Patent GB-927844-A (GB)
Title: Improvements in or relating to apparatus for the stencil printing of webs of cloth
IPC: B41L13/04
Filed: 1959-07-10
Abstract: 927,844. Stencilling-apparatus. A. F: CONCHON, and E. R. MASPERO. July 10, 1959 [July 10, 1958; June 19, 1959], No. 23828/59. Class 100 (2). Apparatus for stencil printing on webs of cloth comprises a power-driven rubber-covered central roll which serves to guide and drive cloth to be printed, a number of rigid stencil-printing rolls which are hollow to receive printing dyestuff and are grouped around the central roll, these rolls being mounted for rotation solely by their surface pressure through the cloth against the central roll, means interconnecting the rotation of the printing rolls with each other to ensure synchronous rotation, and separate means for each printing roll for automatically feeding dyestuff to each roll and for controlling the level of the dyestuff in each printing roll. The apparatus comprises a motor-driven central cylinder 9 around which a number of stencilling rollers 29 are positioned to print on a web of cloth which passes around the cylinder 9. A ring framework 3 supports fixed brackets 4 on each of which are bearings for a roller 29, these bearings being adjustable radially of, and tangentially to, the cylinder 9, and adapted to facilitate ready removal of the roller 29. A pressure roll 6 is urged against the cylinder 9 by a lever-operated cam 8. Each stencil roller 29 has two gears 11 in mesh with central gears 48 freely rotatable with respect to the cylinder 9. Stencil rollers: inking apparatus.-Each stencil roller 29 comprises a hollow sleeve portion having design areas therein through which a liquid dye can permeate, and is rotatably mounted by end rings on a fixed hollow mandrel 22, Fig. 1, which is open to atmosphere at one end and connected at the other end to a sealed dye reservoir 25 by pipes 23, 24. The pipe 24 leads from the base of the reservoir, through a motor-driven pump 39, to one compartment in the mandrel 22, and the pipe 23 leads from the air space in the reservoir to a second compartment in the mandrel, and both compartments are provided with horizontal pipe outlets within the body of the roller 29. The air space above the dye is also connected by a pipe 47 to a suction pump 46, and by a pipe 42 to mercury manometer 43 which constitutes a rheostat for the circuit of the motor of the pump 39, whereby a rise in pressure in the air space of the reservoir causes the pump to be driven faster. This arrangement ensures automatically that the correct liquid level in the stencil roller is maintained, since if the level in the roller is such that the outlet of the pipe 23 is not covered by the liquid, air can enter the space in the reservoir 25, and the rise in pressure therein causes the mercury in the right limb of the manometer to rise and thus start or increase the speed of the pump 39. The process of making a stencil roller 29 comprises the steps of taking a flat, tightly stretched screen of phosphor bronze, coating it with a sensitized solution, transferring the required design to the screen from a negative, rendering the impermeable parts of the design electrically conductive by a synthetic resin and electrically conductive paste, placing the screen in an electrolytic bath, and then cutting the finished design from the screen. The design is then wrapped around a solid cylindrical core, the edges of the pattern are joined, and end rings 53, Fig. 6, are provided, and the resulting shell is removed from the core and placed in a second electrolytic bath. Finally the shell is placed in a third electrolytic bath of chromium or nickel to render it more rigid and resistant to the chemicals employed in the printing dye. The complete cylindrical stencil 29 is removably mounted on the hollow mandrel 22 between end rings. Stencil roll mounting, and adjustment.-The shell of each stencil roll 29 has end rings 53, Fig. 6, each mounted releasably on a disc 30 rotatably mounted on the fixed mandrel 22. The disc 30 has three spring-urged pins 39 which engage holes in the end ring 53, and extensions of the pins pass through cam slots in an end ring 38, whereby when the latter is rotated, the pins 39 are released from the end ring 53 of the roll 29. The ring 38 is retained in one of two positions by a spring-urged balls 54 in the disc 30. A further disc 34, on which is secured a gear 11, is secured to the face of the disc 30 by screw and slot means, so that the gear can be adjusted relative to the design on the roll 29. The mandrel 28 of each stencil-printing roll 29 is mounted in bearings which are adjustable radially of the central roll 9 by screws on brackets 4, and the bearings are adjustable by micrometer means at right angles to the brackets.