Abstract:
An adapter for detachably concentrically coupling shafts having a range of diameters to a rotating input actuator capable of rotating about a rotational axis is disclosed in which the force to transfer rotational torque between said shaft and a rotating input actuator to which said housing is attached is generated independent of said self-centering adjustment system.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    I. Field of the Invention  
           [0002]    The present invention relates to an apparatus for the attachment of a shaft, particularly that of a rotating control device, to an operating unit or actuator drive system. More particularly, the invention concerns a device of the class that includes a centering shaft adapter in which separate mechanisms are used to (1) accommodate shafts of varying sizes while keeping any shaft concentric with the hub of a rotating actuator or drive system attached to the adapter and to (2) generate the clamping force required to transfer the torque load between the shaft and the adapter.  
           [0003]    II. Related Art  
           [0004]    Many control devices include motors driving rotating hubs usually having meshing splines of a given pitch which, in turn, are used to operate a concentrically aligned rotary axle or shaft of a control device such as a butterfly ventilating valve, damper, or the like. An integral adapter device is used to directly couple the rotating output hub to an input shaft of a control device in concentric arrangement. The drive units are designed to be used with a variety of input or control device shaft sizes. However, generally in the past, it has been necessary to provide special arrangements in order to change shaft sizes. For example, a series of adapters might be used to accommodate shafts of different sizes to enable the system to maintain the desired concentric arrangement. Alternatively, a plurality of separate inserts have been devised, one for each size shaft to space the shaft from the clamp jaws the appropriate amount to maintain a concentricity with the output hub of the actuator.  
           [0005]    Mechanical clamping devices also exist which adjust the center of the clamped shaft to maintain concentricity with a corresponding hub over a range of shaft sizes. One such device is illustrated and described in U.S. Pat. No. 5,544,970 to Studer which utilizes a hollow member having internal and external threads which cooperate to open and close upper and lower jaw members to clamp about a shaft of interest. The outer threads engage an outer housing member which, in turn, operates the lower jaw; whereas the inner threads engage a bolt that pulls on the upper jaw. A thread pitch ratio between the inner and outer threads is used to move the jaws an unequal amount so that the center between the jaws remains concentric with the axis of the hub. Although this successfully accomplishes the desired adjustment, the design has several drawbacks or limitations. First, the centering mechanism must also supply the clamping force so that it must be built to transmit the entire system torque; and second, the double-threaded member is difficult to produce and involves the utilization of a very fine pitch on the outside thread which is readily susceptible to clogging and cross threading.  
           [0006]    Thus, there remains a definite need in the art for an adaptive coupling mechanism that utilizes parts that are readily made and provides a separate mechanism for the clamping and centering functions and which can accommodate a wide range of shaft sizes.  
         SUMMARY OF THE INVENTION  
         [0007]    The present invention provides a single, relatively simple mechanism for concentrically adapting the output hub of a direct coupled actuator to operate control device shafts of varying sizes, thereby obviating the need for separate connecting devices or inserts to accommodate a range of shaft sizes. In this manner, a direct coupled actuator can be mounted on shafts of different sizes interchangeably while maintaining concentric alignment between the output hub of the actuator and the shaft of interest. In addition to being a self-centering shaft adapter, the adapter of the invention utilizes separate mechanisms to keep the shaft and output hub concentric and to generate the clamping force required to transfer the torque load from the shaft to the adapter. In this manner, the self-centering mechanism is not required to transmit the full torque load between the adapter and the clamped shaft but only to keep the shaft and output hub concentric. The system consists of opposed jaws that grip each side of the shaft and are mechanically linked to insure that both jaws travel in equal amounts with respect to the geometric center of an integral drive hub when adjusted to accommodate a shaft that is being clamped.  
           [0008]    The mechanism may take any of several forms including double and single rack and pinion systems, beam systems, and cam and follower devices. Each of these mechanisms operates to concentrically open and close a pair of clamping jaws about a geometric center using a mechanical linkage operated by a conventional threaded fastening arrangement, as will be described. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    In the drawings, wherein like numerals designate like parts throughout the same:  
         [0010]    [0010]FIG. 1 is an exploded perspective view of one embodiment of the self-centering shaft adapter of the invention centered utilizing a rotating cam system;  
         [0011]    [0011]FIG. 2A is an exploded perspective view of an alternate embodiment of the self-centering shaft adapter of the invention also employing a cam system;  
         [0012]    [0012]FIG. 2B is a top plan view of the embodiment of FIG. 2A in an assembled state;  
         [0013]    FIGS.  2 C- 2 E represent various sectional views of the embodiment of FIGS. 2A and 2B, as noted on the drawings;  
         [0014]    [0014]FIG. 3A is a top plan view of another embodiment of the self-centering shaft adapter of the invention utilizing a single pinion rack and pinion centering system;  
         [0015]    [0015]FIG. 3C is a bottom end view of the embodiment of  3 A;  
         [0016]    [0016]FIGS. 3B, 3D and  3 E represent sectional views noted on FIGS. 3A and 3C;  
         [0017]    [0017]FIG. 4A is a partially cut-away top view of an alternate embodiment showing internal parts and employing a pair of rack and pinion systems;  
         [0018]    [0018]FIG. 4B is a bottom view of FIG. 4A;  
         [0019]    [0019]FIG. 5 is a top view of yet another embodiment which utilizes a beam-type centering arrangement; and  
         [0020]    [0020]FIG. 6 is an exploded perspective view of an embodiment similar to that shown in FIG. 1 with certain modifications. 
     
    
     DETAILED DESCRIPTION  
       [0021]    The following detailed description describes a variety of implementations of the self-centering shaft adapter of the invention which employ several different mechanisms. Each uses a relatively simple mechanical system to maintain concentricity between integral drive hub and control shaft which should have a long reliable life without the need for expensive, tight tolerance parts. Each of the embodiments also embraces the concept that the self-centering aspect of the mechanism which keeps the shaft and hub concentric is not used to generate the clamping force required to transfer the torque load between the clamped shaft and the shaft adapter. The following embodiments are presented as exemplary of the invention but are not meant to limit the scope of the concept in any manner. When referring to the clamping jaws or other parts of the system, the terms “upper” and “lower” refer to parts of the device as drawn and not to any particular mounted orientation.  
         [0022]    [0022]FIG. 1 is an exploded perspective view illustrating one embodiment of a self-centering shaft adapter of the invention which employs centering cams in conjunction with opposed jaw clamps whose separation is controlled by a spring-biased T-bolt and nut. The system, generally at  20 , includes an upper housing  22  and a lower housing  24  together with a generally U-shaped inner (upper) jaw clamp device  26  which has generally parallel spaced sides  28  and  30  and which is designed to be contained within and slide relative to the spaced parallel sides  32  and  34  of a rather larger generally U-shaped outer (lower) jaw clamp member  36 .  
         [0023]    The spaced parallel sides of upper jaw clamping member  26  include parallel clamping or toothed fractions  40  and the lower jaw member  36  is provided with opposed similar toothed fractions at  42 . A T-bolt  44  with flattened anti-rotation head portion  46  is designed to slip through openings  48  and  50  in respective members  26  and  36  when the upper jaw clamp  26  is assembled into the lower jaw clamp  36  and nut  52  is threaded on the protruding end thereof. The opposed shaped toothed fractions  40  and  42  are caused to converge and diverge by rotation of nut  52  aided by a compression spring  54  which slides over T-bolt  44 .  
         [0024]    The system is further provided with a pair of generally flat washer-shaped spaced centering cam members  56  and  58 . The centering cam device  58  is provided with a pair of follower pins  60  and  62  located on the same side of the cam member  58  spaced 180° apart and extending perpendicular to the plane of the cam member. The cam device  58  is designed to nest in a recess  61  in lower housing  24  and rotate relative thereto. The parallel sides  28  and  30  of upper (inner) jaw member  26  are provided with aligned notches or slots  64  on one side thereof and with elongate recesses, one of which is shown at  66  on the other. The lower (outer) jaw member  36  is likewise provided with aligned notches or slots, one of which is shown at  68 , and recesses  70 , but is designed to be assembled in opposite side-to-side relation with respect to jaw member  26  as shown in FIG. 1. Holes  72  provided in the centering cam member  56  are designed to align with and entertain the pins  60  and  62  in the device as assembled. A driving hub  74  provided with splines (not shown) is fashioned integral with the lower housing member  24 . Threaded devices such as machine screws (not shown) can be used to assemble the housing members  22  and  24  capturing the intermediate parts therebetween.  
         [0025]    In operation, tightening of the nut  52  draws the upper and lower toothed jaw portions  40  and  42  closer together. (Note that the T-bolt head  46  is shaped with flat sides so that it cannot rotate within the lower U-portion of the upper clamp  26 .) As is apparent from the figure, at the same time, the movement of the jaw clamps  26  with slots  64  causes the pins  60 ,  62  to rotate counterclockwise and, in turn, operate via slot  68  to displace the lower jaw member  36  an equal distant amount in the opposite direction. In this manner, using the spring  54  to maintain tension, the device will properly center about any shaft inserted through the jaws within the limits of its clamping capacity size.  
         [0026]    A somewhat similar arrangement in an alternate embodiment is depicted in the several views of FIGS.  2 A- 2 E. As seen generally at  80 , in the exploded view of FIG. 2A, there is provided a lower housing  82  configured to receive an upper housing  84 . U-shaped inner (upper) jaw clamp  86  and U-shaped outer (lower) jaw clamp  88 , T-bolt  90 , nut  92  and compression spring  94  are also shown. A single centering cam member  96  configured to nest in a recess  98  in the lower housing  82  is provided with a pair of opposed (180° apart) raised extensions or tabs  100  (see FIG. 2D). The upper (inner) jaw  86  is provided with a notch  102  and cutout  104  (FIG. 2D) in the lower flange; and the lower flange of the outer (lower) jaw clamp  88  is likewise constructed in opposite relation with notch  106  and recess  108 . A shaft to be captured is pictured at  110  and a splined integral driving hub is shown attached to the outer housing at  112 . As was the case with the embodiment of FIG. 1, the centering cam member  96  with raised tabs  100  operates in conjunction with the notches  102 ,  106  in the respective jaws  86  and  88  to center a shaft of any diameter as at  110  with respect to the hub  112  (FIG. 2E).  
         [0027]    FIGS.  3 A- 3 E depict another embodiment which accomplishes shaft diameter-independent centering using a rack and pinion system. That device includes housing members  120  and  122  enclosing the U-shaped upper (inner) jaw  124  and lower (outer) U-shaped jaw  126  shown capturing a shaft  128 . A clamping bolt  130  with nut  132  and biasing compression spring  134  are included. This embodiment is further provided with a pinion  136  mounted on a fixed shaft  138  and designed to rotate about the shaft in response to the movement of a pair of spaced rack members  140  and  142 , respectively fixed to the upper (inner) and lower (outer) jaw members  124  and  126 . In this manner, movement of the jaw in equal distance in opposite directions is assured as they are opened and closed about a shaft at  128  by rotation of the nut  132 . As with other embodiments, the outer housing is attached to the output hub of a direct coupled actuator. Also, as with the other embodiments, all of the clamping force is provided by the bolt and nut system whereas the operating torque is transmitted between the interface of the jaws and the housing.  
         [0028]    [0028]FIGS. 4A and 4B depict an alternate form of a rack and pinion operated self-centering device using dual rack and pinion systems. The device includes a U-bolt  150  carried in a frame member  151  carrying an upper or inner casting  152  which, in turn, includes a jaw member  154  and a lower or outer casting  156  which carries a lower jaw  158 . A pair of pinions  160 ,  162  carried on shafts  164 ,  166  fixed to the outer housing (not shown) engage respectively upper and lower rack portions  168 ,  170  and  172 ,  174  on either side of the upper or inner casting  152 . Clamping is provided by a pair of nuts  176  attached to the ends  178  of U-bolt  150 .  
         [0029]    [0029]FIG. 5 illustrates a beam version of a self-centering shaft adapter and includes an outer housing  200  in which is mounted a U-shaped upper jaw  202 , a U-shaped lower jaw  204 , the jaws having respective shaft engaging teeth  206  and  208 . Reciprocal operation for opening and closing the jaws is provided by a T-bolt  210  with nut  212  and biasing compression spring  214  in the manner of previously described embodiments as discussed above in regard to FIGS.  1 - 3 . A pivot arm  216  is provided which is mounted on a pivot shaft  218  fixed to the outer housing through a clearance slot  220 . End  222  of pivot arm  216  is provided with a pin  224  which engages a slot  226  in the upper jaw  202 . End  228  is provided with a pin  230  which engages a slot  232  in the lower jaw  204 . This system allows centering adjustment as the jaws are opened and closed to accommodate different diameter shafts.  
         [0030]    In the exploded perspective view of FIG. 6, there is illustrated a cam-operated embodiment similar to that shown in FIG. 1 and FIG. 2A- 2 E, but in a somewhat simplified and more compact form. This embodiment, generally at  300 , includes an upper housing  302  and a lower housing  304  which includes an integral driving hub  306  with outer splines  308  adapted to be received in a driving actuator mechanism (not shown). A generally U-shaped inner (upper) jaw clamp member  310  with spaced parallel sides  312 ,  314  is designed to be contained within and slide reciprocally relative to the spaced parallel sides  316 ,  318  of an outer (lower) U-shaped jaw clamp member  320 . The spaced parallel sides  312 ,  314 ,  316  and  318  include respective opposed parallel toothed fractions  322  and  324  which are designed to converge and clamp a shaft of interest therebetween.  
         [0031]    The jaw clamp members  310  and  320  are retained and operated to open and close using an internally threaded member  326  having projections  328  press fit into matching openings  330  in the base of inner (upper) jaw clamp member  310 . A partially threaded bolt device  332  carried within and free to rotate relative to outer (lower) jaw clamp member  320  is designed to be threaded into member  326  at  334  and is used to adjust the span of the jaw clamp members  310  and  320 . The bolt device  332  is retained within the lower jaw  320  by a hollow member  335  in which it is free to rotate. No spring is necessary as the jaws are easily pried apart by hand, however, one can be provided if desired.  
         [0032]    Notches or slots  336  are aligned on one side of base parallel sides  312  and  314  of upper jaw clamp member  310  and in the opposite side (as assembled) of base sides  316 ,  318  of lower jaw clamp member  320  at  338 . Corresponding accommodating clearance recesses are notched in the jaw clamp member sides opposite the notches at  340  and  342 . A single round, relatively flat cam member  344  having a central opening  346 , which aligns with central openings  348  and  350  in upper and lower housing members  302  and  304 , respectively, carries a pair of opposed follower pins  352 ,  354  on the opposite side thereof and spaced 180° apart. The pins extend perpendicular to the plane of the cam element  344 . The housing is fastened together using threaded fasteners  356 .  
         [0033]    This system operates in the same manner as the embodiment of FIG. 1 with the follower pins  352  and  354  extending through the notches  336  and  338  in jaw members  310  and  320 , and the relative movement of the jaw members  310  and  320  operating through the pins to rotate the cam member  344  so that the upper and lower jaw movement is equal distance from the center of a captured shaft which, in turn, remains co-incident with the center line of the driving hub  306 .  
         [0034]    It should be noted that in this embodiment, the threaded adjustment device  332  need not protrude beyond the confines of the housing making the system more compact. The housing member  302  is provided with curved slots  358  and lower member  304  with curved slots  360  which accommodate and guide the follower pins  352  and  354  eliminating the need for a second cam element.  
         [0035]    This invention has been described herein in considerable detail in order to comply with the patent statutes and to provide those skilled in the art with the information needed to apply the novel principles and to construct and use such specialized components as are required. However, it is to be understood that the invention can be carried out by specifically different equipment and devices, and that various modifications, both as to the equipment and operating procedures, can be accomplished without departing from the scope of the invention itself.