the present invention will now be described more fully hereinafter with reference to the accompanying drawings , in which exemplary embodiments of the invention are shown . the invention may , however , be embodied in different forms and should not be construed as limited to the embodiments set forth herein . rather , these embodiments are provided so that this disclosure will be thorough and complete , and will fully convey the scope of the invention to those skilled in the art . like reference , numerals refer to like elements throughout . like elements will , thus , not be described in detail with respect to the description of each figure . fig1 shows an embodiment of an integrated rotary mixer and disperser head 1 . the illustrated mixer and disperser head 1 comprises a drive shaft 2 configured to be connected to a drive motor ( not shown ) via a connecting shaft 3 . the mixer and disperser head 1 comprises a tubular cylindrical mixing chamber 4 preferably made of stainless steel and having a circular cross section and a central axis 5 . the cylindrical mixing chamber 4 is coaxial with and rigidly connected to the drive shaft 2 . spaced equally angularly through the peripheral wall of the mixing chamber 4 in the middle region thereof are provided a plurality of discharge openings . the plurality of discharge openings is embodied as elongated slots 6 . the plurality of elongated slots 6 extends in a direction forming an angle α of 45 degrees with the generally axial direction 5 of the mixing chamber 4 . in other embodiments of the integrated rotary mixer and disperser head according to the invention the plurality of elongated slots may extends in a direction forming an angle α of between 5 degrees and 55 degrees with the generally axial direction 5 of the mixing chamber , preferably an angle α of between 25 degrees and 55 degrees with the generally axial direction of the mixing chamber , even more preferably an angle α of between 35 degrees and 55 degrees with the generally axial direction of the mixing chamber , yet even more preferably an angle α of between 40 degrees and 50 degrees with the generally axial direction of the mixing chamber . connected to the upper planar rim of mixing chamber 4 by weldings such as at 7 is a first set of impeller blades 8 preferably made of stainless steel . the first set of impeller blades 8 are connected to the drive shaft 2 by welding such as at 9 . the first plurality of equally angularly spaced impeller blades 8 are placed at one axial end of the mixing chamber 4 , and each of said first plurality of impeller blades 8 have a leading edge 10 situated completely outside the mixing chamber 4 and disposed axially outside for said one end , and a trailing portion 11 having a trailing edge disposed axially inward for said leading edge 10 . connected to the lower rim of the mixing chamber 4 is a second plurality of equally angularly spaced impeller blades 12 at the other axial end of said mixing chamber 3 . each of said second plurality of impeller blades 12 have a leading edge 13 situated completely outside the mixing chamber 4 and disposed axially outside for said other end , and a trailing portion 14 having a trailing edge disposed axially inward for said leading edge 13 . the leading edge 10 of each of said first plurality of impeller blades 8 forms part of a first shear part , the radially inner end thereof being rigidly connected to said drive shaft 2 , e . g . by welding at 9 and the radially outer end thereof being rigidly connected to said one axial end of the mixing chamber 4 . in the illustrated embodiment each of the first shear parts of the first plurality of impeller blades 8 comprises a leading portion 15 extending in a plane substantially perpendicular to the drive shaft 2 , and a peripheral portion 16 bent about 90 degrees inward from said leading portion 15 . the leading edge 13 of each of said second plurality of impeller blades 12 forms part of a second shear part , the radially inner end thereof being rigidly connected to hub - like central disc ( see fig5 and 7 ), e . g . by welding , and the radially outer end thereof being rigidly connected to said other axial end of the mixing chamber 4 . in the illustrated embodiment each of the second shear parts of the second plurality of impeller blades 12 comprises a leading portion 17 extending in a plane substantially perpendicular to the drive shaft 2 , and a peripheral portion 18 bent about 90 degrees inward from said leading portion 17 . the illustrated embodiment of a mixer and disperser head 1 further comprises a plurality of equally angularly spaced shear arms 19 situated completely outside the mixing chamber 4 and radially extending from said drive shaft 2 . each of the shear arms 19 comprises a leading portion 20 extending in a plane substantially perpendicular to the drive shaft 2 , and a middle portion 21 bent inward from the leading portion 20 , the middle portion thereby forming an obtuse angle relative to said leading portion 20 . each of the shear arms 10 further comprises a peripheral portion 22 bent inward from said middle portion 21 , whereby said peripheral portion 22 forms an obtuse angle relative to said middle portion 21 , such that the peripheral portion 22 is parallel to the peripheral wall of the mixing chamber 4 . the radially inner end of each of said plurality of equally spaced shear arms 19 is rigidly connected to said drive shaft 2 , e . g . by welding , and the radially outer end of each of said plurality of equally spaced shear arms 19 is rigidly connected to a respective one of the radially outer end of one of the first shear part 15 . each of said shear arms 19 has a leading edge 23 and a trailing edge 24 . fig2 shows a cross section of a middle portion 21 of a shear arm 19 , where it is more clearly seen that the leading edge 23 of the middle portion 21 of the shear arm 19 is sharpened , like a scissor . fig3 shows a cross section of an alternative embodiment of a middle portion 21 of a shear arm 19 where it is seen that the leading edge 23 of the middle portion 21 of the shear arm 19 is sharpened like a knife blade . by providing a plurality of equally angularly spaced shear arms 19 situated completely outside the mixing chamber 4 and radially extending from said drive shaft 2 , and connected to the drive shaft 2 and the shear parts as described above , a very robust mixer and disperser head 1 is achieved , wherein the connections between the radially outer end of the first shear parts and the one end of the mixing chamber , e . g . at the welding 7 , is reinforced , thus precluding breakage . moreover , since the leading edge 23 of the shear arms 19 is sharpened as shown in fig2 or 3 , it will during use cut through the material as it is being pulled into the mixing chamber 4 by the first plurality of impeller blades 8 . this cutting action reduces large agglomerates in the material and therefore effectively provides an initial coarse shear zone in addition to the shear zone provided by the mixing chamber 4 with the plurality of discharge openings 6 in its peripheral wall , thereby providing a mixer and disperser head 1 exerting improved hydraulic and mechanical shear to the substances to be mixed or dispersed . this also has the effect that the mixing process takes less time with a mixer and disperser head 1 according to the invention and it is subjected to less stress and wear , and hence gives improved operational energy efficiency . the leading edge 10 , 13 of each of said first and second plurality of impeller blades 8 , 12 is sharpened , for example in the same way as the shear arm 19 is sharpened , preferably as illustrated in fig2 , or alternatively as in fig3 . hereby is provided a second shear zone surrounding the primary shear zone provided by the mixing chamber 4 . the overall effect is the ability to process larger solids , and the ability to produce equal emulsion droplets in less time , thereby allowing a greatly increased capacity and output . fig4 shows a cross section of a mixer and disperser head 1 according to the invention , where it is clearly visible that the trailing portion 11 of each of said first plurality of impeller blades 8 is integral with and forming an obtuse angle β with said leading portion 15 of each of the first impeller blades 8 . this obtuse angle β , which the trailing portion 11 of each of said first plurality of impeller blades 8 forms with said leading portion 15 of each of the first impeller blades 8 is between 105 degrees and 175 degrees , preferably between 125 degrees and 155 degrees . different degrees have been tested in 3d simulation tests and it turns out that an angle β between 125 degrees and 165 degrees provides best results , with a maximal effect at an angle β of approximately 135 degrees , which therefore is the preferred angle β . fig5 shows a perspective view of an embodiment of the second plurality of impeller blades 12 , where it is seen that the trailing portion 14 of each of said second plurality of impeller blades 12 is integral with and forming an obtuse angle with said leading portion 17 of each of said second impeller blades 12 and in a plane projection having the shape of a sector of an annulus . the radially inner end of the leading portions 17 is rigidly connected to hub - like central disc 25 , e . g . by welding , and the radially outer end thereof is configured for being rigidly connected to the other axial end of the mixing chamber 4 . in the illustrated embodiment each of the leading portions 17 extends in a plane substantially perpendicular to the drive shaft 2 , and a have peripheral portion 18 bent about 90 degrees inward from said leading portion 17 . this peripheral portion is rigidly connected to the other axial end of the mixing chamber 4 by , for example , welding . in this embodiment , only three second impeller blades 12 are illustrated ; however , the number of impeller blades will vary and may be chosen in accordance with the particular need . preferably , the obtuse angle β , which the trailing portion 11 of each of said first plurality of impeller blades 8 forms with said leading portion 15 of each of the first impeller blades 8 is equal to the obtuse angle , which the trailing portion 14 of each of said second plurality of impeller blades 12 forms with said leading portion 17 of each of the second impeller blades 12 . as may be seen in fig4 and fig5 , the leading edges 10 and 13 of the first and second set of impeller blades may have sharpened edges which are differently angled , i . e . have different sharpness . however , in a preferred embodiment these sharpened leading edges of the first and second set of impeller blades are identical . furthermore , in another preferred embodiment the sharpened edge 23 of a shear arm 19 may also be equal to the sharpness of the leading edges 10 , 13 of the first and second impeller blades . fig6 shows an embodiment of an integrated rotary mixer and disperser head 1 as seen from above , wherein the rotational direction is illustrated with the arrow r . as illustrated , the trailing edge of the impeller blades 8 is provided with serrations 26 that have a generally castellation - like profile . this castellation - like profile of the serrations 26 will create turbulence or shear in a fluid mixture passing over them . in the illustrated embodiment there is provided a gap 34 between the trailing portions 11 of the first plurality of impeller blades 8 and the cylindrical wall of the mixing chamber 4 . this enables an easier and more accurate cleaning of the disperser and mixer head 1 , especially the inner surface of the cylindrical wall of the mixing chamber 4 . similarly , fig7 shows an embodiment of an integrated rotary mixer and disperser head 1 as seen from below , wherein the rotational direction is illustrated with the arrow r . as illustrated , the trailing edge of the impeller blades 12 is provided with serrations 27 that have a generally castellation - like profile . this castellation - like profile of the serrations 27 will also create turbulence or shear in a fluid mixture passing over them . similarly to what is shown in fig6 there may also be provided a gap 34 between the trailing portions 14 of the second plurality of impeller blades 12 and the cylindrical wall of the mixing chamber 4 . this also enables an easier and more accurate cleaning of the disperser and mixer head 1 , especially the inner surface of the cylindrical wall of the mixing chamber 4 . fig8 shows a cross section of the peripheral wall of the mixing chamber 4 . as illustrated , the trailing edge of each of the plurality of slots 6 through the peripheral wall of the mixing chamber 4 forms an acute angle θ with the tangent to the inside of said wall at the point of intersection . this feature contributes to the shear forces introduced into the fluid mixture expelled through slots 6 . the trailing edges of the slots 6 so formed also enhance the centrifugal pumping action of the mixing chamber 4 by increasing the velocity by which the fluid mixture is expelled from the mixing chamber 4 into the liquid mixture in the surrounding vessel thereby also increasing the hydraulic shear obtained thereby . from the foregoing description of the first and second sets of impeller blades 8 and 12 , respectively , it is to be understood that they may be made from flat sheet metal by punching using the same set of dies , and by bending trailing portions 11 , 14 and bent portions 16 , 18 to one side to obtain a set of impeller blades 8 , 12 and trailing portions 11 , 14 and bent portions 16 , 18 . as shown in fig9 , the drive shaft 2 has a central bore 28 provided with an internal thread 29 adapted to be threadingly engaged with a corresponding external thread on a connecting shaft 3 connected to a drive unit such as an electric motor or a hydraulic or pneumatic motor for rotatably driving the mixer and disperser head 1 . when thus connected to a drive unit the mixer and disperser head 1 is immersed into the substances to be mixed and / or dispersed contained in a suitable vessel and caused to rotate at high rpm . the first and second plurality of impeller blades 8 and 12 , respectively , now act as impeller pumps driving the substances from the surrounding vessel in a mainly axial direction ( along the axis 5 of the mixing chamber 4 ) into the mixing chamber 4 at a great velocity . thereby these substances firstly undergo an abrupt change of relative direction of movement , resulting in the introduction of accelerative shear forces therein , and secondly the flowing substances are further split up by the castellated serrations 26 and 27 , respectively , introducing further turbulence and shear therein . within the mixing chamber 4 , the two streams of substances collide substantially axially at high velocities creating a high hydraulic shear . due to the absence of a high speed rotating shaft within the mixing chamber 4 , there is no rotative force in the center of the mixing chamber 4 acting upon the substances . therefore , the greater part of the substances will move toward the periphery in a mainly non - rotative , radial direction where these substances are expelled through the discharge slots 6 . the high speed rotating slots 6 act upon the slower moving substances with high mechanical shear , and the substances are expelled therefrom with high velocity into the surrounding mixture , whereby they undergo further high hydraulic shear . since the shear arms 19 are provided with sharpened leading edges 23 and each of the first and second plurality of impeller blades 8 and 12 are also provided with sharpened leading edges 10 and 13 , two additional shear zones 32 and 33 are effectively introduced , as compared with the initially mentioned prior art mixer head disclosed in e . g . u . s . patent no . 5 , 407 , 271 . in addition to the primary shear zone 31 provided by the mixing chamber 4 and its slots 6 , the sharpened leading edges 10 and 13 of the first and second plurality of impeller blades 8 and 12 will provide a second shear zone 32 , because these leading edges 10 and 13 will also cut through the substances and provide additional shear to these substances when they enter the mixing chamber 4 . by further providing sharpened leading edges 23 on the shear arms 19 a third , initial shear zone 33 is provided , wherein larger conglomerates and particles may be sheared and broken down , before being sucked into the mixing chamber 4 by the first plurality of impeller blades 8 . this means that shear forces are introduced in the fluid mixtures in at least three further stages , defined by the leading edges 10 and 13 of the first and second plurality of impeller blades and the leading edges 23 of the shear arms , further in the primary stage 31 , which is intensified due to the angle formed by the slots 6 make relative to the generally axial direction of the mixing chamber 4 . the overall effect of this is an improved overall performance of approximately 20 %. since the visibility of the inner surfaces of the mixer and disperser head 1 according to the invention is only slightly obscured by the presence of the two sets of impeller blades 8 and 12 , respectively , the inventive mixer and disperser head lends itself to an ocular inspection after a cip - procedure . from the foregoing description it will be understood that the various parts of the mixer and disperser head according to the invention may be manufactured at a low cost by simple technological processes and interconnected by welding so as to form an integrated one - piece unit . while the foregoing description relates to the preferred embodiment , it will be understood that numerous modifications may be incorporated therein without departing from the inventive concept . thus , the discharge openings may have any other appropriate shape than that of elongated slots 6 , and also the impeller blades 8 and 12 may be present in another number than three for each set of impeller blades 8 , 12 and may have another shape than that described . depending on the intended application of the mixer and disperser head 1 it may also be made from other materials than stainless steel , e . g . from plastics materials , or from a combination of plastics materials and metallic materials , and the various parts of the mixer and disperser head 1 may be rigidly connected to each other by other means than welding , e . g . by adhesive bonding . in the following is given a list of reference numbers that are used in the detailed description of the invention . 1 rotary mixer and disperser head , 2 drive shaft , 3 connecting shaft , 4 mixing chamber , 5 cylindrical axis of the mixing chamber , 6 elongated slots , 7 welding between peripheral portion 16 of the first shear parts , 8 one of the first impeller blades , 9 welding between the leading portion of the first shear part , 10 leading edge of the first impeller blades , 11 trailing portion of the first impeller blades , 12 one of the second plurality of impeller blades , 13 leading edge of the second impeller blades , 14 trailing portion of the second impeller blades , 15 leading portion of the first impeller blades , 16 peripheral portion of the first impeller blades , 17 leading portion of the second impeller blades , 18 peripheral portion of the second impeller blades , 19 shear arms , 20 leading portion of shear arm , 21 middle portion of shear arm , 22 peripheral portion of shear arm , 23 leading edge of shear arm , 24 trailing edge of shear arm , 25 hub - like annular disk connecting the leading portions of the second impeller blades , 26 castellated serrations of the first impeller blades , 27 castellated serrations of the second impeller blades , 28 central bore of the drive shaft , 29 internal thread in the bore of the drive shaft , 31 primary shear zone , 32 secondary shear zone , 33 initial shear zone , and 34 gap between impeller blades and the cylindrical wall of the mixing chamber .