Telescopic jibs

Claim 1

Locking structure for a telescopic jib constituted by at least a first outer section, a second section and a third inner section, an element connected to the first section and by a single motive member connected between the first and second sections and comprising at least one bolt disposed on the rear end of the third section and capable of integrating the second and third sections in telescoped positions and in extended positions, the bolt being adapted for selective insertion in at least three locking catches the first of which is unitary with the rear end of the second section, thus to integrate the second and third sections to move them together relatively to the first section, the second catch being unitary with the element connected to the first section near the front end of the first section to maintain the third section in extended position relatively to the first section after extension of the assembled second and third sections relatively to the first section whereby the second section may be free to move rearwardly relatively to the first and third sections, the third catch being unitary with the front end of the second section to integrate the second and third sections whereby the assembled second and third sections may be extended together relatively to the first section, all said rearward and extended movements being effected by the single motive member.