Abstract:
A flexible coupling including a first hub having an inner face, a flexible insert having a plurality of exterior lobes and a plurality of interior lobes, a retainer ring having an interior which engages the exterior lobes of the flexible insert, and a second hub having an exterior surface contoured to engage the interior lobes of the flexible insert.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The invention set forth in this specification pertains to new and improved flexible couplings and, more particularly, to such couplings having advantageous features of both shear and compression style couplings.  
           [0003]    2. Description of Related Art  
           [0004]    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. Because of the fact that these devices are widely used and have been known and used for many years, many different types of flexible couplings have been proposed, built, and used.  
           [0005]    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.  
           [0006]    A metal band or ring is typically used to retain the belt in position wrapped around the hubs. The interior of the 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.  
           [0007]    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.  
           [0008]    In our U.S. patent application Ser. Nos. 08/742,372and 08/695,675, we have disclosed 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. In the embodiments illustrated in the referenced applications, the axial groove is bisected by a radial line which also bisects one of the lobes or projections of the flexible belt. The circumferential groove is relatively short, typically having been selected to be two times the width of the retainer ring pin. In practice, such apparatus must contend with vibrations, harmonics, rotation, misalignment and various stresses and forces on the component parts.  
         SUMMARY  
         [0009]    The following is a summary of various aspects and advantages realizable according to various embodiments of the invention. 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.  
           [0010]    Accordingly, disclosed hereafter is a flexible coupling including a first hub having an inner face and a flexible insert having a plurality of exterior lobes and a plurality of interior lobes. A retainer ring is provided having an interior which engages the exterior lobes of the first hub, while a second hub has an exterior surface contoured to engage the interior lobes. The exterior and interior lobes may each have a rounded contour formed between two flat faces, which facilitates torque transmission. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    An illustrative and presently preferred embodiment of the invention will now be described in detail in conjunction with the drawings of which:  
         [0012]    [0012]FIG. 1 is an exploded perspective of a coupling according to a preferred embodiment;  
         [0013]    [0013]FIG. 2 is a side view of the coupling of FIG. 1;  
         [0014]    [0014]FIG. 3 is a perspective end view illustrating a hub, insert and retainer components in assembled relation;  
         [0015]    [0015]FIG. 4 is a perspective view of the coupling in the assembled state;  
         [0016]    [0016]FIG. 5 is a side cross sectional view of an embodiment according to the invention;  
         [0017]    [0017]FIG. 6 is a side cross sectional view of an embodiment according to the invention; and  
         [0018]    [0018]FIG. 7 is a side cross sectional view of an embodiment according to the invention. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0019]    The coupling of the illustrative embodiment includes a first hub  13 , a flexible insert  15 , a second hub  17  and a retainer member  19 . 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 “screw”  27  may be used to secure the hubs to respective shafts.  
         [0020]    The insert  15  is preferably 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.  
         [0021]    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.  
         [0022]    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 .  
         [0023]    In the embodiment illustrated, the width “w 1 ” of the retainer and the width “w 2 ” 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 .  
         [0024]    As shown, for example, in FIG. 3, the width W 3  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 .  
         [0025]    In operation in the assembled state (FIG. 4), the insert 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.  
         [0026]    FIGS.  5 - 7  illustrate various design considerations according to a preferred embodiment of the invention. According to this illustrated embodiment, the insert  15  exhibits a constant shear section width d l . Each exterior lobe, e.g.,  33 , has respective flat sides  81  having a selected length d 2  and a central portion  83  between the two flat sides  81 . The central portion  83  has a circular outer contour of radius R 1 . Adjacent surfaces of the drive ring  19  are dimensioned to conform to the shape of the exterior lobe, e.g.,  53 , for example, in incorporating flat sections  85  adjacent the flat sides  81  of the outer lobes, the flat sections  85  having a length d 21 . The width d 3  of each exterior lobe is the same.  
         [0027]    Similar to the exterior lobes, each interior lobe, e.g.,  52 , has respective flat sides  87  of equal width d 4  and a central circular portion  89  connecting those sides  87  and having a radius R 2 . The corner to comer width d 6  of each interior lobe, e.g.,  52 , is the same. Finally, the insert includes a split  101  in one of the outside lobes  103  to provide for wraparound installation.  
         [0028]    The dimensioning of the various widths and radii illustrated in FIG. 6, of course, varies, for example, with application and size of a particular coupling. An illustrative dimensioning in inches for a coupling of the size under consideration is as follows:  
         [0029]    R 1 =1.875  
         [0030]    R 2 =1.625  
         [0031]    d 2 =0.730  
         [0032]    d 21 =0.725  
         [0033]    d 3 =3.978  
         [0034]    d 4 =0.423  
         [0035]    d 5 =0.510  
         [0036]    d 6 =3.325  
         [0037]    R 3 =0.100  
         [0038]    R 4 =0.100  
         [0039]    R 4  and R 3  are respectively inside corner lobe radii and outside comer hub wing radii implemented to resist tearing and cutting.  
         [0040]    [0040]FIG. 6 illustrates various clearances of interest with respect to a coupling according to embodiment of FIGS.  5 - 7 . The clearance c 2  is the clearance between the flat sides  87  of the interior lobes, e.g.,  52 , and the adjacent surfaces of the insert  15 . The clearances c 2  are the clearances between the flat side portions  81  of the exterior lobes, e.g.,  33 , and the adjacent flat portions of the insert  15 . The clearances c 5  and c 6  are the clearances between the diameter of the exterior lobes, e.g.,  33 , and the insert  15 , while c 3  and c 4  are clearances between the diameter of the interior lobes, e.g.,  52 , and the insert  15 . Illustrative values in inches for these clearances for a coupling, in which the outside diameter of the ring is about 14.72 inches, are:  
         [0041]    c 1 =0.030  
         [0042]    c 2 =0.035  
         [0043]    c 3 =0.060  
         [0044]    c 4 =0.060  
         [0045]    c 5 =0.060  
         [0046]    c 6 =0.060  
         [0047]    [0047]FIG. 7 illustrates additional dimensions of interest in an embodiment, according to FIG. 5. In particular, dimension c 8  represents the thickness of that part  65  of the retainer  19  which overlaps the insert  15 . Dimension c 7  represents the clearance range between the opposing faces of the driving and driven hubs  17 ,  13 . The clearance c 6  represents the distance by which the face of the driving hub  17  is set back from the face of the insert  15 . Dimension c 9  represents the clearance between the side face of the insert  15  and the interior edge of the retainer  19 . Dimension c 10  represents the clearance range between the face of the insert and the driven hub  13 . Representative dimensions in inches for an illustrative coupling of the size under discussion are:  
         [0048]    c 6 =0.0200  
         [0049]    c 7 =0.090-0.310  
         [0050]    c 8 =0.5000  
         [0051]    c 9 =0.0200  
         [0052]    c 10 =0.0200-0.2700  
         [0053]    Several observations may be made with respect to operation of the couplings according to various embodiments disclosed herein. First, the flat side surfaces on the interior and exterior lobes facilitate torque transmission. The coupling further provides free axial float, illustrated, for example, by clearance ranges c 7  and c 10  in FIG. 7, as well as relatively wider width W 2  of the insert and relatively wider wings “W 3 ” of the hub, for example, when compared to features of previous couplings such as ATR Sales&#39; “A” or “M” series. In particular applications, the design enables the driving and driven shafts to be positioned at greater distances from one another than previous designs. In such case, for example, greater thermal growth of shafts can be accommodated than in previous systems.  
         [0054]    Such couplings have the further advantage of combining advantageous aspects of both shear and compression couplings. In particular, the coupling operates normally 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. Occasionally, the 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 shear rather than break the associated equipment.  
         [0055]    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.