Patent ID: 8663142

Claim:
A compact joint having two-axis construction that uses a combination of hydraulics and gears to convert linear hydraulic motion into radial motion and thereby provide variable extension assist and an infinite number of flexion stops for controlled flexion flow, said joint having: a distal member having a proximal end, and a cut-out area therethrough close to said proximal end; a main member joined in co-linear pivotal relation to said distal member; a hydraulic cylinder and piston configured and positioned to provide variable extension assist and an infinite number of flexion stops for controlled flexion flow during movement of said distal member relative to said main member, said hydraulic piston having a distal end; a drive gear associated with said main member and having a protrusion positioned in contact with said distal end of said piston, said drive gear also having a plurality of gear teeth; and a thickened transfer gear having a plurality of gear teeth forming a perimeter configuration for said transfer gear that is similar to that of said cut-out area in said distal member, said perimeter configuration being slightly smaller in dimension than said cut-out area, and said perimeter configuration also being partially press-fit into said cut-out area, with said gear teeth of said drive gear and said gear teeth of said transfer gear in contact with one another and providing a functional gear ratio that also promotes compact joint construction by reducing the amount of travel required by said piston to achieve maximum extension of said distal member relative to said main member, wherein when hydraulic pressure is increased within said hydraulic cylinder, linear motion of said piston toward said protrusion of said drive gear rotates said drive gear providing radial hydraulic force transfer and variable extension assist for movement of said distal member relative to said main member, and rotation of said drive gear causes rotation of said transfer gear and movement of said distal member relative to said main member toward a position of maximum extension, with adjustment of hydraulic pressure in said hydraulic cylinder also determining flexion response of said distal member relative to said main member, which is able to range from full lock to free action with varying levels of pressure return, providing an infinite number of flexion stops for controlled flexion flow in the movement of said distal member relative to said main member toward a position of maximum flexion.