GB801347A - Improvements in or relating to sheet feed apparatus for a press - Google Patents

Abstract

801,347. Feeding sheets. MILLER PRINTING MACHINERY CO. Feb. 4, 1955, No. 3336/55. Class 100(1) In a printing press, such as a rotary multicolour offset lithographic press, sheets are fed from a feed table A, Fig. 1, to an impression cylinder I by periodicallydriven feed rollers R and then by grippers G on a transfer cylinder T, and preliminary stops K mounted on the feed table are adapted to arrest temporarily the movement of a sheet prior to the feeding thereof by the rollers R. The apparatus also includes means for tripping the offset cylinder B in cases where a sheet is not present on the table A, or has been fed thereto incorrectly, and the grippers G include registration stops which can be adjusted to compensate for irregular front edges on sheets. As shown, each sheet is fed from a pile by a separator F on to the table A having conveyer tapes which feed it up to the preliminary front stops K. Side registration means J act on the sheet, and then feed rollers R, comprising upper idler drop rollers 37, Fig. 9, and driven lower rollers 31, feed the sheet at a speed greater than the peripheral speed of the transfer cylinder T, to abut the front edge of the sheet against stops 72 on pads 48 carried on a flexible bar 57 on the cylinder T. The sheet is gripped by grippers G, pulled away from the board A by the cylinder T, taken by grippers on the impression cylinder I to be printed by the co-operating blanket cylinder B, and delivered by a collecting cylinder C and conveyer D to a delivery pile. The lower feed rollers 31 comprise discs, having incomplete typres 36 thereon, secured to a shaft 32 which is oscillated by gearing driven from an arcuate toothed rack which is oscillated by a cam on the shaft 46 of the transfer cylinder T. The drop-feed rollers 37 are discs each rotatably mounted on a stub shaft 38 carried by a cantilever 39 which is pivotally mounted on a transverse shaft 40, each cantilever being capable of being latched in inoperative position, and lifted periodically by a collar secured to the shaft 40. The shaft 40 is rocked, against the action of a spring, by a cam on the shaft 46 to raise the rollers 37. The oscillating preliminary stops K, such as K16, Fig. 9, are each secured to a cantilever, such as 21, secured to a cross shaft 13 which is also rocked, against the action of a spring, by a cam on the shaft 46. The grippers G comprise fingers 47 secured to a shaft 50 mounted in the transfer cylinder T and rocked by an end follower from a cam fixed to the machine frame. Each gripper pad 48 is mounted on the flexible cross bar 57 by a screw 58, and the bar 57 is adjustably secured to the cylinder by three screws-passing through slots in the bar at the two ends and near the middle. A leaf spring urges the mid portion of the bar forward, and three micrometer adjusters mounted on the cylinder are arranged to flex the bar so that the pads 48 carrying the registration stops 72 for the sheets S can be adjusted to suit sheets having concave, convex, or slanted front edges. Sheet-guides. A sheet-guide 74 is moved bodily upwardly before the feed rollers R operate to guide the sheet towards the stops 72 in the grippers G of the transfer cylinder T. This guide ensures that the sheet is bowed upwardly, as at X, Fig. 9, when the front edge engages the stops. Faulty sheet-feed control devices. Two similar detector fingers are carried by two of the intermediate preliminary front stops K. The cantilever 21 of such a stop is slotted and provided with a pin 120 from which depends a pendulum finger 121 which rests against the base of a slot in the table A. A sheet S swings the finger upwardly before striking the stops K. If a sheet is absent or has not reached the stops K at the correct time, the end of the finger 121 will remain in the path of a tappet lever 115 and impede its oscillation, and this will prevent a shaft H from rocking and thus cause know mechanism to trip the offset cylinder B. Furthermore, if the shaft H is prevented from rocking, it cannot cause the oscillation of a lever carrying a stop which lies in the path of movement of two further levers. These two levers are connected, respectively, to the shafts 13 and 40, so that the front stops K do not rise, and the feed rollers 37 cannot fall to co-operate with the lower driven rollers 31. In the case where a sheet is overfed, i.e. fed along the table A beneath the then raised stops K, these stops, in their normal descent, strike the upper surface of the sheet, depress it below the table A, and so cause the depression of a detent arm to impede the oscillation of a tappet lever. This prevents the oscillation of the shaft H, causes the offset cylinder B to be tripped, and further movements of the stops K and drop feed rollers 37 are prevented. Specifications 801,348 and 801,349 are referred to.