Abstract:
A method comprises accessing a vibratory device having a rotor and first and second eccentric weights. The first weight is initially attached to the rotor&#39;s shaft in a manner such that its center of the mass is offset from the shaft in a first radial direction. The second weight is initially attached to the shaft in a manner such that its center of the mass is also offset in the first radial direction. The method further comprises reorienting the first and second weights relative to the shaft in a manner such that their centers of the mass are offset in a second radial direction. By performing these steps, the location of greatest bearing surface wear rate on the shaft is circumferentially relocated about the shaft. As such, the service life of an eccentric weight vibratory device is thereby extended.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    Not Applicable 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable. 
       APPENDIX 
       [0003]    Not Applicable. 
       BACKGROUND OF THE INVENTION 
       [0004]    1. Field of the Invention 
         [0005]    This invention pertains to vibratory devices of the type used in the bulk material handling industry. More particularly, this invention pertains to a rotary vibratory device having repositionable eccentric weights and to methods for extending the useful life of such rotary vibratory devices. 
         [0006]    2. General Background 
         [0007]    Vibratory devices are used throughout the bulk material handling industry for various purposes. Vibratory devices are often attached to bulk material transfer chutes and bulk material storage hoppers to prevent bulk material from clinging to the walls of such chutes and hoppers. Vibratory devices are also utilized on sifting screens to prevent larger material from clogging the sifting screens and to speed the flow of material passing through the screens. 
         [0008]    A common type of vibratory device is the rotary vibratory motor, wherein eccentric weights are rotationally driven by, and rotate about, a shaft and thereby create a oscillating forces. Other types of vibratory devices include, but are not limited to, acoustical vibration devices, air driven rotary vibrators, and linear vibrators. The present invention pertains specifically to the rotary vibratory device wherein on or more eccentric weight is rotationally driven by a shaft (hereafter referred to simple as a rotary vibratory device). 
         [0009]    In rotatory vibratory devices, the forces generating in by the rotating eccentric weights are transmitted to the motor housing via the bearings that support the rotor shaft. In view of the eccentricity of the weights, the bearing forces acting on the rotary shaft peak on the side of the bearing shaft that is closest to the center of mass of the eccentric weights, while the opposite side of the rotor shaft sees little, if any, bearing load. As a result, the portion of the bearing surface of the shaft closest to the center of mass of the eccentric weights wears at the greatest rate. 
       SUMMARY OF THE INVENTION 
       [0010]    The inventors of the present invention have appreciated that the useful life of rotary vibratory devices can be extended by periodically altering the location of greatest bearing surface wear rate circumferentially about the shaft. The inventors have also developed rotary vibratory devices that are configured and adapted to allow for periodically altering the location of greatest bearing surface wear rate with minimal effort. 
         [0011]    In one aspect of the invention, a method of extending the service life of an eccentric weight vibratory device comprises accessing a vibratory device. The vibratory device comprises a rotor and first and second eccentric weights. The rotor has a central shaft about which the rotor is configured to rotate. The shaft has opposite first and second end portions. The first eccentric weight is initially attached to the first end portion of the shaft in a manner such that the center of the mass of the first eccentric weight is offset in a first radial direction from the shaft. The second eccentric weight is initially attached to the second end portion of the shaft in a manner such that the center of the mass of the second eccentric weight is also offset in the first radial direction from the shaft of the rotor. The method also comprises reorienting the first eccentric weight relative to the shaft in a manner such that the center of the mass of the first eccentric weight is offset in a second radial direction from the shaft, and reorienting the second eccentric weight relative to the shaft in a manner such that the center of the mass of the second eccentric weight is offset in the second radial direction from the shaft. By performing these steps, the location of greatest bearing surface wear rate on the shaft is circumferentially relocated about the shaft. As such, the service life of an eccentric weight vibratory device is thereby extended. 
         [0012]    In another aspect of the invention, a vibratory device comprises a rotor having a shaft. The shaft has a shaft axis about which the rotor is configured to rotate. The shaft also comprises a first end portion having a plurality of keyways that are spaced circumferentially about the shaft axis relative to each other. An eccentric weight is mounted on the first end portion of the shaft. The eccentric weight has a center of mass that is offset from the shaft axis and has an opening through which the first end portion of the shaft extends. The opening comprises a keyway. The vibratory device also comprises a key. The key is positioned between one of the keyways of the shaft and the keyway of the eccentric weight in a manner such that the first eccentric weight is not able to rotate relative to the shaft about the shaft axis. 
         [0013]    Further features and advantages of the present invention, as well as the operation of the invention, are described in detail below with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  depicts a perspective view of a rotary vibratory device. 
           [0015]      FIG. 2  depicts the vibratory device of  FIG. 1 , with its end caps removed for servicing. 
           [0016]      FIG. 3  depicts an initial configuration of a plurality of eccentric weights mounted on the shaft of the rotor of the vibratory device shown in  FIGS. 1 and 2 . 
           [0017]      FIG. 4  depicts another view of the rotor and weights in the initial configuration. 
           [0018]      FIG. 5  depicts the rotor and weights from the same viewing angle as shown in  FIG. 4 , but is shown with the weights disengaged from the shaft keys. 
           [0019]      FIG. 6  depicts the rotor and weights from the same viewing angle as shown in  FIGS. 4 and 5 , and shows the weights and shaft keys repositioned about the rotor shaft ninety degrees. 
           [0020]      FIG. 7  depicts the rotor and weights from the same viewing angle as shown in  FIGS. 4-6 , and shows the weights reengaged with the shaft keys after having been rotationally repositioned. 
       
    
    
       [0021]    Reference numerals in the written specification and in the drawing figures indicate corresponding items. 
       DETAILED DESCRIPTION 
       [0022]    A preferred embodiment of a rotary vibratory device in accordance with the present invention is shown in  FIGS. 1 and 2 . The vibratory device  10  comprises an outer housing  12  having removable end caps  14 . Internally, the vibratory device  10  comprises a rotor  16  having a shaft  18 . A plurality of eccentric weights  20  are mounted on the shaft  18  of the rotor  16  for rotation therewith. 
         [0023]    Although some rotary vibratory devices may include only one eccentric weight or have eccentric weights only on one end of rotor shaft, the preferred embodiment of a rotary vibratory device  10  in accordance with the present invention comprises at least one eccentric weight  20  at each of the opposite end portions  22  of the rotor&#39;s shaft  18 . Preferably the weights  20  are balanced such that the forces acting on each end portion of the shaft  18  equal each other and act in the same direction. 
         [0024]    As is shown most clearly in  FIGS. 3-7 , the rotor  16  comprises an armature  24  that is centrally positioned on the shaft  18 . The rotor  16  also comprises a plurality of bearings  26  that attach the rotor to the housing  12  for rotation (and transmit the vibrational forces to the housing). Each of the opposite end portions  22  of the shaft  18  comprises an anular groove that is configured to receive a removable retaining ring  28 . Additionally, each of the opposite end portions  22  of the shaft  18  comprises a plurality of keyways  30  that are circumferentially spaced from each other about the shaft. Preferably, each of the opposite end portions  22  of the shaft  18  comprises two or more axially oriented keyways  30  that are evenly spaced apart from each other about the shaft. The keyways  30  are preferably simple slots milled into the shaft  18 . The eccentric weights  20  attached to the end portions  22  of the shaft include outboard eccentric weights  32  and inboard eccentric weights  34 . Each end portion  22  of the rotor shaft  18  has one outboard weight  32  and one inboard eccentric weight  34  attached thereto. Each of the eccentric weights  20  comprises a mounting hole  36  that is offset from the center of mass of the eccentric weight and that is dimensioned to fit snugly around the shaft  18 . Each of the eccentric weights  20  also comprises slit  38  that extends into the mounting hole  36  and that allows the eccentric weight to be tightly clamped to the shaft via a bolt  40 . Moreover, the mounting hole  36  of at least each of the inboard eccentric weights  34  also comprises an axially extending keyway  42  that is preferably milled into the weight. The rotor  16  further comprises a key  44  and preferably a pair of adjustment guides  46 . 
         [0025]    The eccentric weights  20  of the vibratory device  10  are initially axially and rotationally locked to the shaft  18  of the rotor  16  in an initial position. The keyway  42  of each of the inboard eccentric weights  34  is aligned with one of the keyways  30  of the shaft  18  and one of the keys  44  is positioned between said keyways in a manner rotationally locking the weight to the shaft. Given that each end portion  22  of the shaft  18  preferable has at least two keyways  30 , each inboard eccentric weight  34  is positionable in alternative positions relative to the shaft. As mentioned above, a bolt  40  also clamps each of the eccentric weights to the shaft  18  in a manner such that the weights cannot rotate or axially slide relative to the shaft. Thus, the keys  44  and keyways  30 ,  42  serve primarily to index the inboard eccentric weights  34  and to ensure that they are aligned with each other. The outboard eccentric weights  32  may or may not be aligned with the inboard eccentric weights  34 . In other words, the center of mass of the outboard eccentric weights  32  may be offset from the axis of rotation of the shaft  18  in a different direction than is the center of mass of the inboard eccentric weights  34 . Unlike the inboard eccentric weights  34 , the orientation angle of the outboard eccentric weights  32  relative to the shaft is infinitely variable since the outboard eccentric weights and the shaft are not keyed to each other. It should be appreciated that the rotational position of the outboard eccentric weights  32  relative to the inboard eccentric weights  34  determines the combined center of mass of the weights and the more out of alignment the inboard and outboard weights are, the closer the combined center of mass is to the axis about which the shaft  18  rotates. The radial distance between the combined center of mass of the eccentric weights  20  and the shaft axis determines the amplitude of the vibrations created by the vibratory device  10  at any given revolutions per minute. 
         [0026]    It should be appreciated that as the rotary vibratory device  10  operates, the greatest bearing load on the bearing surfaces of the shaft  18  (which engage the bearings  26  of the rotor  16 ) occur on the side of the shaft facing the center of mass of the eccentric weights  20 . As such, those portions of the shaft  18  wear faster than the other portions of the bearing surfaces of the shaft. Eventually the wear exceeds an acceptable amount. At that point or time, the vibratory device  10  can be serviced to change the location of the greatest bearing load on the bearing surfaces of the shaft  18 . To do this, a technician removes the end caps  14  of the vibratory device&#39;s  10  housing  12  to expose the eccentric weights  20  (see  FIG. 2 ). The technician then loosens the bolts  40  that secure the eccentric weights  20  to the end portions  22  of the shaft  18  of the rotor  20 . Thereafter the technician axially slides the eccentric weights  20  away from armature  24  of the rotor  16  to disengage the keyways  42  of the inboard eccentric weights  34  from the shaft keys  44 , as is shown in  FIG. 5  (note: although  FIGS. 3-7  show the rotor removed from the housing  12 , it is shown that way for clarity and the rotor remains in the housing during servicing). Preferably the end portions  22  of the shaft  18  are long enough such that the weights  20  can be axially slide on the shaft enough to disengage the keyways  42  of the inboard eccentric weights  34  from the shaft keys  44  without removing the weights from the shaft (as is shown on the right side of the rotor  16  in  FIG. 5 ). To this end, the retaining rings  28  serve as end stops for preventing the eccentric weights  20  from sliding off of the rotor&#39;s  16  shaft  18 . With the shaft keys  44  exposed, the technician can remove the keys and place them in another set of the plurality of keyways  30  of the shaft, and then rotate the inboard eccentric weights  34  relative to the shaft  18  until the keyways  42  of the inboard eccentric weights are once again aligned with the shaft keys (as shown in  FIG. 6 ). Following that, the eccentric weights  20  are pushed axially inboard such that the shaft keys  44  lie between the keyways of the shaft  30  and the keyways  42  of the inboard eccentric weights  34  (as shown in  FIG. 7 ). The outboard eccentric weights  32  are also rotated into their proper orientation relative to the inboard weights  34 , using the adjustment guides (which include graduated markings showing the relative angles between the inboard and outboard weights). 
         [0027]    Following the servicing of the vibratory device  10 , the device will operate in the same manner that it did before servicing, except that the location of the greatest bearing load on the bearing surfaces of the shaft  18  will be different from before. Although the shaft  18  of the vibratory device  10  is shown in the figures having four keyways  30  at each of its opposite end portions  22 , preferably it only has two keyways at each end. Having only two keyways  30  at each end of the shaft  18  ensures that there won&#39;t be any overlap in the wear area on the inner bearing race of the shaft from one position to the next. Thus, the vibratory device  10  can continue to operate without risking failure. Moreover, if more than two keyways  30  are provided at each end portion  22  of the shaft  18 , the servicing procedure can be performed additional times (each time placing the key  44  in a yet to be used keyway  30  of the shaft  18 ). Thus, using the present invention, the useful life of the vibratory device  10  can be extended by at least twice that of standard vibratory device. It should also be appreciated that the key  44  and keyways  30 ,  42  of the vibratory device  10  are configured and adapted to assist a technician in rotationally indexing the eccentric weights  20  and are not the primary means for torsionally locking the eccentric weights to the shaft. 
         [0028]    In view of the foregoing, it should be appreciated that the invention has several advantages over the prior art. 
         [0029]    As various modifications could be made in the constructions and methods herein described and illustrated without departing from the scope of the invention, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative rather than limiting. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims appended hereto and their equivalents. 
         [0030]    It should also be understood that when introducing elements of the present invention in the claims or in the above description of exemplary embodiments of the invention, the terms “comprising,” “including,” and “having” are intended to be open-ended and mean that there may be additional elements other than the listed elements. Additionally, the term “portion” should be construed as meaning some or all of the item or element that it qualifies. Moreover, use of identifiers such as first, second, and third should not be construed in a manner imposing any relative position or time sequence between limitations. Still further, the order in which the steps of any method claim that follows are presented should not be construed in a manner limiting the order in which such steps must be performed, unless such and order is inherent.