(US4498456-A)      The mechanism has several sensor concentrators arranged side by side. A number of shape memory alloy coils are located at a position coincident with the focal line of the corresponding sensor concentrators. The coil is treated so as to shrink into a memorised shape when heated.    Each tension wire has one end connected to one end of the coil and the other end wound up on a wire drum which is mounted on a drive shaft. A transfer mechanism is connected to the shaft for transferring the rotation of the shaft to a rotatable main collector.    ADVANTAGE -   Can track sun even if it disappears behind cloud for period of time.    (6pp)    (EP113098-B)      A solar tracking mechanism for a solar collector of the type comprising a base (1) settled on a ground, a frame (2) secured to said base, anda rotatable main collector (3) attached to said frame to be rotatable to collect radiant energy from the sun, said solar tracking mechanism being characterised in that it further comprises: a plurality of stationary concentrators (5a,5b,5c...) fixed to said frame and arranged with different angles with respect to each other so that each of said stationary concentrators catches the sun's radiant energy on the focal line thereof for a certain period; shape memory alloy coils (6) each having one end connected to said frame and another end and each being located at a position coincident with the focal line of the corresponding one of the stationary concentrators, said shape memory alloy coil (6) being treated so as to shrink into a memorized tightly wound-up coil shape when heated to a predetermined temperature; tension wires (7a,7b,7c...) each having one end connected to said other end of said shape memory alloy coil; wire drums (11) provided with a common drive shaft (12) and each fixing the other end of the respective one of said tension wires for winding up or winding off said tension wire; and a transfer mechanism (13,14) operatively connected to said drive shaft for transferring the rotation of said drive shaft to said rotatable main collector.    (8pp)