Patent Publication Number: US-11661973-B2

Title: Flexible reinforced radial spline coupling and method

Description:
FIELD OF THE DISCLOSURE 
     The present disclosure relates to power transmission and, more particularly, to mechanical power transmission using flexible or yielding spline couplings. 
     BACKGROUND 
     Elastomeric couplings for connecting driving and driven mechanical components, typically in the form of rotating shafts are known. Elastomeric couplings are uniquely suited for use in applications where shock, vibration and misalignment may be present. In these types of couplings, driving and driven metal or otherwise stiff hubs are connected on either side of a transmission junction and are connected to one another using an elastomeric or yielding material such as EPDM, natural rubber, Neoprene, Hytrel® and the like. In this way, the yielding material can provide flexing along three axes to accommodate torsional, angular, and parallel misalignment, and also torque spikes and impact drive loads. 
     Conventional elastomeric jaw couplings could meet dynamic life standards for cyclic shock loads or dynamic life standards for accelerated operation life. Elements could meet both standards. As a result high damping applications were limited by the size of the coupling, resulting in consumers required to increase the size of the coupling. High torque applications were susceptible to shock loading passing through the coupling and limiting the life of the customers&#39; driver equipment. 
     Conventional elastomeric jaw and wrap couplings utilize a portfolio of homogeneous elastomeric materials to meet a wide range of industrial applications with a focus on industrial pumping. The elastomer jaw and wrap coupling operate by positive engagement features on the shaft hubs and transmits torque through an elastomeric element between the positive engagement shaft features. Where the shaft hubs connect to the shaft by means of keys, setscrews, or other locking devices. These elastomeric elements are placed in shear and bending, both stresses fatigue the element throughout the operational life, and the torque rating of the coupling is directly correlated to the strength of the homogeneous element material, which is common urethane or natural rubber. The element visually mimics a split spline, where the element is allowed to wrap between the positive engagements features of the shaft hubs. The application which utilize wrap and jaw coupling could require: high load capacity which is achieved with a harder material or high damping capacity which is achieved through a softer material. However, materials which meet each requirement are mutually exclusive. Therefore, the current isotropic materials do not meet high load and high damping simultaneously. As a result, the element portfolio for manufacturers is large and difficult to ensure the right element is integrated into a new application. 
     A few examples of such flexible spline couplings can be seen in U.S. Pat. Nos. 2,867,102 and 2,867,103 (the Williams references), which both issued on Jan. 6, 1959, and describe a flexible coupling for shafts and a gripping arrangement for flexible couplings for power transmission shafts. The types of couplings described in the Williams references are widely used in various industries, but their applications are not without known issues and limitations. 
     One known issue or limitation of known flexible spline couplings is that, during high torque or shock loading situations, the teeth along the outer and inner diameter of the sleeve element deform and roll underneath the opposing teeth of the connected hubs. In extreme conditions, such deformation results in an interruption in torque transmission when the teeth of the flexible element either shear off the element entirely or eject the element from the connected hubs. It has been proposed in the past to increase the stiffness of the elastomeric material such that higher torque loads can be carried. However, such stiffness increases, while possibly better suited to withstand higher torque loads than the baseline stiffness flexible splines, decrease the sleeve&#39;s flexing ability and, therefore, the coupling&#39;s ability to withstand misalignment. 
     BRIEF SUMMARY OF THE DISCLOSURE 
     In one aspect, the present disclosure describes flexible coupling. The flexible coupling includes two hubs, each hub configured to engage a shaft along a central portion and engage flexible spline along an engagement portion. The flexible coupling further includes a flexible member assembly of single or multiple stiffness disposed between the two hubs in engaged relation between the engagement portions of each of the two hubs. The flexible member assembly includes a flexible spline having a first end and a second end, a stiffening cap attached to the first end of the flexible spline between the flexible spline and the engagement portion of one of the two hubs. 
     In another aspect, the present disclosure describes a flexible spline for use with a flexible coupling. The flexible coupling includes two hubs, each hub configured to engage a shaft along a central portion and engage the flexible spline along an engagement portion. The flexible spline further includes a plurality of dowels attached to a first end of the flexible spline. The plurality of dowels is adapted to be disposed between the flexible spline and the engagement portion of one of the two hubs of the flexible coupling. 
     In yet another aspect, the disclosure describes a method for increasing a tooth shear strength without also increasing a torsional rigidity of a flexible spline disposed between two hubs of a flexible coupling for transmitting mechanical motion between two shafts. The method includes aligning and attaching a stiffening cap to a first end of the flexible spline between the flexible spline and an engagement portion of one of the two hubs. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG.  1    is an exploded view of a flexible spline coupling in accordance with an embodiment of the disclosure. 
         FIG.  2    is a cross sectional view of an assembled flexible spline coupling in accordance with an embodiment of the disclosure. 
         FIG.  3 A  is a perspective view of a flexible spline in accordance with an embodiment of the disclosure. 
         FIG.  3 B  is a perspective view of an assembly of the flexible spline in accordance with the embodiment of  FIG.  3 A . 
         FIG.  4 A  is a perspective view of a flexible spline in accordance with an alternative embodiment of the disclosure. 
         FIG.  4 B  is a perspective view of a tooth support cap of the flexible spline of  FIG.  4 A . 
         FIG.  5 A  is a perspective view of a flexible spline in accordance with an alternative embodiment of the disclosure. 
         FIG.  5 B  is a perspective view of a tooth support cap of the flexible spline of  FIG.  5 A . 
         FIG.  6    is a perspective view of a segmented tooth support cap of a flexible spline in accordance with an alternative embodiment of the disclosure. 
         FIG.  7    is an exploded view of a flexible coupling in accordance with another embodiment of the disclosure. 
         FIG.  8    is a cross sectional view of the flexible coupling in accordance with the embodiment of  FIG.  7   . 
         FIG.  9    is a perspective view of the flexible member assembly in accordance with the embodiment of  FIG.  7   . 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure is directed to flexible spline couplings and, more particularly, to systems and methods for improving the couplings&#39; ability to withstand torque loading variations without compromising their ability to handle misalignment during operation. Stated differently, the flexible couplings exhibit an improved resistance to torsional shear without also increasing their torsional rigidity. In the disclosed embodiments, structures are introduced to stiffen each tooth at either end of the coupling spline or sleeve, along both the inner and outer diameters of the sleeve, by inserting and bonding or otherwise attaching a stud or dowel extending through a portion of each tooth, and/or by encapsulating the teeth in boding relation to a liner. The studs or liners advantageously support the teeth and prevent excessive deformation, which allows for high torque transmission, without impacting the misalignment capabilities or the torsional stiffness of the sleeve coupling element. The increased torque capacity advantageously provides an opportunity to downsize the coupling size for a particular application, which can result in a cost savings for the integrator. 
     The present disclosure allows for consolidation within the product offering, provides damping to high torque applications, provides higher torque rating for damping applications, and extends the number of potential applications the wrap and jaw coupling can be integrated into, while retro-fitting into current coupling install base. 
     The present disclosure also provides higher torque applications and increased damping and provides high damping applications higher torque rated couplings, and the opportunity to decrease the size of the coupling, by integrating a stronger material at the core of a softer material element. This decrease in size reduces the overall cost of the complete coupling. The reinforcement carries the load of the element while the softer material elastically deforms and resists the shock loading from passing through the coupling. 
     By reinforcing the core of a soft element with a stiffer material the element can meet higher torque ratings while maintaining damping characteristics of soft materials. While this is achieved through creating anisotropic properties to allow stronger and damping to no longer be mutually exclusive it is a result of the size, shape, location, and material of the core. 
     Previously proposed solutions to increasing torque transmission capacity of a coupling having a given size involve changing the base rubber formulation of the flexible spline to an overall stiffer formulation. However, the increased stiffness of the sleeve or spline has been found to inversely effect misalignment capacity, installation time, and torsional damping characteristics of the coupling. Additionally, stiffer sleeves have been found to increase the resultant load on the driven and driving equipment resulting in reduced equipment life. 
     A perspective view of a flexible coupling  100  in accordance with the disclosure is shown in  FIG.  1    in an exploded state, and in an assembled state in  FIG.  2    to illustrate certain internal structures thereof. 
     Referring now to  FIG.  1   , there is an exploded view of a flexible spline coupling  100  in accordance with an embodiment of the disclosure. The coupling  100  includes two hubs  102 , each having a central portion  104  configured to engage a shaft (not shown) and an engagement portion  106  that is configured to engage toothed ends of a flexible member assembly  108 . In the illustrated embodiment, the engagement portion  106  of each hub  102  includes a row of teeth  110  radially disposed with one another with respect to a longitudinal axis, L 1 , L 2 . The rows of teeth  110  meshably engage corresponding rows of teeth  112 , respectively, formed at either axial end of a flexible spline member  114  included in the flexible member assembly  108 . As shown in  FIG.  3 A , the flexible spline  114  may have an overall width, M, in the axial direction. In certain embodiments, the flexible member assembly  108  may be configured to have single or multiple stiffness depending on its operational usage. 
     Installed in the typical fashion, each hub  102  is installed close to an end of a shaft (not shown) through an axial opening  120  extending through the central portion  104  of the hub  102 . In alternative embodiments, spacer hubs may also be used (not shown here) in the known fashion to mount the flexible coupling. In the illustrated embodiment, member assembly  108  may include a key slot  122  having a setscrew (not shown) disposed in a bore extending through a wrap portion  125  configured to secure the member assembly  108  about teeth  110  of hubs  102 . In certain embodiments, the wrap portion  125  may be made of metal. In other embodiments the wrap portion  125  may be optional with member assembly  108  being configured as a unitary member or piece. The two shafts onto which the hubs  102  are mounted may be two sides of a drive arrangement, for example, between a driving component such as a motor and a driven component such as a pump, drive shaft, conveyor and the like. As is the often the case, the torque transmitted through the coupling  100  may include transient disturbances such as torque spikes, vibrations and the like. Moreover, there may be a misalignment between the two shafts such that an axis L 1  ( FIG.  1   ) extending through one hub  102  may be misaligned and/or non-parallel with an axis L 2  extending through the mating hub  102 . The transient effects in the transmitted torque may be absorbed or otherwise dampened by the elastomeric or resilient material from which the flexible spline  114  is made. The flexible spline  114  can also flex and conform to the misalignment between the axes L 1  and L 2 . 
     In this embodiment, the individual dowels  126  may be assembled, adhered, press fitted or similar, into corresponding bores  134  in the row of teeth  112 . In such an embodiment, a set of dowels such as those shown in  FIG.  3 A  or  FIG.  3 B  would be loosely provided and inserted, one dowel into each corresponding bore. 
     Referring now to  FIG.  2   , there is a cross sectional view of an assembled flexible spline coupling  100  in accordance with an embodiment of the disclosure. The member assembly  108  disposed between hubs  102  is shown with dowels  126  connected to plate  137  and disposed within teeth  112  of member assembly  108  and proximal teeth  110  of hubs  102 . In certain embodiments, the plurality of dowels  126  may be configured to reinforce teeth  112  against torque and shear forces created between the driven hub  102  and the drive hub  102  during use. 
     To increase the ability of the flexible spline  114  to transfer torque while maintain its flexibility and, thus, its ability to conform to misaligned axes, a tooth support or stiffening cap  136  is used in the embodiment shown in  FIG.  2   , and also in  FIGS.  4 A,  4 B, and  5   . A disassembled view of the flexible spline  114  and the tooth support cap  136  is also shown in  FIGS.  4 A and  4 B . In reference to these figures, the tooth support cap  136  includes a plate  137  having a generally annular shape that includes an inner periphery at  112 ′ and  128 ′ and an outer periphery at  137  ( FIG.  4 B ). A plurality of dowels  126  is integrally formed or otherwise connected to the plate  137 . The plurality of dowels  126  are connected at one end to the plate  137  and extend symmetrically around the plate adjacent the outer periphery at  137 . 
     Referring now to  FIGS.  3 A and  3 B , there is a perspective view of a flexible spline  108  in accordance with an embodiment of the disclosure and a perspective view of an assembly of the flexible spline, respectively. As can be seen in  FIGS.  3 A and  3 B , the plurality of dowels  126  extend parallel to one another and have generally the same length in the exemplary embodiment shown. Further, the plurality of dowels  126  extend parallel to a longitudinal axis, L, as shown. As can be appreciated, however, the dowels  126  may have different lengths. For example, the dowels  126  may be longer and extend deeper into the flexible coupling adjacent the inner periphery at  112  and  128 . In this embodiment, the dowels have a circular cross section that results in a cylindrical shape for each dowel. In certain embodiments, the plurality of dowels  126  are also connected on the same side of the plate  137  as shown in  FIG.  4 B . When the tooth support cap  136  is installed onto one end of the flexible spline  114 , for example, the end shown in  FIG.  4 B , the dowels  126  are inserted into openings or bores  134  extending through the axial length of the corresponding inner and outer rows of teeth until the plate  137  is flush with an end face of the flexible spline  114 . In some embodiments, the teeth  112  and dowels  126  align along a diameter, D, of the flexible spline  114 . It is noted that the term “dowel” does not indicate a shape for the structures described, which can have circular and non-circular cross sections, as will be described for alternative embodiments later. 
     As can be seen in  FIG.  3 A , each tooth  112  forms a bore  134 . In this embodiment, the bore  134  has a circular cross section. The radial location of the bore  134  is offset from the outer periphery at  114  and extends in an axial direction, i.e., parallel to the longitudinal axis L, through each tooth  112 . The bore  134  can be placed close to the geometrical center of the tooth  112  such that a first inclined face  111  and a second inclined face  113  extend tangentially to the bore  134  but at an offset distance, dl, therefrom, and the peak at  112  is radially aligned with a center point of the bore  134 . 
     The shape of the plate  137  and, specifically, the inner and outer peripheries are arranged to match the shape of the inner and outer peripheries  132  of the flexible spline  114 . Moreover, the number and placement of the first plurality of dowels  126 , and also the diameter of each dowels  208 , is selected to match the arrangement, placement and size of the bores  134  formed in the outer plurality of teeth  114 . 
     When installing the tooth support cap  136  onto the end face  139 , a layer of adhesive at  139  may be spread over the face of the plate  137  and also along the lateral surfaces of the pluralities of dowels  138  before the cap  136  is installed onto the end face  139 . When the cap  136  is in an installed position onto the end face  139 , the side of the plate  137  from which the dowels  138  extend is flush or abuts onto the end face  139 , and the dowels  138  extend through the corresponding teeth  112 . In the embodiment shown in  FIG.  4 A , for example, the dowels  138  are flush with end openings in the teeth  112 . 
     In certain embodiments, an overmolding process may be used to incorporate two different materials, for example, the plurality of dowels  138  into teeth  112  to capture the dowels  138  inside of teeth  112  without having to use adhesives or the like. Overmolding may completely cover the reinforcement to protect the reinforcement during operation. 
     In  FIG.  3 B , an embodiment illustrates an assembly of inserting the plurality of dowels  126  into bores  134  disposed within teeth  112  to create a reinforced structure for teeth  112  to resist shear and torque forces during use. 
     Referring now to  FIG.  4 A , there is a perspective view of a flexible spline  114  in accordance with an alternative embodiment of the disclosure. In this embodiment, a plurality of dowels  138  comprise a polygonal shape, such as, a trapezoidal form in cross section. Further, dowels  138  also may be configured to extend parallel to the longitudinal axis, L, as shown. In some embodiments, the dowels  138  are inserted as a portion of the tooth support cap  136  with dowels  138  configured to be integral with and connected to end support plate  137 . In certain embodiments, plate  137  is formed to be congruent to match and correspond to the circumferential shape of flexible spline  114  when dowels  138  are inserted into flexible spline  114  and plate  137  abuts a first end of flexible spline  114 , as shown in  FIG.  4 A . 
       FIG.  4 B  is a perspective view of a tooth support cap  136  of the flexible spline  114  of  FIG.  4 A . In certain embodiments, the tooth support cap  136  comprises an end support plate  137  as described above and a plurality of dowels  138 ′ connected and integral thereto. Support plate  137  may include surfaces  112 ′ congruent to the inner circumference of teeth  112  and may include surfaces  128 ′ congruent to the inner circumference of tooth gap  128 . In some embodiments, support plate  137  may include surfaces  122 ′ congruent to the outer circumference and aligning to the positioning of key slots  122 , as shown. End support plate  137  may comprise a metal, a ceramic or other hardened or stiff material to reinforce teeth  112 . 
     In certain embodiments, dowels  138  may include a first side face  140   a , a second side face  140   b  disposed opposite the first side face  140   a , an inner face  142   a  and an outer face  142   b  with the inner face  142   a  proximal the inner circumference of flexible spline  114  and the outer face  142   b  proximal the outer circumference of flexible spline  114 . 
     Referring now to  FIG.  5 A , there is a perspective view of a flexible spline  114  in accordance with an alternative embodiment of the disclosure. In this embodiment, a plurality of dowels  138 ′ having an I-beam polygonal cross section are disposed within similarly shaped bores in the flexible spline  114 . As can be appreciated, I-beams are known for their substantial resistance to shear, bending and torque forces in construction and the like. In certain embodiments, the dowels  138 ′ are disposed circumferentially about the flexible spline  114  with their cross sections radially spaced equidistant about a longitudinal axis, L, within teeth  112 . Dowels  138 ′ are disposed within teeth  112  with the I-beam cross section having a narrow portion of the cross section disposed in a central portion of the teeth  112  and two wider portions of the cross section disposed proximal each side portion of the teeth  112  to provide maximum resistance or reinforcement to shear, bending and torque forces. 
       FIG.  5 B  is a perspective view of a tooth support cap  136  of the flexible spline  114  of  FIG.  5 A . In certain embodiments, the tooth support cap  136  comprises an end support plate  137  as described above and a plurality of dowels  138 ′ connected and integral thereto. Support plate  137  may include surfaces  112 ′ congruent to the inner circumference of teeth  112  and may include surfaces  128 ′ congruent to the inner circumference of tooth gap  128 . In some embodiments, support plate  137  may include surfaces  122 ′ congruent to the outer circumference and aligning to the positioning of key slots  122 , as shown. End support plate  137  may comprise a metal, plastic, high stiffness elastomer, ceramic or other hardened or stiff material to reinforce teeth  112 . 
     In certain embodiments, the dowels  138 ′ are integral and connected to end support plate  137  as described above with respect to dowels  138  in  FIGS.  4 A and  4 B . 
     An alternative embodiment for the flexible spline  114  and tooth support cap  136  is shown in  FIGS.  4 A and  5 A . In these figures, structures and features that are the same or similar to corresponding structures and features described previously are denoted and referred to by the same reference numerals as previously used for sake of description. 
     In this embodiment, it can be seen that the shape of the dowels  138  and  138 ′ is non-circular in cross section. It should be noted that the shape of the dowels is contemplated to have any appropriate shape, for example, triangular as shown here but also other shapes, including but not limited to semi-circular, C-shaped, Y-shaped, T-shaped, X-shaped, I-shaped, V-shaped, star shaped, rectangular, hexagonal, pentagonal, wave-shaped, and others. Shape selection may depend on various factors including the desired contact area between the dowels and their bores, the material of the dowels, the material of the flexible spline, the amount and type of adhesive used between the dowels and their corresponding bores, the manufacturing method used to construct the cap, and others. The cap may be constructed by any sufficiently rigid material including a thermoplastic material, nylon (including glass-filled nylon), metal, fiberglass composites, high durometer elastomers, and the like. 
     While various features in the embodiment shown in  FIGS.  4 A and  5 A  are similar to the embodiment shown in  FIGS.  3 A and  3 B  with respect to the general arrangement of components, it can be seen that here the shape of the dowels  138  and  138 ′ is polygonal rather than circular. Consequently, the bores  134  also have a polygonal shape that mates with the shape of the dowels  138  and  138 ′. Because of this difference, a different type of support may be lent by the dowels to the outer and inner peripheries of the flexible spline  114  and the end face  139 . More specifically, where a tangential relationship exists between the inclined surfaces  111  and  113  and the outer surface of the dowels  138  and  138 ′ having a minimum thickness dl in the embodiment shown in  FIG.  4 A , the polygonal dowels  138  and  138 ′ of the embodiment shown in  FIGS.  4 A and  5 A  includes an orientation of the dowels in side faces  140   a ,  140   b  of the dowels  138  and  138 ′ are orientated to be generally parallel with the inclined side faces  111  and  113  of the teeth  112 . The distance dl thus denote a layer of flexible material that has a uniform thickness over each side face  140   a ,  140   b  and provides a more reliable cushioning effect that, in certain applications, may avoid possible pinch points in embodiments with a non-uniform bore wall thickness between the dowel and an exterior surface of the tooth. In this embodiment, the third face  142   a  of each dowel  138  or  138 ′ lies generally tangentially relative to an end-face  127 . 
     As can be appreciated, a range of different spans of the cap  136  can be used anywhere between a single pair of dowels to a full set of dowels extending around the entire end face, as shown in  FIG.  4 B . The different spans can be used to cover the entire face of a solid flexible coupling, and also alternative types of couplings that are commonly used including a split coupling having a slit on one side, or a fully split coupling having slits on both sides such that the coupling is formed by two semi-cylindrical pieces assembled together to form a full cylindrical coupling. The cap as shown in  FIG.  4 B  would thus occupy half the bores  134  and would be mounted adjacent a mating pair cap to occupy and cover the remaining bores. Other span angles may also be used. It is also noted that the inner periphery  132  of the embodiments for the caps  136  shown in  FIG.  4 B  may alternatively be formed to be smooth, and the inner row of dowels  138  may be omitted such that the caps may be installed from the opposite direction shown in  FIG.  4 A  to occupy the bores  134  in the row of teeth  112 . In the embodiment of  FIGS.  7 - 9   , two opposed plates  137 , appropriately sized, are connected at least to the row of dowels  138  such that both axial faces of the teeth  112  on each side of the flexible spline  114  are faced by the plates  137 . 
     Referring now to  FIG.  6   , there is a perspective view of a segmented tooth support cap  137 ′ of a flexible spline  114  in accordance with an alternative embodiment of the disclosure. In this embodiment, the tooth segmented support cap or plate  137 ′ is configured to be congruent to the inner and outer circumference of flexible spline  114  and includes a plurality of plate segments  137 ′ as shown in  FIG.  6   . In certain embodiments, the plurality of plate segments  137 ′ may provide easier dowel  138 ′ insertion into teeth  112  of flexible spline  114  when an application or use requires an enlarged sized flexible spline  114 . For example, in an application where assembly of the flexible member assembly  108  would make insertion of the dowels  138  or  138 ′ difficult or burdensome as a larger single unit, it is more efficient and cost effective to use a plurality of smaller plate segments  137 ′ during assembly thereof. 
     Use of any of the dowels  126 ,  138  or  138 ′ described herein to stiffen the teeth formed on the axial ends of a flexible spline  114 , which meshably engage with hubs  102  disposed on shafts (not shown), has proven to considerably increase the torque capacity of the flexible coupling  100  (reinforced element) as compared to a baseline coupling, i.e., a coupling with no dowels disposed on the ends of the flexible coupling  100 . To quantify this torque capability increase in exemplary implementations, certain experiments were performed. The purpose of the experiments was to quantify the torsional stiffness and the increased performance of different varieties of stiffening caps in accordance with the disclosure as compared to a baseline coupling. A D-flex® coupling was used as a baseline and also modified for the testing. One of the metrics examined were increases in terms of torque required to shear the teeth of the flexible spline being tested. The scope of the test conducted on the baseline and improved couplings was to statically test the improved coupling designs to identify torsional stiffness, quantify tooth shear strength, and baseline them against the baseline design, which did not include any stiffening structures in the teeth. 
     In order to validate the benefit of adding a reinforcing elements or dowels  126 ,  138 ,  138 ′ to a flexible sleeve member or spline coupling  114 , a reinforced wrap element was dynamically tested alongside the same size homogenous material coupling. The reinforced coupling exhibited a 40% increase in useable life when compared to the homogenous material coupling. 
     Based on testing outlined above, reinforcing the element from bending improves the useable life of the wrap coupling design. 
     Further, testing illustrates that tooth reinforcements have the potential to increase the torque capacity of sleeve coupling elements without impacting the torsional stiffness or the formulation of the base rubber compound, as the base rubber was the same between samples. Additionally, these tooth reinforcements could be any material that has a substantially higher durometer/stiffness than the base rubber material. Urethane, plastics, rubber, or other metals could be used. Further consideration should be given in terms of the actual shape of the reinforcement in addition to circular shapes, which were the only shapes tested. A geometric shape that mimics the profile of the tooth, such as the embodiment shown in  FIG.  5 A , may further provide reinforcement in higher torque situations. 
     The elastomeric reinforced spline uses the increased modulus of elasticity of stronger materials and geometry of the reinforcement to increase the area moment of inertia to resist the shear stress and bending stress within the element. Both features decrease in bending stress increases the fatigue life of the material. The cross section of the reinforcement may be an “I beam”, circle, ellipse, polygon, or the like, and the location of the reinforcement of the element is placed in the center element spline to provide maximum impact. The material may be metallic, nonmetallic, composite, or a combination of materials. By bonding the reinforcement within a softer elastomeric element, by vulcanized, cold bonding or interference fit, the element dampens shock loading by utilizing a lower modulus of elasticity. The softer material may be a thermoset or thermoplastic. The element shape utilizes the current split splined design, allowing for the element to install over current shaft hub without moving the hubs. Each reinforcement on the element may be separate or joined along the face of the coupling for ease of assembly. 
     All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein. 
     The use of the terms “a” and “an” and “the” and “at least one” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The use of the term “at least one” followed by a list of one or more items (for example, “at least one of A and B”) is to be construed to mean one item selected from the listed items (A or B) or any combination of two or more of the listed items (A and B), unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. 
     Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. 
     Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.