Abstract:
A dead shaft or motorized conveyor pulley in which a drum is mounted for rotation about an axis of rotation on a shaft mounted against rotation, has the shaft mounted in a pivot sphere. The sphere is mounted in a complementarily socketed block against rotation around the axis of rotation but to permit angular movement in response to misalignment of the shaft from one of the drum to the other end during installation.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This is a continuation in part of our application Ser. No. 09/187,893, filed Nov. 6, 1998. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002] Not Applicable. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0003]    The invention of this application is described as applied to motorized conveyor pulleys, but it has application to dead shaft pulleys (those in which the shaft of a pulley is fixed against rotation, the drum of the pulley being mounted on bearings to rotate about the shaft) generally as well. Motorized conveyor pulleys have an electric motor inside a drum of the pulley, and a shaft with extensions at each end, fixed against rotation in mounting blocks mounted on a conveyer frame. Conveyer frames are welded structures that inherently do not have the positional accuracy required to mount machine components. Machining the frame structure to create a proper alignment is expensive and many conveyor structures are too large to be machined. In a motorized conveyor pulley a rigid mounting of the pulley in misalignment will cause excessive stress and lead to early failure of either the pulley or the frame. Thus, there must be some provision for aligning the shaft extensions and mounting blocks when the pulley is installed.  
           [0004]    Conventionally, the shaft extensions of a motorized conveyor pulley are loosely fitted in mounting blocks in the form of yokes to allow for misalignment. Such a loose fit is noisy and leads to wear due to relative motion and impact loading. This is likely to cause early failure. For food and beverage service, the gap between the shaft and the mounting block can trap food.  
           [0005]    One of the objects of this invention is to provide a mounting structure for a motorized conveyor pulley that accommodates misalignment but at the same time minimizes noise and relative motion, and provides a more sanitary arrangement for food and beverage service installations.  
           [0006]    Other objects will become apparent to those skilled in the art in the light of the following description and accompanying drawings.  
         BRIEF SUMMARY OF THE INVENTION  
         [0007]    In accordance with this invention, generally stated, a mounting for a dead shaft or motorized conveyor pulley is provided in which the shaft of the pulley is mounted at least one end in a pivot sphere, the sphere being mounted in a complementarily socketed block against rotation around the axis of rotation of the shaft when pulley is in use, but to permit angular movement in response to misalignment of the shaft from one end of the drum to another end during its installation. In a motorized pulley, the shaft is a composite, with shaft extensions extending from both ends of a pulley drum. Inasmuch as the extensions are part of the shaft as a whole, they are encompassed within the term “shaft” as used herein, when referring to the shaft&#39;s projecting from the drum. Preferably, each of the shaft extensions is mounted in a sphere against rotation. In both the dead shaft and motorized pulleys, the sphere is held against rotation around the axis of the shaft by clamping of the mounting block around the sphere. A positive restraint as a back-up can be provided in the form of a pin extending from the mounting block into a slot in the exterior of the sphere parallel to the axis of rotation of the pulley. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0008]    In the drawings, FIG. 1 is a view in side elevation of a motorized conveyor pulley mounted in accordance with one illustrative embodiment of this invention. Shaft extensions  5  and  6  are shown as exaggeratedly misaligned in a vertical plane, to illustrate the capability of the mounting assembly in this invention;  
         [0009]    [0009]FIG. 2 is a sectional view of a prior art mounting block and shaft;  
         [0010]    [0010]FIG. 3 is a fragmentary sectional view of the shaft, sphere and mounting block shown on the right end of the pulley of FIG. 1;  
         [0011]    [0011]FIG. 4 is a view in perspective of the mounting block and sphere and a shaft extension of this embodiment of the invention, with a threaded holding pin omitted;  
         [0012]    [0012]FIG. 5 is a view in end elevation of the block shown in FIG. 4; and  
         [0013]    [0013]FIG. 6 is a view in end elevation of the block shown in FIG. 2, being part of the prior art.  
         [0014]    Corresponding reference numerals will be used throughout the several figures of the drawings. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0015]    Referring now to the drawings for one illustrative embodiment of this invention, reference numeral  1  indicates a motorized conveyor pulley, which can be conventional as described in an application, now U.S. Pat. No. 6,117,318, co-pending with the parent of the present application Ser. No. 09/187,893, assigned to a common assignee. The pulley  1  is bolted to a support structure  2 , shown only fragmentarily, by means of bolts, as indicated at  16  in FIG. 6, the use of such bolts being conventional. The pulley includes a drum  3  and two shaft extensions,  5  and  6 , cylindrical through their central section, but provided at their projecting ends with flats  7 .  
         [0016]    [0016]FIGS. 2 and 6 illustrate a conventional mounting, in which a shaft is loosely confined in a yoke  9 , within a slot defined by side walls  10  and a bottom wall  11 , which permits vertical misalignment, and a limited amount of horizontal angular misalignment, but suffers from the disadvantages described heretofore.  
         [0017]    In the present invention, the shaft extensions  5  and  6  are mounted against rotation in spheres  20 . In the embodiment shown, the spheres  20  are made in the form of two hemispheres, a lower hemisphere  21  and an upper hemisphere or bearing cap  22 . The upper hemisphere  22  has, in this embodiment, an axial slot  23  in its uppermost surface, defined by parallel side walls and a bottom wall, as shown in FIG. 3. Each of the shafts  5  and  6  is mounted to fit closely in a seat defined by a flat bottom  24  and arcuate side walls  25  in the lower hemisphere and a flat upper wall  27  and arcuate side walls  28  in the upper hemisphere. The close fit substantially eliminates the noise and wear permitted by the conventional yoke. The spheres are mounted in mounting blocks  30 , and seated in sockets  32  formed in the mounting blocks  30 . The mounting blocks  30  are made in two parts, a lower seat part  34  and an upper seat part or bearing cap  46 . The lower seat part  34  has a base  35  from which ears  36  extend. Ears  36  have bolt holes  37  through them by which the mounting blocks are mounted on the support structure. The base  35  has bolt bosses  40 , from which bolts  42 , parallel to one another, project toward the upper seat part. The seats of the socket  32  are in the form of a semicircular groove or channel  44  in the lower seat part and  50  in the upper seat part  46 . The grooves  44  and  50  are aligned, to form an annular seat when the parts  34  and  46  are mounted, interrupted only by a narrow gap  60  between the seat parts  34  and  46  when the sphere is installed. The upper seat part  46  has bolt bosses  48  through which the bolts  42  extend, the bolts projecting from an upper surface of the bolt bosses sufficiently far to receive nuts  59 . The provision of the gap  60  permits the sphere to be gripped tightly between the seat parts to prevent rotation of the sphere when the nuts  59  on the bolts  42  are torqued down.  
         [0018]    An internally threaded bolt hole  52 , extending radially through the upper seat  46 , is aligned with the slot  23 . A threaded pin  54 , mounted in the bolt hole  52 , extends into the slot  23 , closely adjacent but clear of the bottom wall of the slot, so as to permit angular movement of the shafts in a vertical plane, and is provided with sufficient clearance between the side walls of the slot  23  to permit angular movement of the sphere  20  about the pin  54  as a pivot in a horizontal plane. Thus the axis of rotation of the drum has freedom to pitch and yaw, but not to translate or roll.  
         [0019]    As has been indicated, tightening the nuts  59  on the bolts  42  clamps the sphere between the upper and lower seat members  34  and  46 . In the embodiment described, if the clamping pressure should be unintentionally relaxed enough to permit rotation of the sphere, the sphere will be prevented from rotating around the axis of the shaft by the pin  54 , but it is intended that the clamping pressure be sufficient to prevent rotation after the pulley has been installed and the nuts  59  torqued down. The width of the gap  60  and the amount of torque applied to the nuts  59  will vary with the size of the pulley, hence the size of the spheres and mounting blocks.  
         [0020]    In installing the pulley, the lower part of each mounting block is loosely mounted on a rail of a supporting structure, the spheres, in which the shaft extensions  5  and  6  are mounted, are seated in the lower part of the mounting block, and the upper part of the mounting block is put in place over the spheres, with the bolts  42  extending through the bosses  48 , and the nuts  59  started but not tightened. Bolts by which the housing is mounted on the structure extend through the bolt holes  37 , but are not initially tightened. The pulley is aligned, the loosely mounted housing itself and the untightened spheres permitting accurate alignment in spite of any structural inaccuracies of the support structure. The bolts by which the housing is mounted on the structure are then tightened. The nuts  59  on the bolts  42  are then torqued to a torque value producing predetermined pressure on the spheres  20  and  22 , that pressure being determined by the size and expected load of the pulley, but being readily calculable.  
         [0021]    Numerous variations in the construction of the mounting assembly of this invention, within the scope of the appended claims, will occur to those skilled in the art in the light of the foregoing disclosure. For example, although the present arrangement is preferred, the sphere and socket mounting can be applied to only one end of the shaft or shaft extension. The pin and slot can be omitted entirely. A boss or pin in the outer surface of the sphere can be seated in a well or slot in the socket seat. An axial boss or bar or pin carried by the mounting block can be directed through an hourglass-shaped channel in the sphere or vice versa. The ends of the shafts can be differently formed, as, for example, polygonally or otherwise non-circularly instead of with flats. The flats and corresponding sphere seats can be oriented differently, as for example rotated ninety degrees from the position shown in FIGS. 1, 3,  4  and  5 . The sphere can be made in one piece and mounted on the shaft extension before it is mounted in the bearing housing. The socket can be made to enclose the sphere more completely, and the open end of the seat in which the shaft end is mounted can be closed, for food conveyor applications, although the construction shown is an improvement over the prior art in that respect. As has been indicated, the sphere assembly can be provided at one or both ends. These variations are merely illustrative.