Working machine and method for working the ground

A working machine, in particular construction machine, having a mast, along which, by means of a positioning means, a rotary head is vertically movable, by which a telescopic Kelly rod having at least two Kelly bars is guided in a displaceable manner, wherein an outer Kelly bar designed for being supported on the rotary head and an inner Kelly bar are provided which comprises a rope suspension for a rope, by which the inner Kelly bar is vertically movable by means of a main rope winch, wherein, for the purpose of torque transmission, Kelly bars are provided on their external and/or internal sides with axially running drive keys as well as locking recesses on the drive keys which can be moved into the locking recesses for axially locking the Kelly bars or moved out of the locking recesses for unlocking,

• wherein a control is provided which is designed for the locking and/or unlocking of the Kelly bars,
• wherein
• for the automatic locking of the Kelly bar the control is configured such that a first torque can be applied to the Kelly bar, wherein a latch element is applied with slight pressure to a drive key of the opposite Kelly bar, and
• the two Kelly bars are moved axially relative to each other until the latch element rotates in the circumferential direction into a locking recess,
• by means of a first detection means a rotation angle of at least one Kelly bar can be detected during inward rotation or that by means of a second detection means a force, torque or pressure change in a drive system, by which at least the positioning means, the rotary head or the main rope winch are driven, can be detected during inward rotation,
• and
• the control is designed to determine the locking of the Kelly bars depending on the detected rotation angle or the detected force, torque or pressure change in the drive system.