We introduce a novel line of magnetically coupled mixer drives for biotechnological, pharmaceutical and chemical applications requiring high-grade aseptic conditions. Our solutions enable their application in larger volume bioreactors compared to traditional magnetic drives, due to a possibility of introducing higher power quantities per individual rotor, while ensuring higher mixing intensity. The proposed design has proven itself in a wide variety of mixing applications, by providing high purity, high power, low maintenance and robust mixing even at 20 m3 production scales.
The working principle of our novel magnetic drives is based on transferring mechanical power by means of interaction between two pairs of magnetic rotors, which are placed inside and outside of a hermetic containment housing (1). A stainless steel shaft (2), which is connected via clutch to a gearbox (9) and then to an electrical motor (8), is placed inside the containment housing and equipped with inner rotors (4). The inner rotors (4) are supplied with drive magnets – permanent magnets (PMs), to which the mechanical power from the motor (8) is transferred directly via stainless steel shaft (2). The outer rotors (5), which are equipped with the impeller blades, are placed outside the housing (1) and are supplied with driven magnets (3) – PMs to which the mechanical power is transferred from the drive magnets (4) via magnetic interaction. Two pairs of silicon carbide (6) and zirconium oxide (7) bushings are mounted on both sides of the outer rotor (5) to provide stable rotation and minimize friction. In a fully assembled system by applying a rotation to the drive magnets (4) (the stainless steel shaft (2) respectively), the driven magnets (3) are rotated simultaneously, thus resulting in mixing. The proposed design enables the possibility to provide higher power inputs during mixing compared to conventional magnetic mixers, which utilize electromagnetic drives or bearingless slice motors. The upper mentioned statement can be explained by the possibility of increasing the number of rotors mounted on the mixer, while simultaneously proportionally increasing the summary maximal torque, considering that each mixer rotor in the proposed design has its individual magnetic coupling. Considering, that in the proposed magnetic mixers design, the hermetic containment housing, which is placed in the bioreactor's inner environment, remains stationary it is easier to fully eliminate shaft oscillation, which in turn decreases the potential power loss due to friction. Additionally, taking into account that the hermetic containment housing remains stationary during mixing, it is easier to guarantee impermeability of the bioreactor, as the mixer does not require any type of seals, which in turn enables the possibility to install the mixer either on the top or bottom lid of the vessel. For convenient mixer installation, we provide suitable flanges (10) (for both top and bottom mixer installations), which can be welded on to existing or newly constructed vessels.