing the tilting mixing chamber open upper end.  
         [0019]     In a further disclosed embodiment, this is accomplished by providing a closed kneader mixing machine comprising: a tilting mixing chamber having an open upper end, the tilting mixing chamber comprising two semi-circular sub-chambers, each sub-chamber having a radius; and a pair of counter-rotating intermeshing rotors rotatably mounted within the tilting mixing chamber, each rotor having radius, the rotor radius being between about 60% and 80% of the sub-chamber radius.  
         [0020]     In yet another disclosed aspect of the present intermeshing kneader, this is accomplished by providing a closed kneader mixing machine comprising: a tilting mixing chamber having an open upper end; a pair of counter-rotating intermeshing rotors rotatably mounted within the tilting mixing chamber, each rotor comprising a hollow cylinder having a spiral groove on an inside surface of the hollow cylinder; and a source of cooling liquid, the source of cooling liquid being in fluid communication with each rotor hollow cylinder spiral groove.  
         [0021]     In a further embodiment of the disclosed kneader mixer, this is accomplished by providing a closed kneader mixing machine comprising: a tilting mixing chamber having an open upper end, the mixing chamber having a predetermined volume; a pair of counter-rotating intermeshing rotors rotatably mounted within the tilting mixing chamber; and a motor drivingly engaging the rotors to rotate the rotors, the motor comprising 3 to 7 HP/liter of mixing chamber volume.  
         [0022]     In yet a further alternate aspect of the disclosed kneader this is accomplished by providing a mixing and kneading device having a pair of rotors, each rotor comprising: a hollow cylinder; a spiral wing on the hollow cylinder, the spiral wing extending radially outward from an outer surface of the hollow cylinder and extending axially in a spiral manner from one end of the hollow cylinder towards the other end of the cylinder; and a pair of poly-sided nogs on the hollow cylinder, each poly-sided nog extending radially outward from the outer surface of the hollow cylinder, a poly-sided nog being proximate each end of the hollow cylinder. The pair of rotors can be intermeshing rotors, and further, can be synchronous rotors. The nogs may have other shapes than poly-sided. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES  
       [0023]      FIG. 1A  is a perspective view of illustrating an intermeshing rotor kneader mixer;  
         [0024]      FIG. 1B  is a second perspective view of the intermeshing rotor kneader shown in  FIG. 1A ;  
         [0025]      FIG. 2  is a perspective view of an intermeshing rotor for use with the mixer shown in  FIG. 1A ;  
         [0026]      FIG. 3  is a second perspective view of the intermeshing rotor shown in  FIG. 2 ;  
         [0027]      FIG. 4A  is a first side view of the intermeshing rotor shown in  FIG. 3 ;  
         [0028]      FIG. 4B  is a second side view of the intermeshing rotor shown in  FIG. 3 ;  
         [0029]      FIG. 4C  is an end view of the intermeshing rotor shown in  FIG. 3 ;  
         [0030]      FIG. 4D  is a cross-sectional view taken on line  4 D- 4 D of  FIG. 4C ;  
         [0031]      FIG. 4E  is a perspective view of the interior of the intermeshing rotor shown in  FIG. 3 ;  
         [0032]      FIG. 5  is a cross-section view of the intermeshing rotor shown in  FIG. 3  mounted on a rotor shaft;  
         [0033]      FIG. 6  is an end view of the lower housing of the intermeshing kneader shown in  FIG. 1A ;  
         [0034]      FIG. 7  is a perspective view of a pair of intermeshing rotors within the lower housing of the intermeshing kneader shown in  FIG. 1A ;  
         [0035]      FIG. 8  is a front view of the ram of the intermeshing kneader shown in  FIG. 1A ; and  
         [0036]      FIG. 9  is perspective view shown details of a hydraulic locking mechanism for engaging the lower housing shown in  FIG. 6 . 
     
    
     DETAILED DESCRIPTION  
       [0037]     Referring to the figures, a batch type or closed kneader mixer  10  that consists of a mixing chamber  20 , two intermeshing mixing rotors  40  within the mixing chamber  20 , and a movable hydraulically driven ram  24  in the top of the mixing chamber  20  is shown. The hydraulically driven ram  24  moves between an open position, where material can be added to the mixing chamber  20  and a closed position, closing the open upper end  25  of the lower mixing chamber  22  for mixing the added material. The mixing chamber  20  is designed to house the two rotors  40 , which intermesh each other while co-rotating opposite directions. The hydraulic ram  24  applies a controlled pressure on the batch while mixing. The batch is discharged by raising the ram  24  and then rotating the chamber  20  downward up to 180 degrees to a tilted discharge position, as shown in  FIG. 1B .  
         [0038]     One embodiment of the mixer  10  is shown in  FIG. 1A . In this embodiment, the components of the mixer  10  are mounted on a single support base  12 . The mixing chamber  20  includes a lower mixing chamber  22  with an upper housing  26  within which the hydraulically ram  24  is mounted. The intermeshing rotors  40  are mounted on rotor shafts  50  and positioned within the lower mixing chamber  22  (see  FIG. 7 ). The lower mixing chamber  22  is divided into two semi-circular sub-chambers  23 . At each end of the lower mixing chamber  22 , end plates  28  enclose the ends of the lower mixing chamber  22  and hold seals through which the rotor shafts  50  pass. The rotor shafts  50  are supported by bearing supports  29 .  
         [0039]     When ram  24  is in the closed position, the lower part of ram  24  in conjunction with the lower mixing chamber  22  forms the mixing chamber  20 . On the lower surface of ram  24  are two semi-circular surfaces  23   a  that form, along with the lower mixing chamber  22 , the sub-chambers  23 .  
         [0040]     The intermeshing rotors  40  are driven by a motor  30  mounted to support base  12 . The motor  30  is connected to the rotor shafts  50  through a reducer  32  connected to the motor shaft (not shown). The reducer  32  connects to the rotor shafts  50  through a drive coupling  34  connected to drive gears  36 . The drive gears  36  rotate the intermeshing rotors  40  at the same speed in opposite directions.  
         [0041]     The mixing chamber  20  is mounted to support base  12  for tilting to a discharge position (see  FIG. 1B ). A tilting gear  38  drives or tilts the mixing chamber  20  to the discharge position, about 135° from a vertical or upright position.  
         [0042]     The disclosed kneader mixer seeks to achieve single pass mixing through the rotor and hydraulic ram design. With the conventional kneader design, the temperature in a batch can typically not be sufficiently controlled to achieve one-pass mixing. With conventional kneaders the batch temperature after the primary kneading stage is too high because of poor temperature transfer from the mixing contact surfaces to the batch. Therefore the batch has to be either cooled down or transferred to another kneader for the final kneading stage. This additional step is cost prohibitive as well as time consuming.  
         [0043]     Kneader mixer  10  also seeks to impart superior dispersion by reducing filler particle size during the kneading process. The reduction of particle size is achieved by the intermeshing rotor design.  
         [0044]     The kneader mixer  10  uses a two piece rotor design, see  FIG. 5 . An oversized rotor shaft  50  and a cast blade shell portion or hollow cylinder  40 . The cast blade shell or rotor  40  is provided with an internal spiral water passage or spiral groove  46  on an inside surface thereof, which is close to the material contact surfaces. The assembled rotor has a much larger outside diameter than conventional kneaders. This allows for more cooling surface as well as larger mixing surfaces.  
         [0045]     In one embodiment, the kneader mixer  10  has a rotor shaft with one long wing (blade)  42  and two nogs (small blades)  44  for mixing. The rotor has much wider land width  43  and is stubby in shape. The much wider rotor tip (land width)  43  greatly enhances the dispersion effect. The materials are subjected to a larger smearing action of the batch between the wide rotor tip and chamber wall as well as between the rotor tip and the opposite rotor shaft. In the non-intermeshing type kneader, no mixing occurs between the rotor tip and rotor shaft due to the non-intermeshing design. The nogs  44  may have a poly-sided shape.  
         [0046]     The disclosed intermeshing rotor design has less fluid volume capacity than convention kneaders due to the larger rotor outside diameter and intermeshing blades. This is usually not desirable because the batch will be smaller in size. The intermeshing design however compensates for the smaller batch size in much shorter mixing cycles, better batch consistency and 1 pass mixing.  
         [0047]     Kneader mixer  10  imparts superior cooling on the batch that allows rubber curing agents to be added in the primary mixing cycle without having to cool the batch before adding the curing agents to the rubber. In one embodiment, the rotor shaft radius  52  is about 70% of the mixing chamber or sub-chamber radius  27  and the rotor tip width  43  is about 15% to about 30% of the rotor diameter, or the rotor tip width  43  may be 20% to 25% of the rotor diameter. The intermeshing blades or wings  42  have about a 3 to 14 mm rotor tip clearance to opposite rotor shaft, or a clearance of about 3 to 6 mm. The intermeshing rotors  40  should rotate at the same speed to avoid damage to the rotors. The poly-sided mixing rotor nogs  44  should be proximate the ends of the rotor  40  and preferably are pentagon shaped with appropriate angles to maximize material flow. The spiral long blade or wing  42  should start from one rotor end but not span the entire rotor length. The blade  42  should spiral around the rotor  40  and may preferably terminate at least 1″ (25 mm) from the other end of the rotor  40 . This design facilitates proper material flow as well as reducing pressure on the rotor dust seals. This design also increases the fluid volume in the mixing chamber.  
         [0048]     In one embodiment, the spiral cooling groove  46  extends into the wing  42  and nogs  44 . As shown in the figures, the spiral wing  42  extends radially outward from the surface of the rotor  40 . The width  43  of wing  42  is greater than the amount the wing  42  extends outward of the rotor  40 . The wing  42  spirals about 90° around the rotor  40 . In addition, one nog  44  is angularly offset about 90° from the other nog  44 . Also, nog  44  that is at the same end of the rotor  40  from which the wing  42  extends is angularly offset about 90° from that end of the wing  42 .  
         [0049]     Each shaft  50  includes an internal cooling liquid passage  54  that connects with spiral cooling passage  46  to provide cooling liquid to the interior of rotor  40  and to the exterior surfaces of rotor  40  that contact the material being mixed.  
         [0050]     Another embodiment uses a hydraulic ram drive  60  for driving ram  24 . Typical pneumatic rams are uncontrolled and, therefore, the ram position is controlled by the rotor dragging force as well as the size of rubber pieces being forced into the rotors. The hydraulic ram drive  60  exerts positive pressure on the batch and can be accurately controlled in the desirable position, which leads to improved mixing and improved batch to batch consistency. The hydraulic ram drive  60  comprises two hydraulic cylinders or operators  62  with a guide rod  64  in the middle to which the ram  24  is affixed. This arrangement assures that in the event of an oil leak in the hydraulic ram drive  60  the batch will not be contaminated with oil. The hydraulic cylinders  62  are located on a platform  66  on top of the mixer frame and outside the mixing chamber  20  to prevent oil leaking into the mixing chamber.  
         [0051]     A further embodiment includes hydraulic chamber pin locks  70 . Due to the high horsepower requirement to drive the intermeshing rotors  40 , the tilting mixing chamber  20  will tend to rock back and forth due to extreme pressures inside the chamber. Two hydraulic chamber pins  72  extend to lock the mixing chamber  20  in position to prevent chamber movement.  
         [0052]     In one embodiment, a motor  30  is used that provides 3 to 7 horsepower per liter of mixing chamber  20  volume. In one particular embodiment, a motor having 6 HP/L of mixing chamber volume is used. This is much greater horsepower than is typically used for closed kneader mixers. For the 50 L mixing chamber  20  shown in the drawings, the 300 HP motor  30  increases the mixing intensity and can reduce the required mixing time.  
         [0053]     The mixing chamber  20  volume includes the volume enclosed by the lower mixing chamber  22  and the ram  24 , (when the ram  24  is in the closed position, see  FIG. 6 ), and the two chamber end plates  28 .