Abstract:
A hub for removable mounting onto a shaft has an inner sleeve having a first end and a second end, and having a substantially cylindrical inner diameter and having an outer surface having a threaded region and a tapered conical surface located substantially near the first end. An outer hub has an inner surface with a threaded region threadably engagable with the threaded region of the inner hub, and a inner tapered conical surface configured to cam along the tapered outer surface of the inner hub. The hub can be locked at a desired axial location or the shaft by engaging the threads to cause the cam surfaces to constrict the diameter of the first end so it frictionally locks onto the shaft.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to the field of hubs that are mounted onto a rotating shaft, for example, hubs that support impellers that are mounted to a rotating mixer shaft. More particularly, the present invention relates to hubs that are removably mounted onto a mixer shaft. 
     BACKGROUND OF THE INVENTION 
     Mixing devices are in wide use in industry, and many mixing devices typically include a vessel, which contains a liquid or other material to be mixed, and an impeller shaft running through some or all of a length inside the vessel. The impeller shaft is typically rotatibly driven by a motor, often located at the top of the vessel. There are radially extending impellers, which are mounted to the shaft at one or several axial locations on the length of the shaft and are in the form of paddles or blade type features that extend radially outward from the shaft. The impellers mix and or otherwise impart energy to the material inside of the vessel when the shaft is rotated. 
     Mixing devices of this type are in wide use, for example in the pharmaceutical, biotechnology, and sanitary food and beverage industries. These industries sometimes present several requirements, which it would be desirable to have met. For example, it is often desirable to be able to change or switch out the shape or size of the impeller being used to permit use of an impeller that will accomplish the desired goals with the material that is to be mixed. For this reason, it would be desirable to have an impeller hub that can be removably mounted on to the shaft, thereby permitting interchanging of different hub impeller arrangements on to a single standard shaft. 
     Another requirement often found in these industries is easy cleanability and maintenance of sanitary conditions before, during and after mixing. Some known disassemblable hub mounting arrangements can present the problem that during operation the material comes in contact with complex surfaces which are then difficult to clean. For example, known hubs may have exposed screws or numerous gaps that can collect dirt or material. Accordingly, it would be desirable to have a removable impeller hub system that maintains sanitary conditions during operation and easy cleanability before or after use. 
     Another desirable characteristic in mixers, in addition to being able to interchange different impeller shapes and sizes, is the ability to change the axial location of the impeller hub. Therefore, it would also be desirable to have a removable impeller assembly that provides for axial adjustment if desired. 
     It would further be desirable to have such an impeller and hub assembly that is economical, requires a relatively few number of parts, and that can be simple to install and uninstall. 
     SUMMARY OF THE INVENTION 
     The foregoing needs are met, to a great extent, by the present invention, wherein in one aspect of an apparatus and method is provided that in some embodiments can be easily mounted onto a shaft at the desired axial location, and adjusted to a different axial location and/or removed entirely when desired, and which is easy to clean. 
     In accordance with one aspect of the present invention, a hub assembly for removable mounting onto a shaft comprises an inner sleeve having a first end and a second end, and having a substantially cylindrical inner diameter and having an outer surface having an outward-facing threaded region, and an outward-facing tapered conical surface located substantially near the first end; and an outer hub having an inner surface with an inward-facing threaded region threadably engagable with the outward-facing threaded region of the inner hub, and an inward-facing tapered conical surface configured to cam along the outward-facing tapered conical surface of the inner hub. 
     In accordance with another aspect of the present invention, a hub assembly for removable mounting onto a shaft comprises an inner sleeve having a first end and a second end, and having a substantially cylindrical inner diameter and having an outer surface having an outward-facing threaded region, and an outward-facing tapered conical region located substantially near the first end; an outer hub having an inner surface with an inward-facing threaded region threadably engagable with the outward-facing threaded region of the inner hub, and an inward-facing tapered conical surface configured to cam along the outward-facing tapered conical surface of the inner hub; and means for constricting the inner diameter at the first end of the inner hub, by relative rotation of the inner hub with respect to the outer hub. 
     In accordance with yet another aspect of the present invention, aspect of the present invention, a method for removably mounting a hub assembly onto a shaft, comprises: providing an inner sleeve having a first end and a second end, and having a substantially cylindrical inner diameter and having an outer surface having an outward-facing threaded region, and an outward-facing tapered conical region located substantially near the first end; providing an outer hub having an inner surface with an inward-facing threaded region threadably engagable with the outward-facing threaded region of the inner hub, and an inward-facing tapered conical surface configured to cam along the outward-facing tapered conical surface of the inner hub; and constricting the inner diameter at the first end of the inner hub, upon relative rotation of the inner hub with respect to the outer hub to cause the tapered surface of the inner hub to cam along the tapered surface of the outer hub. 
     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 side view illustrating an impeller and hub assembly mounted onto a rotating shaft. 
         FIG. 2  is a top view of the impeller and hub assembly of  FIG. 1 . 
         FIG. 3  is a cross-sectional view taken through line  3 - 3  in  FIG. 2  and with the shaft and the blade omitted. 
         FIG. 4  is an end view of an inner hub sleeve. 
         FIG. 5  is a cross-sectional view taken though line  5 - 5  in  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION 
     The foregoing needs are met, to a great extent, by the present invention, wherein in one aspect an apparatus and method is provided that in some embodiments can be easily mounted onto a shaft at the desired axial location, and adjusted to a different axial location and/or removed entirely when desired, and which is easy to clean. 
     Some preferred embodiments of the invention will now be described with reference to the drawing figures, in which like reference numerals refer to like parts throughout. Turning to  FIG. 1 , a side view of an impeller hub and blade assembly  10  mounted on to a shaft  12  is depicted. 
       FIG. 2  is a top view of the impeller hub and blade assembly  10  of  FIG. 1  showing the impeller hub and blade assembly  10  being mounted on the shaft  12  and having an outer impeller hub  14  from which radially extend three impeller blades  16 . The impeller blades  16  shown are exemplary and it is to be understood that any of a wide variety of impeller blades lengths and shapes can be used, as well as any other number of blade elements themselves. 
     One of the advantages of the arrangement shown in  FIGS. 1-3  is that the removal of the outer impeller hub  14  and the impeller blades  16  can be easily accomplished. For example, returning to  FIG. 1 , the shaft  12  is shown having an upper portion with a somewhat larger diameter then the lower portion of the shaft. A step change in diameter is occurring here, where a two piece shaft is illustrated. The step change in diameter is located where the two pieces of the shaft are mounted to each other. The lower most end of the shaft  12  (not shown) is typically freely extending into the material to be mixed, or may be retained by some form of steady bearing or stub shaft bearing at the base of the vessel. Accordingly, when the shaft  12  is removed from the vessel, the hub and blade assembly  10  can be slid over the end and onto the shaft in order to facilitate mounting it onto the shaft  12 . Once slid over the end, the impeller hub and blade assembly  10  can be slid along the length of the shaft  12  to its desired axial location, and then fastened at that axial location. Conversely, the hub and impeller assembly  10  can be removed from the shaft  12  by sliding it off the free end. 
     Turning now to  FIG. 3 , a cross-sectional view taken through line  3 - 3  of  FIG. 2  is illustrated. For simplicity, the impeller blades  16  and the shaft  12  are omitted from  FIG. 3 .  FIG. 3  shows the hub and impeller assembly  10  having two major components. The first major component is an outer impeller hub  14 , which has a generally cylindrical hollow body as shown. The impeller blades  16  extend radially from the outer impeller hub  14 , and in some of the embodiments be welded directly to the outer impeller hub  14 . Of course they also may be permanently or removably attached by other methods. 
     The other major component is the inner impeller hub sleeve  18 . The inner impeller hub sleeve  18  has an externally threaded region  20 , which has threads sized to mate with an internally facing threaded region  22  of the outer impeller hub  14 . It will be appreciated that by this arrangement, the inner impeller hub sleeve  18  can be rotated with respect to the outer impeller hub  14 , or vise versa, so that the threaded connection will move the inner impeller hub sleeve  18  longitudinally with respect to the outer impeller hub  14 . For example, rotating the inner impeller hub sleeve  18  in a first direction causes the inner impeller sleeve  18  to translate in the direction shown in the arrow A with respect to the outer impeller hub  14 . 
     The inner impeller hub sleeve  18  has a conical or tapered outer face portion  24  which has a conical taper angle that matches an inward conical or tapered inner face  26  of the outer impeller hub  14 . The outer face portion  24  and inner face portion  26  have a sliding, camming relationship. 
     Rotation of the outer impeller hub  14  with respect to the inner impeller hub sleeve  18  that longitudinally translates the inner hub sleeve  18  in direction with respect to the outer impeller hub  14  will cause some inward deflection of the top end  30  of the inner impeller hub sleeve  18  due to camming sliding contact between the outer face portion  24  and inner face portion  26 . That is, the top end  30  of the inner impeller sleeve will have its diameter constricted or reduced to some degree. 
     The inner impeller hub sleeve  18  has an inner diameter  32 , which is sized to be very slightly larger than the outer diameter of the drive shaft  12 . The outer impeller hub  28  also has an inner diameter  34  that is also selected to be larger than the shaft diameter. Therefore, it will be appreciated that the components  14  and  18  can be slid over the end of the shaft (whether together with the threads mated or individually as separate components one at a time), and can be slid upward along the length of the shaft, or to the desired axial location. In the embodiment shown in  FIG. 1 , the shaft  12  has a step provided by the change in shaft direction as described above, so vertical travel during installation is limited by this step. However, the impeller and hub assembly  10  can actually be mounted anywhere along the length of the shaft between the end of the shaft  12  and the step. 
     Once the impeller and hub assembly  10  is at the desired axial location, it can be locked onto the shaft  12  by rotating the hub  14  and the hub sleeve  18  with respect to each other, to affect the constriction of the inner diameter  30  as has been described above via the threaded portions and the camed faces. In the illustrated preferred embodiment, this tightening can be accomplished by hand. The constriction of the end  30  will cause frictional contact with the shaft  12  that is sufficient to lock the hub assembly  10  so that it rotates together with the shaft  12 . The direction of the threads can be selected so that the torque imparted by the shaft  12  and the resistance of the blades  16  is continually providing a tightening force that further serves to tighten the threads and maintain the frictional fit via the constriction of the end  30 . 
     In order to provide for sanitary conditions during operation, three O-ring seals  40 ,  42  and  44  are provided, each resting within a properly sized O-ring support channel. These three seals  40 ,  42  and  44  together prevent the material being mixed from entering into threaded areas  20  and  22  as well as the tapered conical areas  26  and  28 . They also substantially prevent material from getting in between the hub components  14  and  16  and the shaft  12  itself. The O-rings  40 ,  42  and  44  can for example be any suitable type of electrometric sealer ring, and for example can be rings made of kalrez (available from Dupont) or peroxide cured EPDM. 
     The O-rings  40 ,  42  and  44  are provided for sealing, and not required to provide any substantial locking function. That is, the hub and impeller assembly  10  can be slid up or down the length of the shaft  12  against the frictional resistance, if any, provided by the O-rings  40  and  44 . Further, the outer hub  14  and inner hub sleeve  18  can be spun relative to each other relatively easily to overcome the frictional force provided by the O-ring  42 . 
     Also shown in  FIG. 3  is a cross-cut slot  50  which is provided on the inner surface  32  of the inner impeller hub sleeve  18 .  FIGS. 4 and 5  showing further detail that cross-cut slots  50 ,  52 ,  54  and  56  are provided near the end  30  of the inner impeller hub sleeve  18  as shown. The provision of these slots facilitates the inward compression of the top end  30  and the resulting constriction of the diameter of the inner surface  32 . Thus, the conical tapered end  30  is able to deform and frictionally grab onto the shaft  12 . The provision of the cross-cut slot  50  also allows this deformation to occur within an elastic region, so that the constriction in release at the end occurs in a spring like fashion. Of course, depending on the size and geometry involved, more or less cross-cuts may be provided as appropriate. 
     It will be appreciated that the illustrated preferred embodiment provides a significant advantage in that it has only two major components and three O-rings. The embodiment does not necessarily require any additional screws, fasteners, c-rings, snap rings or other locking fasteners. This make this preferred embodiment not only economical to manufacturer and simple to use, but also easy to clean, since only two major components and three O-rings need to be cleaned. Also, since the material being mixed during operation is fully or at least substantially prevented from any ingress into the threaded areas  20  and  22  by the O-rings  40  and  44 , cleaning of these surfaces is made easier. Further, the preferred embodiment illustrates an example where no keys or threads are substantially exposed to the material, and no external bolt hole or fastener holes are presented to the material. 
     The impeller and hub assembly  10  may be made of any suitable material including for example metals or plastics. In the case of pharmaceutical, biotechnology, or sanitary food and beverage industries, one preferred material is stainless steel. 
     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 maybe resorted to, falling within the scope of the invention.