Patent GB-813112-A (GB)
Title: An improved method of and apparatus for use in screen printing
IPC: B41F15/12
Filed: 1954-04-20
Abstract: 813,112. Stencilling apparatus; sheet delivery apparatus. BALMER, W., and HERON, J. A. Dec. 30, 1955 [April 20, 1954], No. 11305/54. Classes 100(1) and 100(2) In a screen printing machine, means are provided whereby the air in the immediate vicinity of the screen is maintained charged with a vapour so that the drying of the ink on the screen during the printing operation is inhibited, thus allowing the use of inks which will dry on the printing stock more rapidly than the inks generally used in screen printing so that the prints may be stacked in a pile more quickly than is generally practicable. The machine comprises a main frame 10 and a feed-table 14 on which each sheet to be printed is positioned. A screen frame 18 is mounted for reciprocation within a chamber 24. Reciprocation is effected by means of a cam 19b fast on a driven shaft 19a and which causes reciprocation of a member 19c connected to a rod 19d. The rod 19d is pivoted at its lower end and connected to lugs 19e on the frame 18 at its upper end. The lugs 19e are provided with guide slots in which are fitted the ends of a transverse rod 23 carrying grippers 23a which can move up and down in the slots. When the frame is in the dotted position shown, the grippers 23a grip a sheet on the table 14 and, as the frame moves forwardly pull it between an impression roller 17 and the screen in the frame 18 upon which a squeegee 21, fed from an ink reservoir 20 is operative. During the rearward, movement of the frame 18 the roller 17 and squeegee 21 are rendered inoperative by means of rods 20b operated by cam 20a. The printed sheet is delivered on to a downwardly inclined conveyer 22 by the grippers 23a which move vertically so as to conform to the level of the conveyer 22. Apart from the inlet and outlet for the sheet to be printed, the chamber 24 completely encloses the stencilling frame and is provided with a spray nozzle 27 for discharging the vapour into the chamber 24 from a reservoir 26 either continuously or intermittently in relation to the reciprocation of the frame 18. Delivery apparatus: After being deposited on the conveyer 22 each sheet is delivered to one of a plurality of conveyers 38 forming part of a storage unit. This unit includes a box-like frame carrying guide pulleys 29 which ride on vertical guide rails 30. The frame is carried by four endless chains 31 each passing over sprocket wheels 32. The chains are driven step by step by reciprocation of a shaft 33 which imparts a rocking motion to a bracket 34 provided with a pawl 35 which engages a ratchet wheel 34b. The wheel 34b is fast on a shaft 34a which carries a sprocket wheel 32. Each chain 31 is connected by a pin to an arm 36a pivoted to the box-like frame and having a roller 36c engaging a slot 36d in a bracket 36e secured to the frame. Thus, combined rotation of the shaft 34a causes the frame first to rise and then descend. Initially the frame is in its lowermost position so that the first sheet is delivered from the conveyer 22 to the upper of the conveyers 38. The conveyers 38 are each driven, as they are aligned with the conveyer 22, by frictional engagement with a roller itself in frictional engagement with the conveyer 22. The storage unit is raised until each conveyer 38 has a printed sheet thereon. The next printed sheet is delivered to the lowermost conveyer 38 which is driven so that the sheet already on it is moved along to make room for the new sheet. The storage unit is thus lowered until all the conveyers 38 have two sheets thereon. The arrival of the third sheet for each conveyer 38 as the unit is again raised causes the first sheet on each conveyer 38 to be ejected on to a table the height of which is controlled in known manner.