Abstract:
A prosthetic glove worn over damaged fingers or over a prosthetic hand having flexible fingers. The glove articulates the fingers with multiple shape memory alloy wires and includes a cooling system for each shape memory alloy wire.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to an actuator for a finger to control movement of the finger in response to an input signal and to related methods. The finger is moved by contraction of a shape memory alloy wire. The actuator can move a biological finger not moveable by finger muscles or can move a prosthetic finger. 
       BACKGROUND OF THE INVENTION 
       [0002]    Loss of finger function severely affects an individual&#39;s ability to perform manual tasks. 
         [0003]    Prior prosthetic devices have restored limited hand function to individuals unable to control finger movement. These devices use robotic technologies and actuate fingers through use of motors or other mechanisms. 
         [0004]    Prosthetic devices have used shape memory alloy wires made of Nitinol or like materials as actuating members. The Nitinol wire forms part of an electrical circuit that selectively flows current through the Nitinol wire to heat the wire to a transition temperature that contracts the wire. The wire contraction actuates a member joined to a prosthetic or otherwise uncontrollable finger to move the finger. 
         [0005]    The use of shape memory alloy wires to actuate prosthetic devices is difficult. A long Nitinol wire is required to generate a sufficient contraction stroke for finger actuation. Heated Nitinol wire only shrinks about 4% of its unheated length. The long wire length necessitates prior prosthetic devices to include long support portions to accommodate the long shape memory alloy wires. 
         [0006]    Another problem with prior prosthetic devices is reliance on radiation cooling of the hot, contracted wire below the transition temperature to return the wire to its original length prior to another contraction. Radiation cooling slows lengthening and delays finger contraction. 
         [0007]    Accordingly, there is a need for a compact actuator for a finger that uses shape memory alloy wire which rapidly cools and re-lengthens the contracted wire. 
       SUMMARY OF THE INVENTION 
       [0008]    The invention is an actuator worn by an individual with a prosthetic finger or an otherwise uncontrollable finger to control movement of the finger. Tendon or tension wires are connected to the finger. An increase in the tension in one wire opens the finger. Tension in another wire closes the finger. 
         [0009]    The end of each tendon wire away from the finger is connected to a shape memory alloy (Nitinol) actuating wire. Each actuating wire extends from the tendon wire through a hollow tube to an anchor to form a wire and tube assembly that is wound in a compact coil. The ends of the actuating wire are connected to an electrical circuit which, in response to a signal, flows current through the wire to heat the wire to a transition temperature in order to shorten the wire and tension the tendon wire for resultant movement of the finger. 
         [0010]    After heating and shortening of the wire, the wire is rapidly re-lengthened by gas cooling. This is achieved by flowing a gas, such as carbon dioxide, into the coiled tube and along the wire to quickly cool the wire below the transition temperature, re-lengthen the wire and prepare the wire for subsequent shortening in response to another input signal and current flow through the wire. 
         [0011]    Actuation of a wire to flex a finger in one direction pulls out a previously retracted and cooled wire used to move the finger in the opposite direction to lengthen the wire for reheating and contraction in response to another signal. 
         [0012]    The actuator may include sensors on the fingertip to actuate circuits to heat and retract Nitinol wires actuating the finger. 
         [0013]    Individual wire and tube actuators may be wound around a cylindrical support that surrounds the wrist supporting the finger or may be stacked on the back of a hand supporting the finger. The actuators may be wound in flat spirals. 
         [0014]    A number of wire and tube actuators may be provided for the finger so that the finger is moved independently about finger joints in response to signals from finger sensors. A sensor on the end of the finger actuates an actuator or actuators to flex the finger inwardly in a gripping motion. Actuators may also move a finger laterally to either side in response to signals. In the absence of a flex signal, a control system automatically releases or straightens the finger. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a side view of the invention on a hand; 
           [0016]      FIG. 2  is a top view of  FIG. 1 ; 
           [0017]      FIG. 3  is a detail view of invention support plates and tension wires; 
           [0018]      FIG. 4  is a representational view of the actuator with the tube and wire unwound; 
           [0019]      FIGS. 5 ,  6 ,  7 , and  8  are detail views of a distal support member; 
           [0020]      FIGS. 9 ,  10  and  11  are detail views of a medial support member; 
           [0021]      FIGS. 12 ,  13 , and  14  detail views of a proximal support member; 
           [0022]      FIGS. 15 and 16  are perspective and top views of a casing assembly; 
           [0023]      FIG. 17  is a sectional view taken along line  17 - 17  of  FIG. 16 ; 
           [0024]      FIG. 18  is a perspective view of a wrist-surrounding casing assembly; 
           [0025]      FIG. 19  is a view showing the wrist-surrounding casing assembly taken along line  19 - 19  of  FIG. 18 ; 
           [0026]      FIG. 20  is a sectional view of the wrist-surrounding casing assembly taken along line  20 - 20  of  FIG. 19 ; 
           [0027]      FIG. 21  is a sectional view of the wrist-surrounding casing assembly along line  21 - 21  of  FIG. 20 ; and 
           [0028]      FIG. 22  is a sectional view of the wrist-surrounding casing assembly taken along line  22 - 22  of  FIG. 21 . 
       
    
    
     DESCRIPTION OF THE INVENTION 
       [0029]    As illustrated in  FIG. 1 , first embodiment prosthetic glove  10  includes a finger sheath  12  with flat distal support member or plate  14 , flat medial support member or plate  16  and flat proximal support member or plate  18  secured to the top of the sheath. Palm portion  20  of glove  10  covers the palm supporting the finger in sheath  12 . 
         [0030]    Support members  14 ,  16  and  18  may be plates as shown in profile in  FIG. 1  and in alternate views in  FIGS. 9 ,  10 ,  11   12 ,  13  and  14 . The plates are bound to the top of finger sheath  12  by bands  22  attached to each plate and surrounding finger sheath  12 . 
         [0031]    In an alternative embodiment, each support member  14 ,  16  or  18  may form one wall of an open ended square tube  24  as illustrated in  FIGS. 5-8 . Tube  24  includes flat sidewalls  26  and  28  joining support  14  and flat bottom wall  30 . In member  14 , sensor slots  32  are provided in the lead end of the member  14  of walls  26  and  28 . The slot in wall  28  is not illustrated. Pressure sensors may be mounted in slots  32 . 
         [0032]    Two pairs of tendon wire-mounting holes  34  and  36  are located on opposite sides of support  14 . Hinge mounting holes  38  extend through the proximal end of the member. 
         [0033]    Medial support member  16  includes two hinge mounting holes  40  on the distal end thereof, a tendon wire mounting hole  42  and a pair of tendon wire mounting holes  44 . Holes  42  and  44  are on the centerline of the member. Band attachment slots  46  extend along opposite sides of the support member. 
         [0034]    Hinge  48  is connected to support members  14  and  16  at holes  38  and  40  to permit relative rotation of the members during flexing of the finger and sheath  12 . 
         [0035]    The three support members  14 ,  16  and  18  are mounted on finger sheath  12  as illustrated in  FIG. 1  so that member  14  overlies a finger&#39;s distal phalanges bone, member  16  overlies a finger&#39;s middle phalanges bone and member  18  overlies a finger&#39;s proximal phalanges bone. A band  22  may be secured to member  14 ,  16  or  18  by band attachment slots  46 . 
         [0036]    In embodiments in which support members  14 ,  16  or  18  form parts of square tubes  24 , as shown with a support member  14  in  FIGS. 5-8 , sheath  12  extends into the interior of the tubes so that the support member overlies the top of the finger. 
         [0037]    Finger sheath  12  is closed and opened to grip and release objects by selectively tensioning and relaxing tendon wires  50 ,  52 ,  54  and  56  connected to members  14 ,  16  and  18  as illustrated in  FIGS. 1 ,  2  and  3 . Each tendon wire is connected to a wire actuator  58  having a coiled dielectric tube  60  and a shape memory wire  62  in the tube. An electrical circuit flows current through the shape memory alloy wire to heat and contract the wire and a gas supply assembly  64  flows cooling gas through the tube to cool and elongate the heated wire  62 . The end of the shape memory alloy wire away from the tendon wire is fixed in position. The other end of the shape memory alloy wire is connected to the tendon wire to tension and relax the tendon wire. 
         [0038]    Individual wire actuators  58 , each with a coil of Nitinol shape memory alloy wire in a coiled tube, are located in housing  66 , secured to the back of the glove  10  above the palm of the glove. See  FIG. 1 . 
         [0039]    The housing  66  surrounds each coiled wire actuator  58  for each tendon wire  68  attached to a member  14 ,  16  or  18 . Each wire actuator  58  has a coiled dielectric tube  60  with a fixed closed end  70 , a coiled length  72  and a fixed open end  74 . A length of memory alloy wire  62  extends the length of the interior of the tube from a fixed wire end  76  at tube fixed closed end  70 , along the tube, past open end  74 , which may be fixed, to wire end  76  outside the tube where the end of the memory shape alloy wire is joined to the proximal end  78  of a tendon or tension wire  68  wire outside of the tube at a turnbuckle or length-adjusting device  80 .  FIG. 4  shows an uncoiled wire actuator  58 . 
         [0040]      FIG. 2  illustrates the three support members  14 ,  16  and  18 , the tendon wires connected to the members and a housing  66  containing multiple wire actuators  58 . Each wire actuator  58  is wound into a coil made up of one or more coil loops. The actuator may be wound into a flat coil having co-planar loops as illustrated in  FIGS. 1 and 2 . The actuator may be wound into a cylindrical coil having circular loops arranged adjacent to each other as illustrated in  FIG. 20 . 
         [0041]    Tendon wire  50  contracts members  14  and  16  to close the finger to grip an object. Tendon wire  52  extends from turnbuckle or length-adjusting device  80  adjacent housing  66  under proximal member  18  and under members  16  and  14  to an end secured to mounting holes  34  in member  14 . A branch  82  of tendon wire  50  is joined to tendon wire  50 , extends under member  16  and is connected to member  16  at hole  42 . 
         [0042]    Tendon wire  52  opens members  14  and  16  and extends from turnbuckle or length-adjusting device  80  adjacent housing  66  over member  18 , and over member  16  and  14  to an end attached to holes  36  in member  14 . A tendon wire branch  84  joins tendon wire between members  16  and  18 , extends over member  16  and is connected to holes  44  in member  16 . 
         [0043]    Tendon wire  54  extends from turnbuckle or length-adjusting device  80  adjacent housing  66  across the top of member  18  and is connected to the top of the member at holes  86 . Tendon wire  56  extends from turnbuckle or length-adjusting device  80  adjacent housing  66  under member  18  and is connected to the bottom of member  18  at holes  88 . Tensioning of tendon wire  54  rotates member  18  upwardly to open the finger. Tensioning of tendon wire  56  moves the member  18  downwardly to close the finger. 
         [0044]    The finger sheath is moved laterally by tensioning tendon wires  90  or  92 . Tendon wire  90  extends from a turnbuckle or length-adjusting device  80  adjacent housing  66  over member  18  and is connected to the top of the member at hole  94 . Tendon wire  92  extends from a turnbuckle or length-adjusting device  80  adjacent housing  66  over member  18  and is connected to the top of the member at hole  96 . Tendon wires  90  and  92  extend from assembly  66  to member  18  at angles so that tensioning of either wire by the assembly exerts a torque on the finger sheath tending to rotate the finger sheath to one side or the other side, depending upon which wire  90  or  92  is tensioned. See  FIGS. 3 and 13 . 
         [0045]    Housing  66  includes casing assembly  94  shown in  FIGS. 15-17 . Assembly  94  includes a central cylindrical post  96 , an outer cylindrical wall  98  and a cylindrical recess  100  between the post and wall. Wire access openings  102  extend through wall  98  to recess  100 . Casing assembly  94  includes a number of vertically stacked coiled wire actuators  58 . 
         [0046]    In each actuator  58 , the fixed wire end  76  of Nitinol wire  62  is anchored to casing  94 . The other end of the wire  62  extends outwardly from wire actuator  58  through an opening  102  and is connected to a tendon wire  68  at turnbuckle or length-adjusting device  80 . See  FIGS. 2 and 4 . 
         [0047]    Shape memory alloy wire  62  is surrounded by a flexible dielectric tube  60  to permit the flowing of a cooling gas through the tube and over the wire. The tube may be made of rubber, plastic or a like material. Gas inlet port  104  is located proximate fixed wire end  76  and joins tube interior  106  to gas supply assembly  64 . The open tube end  74  forms a gas outlet port. Gas supply assembly  64  includes a high-pressure source of cooling gas  108  that releases a cooling gas  110  through solenoid valve  112  and pressure regulator  114 . Cooling gas  110  may be carbon dioxide. Actuation of valve  112  flows cooling gas  110  along tube interior  106  and shape memory alloy wire  62  to cool and lengthen the heat contracted wire and to outlet port  74 . Thermocouple  112  is mounted to tube  60  mid-way along the length of the tube. The thermocouple is connected to a controller  114  for wire  62  as described below. 
         [0048]    The ends of each shape memory alloy wire adjacent to fixed end  76  and device  80  are connected to an electricity source  118  and micro-controller  114  at contacts  117  and  119 . 
         [0049]    Controller  114  selectively flows electricity through contacts  117  and  119  along wire shape memory wire from end  78  to end  76 . The entire length of the shape memory wire  62  is heated, thus allowing generation of a maximum contractive stroke for the wire. 
         [0050]    Contraction and release of a finger using prosthetic glove  10  will now be described. 
         [0051]    When the sensor in slot  30  in the bottom wall of tube  20  engages an object, a signal is sent to micro-controller  114  to contract the Nitinol wires connected to finger contraction tendon wires  50  and  56 . Flow of electricity through the Nitinol wires connected to tendon wires  50  and  56  contracts the wires to contract members  14 ,  16  and  18 . Electricity is flowed through the Nitinol wires until the wires are heated sufficiently to contract. 
         [0052]    The wires may be heated by direct current, alternating current or a current pulse-train proportional to the force exerted on the pressure sensor. When the Nitinol wires are fully contracted, the micro-controller turns off the current flow through the wires. If the wires are not fully contracted when the sensor is deactivated and the current is turned off, a subsequent signal from the pressure sensor will reactuate the micro-controller to flow a current through the wires to further contract the wires and contract the finger. 
         [0053]    The Nitinol wires are heated during contraction. Each wire has a maximum contraction stroke. In order to prepare heated, contracted wires for a future contraction stroke it is necessary to cool the wires below the activation temperature. This must be done rapidly in order to permit repeated actuation of the finger. 
         [0054]    When a Nitinol wire has been fully contracted and the actuation signal to the micro controller to flow electricity through the wire is deactivated, thermocouple  112  senses the temperature of Nitinol wire  62  in tube  60 . If the temperature of the wire is above the transition temperature for the wire, the micro-controller sends a signal to solenoid valve  112  to flow a cooling gas such as carbon dioxide through the length of tube  60 , and past wire  62  to cool the wire below the actuation temperature. Flow of the cooling gas is stopped when the sensed temperature of the wire is below the actuation temperature. 
         [0055]    Tendon wires  52  and  54  are likewise tensioned by flowing electricity through their respective Nitinol wires to move members  14 ,  16  and  18  in upward, opening movement to release the grip of the finger. Opening of the finger stretches out the previously contracted Nitinol wires for tendon wires  50  and  56 . Likewise, contraction of the finger stretches out the previously contracted Nitinol wires for tendon wires  52  and  54 . 
         [0056]    Wires  90  and  92  are likewise tensioned to rotate the finger sheath from side to side. Movement of the sheath to one side stretches out the Nitinol wire for moving the sheath to the opposite side. 
         [0057]      FIGS. 18  though  22  illustrate a second embodiment of the invention having a wrist-surrounding casing assembly  122 . Casing assembly  122  has cylindrical body  124  defining a cylindrical passage  126  extending from an assembly rear opening  128  to an assembly front opening  130  though which a user places their wrist or arm  132 . Cylindrical body  124  has an outer cylindrical wall  134  and an inner cylindrical wall  136 . 
         [0058]    Inflatable cuff  138  having cuff walls  140  is mounted on inner cylindrical wall  136  in passage  126  and is inflated to surround and comfortably fit the assembly on the user&#39;s arm  132 . Outer cylindrical wall  134  and inner cylindrical wall  136  define casing assembly interior cylindrical cavities  142 . 
         [0059]      FIGS. 20 and 21  shows a coiled cylindrical tube  60  and wire  50  positioned in one interior cylindrical cavity  142 . Additional actuators  50  are positioned in cavities  142  spaced along assembly  122 . 
         [0060]    Coiled actuator  58  is positioned in cylindrical cavity  142  by affixing the ends of tube  60  to mounts  144  located proximate tube closed end  70  and tube open end  74  as shown in  FIG. 20 . Port  104  is located proximate tube closed end  70  and connects tube interior  106  to cooling gas supply assembly  64  as previously described. 
         [0061]    Memory alloy wire  62  extends from fixed wire end  76  along tube  60  through tube open end  74  and is joined to tendon wire  68  at turnbuckle or length-adjusting device  80 . Tendon wire  68  extends about pulley  146  and out of interior cylindrical cavity  142  through assembly exit hole  148 . 
         [0062]      FIG. 20  shows memory alloy wire  62  heated above the transition temperature to a fully contracted length. As memory alloy wire  62  is cooled below its transition temperature, it will lengthen. Memory alloy wire stroke distance  150  shows the contraction distance for wire  62 , illustrated as the distance moved by turnbuckle or length-adjusting device  80  from a lengthened, cooled position  154  to a contracted, heated position  152 . 
         [0063]    Walls  156  separate adjoining cylindrical cavities  142 . 
         [0064]    The second embodiment of the invention functions like the first embodiment to tension tendon wires.