Actuator system with a motor assembly and latch for extending and flexing a joint

Abstract

An actuator system for assisting extension of a biological joint is provided with a motor assembly, a rotary-to-linear mechanism, and an extension stop. The rotary-to-linear mechanism includes a screw that accepts rotational output of the motor assembly, and a nut that cooperates with the screw to convert rotational movement of the screw to linear movement of the nut. The extension stop is driven by linear movement of the nut in an extension direction to cause extension of the biological joint. The motor assembly, the rotary-to-linear mechanism and the extension stop cooperate to allow unpowered flexion of the joint. The system is configured without a flexion stop, and is configured such that the nut cannot drive the joint in a flexion direction. Methods of use are also disclosed.

1 . An actuator system for extending and flexing a joint, comprising:
 a motor assembly that provides a rotational output;   a rotary-to-linear mechanism including a screw that accepts the rotational output of the motor assembly, and a nut that cooperates with the screw to convert rotational movement of the screw to linear movement of the nut; and   a latch that selectively allows at least one of the following: linear movement of the nut in an extension direction to cause extension of the joint, and a linear movement of the nut in a flexion direction to cause flexion of the joint.   
     
     
         2 . The actuator system of  claim 1 , further comprising a moving rail that moves linearly to cause flexion and extension of the joint; wherein the latch is mounted to the moving rail. 
     
     
         3 . The actuator system of  claim 2 , wherein the latch includes an extension stop surface that translates linear movement of the nut in an extension direction into linear movement of the moving rail in the extension direction. 
     
     
         4 . The actuator system of  claim 3 , wherein linear movement of the moving rail in an extension direction causes an extension of the joint. 
     
     
         5 . The actuator system of  claim 3 , wherein the moving rail includes a flexion stop that translates linear movement of the nut in a flexion direction into linear movement of the moving rail in a flexion direction. 
     
     
         6 . The actuator system of  claim 3 , wherein the latch is movable between an engaged position that allows the nut to apply force against the extension stop surface of the latch and a disengaged position that prevents the nut from applying force against the extension stop surface of the latch. 
     
     
         7 . The actuator system of  claim 6 , wherein the latch is movable between the engaged position and disengaged position by sliding relative to the nut to engage and disengage the nut. 
     
     
         8 . The actuator system of  claim 7 , further comprising a switch coupled to the latch, wherein the latch is selectable between the engaged position and disengaged position by rotating the switch. 
     
     
         9 . The actuator system of  claim 2 , wherein the latch includes a flexion stop surface that translates linear movement of the nut in a flexion direction into linear movement of the moving rail in the flexion direction. 
     
     
         10 . The actuator system of  claim 9 , wherein linear movement of the moving rail in a flexion direction causes a flexion of the joint. 
     
     
         11 . The actuator system of  claim 9 , wherein the moving rail includes an extension stop that translates linear movement of the nut in an extension direction into linear movement of the moving rail in an extension direction. 
     
     
         12 . The actuator system of  claim 9 , wherein the latch is movable between an engaged position that allows the nut to apply force against the flexion stop surface of the latch and a disengaged position that prevents the nut from applying force against the flexion stop surface of the latch. 
     
     
         13 . The actuator system of  claim 12 , wherein the latch is movable between the engaged position and disengaged position by sliding relative to the nut to engage and disengage the nut. 
     
     
         14 . The actuator system of  claim 13 , further comprising a switch coupled to the latch, wherein the latch is selectable between the engaged positing and disengaged position by rotating the switch. 
     
     
         15 . The actuator system of  claim 2 , wherein the latch includes:
 an extension stop surface that translates linear movement of the nut in an extension direction into linear movement of the moving rail in the extension direction; and   a flexion stop surface that translates linear movement of the nut in a flexion direction into linear movement of the moving rail in the flexion direction.   
     
     
         16 . The actuator system of  claim 15 , wherein linear movement of the moving rail in an extension direction causes an extension of the joint; and linear movement of the moving rail in a flexion direction causes a flexion of the joint. 
     
     
         17 . The actuator system of  claim 15 , wherein the latch is movable between an engaged position that allows the nut to apply force against the latch and a disengaged position that prevents the nut from applying force against the latch. 
     
     
         18 . The actuator system of  claim 17 , wherein the latch is movable between the engaged position and disengaged position by sliding relative to the nut to engage and disengage the nut. 
     
     
         19 . The actuator system of  claim 18 , further comprising a switch coupled to the latch, wherein the latch is selectable between the engaged position and disengaged position by rotating the switch. 
     
     
         20 . The actuator system of  claim 15 , wherein the extension stop surface of the latch and the flexion stop surface of the latch are located such that they allow significant movement of the moving rail back and forth between the extension stop surface and the flexion stop surface without moving the nut or back-driving the multi-motor assembly. 
     
     
         21 . The actuator system of  claim 1 , wherein the motor assembly includes:
 a drive shaft that provides rotational output,   a first motor subsystem having a first output shaft and a first transmission connecting the first output shaft to the drive shaft, and   a second motor subsystem having a second output shaft and a second transmission coupling the second output shaft to the drive shaft.   
     
     
         22 . An actuator system for extending and flexing a joint, comprising:
 a motor assembly that provides a rotational output;   a rotary-to-linear mechanism including a screw that accepts the rotational output of the motor assembly, and a nut that cooperates with the screw to convert rotational movement of the screw to linear movement of the nut;   a moving rail having an extension stop that translates linear movement of the nut in an extension direction into extension of the joint; and   a latch that selectively couples the nut and the moving rail and that includes a flexion stop surface, wherein the latch is movable between a disengaged position that prevents the nut from applying force against the flexion stop surface of the latch and an engaged position that allows the nut to apply force against the flexion stop surface of the latch thereby translating linear movement of the nut in a flexion direction into a flexion of the joint.   
     
     
         23 . A method of assisting extension of a joint during a movement cycle, the method comprising:
 attaching an actuator system to a joint of a user;   during one portion of the cycle, driving an actuator of the system in an extension direction to deliver a high force to the joint at a relatively low speed; and   during another portion of the cycle, allowing a limb associated with the joint to move freely by driving the actuator with a smaller force and at a higher speed.   
     
     
         24 . The method of  claim 23 , wherein the user does not back-drive the actuator during the free moving portion of the cycle. 
     
     
         25 . The method of  claim 23 , wherein the actuator comprises at least one motor that provides a rotational output, and a rotary-to-linear mechanism that functions to convert the rotational output from the motor into a linear movement that ultimately extends the joint of the user. 
     
     
         26 . The method of  claim 25 , wherein the actuator comprises two motors, and the rotary-to-linear mechanism converts the rotational output from both of the motors into the linear movement. 
     
     
         27 . The method of  claim 26 , wherein one of the motors is used to deliver high forces to the joint at relatively low speeds, and the other motor is used to deliver smaller forces at higher speeds.