PURPOSE: To raise the safeness of an oil-pressure hammer system by a method in which the movement of a bar provided on the rod end of a cylinder is detected, the dropping height of the hammer is calculated by the detection signal, and the height of the hammer is displayed by signals from the arithmetic unit.
CONSTITUTION: When oil is sent into the lower chamber 3a of a rod cylinder 3 and a piston 3c is raised, rods 1 and 2 are raised to pull up a ram 4. As the rods 1 and 2 go up, a bar 10 is also raised and when a photoelectric switch 14 passes through the small holes 13, 13' and 13"... of the bar 10 in order, on-off operations of the switch 14 are repeated by the passage of light. The number of the repeating times is counted by a counter 16, the pulling-up distance of the ram 4 is calculated in the arithmetic unit 17 to calculate the dropping height of the ram 4, and the calculated value is displayed digitally on a displayer 18.
YOSHIDA KAZUYUKI
MIZUNO TOSHIYUKI
