target activation pressures can be determined and the locking mechanism designed to be activated by the predicted pressure at a predetermined depth or location designing the system around the casing expansion that will occur at a desired depth or location provides flexibility and reliability as casing 16 expands wrap band springs 30 are tensioned between casing 16 and outer ratchet band 24 causing rotation of outer ratchet band 24 about casing 16 rotation of outer ratchet band 24 in turn causes rotation of interlocking inner ratchet band 26 see fig6 a and detail ad when this increased pressure is released one or more compression torsion springs 28 urge outer ratchet band 24 toward the original pre pressurization position see fig6 b and detail ac wrap bands 30 can include any number of partial or full windings about casing 16 to achieve a desired circumferential tension and corresponding movement of a free end of wrap band 30 in response to a given pressurization and circumferential expansion of casing 16 the latch or locking portion of ratchet mechanism 14 comprises numerous components that work together as illustrated in fig3 a and 4b a ratchet spring lock 31 engages inner ratchet 26 to ensure unidirectional rotation and prevent inner ratchet 26 from rotating backwards with the outer ratchet band 24 when the pressure is released ratchet spring lock 31 is protected from debris by ratchet spring lock cover 33 thus selective cyclical pressurization of casing 16 causes outer ratchet band 24 to rotate back and forth which in cooperation with spring lock 31 produces a ratcheting reaction between outer ratchet band 24 and inner ratchet band 26 with.