Cylinder lock

1. A cylinder lock comprising:

an outer cylinder longitudinally having a plurality of upper tumbler bores;

an inner cylinder which is fit into the outer cylinder so as to be freely rotatable, the inner cylinder having a plurality of lower tumbler bores connecting with a keyway and corresponding to the plural upper tumbler bores in the outer cylinder;

upper tumblers inserted into the upper tumbler bores of the outer cylinder, respectively;

springs arranged in the upper tumbler bores, respectively, so as to urge the upper tumblers toward the inner cylinder;

lower tumblers inserted into the lower tumbler bores of the inner cylinder, respectively; and

auxiliary tumblers interposed between the upper tumblers and the lower tumblers of spontaneously selected pairs of upper tumblers and lower tumblers, so that the auxiliary tumblers can be moved aside from between the upper tumblers and the lower tumblers, thereby enabling a change of keys for locking and unlocking the cylinder lock,

wherein a plurality of elongated accommodation holes are formed longitudinally on an outer peripheral surface of the inner cylinder, and a groove is formed on the outer peripheral surface of the inner cylinder so as to connect the plural accommodation holes,

wherein partition walls are provided for separating adjacent ones of the upper tumbler bores from each other,

wherein the elongated accommodation holes are each formed in such region that when the inner cylinder is turned at a predetermined angle to cause the elongated accommodation holes to be positioned facing the upper tumbler bores, a longitudinal length of each accommodation hole extends from a corresponding upper tumbler bore facing the accommodation hole to a partition wall adjoining to the corresponding upper tumbler bore,

wherein a set/reset member is arranged to slide freely in the groove, the set/reset member being provided with crests and roots formed alternately continuously to each other in a longitudinal direction, a tapered part being provided behind each root and in front of each crest, and a stopping part being provided in front of each root and behind each crest, such that

in a reset state in which all of the auxiliary tumblers are positioned between the upper tumblers and the lower tumblers, upon insertion of an adaptable key into the keyway of the inner cylinder so as to move any ones of the auxiliary tumblers into the upper tumbler bores and the remaining auxiliary tumblers into the lower tumbler bores, the inner cylinder is configured to be turned at a predetermined angle so as to bring the auxiliary tumblers positioned in the upper tumbler bores into contact with crests of the set/reset member, and the set/reset member is configured to be pushed by a first stroke longitudinally of the groove, through an outside operation, so as to move the auxiliary tumblers contacting with the crests to a position of facing the roots whereby the auxiliary tumblers are accommodated into accommodation holes on the inner cylinder by an urging force of the springs for the upper tumblers, such that upon releasing the set/reset member, the stopping parts of the set/reset member move the auxiliary tumblers accommodated in the accommodation holes longitudinally of the elongated accommodation holes by an urging force of a spring for the set/reset member to a position such that each of the auxiliary tumblers in the accommodation holes faces a foregoing partition wall of a corresponding upper tumbler bore and is held in a set state, and

in the set state, upon insertion of an adaptable key into the keyway of the inner cylinder, the inner cylinder is configured to be turned at a predetermined angle such that the accommodation holes face the upper tumbler bores, and the set/reset member is configured to be pushed, through an outside operation, by a second stroke longer than the first stroke such that the auxiliary tumblers held in the accommodation holes and positioned at roots of the elongated accommodation holes are pushed toward a side of the upper tumbler bores through function of the tapered parts in continuation to the roots, and such that crests in continuation to the tapered parts hold the auxiliary tumblers in the upper tumbler bores, the inner cylinder being further configured to be turned to a position at which the upper tumbler bores and the lower tumbler bores face each other, such that upon releasing the set/reset member, the auxiliary tumblers are returned to the reset state between the upper tumblers and the lower tumblers.

2. A cylinder lock as set forth in claim 1 , further comprising:

an insertion bore for a set/reset pin, the insertion bore being provided at a front of the inner cylinder;

a first jig which holds a key which is to be inserted into the keyway for a setting operation, so that when the key is inserted into the keyway, a first pin having a first length is inserted into the set/reset pin insertion bore, and when the first pin having the first length is pushed in completely by the first stroke, the set/reset member is operated, through the outside operation, so as to change a position of the set/reset member from a position at which the crests face the upper tumbler bores to a position at which the roots face the upper tumbler bores; and

a second jig which holds a key which is to be inserted into the keyway for a resetting operation, so that when the key is inserted into the keyway, a second pin having a second length longer than the first length is inserted into the set/reset pin insertion bore, and when the second pin having the second length is pushed in completely by the second stroke, the auxiliary tumblers positioned at roots of the elongated accommodation holes of the inner cylinder are pushed to the side of the upper tumbler bores by function of the tapered parts in continuation to the roots.