Abstract:
A method and system for a shaft coupling assembly is provided. The assembly includes a first coupling half coupled to a distal end of a first shaft wherein the first coupling half includes one or more projections extending away from the first coupling half. The shaft coupling assembly also includes a second coupling half coupled to a distal end of a second shaft wherein the second coupling half includes a media configured to matingly engage the one or more projections in an axial direction, the projections include a relatively large length to width ratio, the media displaces orthogonally to the insertion direction an amount sufficient to facilitate the insertion for each individual projection while substantially preventing gross movement of all of the projections in total such that a linear force or torque applied to one coupling half is transmitted through the mated projections and media.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The field of the invention relates generally to power transmission devices, and more specifically, to a method and system for coupling machine elements. 
         [0002]    A rotational accuracy and repeatability of known two part couplings used to couple coaxial shafts or other machine elements has been limited by a spacing of the pins, teeth or other projections in one coupling half that mate with defined sockets or other mating receptacles in the other coupling half. Readjustment in a second step is typically necessary for better accuracy of rotational alignment. Retention of rotational alignment or repeatability from one engagement cycle to the next is limited by the angular distance between projections (pitch in a geared coupling). 
         [0003]    Friction couplings or clutches theoretically have a continuous resolution that is not possible in a coupling or clutch with discrete mating parts. Friction couplings depend on relatively high mating forces applied orthogonally to the direction of a rotational torque to be transmitted if they are to operate without slippage and loss of resolution. 
         [0004]    Known couplings of current design have limitations including lack of rotational accuracy, repeatability and high coupling force required, which limit their usefulness or applicability in numerous applications. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0005]    In one embodiment, a shaft coupling assembly includes a first coupling half coupled to a distal end of a first shaft wherein the first coupling half includes one or more projections extending away from the first coupling half. The shaft coupling assembly also includes a second coupling half coupled to at least one of a distal end of a second shaft and a machine element wherein the second coupling half includes a media configured to matingly engage the one or more projections in an axial direction of the projections, where the one or more projections include a relatively large length to width ratio and when inserted into the media, the media displaces orthogonally to the insertion direction an amount sufficient to facilitate the insertion for each individual projection while substantially preventing gross movement of all of the projections in total such that a linear force or torque applied to one coupling half is transmitted through the mated projections and media. 
         [0006]    In another embodiment, a method of positioning an object includes extending a first coupling flange towards a face of a second coupling flange, engaging a resilient media that forms at least a portion of the face using one or more rigid pins extending toward the face from the first coupling flange, applying a force to the resilient media through the pins, and translating the second coupling in the direction of the force using the applied force. 
         [0007]    In yet another embodiment, a precision positioning system includes a source of mechanical power including a power shaft configured to transmit the mechanical power, a device configured to be translated from a first position to a second position using a load shaft, and a shaft coupling assembly configured to couple the power shaft to the load shaft during a positioning period and to decouple the power shaft from the load shaft during a quiescent period. The shaft coupling assembly including a first coupling half coupled to a distal end of one of the power shaft and the load shaft, the coupling half including one or more projections extending away from the first coupling half, a second coupling half coupled to a distal end of an other of the power shaft and the load shaft, the second coupling half including a media configured to matingly engage the one or more projections in an axial direction of the projections, where the one or more projections include a relatively large length to width ratio and when inserted into the media, the media displaces orthogonally to the insertion direction an amount sufficient to facilitate the insertion for each individual projection while substantially preventing gross movement of all of the projections in total such that a linear force or torque applied to one coupling half is transmitted through the mated projections and media. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIGS. 1A-12  show exemplary embodiments of the method and system described herein. 
           [0009]      FIG. 1A  is a perspective view of a pin felt coupling device in an uncoupled configuration in accordance with an exemplary embodiment of the present invention; 
           [0010]      FIG. 1B  is a perspective view of coupling device in a coupled configuration; 
           [0011]      FIG. 2A  is a perspective view of a pin felt coupling device in an uncoupled configuration in accordance with another exemplary embodiment of the present invention; 
           [0012]      FIG. 2B  is a perspective view of coupling device in a coupled configuration; 
           [0013]      FIG. 3A  is perspective view of a pin felt coupling device in an uncoupled configuration in accordance with still another exemplary embodiment of the present invention; 
           [0014]      FIG. 3B  is a perspective view of coupling device in a coupled configuration; 
           [0015]      FIG. 4  is an exploded view of a dual pin felt coupling device in accordance with yet another exemplary embodiment of the present invention; 
           [0016]      FIG. 5  is a perspective view of driver pin array in accordance with an exemplary embodiment of the present invention; 
           [0017]      FIG. 6  is a perspective view of a driver side of output rotor in accordance with an exemplary embodiment of the present invention; 
           [0018]      FIG. 7  is a perspective view of a cam side of output rotor in accordance with an exemplary embodiment of the present invention; 
           [0019]      FIG. 8  is a perspective view of rotary cam in accordance with an exemplary embodiment of the present invention; 
           [0020]      FIG. 9  is a perspective view of fixed cam in accordance with an exemplary embodiment of the present invention; 
           [0021]      FIG. 10  is a perspective view of shaft in accordance with an exemplary embodiment of the present invention; 
           [0022]      FIG. 11  is a perspective view of fully assembled pin felt coupling device in an uncoupled configuration where shaft is freely rotatable while holding output rotor stationary; 
           [0023]      FIG. 12  is a perspective view of fully assembled pin felt coupling device in a coupled configuration where a rotation force applied to shaft is transferred through pins and receptive media; and 
           [0024]      FIG. 13  is a perspective view of a receptive flange in accordance with an exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    The following detailed description illustrates embodiments of the invention by way of example and not by way of limitation. It is contemplated that the invention has general application to structural and methodical embodiments of a power transfer device in industrial, commercial, and residential applications. 
         [0026]    As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural elements or steps, unless such exclusion is explicitly recited. Furthermore, references to “one embodiment” of the present invention are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. 
         [0027]      FIG. 1A  is a perspective view of a pin felt coupling device  100  in an uncoupled configuration in accordance with an exemplary embodiment of the present invention.  FIG. 1B  is a perspective view of coupling device  100  in a coupled configuration. In the exemplary embodiment, coupling device  100  includes a first flange  102  coupled to a distal end  104  of a first shaft  106 . First shaft  106  includes a longitudinal axis of rotation  108 . First flange  102  includes one or more axially extending pins  110  having a height  112  and a diameter  114  that extend axially away from a face  115  of first flange  102 . Although described as pins having a diameter, pins  110  can be embodied in pins, prongs, studs, or other projections and can have any shaped cross-section and diameter  114  may refer to, rather than a circular dimension, but rather a cross-sectional dimension substantially perpendicular to axis  108 . In the exemplary embodiment, height  112  is significantly greater than diameter  114 . 
         [0028]    Coupling device  100  also includes a second flange  116  coupled to a distal end  118  of a second shaft  120 . Second shaft  120  includes a longitudinal axis of rotation  122 . Second flange  116  includes one or more circumferentially extending grooves  124  extending along a face  125  of flange  116 . In the exemplary embodiment, groove  124  is defined by a radially inner sidewall  126  and a radially outer sidewall  128 . A receptive media  130  is positioned between inner sidewall  126  and outer sidewall  128  within groove  124 . Receptive media  130  may be formed of, for example, but not limited to, felt, metal wool, and gel. In one embodiment, a surface  131  of receptive media  130  extends axially beyond face  125 . 
         [0029]    During use, first flange  102  and second flange  116  are positioned face-to-face a distance  132  apart. Distance  132  is selectable to permit an engagement of pins  110  and receptive media  130  to a coupled configuration of coupling device  100  (shown in  FIG. 1B ) and a disengagement of pins  110  and receptive media  130  in an uncoupled configuration (shown in  FIG. 1A ) of coupling device  100 . Receptive media  130  is formed of a material that is penetrable by pins  110  and sufficiently resilient to receive a rotational force in the circumferential direction from pins  110  and transfer the force to second flange  116 . Pins  110  engage receptive media  130  by penetrating a surface of receptive media  130  or by fitting into cavities  133  in surface  131 . In one embodiment, cavities  133  are formed in surface  131  complementary to pins  110 . In various embodiments, cavities  133  are formed in surface  131  by the engagement of pins  110  with surface  131 . For example, a pin  110  engaging surface  131  may dislocate a local portion of surface  131  to create an opening through which pin  110  is able to further penetrate surface  131  and slide into full engagement with media  130 . Dislocating the local portion and sliding past media  130  causes friction between pins  110  and media  130 , which defines an amount of axial force needed to fully engage pins  110  and media  130 . Pins  110  and media  130  are selected such that engagement and disengagement of pins  110  and media  130  results in a relatively minor amount of long term damage to either pins  110  or media  130  thereby providing a relatively long life and/or number of engagement/disengagement cycles. After engagement, one of shafts  106  or  120  can drive the other through coupling device  100 . Engagement and disengagement normally only occurs when shafts  106  and  120  are stationary. 
         [0030]      FIG. 2A  is a perspective view of a pin felt coupling device  200  in an uncoupled configuration in accordance with another exemplary embodiment of the present invention.  FIG. 2B  is a perspective view of coupling device  200  in a coupled configuration. In the exemplary embodiment, coupling device  200  includes a first flange  202  coupled to a distal end  204  of a first shaft  206 . First shaft  206  includes a longitudinal axis of rotation  208 . First flange  202  includes an inflatable torus  209  at least partially surrounding a circumferential periphery of first flange  202 . Torus  209  includes one or more radially extending pins  210  having a height  212  and a diameter  214  that extend radially away from a radially outward facing rim  215  of torus  209 . Although described as pins having a diameter, pins  210  can be embodied in pins, prongs, studs, or other projections and can have any shaped cross-section and diameter  214  may refer to, rather than a circular dimension, but rather a cross-sectional dimension substantially perpendicular to axis  208 . In the exemplary embodiment, height  212  is significantly greater than diameter  214 . 
         [0031]    Coupling device  200  also includes a second flange  216  coupled to a distal end  218  of a second shaft  220 . Second shaft  220  includes a longitudinal axis of rotation  222 . Second flange  216  includes one or more circumferentially extending raised sidewall  224  extending around a periphery  223  of a face  225  of flange  216 . In the exemplary embodiment, a receptive media  230  is positioned along a radially inner surface  226  of sidewall  224 . Receptive media  230  may be formed of, for example, but not limited to, felt, metal wool, and gel. 
         [0032]    During operation, first flange  202  and second flange  216  are positioned face-to-face a distance  232  apart. Distance  232  is selectable to permit an engagement of pins  210  and receptive media  230  to a coupled configuration of coupling device  200  (shown in  FIG. 2B ) where torus  209  is inflated, which increases a diameter of torus  209 . Distance  232  is also selectable to permit a disengagement of pins  210  and receptive media  230  to an uncoupled configuration of coupling device  200  (shown in  FIG. 2A ) where torus  209  is deflated, which decreases a diameter of torus  209 . Distance  232  may be selectively variable to permit withdrawal of one of first flange  202  and second flange  216  away from proximity to the other of first flange  202  and second flange  216 . Alternatively, distance  232  may be fixed, maintaining first flange  202  and second flange  216  in relatively close proximity. Receptive media  230  is formed of a material that is penetrable by pins  210  and sufficiently resilient to receive a rotational force in the circumferential direction from pins  210  and transfer the force to second flange  216 . Pins  210  engage receptive media  230  by penetrating a surface of receptive media  230  or by fitting into cavities  233  in surface  231 . In one embodiment, cavities  233  are formed in surface  231  complementary to pins  210 . In various embodiments, cavities  233  are formed in surface  231  by the engagement of pins  210  with surface  231 . For example, a pin  210  engaging surface  231  may dislocate a local portion of surface  231  to create an opening through which pin  210  is able to further penetrate surface  231  and slide into full engagement with media  230 . Dislocating the local portion and sliding past media  230  causes friction between pins  210  and media  230 , which defines an amount of axial force needed to fully engage pins  210  and media  230 . Pins  210  and media  230  are selected such that engagement and disengagement of pins  210  and media  230  results in a relatively minor amount of long term damage to either pins  210  or media  230  thereby providing a relatively long life and/or number of engagement/disengagement cycles. After engagement, one of shafts  206  or  220  can drive the other through coupling device  200 . Engagement and disengagement normally only occurs when shafts  206  and  220  are stationary. 
         [0033]      FIG. 3A  is perspective view of a pin felt coupling device  300  in an uncoupled configuration in accordance with still another exemplary embodiment of the present invention.  FIG. 3B  is a perspective view of coupling device  300  in a coupled configuration. In the exemplary embodiment, coupling device  300  includes a first arm assembly  302  coupled to a distal end  304  of a first shaft  306 . First shaft  306  includes a longitudinal axis of rotation  308 . First arm assembly  302  includes one or more radially outwardly extending arms  309 . One or more pins  310  having a height  312  and a diameter  314  extend away from a distal end  315  of arms  309  in a direction of rotation for coupling coupling device  300 . Although described as pins having a diameter, pins  310  can be embodied in pins, prongs, studs, or other projections and can have any shaped cross-section and diameter  314  may refer to, rather than a circular dimension, but rather a cross-sectional dimension substantially perpendicular to axis  308 . In the exemplary embodiment, height  312  is significantly greater than diameter  314 . 
         [0034]    Coupling device  300  also includes a second arm assembly  316  coupled to a distal end  318  of a second shaft  320 . Second shaft  320  includes a longitudinal axis of rotation  322 . Second arm assembly  316  includes one or more arms  324  extending radially outward from second arm assembly  316 . Arms  324  include pads  326  comprising a receptive media that is coupled to or formed with a distal end  329  of arms  324 . The receptive media of pads  326  is configured to receive pins  310  when one of first arm assembly  302  and/or second arm assembly  316  is rotated into engagement with the other. The receptive media is also configured to release pins  310  when one of first arm assembly  302  and/or second arm assembly  316  is rotated to disengage the other. The receptive media may be formed of, for example, but not limited to, felt, metal wool, and gel. 
         [0035]    During use, first arm assembly  302  and second arm assembly  316  are positioned face-to-face a distance  332  apart. Distance  332  is selectable to permit an engagement of pins  310  and the receptive media to a coupled configuration of coupling device  300  (shown in  FIG. 3B ). Distance  332  is also selectable to permit a disengagement of pins  310  and receptive media to an uncoupled configuration of coupling device  300  (shown in  FIG. 3A ). Distance  332  may be selectively variable to permit withdrawal of one of first arm assembly  302  and second arm assembly  316  away from proximity to the other of first arm assembly  302  and second arm assembly  316 . 
         [0036]    The receptive media is formed of a material that is penetrable by pins  310  and sufficiently resilient to receive a rotational force in the circumferential direction from pins  310  and transfer the force to second arm assembly  316 . Pins  310  engage the receptive media by penetrating a surface of the receptive media or by fitting into cavities  333  in a receptive media surface  331 . In one embodiment, cavities  333  are formed in surface  331  complementary to pins  310 . In various embodiments, cavities  333  are formed in surface  331  by the engagement of pins  310  with surface  331 . For example, a pin  310  engaging surface  331  may dislocate a local portion of surface  331  to create an opening through which pin  310  is able to further penetrate surface  331  and slide into full engagement with media. Dislocating the local portion and sliding past media causes friction between pins  310  and media, which defines an amount of axial force needed to fully engage pins  310  and media. Pins  310  and media are selected such that engagement and disengagement of pins  310  and media results in a relatively minor amount of long term damage to either pins  310  or media thereby providing a relatively long life and/or number of engagement/disengagement cycles. After engagement, one of shafts  306  or  320  can drive the other through coupling device  300 . 
         [0037]      FIG. 4  is an exploded view of a dual pin felt coupling device  400  in accordance with yet another exemplary embodiment of the present invention. In the exemplary embodiment, coupling device  400  includes a shaft  402 , a fixed cam  404 , a rotary cam  406 , an output rotor  408 , a receptive media  410 , a bias member  412 , a driver pin array  414 , and one or more engagement pins  416 . 
         [0038]      FIG. 5  is a perspective view of driver pin array  414  in accordance with an exemplary embodiment of the present invention. In the exemplary embodiment, driver pin array  414  includes a spring socket  502  and a plurality of pins  510  fixedly coupled to a shell  504 . 
         [0039]      FIG. 6  is a perspective view of a driver side of output rotor  408  in accordance with an exemplary embodiment of the present invention. In the exemplary embodiment, output rotor  408  includes receptive media  410  and a bearing  602 . 
         [0040]      FIG. 7  is a perspective view of a cam side of output rotor  408  in accordance with an exemplary embodiment of the present invention. In the exemplary embodiment, output rotor  408  includes receptive media  410 , bearing  602 , and an output arm  702 . 
         [0041]      FIG. 8  is a perspective view of rotary cam  406  in accordance with an exemplary embodiment of the present invention. In the exemplary embodiment, rotary cam  406  includes a lobe  802 . 
         [0042]      FIG. 9  is a perspective view of fixed cam  404  in accordance with an exemplary embodiment of the present invention. In the exemplary embodiment, fixed cam  404  includes a lobe  902 , a plurality of pins  910 , and a matrix  912  fixedly holding pins in a housing  914 . 
         [0043]      FIG. 10  is a perspective view of shaft  402  in accordance with an exemplary embodiment of the present invention. In the exemplary embodiment, shaft  402  includes a shaft collar  1002 . 
         [0044]      FIG. 11  is a perspective view of fully assembled pin felt coupling device  400  in an uncoupled configuration where shaft  402  is freely rotatable while holding output rotor  408  stationary.  FIG. 12  is a perspective view of fully assembled pin felt coupling device  400  in a coupled configuration where a rotation force applied to shaft  402  is transferred through pins  510  and receptive media  410 . In the exemplary embodiment, coupling device  400  includes shaft  402 , fixed cam  404 , rotary cam  406 , output rotor  408 , receptive media  410 , bias member  412 , and driver pin array  414  assembled onto shaft  402 . A double coupling is used to retain the rotational angle of output rotor  408 . Output rotor  408  is coupled to driver pin array  414  with a first pin felt coupling  1102  of double pin felt coupling device  400  and decoupled from fixed cam  404  with cam fixed pins  910  (as it would be normally attached to another part of the machine) cam by retracting a second pin felt coupling  1104 . There is overlap in this operation so that the rotation angle of output rotor  408  is retained because pins  416  are inserted into the driver side media  410  before they are completely removed from the fixed pin side media. 
         [0045]    In the un-operated position (shown in  FIG. 11 ), shaft  402  can be freely rotated with out changing the position of output rotor  408  which is held in position by pins on the fixed side. During operation, pins are retracted from the felt on the fixed side of the output rotor and inserted into the felt on the driver side (shown in  FIG. 12 ). During this operation the pins can be inserted into the driver side felt before they are completely withdrawn from the fixed side felt so that the rotary orientation of the output rotor is preserved. After the operation is complete rotation of the shaft will rotate the output rotor. 
         [0046]    A ratio of insertion force to torque capability of the coupling as well as the rotational accuracy depend on factors including for example, materials, number of pins and coupling size. The insertion force may be by mechanical means such as a cam or a lever. It could also be electromagnetic provided by a coil or provided by a fluid power cylinder, bellows or inflatable/deflatable flexible membrane or electrostatic. 
         [0047]    The forces that provide low resistance to pin insertion but higher resistance to orthogonal pin movement can be inherent in the properties of the receiving media such as a fiber media like felt or metal wool or may need to be activated by another controllable means. An example would be wax that would be activated to receive the pins with heat and then cooled to resist orthogonal motion. The activation may be required to insert the pins like the wax example or activation of a fluidized bed with air flow or the activation may be required to provide the orthogonal resistance such as turning on a magnetic coil to increase the viscosity of a fluid with magnetic particles suspended in it. Insertion could also be enhanced by vibration induced by mechanical or sonic means. 
         [0048]      FIG. 13  is a perspective view of a receptive flange  1200  in accordance with an exemplary embodiment of the present invention. Receptive flange  1200  may be used with flange  102  (shown in  FIG. 1 ), flange  216  (shown in  FIG. 2 ), and arm assembly  316  (shown in  FIG. 3 ). In the exemplary embodiment, receptive flange  1200  includes a U-shaped channel  1202  that includes a base  1204 , a first sidewall  1206  extending orthogonally away from a first edge  1208  of base  1204 , and a second sidewall  1210  extending orthogonally away from a second edge  1212  of base  1204  in the same direction as first sidewall  1206 . In the embodiment illustrated in  FIG. 12 , channel  1202  is represented in a linear configuration. However, it should be understood, in other embodiments, channel  1202  may be a circular member having sidewalls  1206  and  1210  extending circumferentially about a central axis wherein each of sidewalls  1206  and  1210  are concentric with respect to each other. 
         [0049]    A receptive media  1214  extends from a distal end  1216  of first sidewall  1206  to a distal end  1218  of second sidewall  1210 . In the exemplary embodiment, receptive media  1214  includes a plurality of closely-spaced rigid or semi-rigid members  1220 . Members  1220  may also be formed of a resilient material stretched taut between sidewalls  1206  and  1210 . In one embodiment, members  1220  are formed of an elongate member, for example, but not limited to, a thread, a string or cable fabricated of a material such as, but not limited to, aramid, ultra high molecular weight polyethylene (UHMWPE), or a polyhydroquinone-diimidazopyridine (M5) fiber that is wound around receptive flange  1200 . In the exemplary embodiment, each turn of members  1220  is in contact with each adjacent turn of member  1220 . Further, in other embodiments, members  1220  may be wound to form a plurality of layers with each layer of members  1220  overlapping members of adjacent layers. Members  1220  may be secured in place using an adhesive  1222  applied to outer surfaces of base  1204 , and sidewalls  1206  and  1210  prior to applying members  1220 . Alternatively, member  1220  may be coated with an adhesive  1224  prior to winding member  1220  around receptive flange  1200 . Adhesive  1224  may be activated after application using for example, but not limited to, heat, or a second part of a two part adhesive. 
         [0050]    Receptive media  1214  is configured to receive a plurality of pins  1226  extending from a flange (not shown) complementary to receptive flange  1200 . During operation, pins  1226  are advanced to engagement with member  1220  of receptive media  1214 . Pins  1226  tend to spread members  1220  apart and slide between members  1220 . A lateral force imparted by pins  1226  to members  1220  causes base  1204  to move in the direction of the applied force. For precision positioning applications using a smaller diameter member  1220  and/or pins  1226  tends to increase a resolution of a position of base  1204  with respect to the flange carrying pins  1226 . 
         [0051]    The above-described embodiments of a method and system of a shaft coupling that is engageable/disengagable and maintains positional or rotational accuracy between coupling halves provides a cost-effective and reliable means for transmitting rotational power. More specifically, the method and system described herein facilitate infinite rotational resolution and accurate repeatability of the shaft coupling. As a result, the method and system described herein facilitate transmitting rotational force from a first shaft to a second shaft in a cost-effective and reliable manner. 
         [0052]    An exemplary method and system for coupling two coaxial shafts are described above in detail. The apparatus illustrated is not limited to the specific embodiments described herein, but rather, components of each may be utilized independently and separately from other components described herein. Each system component can also be used in combination with other system components. 
         [0053]    This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.