Patent GB-483735-A (GB)
Title: Improvements in or relating to impression mechanism for rotary photogravure printing presses
IPC: B41F9/18
Filed: 1936-09-25
Abstract: 483,735. Printing-machines. JACKSON, L. MELLERSH-. (Goss Printing Press Co.) Sept. 25, 1936, No. 26078. [Class 100 (ii)] A rotary photogravure printing - press of the kind in which the impression roller 24 is pressed against the printing-cylinder 20 by means of a counter-pressure cylinder 25, is constructed so that the counter-pressure cylinder 25 can be raised and lowered by automatic power means such as a motor for raising and lowering the impression roller 24 while permitting a limited relative movement between the cylinder 25 and roller 24. Each end of the cylinder 25 is independently mounted in slides 27 which move in guides in side frames 21, 22, and the slides 27 are raised and lowered, either independently or together, by means of screwed rods 50 connected by blocks 51, Fig. 2a, to the slides. The cylinder 25 is mounted at each end in self-aligning anti-friction bearings 26, and the roller 24 is mounted in lever arms 180 pressed outwards by springs 198 to an extent limited by nuts 196 on studs 194 which engage apertures in extensions of the arms 180. The roller 24 can thus move relatively to cylinder 25 to a limited extent. The rods 50 are movable vertically by means of threaded sleeves 53 which are keyed to threaded sleeves 52 driven by worm wheels 115 and worms 119 free on a shaft 110, Fig. 3, which can be operated by a hand-wheel 112, or by a motor 114 under control of a clutch which selectively permits actuation of either of the worms 119, and permits also in the normal position of the clutch-operating lever 142, simultaneous operation of both worms, and equal raising and lowering of both ends of the cylinder 25. The pressure of the cylinder 25 on roller 24 due to the weight of the cylinder is supplemented by a relatively heavy adjustable coiled spring 70, Fig. 2, which presses on a seat 72 supported on a shoulder 80 of a split collar 81 clamped to a sliding cylinder 73 which protects the spring. The collar 81 is screwed to a bell 85 fitted with a ball thrust bearing 86 supported on a cylinder 87 near the upper ends of the sleeve 53. The force of the spring reacting against a cross member 78 is applied to the screw 50 through sleeve 53, ball bearing 86, bell 85 and collar 81, and by adjustment of the collars 81 by turning-bars the printing pressure can be varied. The worm gearing 115, 119 is mounted in oil in an oil-tight casing 97, and oil-retaining rings 98 are fitted on the rods 50 which are enclosed in accordion pleated covers 100 to protect the cylinder 25 from oil. Limit switches 205, 220, Fig. 1, are operated by projections 207, 222 on the slides 27 to cut off the current to the motor 114 when the slides are in their highest and lowest desirable positions, the projections 222 being adjustable to suit rollers of different diameters. A further switch 247 is provided to cut off the current when the compression of spring 70 reaches its upward desirable limit. This is operated by a pressure-indicating device 237, 239 operated by a spring-raised lever 234 engaging the under side of the collar 81, and indicates when the collar 81 has compressed the spring 70 to the desired extent. A dial micrometer 249 is operated by an arm 256 which moves with the slide 27 and gives a visual indication of the exact position of the cylinder 25. The impression roller 24 is arranged to be cooled by water introduced through a pipe 178, Fig. 2a, and a packed joint and a bore in end of the roller. The roller is adapted to be removed from its split bearings when desired, and it can be passed out of the machine over fixed tracks and tracks formed on bellcranks 200 pivoted to each arm 180 and normally held out of operative position by resilient clips 205 projecting downward from fixed brackets 182. The construction is adapted to provide an even pressure along the whole length of a fractional width impression roller, or when using fractional width paper rolls. In either case the pressure cylinder is set so that the idle end is slightly higher than at the printing end.