Locking device

A lock comprising:

• a housing including
• a housing body that has an inner surrounding surface defining an inner space, and a limiting groove formed in said inner surrounding surface;
• a cylindrical core extending along a core axis into said housing, rotatable relative to said housing about the core axis, and having
• an insertion end that is retained in said inner space of said housing body,
• a helical keyway that is formed in an outer surrounding surface of said cylindrical core, and that extends through said insertion end to form an opening of said insertion end, and
• a retaining groove that is formed in said outer surrounding surface of said cylindrical core;
• and
• a tumbler unit including
• a limiting member that is mounted to said cylindrical core, that is movable relative to said cylindrical core along a limiting axis of the cylindrical core, and that has a main body and a limiting projection, said main body extending into said retaining groove and having a driven section that extends into said helical keyway, said limiting projection projecting away from said cylindrical core, and being aligned with said limiting groove in the direction of the limiting axis when said cylindrical core is at a locked position, said limiting projection engaging fittingly said limiting groove to prevent the relative rotation between said cylindrical core and said housing when said limiting member is at an engaged position, said limiting projection being disengaged from said limiting groove to permit the relative rotation between said cylindrical core and said housing when said limiting member is at a disengaged position, and
• a resilient member that abuts against said limiting member for biasing resiliently said limiting member to the engaged position when said cylindrical core is at the locked position, so as to prevent the relative rotation between said cylindrical core and said housing;
• wherein a blade member is capable of being inserted into said helical keyway via said opening of said insertion end of said cylindrical core to access said driven section of said limiting member when said cylindrical core is at the locked position, so as to drive movement of said limiting member to the disengaged position to permit the relative rotation between said cylindrical core and said housing.

A key adapted for use with a lock, the lock including a housing, a cylindrical core that extends rotatably into the housing and that has a helical keyway, and a limiting member that is mounted movably between the housing and the cylindrical core, the limiting member having a driven section that extends into the helical keyway and a guide block that projects from the driven section, and being movable between an engaged position where the relative rotation between the housing and the cylindrical core is prevented, and a disengaged position where the relative rotation between the housing and the cylindrical core is permitted, said key comprising:

• a grip section for being held;
• and
• a blade section connected to said grip section and including a helical blade, said helical blade being adapted to be inserted into the helical keyway to access the driven section of the limiting member, so as to drive movement of the limiting member to the disengaged position to permit the relative rotation between the housing and the cylindrical core;
• wherein, said helical blade of said key has a helically-extending guide surface, and a continuous guide groove that is formed in said guide surface, and that substantially extends along said guide surface, at least a portion of said guide groove being configured not to extend in the helically-extending direction of said guide surface, the guide block engaging slidably said guide groove when said helical blade is inserted into the helical keyway, such that the limiting member is moved by a groove-defining surface that defines said guide groove during the insertion movement of said helical blade of said key.