Screen printer with ink level sensing and control

Claim 1

An automated printing ink supply device for an automatic screen printing machine of the type including an endless belt adapted to be intermittently driven around a pair of drums for feeding material to be printed with the material adhered to the outer surface of said endless belt along a forwarding moving run thereof, at least one screen frame having a screen positioned above said endless belt, said screen frame being movable between an upwardly shifted position in which said screen is clear of said belt and a downwardly shifted position in which said screen is in conTact with the material on the belt during the time the belt is stopped between intermittent movements, and a pair of juxtaposed squeegees reciprocally movable between first and second positions substantially across the width of the belt and slidable over the screen to deposit a printing ink contained on said screen between said squeegees, onto the material to be printed through said screen as said pair of squeegees is moved from either of said first and second positions to the other during the time the belt is stopped, said automated printing ink supply device comprising an ink storage container having an outflow opening and adapted to contain therein a substantial amount of printing ink, container mounting means positioned at one side of the machine on which said container is mounted at a position above the screen frame and squeegees and between the position of the squeegee remote from said mounting means when said squeegees are in the first position and said screen frame at said one side of said machine, a valve connected with said outflow opening of said container for regulating the flow of the printing ink from said container onto said screen, squeegee position and frame movement responsive means actuated in response to the presence of one of said squeegees adjacent to said mounting means upon return of said pair of said squeegees to said first position and further to the raising of said frame, means for detecting the level of the surface of said printing ink on said screen and producing a response when said level falls below a predetermined level, and valve operating means connected to said valve for opening and closing it and to which said squeegee position and frame movement responsive means and said level detecting means are coupled and operable to open said valve only when said responsive means is actuated and said level detecting means produces a response whereby said valve is opened only when the level of the surface of the printing ink on the screen falls below a predetermined level when the squeegees are at the said first position.