System for retaining stencil printing master on printing drum by clamp strip hinged along drum generator

A system for retaining a leading edge of a stencil master to a cylindrical printing drum of a stencil printing device, said printing drum being mounted to be rotatable around its central axis, comprising:

• a magnet strip carried by said printing drum to extend substantially along an outer surface portion thereof and parallel with said central axis;
• a clamp strip made of a material which is magnetically attracted by said magnet strip, one edge of said clamp strip being hinged to said printing drum along a pivot line extending near one side of said magnet strip substantially parallel with said central axis so that said clamp strip can be pivoted for substantially 180.degree. between a first pivot position where it lies against and along said magnet strip so as to be held thereon by an attracting magnetic force and a second pivot position where it lies against an outer surface portion of said printing drum opposite to said magnet strip with respect to said pivot line so as to be substantially free from the attracting magnetic force of said magnet strip;
• a permanent magnet mounted at a circumferentially spaced surface portion of said printing drum for stably holding said clamp strip at said second pivot position;
• and
• a means for selectively driving said clamp strip between said first and second pivot positions by overcoming the holding actions applied to said clamp strip by said magnet strip and said magnet for holding said clamp strip at said second pivot position said driving means comprising:
• a first gear wheel coupled to said clamp strip with its central axis in alignment with said pivot line of said clamp strip so as to be rotatable with said clamp strip around said pivot line;
• a second gear wheel which can mesh with said first gear wheel to drive said first gear wheel and
• a means which supports said second gear wheel to be rotatable around its central axis and to be selectively movable between a first shift position where said second gear wheel meshes with said first gear wheel when said printing drum is in its certain predetermined rotational position and a second shift position where said second gear wheel is removed from said first gear wheel so as not to interfere with said first gear wheel when said printing drum is rotated around said central axis.