Abstract:
A flexible coupling and flexible belt or insert therefor, the belt or insert comprising a plurality of equally spaced circumferentially disposed identically shaped lobes centrally joined together by radial segments of a constant width.

Description:
BACKGROUND OF THE DISCLOSURE 
     Field 
     The subject disclosure pertains to new and improved flexible couplings and, more particularly, to a flexible belt or insert for such couplings having improved torque transmission qualities. 
     Description of Related Art 
     Flexible couplings have long been used for the purpose of transmitting rotation from one shaft to another. Such couplings are normally used in order to accommodate comparatively minor shaft alignment problems such as are occasionally encountered because of manufacturing or assembly errors. 
     Certain particular flexible couplings have been manufactured in the past so as to include two hubs or hub elements which are adapted to be connected to the shafts joined by the coupling. These hubs are each provided with extending lugs, teeth, or ribs serving as holding means so as to be engaged by corresponding projections on a band-like or belt-like motion transmitting means in order to cause the hubs to rotate in synchronism as one of the shafts is rotated. The bands or belts used in these prior couplings have been flexible, somewhat resilient belts capable of being wrapped around the hubs so that the projections on them engage the holding means on the hubs. 
     A metal band or ring has typically used to retain the belt in position wrapped around the hubs. The interior of the metal band is shaped and dimensioned so that the band may be slid axially relative to the hubs during the assembly and disassembly of the coupling so that the band fits over the belt when the coupling is assembled so as to conform closely to the exterior of the belt. 
     Some coupling designs have provided a pair of oppositely-disposed axial grooves in the outer surface of the belt and a pair of oppositely-disposed pins in the inner surface of the metal band. The pins are located so as to slide into the grooves as the metal band is installed along a line parallel to the axis of rotation of the hubs. The pins thus position the band and provide a degree of retention. However, if the shafts are grossly misaligned, the metal band will “walk-off” the belt, causing the coupling to come apart. The axial grooves have also been provided with an enlarged central portion such that the pins must be forced through the entrance of the axial groove and then “pop” into place in the central portion to give a tactile indication that the metal band is properly positioned with respect to the flexible belt. 
     Some prior coupling designs have also employed improved “lock-on” apparatus for improving the retention of the aforementioned metal retainer bands. This improved apparatus employs an axial groove for initially receiving a pin located on the underside of the metal retainer band and a circumferential groove opening into the axial groove and into which the retainer band pin may be rotated. 
     SUMMARY 
     The following is a summary of various aspects and advantages realizable according to various embodiments. It is provided as an introduction to assist those skilled in the art to more rapidly assimilate the detailed design discussion which ensues and does not and is not intended in any way to limit the scope of the claims which are appended hereto in order to particularly point out the invention. 
     Accordingly, in an illustrative embodiment, flexible coupling apparatus is provided comprising an inner hub component and an outer retainer component and a flexible torque transmitting belt or insert adapted to transmit torque between the hub component and retainer component. In an illustrative embodiment, the flexible torque transmitting belt or insert comprises a flexible plastic body having a plurality of equally spaced, circumferentially disposed lobes joined to one another by a plurality of radial segments of constant width. Each lobe has an outer surface adapted to engage the retainer and an inner surface adapted to engage the hub. Each lobe further has an outer surface of a same selected first width and an outer perimeter including a rounded portion disposed between first and second flat sides, the distance between the respective junctions of the flat sides with respective radial segments defining the first width, wherein each rounded portion has a centrally located flat surface at an outer tip thereof. The inner surface of each lobe has a selected second width and an inner perimeter including a rounded portion disposed between first and second flat sides, the distance between the respective junctions of the flat sides with a respective radial segment defining the second width, the rounded portion having a centrally located flat surface at an inner tip thereof. Each lobe further comprises a solid body of flexible or plastic material in the space encompassed by the inner and outer perimeters. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An illustrative embodiment of a flexible coupling insert and related coupling components will now be described in detail in conjunction with the drawings of which: 
         FIG. 1  is an exploded perspective of a prior art flexible coupling; 
         FIG. 2  is a side view of a flexible coupling according to an illustrative embodiment; 
         FIG. 3  is a side view of the flexible insert or belt of the coupling of  FIG. 2 ; 
         FIG. 4  is a side view of a single lobe of the flexible insert of  FIG. 3 ; 
         FIG. 5  is an end view of the flexible insert of  FIG. 3 ; and 
         FIG. 6  is a side cross sectional detail view taken at “VI” of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     A prior art flexible coupling is shown in  FIG. 1  and described in detail in U.S. Pat. No. 7,806,771, incorporated by reference herein in its entirety. The flexible coupling of  FIG. 1  includes a first hub  13 , a flexible insert  15 , a second hub  17  and a retainer member  19 . In illustrative embodiments, the hubs and retainer may be fabricated of steel or other suitable metals. 
     The first hub  13  includes an interior bore  22 , a first cylindrical segment  21  and a mounting flange  23  having a circular outer edge  25 . The face  27  of the flange  23  has a number of mounting holes  29  therein, each of which lies equally spaced on a circle of lesser diameter than that of the outer edge  25 . Conventional fastening devices such as a screw  28  may be used to secure the hubs to respective shafts. 
     The insert  15  may be fabricated from a flexible material such as, for example, a suitable urethane, and is preferably split so as to facilitate “wraparound” installation. The outer surface  31  of the insert  15  features a number of equally spaced exterior lobes  33 ,  34 ,  35 ,  36 ,  37 ,  38  projecting therefrom. The lobes, e.g.,  33 , are formed about equally spaced radii extending from the center of the insert  15 . The interior surface of the insert  15  features a number of interiorly projecting lobes  52 ,  53 ,  54 ,  55 ,  56 ,  57 , which, in the embodiment of  FIG. 1 , alternate with the exterior lobes  33 ,  34 , etc. In other words, as one proceeds about the circumference of the insert  15  one encounters a first exterior lobe  33 , then an interior lobe  52 , then a second exterior lobe  34 , then a second interior lobe  53 , etc. 
     The second hub  17  includes a cylindrical segment  43  and an insert-mounting segment or portion  45 . The insert-mounting portion  45  includes a number of wells or receptacles  47  which are shaped and dimensioned to mate snugly with the interior lobes, e.g.,  52 ,  53 , of the insert  15 . The hub  17  is preferably machined as a unitary part from a single piece of metal stock, but of course could be constructed in various other fashions. The second hub  17  further includes an interior bore  44 , typically of circular cross section dimensioned to receive a shaft of cooperating apparatus. 
     The interior  49  of the retainer  19  is specially contoured, shaped and dimensioned to receive and snugly mate with the exterior lobes, e.g.,  33 ,  34 , of the insert  15  when the coupling is in the assembled state. The retainer  19  has a first face  61  ( FIG. 3 ), which receives and passes the insert  15  into mating position with the exterior lobes  33 ,  34 , etc., and a second face  63  ( FIG. 1 ) which includes a depending edge or flange portion  65 , which prevents the insert  15  from passing through the retainer  19 , i.e., holds the insert  15  in a position wherein the insert  15  is preferably encased by the retainer  19 . 
     In the embodiment illustrated, the width of the retainer and the width of the insert are selected such that the face  71  of the insert  15  lies flush with the edge of the first face  61  of the retainer  19 , such that both the insert&#39;s face  71  and the edge  61  lie adjacent the flange face  27  in the assembled state. Thus, in assembly, the retainer  19  “captures” the insert  15  and is then attached to the first hub  13  via a number of fastening devices such as threaded bolts  73 . 
     In one embodiment, the width of the insert mating portion  45  of the second hub  17  is preferably selected such that its interior face terminates slightly short of the face of the insert  15 . Thus, the second hub  17  does not protrude through the insert  15  or extend to a point where it might contact the flange face  27  of the first hub  13 . 
     In operation in the assembled state, the insert  15  is snugly encased and transmits torque and absorbs minor misalignment without exerting axial thrusts on the cooperating shafts to which the first and second hubs  13 ,  17  are respectively attached. Thus, the insert  17  does not tend to exert forces on the hubs  13 ,  17  tending to move them parallel to the central axis  75  of rotation in typical applications. Such forces may cause a hub to move, for example, 15 thousandths of an inch, which is undesirable or unacceptable in certain applications. 
       FIGS. 2-6  illustrate a flexible coupling  101  according to an illustrative embodiment, which features an improved torque transmitting insert or belt  107  interfacing with a hub  105  and a retainer  103 . In one embodiment, the hub  105  and retainer  103  may be generally constructed and arranged as illustrated and described in connection with  FIG. 1  but with dimensioning altered to interface with the improved torque transmitting belt  107 . In illustrative embodiments, the flexible insert  107  may be constructed of a flexible or plastic material, such as, for example, a suitable urethane and may be split to facilitate wrapping around a hub  105  without having to move any equipment. The flexible insert design according to the illustrative embodiments and the cooperating shape of the interfacing receptacles of the hub and retainer yield markedly improved performance over prior art designs. 
     In particular, with reference to  FIG. 3 , the insert  107  of an illustrative embodiment features a plurality of identically shaped lobes  109  interconnected by identically shaped radial segments  111 , each radial segment  111  having the same radial length and the same thickness d2. In one illustrative embodiment, the diametric distance d3 between oppositely disposed lobe pairs is 2.69 inches, the distance d1 is 0.9812 inches, and the thickness d2 of each radial segment  111  is 0.2553 inches. In this illustrative embodiment, the distances d4, d5, and d6 are respectively 1.6248, 1.2765 and 0.2460 inches. These distances are the distance between the junction of the outer perimeter of a lobe  109  with its adjacent segments  111 , the distance between the beginning points of the radiused or rounded portion of the outer perimeter of each lobe  109 , and the width of the flat portion  117  of the tip of the outer perimeter of each lobe  109 . The distance d10 between the midpoints of the inner and outer lobe perimeters in this illustrative embodiment is 1.6425 inches. 
     In the illustrative embodiment, each flat lobe side  113 ,  115 , makes a respective angle Θ3, Θ4, with a vertical line bisecting the lobe  109 . In one embodiment, Θ3 and Θ4 are each thirty degrees. 
     With reference to  FIG. 4 , further details of the illustrative lobe  109  are provided. In particular, the linear inner lobe sides  119 ,  121  form respective 30 degree angles Θ1, Θ2, with a vertical line bisecting the lobe  109 , while dimensions d7, d8 and d9 are respectively 1.5032, 0.8386 and 0.0808 inches. Dimension d7 is the distance between the junction of the interior of the lobe  109  with its respective adjacent segments  111 , while dimension d9 is the width of the flat tip of the interior perimeter of the lobe  109 . Distance d8 is the width of the rounded or radiused portion of the lobe  109  which joins the flat sides  119 ,  121 . 
       FIG. 6  illustrates the interface between the flexible insert  107  and it&#39;s mating retainer  103  and hub  105 . In particular, in the illustrative embodiment, clearances C1, C2, C3, C4, and C5 are respectively: 0.0300, 0.0175, 0.0325, 0.0175, and 0.0088 inches. Clearances C1 and C2 are the distances between the radial segment  111  and the interior retainer surface  131  and exterior spoke surface  133 , respectively. Clearances C3 and C4 are the distances between the flat surface of the outer perimeter of the lobe  109  and its mating retainer surface  135  and the distance between the flat surface of the interior perimeter of the lobe  109  and its mating hub surface  137 , respectively. The clearance C5 is the distance between the flat surfaces of the interior lobe and the flat side surface of a hub spoke. As those skilled in the art will appreciate, the dimensioning of the various widths and radii illustrated in  FIGS. 3, 4 and 6 , of course, varies, for example, with application and size of a particular coupling. According to one embodiment, as the size (diameter) of the coupling increases, the dimensions just set forth will proportionately increase. 
     In the illustrative flexible insert design employing “unitary” lobes as disclosed in  FIGS. 2-6 , the six lobes  109  work in unison to transfer power and provide much greater drive contact with the metallic hub  105  and retainer  103  and, in illustrative embodiments, has enhanced horse power transfer capacity between the driving and driven hubs by ⅓ throughout a range of coupling sizes, while producing less axial thrust loads and spreading stress more uniformly over a larger area of the insert. 
     Couplings according to various embodiments disclosed herein further provide free axial float and in particular applications, enable the driving and driven shafts to be positioned at greater distances from one another, thereby accommodating greater thermal growth of shaft. 
     Couplings as disclosed above continue the advantage of combining advantageous aspects of both shear and compression couplings. In particular, the disclosed couplings normally operate in compression, which prevents exertion of axial thrusts, but can still shear to protect equipment in the event of lock-up or overload, etc. An example is the case of shredding apparatus used to shred recycled material, where occasionally, material will include prohibited foreign objects which can lock the shredder. In such case, the insert of a coupling according to the disclosed design will advantageously shear rather than break the associated equipment. 
     While the present invention has been described above in terms of specific embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. The role of “driving” and “driver hubs” may be reversed and dimensioning adapted to particular sizes and conditions. Thus, the present invention is intended to cover various modifications and equivalent methods and structures included within the spirit and scope of the appended claims.