US20160367383A1 - Lockable Finger System and Related Methods - Google Patents
Lockable Finger System and Related Methods Download PDFInfo
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- US20160367383A1 US20160367383A1 US15/185,873 US201615185873A US2016367383A1 US 20160367383 A1 US20160367383 A1 US 20160367383A1 US 201615185873 A US201615185873 A US 201615185873A US 2016367383 A1 US2016367383 A1 US 2016367383A1
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- prosthetic
- finger
- digit
- linkage
- prosthetic digit
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
- A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
- A61F2/50—Prostheses not implantable in the body
- A61F2/54—Artificial arms or hands or parts thereof
- A61F2/58—Elbows; Wrists ; Other joints; Hands
- A61F2/583—Hands; Wrist joints
- A61F2/586—Fingers
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
- A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
- A61F2/50—Prostheses not implantable in the body
- A61F2/54—Artificial arms or hands or parts thereof
- A61F2/58—Elbows; Wrists ; Other joints; Hands
- A61F2/583—Hands; Wrist joints
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
- A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
- A61F2/50—Prostheses not implantable in the body
- A61F2002/5072—Prostheses not implantable in the body having spring elements
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
- A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
- A61F2/50—Prostheses not implantable in the body
- A61F2/54—Artificial arms or hands or parts thereof
- A61F2/58—Elbows; Wrists ; Other joints; Hands
- A61F2/583—Hands; Wrist joints
- A61F2/586—Fingers
- A61F2002/587—Thumbs
Definitions
- the application relates generally to prosthetic devices and in particular, to a lockable finger for a prosthesis.
- Prosthetic devices for individuals with upper limb loss include myoelectric devices (which are controlled by electromyographic (EMG) signals from muscle) and body-powered prostheses (in which movement of a remaining joint, e.g., shoulder flexion, is physically coupled to the prosthetic joint through a harness and Bowden cabling system).
- a Bowden cabling system in general, is a flexible cable system which transfers a mechanical force and operates inside a hollow tube.
- Bowden cabling systems are used to operate a body-powered device. For example, the user wears a harness across his or her shoulders. The Bowden cable attaches at one end to the harness and the opposite end attaches to the prosthesis (hand or hook or some other device used to manipulate objects in the user's environment).
- a Bowden cable can be useful for this application because the hollow tube surrounding the moving cable protects the user's skin from the friction of the moving cable.
- the terminal device of a prosthesis is the means by which a user directly interacts with and manipulates their environment. It is the device worn at the end of the prosthesis used to interact with the surrounding environment, and often is considered part of a prosthesis. Examples of terminal devices includes hooks and hands. Terminal devices may alternatively take on many unique and specialized shapes. For example, there are several different special terminal devices for playing sports such as baseball or golf. Thus, the functional utility of the terminal device often plays a role in determining the user's overall ability to perform necessary or desired activities.
- the human hand is a highly complex mechanism with many joints.
- the MCP joint is the “Metacarpophalangeal joint”—these joints are what we commonly refer to as our knuckles.
- the PIP joint is the “proximal interphalangeal joint”—these are the joints we think of when we think of bending our fingers, the middle joint between the knuckles and the small joint at the finger tips.
- Body-powered terminal devices include prehensors (e.g., split-hooks and other non-anthropomorphically shaped terminal devices) and hands.
- Body-powered prehensors and hands are available in one of two modes. Voluntary open (VO) devices are opened by actuation of the Bowden cable and have a default closed position, whereas voluntary close (VC) devices have a default open position and are closed by actuation of the Bowden cable. Both VO and VC devices provide advantages and disadvantages to the user, depending on the task at hand.
- VO Voluntary open
- VC voluntary close
- body-powered prehensors are considered more functional than body-powered hands. See C. M. Fryer, et al., “Body-Powered Components,” in Atlas of Amputations and Limb Deficiencies , D. G. Smith, et al., Eds., 3rd ed Rosemont, Ill.: American Academy of Orthopaedic Surgeons, 2004, pp. 131-143 (hereinafter, “Fryer”). Body-powered hands often do not look natural, and functionally they can be slow, heavy, and awkward, and provide a weak grip force. They do not open very wide, and the user must expend a lot of energy to operate them.
- VO and VC hands are commercially available—such as the APRL VC hand; the Becker Lock-Grip hand, and the Sierra VO hand.
- VO hands are seldom used due to their poor pinch forces (as explained in the Fryer reference) and the relaxed position of the VC hands is an open grasp, which is not cosmetically appealing.
- these body-powered prosthetic hands are very bulky in the palm section, which further impacts cosmesis.
- the added weight of a cosmetic shell makes the weight of body-powered hands (300-450 g) heavier than certain prehensors (113-354 g), and similar to certain myoelectric hands (250-440 g).
- substantial user force can be lost due to deformation of the cosmetic glove.
- Body-powered fingers typically have a single axis of rotation, located at the metacarpophalangeal (MCP) joint.
- MCP metacarpophalangeal
- Such a design requires a pre-flexed proximal interphalangeal (PIP) joint, which does not result in a cosmetically appealing palm-flat posture.
- PIP proximal interphalangeal
- grasps may be described as a static posture with movement of a subset of fingers. For example, in cylindrical grip, all of the fingers move together. In three-jaw chuck grip, the fourth and fifth digits are fully flexed, and only the second and third digits move. In trigger-grip, the third, fourth, and fifth digits are fully flexed, and only the second digit moves.
- Fine manipulation tasks usually involve the first finger and thumb, or the first finger, second finger, and thumb.
- the three-jaw-chuck grip (which uses the thumb, middle, and index fingers) provided by existing prostheses serves as a compromise between power and precision grasps.
- the fourth and fifth fingers do not contribute functionally to fine manipulation; they are present principally for cosmesis in most available hands, and secondarily used for object stabilization.
- body-powered devices they do not transmit force from the Bowden cable to objects, but they often get in the way of many precision grasps, as the palm and fingers of the hand are typically positioned in the user's line of sight to the object being grasped. This can prevent visual feedback, unless the user adopts an unnatural posture.
- a grasping device that is able to maintain a static posture while select digits are actuated could achieve a substantial subset of important grasps, without the need for multiple actuators.
- a prosthetic grasping device only requires actuation for digit flexion—it is not necessary to actuate digit extension, which can be achieved passively using springs.
- a prosthetic device may comprise a prosthetic digit, an engagement portion, and a stopping portion.
- the engagement portion is capable of engaging with the stopping portion to lock the prosthetic digit in a position of flexion in response to a force applied to the prosthetic digit.
- FIG. 2 shows a perspective view of a prosthetic hand arranged in a “fine pinch” position with the middle finger, ring finger, and pinky finger locked in a position of flexion.
- FIG. 3 shows a perspective view of a prosthetic hand arranged in a “three-jaw-chuck” position.
- FIG. 4 shows a perspective view of a prosthetic hand arranged in a “three-jaw-chuck” position with the ring finger and the pinky finger locked in a position of flexion.
- FIG. 5 shows a perspective view of a prosthetic hand arranged in a “palm flat” position.
- FIG. 6 shows a perspective view of a prosthetic hand arranged in a “cylindrical grasp” position.
- FIG. 7 shows a side view of one embodiment of a lockable finger.
- FIGS. 8 a , 8 b , and 8 c show three different configurations of the lockable finger shown in FIG. 7 .
- FIG. 9 shows a second embodiment of a lockable finger.
- FIG. 11 shows a perspective view of the lockable finger shown in FIG. 9 .
- FIGS. 12 a , 12 b , and 12 c show side views of the lockable finger shown in FIG. 9 as it is being unlocked.
- FIGS. 13 a and 13 b show one embodiment of a lockable finger with a contoured linkage.
- FIGS. 14 and 15 show one embodiment of a lockable finger in use with a hand, where the hand is configured to operate in voluntary-open (VO) mode.
- VO voluntary-open
- FIGS. 16 and 17 show one embodiment of a lockable finger in use with a hand, where the hand is configured to operate in a voluntary-close (VC) mode.
- VC voluntary-close
- FIG. 1 shows a view of a prosthetic hand 10 having a thumb 15 , an index finger 20 , a middle finger 30 , a ring finger 40 , and a pinky finger 50 .
- the hand 10 is arranged in a position known as “fine pinch,” where the index finger 20 and the thumb 15 pinch together in an effort to grasp a relatively small object, such as a pen.
- the middle finger 30 , the ring finger 40 , and the pinky finger 50 are not used to grasp the object.
- fingers 30 , 40 , and 50 can even get in the way of the user's attempt to use the “fine pinch” grasp to pick up the object. For instance, they can block the view of the object from the user, or physically interfere with the object.
- FIG. 2 shows a view of the same prosthetic hand 10 , but with fingers 30 , 40 , and 50 each locked in a position of flexion. Locking the fingers 30 , 40 , and 50 when the hand is in the fine pinch position allows the user to more accurately grasp the pen or other object, including helping the user see the object he or she is trying to grasp.
- FIGS. 3 and 4 show the hand 10 in a “three-jaw-chuck” position, where both the index finger 20 and the middle finger 30 pinch together with the thumb 15 .
- a user may use the three-jaw-chuck position, for instance, when the user wants to grasp an item like a pen or silverware, which requires precision but some extra force and stability.
- none of the digits is locked, which may lead to the same difficulties as described above; namely, that the unlocked digits may get in the way or block a view of the object.
- the ring finger 40 and the pinky finger 50 are locked when the hand 10 is in the three-jaw-chuck position, which gives the user a more accurate grip of the object he or she is trying to grasp.
- a lockable finger may be employed on many different kinds of gripping devices, such as prosthetic hands. At least one lockable finger may be used in a gripping device, such as a prosthetic hand, that operates in a voluntary-close (“VC”) mode or a voluntary-open (“VO”) mode. At least one lockable finger may be used in a gripping device, such as a prosthetic hand, that operates in both a VC mode and a VO mode, for instance by switching between the VC mode and the VO mode.
- VC voluntary-close
- VO voluntary-open
- a lockable finger may be employed on myoelectric prosthetic hands, where electrical signals generated by the user are used to help control the myoelectric prosthetic hand.
- a myoelectric prosthetic hand are described in further detail in U.S. patent application Ser. No. 14/614,256 to J. Sensinger and J. Lipsey, titled Modular and Lightweight Myoelectric Prosthesis Components and Related Methods, for instance, which is incorporated by reference.
- FIG. 7 displays a side view of one embodiment of a lockable finger.
- finger 100 is positioned adjacent to the latch 108 .
- the finger 100 may have a surface 109 and notch sides 110 .
- the surface 109 may be rounded.
- the finger 100 may be configured to receive a locking force 134 from an external source.
- the locking force 134 may be provided by the user, for instance, by pushing on the finger 100 using his or her other hand, by pushing the finger 100 against an object (such as a wall, a table, or some other object in the user's environment).
- the locking force 134 may also be provided by other means, such as by another person, or by some other method.
- a latch 108 may be positioned adjacent to the proximal finger linkage 100 .
- the latch 108 may comprise a spring-loaded cam.
- the latch 108 pivots about a pivot 112 .
- a spring 111 may provide a torque on the latch 108 in the clockwise direction indicated by arrow 111 t and a spring 116 may provide a torque on the finger 100 in the counterclockwise direction indicated by arrow 114 t .
- the surface 109 comes into contact with a portion 107 of the latch 108 .
- the portion 107 may protrude from the latch 108 .
- the surface 109 may push the portion 107 in a direction that causes the rotation of the latch 108 about the latch pivot 105 .
- the finger 100 continues to rotate in a clockwise direction around pivot 114 until the surface 109 no longer is in contact with the latch 108 .
- a spring 112 may cause the latch 108 to rotate in a clockwise direction, such that the portion 107 or another portion of the latch 108 moves to a position underneath the finger 100 .
- the finger 100 is sufficiently flexed by the locking force 134 so that it is in a position of full flexion (defined below)
- the latch 108 and the finger 100 have become positioned with respect to each other so that it the latch 108 is positioned underneath the notch sides 110 of the finger 100 .
- the spring 116 causes the finger 100 to rotate counterclockwise around pivot 114 to return to extension.
- the notch sides 110 press against the latch 108 , therefore preventing the finger 100 from extending.
- the latch 108 serves as a stopping element, and in the embodiment shown in FIG. 7 , the engagement of the finger 100 with latch 108 locks the finger 100 in a position of flexion.
- the latch 108 may be disengaged manually from the finger 100 .
- the latch 108 may be disengaged by pressing an unlock mechanism 136 that is coupled to the latch 108 .
- the unlock mechanism 136 may push against the latch 108 , causing the latch 108 to rotate away from the finger 100 , such that the latch 108 is no longer positioned underneath the notch sides 110 of the finger 100 .
- the unlock mechanism may be a protruding portion of the latch itself.
- the unlock mechanism 136 may comprise a bias spring (not shown) that disengages the latch 108 from the finger 100 .
- the bias spring may be balanced against the torsion spring on the latch. As the unlock mechanism 136 is not under high stress, it can be miniaturized.
- the spring 116 actuates the finger 100 to a position that allows it to be actuated by the power source 150 .
- the default position of the finger 100 is one of extension (in other words, a “voluntary-close” hand)
- the spring 116 returns the finger 100 to a default extended position.
- the finger 100 is released from the locked position by spring 116 but remains in a semi-flexed position.
- the spring 116 biases the finger 100 towards extension so as to maintain the position of the actuator linkage 104 at the bottom of the actuator slot 102 .
- the finger 100 may be configured so that it can remain in a locked position while at least one other finger on the same hand is free to move.
- This feature may be important to the user, for instance, if the finger 100 and the at least one other finger are actuated or otherwise moved using the a common linkage. In this embodiment, having one locked finger does not prevent the other one or more fingers from actuating freely.
- This feature may also be important for the user to move the finger 100 out of the way during an activity that does not require use of the finger 100 , such as activities involving trigger grip, fine pinch, or 3-jaw-chuck.
- This feature may also be important for the user if the user desires to lock the finger 100 to assist with a particular type of grasp. For example, the thumb may be locked to assist with the user grasping an object. Alternately, the thumb may be locked to move it out of the way for activities that do not require the thumb.
- an actuator slot 102 is provided in the finger 100 and is configured to receive an actuator linkage 104 .
- the actuator linkage 104 may be coupled to a common link 140 which in turn may be coupled to a power source 150 .
- the arrow 106 in FIG. 7 indicates the direction of the actuation force that the power source 150 provides to the actuator linkage 104 through the common link 140 .
- the power source 150 may be an externally powered motor, a Bowden cable attached to the user's body, or another powered mechanism.
- One embodiment achieves movement of unlocked fingers through the use of a slot in the proximal finger linkage at the attachment point of the actuator linkage. Forces on the proximal finger linkage only occur when the actuator linkage is at the end of the slot, ensuring larger surface areas and thus acceptable material pressures. Locking one or more fingers does not interfere with movement of the other fingers in either VO or VC modes, since the actuator link is free to move throughout the range of motion of the slot. Similarly, locking the fingers does not interfere in any way with the ability of the user to obtain proprioceptive input during use of the device, since the actuator link still moves throughout the entire range of motion and is not impeded in any way. As shown in FIG.
- an actuation slot 102 in the actuation path enables the digit to move through its range of motion to a flexed position without inhibiting the actuator.
- Manually flexing the finger to a lockable position allows latch 108 to engage with the notch 110 on the proximal finger linkage 100 .
- Latch 108 is biased by a spring 112 to close so that once the digit reaches the locked position, latch 108 will automatically engage with notch 110 and statically lock the digit in a flexed position.
- FIGS. 8 a , 8 b , and 8 c shows three different representations of the finger 100 .
- Each representation shows the finger 100 in a different configuration during a different stage of use.
- spring 116 is represented as a spring attached to a wall, rather than as a torsion spring as shown in FIG. 7 , so that the force it provides on the finger 100 can be more easily visually compared to the locking force 134 .
- FIG. 8 a shows the finger 100 actuated to the maximum extent of the possible range of the motion of flexion. This position is known as “full flexion.”
- full flexion occurs at a greater range of motion than can be actuated by the power source 150 . This prevents the power source 150 from accidentally locking the digit.
- the finger 100 may be configured to reach full flexion just beyond the point necessary for it to engage with the latch 108 . In order for full flexion to occur at a greater range of motion than can be actuated by the power source 150 , the finger 100 may be constructed so that it can flex beyond the functional range of movement.
- the finger 100 may be constructed so that it can flex up to 110 degrees. In this way, the power source 150 is limited to flexing the finger 100 to 90 degrees and then may reach a hard stop. At this point, the user can still manually flex the finger to 110 degrees of flexion, at which point the finger locks.
- the actuator linkage 104 is not bottomed out in the slot 102 . In this embodiment, it indicates that in order to engage the latch 108 , the finger 100 must be flexed beyond the capabilities of the power source 150 .
- the actuator linkage 104 For the power source 150 to be moving the finger 100 into flexion, the actuator linkage 104 must be bottomed out in the slot 102 . However, since the actuator linkage 104 is not in the bottom of the slot 102 , FIG. 8 a is showing the finger 100 being flexed manually beyond the capabilities of the power source 150 .
- FIG. 8 b shows the finger 100 locked in a position of flexion. Once the finger 100 has been pushed into the position of full flexion, the latch 108 flips into place, engaging with the notch sides 110 to prevent extension of the finger 100 . This position can be accomplished by the locking force 134 , rather than by the actuator force 106 .
- FIG. 8 c shows the finger 100 locked in a position of flexion, with the actuator linkage 104 free to move throughout its normal range of motion in the actuation slot 102 in the proximal digit linkage 100 . Locking of the finger 100 does not prevent the at least one other finger (including a thumb) from being actuated through common link 140 and power source 150 .
- a four-bar linkage may be inserted into the fingers, in order to kinematically couple PIP flexion to MCP flexion. In this manner the fingers remain relatively flat during palm-flat, yet achieve the required PIP flexion angle for chuck-grasp.
- the four-bar linkage maximizes pinch force while still achieving a kinematically acceptable motion profile, within the constraints of an anthropomorphic hand envelope.
- FIG. 9 Another embodiment of a locking finger is shown in FIG. 9 .
- the finger 200 may have a proximal phalanx 201 and a distal phalanx 202 .
- an upper portion of the distal phalanx 202 may be configured in a cam shape, so that a portion 232 of the distal phalanx 202 extends from the surface of the distal phalanx 202 and allows for the receipt of a pin 230 that connects the distal phalanx 202 to the locking linkage 226 .
- the user pushes on the distal phalanx 202 to lock the finger 200 .
- the finger 200 may lock due to engagement between the locking linkage 226 and the stopping element 208 .
- the stopping element 208 may be located on the proximal phalanx 201 .
- FIG. 11 shows a perspective view of the finger 200 locked in a position of flexion, where the locking linkage 226 is prevented from further flexion by stopping element 208 .
- FIG. 11 also shows wall 252 , which provides common support as shown for the components of the finger 200 .
- Another wall on the opposite side of the stopping element 208 and locking linkage 226 may be provided, but is omitted from FIG. 11 so that the reader can better see the internal arrangement of the finger 200 .
- At least one passive spring provides a torque that keeps the finger in a locked position.
- spring 224 provides a torque in a counterclockwise direction.
- the torque from spring 224 attempts to extend the proximal phalanx 201 .
- the locking linkage 226 creates a clockwise rotation about pin 230 , due to the fixed radius of pin 230 from PIP joint 220 .
- This clockwise rotation of the distal phalanx 202 moves the locking linkage 226 towards extension, where it collides with the stopping element 208 .
- FIGS. 12 a , 12 b , and 12 c display three side views of the finger 200 being unlocked.
- a force 260 may be applied to a top surface of the proximal phalanx 201 .
- the force 260 may be applied by the user's other hand, or by an object in the user's environment.
- the force 260 causes the finger 200 to flex.
- the force 260 causes the proximal phalanx 201 to rotate in a clockwise direction, which rotates the locking linkage 226 to the singularity.
- FIG. 12 a a force 260 may be applied to a top surface of the proximal phalanx 201 .
- the force 260 may be applied by the user's other hand, or by an object in the user's environment.
- the force 260 causes the finger 200 to flex.
- the force 260 causes the proximal phalanx 201 to rotate in a clockwise direction, which rotates the locking linkage 226 to
- 12 b shows the locking linkage 226 at the point of singularity, at which point the PIP spring 222 pulls the distal phalanx 202 outward and MCP spring 224 pushes the proximal phalanx 201 towards extension.
- the springs 222 and 224 therefore work together, in the directions indicated by the arrows shown around the MCP joint 114 and the PIP joint 120 , respectively, to push the finger 200 back into the unlocked position shown in FIG. 12 c.
- the locking portion may physically configured to avoid catching or otherwise interfering with other portions of the system.
- the locking linkage 226 may be contoured so that its movement between extension and flexion of the finger 200 does not interfere with the actuator linkage 204 or the support member 206 .
- Equivalent support members are shown in the profile views FIGS. 14-16 .
- the locking linkage 226 is contoured to receive support member 206 when the finger 200 is extended.
- the same contour of the locking linkage receives the actuator linkage 204 when the finger 200 is extended.
- a four-bar mechanism is used in each finger, and a fifth bar in each finger is used to transmit torque from the body-powered mechanism, such as a Bowden cable, to the finger.
- These fifth bars may be rigidly linked across the fingers, and connected by some method to a VO/VC switch mechanism, allowing the hand to function either as a VO or a VC hand.
- Each of the actuator links is attached to the output of the VO/VC mechanism, such that the output of the VO/VC mechanism is a linkage.
- the actuator links are attached through a linear bushing to ensure that each of the fingers moves at the same rate.
- the VO/VC mechanism is in turn attached to the Bowden cable or external motor, which provides the input to the VO/VC mechanism.
- FIGS. 14 and 15 show embodiments of a locking finger in use with a hand 300 , where the hand 300 is configured to operate in voluntary-open (VO) mode.
- the hand 300 is shown coupled to an actuation lever 310 .
- Finger 320 and finger 330 each have a slot 320 s and 330 s , respectively.
- the actuation lever 310 is coupled to the fingers 320 and 330 by a transmission. Actuation of the actuation lever 310 causes rotation of the actuation lever 310 about a central pivot, causing switch 360 to rotate in a counter clockwise direction.
- switch 360 acts on pin 362 and link 364 to transfer an upward force through pin 366 to the coupler linkage 368 .
- the coupler linkage 368 is connected by pin 370 to driver linkages 340 , which actuate the fingers 320 and 330 .
- the driver linkage 340 is coupled to finger 320 by a pin 320 p and is coupled to finger 330 by a pin 330 p .
- Pin 320 p is positioned in the slot 320 s and pin 330 p is positioned in the slot 330 s .
- each pin 320 p and 330 p allows its respective finger 320 and 330 to move by releasing it from VO mode and allowing it to extend.
- extension may be provided by one or more springs coupled to each finger.
- Finger 330 has a similar spring around its joint, but because the finger 330 is locked, instead of that spring acting on finger 330 to cause extension, pin 330 s instead slides through slot 330 p , and comes to rest at the top of slot 330 p as shown in FIG. 15 .
- FIGS. 16 and 17 show an embodiment of a locking finger in use with a hand 300 , where the hand is configured to operate in a voluntary-close (VC) mode.
- VC voluntary-close
- the finger 330 is locked in a position of flexion, and the pin 330 p is at the top of the slot 330 s .
- the finger 320 is in a position of extension due to torque provided by a spring about main pivot 345 .
- a force 350 is applied to flex the finger 320 .
- the pin 320 p moves to the bottom of slot 320 s to flex the finger 320 , while the pin 330 p slides through the bottom of the slot 330 s as the finger 330 is already locked in a position of flexion
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- Health & Medical Sciences (AREA)
- Orthopedic Medicine & Surgery (AREA)
- Transplantation (AREA)
- Cardiology (AREA)
- Oral & Maxillofacial Surgery (AREA)
- Engineering & Computer Science (AREA)
- Biomedical Technology (AREA)
- Heart & Thoracic Surgery (AREA)
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Abstract
A prosthetic device comprising a first prosthetic digit, a first engagement portion, and a first stopping portion, wherein the first engagement portion is capable of engaging with the first stopping portion to lock the first prosthetic digit in a position of flexion in response to a force applied to the first prosthetic digit.
Description
- This patent claims priority to U.S. Provisional Patent Application No. 62/182,253, filed on Jun. 19, 2015, entitled “Lockable Finger System and Related Methods.” The entirety of U.S. Provisional Patent Application No. 62/182,253 is incorporated herein by reference.
- This invention was made with government support under H133G120059 awarded by the National Institute for Disability and Rehabilitation Research (NIDRR). The government has certain rights in the invention.
- The application relates generally to prosthetic devices and in particular, to a lockable finger for a prosthesis.
- An estimated 41,000 people in the United States have lost use of one or both of their upper limbs through amputation at or above wrist level. See K. Ziegler-Graham, et al., “Estimating the prevalence of limb loss in the United States: 2005 to 2050,” Archives of Physical Medicine and Rehabilitation, vol. 89, pp. 422-429, March 2008. Loss of the arm and hand profoundly limits everyday activities such as dressing and eating, affects social interactions and personal relationships, and can threaten basic independence. In particular, difficulty in grasping and holding objects impedes leisure activities and may prevent a return to employment. The most effective treatment for limb loss is replacement of the missing limb with a prosthetic device. Most upper limb amputations are caused by trauma and occur in relatively young, active individuals, who need prostheses that effectively replace functional dexterity of the lost hand.
- Prosthetic devices for individuals with upper limb loss include myoelectric devices (which are controlled by electromyographic (EMG) signals from muscle) and body-powered prostheses (in which movement of a remaining joint, e.g., shoulder flexion, is physically coupled to the prosthetic joint through a harness and Bowden cabling system). A Bowden cabling system, in general, is a flexible cable system which transfers a mechanical force and operates inside a hollow tube. In prosthetics, Bowden cabling systems are used to operate a body-powered device. For example, the user wears a harness across his or her shoulders. The Bowden cable attaches at one end to the harness and the opposite end attaches to the prosthesis (hand or hook or some other device used to manipulate objects in the user's environment). The user then moves his or her shoulders (typically scapular retraction/protraction) to create tension in the cable which results in movement in the terminal device. A Bowden cable can be useful for this application because the hollow tube surrounding the moving cable protects the user's skin from the friction of the moving cable.
- The terminal device of a prosthesis is the means by which a user directly interacts with and manipulates their environment. It is the device worn at the end of the prosthesis used to interact with the surrounding environment, and often is considered part of a prosthesis. Examples of terminal devices includes hooks and hands. Terminal devices may alternatively take on many unique and specialized shapes. For example, there are several different special terminal devices for playing sports such as baseball or golf. Thus, the functional utility of the terminal device often plays a role in determining the user's overall ability to perform necessary or desired activities.
- The human hand is a highly complex mechanism with many joints. The MCP joint is the “Metacarpophalangeal joint”—these joints are what we commonly refer to as our knuckles. The PIP joint is the “proximal interphalangeal joint”—these are the joints we think of when we think of bending our fingers, the middle joint between the knuckles and the small joint at the finger tips. There are different classifications of common grasps that the hand uses when performing activities of daily living. One distinction is the difference between power and precision grasps. One study has shown that daily usage of these two types of grasps is fairly equal. See J. Z. Zheng, et al., “An investigation of grasp type and frequency in daily household and machine shop tasks,” presented at the IEEE International Conference on Robotics and Automation, 2011. Examples of functional hand grasps include 3-jaw chuck, fine-pinch, trigger, and cylindrical grasps. Examples of precision grapes include fine pinch, trigger, and 3-jaw chuck. Examples of power grasps include cylindrical grasp and “power” grasp (like a fist). Users of prosthetics can use power grasps, for example, for tasks like holding heavy objects, holding drinking glasses, or positioning a jar to open.
- Most myoelectric prostheses are electrically powered by batteries and rely on limit switches, potentiometers, force sensitive resistors, or myoelectric sensors for control inputs. Currently available myoelectrically controlled hands are cosmetically appealing and can apply high pinch force, but are quite heavy, are not robust, and are very expensive. Recent myoelectric hands such as the iLimb ultra (Touch Bionics) and the Bebionic 3 hand (SteeperUSA) have achieved a variety of grasps by powering each finger in the hand. These hands can accomplish several grasps, including power grip, key grip, 3-jaw-chuck, and fine pinch; however, in order to accomplish these grasps multiple actuators are required to control each finger individually, which adds weight to the hand and increases its size.
- Body-powered terminal devices include prehensors (e.g., split-hooks and other non-anthropomorphically shaped terminal devices) and hands. Body-powered prehensors and hands are available in one of two modes. Voluntary open (VO) devices are opened by actuation of the Bowden cable and have a default closed position, whereas voluntary close (VC) devices have a default open position and are closed by actuation of the Bowden cable. Both VO and VC devices provide advantages and disadvantages to the user, depending on the task at hand.
- In general, body-powered prehensors are considered more functional than body-powered hands. See C. M. Fryer, et al., “Body-Powered Components,” in Atlas of Amputations and Limb Deficiencies, D. G. Smith, et al., Eds., 3rd ed Rosemont, Ill.: American Academy of Orthopaedic Surgeons, 2004, pp. 131-143 (hereinafter, “Fryer”). Body-powered hands often do not look natural, and functionally they can be slow, heavy, and awkward, and provide a weak grip force. They do not open very wide, and the user must expend a lot of energy to operate them.
- Both VO and VC hands are commercially available—such as the APRL VC hand; the Becker Lock-Grip hand, and the Sierra VO hand. However, VO hands are seldom used due to their poor pinch forces (as explained in the Fryer reference) and the relaxed position of the VC hands is an open grasp, which is not cosmetically appealing. In addition, these body-powered prosthetic hands are very bulky in the palm section, which further impacts cosmesis. The added weight of a cosmetic shell makes the weight of body-powered hands (300-450 g) heavier than certain prehensors (113-354 g), and similar to certain myoelectric hands (250-440 g). Finally, during pinch grips, substantial user force can be lost due to deformation of the cosmetic glove. These functional and cosmetic issues together result in low user-acceptance rates for available body-powered hands (see Fryer).
- Currently available body-powered hands provide a single degree of movement, actuated through a Bowden cable that drives all of the fingers together. In some devices, movement of the thumb is coupled to movement of the fingers, in others the fourth and fifth fingers remain stationary, or their linkages are compliant, for example they are made of a compliant rubber or are biased by a spring, rather than being rigid (such as hard plastic is rigid). In all cases, only a single grasp can be obtained.
- Body-powered fingers typically have a single axis of rotation, located at the metacarpophalangeal (MCP) joint. Such a design requires a pre-flexed proximal interphalangeal (PIP) joint, which does not result in a cosmetically appealing palm-flat posture.
- However, it is important to note that many grasps may be described as a static posture with movement of a subset of fingers. For example, in cylindrical grip, all of the fingers move together. In three-jaw chuck grip, the fourth and fifth digits are fully flexed, and only the second and third digits move. In trigger-grip, the third, fourth, and fifth digits are fully flexed, and only the second digit moves.
- Fine manipulation tasks usually involve the first finger and thumb, or the first finger, second finger, and thumb. The three-jaw-chuck grip (which uses the thumb, middle, and index fingers) provided by existing prostheses serves as a compromise between power and precision grasps. The fourth and fifth fingers do not contribute functionally to fine manipulation; they are present principally for cosmesis in most available hands, and secondarily used for object stabilization. In body-powered devices, they do not transmit force from the Bowden cable to objects, but they often get in the way of many precision grasps, as the palm and fingers of the hand are typically positioned in the user's line of sight to the object being grasped. This can prevent visual feedback, unless the user adopts an unnatural posture.
- Thus a grasping device that is able to maintain a static posture while select digits are actuated could achieve a substantial subset of important grasps, without the need for multiple actuators. In addition, a prosthetic grasping device only requires actuation for digit flexion—it is not necessary to actuate digit extension, which can be achieved passively using springs.
- In one embodiment, a prosthetic device may comprise a prosthetic digit, an engagement portion, and a stopping portion. The engagement portion is capable of engaging with the stopping portion to lock the prosthetic digit in a position of flexion in response to a force applied to the prosthetic digit.
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FIG. 1 shows a perspective view of a prosthetic hand arranged in a “fine pinch” position. -
FIG. 2 shows a perspective view of a prosthetic hand arranged in a “fine pinch” position with the middle finger, ring finger, and pinky finger locked in a position of flexion. -
FIG. 3 shows a perspective view of a prosthetic hand arranged in a “three-jaw-chuck” position. -
FIG. 4 shows a perspective view of a prosthetic hand arranged in a “three-jaw-chuck” position with the ring finger and the pinky finger locked in a position of flexion. -
FIG. 5 shows a perspective view of a prosthetic hand arranged in a “palm flat” position. -
FIG. 6 shows a perspective view of a prosthetic hand arranged in a “cylindrical grasp” position. -
FIG. 7 shows a side view of one embodiment of a lockable finger. -
FIGS. 8a, 8b, and 8c show three different configurations of the lockable finger shown inFIG. 7 . -
FIG. 9 shows a second embodiment of a lockable finger. -
FIGS. 10a, 10b, and 10c show side view stages of the lockable finger shown inFIG. 9 as it is locked in a position of flexion. -
FIG. 11 shows a perspective view of the lockable finger shown inFIG. 9 . -
FIGS. 12a, 12b, and 12c show side views of the lockable finger shown inFIG. 9 as it is being unlocked. -
FIGS. 13a and 13b show one embodiment of a lockable finger with a contoured linkage. -
FIGS. 14 and 15 show one embodiment of a lockable finger in use with a hand, where the hand is configured to operate in voluntary-open (VO) mode. -
FIGS. 16 and 17 show one embodiment of a lockable finger in use with a hand, where the hand is configured to operate in a voluntary-close (VC) mode. - The locking aspects of the embodiments described here may be utilized in a variety of prostheses. Examples include those described in U.S. patent application Ser. Nos. 14/030,095, 14/614,187, 14/614,231, and 14/614,256, all of which are incorporated by reference.
- Referring to the drawings, embodiments of the device are illustrated and indicated numerically in the accompanying figures.
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FIG. 1 shows a view of aprosthetic hand 10 having athumb 15, anindex finger 20, amiddle finger 30, aring finger 40, and apinky finger 50. Thehand 10 is arranged in a position known as “fine pinch,” where theindex finger 20 and thethumb 15 pinch together in an effort to grasp a relatively small object, such as a pen. As shown inFIG. 1 , themiddle finger 30, thering finger 40, and thepinky finger 50 are not used to grasp the object. In certain situations,fingers -
FIG. 2 shows a view of the sameprosthetic hand 10, but withfingers fingers -
FIGS. 3 and 4 show thehand 10 in a “three-jaw-chuck” position, where both theindex finger 20 and themiddle finger 30 pinch together with thethumb 15. A user may use the three-jaw-chuck position, for instance, when the user wants to grasp an item like a pen or silverware, which requires precision but some extra force and stability. InFIG. 3 , none of the digits is locked, which may lead to the same difficulties as described above; namely, that the unlocked digits may get in the way or block a view of the object. InFIG. 4 , thering finger 40 and thepinky finger 50 are locked when thehand 10 is in the three-jaw-chuck position, which gives the user a more accurate grip of the object he or she is trying to grasp. - In various embodiments, each finger (including the thumb) may be locked in a position of flexion, and unlocked from that position, independently of the other fingers. This allows one or more fingers to be locked while the other fingers are unlocked, as shown in
FIGS. 1-4 , while also allowing for all fingers to be unlocked (for example, as shown inFIG. 5 , where thehand 10 is shown in the “palm flat” position and inFIG. 6 , where thehand 10 is shown in the “cylindrical grasp” position). - A lockable finger may be employed on many different kinds of gripping devices, such as prosthetic hands. At least one lockable finger may be used in a gripping device, such as a prosthetic hand, that operates in a voluntary-close (“VC”) mode or a voluntary-open (“VO”) mode. At least one lockable finger may be used in a gripping device, such as a prosthetic hand, that operates in both a VC mode and a VO mode, for instance by switching between the VC mode and the VO mode. Embodiments of a VO/VC device are described in further detail in U.S. patent application Ser. No. 14/030,095 to J. Sensinger, titled Gripping device with Switchable Opening Modes, for instance, which is incorporated by reference. Additionally, a lockable finger may be employed on myoelectric prosthetic hands, where electrical signals generated by the user are used to help control the myoelectric prosthetic hand. Embodiments of a myoelectric prosthetic hand are described in further detail in U.S. patent application Ser. No. 14/614,256 to J. Sensinger and J. Lipsey, titled Modular and Lightweight Myoelectric Prosthesis Components and Related Methods, for instance, which is incorporated by reference.
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FIG. 7 displays a side view of one embodiment of a lockable finger. As shown inFIG. 7 ,finger 100 is positioned adjacent to thelatch 108. Thefinger 100 may have asurface 109 and notch sides 110. As shown inFIG. 7 , thesurface 109 may be rounded. Thefinger 100 may be configured to receive a lockingforce 134 from an external source. The lockingforce 134 may be provided by the user, for instance, by pushing on thefinger 100 using his or her other hand, by pushing thefinger 100 against an object (such as a wall, a table, or some other object in the user's environment). The lockingforce 134 may also be provided by other means, such as by another person, or by some other method. - A
latch 108 may be positioned adjacent to theproximal finger linkage 100. In one embodiment, thelatch 108 may comprise a spring-loaded cam. Thelatch 108 pivots about apivot 112. In one embodiment, aspring 111 may provide a torque on thelatch 108 in the clockwise direction indicated byarrow 111 t and aspring 116 may provide a torque on thefinger 100 in the counterclockwise direction indicated byarrow 114 t. When a lockingforce 134 is applied to thefinger 100, thefinger 100 engages with thelatch 108 to lock thefinger 100 in a position of flexion. The force bias introduced by thespring 116 also prevents thefinger 100 from flexing or extending independently of actuation, but it may be overpowered by the lockingforce 134. In the embodiment shown inFIG. 7 , when the lockingforce 134 is applied to thefinger 100, if the torque provided by the lockingforce 134 is greater thetorque 114 t, thefinger 100 begins to rotate aboutpivot 114. (Spring 116 and the other springs displayed in the figures with a dashed lines may be torsion springs or representations of other springs known in the art.) - As the
finger 100 rotates about thepivot 114, thesurface 109 comes into contact with aportion 107 of thelatch 108. In one embodiment, theportion 107 may protrude from thelatch 108. When thesurface 109 comes into contact with theportion 107, thesurface 109 may push theportion 107 in a direction that causes the rotation of thelatch 108 about thelatch pivot 105. As the lockingforce 134 continues to be applied to thefinger 100, thefinger 100 continues to rotate in a clockwise direction aroundpivot 114 until thesurface 109 no longer is in contact with thelatch 108. Once thesurface 109 is no longer in contact with thelatch 108, aspring 112 may cause thelatch 108 to rotate in a clockwise direction, such that theportion 107 or another portion of thelatch 108 moves to a position underneath thefinger 100. When thefinger 100 is sufficiently flexed by the lockingforce 134 so that it is in a position of full flexion (defined below), thelatch 108 and thefinger 100 have become positioned with respect to each other so that it thelatch 108 is positioned underneath the notch sides 110 of thefinger 100. When the lockingforce 134 is no longer applied, thespring 116 causes thefinger 100 to rotate counterclockwise aroundpivot 114 to return to extension. However, the notch sides 110 press against thelatch 108, therefore preventing thefinger 100 from extending. In this way, thelatch 108 serves as a stopping element, and in the embodiment shown inFIG. 7 , the engagement of thefinger 100 withlatch 108 locks thefinger 100 in a position of flexion. - In the embodiment shown in
FIG. 7 , thelatch 108 may be disengaged manually from thefinger 100. For instance, thelatch 108 may be disengaged by pressing anunlock mechanism 136 that is coupled to thelatch 108. Theunlock mechanism 136 may push against thelatch 108, causing thelatch 108 to rotate away from thefinger 100, such that thelatch 108 is no longer positioned underneath the notch sides 110 of thefinger 100. In one embodiment, the unlock mechanism may be a protruding portion of the latch itself. In another embodiment, theunlock mechanism 136 may comprise a bias spring (not shown) that disengages thelatch 108 from thefinger 100. In one embodiment, the bias spring may be balanced against the torsion spring on the latch. As theunlock mechanism 136 is not under high stress, it can be miniaturized. - Once the
latch 108 is disengaged from thefinger 100, thespring 116 actuates thefinger 100 to a position that allows it to be actuated by thepower source 150. In a hand where the default position of thefinger 100 is one of extension (in other words, a “voluntary-close” hand), thespring 116 returns thefinger 100 to a default extended position. In a hand where the default position of thefinger 100 is one of flexion (in other words, a “voluntary-open” hand), thefinger 100 is released from the locked position byspring 116 but remains in a semi-flexed position. Thespring 116 biases thefinger 100 towards extension so as to maintain the position of theactuator linkage 104 at the bottom of theactuator slot 102. - In an embodiment, the
finger 100 may be configured so that it can remain in a locked position while at least one other finger on the same hand is free to move. This feature may be important to the user, for instance, if thefinger 100 and the at least one other finger are actuated or otherwise moved using the a common linkage. In this embodiment, having one locked finger does not prevent the other one or more fingers from actuating freely. This feature may also be important for the user to move thefinger 100 out of the way during an activity that does not require use of thefinger 100, such as activities involving trigger grip, fine pinch, or 3-jaw-chuck. This feature may also be important for the user if the user desires to lock thefinger 100 to assist with a particular type of grasp. For example, the thumb may be locked to assist with the user grasping an object. Alternately, the thumb may be locked to move it out of the way for activities that do not require the thumb. - For instance, as shown in
FIG. 7 , anactuator slot 102 is provided in thefinger 100 and is configured to receive anactuator linkage 104. Theactuator linkage 104 may be coupled to acommon link 140 which in turn may be coupled to apower source 150. Thearrow 106 inFIG. 7 indicates the direction of the actuation force that thepower source 150 provides to theactuator linkage 104 through thecommon link 140. Thepower source 150 may be an externally powered motor, a Bowden cable attached to the user's body, or another powered mechanism. - One embodiment achieves movement of unlocked fingers through the use of a slot in the proximal finger linkage at the attachment point of the actuator linkage. Forces on the proximal finger linkage only occur when the actuator linkage is at the end of the slot, ensuring larger surface areas and thus acceptable material pressures. Locking one or more fingers does not interfere with movement of the other fingers in either VO or VC modes, since the actuator link is free to move throughout the range of motion of the slot. Similarly, locking the fingers does not interfere in any way with the ability of the user to obtain proprioceptive input during use of the device, since the actuator link still moves throughout the entire range of motion and is not impeded in any way. As shown in
FIG. 7 , anactuation slot 102 in the actuation path enables the digit to move through its range of motion to a flexed position without inhibiting the actuator. Manually flexing the finger to a lockable position allowslatch 108 to engage with thenotch 110 on theproximal finger linkage 100.Latch 108 is biased by aspring 112 to close so that once the digit reaches the locked position, latch 108 will automatically engage withnotch 110 and statically lock the digit in a flexed position. -
FIGS. 8a, 8b, and 8c shows three different representations of thefinger 100. Each representation shows thefinger 100 in a different configuration during a different stage of use. (It should be noted that inFIGS. 8a, 8b, and 8c ,spring 116 is represented as a spring attached to a wall, rather than as a torsion spring as shown inFIG. 7 , so that the force it provides on thefinger 100 can be more easily visually compared to the lockingforce 134.) -
FIG. 8a shows thefinger 100 actuated to the maximum extent of the possible range of the motion of flexion. This position is known as “full flexion.” In a preferred embodiment, full flexion occurs at a greater range of motion than can be actuated by thepower source 150. This prevents thepower source 150 from accidentally locking the digit. In an embodiment, thefinger 100 may be configured to reach full flexion just beyond the point necessary for it to engage with thelatch 108. In order for full flexion to occur at a greater range of motion than can be actuated by thepower source 150, thefinger 100 may be constructed so that it can flex beyond the functional range of movement. For instance, if 90 degree flexion is required to accomplish most activities of daily living, thefinger 100 may be constructed so that it can flex up to 110 degrees. In this way, thepower source 150 is limited to flexing thefinger 100 to 90 degrees and then may reach a hard stop. At this point, the user can still manually flex the finger to 110 degrees of flexion, at which point the finger locks. Note that theactuator linkage 104 is not bottomed out in theslot 102. In this embodiment, it indicates that in order to engage thelatch 108, thefinger 100 must be flexed beyond the capabilities of thepower source 150. For thepower source 150 to be moving thefinger 100 into flexion, theactuator linkage 104 must be bottomed out in theslot 102. However, since theactuator linkage 104 is not in the bottom of theslot 102,FIG. 8a is showing thefinger 100 being flexed manually beyond the capabilities of thepower source 150. -
FIG. 8b shows thefinger 100 locked in a position of flexion. Once thefinger 100 has been pushed into the position of full flexion, thelatch 108 flips into place, engaging with the notch sides 110 to prevent extension of thefinger 100. This position can be accomplished by the lockingforce 134, rather than by theactuator force 106. -
FIG. 8c shows thefinger 100 locked in a position of flexion, with theactuator linkage 104 free to move throughout its normal range of motion in theactuation slot 102 in theproximal digit linkage 100. Locking of thefinger 100 does not prevent the at least one other finger (including a thumb) from being actuated throughcommon link 140 andpower source 150. - In another embodiment, a four-bar linkage may be inserted into the fingers, in order to kinematically couple PIP flexion to MCP flexion. In this manner the fingers remain relatively flat during palm-flat, yet achieve the required PIP flexion angle for chuck-grasp. The four-bar linkage maximizes pinch force while still achieving a kinematically acceptable motion profile, within the constraints of an anthropomorphic hand envelope. Another embodiment of a locking finger is shown in
FIG. 9 . Thefinger 200 may have aproximal phalanx 201 and adistal phalanx 202. (A “phalanx” is the part of the finger between two joints, while “proximal” and “distal” are used to describe the relative positions of the phalanxes to the body, with the “proximal” phalanx closer to the body and the “distal” phalanx further from the body.) As shown inFIG. 9 , in one embodiment, an upper portion of thedistal phalanx 202 may be configured in a cam shape, so that aportion 232 of thedistal phalanx 202 extends from the surface of thedistal phalanx 202 and allows for the receipt of apin 230 that connects thedistal phalanx 202 to the lockinglinkage 226. In one embodiment, asupport member 270 may be provided that connects to theproximal phalanx 201 by MCP joint 214 and connects to the lockinglinkage 226 bypin 228. (MCP joint 214 may be a pin or other suitable fastening mechanism.)Pin 230, positioned as shown inFIG. 9 to the left of the PIP joint 220, may connect the other end of the lockinglinkage 226 to thedistal phalanx 202. It should be understood that while pins may used to connect different components of the finger, as shown in the various figures herein, other fastening mechanisms known in the art may be used instead. Aslot 210 andactuator linkage 204 may be provided, for thefinger 200 to be flexed and/or extended independently of other fingers. - In one embodiment, the user pushes on the
distal phalanx 202 to lock thefinger 200. Thefinger 200 may lock due to engagement between the lockinglinkage 226 and the stoppingelement 208. In one embodiment, the stoppingelement 208 may be located on theproximal phalanx 201. - The locking
force 234 applied to thedistal phalanx 202 causes thedistal phalanx 202 to rotate about PIP joint 220. As shown inFIG. 9 , thedistal phalanx 202 begins to rotate in a clockwise direction about joint 220, and continues to rotate until the lockinglinkage 226 pushes against the stoppingelement 208. In doing so, thedistal phalanx 202 is flexed beyond the full flexion provided by the actuator. Additionally, the lockinglinkage 226 passes through the singularity defined by thepin 228,pin 230, and PIP joint 220 being collinear. Once the lockinglinkage 226 passes through this singularity, thefinger 200 remains locked (as described in further detail below).FIGS. 10a, 10b, and 10c show side views of the stages of thefinger 200 as it is locked in a position of flexion. - A more detailed description of a “singularity” may be found in U.S. patent application Ser. No. 14/030,095 to J. Sensinger, titled Gripping device with Switchable Opening Modes. Briefly, a mechanical singularity is when the position or configuration of the mechanism and its subsequent behavior cannot be predicted. With respect to
finger 200, when thepin 228,pin 230, and PIP joint 220 are aligned, it is not possible to determine whetherpin 230 will rotate about PIP joint 220 in a clockwise direction (and so working to flex the finger 200) or in a counterclockwise direction (and so working to extend the finger 200). -
FIG. 11 shows a perspective view of thefinger 200 locked in a position of flexion, where the lockinglinkage 226 is prevented from further flexion by stoppingelement 208.FIG. 11 also showswall 252, which provides common support as shown for the components of thefinger 200. Another wall on the opposite side of the stoppingelement 208 and lockinglinkage 226 may be provided, but is omitted fromFIG. 11 so that the reader can better see the internal arrangement of thefinger 200. - In one embodiment, at least one passive spring provides a torque that keeps the finger in a locked position. In one embodiment, shown in
FIG. 11 ,spring 224 provides a torque in a counterclockwise direction. When thefinger 200 is locked, the torque fromspring 224 attempts to extend theproximal phalanx 201. However, as theproximal phalanx 201 rotates towards extension, the lockinglinkage 226 creates a clockwise rotation aboutpin 230, due to the fixed radius ofpin 230 from PIP joint 220. This clockwise rotation of thedistal phalanx 202 moves the lockinglinkage 226 towards extension, where it collides with the stoppingelement 208. In order for thefinger 200 to continue into extension, the lockinglinkage 226 would need to occupy the space of the stoppingelement 208. However, since the stoppingelement 208 is present, thespring 224 at the MCP joint 214 acts to continuously engage the lockinglinkage 226 and the stoppingelement 208. This continued engagement of the lockinglinkage 226 with the stoppingelement 208 keeps thefinger 200 locked in the position of flexion. -
FIGS. 12a, 12b, and 12c display three side views of thefinger 200 being unlocked. InFIG. 12a , aforce 260 may be applied to a top surface of theproximal phalanx 201. Theforce 260 may be applied by the user's other hand, or by an object in the user's environment. Theforce 260 causes thefinger 200 to flex. In one embodiment, theforce 260 causes theproximal phalanx 201 to rotate in a clockwise direction, which rotates the lockinglinkage 226 to the singularity.FIG. 12b shows the lockinglinkage 226 at the point of singularity, at which point thePIP spring 222 pulls thedistal phalanx 202 outward andMCP spring 224 pushes theproximal phalanx 201 towards extension. Thesprings finger 200 back into the unlocked position shown inFIG. 12 c. - In an embodiment of the finger, the locking portion may physically configured to avoid catching or otherwise interfering with other portions of the system. For example, as shown in
FIGS. 13a and 13b , the lockinglinkage 226 may be contoured so that its movement between extension and flexion of thefinger 200 does not interfere with theactuator linkage 204 or thesupport member 206. Equivalent support members are shown in the profile viewsFIGS. 14-16 . As shown inFIG. 13a , the lockinglinkage 226 is contoured to receivesupport member 206 when thefinger 200 is extended. As shown inFIG. 13b , the same contour of the locking linkage receives theactuator linkage 204 when thefinger 200 is extended. - In alternative embodiments, a four-bar mechanism is used in each finger, and a fifth bar in each finger is used to transmit torque from the body-powered mechanism, such as a Bowden cable, to the finger. These fifth bars may be rigidly linked across the fingers, and connected by some method to a VO/VC switch mechanism, allowing the hand to function either as a VO or a VC hand. Each of the actuator links is attached to the output of the VO/VC mechanism, such that the output of the VO/VC mechanism is a linkage. The actuator links are attached through a linear bushing to ensure that each of the fingers moves at the same rate. The VO/VC mechanism is in turn attached to the Bowden cable or external motor, which provides the input to the VO/VC mechanism.
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FIGS. 14 and 15 show embodiments of a locking finger in use with ahand 300, where thehand 300 is configured to operate in voluntary-open (VO) mode. InFIG. 14 , thehand 300 is shown coupled to anactuation lever 310.Finger 320 andfinger 330 each have aslot FIG. 14 , theactuation lever 310 is coupled to thefingers actuation lever 310 causes rotation of theactuation lever 310 about a central pivot, causingswitch 360 to rotate in a counter clockwise direction. In doing so, switch 360 acts onpin 362 and link 364 to transfer an upward force throughpin 366 to thecoupler linkage 368. Thecoupler linkage 368 is connected bypin 370 todriver linkages 340, which actuate thefingers driver linkage 340 is coupled tofinger 320 by apin 320 p and is coupled tofinger 330 by apin 330 p.Pin 320 p is positioned in theslot 320 s and pin 330 p is positioned in theslot 330 s. As thedriver linkage 340 moves in the upward direction, eachpin respective finger - However, a finger, for
example finger 330, may be locked, so that actuation of theactuation lever 310 does not cause the finger to extend. For example,FIG. 15 showsfinger 330 locked in a position of flexion even as theactuation lever 310 has been actuated by aforce 350, such as being pulled on by a Bowden cable. As thehand 300 is actuated, thedriver linkage 340 moves in an upward direction.Spring 320 sp pullsfinger 320 into a position of extension.Finger 330 has a similar spring around its joint, but because thefinger 330 is locked, instead of that spring acting onfinger 330 to cause extension, pin 330 s instead slides throughslot 330 p, and comes to rest at the top ofslot 330 p as shown inFIG. 15 . -
FIGS. 16 and 17 show an embodiment of a locking finger in use with ahand 300, where the hand is configured to operate in a voluntary-close (VC) mode. As shown inFIG. 16 , thefinger 330 is locked in a position of flexion, and thepin 330 p is at the top of theslot 330 s. Thefinger 320 is in a position of extension due to torque provided by a spring aboutmain pivot 345. InFIG. 17 , with thehand 300 in VC mode, aforce 350 is applied to flex thefinger 320. Thepin 320 p moves to the bottom ofslot 320 s to flex thefinger 320, while thepin 330 p slides through the bottom of theslot 330 s as thefinger 330 is already locked in a position of flexion
Claims (20)
1. A prosthetic device comprising:
a first prosthetic digit;
a first engagement portion; and
a first stopping portion;
wherein the first engagement portion is capable of engaging with the first stopping portion to lock the first prosthetic digit in a position of flexion in response to a force applied to the first prosthetic digit.
2. A prosthetic device according to claim 1 , further comprising:
a second prosthetic digit.
3. A prosthetic device according to claim 2 , further comprising:
a second engagement portion; and
a second stopping portion;
wherein the second engagement portion is capable of engaging with the second stopping portion to lock the second prosthetic digit in a position of flexion in response to a force applied to the second prosthetic digit.
4. A prosthetic device according to claim 3 , wherein
the first prosthetic digit is capable of locking in a position of flexion independently from the second prosthetic digit.
5. A prosthetic device according to claim 4 , further comprising:
a linkage coupled to the first prosthetic digit and the second prosthetic digit;
wherein the linkage is configured to extend the first prosthetic digit when the first prosthetic digit is not locked in a position of flexion; and
wherein the linkage is configured to extend the second prosthetic digit when the second prosthetic digit is not locked in a position of flexion.
6. A prosthetic device according to claim 5 , further comprising:
a third prosthetic digit and a fourth prosthetic digit;
wherein the first prosthetic digit, second prosthetic digit, third prosthetic digit, and fourth prosthetic digit comprise prosthetic fingers.
7. A prosthetic device according to claim 1 , wherein
the first engagement portion comprises at least one notch positioned on the first prosthetic digit; and
the first stopping portion comprises a latch.
8. A prosthetic device according to claim 7 , wherein
the first stopping portion is positioned adjacent to the first prosthetic digit.
9. A prosthetic device according to claim 4 , wherein
the first engagement portion comprises at least one notch positioned on the first prosthetic digit;
the first stopping portion comprises a latch positioned adjacent to the first prosthetic digit;
the second engagement portion comprises at least one notch positioned on the second prosthetic digit; and
the second stopping portion comprises a latch positioned adjacent to the second prosthetic digit.
10. A prosthetic device according to claim 9 , further comprising:
a linkage coupled to the first prosthetic digit and the second prosthetic digit;
wherein the linkage is configured to extend the first prosthetic digit when the first prosthetic digit is not locked in a position of flexion; and
wherein the linkage is configured to extend the second prosthetic digit when the second prosthetic digit is not locked in a position of flexion.
11. A prosthetic device according to claim 10 , further comprising:
a third prosthetic digit and a fourth prosthetic digit;
wherein the first prosthetic digit, second prosthetic digit, third prosthetic digit, and fourth prosthetic digit comprise prosthetic fingers.
12. A prosthetic device according to claim 1
wherein the first prosthetic digit comprises a first phalanx and a second phalanx; and
wherein the first engagement portion comprises a first linkage joining the first phalanx and the second phalanx.
13. A prosthetic device according to claim 12 ,
wherein the first stopping portion is positioned on the first phalanx of the first prosthetic digit.
14. A prosthetic device according to claim 4 , wherein
the first prosthetic digit comprises a first phalanx and a second phalanx;
the first engagement portion comprises a first linkage joining the first phalanx and the second phalanx;
the second prosthetic digit comprises a third phalanx and a fourth phalanx; and
the second engagement portion comprises second linkage joining the third phalanx and the fourth phalanx.
15. A prosthetic device according to claim 14 , wherein
wherein the first stopping portion is positioned on the first phalanx of the first prosthetic digit; and
wherein the second stopping portion is positioned on the third phalanx of the second prosthetic digit.
16. A prosthetic device according to claim 15 , further comprising:
a linkage coupled to the first prosthetic digit and the second prosthetic digit;
wherein the linkage is configured to extend the first prosthetic digit when the first prosthetic digit is not locked in a position of flexion; and
wherein the linkage is configured to extend the second prosthetic digit when the second prosthetic digit is not locked in a position of flexion.
17. A prosthetic device according to claim 16 , further comprising:
a third prosthetic digit and a fourth prosthetic digit;
wherein the first prosthetic digit, second prosthetic digit, third prosthetic digit, and fourth prosthetic digit comprise prosthetic fingers.
18. A prosthetic device according to claim 4 , wherein
the first engagement portion comprises at least one notch positioned on the first prosthetic digit;
the first stopping portion comprises a latch positioned adjacent to the first prosthetic digit;
the second prosthetic digit comprises a first phalanx and a second phalanx;
the second engagement portion comprises a first linkage joining the first phalanx and the second phalanx; and
the second stopping portion is positioned on the first phalanx of the second prosthetic digit.
19. A prosthetic device according to claim 18 , further comprising:
a linkage coupled to the first prosthetic digit and the second prosthetic digit;
wherein the linkage is configured to extend the first prosthetic digit when the first prosthetic digit is not locked in a position of flexion; and
wherein the linkage is configured to extend the second prosthetic digit when the second prosthetic digit is not locked in a position of flexion.
20. A prosthetic device according to claim 19 , further comprising:
a third prosthetic digit and a fourth prosthetic digit; and
wherein the first prosthetic digit, second prosthetic digit, third prosthetic digit, and fourth prosthetic digit comprise prosthetic fingers.
Priority Applications (2)
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US16/657,638 US11246721B2 (en) | 2015-06-19 | 2019-10-18 | Lockable finger system and related methods |
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US201562182253P | 2015-06-19 | 2015-06-19 | |
US15/185,873 US20160367383A1 (en) | 2015-06-19 | 2016-06-17 | Lockable Finger System and Related Methods |
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US16/657,638 Division US11246721B2 (en) | 2015-06-19 | 2019-10-18 | Lockable finger system and related methods |
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US20160367383A1 true US20160367383A1 (en) | 2016-12-22 |
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US16/657,638 Active US11246721B2 (en) | 2015-06-19 | 2019-10-18 | Lockable finger system and related methods |
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USD783448S1 (en) * | 2015-12-15 | 2017-04-11 | Kamal Siegel | Figurine articulated hand |
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Also Published As
Publication number | Publication date |
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US20200054464A1 (en) | 2020-02-20 |
US11246721B2 (en) | 2022-02-15 |
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