Powered finger with locking rack mechanism

Abstract

This disclosure provides systems, apparatuses, and devices for a powered prosthetic digit. The disclosed devices restore prehension in a person with missing fingers or thumb by providing motor-driven extension and flexion, and opposition to forces in the extension direction via a pawl and locking rack ratchet mechanism, thereby allowing an individual to manipulate or stabilize objects. In one embodiment, a digit comprises a base configured to be removably couplable to an anchor, a first segment pivotably coupled to the base, and a second segment removably coupled to the first segment. The first segment comprises a rack with a plurality of rack teeth and a pawl with a nose configured to engage with the rack to prevent pivoting of the first segment in a rotational direction corresponding to extension of the prosthetic digit. The second segment comprises a drive gear operable to pivot the first segment with respect to the base.

We claim: 
     
         1 . A powered prosthetic digit having a lock, the powered prosthetic digit comprising:
 a base configured to be removably couplable to an anchor;   a first segment pivotably coupled to the base and positioned such that the lock prevents pivoting of the first segment in a rotational direction corresponding to extension of the powered prosthetic digit;   a positioning gear pivotably coupled to the first segment; and   a second segment coupled to the first segment, the second segment having a drive gear configured to operatively engage with the drive gear to pivot the first segment with respect to the base.   
     
     
         2 . The powered prosthetic digit of  claim 1 , wherein the second segment is configured to be removably couplable to the first segment. 
     
     
         3 . The powered prosthetic digit of  claim 1 , wherein the powered prosthetic digit is configured to resist a force greater than 222 N applied to the powered prosthetic digit in a direction tending to cause extension of the powered prosthetic digit. 
     
     
         4 . The powered prosthetic digit of  claim 1 , wherein the powered prosthetic digit is configured to output a grasping power of less than 200 mW at a distal end of the prosthetic distal segment. 
     
     
         5 . The powered prosthetic digit of  claim 1 , wherein the lock is a ratcheting lock and comprises a rack having a plurality of rack teeth and a pawl having a nose configured to engage with the rack teeth to prevent pivoting of the first segment in the rotational direction corresponding to extension of the powered prosthetic digit. 
     
     
         6 . The powered prosthetic digit of  claim 5 , wherein the first segment further comprises a lock link coupled between the positioning gear and the pawl to rotate the pawl upon rotation of the positioning gear, and wherein the rotation of the positioning gear causes the pawl to transition between (a) a locked state in which the nose is engaged with the rack teeth and (b) an unlocked state in which the nose is disengaged from the rack teeth. 
     
     
         7 . The powered prosthetic digit of  claim 5 , wherein the first segment further comprises a rocker arm positioned between the positioning gear and the pawl to allow rotation the pawl upon rotation of the rocker arm, and wherein the rotation of the rocker arm causes the pawl to transition between (a) a locked state in which the nose is engaged with the rack teeth and (b) an unlocked state in which the nose is disengaged from the rack teeth. 
     
     
         8 . The powered prosthetic digit of  claim 5 , wherein rotation of the positioning gear causes the pawl to transition to the locked state when an opposition force is applied to the powered prosthetic digit. 
     
     
         9 . The powered prosthetic digit of  claim 1 , wherein the first segment further comprises a first linkage with a proximal end pivotably coupled to the base and a second linkage with a proximal end pivotably coupled to the base and extending in a crossed configuration with the first linkage, wherein the first linkage comprises the rack. 
     
     
         10 . The powered prosthetic digit of  claim 9 , further comprising a connector plate pivotably coupled to a distal end of the first linkage and a distal end of the second linkage, wherein the connector plate, the first linkage, the second linkage, and the base form a four-bar linkage configuration. 
     
     
         11 . The powered prosthetic digit of  claim 10 , wherein the second segment is removably couplable to the connector plate. 
     
     
         12 . The powered prosthetic digit of  claim 10 , wherein the four-bar linkage is configured to rotate the connector plate at a greater angular velocity with respect to the base than the angular velocity of the first segment with respect to the base during articulation of the powered prosthetic digit. 
     
     
         13 . The powered prosthetic digit of  claim 1 , wherein the second segment further comprises a motor configured spin the drive gear to pivot the first segment with respect to the base. 
     
     
         14 . The powered prosthetic digit of  claim 13 , wherein the drive gear is a worm screw, and wherein rotation of the worm screw causes a change in position along the positioning gear. 
     
     
         15 . The powered prosthetic digit of  claim 13 , wherein the motor is electrically coupled to an electronics control board having a microprocessor configured to control the motor in response to one or more of a signal, algorithm, function, and command. 
     
     
         16 . The powered prosthetic digit of  claim 13 , wherein the second segment further comprises a battery electrically coupled to the electronics control board and configured to power the motor. 
     
     
         17 . The powered prosthetic digit of  claim 13 , wherein the motor is configured to rotate the first segment with respect to the base at an angular velocity of at least 140 deg/sec. 
     
     
         18 . The powered prosthetic digit of  claim 13 , wherein the motor is configured to apply a grasping force through the powered prosthetic digit of less than 2 N. 
     
     
         19 . The powered prosthetic digit of  claim 1 , wherein the second segment comprises a fairing. 
     
     
         20 . A powered prosthetic digit, comprising:
 a base configured to be removably couplable to an anchor;   a first segment pivotably coupled to the base and having a rack with a plurality of rack teeth and a pawl with a nose configured to engage with the rack to prevent pivoting of the first segment in a rotational direction corresponding to extension of the powered prosthetic digit; and   a second segment coupled to the first segment, the second segment having a drive gear operable to pivot the first segment with respect to the base.   
     
     
         21 . The powered prosthetic digit of  claim 20 , wherein the second segment is configured to be removably couplable to the first segment. 
     
     
         22 . The powered prosthetic digit of  claim 20 , wherein the powered prosthetic digit is configured to resist a force greater than 222 N applied to the powered prosthetic digit in a direction tending to cause extension of the powered prosthetic digit. 
     
     
         23 . The powered prosthetic digit of  claim 20 , wherein the powered prosthetic digit is configured to output a grasping power of less than 200 mW at a distal end of the prosthetic distal segment. 
     
     
         24 . The powered prosthetic digit of  claim 20 , further comprising a positioning gear pivotably coupled to the first segment, wherein the positioning gear is configured to operatively engage with the drive gear to pivot the first segment with respect to the base. 
     
     
         25 . The powered prosthetic digit of  claim 24 , wherein the drive gear is a worm screw, and wherein rotation of the worm screw causes a change in engagement position along the positioning gear. 
     
     
         26 . The powered prosthetic digit of  claim 20 , wherein the first segment further comprises a first linkage with a proximal end pivotably coupled to the base and a second linkage with a proximal end pivotably coupled to the base and extending in a crossed configuration with the first linkage, wherein the first linkage comprises the rack. 
     
     
         27 . The powered prosthetic digit of  claim 26 , further comprising a connector plate pivotably coupled to a distal end of the first linkage and a distal end of the second linkage, wherein the connector plate, the first linkage, the second linkage, and the base form a four-bar linkage configuration. 
     
     
         28 . The powered prosthetic digit of  claim 27 , wherein the second segment comprises a fairing having a grip portion, and wherein the second segment is removably couplable to the connector plate. 
     
     
         29 . The powered prosthetic digit of  claim 27 , wherein the four-bar linkage is configured to rotate the connector plate at a greater angular velocity with respect to the base than the angular velocity of the first segment with respect to the base during articulation of the powered prosthetic digit. 
     
     
         30 . The powered prosthetic digit of  claim 20 , wherein the second segment further comprises a motor configured spin the drive gear to pivot the first segment with respect to the base. 
     
     
         31 . The powered prosthetic digit of  claim 30 , wherein the motor is electrically coupled to an electronics control board having a microprocessor configured to control the motor in response to one or more of a signal, algorithm, function, and command. 
     
     
         32 . The powered prosthetic digit of  claim 30 , wherein the second segment further comprises a battery electrically coupled to the electronics control board and configured to power the motor. 
     
     
         33 . The powered prosthetic digit of  claim 30 , wherein the motor is configured to rotate the first segment with respect to the base at an angular velocity of at least 140 deg/sec. 
     
     
         34 . The powered prosthetic digit of  claim 30 , wherein the motor is configured to apply a grasping force through the powered prosthetic digit of less than 2 N. 
     
     
         35 . The powered prosthetic digit of  claim 24 , wherein:
 the first segment further comprises a lock link coupled between the positioning gear and the pawl,   the lock link is operable to rotate the pawl upon rotation of the positioning gear, and   the rotation of the positioning gear causes the pawl to transition between a locked state, in which the nose is engaged with the rack teeth, and an unlocked state, in which the nose is disengaged from the rack teeth.   
     
     
         36 . The powered prosthetic digit of  claim 24 , wherein:
 the first segment further comprises a rocker arm positioned between the positioning gear and the pawl,   the rocker arm is operable to allow rotation the pawl upon rotation of the rocker arm, and   the rotation of the rocker arm causes the pawl to transition between a locked state, in which the nose is engaged with the rack teeth, and an unlocked state, in which the nose is disengaged from the rack teeth.