Inside corner concrete form unit

Abstract

A form unit to cast the inside surfaces of a corner of a concrete structure has a pair of form panels disposed generally perpendicular to each other and an elongated corner member disposed between the adjoining edges of such panels with an actuator having relatively movable parts including a first part connected by parallelogram linkage to each of the form panels and a second part connected to the corner member so that when the actuator parts are moved together the form panels are butted against the outer edges of the corner member and when the actuator parts are moved apart the form panels are separated from the corner member. Holding means retains the corner member against displacement toward the panels while the form panels are being stripped from the hardened concrete and latch means holds the form panels against relative movement while the corner member is being stripped. The latch means and holding means are operated conjointly and in conjunction with operation of the actuator, preferably all operations being performed hydraulically. For casting all inside surfaces of a complete tubular structure four of the corner form units are assembled into a box configuration with the outwardly facing walls defining the inside surfaces of the structure to be cast.