Changeable code lock

A variable code lock for use with a cylindrical key comprising:

• an external shell having a cylindrical inner surface and a wall at one end thereof having an orifice of smaller diameter than that of the inner surface, the inner surface having a plurality of longitudinally disposed grooves thereon and an annular recess longitudinally spaced from the orifice;
• a drum disposed coaxially and rotationally within the shell and having a plurality of longitudinally disposed slots thereon each circumferentially corresponding to one of the grooves;
• a centrally disposed longitudinally oriented guiding rod rotationally fixed to and coaxial with the drum;
• a plurality of tumblers disposed in at least some of said slots extending radially inwardly further than an edge of the orifice and extending radially outwardly no further than a radially outwardly disposed edge of the drum, the tumblers each carrying a plurality of undulations;
• a plurality of blocks disposed and substantially radially fixed within the grooves having corresponding undulations that radially extend to interengage with the undulations of each of the tumblers;
• wherein the insertion of the cylindrical key having the predetermined code longitudinally through the orifice disposes each of the blocks within the recess of the shell to enable the drum to rotate circumferentially without interference and wherein the annular recess is constructed and arranged to allow the blocks to displace circumferentially therein;
• a plurality of radially outwardly disposed indentations located upon the inner surface of the shell within the annular recess at positions upon a circumference of the inner surface between each of the grooves, the indentations each having a radially outwardly disposed depth sufficient to allow radial displacement of the blocks away from the tumblers, so that the undulations of the tumblers disengage from interengaging contact with the corresponding undulations of the blocks, the blocks in the indentations remaining longitudinally fixed in the annular recess and the tumblers being movable in corresponding slots toward the orifice;
• the orifice being constructed and arranged so that the key can be inserted therethrough and removed therefrom only when the blocks are positioned within predetermined grooves and when the blocks are positioned within predetermined indentations, respectively, and a changing of a fixed longitudinal positioning of the blocks relative to the tumblers being enabled by changing the predetermined code of the key only when the blocks are located in the indentations;
• and
• a cylindrical key having a shaft with a plurality of lugs positioned thereon, the lugs each being independently rotationally variable relative to the shaft for engaging predetermined of the tumblers and wherein the shaft includes a selectively movable lug for selectively enabling the key to be removed from the orifice when the blocks are located in the indentations, whereby the predetermined code can be changed only when the lug is moved to a predetermined radial position on the shaft.