A DISC TYPE CYLINDER LOCK

摘要

A disc type cylinder lock comprises an outer cylinder; an inner cylinder fitted in the outer cylinder; locking tumbler discs inserted in the inner cylinder; a positioning disc slightly movable within inner cylinder; a key insertable into key-holes of the locking tumbler discs and the positioning disc; and a side bar disposed between the outer cylinder and the peripheries of the locking tumbler discs and the positioning disc. The positioning disc has a protrudent piece which is able to enter and escape from a receiving hole formed in the inner cylinder. The key-hole of the positioning disc is longer in a radial direction than the key-holes of the locking tumbler discs. The positioning disc has a projection on the periphery of the key-hole. The key has a longitudinal guide groove and a recess at the terminal of the guide groove. When the key is initially after full insertion thereof, a through-groove is formed by aligned notches of the locking tumbler discs and the positioning disc. Upon the further rotation of the key, the side bar enters into the through-groove, thereby the projection of the positioning disc enters into said recess of the key, and the protrudent piece of the positioning disc escapes from the receiving hole of the inner cylinder. In this way, the inner cylinder can rotate to a predetermined extent with respect to the outer cylinder.