Patent ID: 6915759

Claim:
A printing apparatus for printing a pattern on a surface of a spark plug insulator, comprising: a marking roller for forming an ink film on an intaglio thereon; a transfer roller for transferring said ink film which is further transferred to said spark plug insulator in order to print said pattern; an ink supply nozzle for supplying an ink for said ink film; and a doctor blade for scratching from said marking roller ink which does not contribute to form said ink film, wherein a concave depth in said intaglio is greater than or equal to 15 μm and smaller than or equal to 20 μm, and wherein said doctor blade is disposed at an upper side of said marking roller; is movable along the tangential and normal directions of the surface of said marking roller so as to follow swelling motion of said marking roller; and is pressed against said marking roller along a direction normal to the longitudinal direction of said doctor blade.