Abstract:
An improved method and apparatus for mixing is provided that features a drive system that is removable from a bearing housing that supports the impeller shaft in the vessel. Some versions of the system and method use a magnetic drive system having a canister projecting outward from the bearing housing. The drive system has a lower shell that engages with the bearing housing and is quickly releasable and/or detachable to facilitate mounting and dismounting of the drive system from the bearing assembly.

Description:
FIELD OF THE INVENTION 
     The present invention pertains generally to mixing devices and mixing methods, and more particularly pertains to mixing devices and methods that utilize a driven impeller shaft that extends into a mixing vessel to mix material therein. 
     BACKGROUND OF THE INVENTION 
     Mixing devices and assemblies are in wide use in industry, for example, in the food processing, pharmaceutical, biotechnology, chemical, consumer product manufacturing, and other industries. In these industries, it is often desirable to contain a material to be mixed or agitated such as, for example, a liquid, a slurry, or any other material in a vessel and to impart mixing or agitating energy to the material via a shaft that is driven to rotate and has axially extending impellers that impart force to the material. The impellers often take the form of flat or curved blades. 
     One recently developed type of such mixer, which is sometimes especially suitable for industries requiring very high sanitary or cleanliness or cleanability conditions, is a so-called magnetically driven mixer arrangement. 
     In one type of a magnetically driven mixer arrangement, the material to be mixed or agitated is sealed inside a vessel and a bearing housing which supports the impeller shaft is provided adjacent an opening of the vessel. The end of the impeller shaft housing is closed with a domed-shape canister. Inside the canister, the end of the impeller shaft has an inner magnetic rotor, which is typically a rotor or a shaft stub having magnets disposed thereon. 
     External to the canister, a drive system is provided which has a hollowed out outer magnetic rotor which fits around and over the canister, and also has magnets disposed thereon. The outer magnetic rotor is driven by a motor and gear box with an associated shaft, all external to the canister and to the mixing vessel. Typically, the inner rotor magnets face outwardly towards the canister. Also, typically the outer rotor magnets face inwardly towards the canister. Rotation of the outer magnetic rotor creates a rotating magnetic field that tends to rotate the inner magnetic rotor, thus driving the impeller shaft. 
     In many magnetically driven mixer systems, it has been a prior practice to semi-permanently affix the drive system to the bearing housing by utilizing radially extending flanges having holes in the flanges combined with bolts through the holes of the associated flanges. 
     This type of arrangement uses radial flanges and axial bolts and provides good alignment and durability. However, this arrangement also has the disadvantage that it is relatively cumbersome and time consuming to undo all of the bolts in order to remove the motor and drive assembly from the bearing housing. This is especially true since a relatively large number of bolts can be involved. Of course reinstalling the drive system to a vessel also requires a cumbersome and time consuming operation of a fairly large number of bolts. 
     In the case of most known prior art systems, this has not posed a significant disadvantage, because the only removal of the motor and drive system that occurs would occur during some kind of cleaning or servicing of the bearing housing which does not occur particularly frequently. Also, since the bearing housing is detachable from the opening in the vessel, it has been a suitable practice to detach the bearing housing and motor drive assembly as one single unit. 
     However, in some instances it would be desirable to have a more readily detachable and re-attachable drive system. Accordingly, there is a need in the art for a mixing impeller drive system and method that provides a convenient, economical and rapid installation and removal of the drive system from the remainder of the mixer assembly. 
     SUMMARY OF THE INVENTION 
     The foregoing needs are met, to a great extent, by the present invention, wherein in one aspect an apparatus is provided that in some embodiments provides an improved drive system mounting assembly and method for a mixing device, including in some embodiments a bayonet type mount. 
     In accordance with one embodiment of the present invention, a mixer drive apparatus having a bearing housing that rotationally supports an impeller shaft; an outer cylindrical surface defined by the bearing housing having a first engaging feature thereon; a removable drive system, having a cylindrical lower shell sized to fit over a portion of the bearing housing; and a second engaging feature on the lower shell that releasably fastens the lower shell to the bearing housing by engaging the first engaging feature. 
     In accordance with another embodiment of the present invention, a mixer drive apparatus having a bearing housing that rotationally supports an impeller shaft; an outer cylindrical surface defined by the bearing housing having a first engaging means therein; a removable driving means for driving the impeller shaft having a cylindrical lower shell sized to fit over a portion of the bearing housing; and a second engaging means on the lower shell for fastening lower shell to the bearing housing. 
     In accordance with yet another embodiment of the present invention, a method for mixing material in a vessel having an impeller shaft, the method includes rotationally supporting an impeller shaft with a bearing housing; engaging an outer cylindrical surface defined by the bearing housing having a first engaging feature thereon with a removable drive system, having a cylindrical lower shell sized to fit over a portion of the bearing housing and a second engaging feature on the lower shell that releasably fastens the lower shell to the bearing housing by engaging the first engaging feature by engaging the first and second engaging features with each other. 
     There has thus been outlined, rather broadly, certain embodiments of the invention in order that the detailed description thereof herein may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional embodiments of the invention that will be described below and which will form the subject matter of the claims appended hereto. 
     In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of embodiments in addition to those described and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting. 
     As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a drive assembly, bearing housing, and impeller shaft according to a preferred embodiment of the present invention. 
         FIG. 2  is an exploded view of the assembly of  FIG. 1 . 
         FIG. 3  is a top view of the assembly of  FIG. 1 . 
         FIG. 4  is a cross-sectional view taken through line  4 - 4  of  FIG. 3 . 
         FIG. 4A  is a detail cross-section view taken through line  4 A- 4 A of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION 
     Some embodiments of the present invention provide a mixing impeller drive system and method that provides a convenient, economical and rapid installation and removal of the drive system from the remainder of the mixer assembly. In one example embodiment, a bayonet type mounting arrangement is provided. Preferred embodiments will now be described with reference to the drawing figures, in which like reference numerals refer to like parts throughout. 
       FIGS. 1 through 4  illustrate a preferred embodiment of the present invention, in which a drive system for a magnetically driven mixer impeller is provided with a quick and convenient detachment with respect to a bearing housing. More specifically, a drive system  10  is shown which includes a motor and gear drive housing including an upper cylindrical shell portion  12  and a lower cylindrical shell portion  14 . The upper and lower shell portions  12  and  14  may be two pieces secured by one or more connecting screws  16  or may be a single shell. The upper shell portion  12  surrounds a motor assembly (not shown) and may have a panel  18  for a controller. 
     The lower end  20  of the lower shell portion  14  extends downwardly as shown. The inner diameter surface of the lower shell portion  14  has an inner diameter sized to fit over a diameter of a cylindrical side surface  22  of the bearing housing  24 . The bearing housing  24  supports an impeller shaft  26  as shown. The bearing housing  24  also has a lower end  28  that is sized to be mounted to an opening of a mixing vessel (not shown) in  FIGS. 1 and 2 . The bearing housing  24  also has an upwardly (away from the vessel) protruding canister  30  which is mounted to the bearing housing by a series axially directed screws  32 . 
       FIG. 2  shows the assembly in the disassembled state. To assemble the device into the operative configuration shown in  FIG. 1 , the lower shell portion  14  is lowered over the surface  22  with the vertical part of an L-shaped slot  34  aligned with the threaded shaft of a wing screw  36 . The wing screw  36  is screwed into a threaded hole in the surface  22  of the bearing housing  24 . The vertical slot portion of the L-shaped slot  34  is slightly wider than the threaded portion of the wing screw  36  so that the lower shell portion  14  can slide down and over the surface  22  until the bottom end surface  20  will bottom out against a shoulder  38  on the bearing housing  24 . Next, the lower shell portion  14  is rotated clockwise so that the threaded shaft of the wing screw  36  slides along the horizontal portion of the L-shaped slot  34 , thus, positively locating the bottom end  20  against the shoulder  38 . 
     The horizontal portion of the L-shaped slot  34  may be slightly angled or tapered so that it tends to cam against the threaded surface of the wing screw  36 , forcing the lower shell portion  14  downward and further contributing to the bottom end  20  bottoming out on the shoulder  38 . Once the lower end  20  is fully bottomed out on the shoulder  38 , the wing screw  36  is tightened, thereby securing the entire assembly in place. 
     In the preferred embodiment illustrated, two opposed wing screws  36  are provided, but any other number may be used. Typically to or more wing screws  36  will be provided, but, for example, if close alignment is not required, or if other alignment features are used, some embodiments may have solely one wing screw. 
     Also, although a wing screw is illustrated, it will be appreciated that any other type of tightenable fastener, such as, for example, an allen head screw, Philips head screw, a machine head screw, or other like fasteners can be used to engage the L-shaped slot  34  and also to tighten against it. Also, in some embodiments, instead of a removable screw, a fixed radially protruding post may be provided which interacts with the L-shaped slot  34 . Further, although an L-shaped slot is depicted having a generally vertical axial leg portion meeting at substantially right angles with a generally horizontal portion (which might be slightly tapered or tilted to provide a tightening effect) it will be appreciated that other shapes of keyways can be utilized in place of the L-shaped slot  34 , and in particular, may be shaped and designed to operatively correspond with the fixed post or removable fastener  36  being used. 
     Also a combination of one or more screws or posts may be used. Also, the slots and screws/posts can be reversed so the slots are on the surface  22  and the screws/posts extend inward from the lower shell portion  14 . Besides slots and screws/posts, any other interlocking mechanical connection can be employed, including threads or mating keyways. Generally, all of these mechanical attachments include various bayonet mounts. 
       FIG. 4  is an exploded view, which shows further details, particularly of the magnetic connection. In addition to the elements described above,  FIG. 4  also depicts an outer magnetic rotor  50  which has magnets disposed on its inward surface, and the inner magnetic rotor  52  which has magnets disposed around its outer surface. The inner magnetic rotor  52  is shown mounted to an impeller shaft  56  which is supported by a pair of roller bearings  58 . In some preferred embodiments, these roller bearings  58  may be of an all-ceramic design, or can be a metal or metal ceramic design. 
       FIG. 4  also illustrates a vessel  60  to which the bearing housing  24  is mounted. The connection of the bearing housing  24  to the vessel  60  in this figure is schematic only and may be accomplished by any suitable known attachment method. In addition, the illustrated embodiment shows the bearing housing  24  including a pedestal  62  by which it is mounted to the vessel  60  and also having a upper pedestal  64  which is mounted to the bearing housing  24  in supports the canister dome  30 . This type of bearing housing is illustrated by way of example only. 
       FIG. 4A  shows the interaction of the wing screws  36  projecting into threaded bores in the bearing housing  24 . 
     Some embodiments according to the present invention can be utilized wherever it is desirable to have a quick release drive system for a mixer including, for example, magnetically driven mixers. They may also be usable in other applications other than magnetic mixers, for example, where instead of a magnetic canister and inner and outer magnetic rotors, a simple splined or other axial end-to-end shaft connection may be implemented. 
     However, one particularly advantageous use of the above-described embodiment is in the context of sanitary and/or clean-in-place magnetically driven mixers. In some embodiments, sanitary and/or clean-in-place magnetically driven mixers may be completely sealed and may even be disposable. Such mixers may be completely sealed at the time of manufacture, and once filled and used for a mixing cycle and then emptied, some sealed magnetic mixers vessels may be disposable. 
     In these systems, a particularly advantageous manufacturing process can be implemented wherein a manufacturing facility may utilize one or a limited number of drive systems which is less than a number of vessels that are used in the manufacturing facility. That is, the drive systems can be quickly changed from one vessel to another. 
     Also, in the case of disposable vessels, or vessels that are taken off site for cleaning or refurbishment, a useful arrangement can be obtained where (1) the vessels are delivered without a drive system, (2) a drive system which is already at the facility is quickly mounted onto the vessel, (3) the mixing cycle is performed, and then (4) the drive system can be quickly removed. In another embodiment of the invention, standard sizes of canisters and bearing housing can be developed over a range of different standard sizes, and corresponding standard size lower shells  14  can also be designed, so that a system is provided having a number of different user selectable corresponding standard sizes. 
     In the illustrated embodiment, the lower end  20  of the lower shell portion  14  provides a positive bottoming out stop facing against the shoulder  38 . This provides an advantage of these embodiments, wherein a positive axial placement as well as axial alignment is provided by the interface of these two surfaces. This facilitates alignment of the inner and outer magnetic rotors and proper drive operation. However, in other embodiments, other alignment contact surfaces may be provided and besides being a flat bottom end  20 . 
     The many features and advantages of the invention are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirit and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.