Mixing device

Abstract

There is provided a mixing device for low velocity and low shear mixing. The device is of special value for mixing of delicate materials, such as cell suspensions, microspheres and the like, as used in fermentors and the like. The device is based on the suction effect obtained by low velocity rotation of a cylinder provided with tangential openings.

I claim: 
     
       1. A mixing device to be submerged in a liquid contained in a vessel for low velocity and low shear mixing of delicate materials, such as cell suspensions, microspheres and the like, said device comprising: a cylinder open at one end and closed at the other end;   a cylindrical drive member coaxially mounted on said cylinder for rotating the cylinder about the longitudinal axis of said .[.tubular.]. .Iadd.cylindrical drive .Iaddend.member;   at least two vent openings defined by the sidewall of said cylinder located in the same radial plane; and   a vent cover and flow director for each of said vent openings extending peripherally from one side of the vent opening outwardly around the periphery of said cylinder terminating radially spaced from the other side of the vent opening, said vent cover and flow director defining a radially extending liquid opening bounded on one side by the periphery of said cylinder and on all other sides by the terminal edges of said vent cover and flow director for moving said liquid from the interior of the cylinder through said at least two vent openings and its vent cover and flow director, axially along the periphery of said cylinder to said open end of the cylinder by a suction created at said liquid openings when said .[.tubular.]. .Iadd.cylindrical drive .Iaddend.member is rotated at a speed in the range of 10 to 50 RPM.   
     
     
       2. A device according to claim 1, wherein said at least two vent openings and said vent cover and flow director are located at the lower part of the cylinder, said vent cover and flow directors being open towards the same circular direction, rearward the rotation of the cylinder. 
     
     
       3. A device according to claim 1, wherein said vent cover and flow directors, pointing in the same circular direction rearward the rotation of the cylinder, are provided in the upper part of the cylinder. 
     
     
       4. A device according to claim 1, wherein said cylindrical drive member extends above the upper level of the cylinder, and is attached thereto. 
     
     
       5. A device according to claim 1, wherein said cylindrical drive member is axially attached to the center of said cylinder, holes being provided in said cylindrical drive member within the confines of the cylinder, for circulating a gaseous medium through the liquid during a mixing process. .Iadd. 
     
     
       6.  A mixing device to be submerged in a liquid contained in a vessel for low velocity and low shear mixing of delicate materials, such as cell suspensions, microspheres and the like, said device comprising: (a) cylinder means open at one end and closed at the other end to be submerged in a liquid contained in a vessel and to be rotated about its longitudinal axis;   (b) a tubular member coaxially mounted on said cylinder means and projecting into and terminating within said cylinder means for introducing gas into said cylinder means;   (c) at least two inner vent openings defined by the wall of the cylinder means, said inner vent openings being equally spaced about the periphery of the cylinder means and located in a common plane normal to the axis of the cylinder means; and   (d) a vent cover and flow director for each of said inner vent openings extending tangentially from the inner vent opening radially outwardly and peripherally of said cylinder means terminating in an outer vent opening located in an axial plane,   (e) said outer vent openings being equally spaced about the periphery of the cylinder means and lying in said common plane normal to the axis of the cylinder means, said outer vent openings facing in the same direction so that when the cylinder means is rotated at a speed in the range of 10 to 50 RPM with said outer vent openings facing rearwardly, liquid contained in a vessel in which the mixing device is submerged will flow from the interior of the cylinder means through said at least two inner vent openings, their vent covers and flow directors and exit through said outer vent openings tangentially with respect to said cylinder means due to a pressure drop occurring at the outer vent openings caused by the inertia of the liquid, thus creating a suction effect. .Iaddend. .Iadd.7. A mixing device as claimed in claim 6, wherein said vent covers and flow directors include tangentially protruding tubular members. .Iaddend. .Iadd.8. A mixing device as claimed in claim 7, wherein there are two of said tubular members. .Iaddend. .Iadd.9. A mixing device as claimed in claim 6 wherein each outer vent opening is defined between the wall of the cylinder means and the end of the vent cover and flow director. .Iaddend. .Iadd.10. A mixing device as claimed in claim 6 wherein the vent covers and flow directors are located nearer the closed end of the cylinder means. .Iaddend. .Iadd.11. A mixing device as claimed in claim 6 wherein the vent covers and flow directors are located nearer the open end of the cylinder means. .Iaddend. .Iadd.12. A mixing device to be submerged in a liquid contained in a vessel for low velocity and low shear mixing of delicate materials, such as cell suspensions, microspheres and the like, said device comprising:   (a) cylinder means open at one end and closed at the other end to be submerged in a liquid contained in a vessel and to be rotated about its longitudinal axis; and   (b) at least two tangentially extending vent means formed on the wall of the cylinder means, said vent means being equally spaced about the periphery of the cylinder means and located in a common plane normal to the axis of the cylinder means and terminating in vent openings, each vent opening terminated substantially in a plane intersecting the axis of the cylinder means   (c) said vent openings facing in the same direction so that when the cylinder means is rotated at a speed in the range of 10 to 50 RPM with said vent openings facing rearwardly, liquid contained in a vessel in which the mixing device is submerged will flow from the interior of the cylinder means through said vent openings tangentially with respect to said cylinder means due to a pressure drop occurring at the vent openings caused by the inertia of the liquid, thus creating a suction effect. .Iaddend. .Iadd.13. A mixing device as claimed in claim 12, further comprising gas introducing means cooperating with said cylinder means for   
     
     
        introducing gas into said cylinder means. .Iaddend. .Iadd.14.  A mixing device as claimed in claim 12, wherein said vent means include tangentially protruding tubular members. .Iaddend. .Iadd.15. A mixing device as claimed in claim 14, wherein there are two of said tubular members. .Iaddend. .Iadd.16. A mixing device as claimed in claim 12 wherein each vent opening is defined between the wall of the cylinder means and the end of the vent means. .Iaddend. .Iadd.17. A mixing device as claimed in claim 12 wherein the vent means are located nearer the closed end of the cylinder means. .Iaddend. .Iadd.18. A mixing device as claimed in claim 12 wherein the vent means are located nearer the open end 
     
     
        of the cylinder means. .Iaddend. .Iadd.19.  An apparatus for low velocity and low shear mixing of delicate materials, such as cell suspensions, microspheres and the like, said device comprising: (a) vessel for containing a liquid;   (b) cylinder means open at one end and closed at the other end for submersion in a liquid contained in said vessel and to be rotated about its longitudinal axis;   (c) a tubular member coaxially mounted on said cylinder means and projecting into and terminating within said cylinder means for introducing gas into said cylinder means;   (d) at least two inner vent openings defined by the wall of the cylinder means, said inner vent openings being equally spaced about the periphery of the cylinder means and located in a common plane normal to the axis of the cylinder means;   (e) a vent cover and flow director for each of said inner vent openings extending tangentially from the inner vent opening radially outwardly and peripherally of said cylinder means terminating in an outer vent opening located in an axial plane; and   (f) said outer vent openings being equally spaced about the periphery of the cylinder means and lying in said common plane normal to the axis of the cylinder means, said outer vent openings facing in the same direction so that when the cylinder means is rotated at a speed in the range of 10 to 50 RPM with said outer vent openings facing rearwardly, liquid contained in said vessel in which the mixing device is submerged will flow from the interior of the cylinder means through said at least two inner vent openings, their vent covers and flow directors and exit through said outer vent openings tangentially with respect to said cylinder means due to a pressure drop occurring at the outer vent openings caused by the inertia of the liquid, thus creating a suction effect. .Iaddend. .Iadd.20. A mixing device as claimed in claim 19, wherein said vent covers and flow directors include tangentially protruding tubular members. .Iaddend. .Iadd.21. A mixing device as claimed in claim 20, wherein there are two of said tubular members. .Iaddend. .Iadd.22. A mixing device as claimed in claim 19, wherein each outer vent opening is defined between the wall of the cylinder means and the end of the vent cover and flow director. .Iaddend. .Iadd.23. A mixing device as claimed in claim 19, wherein the vent covers and flow directors are located nearer the closed end of the cylinder means. .Iaddend. .Iadd.24. A mixing device as claimed in claim 19, wherein the vent covers and flow directors are located nearer the open   
     
     
        end of the cylinder means. .Iaddend. .Iadd.25.  A mixing device for low velocity and shear mixing of delicate materials, such as cell suspensions, microspheres and the like, said device comprising: (a) a vessel for containing a liquid;   (b) cylinder means open at one end and closed at the other end to be submerged in a liquid contained in said vessel and to be rotated about its longitudinal axis; and   (c) at least two tangentially extending vent means formed on the wall of the cylinder means, said vent means being equally spaced about the periphery of the cylinder means and located in a common plane normal to the axis of the cylinder means and terminating in vent openings, each vent opening terminated substantially in a plane intersecting the axis of the cylinder means,   (d) said vent openings facing in the same direction so that when the cylinder means is rotated at a speed in the range of 10 to 50 RPM with said vent openings facing rearwardly, liquid contained in said vessel in which the mixing device is submerged will flow from the interior of the cylinder means through said vent openings tangentially with respect to said cylinder means due to a pressure drop occurring at the vent openings caused by the inertia of the liquid, thus creating a suction effect.   
     
     
        .Iaddend. .Iadd.26.  A mixing device as claimed in claim 12, further comprising gas introducing means cooperating with said cylinder means for introducing gas into said cylinder means. .Iaddend. .Iadd.27. A mixing device as claimed in claim 12, wherein said vent means include tangentially protruding tubular members. .Iaddend. .Iadd.28. A mixing device as claimed in claim 14, wherein there are two of said tubular members. .Iaddend. .Iadd.29. A mixing device as claimed in claim 12, wherein each vent opening is defined between the wall of the cylinder means and the end of the vent means. .Iaddend. .Iadd.30. A mixing device as claimed in claim 12, wherein the vent means are located nearer the closed end of the cylinder means. .Iaddend. .Iadd.31. A mixing device as claimed in claim 12, wherein the vent means are located nearer the open end of the cylinder means. .Iaddend.