Thermal printer unit and thermal printer

A thermal printer comprising:

• a body comprising a paper roll containing part for holding a paper roll
• a thermal head assembly mounted on said body, and comprising:
• a frame having platen roller receiving parts receiving both ends of a platen roller, respectively;
• a thermal head mounted on said frame;
• and a spring member mounted on said frame and applying a head pressure to said thermal head;
• and
• a cover rotatably supported by said body, supporting said platen roller, and covering an opening of said paper roll containing part,
• wherein, in a condition in which said opening of said paper roll containing part is covered by said cover, said platen roller is pressed onto said thermal head, and said platen roller is fitted into said platen roller receiving parts so that said cover is maintained in the condition in which said opening is covered by said cover, and
• wherein each platen roller receiving part comprises:
• a vertical groove part having an opening at the top thereof;
• a horizontal groove part extending from the bottom of said vertical groove part in a direction such as to be away from said thermal head;
• and
• a projection part formed relatively by said vertical groove part and horizontal groove part, located above said horizontal groove part, and projecting from a depth part of said horizontal groove part toward said thermal head, and
• wherein, in the condition in which said cover covers said opening of said paper roll containing part, both ends of said platen roller are inserted into the horizontal groove parts of said platen roller receiving parts, respectively, and, also, are pressed by said spring member through said thermal head into the depth parts thereof, respectively;
• and
• wherein said thermal head is obliquely provided so that said thermal head is pressed onto said platen roller by said spring member, thereby preventing said platen roller from being moved upward unless an external force of predetermined magnitude is applied to said platen roller to move said thermal head against a resilient force of said spring member.

A thermal printer unit comprising

• a thermal head assembly;
• and
• a platen roller,
• wherein:
• said thermal head assembly comprises:
• a frame having a platen roller receiving part receiving said platen roller;
• a thermal head mounted on said frame;
• and
• a spring member mounted on said frame and applying a head pressure to said thermal head,
• wherein:
• said thermal head assembly further comprises photosensors provided on the rear side of said platen roller receiving part so as to face said platen roller;
• and
• said photosensors are used for detecting, through combination of outputs thereof, any of a condition in which printing operation can be properly performed by said printer unit, a condition in which paper for the printing is nearly run out, a condition in which the paper for the printing is run out, and a condition in which said platen roller is removed from said platen roller receiving part.

A thermal printer comprising:

• a body comprising a paper roll containing part for holding a paper roll;
• a thermal head assembly mounted on said body, and comprising:
• a frame having a platen roller receiving part receiving a platen roller;
• a thermal head mounted on said frame;
• and a spring member mounted on said frame and applying a head pressure to said thermal head;
• and
• a cover rotatably supported by said body, supporting said platen roller, and covering an opening of said paper roll containing part,
• wherein, in a condition in which said opening of said paper roll containing part is covered by said cover, said platen roller is pressed onto said thermal head, and said platen roller is fitted into said platen roller receiving part so that said cover is maintained in the condition in which said opening is covered by said cover, and
• wherein:
• said thermal head assembly further comprises photosensors provided on the rear side of said platen roller receiving part so as to face said platen roller;
• and
• said photosensors are used for detecting, through combination of outputs thereof, any of a condition in which printing operation of said printer can be properly performed, a condition in which paper for the printing is nearly run out, a condition in which the paper for the printing is run out, and a condition in which said platen roller is removed from said platen roller receiving part.

A thermal head assembly mounted on a body of a thermal printer including a platen roller and a cover rotatably supported by the body and rotatable into a closed condition, the thermal head assembly comprising:

• a thermal head;
• a frame having the thermal head provided obliquely thereon, and having platen roller receiving parts to receive both ends of the platen roller, the platen roller being fitted into the platen roller receiving parts to maintain a position of the cover when the cover is covering the opening, each platen roller receiving part having
• a vertical groove part having an opening at the top,
• a horizontal groove part, having a depth part, and extending from the bottom of the vertical groove part in a direction away from the thermal head, and into which both ends of the platen roller are pressed when the cover covers the opening, and
• a projection part, formed relatively by the vertical groove part and the horizontal groove part, located above the horizontal groove part, and projecting from the depth part toward the thermal head;
• and
• a spring member, mounted on the frame, applying a head pressure to the thermal head to press the thermal head onto the platen roller and to press the ends of the platen roller, respectively, into the depth parts of the horizontal groove parts when the cover is covering the opening, to prevent the platen roller from moving upward unless an external force of predetermined magnitude is applied to the platen roller to move the thermal head against the head pressure applied by the spring member.