Image Number 3 for United States Patent #5351845.
A generally cylindrical relative rotatable lock structure comprises three relatively rotatable coaxial members. The first and second members have generally opposed surfaces carrying connecting means which interengage to prevent relative axial movement between those members except in predetermined relatively rotatable positions. The third member is supported by one of the first or second members to prevent axial movement relative to the supporting member, but to permit rotatable movement. Friction between the third and non-supporting member causes the third member to rotate with the non-supporting member. The third member has connecting means cooperable with the connecting means on the member which does not support the third member to prevent relative axial movement between the third and non-supporting members except in predetermined relative position. Opposing stop members are provided on the third member and the supporting member limiting their relative rotation in one direction to less than one revolution before the stop faces abut after which the third member is driven by the stop member to rotate with the supporting member. However, at least one of the stop members has a ramp on the face opposed to the stop face of such a pitch that the other stop member, upon encountering the ramp, is able to ride up the ramp and over the stop member during relative rotation in the direction opposite to that causing contact between the stop faces. The principal use of the invention is as a closure for child-resistant packaging.