Prosthetic hand system

A prosthetic hand structure (100) comprises at least one mechanical finger (110a-e) comprising in turn a metacarpal support (111) and a proximal stiff link (112) connected to the metacarpal, support (111) by a proximal cylindrical joint (113). The proximal stiff link (112) is arranged to carry out a rotation of predetermined amplitude (φ) with respect to the metacarpal support (111) about an axis (113') of the proximal cylindrical joint (113). The mechanical finger (110a-e) also comprises a transmission member (116, 117) connected to the proximal stiff link (112). The transmission member (116, 117) is adapted to actuate the proximal stiff link (112) for causing the above described rotation of predetermined amplitude (φ). In particular, the transmission member (116, 117) comprises a worm screw (116) integral to the proximal stiff link (112) and is arranged for carrying out a rotation about a longitudinal axis (116') of the worm screw (116). The transmission member (116, 117) comprises also a flexible rack (117) having a first end portion (117a), pivotally connected to the metacarpal support (111), and a second end portion (117b) arranged to engage with the threaded profile of the worm screw (116) at an engagement zone (P) of the flexible rack (117). It is provided an actuator (118) mounted to the mechanical finger (110a-110e) and to actuate the worm screw (116), causing it to rotate about its rotation axis (116' ), in such a way that, when the actuator (118) moves the worm screw (116), there is a moving away/approaching movement of the engagement zone (P) away from/towards the first end (117a), with subsequent rotation of predetermined amplitude (φ), in a direction of rotation, or in the opposite direction, of the proximal stiff link (112) about its axis (113'), corresponding to the extension/flexion movement of the mechanical finger (110a-110e).