Abstract:
A flexible coupling device for transmitting power between at least two adjoining rotary members and allowing axial deflection and/or angular misalignment of at least one rotary member relative to another. The flexible coupling device provides optimization for both bending and torque stress. The flexible coupling device includes at least two annular members where the thinnest point of the flexure portion of at least one of the annular members is spaced radially-inward from the radially-outermost point. Additionally, the components of the device are unitary in structure and may be constructed using cost-efficient manufacturing processes.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention is directed to couplings for connecting rotatable members, and more particularly to flexible couplings that transmit power and accommodate angular and/or axial misalignments between adjoining rotatable members.  
       BACKGROUND OF THE INVENTION  
       [0002]     Drive systems serve as the crux of many industrial machines. In order to be commercially efficient, it is important that these drive systems not only operate effectively, but that their subsystems and individual parts do so at an efficient cost. Drive systems often include power transmission couplings. Typically, power transmission couplings transmit power from an engine to a gearbox or from a rotatable driving shaft to a rotatable driven shaft. These shafts are often angularly misaligned, axially misaligned, or both. As a result, power transmission couplings are critical components in industrial applications, especially transportation applications such as the drive systems of fixed-wing and rotary-wing aircraft. These applications involve both high torque and high bending stress requirements. In addition to satisfying these requirements, it is also advantageous that these couplings are inexpensive to manufacture.  
         [0003]     Flexible transmission couplings are commonly used in these applications. Typical flexible couplings include a flexible diaphragm member with a wall thickness that decreases with increasing radial distance from the center. Because torque transmitting capacity varies inversely with the square of the radius of the diaphragm, the purpose of this profile is to maintain constant shear stress throughout the thickness of the diaphragm member so that the weight of the device may be minimized.  
         [0004]     In order to produce this profile, a typical diaphragm member is manufactured with contours produced on both sides of the member. The contours may be created using electro-chemical machining, which is helpful in allowing two neighboring annular members of a diaphragm to be formed with a cavity therebetween defined by the contours. To produce the flexible coupling, the diaphragm members may be joined to each other or to appropriate flanges, fittings, or tubes by means of electron beam welding. However, these processes are costly and time consuming. Additionally, because the bending stresses increase as the radius increases, a wall thickness profile that maintains constant shear stress throughout the thickness of the diaphragm member does not optimize the bending stresses of the flexible coupling.  
         [0005]     Thus, there remains a need for a commercially efficient coupling device for use in transmitting power between rotary members that are axially and/or angularly misaligned. The device should be constructed of unitary parts and should be able to be optimized for the high torque and bending requirements of power transmission between members. The device should also use cost-efficient manufacturing processes, thus resulting in a simplified, less expensive flexible coupling.  
       BRIEF SUMMARY OF THE INVENTION  
       [0006]     The present invention addresses the above needs and achieves other advantages by providing a simplified flexible coupling device for transmitting power between at least two adjoining rotary members and allowing axial deflection and/or angular misalignment of at least one rotary member relative to another. The flexible coupling device provides optimization for both bending and torque stress. The flexible coupling device includes at least two annular members having the thinnest point of the flexure portion of at least one annular member spaced radially-inward from the radially-outermost point. Additionally, the components of the device are unitary in structure and may be constructed using inexpensive manufacturing processes.  
         [0007]     In one embodiment, the present invention includes a hub portion and at least two flexible adjacent annular members extending radially outwardly from the hub portion. The annular members comprise at least one radially-outward connecting portion for connecting each diaphragm to an adjoining diaphragm or rotary member. The annular members also comprise a flexure portion extending radially between the hub portion and the connecting portion of the respective annular member. The flexure portion comprises an outer side and an inner side, and the inner and outer sides of at least one flexure portion define a thickness. The thinnest point of the thickness is spaced radially-inward from the radially-outermost point of the flexure portion. Also, the inner sides of the adjacent annular members of a diaphragm face each other so as to define a flexure space that does not narrow in a radially-outward direction when the annular members are in an unflexed condition.  
         [0008]     In one aspect, the thinnest points of adjacent flexure portions are substantially aligned in a radial direction. In another aspect, a continuous curve may define the outer side of at least one flexure portion. The connecting portion may be located at the radially-outermost point of the flexure portion, and the connecting portion may extend axially in one direction and radially outward from the flexure portion  
         [0009]     The present invention also provides a method of manufacture for a unitary diaphragm of a flexible coupling device for transmitting power between at least two adjoining rotary members and allowing axial misalignment of at least one rotary member relative to another. The method of manufacture comprises forming outer sides of flexure portions of at least two annular members that extend radially outwardly from a diaphragm. The method also includes forming a flexure space that does not narrow and that defines inner sides of adjacent annular members, where the inner and outer sides of at least one flexure portion define a thickness for the flexure portion, and the thinnest point of the flexure portion is spaced radially-inward from the radially-outermost point of the flexure portion.  
         [0010]     In one aspect, the method includes forming the unitary diaphragm using conventional manufacturing means. In another aspect, the method includes forming the outer sides of at least one flexure portion so that the outer side is defined by a continuous curve. In another aspect, the method includes forming a connecting portion located at the radially-outermost point of the flexure portion. The method may also include forming a connecting portion that extends axially in one direction and radially outward from the flexure portion.  
         [0011]     The flexible coupling device of the present invention has several advantages that provide a simplified and commercially efficient coupling device for use in transmitting power between rotary members that are axially and/or angularly misaligned. The flexure portions, which include substantially straight inner sides and outer sides that have a first portion and a second portion, advantageously have the thinnest portion of the thickness at a transition point that is radially inside of the outer-most point of the flexure portion. This positioning allows optimization of both the torque and bending stresses. Additionally, the diaphragm is constructed of a unitary part. Although in certain circumstances it may still be advantageous to do so, this obviates the need for electron beam welding of adjacent coupling parts used in conventional coupling devices. Also, the flexure space does not narrow in a radially-outward direction. This allows the machining or forming of the flexure space to be more simplified, and thus less expensive and more commercially efficient. It also advantageously requires contouring of only the outer sides of the flexure portion of the diaphragm. Although conventional methods may be used, this results in the ability to use methods less expensive and time consuming than the conventional electro-chemical machining. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:  
         [0013]      FIG. 1  shows a side view of one embodiment of the present invention having multiple diaphragms and two end connecting members attached to two rotary members;  
         [0014]      FIG. 2  shows a sectional view of the present invention having one diaphragm; and  
         [0015]      FIG. 3  shows a close-up sectional view of the present invention shown in  FIG. 2  on one side of the axis of rotation. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]     The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.  
         [0017]     Generally the present invention in one embodiment includes a flexible coupling device  10  having one or more diaphragms  11 . A flexible coupling device with multiple diaphragms  11  and two end connecting members  15  is shown in  FIG. 1 . Advantageously, the flexible coupling device provides optimization for both bending and torque stress between at least two adjoining rotary members  18 .  
         [0018]     The flexible coupling device  10  is created from bar stock, but may be fabricated in any way, including by forging. It is constructed of a low-alloy steel, such as Inconel, but may also be made of other materials suitable for sustaining the required bending and torque stresses such as such as maraging steel, stainless steel, and titanium alloy. A cross section of diaphragm  11  of the flexible coupling device  10  is shown in  FIGS. 2 and 3 . The diaphragm  11  is generally disk-shaped and has a hub portion  12  and at least two annular members  13 . The hub portion  12  is generally cylindrical in shape with a center axis that is generally co-linear with an axis of rotation  14  of the flexible coupling device  10  when the coupling device is not being flexed. The hub portion  12  includes an inner hub wall  22 , a left hub surface  38 , a right hub surface  39 , and an outer hub wall  23 . The left hub surface  38  and the right hub surface  39  are substantially parallel to each other and generally perpendicular to the axis of rotation  14 . The center of the hub portion  12  is cut out such that an inner hub wall  22  is defined at some distance from the axis of rotation  14  of the flexible coupling device  10  as shown in  FIG. 3 .  
         [0019]     It should be noted that in other embodiments of the present invention a wide range of variations in the structure of the hub portion  12  are possible. For example, the hub portion  12  could be continuous such that no section of the hub portion  12  is cut out, resulting in no inner hub wall  22 . Alternatively, the left hub surface  38  and/or the right hub surface  39  need not be perpendicular to the axis of rotation  14 . For example the left hub surface  38 , the right hub surface  39 , or both the left hub surface  38  and the right hub surface  39  could have positive slopes such that they angle away from each other, or they could have negative slopes such that they angle back toward each other.  
         [0020]     Referring to  FIG. 3 , the annular members  13  extend radially outward from the hub potion  12  and, include a flexure portion  16  and a connecting portion  17 . The flexure portion  16  extends radially outward from the hub portion  12  to a flexure end  29 . The connecting portion  17  is located at the radial end of the flexure portion  16  and extends axially in one direction and radially outward from the flexure end  29  so as to define connecting rings  24 , as shown in  FIGS. 1 and 3 . This shape provides more axial space between adjacent flexure portions than connecting members that extend only radially, which allows more angular misalignment in the coupling device.  
         [0021]     The connecting rings  24  have an outer connecting surface  36  and an inner surface  37 . The outer connecting surface  36  and the inner surface  37  are substantially parallel to each other and are generally perpendicular to the axis of rotation  14 . The outer connecting surfaces  36  of the connecting rings  24  of the annular members  13  are located radially outside of the right hub surface  38  and the left hub surface  39 , respectively. The connecting portion  17  also includes connecting holes  21 . The connecting holes  21  are generally cylindrical in shape and are spaced along the periphery of the connecting rings  24 . The connecting holes  21  extend from the outer connecting surface  36  through the inner surface  37  such that the axes of the connecting holes  21  are generally parallel to the axis of rotation  14 . As shown in  FIG. 1 , the connecting holes  21  permit the use of fasteners, such as rivets, bolts, etc. to connect the diaphragm  11  to an adjoining diaphragm  11  or to end connecting member  15 . The connecting portion  17  also permits connection directly to other rotary members  18 .  
         [0022]     Other embodiments of the flexible coupling device  10  may include multiple diaphragms  11 . For example, a flexible coupling device  10  may comprise several diaphragms  11  adjacent to each other and attached at the connecting portion  17  as shown in  FIG. 1 . Other variations in the structure of the connecting portion  17  are also possible. For example, the outer connecting surface  36  and the inner surface  37  need not be parallel to each other. Also, other means for connecting the connecting portion  17  to adjoining diaphragms  11  or other rotary members  18  are possible, such as welding or brazing.  
         [0023]     Referring to  FIG. 3 , the flexure portions  16  include inner sides  25 , outer sides  26 , and a thickness  27  defined between the inner sides  25  and the outer sides  26 . The outer sides  26  have a first portion  34  of decreasing thickness extending from the hub portion  12  radially outward to a transition point  28 . From the transition point  28 , the outer sides  26  have a second portion  35  of increasing thickness that extends radially outward to the flexure end  29 . The inner sides  25  of the flexure portion  16  are generally perpendicular to the axis of rotation  14  and are substantially straight such that the inner sides  25  of adjacent flexure portions  16  are substantially parallel and are generally perpendicular to the axis of rotation  14 . The resulting transition point  28  defines the thinnest portion of the thickness  27  along the flexure portion  16 .  
         [0024]     Because torque transmitting capacity varies inversely with the square of the radius of the diaphragm, conventional flexible couplings that have the thinnest portion of the diaphragm member at the radially-outermost point from the hub are designed primarily to maintain constant shear stresses radially while minimizing weight. The result is that large bending stresses are created at the thinnest portions because the larger bending moments occur at the radially-outermost points. However, smaller bending moments occur at points that lie in-between the hub and the radially-outermost points. Thus, the flexible coupling device  10  of the present invention places the thinnest point of the flexure portion  16  at a point of lower bending stress, radially-outward from the hub portion  12  and radially-inward from the radially-outermost point. For example, the thinnest point of the flexure portion  16  may be placed at a point that is 40%-80% of the radius dimension. As a result, the diaphragm  11  can be optimized for bending stresses as well as for shear stresses, as is likewise stated in U.S. Pat. No. 5,158,504 to Stocco, the entire contents of which are hereby incorporated by reference.  
         [0025]     It should be noted that although the illustrated embodiment includes certain profiles of the outer sides  26 , the outer sides  26  could also have any profile, whether curved, straight, or combinations of both, and still contain a transition point  28  that defines the thinnest portions of the thickness  27  radially-inward from the radially-outermost point of the flexure portion  16 .  
         [0026]     A generally u-shaped flexure space  31  is defined by the outer hub wall  23  and the inner sides  25  of adjacent flexure portions  16 . The flexure space  31  extends radially outward from the outer hub wall  23  and does not narrow in a radially-outward direction (when the annular members are in an unflexed condition). Likewise, a generally u-shaped connecting space  40  extends radially outward from the flexure space  31  and is defined by the inner connecting surfaces  37  of adjacent flexure portions  16 . The fact that the flexure space  31  does not narrow in a radially-outward direction means that the inner sides  25  do not have undercut sections in the radial direction. This makes the flexible coupling device  10  easier to fabricate, and thus makes it easier to use conventional machining methods including, but not limited to turning, facing, or boring, to form the flexure space  31 . It should be noted, however, that neither the flexure space  31 , nor the connecting space  40  need be generally u-shaped. For example, the distance between the inner sides  25  of adjacent annular members  13  could increase radially outward such that the flexure space  31  is generally v-shaped. Likewise, the distance between the inner surfaces  37  of adjacent annular members  13  could increase radially outward such that the connecting space  40  is generally v-shaped.  
         [0027]     The flexible coupling device  10  of the present invention has several advantages that provide a simplified and commercially efficient coupling device for use in transmitting power between rotary members that are axially and/or angularly misaligned. The flexure portions  16 , which include substantially straight inner sides  25  and outer sides  26  that have a first portion  34  and a second portion  35 , advantageously have the thinnest portion of the thickness  27  at a transition point  28  that is radially inside of the outer-most point of the flexure portion  16 . This positioning allows optimization of both the torque and bending stresses. Additionally, the diaphragm  11  is constructed of a unitary part. Although in certain circumstances it may still be advantageous to do so, this obviates the need for electron beam welding of adjacent coupling parts used in conventional coupling devices. Also, the flexure space  31  does not narrow in a radially-outward direction. This allows the machining or forming of the flexure space  31  to be more simplified, and thus less expensive and more commercially efficient. It also advantageously requires contouring of only the outer sides  26  of the flexure portion  16  of the diaphragm  11 . Although conventional methods may be used, this results in the ability to use methods less expensive and time consuming than the conventional electro-chemical machining.  
         [0028]     Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.