Rotary drill with a kelly bar and hydraulic chuck

In a rotary drilling apparatus wherein a rotary table is adapted to be moved axially while rotating, said rotary table including a spindle having an axially directed passage through it as its center of rotation, a kelly bar extending through said passage, means carried by the rotary table for transmitting positive rotational force from the rotary table to the kelly bar, said kelly bar having shoulder means having radial shoulder surfaces, elongated plunger means carried by said rotary table for selectively engaging and disengaging said kelly bar shoulder surfaces and actuating means carried by said rotary table for causing said plunger means to engage with and disengage from said shoulder means, the improvement comprising a tubular housing, means for holding said housing against rotation and to permit axial movement of said housing with said table, a chuck body mounted on said spindle and extending axially within and for rotation with respect to said housing, said plunger means being mounted for radial movement in said chuck body, said plunger means having cam surfaces on opposite sides of them intermediate their ends;

• said actuating means comprising a tube mounted on said chuck body for axial movement with respect thereto, said tube having spaced fingers, straddling said plunger means, each with a wedge-shaped camming surface for engaging the said cam surfaces of said plungers and moving said plungers outwardly radially upon axial movement of said tube to disengage said plungers from said kelly bar shoulder means, hydraulic means for moving said tube axially selectively, and means for biasing said plungers toward and into engagement with said kelly bar shoulder means when said tube camming means are moved away from said plungers.