Lifting devices for flat screen printer

Claim 1

An automatic screen printing machine comprising a transporting mechanism for supporting thereon a material to be printed and transporting it continuously or intermittently to a printing operation zone, a flat screen disposed in the printing operation zone above a running passage for the material to be printed, a squeegee member disposed above said screen to squeeze out a printing paste or ink onto the material to be printed through said screen, and a lifting device disposed in said operating zone for causing the material to be printed to come into contact with the screen during a printing step and of separating the material from the screen during a non-printing period by moving vertically at least one of said transporting mechanism and said squeegee member and screen relative to each other by means of a lifting member; said lifting device comprising a lifting cam mechanism and a gear mechanism for driving intermittently said lifting cam mechanism and restraining intermittently said lifting cam mechanism, said gear mechanism comprising a first partially toothed wheel including a toothed large diameter circumferential portion and a non-toothed small diameter circumferential portion, said partially toothed wheel being continuously driven and rotated by driving means connected therewith and a second partially toothed wheel including at least one toothed circumferential portion and at least one projected portion having a concave face capable of engaging the non-toothed smooth circumferential portion of the first partially toothed wheel, said first and second partially toothed wheels disposed adjacent to and in operable contact with each other such that the first and second partially toothed wheels are intermittently engaged with each other and are intermittently restrained by each other whereby engagement of the teeth of said first partially toothed wheel with the teeth of said second partially toothed wheel, drives and causes the second partially toothed wheel to rotate, and engagement of the projected portion of said second partially toothed wheel with the non-toothed smooth circumferential portion of said first partially toothed wheel, restrains the rotation of the second partially toothed wheel; said lifting cam mechanism including a cam and said second partially toothed wheel wherein said cam is fixed to said second partially toothed wheel to rotate together and said cam mechanism is operably connected to said lifting member whereby the rotation of said second partially toothed wheel and said cam causes the lifting member to be lifted or lowered and to be held at an elevated position or a lowered position by restraint of the rotation of said second partially toothed wheel.