Lockable finger system and related methods
A prosthetic device having a proximal interphalangeal joint (PIP) and a metacarpophalangeal joint (MCP), comprising a first prosthetic digit comprising one or more first phalanges and a four-bar linkage to operatively couple the PIP joint to the MCP joint, a first engagement portion positioned on one of the first phalanges, the first engagement portion comprising a locking linkage extending along the phalange, the locking linkage being part of the four-bar linkage, and a first stopping portion comprising a stopping element configured to be positioned above the locking linkage, wherein the locking linkage is capable of engaging with the stopping element by passing the one of the first phalanges in which the locking linkage is positioned through a mechanical singularity to lock the first prosthetic digit such that each of the one or more phalanges is in a position of flexion in response to a force applied to the first prosthetic digit.
1. A prosthetic device comprising:
a first prosthetic digit and a second prosthetic digit, wherein each prosthetic digit comprises:
i. a first phalange comprising a proximal end and a distal end;
ii. a proximal interphalangeal (PIP) joint;
iii. a second phalange coupled to the distal end of the first phalange at the PIP joint, a portion of the second phalange that is coupled to the first phalange comprising a cam;
iv. a metacarpophalangeal (MCP) joint;
v. a four-bar linkage configured to operatively couple the PIP joint to the MCP joint, the four-bar linkage comprising a locking linkage extending along the first phalange, wherein the proximal end of the first phalange receives a first pin that connects the proximal end to the locking linkage, and the distal end of the first phalange receives a second pin that connects the cam of the second phalange to the locking linkage; and
a stopping portion comprising a stopping element configured to be positioned above the locking linkage, wherein, in response to a force applied to move the second phalange into a position of flexion, the cam of the second phalange rotates in a first direction about the PIP joint until the locking linkage encounters the stopping element such that the second phalange is in a position of flexion and the locking linkage passes through a mechanical singularity, defined by the first pin, the second pin, and the PIP joint being collinear, to lock the prosthetic digit into the position of flexion.
2. The prosthetic device according to claim 1 ,
wherein the stopping portion of each prosthetic digit is positioned on the first phalange of the prosthetic digit.
3. The prosthetic device according to claim 1 , further comprising:
an actuator linkage coupled to each of the first prosthetic digits;
wherein the actuator 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 actuator linkage is configured to extend the second prosthetic digit when the second prosthetic digit is not locked in a position of flexion.
4. The prosthetic device according to claim 3 , 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.
5. The prosthetic device according to claim 1 , wherein the PIP joint comprises a spring configured to bias the second phalange into an open position when the second pin and the cam are on a first side of the mechanical singularity and bias the second phalange into the position of flexion when the second pin and the cam are on a second side of the mechanical singularity.
6. The prosthetic device according to claim 1 , wherein the locking linkage of each prosthetic digit moves independently of the other locking linkages such that each prosthetic digit can be in a locked position or an unlocked position, independently of the other prosthetic digits.