GB993911A - Improvements in or relating to web-feb printing machines - Google Patents

Abstract

993,911. Feeding webs. FORMMASTER Ltd. March 16, 1962 [March 16, 1961], No. 10906/61. Heading B6B. The web-feeding means of the printing machine of Specification 950,053, is driven by a mechanism comprising a continuously rotatable shaft 146, a shaft 72 coupled to the feeding means, an electrically operable clutch between the shafts, switch means controlling the clutch, a programme member driven in synchronism with the blanket and impression cylinders 44, 45 of the machine and operable on the switch means to effect engagement of the clutch each time the web feed is to start and a cam 312 also driven in synchronism with the said cylinders and operable on the switch means to effect disengagement of the clutch each time web feed is to stop. The clutch comprises an epicyclic gear mechanism having an intemally-toothed annulus 300 secured to the shaft 146, which shaft mounts a numbering cylinder 46 and is continuously driven from the cylinder 45, a sun-wheel 301 rotatable on the shaft 146 and planet wheels 302 on a rotatable planet carrier 304. The sun-wheel 301 is attached to a sprocket 305 connected by a chain 306 to a sprocket 307 fixed on the shaft 72. A ratchet wheel 308 is secured to the carrier 304 and a pawl 310 operated by a solenoid 311 is engageable with the ratchet teeth. When so engaged, the shaft 146 drives the shaft 72, which drives web-feeding rollers 33, 48, through the epicyclic gear and the chain drive. The switch means comprises micro-switches 320 and 335 whilst energization of the clutch through the solenoid 311 is controlled by a relay 321 having self-holding contacts 322 and solenoid controlling contacts 323. The programme member comprises an endless flexible belt 328 which is driven by a pin wheel 329 having pins 330 engaging in holes 331 in the belt, the wheel 329 rotating continuously with the cylinder 45 and being driven by gears therefrom. The belt has a notch 333, or notches, in one side edge and this edge runs against an operating roller 334 of the switch 335. The electrical supply to the controlling mechanism is through a potentiometer 350. In operation, when the engagement of the notch 333 with the roller 334 allows the movement of the latter to energize the relay 321, the contacts 322 and 323 close to hold the relay regardless of the fact that the notch 333 and roller 334 have disengaged and to energize the solenoid 311 and a solenoid which releases an electromagnetic brake on the shaft 72. The pawl 310 thus engages the ratchet 308 to lock the carrier 304 such that the shaft 146 drives the web-feeding means through the shaft 72. On the completion of the web feed operation the cam 312 on the shaft 146 allows a spring-loaded lever 316 to pivot anticlockwise thus opening the switch 320 and breaking the power supply to the relay 321. This allows the pawl 310 to withdraw from the teeth 308 and the braking of the shaft 72. Positive arrest of the latter shaft is ensured by the engagement of a finger 318 on the lever 316 with a detent 314 in a wheel 313 keyed to the shaft 72. The pawl 310 is mounted on a rockable shaft 340 and as the lever 316 pivots anticlockwise the engagement of a slot 343 in the end of a link 344 carried by the lever with a pin 342 on a member 341 fixedly mounted on the shaft 340, effects positive withdrawal movement of the pawl from the ratchet teeth 308. The arrangement of cam 312, lever 316 and wheel 313 is such that the web-feed shaft 72 is free for rotation during a major portion of each revolution of the shaft 146 and is positively held and located at a precise position once during each revolution.