A discharge passage (42) of a work support includes: an annular space (2a) created between an insertion hole (2), provided through a leading end portion of a housing (1), and a support rod (3); and a discharge port (42a) provided at the leading end portion of the housing (1). The work support is designed so that an amount of gas pushed out of an outlet chamber (32) by an output member (24) when the output member (24) moves from its base-end-side limit position to its leading-end-side limit position is larger than a capacity of an accommodation chamber (45) created on a base end side relative to the support rod (3) due to movement of the support rod (3) from its base-end-side limit position to a leading-end-side position.

A hydraulic cylinder includes a rod insertion hole formed in a piston member, an auxiliary rod provided to a head side end wall member and capable of being inserted into the rod insertion hole, a rod fitting hole formed to pass through the head side end wall member and the auxiliary rod, a movable rod installed in the rod fitting hole and whose end portion toward a head side end wall projects to the exterior, a movement restriction mechanism that prohibits shifting of the movable rod in an unclamping state and permits shifting of the movable rod in a clamping state.

A work support includes a mounting plate and a mechanical lock coupled to the mounting plate. The mechanical lock includes a base coupled to the mounting plate and a support pin. The support pin is movably coupled to the base. As such, the support pin can move relative to the base. The work support further includes a locking collar at least partly disposed inside the base. The locking collar surrounds the support pin and includes a first collar portion disposed around the support pin. The first collar portion has an outer tapered surface facing away from the support pin. The locking collar further includes a second collar portion disposed around the support pin. The second collar portion has an inner tapered surface facing toward the support pin and can move relative to the first collar between an unlocked position and a locked position.