Abstract:
The present invention relates to a drive assembly including an adapter that enables the use of a lightweight backstopping clutch with a driven shaft. The adapter is coupled to the driven shaft for rotation therewith and forms a stub shaft smaller than the driven shaft. The clutch has an inner race that is disposed about the stub shaft and an outer race fixed against rotation so as to allow rotation of the stub shaft and driven shaft in one direction and inhibit rotation in an opposition direction.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a drive assembly in which rotation in a single direction is allowed and in particular to a drive assembly with an adapter allowing the use of a lightweight backstopping clutch.  
       DISCLOSURE OF RELATED ART  
       [0002]     Numerous applications incorporate drive assemblies that provide a rotational force in one direction while prohibiting rotation in an opposite direction. Examples include inclined conveyors, escalators pumps, gear drives, fans, and other applications involving shaft rotation. The use of a backstopping clutch to prevent the reversal of shaft rotation in such applications is well known in the art. A backstopping clutch is designed to prevent a shaft or the rotational element from turning backwards or in the reverse direction when a motor is stopped. Traditionally, backstopping clutches have been used to allow for free rotation of the shaft in a predetermined direction, while preventing the rotation of the shaft in the opposite direction.  
         [0003]     Prior coupling designs of a backstopping clutch with a driven shaft of a drive assembly have required the attachment of the clutch directly to the driven shaft. One problem with this method of assembly is the inability to accommodate various size driven shafts with these clutches. Second, large clutches are required in applications having large shafts. Another problem related to the current method is that the drilling and tapping of the driven shaft is labor intensive and limits the flexibility of coupling all of the drive assembly components to one another. Other coupling designs known in the art which couple the backstopping clutch and the driven shaft together are generally expensive, heavy and space demanding during manufacturing, especially due to the their requisite size requirements.  
         [0004]     Other prior art designs have resulted in placing size limitations on the components used in the drive assembly. This results in an inability to readily adapt the assembly for use. Consequently, specific driven shafts and clutch assemblies have to be specially sized to be attached to one another. There is a need to provide a drive assembly that allows for various sized clutches and driven shafts to be coupled together. Furthermore, there is a need to have a readily adaptable assembly that is not labor intensive during production.  
         [0005]     The inventors herein have recognized a need for a drive assembly having a backstopping clutch that will minimize and/or eliminate one or more of the above-identified deficiencies.  
       SUMMARY OF THE INVENTION  
       [0006]     The present invention relates to a drive assembly. The drive assembly includes a driven shaft. An adapter is coupled to the driven shaft for rotation therewith. The adapter further provides a stub shaft which is smaller than the driven shaft. The drive assembly includes a backstopping clutch having an inner race disposed about the stub shaft and an outer race fixed against rotation. The clutch allows rotation of the stub shaft and driven shaft in a first direction and inhibits rotation in a second direction opposite the first direction.  
         [0007]     The present invention further provides a method of assembling a drive assembly, comprising the steps of: providing a driven shaft, an adapter defining a closed bore on a first side and a stub shaft on a second side, a split ring having a plurality of arcuate portions, and a backstopping clutch; inserting the driven shaft through the split ring; removing a spacer between first and second arcuate portions of the split ring; inserting a fastener through the first and second arcuate portions; inserting an end of the driven shaft into the closed bore of the adapter; securing the split ring to the adapter using a fastener; placing an inner race of the clutch over the stub shaft; and fixing an outer race of the clutch against rotation.  
         [0008]     A drive assembly in accordance with the present invention is advantageous because it provides an assembly that is readily coupled together and is readily adaptable. Further, the assembly enables the coupling of clutches and driven shafts of various diameters and the use of relatively smaller, lightweight clutches in applications employing large shafts. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     Embodiments of the invention will now be described with reference to the accompanying drawings in which:  
         [0010]      FIG. 1  is a perspective view of the drive assembly of the present invention;  
         [0011]      FIG. 2  is a cross sectional view of a portion of the drive assembly of  FIG. 1 ;  
         [0012]      FIG. 3  is a cross sectional frontal view of a portion of the drive assembly of  FIG. 1 ; and  
         [0013]      FIG. 4  is the perspective view of a portion of the drive assembly of  FIG. 1 .  
         [0014]      FIG. 5   a  and  5   b  are cross sectional views of a portion of the drive assembly of  FIG. 2 .  
         [0015]      FIG. 6  is a flow chart of the method of assembly in accordance with the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]     Referring now to the drawings wherein like reference numerals are used to identify identical components in the various views,  FIGS. 1-2  illustrate one embodiment of a drive assembly  10  in accordance with the present invention. The drive assembly  10  includes a driven shaft  12  coupled to an adapter  14  for rotation therewith and for engaging a backstopping clutch  16 . Driven shaft  12  may be used to provide rotation in a variety of applications including inclined conveyors, escalators pumps, gear drives, fans, and other applications involving shaft rotation. A split ring  18  is provided around driven shaft  12  for coupling of driven shaft  12  to adapter  14 .  
         [0017]     As can be seen in  FIGS. 1 and 2 , driven shaft  12  is engagingly received by adapter  14 . In particular, adapter  14  defines a closed bore  20  for receiving driven shaft  12 . Closed bore  20  reflects the size and shape of one end of driven shaft  12  for engagingly receiving driven shaft  12 . Upon the rotation of driven shaft  12 , adapter  14  reflects the same rotation due to the engagement of driven shaft  12  with adapter  14 . A stub shaft  22  is further provided by adapter  14  on which backstopping clutch  16  is supported. Stub shaft  22  may be smaller in diameter than driven shaft  12 , thereby enabling use of a smaller backstopping clutch  16  than would be required if clutch  16  were disposed about shaft  12 . Accordingly, stub shaft  22  may vary in size based on the size configurations of the assembly components. Stub shaft  22  is provided on the opposite side of adapter  14  from the side providing closed bore  20 . The coupling of stub shaft  22  with backstopping clutch  16  allows for the transfer of a braking force from clutch  16  to adapter  14  and shaft  12  to prevent rotation of shaft  12  in one direction.  
         [0018]     As seen in  FIG. 2 , backstopping clutch  16  includes an inner race  24  and an outer race  26 . Inner race  24  of clutch  16  rotates with driven shaft  12  through the coupling of inner race  24  to stub shaft  22  of adapter  14 . The relative speed of rotation of inner race  24  may vary based on the relative size ratio of the diameter of stub shaft  22  to the diameter of driven shaft  12 . Inner race  24  is permitted to rotate in one given direction through its engagement with stub shaft  22 . Therefore, the engaging rotation of driven shaft  12  with adapter  14  results in the simultaneous transferred rotation of inner race  24 .  
         [0019]     Referring to  FIG. 3 , clutch  16  further provides a plurality of spring loaded plungers  36  disposed about the circumferential periphery of inner race  24 . Each of the spring loaded plungers  36  are engagingly coupled to a locking roller  38 . The individual spring loading of locking rollers  38  provide constant force between locking rollers  38  and both the inner race and outer race,  24  and  26 , respectively. Locking rollers  38  engage a cylindrical groove  40  provided by outer race  26 . The cylindrical groove  40  provided by outer race  26  reflects the circular exterior of roller  38  for receiving and providing a surface of engagement for each of the locking rollers  38 . Upon rotation of inner race  24  in a backward direction, locking roller  38  prevents further backward rotation of inner race  24  by pressing resistance upon outer race  26 . The force provided by spring loaded locking rollers  38  against outer race  26  ensures instantaneous lock-ups when switching from various engagement modes. Various designs of effective locking rollers may be used and are not limited to solely cylindrical configurations. Similarly the provided groove for engagement of the locking rollers may vary in design to reflect the configuration of the rollers.  
         [0020]     Outer race  26  of the clutch  16  is fixed from rotation due to the engagement of outer race  26  with a torque arm  28 . Torque arm  28  includes a head  30  and a shaft  32 . Head  30  of torque arm  28  is coupled with outer race  26  of clutch  16  thereby fixing outer race  26  against rotation. More particularly, outer race  26  is press fit into head  30  thereby securely fixing outer race  26  against head  30 . Various other methods may be used to fix outer race  26  from rotating within head  30  of torque arm  28  in addition to the press fit embodiment as described by the present invention. Torque arm  28  is further provided with shaft  32 . Shaft  32  provides a threaded portion  33  on end  34 . As shown in  FIG. 4 , head  30  provides a threaded aperture  31  for engagingly receiving threaded portion  33  of shaft  32 . The other end of shaft  32  is held in a fixed position by mounting to a frame or similar stationary structure.  
         [0021]     As can be seen in  FIG. 2 , a split ring  18  is further disposed around driven shaft  12  and is coupled to adapter  14 . More particularly, with reference to  FIGS. 5   a  and  5 b, split ring  18  includes a plurality of arcuate portions  42 . Various configurations of arcuate portions  42  may be used, ranging in the use of at least one arcuate portion to the use of a plurality of arcuate portions configured together to provide split ring  18 . Arcuate portions  42  are further provided with one or more spacers  44  between each of the arcuate portions  42 . The use of spacer  44  allows for configuring the split ring  18  to a proper size and configuration for coupling around driven shaft  12 . Prior to positioning of split ring  18  around driven shaft  12 , split ring  18  is bored to provide an aperture  46 . Aperture  46  is bored to a dimension reflective of driven shaft  12 , thereby resulting in a clearance or slip fit of split ring  18  with driven shaft  12 . Split ring  18  is coupled to driven shaft  12  by receiving one end of driven shaft  12  through aperture  46 . Each of the spacers  44  are removed and arcuate portions  42  are fixedly attached together though the use of one or more fasteners  48 . Fasteners  48  could comprise bolts, screws, pins, adhesives, or welds. Fasteners  48  maybe provided perpendicular to a plane containing the axis of rotation of driven shaft  12 . The fastening of arcuate portions  42  around driven shaft  12  results in split ring  18  being torqued down and distorted upon its gripping of driven shaft  12 . The fastening of arcuate portions  42  results in split ring  18  being fixedly coupled to driven shaft  12 .  
         [0022]     The end of driven shaft  12  having split ring  18  is coupled to adapter  14  through the use of at least one axially extending fastener  50 . Again, various fastener means known in the art may be used through this application, including but not limited to, bolts, pins, adhesives, welds, screws and other fasteners known in the art. Adapter  14  is placed on driven shaft  12  and fastened to split ring  18  via clearance holes  52 . Clearance holes  52  are provided to accommodate the split ring distortion and securely attach adapter  14  to split ring  18 .  
         [0023]     Referring to  FIG. 6 , a method of assembling the drive assembly  10  of the present invention is described. The inventive method may begin with step  54  of providing a driven shaft  12 , an adapter  14  defining a closed bore  20  on one side and a stub shaft  22  on another side, a split ring  18  having a plurality of arcuate portions  42  and a backstopping clutch  16 . As described above, split ring  18  may further includes a plurality of spacers  44  between arcuate positions  42 . The method may continue with step  56  of boring split ring  18  to form aperture  46  to reflect the dimensions of driven shaft  12 . The method may continue with steps  58 ,  60  of inserting driven shaft  12  though split ring  18  (in particular, through aperture  46  of split ring  18 ) and removing spacers  44  between arcuate portions  42 . The method may continue with the step  62  of inserting a fastener  48  through the arcuate portions  42  of split ring  18 . As fastener  48  is inserted, split ring  18  is torqued down around driven shaft  12  and distorted for securing around shaft  12 . The method may continue with the step  64  of inserting the end of driven shaft  12  into closed bore  20  of adapter  14 . Once adapter  14  is fitted over the end of driven shaft  12 , the method may continue with the step  66  of securing split ring  18  to adapter  14  using one or more fasteners  50 . As mentioned above, axially extending fasteners  50  may be inserted through adapter  14  and into clearance holes  52  to secure adapter  14  and split ring  18  together on driven shaft  12 . The method may continue with the step  68  of placing an inner race  24  of clutch  16  over stub shaft  22  of adapter  14 . The method may conclude with the step  70  of fixing an outer race  26  of clutch  16  against rotation. Step  70  may include the substeps  72 ,  74  of pressing the outer race  26  into a head  30  of a torque arm  28  and threading a shaft  32  into head  30  with the shaft  32  fixed against rotation.  
         [0024]     A drive assembly and method of assembly in accordance with the invention has several advantages. First, the inventive device and method enable relatively easy assembly while providing effective backstopping methods. Second, the inventive device and method enable assembly of components despite variations of size among clutches and driven shafts.  
         [0025]     While the invention has been particularly shown and described with references to preferred embodiments thereof, it is well understood by those skilled in the art that various changes and modifications can be made in the invention without departing from the spirit and scope of the invention.