Vacuum printer

Claim 1

In a vacuum printer for the graphic arts, having a bed, a blanket frame upon said bed including a flexible impervious blanket having a peripheral sealing bead, a glass frame including a glass juxtaposed with the blanket frame and with said glass in snug flexing and sealing registry with said bead, defining a contact printing chamber, means movably mounting the glass frame for opening and closing movements relative to said blanket frame, a vacuum source having a first vacuum conduit communicating with said printing chamber for evacuating said printing chamber; the improvement comprising: a support mounted upon and underlying said blanket frame; a non-metallic base plate yieldably positioned within and peripherally spaced from said blanket frame, supportably underlying said blanket; a plurality of uniformly spaced spring means interposed between said support and said base plate, uniformly supporting said base plate; a continuous centrally apertured skirt of flexible imperforate material along its outer periphery sealed upon said blanket frame, and along its inner periphery sealed against peripheral portions of said base plate; said skirt and base plate defining with said blanket a vacuum chamber; a second vacuum conduit interconnecting said first vacuum conduit and said vacuum chamber initially retaining said blanket upon said base plate; and a control means connected to said second conduit for simultaneously evacuating said vacuum chamber and regulating its vacuum level with respect to the vacuum level in said printing chamber, and after a preset period cutting off vacuum from said vacuum chamber; said base plate and blanket thereon adapted for uniform upward movement relative to said glass under the combined action of atmospheric air pressure and said spring means, said blanket then disengaging from the base plate and supportably engaging the glass.