Tubular door lock with a bell

A tubular door lock comprising an inside knob having a locking structure and a pipe shaft formed with a pair of elongate slots defining respective arcuate portions of the pipe shaft, an outside knob with a hollow square shaft in which is located a flat plate having one end adapted to engage the locking structure of the inside knob for rotating the flat plate, at least two holes in the square shaft in each of which is located a ball for radial up and down movement therein, an assembling plate having two arcuate slots for receiving the respective arcuate portions of the pipe shaft and with a square hole centrally of the arcuate slots for receiving the square shaft so that both knobs are connected for rotation through the assembling plate, a latch connected with a linking plate, the linking plate having a shaft hole with a pair of circumferential recesses, the shaft hole receiving the square shaft therein with said balls in line with the recesses, the flat plate extending through the square shaft for rotation by the locking structure between an unlocked position in which opposite edges of the flat plate engage the balls and urge the balls outwardly into said recesses to drivingly connect the square shaft and the linking plate, and a locked position in which the flat plate is rotated to release the balls from said recesses thereby disconnecting the square shaft from the flat plate.