Desk top type label printer

A desk top type label printer comprising:

• a casing having an opening at one side and having a laterally openable cover for said opening;
• a tape holder for holding a roll of label tape in the interior of said casing;
• a thermal printing head unit inside said casing and having a thermal printing head;
• a tape depressing mechanism opposed to said thermal printing head unit and having a platen roller which is movable into and out of pressure contact with said thermal printing head;
• a driving means for feeding label tape inserted between said thermal printing head and said platen roller out of said casing;
• an electric circuit for controlling said thermal printing head and said driving means;
• an input means for entering data to be printed in said thermal printing head unit through said electric circuit;
• and
• a supporting shaft for supporting said thermal printing head unit and having one end supported on the interior of said casing and the other end free and extending toward said opening;
• said tape depressing mechanism having a support frame pivotally supported by a fixed shaft which extends parallel with said thermal printing head unit supporting shaft and having one end fixed to the interior of said casing and the other end a free end, said platen roller being at a free end of said support frame, and said thermal printing head unit and said tape depressing mechanism respectively having engaging means for engaging said tape depressing mechanism with said thermal printing head unit, said thermal printing head and said platen roller having a space therebetween which is open toward said opening for inserting a label tape between said thermal printing head and said platen roller when said tape depressing mechanism is turned to separate said platen roller from said thermal printing head unit, and said tape depressing mechanism being engaged with and fixed to said thermal printing head unit supporting shaft by said engaging means when said platen roller is urged toward said thermal printing head to press a label type to said thermal printing head;
• said engaging means comprising a pair of engaging parts on said supporting shaft of said thermal printing head unit respectively positioned on both sides of said thermal printing head and a pair of engaging cutaway parts provided on the support frame of said tape depressing mechanism respectively opposed to said engaging parts, each of said engaging parts having a cross section of a partly cutaway circle which is made up by partly cutting off a true circle with the center on the axial line of said supporting shaft, and said engaging cutaway parts respectively having a straight passage which is open at an end opposed to a corresponding engaging part and a circular hole at the other end of said straight passage, the width of said straight passage being slightly larger than the wall thickness of said engaging parts and the diameter of said circular hole being substantially the same as the diameter of said engaging parts, and a knob on said supporting shaft outside said thermal printing head unit for simultaneously rotating each of said engaging parts in corresponding circular holes of said engaging cutaway parts.