Abstract:
A hub mounting assembly for mounting a plurality of impellers onto a shaft has a first hub ring and a second hub ring. A first key piece is adapted to engage with the shaft and engage with at least one of the hub rings, and a first lock pin is adapted to engage with the shaft and engage with at least one of the hub rings. In the installed state, the first hub ring is adapted to be fastened to the second hub ring, to trap the key piece and lock pin in a position so that the hub rings together form a hub that is locked against rotation and axial movement with respect to the shaft.

Description:
FIELD OF THE INVENTION 
   The invention pertains generally to the field of mixing devices and mixing methods. More particularly, the invention pertains to a method for attaching a hub that supports impellers to a rotating shaft inside the vessel so that the shaft will move the impellers inside the vessel to mix material. 
   BACKGROUND OF THE INVENTION 
   Mixing devices are in wide use in industry, and many mixing devices include a large vessel which contains a liquid or other material to be mixed. In some types, a typically vertically-oriented impeller shaft runs down some or all of the length inside the vessel. The impeller shaft typically enters the vessel through a bearing and seal arrangement, and the impeller shaft is rotatably driven from outside of the vessel usually by a motor located at the top of the vessel. Inside the vessel, at one or several axial locations on the length of the shaft, radially extending impellers are attached to the shaft which have paddles or blade type features extending radially outwardly. Rotation of the shaft rotates the impellers to mix and or otherwise impart energy to the fluid or other material inside the vessel. 
   In some instances, the motor and drive assembly, along with the bearing and sealing arrangement, are mounted at the top opening of the vessel, and the shaft is suspended, so that it hangs down from the motor with its lower end being either a free end spaced above the bottom of the vessel, or a lower stub of the shaft may be rotatably supported by a bearing at the bottom inside of the vessel. In the case of long shafts, intermediate steady bearings may be mounted to provide radial support against flexing or bending or vibration of the shaft. 
   In some instances, the impellers themselves are welded directly onto the shaft at the time of manufacture. This arrangement is often suitable, but also can have the disadvantage that welding of the impellers onto the shaft is relatively permanent. Thus, replacement or substitution of different impellers for different applications is not convenient. Further, the opening in the top of the vessel needs to be large enough to permit a shaft, and the welded impellers all to be inserted through the opening when installing the shaft in the impellers into the vessel. This can require a large opening in the top of the vessel. 
   To overcome these disadvantages, there are arrangements in which a removable or detachable hub that supports the impellers can be mounted onto the shaft. However, at least some of the removable hub designs suffer from the disadvantages that all of the impellers are mounted to a single removable hub, and thus the hub and impeller assembly, which may be quite large, still needs to fit through the opening in the vessel. Further, some of these arrangements have a disadvantage that they may not be as sanitary as the desired. In many applications, it is desirable to have a very sanitary arrangement which reduces as much as possible any of the mixing material from going into the inside structure of the hub mounting arrangement. Entry of the material into the inside structure of the hub mounting arrangement, and into any gaps, crevices or clearances between the hub and the shaft, can be undesirable because it can lead to difficulty in cleaning the installed arrangement and possible contamination of the material being mixed. 
   In view of the foregoing, there is a need in the art for a removably attachable impeller hub that can quickly and easily be attached and/or detached to an impeller shaft, which can provide a secure attachment while also having desirable sanitary properties. 
   SUMMARY OF THE INVENTION 
   Some embodiments of the invention provide for removably attachable impeller hub apparatus that can quickly and easily be attached and/or detached to an impeller shaft, and a hub attachment method which can provide a secure attachment while also having desirable sanitary properties. 
   In one aspect, an embodiment of the invention provides a hub mounting assembly for mounting a plurality of impellers onto a shaft, comprising a first hub ring, a second hub ring, a first key piece adapted to engage with the shaft and engage with at least one of the hub rings; and a first lock pin adapted to engage with the shaft and engage with at least one of the hub rings, wherein the first hub ring is adapted to be fastened to the second hub ring, to trap the key piece and lock pin in a position so that the hub rings together form a hub that is locked against rotation and axial movement with respect to the shaft. 
   In another aspect, an embodiment of the invention provides a hub mounting assembly for mounting a plurality of impellers onto a shaft, comprising a first hub ring a second hub ring a first engaging means adapted to engage with the shaft and engage with at least one of the hub rings and a second engaging means adapted to engage with the shaft and at least one of the hub rings, wherein the first hub ring is adapted to be fastened to the second hub ring, to trap the key piece and lock pin in a position so that the hub rings together form a hub that is locked against rotation and axial movement with respect to the shaft. 
   In yet another aspect, an embodiment of the invention provides a method for attaching a plurality of impellers to a shaft, comprising installing an upper hub ring at a location on the shaft installing a key piece into engagement with the shaft installing a lock pin into engagement with the shaft and fastening a second hub ring to the first hub ring. 
   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 layout/cross-sectional view of a removable impeller hub attachment system and method, according to a preferred embodiment of the present invention and taken through Section  1 - 1  in  FIG. 6 . 
       FIG. 2  is a cross-sectional view taken through Section  2 - 2  in  FIG. 1 , and also corresponds with a view taken through lines  2 - 2  in  FIG. 4 . 
       FIG. 3  is a cross-sectional view taken though Section  3 - 3  in  FIG. 1 . 
       FIG. 4  is a view similar to  FIG. 1 , but showing an alternative embodiment of the present invention. 
       FIG. 5  is a cross-sectional taken through Section  5 - 5  in  FIG. 4 . 
       FIG. 6  is a view of an impeller assembly taken through Section  6 - 6  in  FIG. 1 . 
   

   DETAILED DESCRIPTION 
   Some embodiments of the invention provide a removable attachable impeller hub and method for attachment that can quickly and easily be attached and/or detached to an impeller shaft, which can provide a secure attachment while also having desirable sanitary properties. Preferred embodiments the invention will now be described with reference to the drawing figures in which like reference numerals refer to like parts throughout. 
     FIG. 1  illustrates a preferred embodiment of the invention, in which a mounting assembly generally designated  10  is mounted onto an impeller shaft  12 .  FIG. 1  illustrates only part of an impeller shaft to which the hub  10  is mounted. The illustrated part of impeller shaft  12  has an upper portion  14 , an intermediate portion  16 , and a lower portion  18 . In a typical mixing vessel application, there may be one or more hubs  10  mounted at different lengths of the shaft  12 . Therefore, the reference to upper and lower are for reference with respect to this hub only. Also, although a vertically oriented shaft is shown and described, the shaft in some arrangements can also be horizontally arranged or at any angle. 
   Also, in this illustrated example, the intermediate portion  16  of the shaft  12  is depicted as having a slightly larger diameter than the remainder of the shaft  12 . The intermediate portion  16  may also be different than the rest of the shaft  12  in any of several ways. For example, the intermediate portion  16  may have a different surface finish in order to facilitate interaction with O-rings that are discussed below. Further, making the intermediate portion  16  a larger diameter than the remainder of the shaft  12  may facilitate sliding the hub components  10  over the remainder of the shaft, because there will be a greater clearance between the hubs and the remainder of the shaft, however, there will be a tighter clearance between the hub and the shaft mounting region  16 . Further, the thickened region  16  of the shaft can be manufactured by machining of the entire shaft, or by coating or depositing extra material onto the shaft  12  at the region  16 . 
   The shaft  12  includes a longitudinal key way on slot  22  which is able to receive a longitudinal key piece  24 . The shaft  12  also has a pin hole  26  which is configured to receive a lock pin  28 . 
   The hub assembly  10  includes an upper hub body  30  which has a keyway or slot  32  that also receives part of the key piece  24 . The upper hub  30  has a sloped top surface  34  which is angled downward and away from the shaft  12 . The feature of the angled or conical top surface  34  provides a sanitary benefit in that it reduces beads or puddles of material from resting on this top surface  34  after emptying or cleaning of the vessel. Rather, after emptying or cleaning, any material that would otherwise tend to sit on the top surface  34  of the hub assembly  10 , instead tends to drain off of this angled portion  34 . 
   The upper hub  30  has an O-ring channel  36  located around its top corner, which is sized just smaller than the volume of on elastomeric O-ring  37 . Upon assembly, the elastomeric O-ring  37  is compressed so that it completely fills the channel  36  while bulging outward slightly. This provides a desirable seal, and also reduces the likelihood of material accumulating in the region adjacent the seal after draining or cleaning of the vessel. The upper hub  30  also has a pin receiving notch or groove  35 , which in this embodiment is an angular ring around the lower inner corner of the hub  30 . 
   The upper hub  30  also supports two or more impellers arms  38  which can be attached for example by welding. Those will be discussed in more detail below. Although two arms  38  are illustrated, the hub assembly  10  itself can support any number of impellers arms. Various arrangements for having the arms extend from the hub elements are also useful, and some are described in more detail below. 
   The hub assembly  10  also includes a lower hub body  40 . The lower hub  40  also includes a keyway or slot  42  which receives part of the key piece  24 . The lower hub  40  has an O-ring channel  46  designed around its bottom corner, which is sized just smaller than the volume of a elastomeric O-ring  47 . Upon assembly, the elastomeric O-ring is compressed so that it completely fills the channel  46  while bulging outward slightly. This provides a desirable seal, and also reduces the likelihood of material accumulating in the region adjacent the seal after draining or cleaning of the vessel. The lower hub  40  also has a pin receiving notch or groove  55 , which in this embodiment is an angular ring around the upper inner corner of the hub  40 . 
   The lower hub  40  has a number of preferably spaced mounting bores  48 , through which can be inserted in a threaded fastener  50  such as for example a threaded bolt. The fastener  50  engages with a tapped bore  52  in the upper hub  30 , and has a hex head  54  so that tightening of the threaded bolt  50  secures the lower hub body  40  to the upper hub body  30  in the configuration shown. 
   The threaded bolt  50  in this example has a hexagonal head  54  to facilitate tightening with a wrench, and also has a convex domed end  55 . The domed end  55  facilitates sanitary properties of the device, because after emptying of the vessel or cleaning, any material that tends to drip down along the bottom of the hub assembly  10  will tend to find its lowest point at the domed end  55 . The convex domed downward pointing shape of this domed part  55  of the acorn head tends to cause the materials to be released off the bottom due to surface tension properties of the shape. 
   The upper hub  30  also has an O-ring groove  60  which supports an O-ring  61 . This groove  60  is also sized to be slightly smaller in cross-section than the volume of the O-ring  61  itself, so that it completely fills the groove, and protrudes out slightly, and thus provides a desirable seal, and also reduces the likelihood of material accumulating in the region adjacent the seal after draining or cleaning of the vessel the O-rings described above. 
   A respective O-ring  58  is also seated between the bottom surface of the lower hub body  40  and the surface of each fastener  50  underneath the hexagonal portion  54  as shown, and the ring and groove are designed as described above. In an illustrated embodiment, only two threaded bolts  50  are used. However, in some embodiments three or more equally spaced fasteners  50  may be employed. 
     FIG. 2  shows a cross-section of the key piece  24  sitting in the keyways  22  and  32 . In this example, the key piece  24  is a rectangular straight bar. However, in other embodiments the key piece  24  may be wider and may be curved around the center of curvature at the axis of the shaft. In such a case, the keyways  22  and  33  themselves will also have a curved inner surface. A keyway slot  32  portion is disposed in the upper hub  30  as well as a keyway slot  42  provided in the lower hub  40 . These two slots  32  and  42  together form one elongated slot to receive the key piece  24 . However, providing the slot in both hubs provides positive torque resistance for both hub bodies, and therefore the fasteners  50  do not need to provide the torque resisting support. In some embodiments, it is possible to have only one of the hubs  30  or  40  have the keyway slot as a single feature. Also, one key piece  24  can be used. 
     FIG. 3  shows not only the key piece  24  but also the arrangement of the lock pin  28 . The lock pin  28  fits directly into a pin slot  26  cut into the shaft  12  and extends out to one or both of the hubs  30  and  40 . Whereas the key piece  24  provides a rotational locking function, the pin  28  provides an axial locking function. The lock pin  28  in the embodiment shown, fits within an annular channel that is formed by annular cut-outs on  35  and  45  seen in  FIG. 1 . 
     FIG. 4  shows an alternative embodiment, where instead of a channel being formed by a pair of annular cut-outs  35  and  45 , instead a pin-receiving slot is formed by notches  39  and  49  cut into lower corners of the hub bodies  30  and  40  respectively. The shape of the cut-out formed by notches  39  and  49  in this embodiment can be seen in  FIG. 5 . In some embodiments, not shown, the pin  28  can engage with only one hub body  30  or  40 , and not both as shown in  FIG. 4 . 
     FIG. 6  shows an example of an impeller arrangement with which the hub mounting systems and methods of the present invention may be used. The upper hub  30  supports two impeller blades  60 . The lower hub  40  supports two other impeller blades  62 . A benefit of this arrangement, is that for installation the opening in the vessel needs only be large enough for the two bladed hubs to each individually pass one at a time. In this way a larger impeller can be fit through a smaller opening as compared to a single hub supporting all four of the blades. In this illustrated example, only one upper hub and one lower hub are shown, and each support two blades. Of course, more blades could be attached to each hub. Further, in other embodiments an intermediate hub an be mounted in between the upper hub and the lower hub and this intermediate hub can also support any number of blades. 
   A method of installing the mount  10  for assembly onto a shaft  12  will now be described, particularly with reference to  FIG. 1 . Initially, an end of the shaft  12  is extending free, and none of the mounting assembly components are yet mounted to it. 
   Next, the upper hub body  30  is slid over the end of the shaft, with the O-ring  36  in place in its channel  37 , and the upper hub  30  is moved vertically past its desired position so that the bottom of the upper hub body  30  is past the top of the key way  22 . Next, the key piece  24  is pushed into the key way  22 . Next, the upper hub body  30  is lowered, with its key way slot  32  aligned with the key piece  24  and slid down over a portion of the key piece  24  until it is substantially in its final installed position. However, it is not lowered so far as to obstruct the location of the pin  28  which has not yet been inserted. Next, the pin  28  is inserted and then the hub  30  can be lowered fully. 
   At this point, the key piece  24 , pin  28 , and hub  30  are all located where they will be in the final installed position, with the axial position of the hub  30  being defined by its contact with the pin  28 . 
   Next, the lower hub  40  is slid over the end of the shaft and is brought upward to meet the upper hub  30 . Before sliding the upper hub  40  upwards, the O-rings  60  are installed in place, and during the sliding motion the O-rings  46  remain in place. The keyway  42  is aligned with the key piece  24 . The fasteners  50  are each inserted upwardly through the bores in the lower hub  40  and are tightened into the hub  30  by hand and/or with a wrench to secure the assembly together in the position shown in  FIG. 1 . At this time, each of the O-ring is checked to make sure it is fully seated. The O-rings  58  are slid over the fastener before the fasteners are installed. 
   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 advantanges 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.