Single dot tactile reading module including a tactile dot, driven by a rotation
of a cam around its axis, either directly or through a pair of levers. A shape
memory alloy wire is attached on one hand to a rod which ends can slide in slots
cut in internal faces of the cam, on the other hand to a rod held in a fixed position
at the bottom of the tactile module. The wire contraction, produce by Joule heating,
rotates the cam which in turn moves the dot up or down depending on the direction
of the rotation. The wire cooling, accelerated by a heat sink allows the return
of the wire to its initial length with help of a spring which pushes the rod from
one end to the opposite end of the slots the cam being prevented from rotating
by a locking spring having two stable positions, one corresponding to the up position
of the dot, the other to its down position. At the end of the wire cooling phase,
the rod and the wire occupy positions symmetrical from their positions at the beginning
of the wire heating phase with respect to containing the dot axis and the cam axis.
Each subsequent contraction-recovery cycle of the wire reverses the tactile dot position.
