Abstract:
A support assembly for supporting a rotating shaft relative to a structure in which a first magnetized member is attached to the shaft for rotation therewith, a support member is connected to the structure and at least one damper member connects the support member to a second magnetized member for supporting the second magnetized member in a portion relative to the first magnetized member. The respective magnetic fields of the first and second magnetized members are such that radial deflective movement of the shaft, and therefore the first magnetic member, causes corresponding radial movement of the second magnetized member which is dampened by the damping member.

Description:
This application is a division of application Ser. No. 09/053,480 filed on Apr. 1, 1998, now U.S. Pat. No. 6,057,618. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to an assembly for supporting a shaft and, more particularly, to a non-contacting support assembly for supporting a relatively long, rotating shaft without the use of grease lubricated bearings and associated apparatus. 
     There are several applications in which a relative long shaft must be supported for relative high-speed rotational movement. For example, the tail rotor drive shaft of a helicopter, or an interconnecting drive shaft of a tilt rotor aircraft must be supported in a manner to prevent misalignment of the shaft yet permit rotation of the shaft at relatively high supercritical speeds. Most systems for supporting these types of shafts employ a plurality of grease lubricated bearings and hanger brackets which are expensive, heavy and cumbersome and require heavy maintenance. Also, to accommodate angular misalignment, expensive and heavy couplings are required. Further, subcritical shafts have to be relatively stiff so that they can rotate at speeds below their resonant frequencies to prevent instability. 
     Additional problems arise when the shaft rotates at supercritical speeds since a damping element and/or a motion limiter, such as a squeeze film damper or a friction damper, is usually required. However, these devices must be made to precision tolerances, and require accurate shaft alignment and regular inspections and maintenance, all of which are expensive. 
     Therefore, what is needed is a relative inexpensive and lightweight support assembly for supporting a rotating shaft according to which the shaft does not contact the support structure or dampers and therefore does not require grease lubricated bearings, hangers and the like, while eliminating squeeze film dampers and friction dampers. Also, a support assembly of the above type is needed which requires relatively little maintenance yet enables the shaft to rotate at supercritical speeds while maintaining shaft stability and maintaining the shaft alignment to the desired shape and position. 
     SUMMARY OF THE INVENTION 
     Accordingly, the support assembly of the present invention is adapted to support a rotating shaft relative to a structure and includes a first magnetized member attached to the shaft for rotation therewith. A support member is connected to the structure and to a second magnetized member for supporting the second magnetized member in a position relative to the first magnetized member. The respective magnetic fields of the first and second magnetized members are such that radial deflective movement of the shaft, and therefore the first magnetic member, causes a radial force to be transmitted to the second magnetized member. The radial force causes radial movement of the second magnetized member which is dampened by the support member. The equal and opposite radial forces on the first magnetized member tends to maintain the shaft&#39;s radial location and thus keep it aligned. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric view of two support assemblies of the present invention show supporting the center section of an elongated rotating shaft 
     FIG. 2 is an enlarged isometric view of the support assembly of FIG.  1 . 
     FIG. 3 is an isometric view similar to that of FIG. 2 but depicting the support assembly of FIG. 2 viewed from an opposite side and in a reduced scale. 
     FIG. 4 is a perspective view of a component of the support assembly of FIGS. 1-3. 
     FIGS. 5 and 6 are schematic views depicting operational principles of the support assembly of FIGS.  1 - 3 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1 of the drawings, the reference numeral  10  refers to a shaft which is supported for rotation relative to a support member, or plate,  12 . For the purpose of example it is assumed that the shaft  10  is the tail rotor drive shaft of a helicopter or the interconnecting drive shaft of a tilt rotor aircraft, and the plate  12  is a structural support member of the helicoptor or aircraft. Two support assemblies employing features of the present invention are shown, in general, by the reference numerals  14  and  16  and are adapted to support the shaft  10  in a slightly elevated position relative to the plate  12 . 
     The support assembly  14  is shown in detail in FIGS. 2 and 3 and includes two spaced brackets  20  and  22  that are bolted to the plate  12 . A pair of turnbuckles  24  and  26 , of a conventional design, connect the brackets  20  and  22 , respectively, to a bracket  30 . The bracket  30  is generally U-shaped and has two spaced parallel legs  30   a  and  30   b  that extend vertically as viewed in FIG.  2 . The respective ends of the turnbuckle  24  are mounted for pivotal movement relative to the bracket  20  and the leg  30   a  of the bracket  30 , and the respective ends of the turnbuckle  26  are mounted for pivotal movement relative to the bracket  22  and the leg  30   b  of the bracket  20 , all in a conventional manner. The turnbuckles  24  and  26  include outer sleeves  24   a  and  26   a, respectively, which, when manually rotated, axially expand or contract the turnbuckles, also in a conventional manner and for reasons to be described. 
     An expansion bolt  32  is in threaded engagement with a threaded bore (not shown) provided in the bracket  20  and has a head portion connected to the bracket  30  by a bolt  34  extending through aligned openings in the bracket  40  and through an opening in the head portion. An expansion bolt  36  is in threaded engagement with a threaded bore (not shown) provided in the bracket  22  and has a head portion connected to the bracket  30  by a bolt  38  extending through aligned openings in the bracket  30  and through an opening in the latter head portion. The expansion bolts  32  and  36  can be axially expanded and contracted by rotating the bolts in a conventional manner. As a result of the foregoing, expansion and contraction of the expansion bolts  32  and  36  and the turnbuckles  24  and  26 , adjust the position of the bracket  30  in an axial direction relative to the shaft  10 , as well as its angular position relative to a vertical and horizontal axis as viewed in FIGS. 2 and 3, for reasons to be described. 
     Two horizontally-spaced, parallel damping members  40  and  42  are mounted at one of their ends to the bracket  30  by a plurality of bolts  44  and  46 , respectively. The damping members  40  and  42  are rectangular in cross section and extend upright and horizontally as viewed in FIGS. 2 and 3. A bracket  50  is provided in a spaced relation to the bracket  30  and is connected to the other ends of the damping members  40  and  42  by a plurality of bolts  52  and  54 , respectively. The bracket  50  has a central opening  50   a  for receiving the shaft with ample clearance. 
     Two vertically-spaced, parallel damping members  60  and  62  are mounted at one end to the bracket  50  by a plurality of bolts  64  and  66 , respectively. The damping members  60  and  62  are rectangular in cross section and extend horizontally as viewed in FIGS. 2 and 3. The damping members  40 ,  42 ,  60  and  62  are angular spaced at ninety degree intervals. 
     A substantially disc-shaped, metal casing  70  is connected to the other end of the damping member  60  by a pair of spaced mounting plates  72   a  and  72   b  affixed to one face of the casing, and by three bolts  74  that extend though aligned holes in the mounting plates and the damping member. Although not shown in the drawings it is understood that the other end of the damping member  62  is connected to the casing  70  by a pair of spaced mounting plates and bolts which are identical to the mounting plates  72   a  and  72   b  and the bolts  74 , respectively. The casing  70  has a central opening  70   a  that receives the shaft  10  with ample clearance. 
     With reference to FIG. 4, the damping member  60  is formed by three stacked elastomeric damping pads  80   a - 80   c.  The pad  80   a  is sandwiched between two relatively thin, plates  82   a  and  82   b,  the pad  80   b  is sandwiched between the plate  82   b  and an additional plate  82   c,  and the pad  80   c  is sandwiched the plate  82   c  and an additional plate  82   d.  The plates  82   a - 82   f  extend beyond the ends of the pads  80   a - 80   c,  and six blocks  84   a - 84   f  of a strong rigid material, such as aluminum, are disposed at the respective ends of the pads and between the respective plates. 
     To assemble the damping member  60 , the plates  82   a - 82   d  and the blocks  84   a - 84   f  are assembled as shown in FIG.  4  and the elastomer pads  80   a - 80   c  are molded or bonded in the cavities formed by the plates and the blocks to form a unitary member. The plates  82   a - 82   d  and the blocks  84   a - 84   f  each have openings therethrough so as to receive the bolts  64  and  74  (FIGS. 2 and 3) and thus permit a rigid mounting of the damping member  60  to the bracket  50  and to the plates  72   a  and  72   b.  It is understood that the damping members  40 ,  42  and  62  are identical to the damping member  60  and thus will not be described in detail. The use of two damping members  40  and  42 , as well as two damping members  60  and  62 , allows radial movement of the casing  70  without causing any tilting, or angular movement, of the casing. 
     Referring again to FIGS. 2 and 3, a metal, disc-shaped casing  90  is provided that is identical to the casing  70  with the exception that the casing  90  is connected to the shaft. In this context the casing  90  has a central opening (not shown) that receives the shaft  10  with minimal clearance and the casing is connected to the shaft in any conventional manner such as providing an axial flange, or the like, on the casing for securing to the shaft. The casing  90  thus rotates with the shaft  10  during its operation. 
     The support assembly  14  is installed relative to the support plate  12  (FIG. 1) and to the shaft  10  so that the casing  70  is in a closely-spaced, parallel relationship with the casing  90  so as to inhibit deflective movement of the shaft in a manner to be described. 
     As shown in FIGS. 5 and 6, the back side of the fixed casing  70  and the front facing side of the rotating casing  90  each contain a plurality of radially spaced magnetic rings  92  and  94 , respectively. The rings  92  in the casing  70  are arranged with their poles in an alternating orientation, the rings  94  in the casing  90  are arranged in an alternating orientation, and the rings  92  are arranged relative to the rings  94  so that the facing poles of the respective rings are opposite in polarity. Since the rings  92  will thus be attracted to the rings  94  in an axial direction, the support assembly  14  is positioned relative to the casing  90  a distance to maintain a magnetic attraction between the rings  92  of the casing  70  and the rings  94  of the casing  90 , thus creating an axial force that is reacted at one end of the shaft  10 . In this manner, the alternating poles of the respective rings  92  and  94  center the casing  70  relative to the casing  90  and provide a strong resistance to any relative radial motion between the casings. Thus, any radial deflective movement of the shaft  10  will be resisted by the magnetic force between the rings  92  and  94   
     As a result of the above, the support assembly  14  provides a non-contacting, support of the shaft in an elevated position relative to the support plate  12  (FIG.  1 ), while the magnetic rings  92  and  94  create a spring-like resistance to radial motion of the shaft. This latter effect allows radial forces to be carried from the rotating shaft  10  and the rotating casing  90  to the support assembly  14  which acts as a damper and a restoring spring to radial displacement of the shaft, without any impedance to rotation of the shaft. The magnetic force between the rings  92  and  94  also acts to oppose radial movement of the shaft and thus tender to maintain shaft alignment. 
     Since the support assembly  16  is identical to the support assembly  14  the assembly  16  will not be described in detail. 
     In operation, the shaft  10  is positioned in the elevated position relative to the support plate  12  as shown in FIG. 1, and the support assembly  14  is positioned with its casing  70  and the magnetic rings  92  in a closely spaced relationship with the casing  90  and its magnetic rings  94 . The turnbuckles  24  and  26  (FIGS.  2  and  3 ), together with the screws  32  and  36 , are adjusted so that the casing  70  extends in a parallel, aligned relation with the casing  90  in an axial direction relative to the shaft  10 . This adjustment of the turnbuckles  24  and  26  and the screws  32  and  36  also control the space between the casing  70  and the casing  90  so as to maintain a magnetic attraction between the casing and the casing yet insure that they do not touch. 
     The support assembly  14  thus provides a non-contacting, substantially frictionless, bearing for rotation of the shaft  10 . Also, any radial deflection of the shaft  10  causes corresponding movement of the casing  90 , and therefore the casing  70 , due to the magnetic attraction between the rings  92  and  94 . This movement of the casing  70  will be opposed by the damping and/or springlike resistance to this movement provided by the damping members  40 ,  42 ,  60  and  62 . For example, any deflections of the shaft  10  that causes vertical movement of the shaft to the position shown by the phantom lines in FIG. 6 for example, will cause corresponding movement of the casing  90  and therefore the casing  70  to the positions also shown by the phantom lines. This causes resultant shear forces to be applied to the damper members  60  and  62  and cause them to move from the positions shown by the solid lines to the positions shown by the phantom lines which dampens the deflective movement of the shaft. 
     Although not shown in the drawings, any deflections of the shaft  10  that causes movement of the casing  90 , and therefore the casing  70 , in a horizontal direction, e.g. Into or from the plane of the drawing with reference to FIG. 6, will cause corresponding shear forces to be applied to the damper members  40  and  42  and cause them to deflect in the same manner as discussed above in connection with the damper members  60  and  62 . Of course, deflections of the shaft  10  in a direction having both a horizontal and a vertical component will cause corresponding movement of all of the damper members  40 ,  42 ,  60  and  62  in the manners discussed above. 
     It is understood that the support assembly  16  functions in a manner identical to that of the support assembly  14  and that, when the shaft  10  is of a considerable length, additional support assemblies can be utilized as needed. Also, in situations in which a portion or portions of the shaft  10  must be curved by design due to its particular application, the support assemblies  14  and  16 , and any additional identical support assemblies, can easily be positioned relative to the shaft to deflect the shaft into the desired curvature, thereby avoiding the need for angular misalignment couplings. 
     It is apparent from the foregoing that the support assembly of the present invention provides significant advantages. For example, it supports the rotating shaft in a frictionless manner and therefore does not require grease lubricated bearings, hangers and the like, while eliminating squeeze film dampers and friction dampers. Also, it is relative inexpensive and lightweight. Further, it requires relatively little maintenance yet permits the shaft to rotate at supercritical speeds while maintaining shaft stability. Still further, the ratio of damping force to spring force exerted by the damping members can be varied. 
     It is understood that several variations can be made in the foregoing without departing from the scope of the invention. For example, any number of support assemblies can be used at spaced intervals along the shaft to be supported with the number depending on the length of the shaft. Also, also each magnetic ring  92  and  94  can be formed by a plurality of arcuate segments which together form a circular ring. Further, the number of damping pads, and therefore the associated plates, in each of the damping members can be varied. 
     It is understood that other modifications, changes and substitutions are intended in the foregoing disclosure and in some instances some features of the invention will be employed without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.