Patent Publication Number: US-2006009297-A1

Title: Flexible coupling having a center with opposing re-entrant folds

Description:
CROSS REFERENCES TO RELATED APPLICATIONS  
      Not Applicable  
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH  
      Not Applicable  
     BACKGROUND OF THE INVENTION  
      This invention relates to flexible shaft couplings, and more particularly, to composite flexible couplings for transmitting torque between two shafts approximately aligned on a shaft axis, i.e., to flexible couplings joining a pair of axially spaced shafts. Flexible diaphragm couplings comprising a pair of shoes joined by a generally U-shaped flexible center element, such as disclosed in U.S. Pat. Nos. 4,634,400; 6,080,065; 6,117,015; 6,196,926; and 6,257,985, all issued to the assignee of the present application, can accommodate axial misalignments (i.e. the spacing between the shafts is not optimum per coupling design) and angular misalignments (i.e. the shaft axes intersect at a point) without large stresses by using a bellows actions. U.S. Pat. Nos. 4,634,400; 6,080,065; 6,117,015; 6,196,926; and 6,257,985 are all fully incorporated herein by reference.  
      These known couplings, however, have difficulty accommodating lateral misalignment (i.e. the shaft axes do not intersect and are not coaxial). One known method for coupling laterally misaligned shafts is to provide a flexible diaphragm coupling having an oversized flexible center element that can accommodate the bellows action in orthogonal directions. Unfortunately, the oversized flexible center element increases the coupling mass which increases the loads and forces on the hub attachment assembly. Moreover, the large flexible element can decrease the torsional stiffness of the coupling and increase wind up deformation. Accordingly, a need exists for an improved coupling which can accommodate axial, lateral, and angular shaft misalignments.  
     SUMMARY OF THE INVENTION  
      The present invention provides a flexible coupling for transmitting torque between two shafts approximately aligned on a shaft axis, and a method of making the novel coupling. The coupling can accommodate axial, lateral, and angular shaft misalignments without the problems associated with prior art couplings. One embodiment of a flexible coupling incorporating the present invention includes an arcuate flexible center element having two axially spaced radially extending leg portions joined by an axially extending bridging portion. The axially extending bridging portion has at least two opposing re-entrant folds defining a T-shaped cross-section in a radial plane extending from and along the shaft axis.  
      A general objective of the present invention is to provide a flexible coupling that can accommodate axial, lateral, and angular shaft misalignments without the problems associated with prior art diaphragm couplings. This objective is accomplished by providing a coupling having a center element including a bridging portion with at least two opposing re-entrant folds defining a T-shaped cross-section in a radial plane extending from and along the shaft axis.  
      The foregoing and other objects and advantages of the invention will appear from the following description. In the description, reference is made to the accompanying drawings which form a part hereof, and in which there is shown by way of illustration a preferred embodiment of the invention.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a perspective view of one embodiment of a portion of a coupling incorporating various of the features of the invention, which view is taken from the inside of the coupling;  
       FIG. 2  is an elevational view of the inside of the couplings shown in  FIG. 1 ;  
       FIG. 3  is a partially broken away and sectioned axial side view of the entire coupling shown in  FIG. 1 , with one half thereof shown in dotted outline;  
       FIG. 4  is a perspective view of the center element of  FIG. 1 ;  
       FIG. 5  is a fragmentary view of a second embodiment of a coupling incorporating various of the features of the invention;  
       FIG. 6  is a perspective view of a third embodiment of a portion of a coupling incorporating various of the features of the invention, which view is taken from the inside of the coupling;  
       FIG. 7  is an elevational view of the inside of the couplings shown in  FIG. 6 ;  
       FIG. 8  is a partially broken away and sectioned axial side view of the entire coupling shown in  FIG. 6 , with one half thereof shown in dotted outline; and  
       FIG. 9  is a cross-sectional axial side view of the coupling shown in  FIG. 6  in a mold during manufacture. 
    
    
      Before one embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of the construction and the arrangements of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.  
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
      A composite flexible diaphragm coupling  11  for transmitting torque between first and second axially spaced and oppositely extending shafts  13  and  15  which are approximately aligned on a shaft axis  17  is shown in  FIG. 1-3 . The coupling  11  comprises first and second angularly spaced composite flexible arcuate members  21  and  23  ( FIG. 3 ) which are of generally identical construction, and respectively extend for approximately 180 degrees around a coupling axis  35 . The arcuate members include first and second oppositely extending arcuate shoes  31  and  33  which are joined by an arcuate flexible T-shaped center element  41 .  
      Because the first and second composite members  21  and  23  are generally identically constructed, only the first composite member  21  will be described in detail. More specifically, the first and second shoes  31  and  33  are also of generally identical construction and each arcuately extends for an arcuate distance which can be almost 180 degrees. In addition, the first and second shoes  31  and  33  extend axially in opposite directions to each other. More particularly, the first and second shoes  31  and  33  each include an inner part  51  which is bonded to the central element  41 , and an outer part  53  which extends from the inner part  51  and which is adapted, in any suitable way, to be connected to an associated one of the oppositely extending shafts  13  and  15 . In the particularly illustrated construction, the outer parts  53  each include one or more apertures  55  which permit the shoes  31  and  33  to be fixed by bolts  30  to generally cylindrical hubs  32 . The hubs  32  include central bores  34  housing the shafts  13  and  15 .  
      The shoes  31  and  33  can take any number of suitable configurations and, in the disclosed construction, the inner and outer parts  51  and  53  are preferably of generally semi-cylindrical configuration. In addition, the shoes  31  and  33  can be fabricated of any suitable metallic or plastic material and, in the disclosed construction, are preferably fabricated of suitable plastic material.  
      The center element  41  is formed from a composite sheet material, and includes first and second leg portions  61  and  63  which are generally identically constructed and which are axially spaced from each other and joined by a bridging portion  65 . The sheet material is preferably a glass fiber fabric impregnated with a vinyl ester resin, however any flexible material, such as a urethane material, can be used without departing from the scope of the invention. The leg portions  61 ,  63  and bridging portion  65  extend arcuately for an arcuate distance which is approximately 180 degrees.  
      Referring to  FIGS. 1-4 , the bridging portion  65  includes a pair of centrally located, opposing, outward, re-entrant folds  67 ,  69 . Each fold  67 ,  69  is joined to one of the leg portions  61 ,  63  by a radially extending base portion  77 ,  79  to define a generally T-shaped cross-section in a radial plane extending from and along the shaft axis  17  or coupling axis  35 , wherein the T-shaped cross-section has a radially extending stem  81  with a top  83  substantially perpendicular to the stem  81 . Although only one pair of opposing, outward, re-entrant folds is shown, more than one pair of opposing, outward, re-entrant folds can be provided without departing from the scope of the invention.  
      Advantageously, the bridging portion  65  including at least one pair of centrally located, opposing, outward, re-entrant folds  67 ,  69  which defines the T-shaped cross-section accommodates axial, lateral, and angular misalignments without the accompanying increase of coupling mass, loads and forces on the shafts, and wind up deformation, associated with prior art U-shaped cross-section center elements. Moreover, the center element  41  including the bridging portion  65  having the T-shaped cross-section provides a coupling with a diameter that is smaller than a prior art coupling sized for the same torque loads and misalignments.  
      The leg portions  61  and  63  each include a radially inner part  71  bonded to the cylindrical portion of the associated one of the shoes  31  and  33 . The inner parts  71 , respectively, include oppositely facing, arcuately extending recesses  75  which receive, and are bonded to, the inner parts  51  of the associated shoes  31  and  33 . Any suitable method for bonding the shoes  31  and  33  to the inner parts  71  can be employed.  
       FIG. 5  is another embodiment of a coupling  211  which is of generally the same construction as that shown in  FIGS. 1-3 , except that the outer parts  253  of the shoes  231 ,  233  extend radially for engaging the shafts  13 ,  15  or hub  32 .  
      In  FIG. 6-8 , a preferred embodiment of a flexible diaphragm coupling  111  for transmitting torque between first and second axially spaced and oppositely extending shafts  113  and  115  which are approximately aligned on a shaft axis  117  is shown. The coupling  111  comprises first and second angularly spaced flexible arcuate members  121  and  123  ( FIG. 8 ) which are of generally identical construction, and respectively extend for approximately 180 degrees around a coupling axis  135 .  
      Each arcuate members  121 ,  123  is preferably formed from a suitable material as a single piece. The material is preferably a glass fiber fabric impregnated with a vinyl ester resin, however, as in the above described embodiments, any flexible material, such as polyether urethane, can be used without departing from the scope of the invention. Because the first and second arcuate members  121  and  123  are generally identically constructed, only the first arcuate member  121  will be described in detail.  
      The arcuate member  121  including an arcuate flexible T-shaped center element  141  having integral shoes  131 ,  133 . The T-shaped center element  141  includes first and second leg portions  161 ,  163  joined by a bridging portion  165 . The bridging portion  165  includes a pair of centrally located, opposing, outward, re-entrant folds  167 ,  169 . Each fold  167 ,  169  is joined to one of the leg portions  161 ,  163  by a radially extending base portion  177 ,  179  to define a generally T-shaped cross-section in a radial plane extending from and along the shaft axis  117 , wherein the T-shape has a radially extending stem  181  with a top  183  substantially perpendicular to the stem  181 . As in the first embodiment, although only one pair of opposing, outward, re-entrant folds is shown, more than one pair of opposing, outward, re-entrant folds can be provided without departing from the scope of the invention.  
      Advantageously, as in the first embodiment, the T-shaped cross-section accommodates axial, lateral, and angular misalignments without the accompanying increase of coupling mass, loads and forces on the shafts, and wind up deformation, associated with prior art U-shaped cross-section center elements. Moreover, the center element  141  including the bridging portion  165  having the T-shaped cross-section provides a coupling with a diameter that is smaller than a prior art coupling sized for the same torque loads and misalignments.  
      The first and second leg portions  161 ,  163  extend in axially opposite directions from the bridging portion  165 . Outer parts  162 ,  164  of the first and second leg portions  161 ,  163  form the integral shoes  131 ,  133  formed of the same material as the center element  141 . The shoes  131 ,  133  are generally identically constructed and axially spaced from each other. Preferably, the shoes  131 ,  133  have a material thickness greater than the thickness of the material forming the bridging portion  165  to increase the shear strength of each shoe  131 ,  133 . The additional thickness can be formed by applying additional material forming the shoes  131 ,  133  over the outer parts  162 ,  164  of the first and second leg portions  161 ,  163 , or a different material, such as metal, an elastomer, and the like, can be embedded in, bonded to, or mechanically fastened to, to the outer parts  162 ,  164  of the first and second leg portions  161 ,  163  forming the shoe  131 ,  133 .  
      Apertures  155  formed through shoes  131  and  133  receive bolts  130  which fix the coupling  111  to the shafts  113 ,  115 . The bolts  130  pass through the apertures  155  and threadably engage hubs  132  fixed to the shafts  113 ,  115  to fix the coupling  111  to the shafts  113 ,  115 . Of course, other methods for fixing the coupling to the shafts can be used, such as pinning (i.e. using pins extending through the coupling into the shafts), bonding (i.e. adhesives and other chemical fasteners), mechanically interlocking the coupling with the shafts, and the like, without departing from the scope of the invention. Grommets can be fixed in the apertures  155  to strengthen the aperture peripheries.  
      Referring now to  FIGS. 7 and 9 , the coupling  111  is preferably made by a resin transfer molding process. In particular, in a preferred method of making the coupling  111 , the coupling  111  is formed by slipping a cylindrical sleeve  185  or laying a sheet of glass fiber fabric over a cylindrical mandrel  187  having a radially extending T-shaped form  189 . Although a cylindrical sleeve of glass fiber fabric is preferred, the sheet material can be formed by winding fibers around the mandrel without departing from the scope of the invention. Advantageously, the cylindrical sleeve  185  conforms to the shape of the mandrel  187  including the radially extending T-shaped form  189 . Additional layers  191  of the same or different material, such as additional cylindrical sleeves of fabric, sheets of fabric, fiber windings, metal rings, and the like can be placed over the sleeve  185  on opposite axial sides of the T-shaped form  189  to build up the integral shoes  131 ,  133 , such that the shoes  131 ,  133  are more rigid than the center element  141  for withstanding the shear forces exerted on the shoes  131 ,  133  by the shafts  113 ,  115 . Of course, additional material can also be applied over the T-shaped form  189  to increase the thickness of the center element  141 , if desired.  
      Once the material forming the coupling is applied onto the mandrel  187 , molds  193 ,  195  axially slipped onto the mandrel  187  from opposing sides of the T-shape form  189  encloses the material applied to the mandrel  187  and T-shaped form  189 , and urges the material to conform to the shape of the mandrel  187  and T-shape form  189 . Resin, such as a vinyl ester resin, is injected into the mold to impregnate the glass fiber material and any other impregnable material forming part of the coupling  111 , as is known in the art. The resin impregnated material is then cured, and cut axially along a plane intersecting the coupling axis to form the two arcuate members  121 ,  123 . Advantageously, the center element  141  wrapped around the T-shaped form  189  is flexible to allow the removal of the arcuate members  121 ,  123  from the mandrel  187  and T-shaped form  189 . Of course, the above method can used to make the flexible center element  41  of the first embodiments shown in  FIGS. 1-5 , and the shoes can be fixed to the center element during the application of the material to the mandrel, upon curing, or subsequent to removal of the center element from the mandrel.  
      While there has been shown and described what are at present considered the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention defined by the appended claims. Therefore, various alternatives and embodiments are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter regarded as the invention.