Abstract:
Embodiments of the disclosure relate generally to shaft devices and, more particularly, to a shaft device having at least one portion that is radially distanced from a longitudinal axis of the shaft device. In one embodiment, the invention provides a first aspect of the disclosure provides a shaft assembly for movement of a plurality of adjustable members, the shaft assembly comprising: an elongate shaft body having: a first end; a second end; a first portion oriented substantially along a longitudinal axis of the elongate shaft body; and a second portion oriented substantially parallel to and radially displaced from the longitudinal axis of the elongate shaft body; and a plurality of attachment devices disposed along an outer surface of the elongate shaft body.

Description:
BACKGROUND 
       [0001]    Embodiments of the disclosure relate generally to shaft devices and, more particularly, to a shaft device having at least one portion that is radially distanced from a longitudinal axis of the shaft device. 
       SUMMARY OF THE INVENTION 
       [0002]    A first aspect of the disclosure provides a shaft assembly for movement of a plurality of adjustable members, the shaft assembly comprising: an elongate shaft body having: a first end; a second end; a first portion oriented substantially along a longitudinal axis of the elongate shaft body; and a second portion oriented substantially parallel to and radially displaced from the longitudinal axis of the elongate shaft body; and a plurality of attachment devices disposed along an outer surface of the elongate shaft body. 
         [0003]    The illustrative aspects of the present disclosure are designed to solve the problems herein described and/or other problems not discussed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]    These and other features of this disclosure will be more readily understood from the following detailed description of the various aspects of the disclosure taken in conjunction with the accompanying drawings that depict various embodiments of the disclosure, in which: 
           [0005]      FIG. 1  is a perspective view of a shaft device; 
           [0006]      FIG. 2  is a perspective view of a shaft device according to one embodiment of the invention; 
           [0007]      FIG. 3  is a perspective view of a shaft device according to another embodiment of the invention. 
           [0008]      FIG. 4  is a side view of an attachment device according to an embodiment of the invention; 
           [0009]      FIG. 5  is a top view of the attachment device of  FIG. 4  in conjunction with components of a stepped shaft device according to an embodiment of the invention; 
           [0010]      FIG. 6  is a side view of an attachment device according to another embodiment of the invention; and 
           [0011]      FIG. 7  is a top view of the attachment device of  FIG. 6  in conjunction with components of a stepped shaft device according to another embodiment of the invention. 
       
    
    
       [0012]    It is noted that the drawings of the disclosure are not to scale. The drawings are intended to depict only typical aspects of the disclosure, and therefore should not be considered as limiting the scope of the disclosure. In the drawings, like numbering represents like elements between the drawings. 
       DETAILED DESCRIPTION 
       [0013]    Shaft-like devices are commonly used to provide rotational control of arrays of vanes in compressors and gas turbines. Typically, such a device comprises an elongate member having a plurality of attachment devices along its length, to each of which an actuator rod or control rod may be connected. 
         [0014]      FIG. 1  shows a perspective view of a device  100 , with an elongate shaft  110  having a first end  112  and a second end  114 . Each of the first and second ends  112 ,  114  is typically mounted on bearings to facilitate rotation of elongate shaft  110 . A plurality of attachment devices  120 ,  122 ,  124 ,  126  are fastened along elongate shaft  110  and to which may be attached, for example, a control rod, which may then be used to control a variable vane of a stage of a gas turbine. 
         [0015]    Attachment devices  120 ,  122 ,  124 ,  126  extend from elongate shaft  110  and from its longitudinal axis L to varying degrees, as a consequence of their intended function in controlling, for example, variable vanes of a gas turbine. The varying radial lengths of the attachment devices  120 ,  122 ,  124 ,  126  with respect to elongate shaft  110  impart high stresses, particularly at those attachment devices extending furthest from elongate shaft  110 . This requires the use of higher strength materials for elongate shaft  110  and attachment devices  120 ,  122 ,  124 ,  126 . 
         [0016]    In addition, attachment devices  120 ,  122 ,  124 ,  126  are typically fitted into a flanged joint  130 ,  132 ,  134 ,  136  along the length of elongate shaft  110 . This, however, requires some fastening apparatus or method to fix, for example, attachment device  120  within flanged joint  130 . Such apparatuses and methods often include, for example, threaded bolts, bonding, brazing, welding, etc., each of which increases the complexity and expense of manufacturing known shaft-like devices. 
         [0017]      FIG. 2  shows a perspective view of a stepped shaft assembly  200  according to one embodiment of the invention. Stepped shaft assembly  200  includes an elongate shaft body  210  with a first end  212  and a second end  214 . However, unlike the known device of  FIG. 1 , elongate shaft body  210  includes a first portion  216  oriented substantially along a longitudinal axis L of the elongate shaft body  210  (i.e., a longitudinal axis extending through first and second ends  212 ,  214 ) and a second portion  218  oriented substantially parallel to and radially displaced to a distance D from the longitudinal axis L of the elongate shaft body  210 . That is, second portion  218  includes a second longitudinal axis L′ radially displaced from longitudinal axis L. 
         [0018]    A plurality of attachment devices  220 ,  222 ,  224 ,  226  is disposed along elongate shaft body  210 . Each attachment device  220 ,  222 ,  224 ,  226  extends from either first portion  216  or second portion  218  to a distance d 1 , d 2 , d 3 , d 4 , respectively. The radial displacement of second portion  218  of elongate shaft body  210  from the longitudinal axis L permits the use of shorter attachment devices  220 ,  222 ,  224  along second portion  218 . That is, attachment devices  220 ,  222 ,  224  extend radially from second portion  218  (and from longitudinal axis L) to distances d 2 , d 3 , d 4 , respectively, which is a lesser distance than if second portion  218  was oriented substantially along longitudinal axis L. 
         [0019]    The use of shorter attachment devices  220 ,  222 ,  224  reduces the load path and the stresses to which attachment devices  220 ,  222 ,  224  are exposed. As a consequence, stepped shaft assembly  200  may be formed from less expensive, lower-strength materials than may be known devices. In addition, elongate shaft body  210  and attachment devices  220 ,  222 ,  224  may be forged or cast as a single unit. That is, attachment devices  220 ,  222 ,  224  may be structurally integrated into elongate shaft body  210  during the manufacturing process, obviating the need for joints into which attachment devices are inserted and into which the attachment devices must be fastened. 
         [0020]    In other embodiments of the invention, a stepped shaft device may include more than one “stepped” portions radially displaced from the longitudinal axis of the elongate shaft body, each of the “stepped” portions being displaced to a different degree. Such an embodiment may be desirable where, for example, the extent of displacement is intended to be proportional to the lengths of the attachment devices that would otherwise be employed. In such an embodiment, attachment devices may be disposed along the lengths of any or each of the “stepped” portions. 
         [0021]    Materials from which stepped shaft assembly  200  may be formed include, for example, A514 steel, 2.25 Cr-1 Mo steel, and carbon steel. Any such material may optionally include a coating or protectant, such as a rust protectant. Other suitable materials and other methods of forming stepped shaft assembly  200  will be apparent to one skilled in the art and are within the scope of the invention. 
         [0022]    In some cases, it has been found that the use of a stepped shaft assembly according to embodiments of the invention has resulted in between about a 35% and a 40% reduction in stresses at the attachment devices. At the same time, the total amount of material used in the cast stepped shaft assembly of  FIG. 2  has been found to be reduced by between about 25% and about 30%. 
         [0023]      FIG. 3  shows a perspective view of a stepped shaft assembly  300  according to another embodiment of the disclosure. Here, rather than a singular cast body, stepped shaft assembly  300  comprises a welded or otherwise joined or fused configuration made up of a first cylindrical member  316  and a second cylindrical member  318 . A first plate member  340  joins second cylindrical member  318  to a first end  312  and a second plate member  342  joins first cylindrical member  316  and second cylindrical member  318 . 
         [0024]    As can be seen in  FIG. 3 , second cylindrical member  318  is laterally displaced from the longitudinal axis L of stepped shaft assembly  300  to distance D by first plate member  340  and second plate member  342 . That is, a second longitudinal axis L′ of second cylindrical member  318  is radially displaced to distance D from longitudinal axis L extending through first and second ends  312 ,  314 . Functionally, this is similar to the embodiment shown in  FIG. 2 , resulting in decreased stresses at attachment devices  320 ,  322 ,  324 . Also similar to the embodiment of  FIG. 2 , therefore, stepped shaft assembly  300  may be formed from less expensive, lower-strength materials than may be known devices. 
         [0025]    Attachment devices  320 ,  322 ,  324 ,  326  may be affixed to first cylindrical member  316  or second cylindrical member  318  in any of a number of ways. As shown in  FIG. 3 , attachment devices  320 ,  322 ,  324 ,  326  comprise a pair of adjacent, similarly-sized and similarly-shaped arms. These arms may, for example, be sized to slide over the exterior surface of first or second cylindrical member  316 ,  318  and welded or otherwise fixed in place. Alternatively, each of first and second cylindrical members  316 ,  318  may be made up of a plurality of shorter lengths which are affixed to and joined by attachment devices  320 ,  322 ,  324 ,  326 . 
         [0026]    In some embodiments of the invention, cylindrical members  316 ,  318  may be solid in cross-section. In other embodiments, cylindrical members  316 ,  318  may be tubular, i.e., hollow in cross-section. In embodiments in which cylindrical members  316 ,  318  are tubular, ends  312 ,  314  may be inserted into first plate member  340  and first cylindrical member  316 , respectively. 
         [0027]      FIG. 4  shows a side view of attachment device  326  of  FIG. 3 . As can be seen, attachment device includes a body  350  having a first aperture  352  and a second aperture  354 . First aperture  352  is sized and shaped to accommodate first cylindrical member  316 . Second aperture  354  is sized and shaped to accommodate a device for securing, for example, a control rod, as discussed above. Apertures  352 ,  354  are shown as substantially circular, but may be of any shape compatible with, respectively, first cylindrical member  316  and the device for securing, for example, the control rod. 
         [0028]      FIG. 5  shows a top view of attachment device  326 , which can be seen as comprising a pair of bodies  350 ,  351 , a pair of first apertures  352  ( FIG. 4 ; obscured in  FIG. 5 ),  354 , and a pair of second apertures  354 ,  355 , each aligned to accommodate passage of first cylindrical member  316  through first apertures  352 ,  353  along path A. Bodies  350 ,  351  are separated by a space S, such that, in place along either first or second cylindrical members  316 ,  318 , bodies  350 ,  351  are spaced along or parallel to the longitudinal axis L ( FIG. 3 ). As also shown in  FIG. 5 , first cylindrical member  316  is tubular, having an internal dimension sized to accept second end  314 , which may be solid rather than tubular. 
         [0029]    Once first cylindrical member  316  is passed through both first apertures  352 ,  353 , attachment device  326  may be fixed to first cylindrical member  316  by, for example, welding. Similarly, once second end  314  is passed into first cylindrical member  316  to the extent desired, second end  314  and first cylindrical member  316  may be fixed together by, for example, welding. 
         [0030]      FIGS. 6 and 7  show, respectively, side and top views of an attachment device  426  according to another embodiment of the invention briefly described above. Referring to  FIG. 6 , the body  450  of attachment device  426  is truncated as compared to the embodiment of  FIG. 4 . Here, aperture  452  is substantially semi-circular rather than circular, as in  FIG. 4 . 
         [0031]      FIG. 7  shows a top view of attachment device  426  in conjunction with two segments  416 A,  416 B of first cylindrical member  416  ( FIG. 4 ). Here, segments  416 A,  416 B may effectively be joined, at least in part, by joining (via welding, etc.) body  450  to first segment  416 A and by joining body  451  to second segment  416 B. Segments  416 A,  416 B may optionally be directly joined as well, via welding, etc. 
         [0032]    In still another embodiment of the invention, an attachment device such as attachment device  426  may be used in combination with an unsegmented cylindrical member, such as first cylindrical member  316  ( FIGS. 3 and 5 ), with the bodies of such attachment devices joined to the unsegmented cylindrical member. 
         [0033]    The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, 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. 
         [0034]    The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present disclosure has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the disclosure in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the disclosure. The embodiment was chosen and described in order to best explain the principles of the disclosure and the practical application, and to enable others of ordinary skill in the art to understand the disclosure for various embodiments with various modifications as are suited to the particular use contemplated.