Abstract:
A fastener comprising a head; a first section extending from the head and defining a first outside diameter, wherein the first section is unthreaded; and a second section co-axially extending from the first section and defining a second outside diameter. The second section being threaded and the second outside diameter being smaller than the first outside diameter.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/310,547, filed on Mar. 4, 2010. The entire disclosure of the above application is incorporated herein by reference. 
     
    
     FIELD 
       [0002]    The present disclosure relates to fasteners and, more particularly, relates to fasteners for coupling flexible elements. 
       BACKGROUND AND SUMMARY 
       [0003]    This section provides background information related to the present disclosure which is not necessarily prior art. This section also provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
         [0004]    Flexible couplings typically employ one or more flexible elements to simultaneously transmit torque and accommodate misalignment of the connected equipment. Some types of flexible couplings employ flexible elements that are connected to the other coupling components by means of fasteners and transmit torque circumferentially between these fasteners. 
         [0005]    Typically, bolts or screws with similar or consistent body and thread diameters are used to connect flexible elements to the other coupling components. Fasteners with consistent diameter of thread and body can be difficult to assemble and the threads can become damaged during assembly and disassembly. 
         [0006]    In some conventional designs, a single or multi-piece bushing is assembled through the holes in the flex element and mating component in order to align and connect the two components, and a fastener (or fasteners) is (are) assembled with this bushing in order to clamp the flex element to the mating component. In simpler designs, a fastener is assembled through the holes in the flex element and mating component, and this fastener is used to both align the two components and clamp them together. However, many of these conventional solutions are cumbersome, difficult to install, or easily damaged. 
         [0007]    The present teachings, however, provide a single fastener having a unique construction that can be used to both align a flex element with the mating component, and further clamp or fasten the flex element and mating component together. 
         [0008]    In many applications, it is generally advantageous to have a minimal clearance between the fasteners and the holes of the flex element and the mating component. Therefore, the holes in the flex element must be accurately aligned with the holes in the mating components in order to install the fasteners. As a result, it is possible to damage the threads on the fastener as they are assembled and disassembled through the holes in the flex element and mating component. 
         [0009]    In some flexible element designs it can be advantageous to introduce a pre-tension into the flexible element sections between the fasteners in order to minimize compression or buckling of these sections when torque is applied. One method to do this is to design the bolt circle (that is, the radial position of the through hole) of the flexible element to be slightly smaller than the bolt circle of the coupling component to which it is connected. In this case, a pre-tension is introduced into the flexible element when it is connected to the other coupling components with the fasteners provided. Depending on the amount of pre-tension and the size of the coupling, conventional solutions can be difficult to assemble and the fasteners can potentially be damaged during assembly and disassembly. 
         [0010]    The fasteners described here are designed to facilitate installation through a flexible element and a mating component, and also to protect the threads on the fasteners during installation. 
         [0011]    Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0012]    The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
           [0013]      FIG. 1  is a partial cross-sectional view illustrating a fastener according to the principles of the present teachings disassembled from a flexible element and a mating component; 
           [0014]      FIG. 2  is a partial cross-sectional view illustrating the fastener engaged with the mating component at a first diameter section and engaged with the flexible element at a second diameter section; 
           [0015]      FIG. 3  is a partial cross-sectional view illustrating the fastener engaged with the mating component at the first diameter section and engaged with the flexible element at the first diameter section; 
           [0016]      FIG. 4  is a partial cross-sectional view illustrating a fastener according to some embodiments of the present teachings disassembled from a flexible element and a mating component; 
           [0017]      FIG. 5  is a side view of a fastener according to some embodiments of the present teachings having a thread cover, wherein the fastener comprises a tapered shoulder for installation and the thread cover defines an outer diameter that is smaller than the first diameter section of the fastener; 
           [0018]      FIG. 6  is a side view of a fastener according to some embodiments of the present teachings having a thread cover, wherein the thread cover comprises a tapered tail section for installation extending from the outer diameter of the threaded cover to the first diameter section of the fastener; 
           [0019]      FIG. 7  is a side view of a fastener according to some embodiments of the present teachings having a thread cover, wherein the thread cover defines an outer diameter that is similar or consistent with to the first diameter section of the fastener; and 
           [0020]      FIG. 8  is an assembled view of a fastener according to the principles of the present teachings together with a flexible element and mating components. 
       
    
    
       [0021]    Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
       DETAILED DESCRIPTION 
       [0022]    Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. 
         [0023]    The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a”, “an” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed. 
         [0024]    When an element or layer is referred to as being “on”, “engaged to”, “connected to” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to”, “directly connected to” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
         [0025]    According to the principles of the present teachings, as illustrated in  FIGS. 1-8 , a fastener  10  is provided having a head  11 , a first diameter section  12  and a second diameter section  14 . In some embodiments, first diameter section  12  can be an unthreaded section defining a first outer diameter dimension. In some embodiments, second diameter section  14  can be a threaded section defining a second outer diameter dimension. As can be seen in the figures, second outer diameter dimension of second diameter section  14  can be smaller than first outer diameter dimension of first diameter section  12 . 
         [0026]    Unlike a traditional shoulder bolt, the outer diameter of the unthreaded section is designed specifically to prevent threaded second diameter section  14  from contacting a flexible element  100  during assembly and disassembly. 
         [0027]    In some embodiments, fastener  10  can comprise a transition section  16 , such as a gradually tapered transition section ( FIGS. 1-5 ), between threaded second diameter section  14  and the unthreaded first diameter section  12  designed to facilitate assembly with the flexible element. 
         [0028]    In some embodiments, threaded second diameter section  14  of fastener  10  is designed to be sufficiently smaller than the unthreaded first diameter section  12  of fastener  10  to ensure that threaded second diameter section  14  does not make contact with the through-holes  102  in flexible element  100  during assembly or disassembly. This provides the advantage of protecting the threads on threaded second diameter section  14  of fastener  10  during assembly and disassembly. 
         [0029]    It should be appreciated that the smaller diameter of threaded second diameter section  14  of fastener  10  provides an additional benefit in that a lower tightening torque is required (because of the reduced outside diameter relative to single diameter fasteners). This is advantageous in that smaller tooling requirements are required and, thus, safety can be improved. Moreover, less force is required by the installer during installation. 
         [0030]    The present teachings take into account various design criteria, such as the location tolerances of the through-holes relative to one another as well as any intentionally designed offset of the holes for pre-tension or other reasons. Moreover, the present teachings take into account material strength considerations and the necessary size of threaded second diameter section  14  to achieve the required fastener tension and clamping force for flexible element  100  as required for proper operation of the flexible coupling. 
         [0031]    Still referring to  FIGS. 1-5 , in some embodiments tapered, transition section  16  of fastener  10  can be configured and sized to make first contact with the holes  102  in flexible element  100  and to facilitate assembly. The tapered, transition section  16  can begin just past threaded second diameter section  14 . In this way, the tapered contour of transition section  16  can provide a smooth transition to permit holes  102  of flexible element  100  to contact this camming surface and be properly positioned on unthreaded first diameter section  12 . Generally, a taper of less than 45 degrees would be advantageous in providing a smooth transition. As mentioned above, in this way, the threads are protected by avoiding contact during assembly and disassembly. Another advantage of this design is that the taper aligns the flex element with the mating component as fastener  10  is assembled through both, which makes assembly easier for the installer. Further, the taper facilitates assembly in the case where the holes in the two components are misaligned, either simply due to tolerances or intentionally by design, minimizing the force required to assemble fastener  10   s.    
         [0032]    With particular reference to  FIGS. 5-6 , in some embodiments, fastener  10  can comprise a thread cover  20  disposed over threaded second diameter section  14  to protect the threads thereof during shipment, handling, assembly, disassembly, and the like. The shape further facilitates installation in the case where the holes are not initially well-aligned in addition to being designed for pre-tension. Thread cover  20 , in some embodiments, can comprise a sheath-like member being made of a predetermined material sufficient to protect the threads, such as plastic, having a tip portion  22  protecting the end  26  of fastener  10  and a sheath portion  24  generally surrounding the threads. Thread cover  20  can terminate at an end  28  that is generally adjacent transition section  16  of fastener  10 . 
         [0033]    It should be appreciated that thread cover  20  can be sized and/or configured in various combinations. By way of non-limiting example, in some embodiments, thread cover  20  can be generally consistent in outside diameter ( FIG. 5 ) and be sized such that its outer diameter is smaller than the first diameter of first diameter section  12 . In such case, tapered, transition section  16  can be used. In some embodiments, thread cover  20  can have a trailing sloped end  28 ′ ( FIG. 6 ) that serves to transition from the outside diameter of thread cover  20  to the first diameter section  12 , thereby eliminating the need for tapered transition section  16 . In this regard, fastener  10  can define a 90 degree transition section  16 . Moreover, in some embodiments, thread cover  20  can be generally consistent in outside diameter ( FIG. 7 ) and be sized such that its outer diameter is equal to the first diameter of first diameter section  12 , thereby eliminating the need for tapered transition section  16 . In this regard, fastener  10  can define a 90 degree transition section  16 . It should be understood that thread cover  20  can be made of a material or include a coating that provides a low friction surface to facilitate assembly of flexible element  100  and mating components  200 . Moreover, in some embodiments, thread cover  20  can be made of plastic, metal, composite, rubber, polymer, wax/shellac (meltable material), soluble material, or other materials. In some embodiments, thread cover  20  can be installed on fastener  10  by threaded fit, slip fit, tight fit, shrunk on, or other method. Moreover, thread cover  20  can comprises a flat or tapered tip portion  22 . Thread cover  20  can be removed from fastener  10  by using an extension, pull tab, threaded insert for puller/pusher rod, or use a meltable/soluble material. Such features can be integral formed or require an additional part to permit it to be grabbed or otherwise removed. Moreover, thread cover  20  could be a perforated part that separates from the bolt easily or mounted by heating the protector and then reheat to remove. 
         [0034]    Generally, it should be understood that the principles of the present teachings provide a number of advantages over the prior art. Specifically, it should be recognized that the present teachings can be used in any assembly where two components have offset holes either by design or through tolerance buildup, thereby replacing tapered alignment pins. 
         [0035]    The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the invention, and all such modifications are intended to be included within the scope of the invention.