Patent GB-988711-A (GB)
Title: Stencil printing machine
IPC: B41F15/08
Filed: 1962-01-25
Abstract: 988,711. Stencilling apparatus. SOC. ALSACIENNE DE CONSTRUCTIONS MECANIQUES. Jan. 25, 1962 [Jan. 26, 1961], No. 2879/62. Heading B6C. A stencilling machine comprises an elongated table 101 to which a sheet of material 109 is adhered, a carriage 103 supported for longitudinal displacement over the table, a frame carrier 104 having a printing pattern frame 171 carrying a screen 205 and supported on the carriage 103 for movement between a printing position in engagement with the material on the table and a raised position, a squeegeecarrier 105 supported for horizontal traversing displacement across said frame carrier when in printing position to apply a printing substance through the stencil to the material, and control means for imparting to the carriage, the frame carrier and the squeegee-carrier a cyclic sequence of displacements including: advancing the carriage 103 in steps to a series of preset positions spaced along the table; at each step moving the carrier 104 to printing position, traversing the squeegee-carrier 105 across the carrier 104, and moving the carrier 104 back to raised position; and returning the carriage 103 to an initial position on the table after a last step of advance. The carriage 103 is mounted at its corners on flanged wheels 111, 112 and rollers 116, the former being traversable along a rail 113, Fig. 3, associated with one side of the table 101 whilst the latter are movable along a flat support 117 associated with the other side of the table. The carriage mounts a motor 128 which, through a friction clutch, a reducer gear 129, and a belt drive 131, 132 and 133, coupled to the wheel 111, drives the carriage along the table. In order to accurately adjust the elevation of the carriage above the table and to allow a given carriage to be adapted for tables of different widths the rollers 116 are mounted on arms 121 each having a back 122 secured thereto which is slidable upon, and pivotal about a bar 123 extending longitudinally along a side of the carriage 103 and secured at both ends by way of lugs 125, 126. The frame carrier 104 comprises a framework of tubular members 136, 137, 138 and 139 which is secured at each corner to the carriage 103 through a helical cam device, Fig. 4, in which a cylinder 143 having a helical cam-way 144 and carrying a horizontally disposed sprocket 158 is rotatably mounted on the frame 103, the cam-way locating a roller 146 fixedly mounted on the carrier 104. Rotation of the cylinders 143 is effected by an endless chain 163 which is driven by a motor 159 through a friction clutch and a speed-reducer 161 and carries a member 266 which engages, at the limits of travel of the carrier 104, limit switches IV and VII mounted on the carriage 103. Actuation of these switches de-energizes the motor 159. The carrier 104 supports a stencil frame 171 through lugs 172, 173, 174 projecting therefrom and resting on members 176, 177 which are supported on the tubes 138, 139 for longitudinal displacement relative thereto. A squeegee-carrier 105 is movably supported on the carrier 104 through rollers 181, 182, 183, 184, 185 in contact with the carrier members 136, 137 and is reciprocable across the carrier 104 by a drive from a motor 187 through a reducer gear 188, a sprocket 189, a chain 191 and a sprocket 192. The motor 187 is mounted on the carrier 104 and the chain 191 is connected to the carrier 105 at 194, Fig. 1. A rubber squeegee 196 is universally connected through a mount 197 to the lower end of a vertical rod 199 which is carried in a downwardly spring-biased manner by a support 201 upstanding from the carrier 105. Stop plates 202 attached to the mount 197 limit the angular inclinations of the squeegee through abutment with the walls of a slot 203 formed in the carrier 105. The spring tension thrusting the squeegee downwardly may be adjusted through actuation of a pair of lock-nuts 211, 212, whilst an air damper device 215 associated with the squeegee is provided to control its vertical motion. The squeegee is lifted off the stencil at each end of its horizontal stroke through the interengagement of follower rollers 222 on the rod 199 with ramps 221 and 226 mounted through shockabsorbing arrangements on respective opposite sides of the carrier 104. Each ramp is pivotally attached to a bar 224 or 228 such that the rollers 222 after moving up the ramp drops into a rest member 227 and remains there until the carrier 105 starts moving in the opposite direction when the rollers effect pivotal displacement of the ramp to allow unimpeded the downward movement of the rollers. Limit switches V and VI, actuable by members 267, 268, carried by the carrier 105, to stop the motor 187, are mounted adjacent each ramp 221 or 228. A rail 256 located to one side of the table 101 carries a series of stops 255, each being placed at a printing station. The carriage mounts a device having a solenoid controlled arm 249 which is adapted to engage selected stops 255 to thereby effect arrest of the carriage at particular stations. Although the carriage has switches enabling operation of the machine to be effected through an operator the machine incorporates electrical control systems such that it is fully automatic. Through switch control, the switchboards 238, 239 being embodied in the carriage 103, the carriage may be automatically stopped at alternate stops 255, a printing operation then ensuing, the squeegee effecting a single sweep either to the right or the left, depending upon its " end of stroke position " at the previous printing operation. On the other hand, the squeegee may be set to effect " a double sweep " at each operation. At the end of its travel the carriage actuates a limit switch I, the effect of which is to reverse the carriage drive such that it returns to its initial position at high speed where it is arrested through actuation of a switch II. A new run is then initiated, the carriage being advanced manually one step to thus effect printing at the stations skipped during the first run. Any pattern of step progression may be employed, it being possible to stop the carriage at each stop 255 if desired. The frame carrier is mountable on the carriage 103 in either one of two mutually perpendicular positions depending on whether it is desired that the squeegee shall sweep across the warp or weft of the material 109. In a modification, the carrier 104, Fig. 6, is pivotally mounted about its front edge, the cam devices, actuated by a chain drive from a motor 297, being provided at the two rear corners.