Patent GB-120357-A (GB)
Title: Improvements in or relating to Offset Web Mechanisms for Printing Presses.
IPC: B41F23/06
Filed: 1918-06-28
Abstract: 120,357. Goss Printing Press Co., (Goss Printing Press Co.). June 28, 1918. Set-off, preventing; stopping and tripping arrangements; driving machines. - A set-off web mechanism comprises means for feeding the web round an impression cylinder at the same surface speed as that of the printing and impression cylinders during the printing operations, and means operated independently of the means for driving the printing mechanism for drawing and re-winding it back when the impression cylinder is tripped out of contact with the forme cylinder, means being provided for stopping the machine and tripping the impression cylinder when the supply roll of the web is exhausted or when the web breaks. A multiple press arrangement is described wherein, if one of the set-off webs breaks when moving in either direction, the remaining webs are rewound. Special web-tensioning devices arc provided. As shown in Fig. 1, the set-off web 31 passes round the impression cylinder 18 inside the web 17 which is being printed by the forme cylinder 16. The cylinder 18 is in eccentric bearings 21 by which it may be tripped away from the cylinder 16, the bearings 20 being operated by arms 22 connected by rods 23 to arms 25 fixed on a shaft 27. A strong spring 28 on one of the rods 23 normally holds the cylinder 18 in operative position against the cylinder 16. The set-off web 31 is wound on two rolls 34 and 39. The roll 34 which winds the web during printing rests on two driving-rollers 35, 36 and is mounted in slide blocks 37 movable vertically on guides 38. Similar driving-rollers 40, 41, blocks 42, and guides 43 are provided for the roll 39. The rollers 35, 36 are uriven by bevel gears 48, 49 from a shaft 50 driven in timed relation to the speed of the press by a gear wheel 51 which drives the shaft 50 through a clutch 52. An arm 250 on the shaft 27 is connected to the movable part of the clutch 52 so that, when the cylinder 18 is moved away from the cylinder 16, the clutch is opened and the shaft 50 and rollers 35, 36 stopped while the press gear and gear 51 continue to rotate. The rollers 40, 41 are driven for re-winding the web back on to the roll 39 at a high speed by bevel gears 58, 59 from a shaft 60 driven by gears 61, 63 from a separate electric motor 64 through a clutch 62. A rod 66 connects the arm 250 to a pivoted arm 65 which operates the clutch 62, so that, when one clutch is operative, the other is open. The arms 65 and 250 are moved to the left in opposition to the spring 28 'by a lever 67 connected to the arm 65 by a lateh-arm 68, held depressed by the heavy armature 79 of a solenoid 80 so that the latch is normally clear of the lateral projection 69 on the lever 67. A spring 74 holds the lever 67 to the right, and it is moved to the left when the latch arm 68 is raised by a spring 70, by a cam 72 on the gear 61. The spring 70 raises the latch when permitted by the energizing of the solenoid 80 and lifting of its armature 79. When thus moved to the left to engage the re-winding clutch 62, the arm is held in that position, until the latch 68 is again depressed by the armature 79 along with the latch 68. A dash-pot 86 controls the movement of the arm 250. During the printing movements, the shaft 50 is driven by the gear 51, and. the shaft 60 is rotated in the opposite direction by the pull of the web 31 on the rollers 40, 41. During the re-winding, the shaft 60 is driven by the motor 64 and the shaft 50 is rotated in the opposite direction by the pull of the web 31. The shafts 50, 60 are in line and bevel gears 87, 88 on their ends engage bevel pinions 90, 91 on a rotatable head 89, so that, when the two shafts are moving at the same speed, the head 89 remains at rest. When one of the shafts 50 or 60 is rotated at a greater speed than the other, the head 89 is rotated, and on the other hand, if the head is locked against rotation, the shafts are constrained to rotate at the same speed. A brahing-device is automatically applied to the head 89 to cause the speeding up of the slower-moving shaft and relieve the abnormal tension of the web 31. This brake 107 is controlled from a heavy roller 92 carried by arms on a shaft 97 and resting in a loop of the web 31. An arm 98 on the shaft 97 is provided with a cam piece operating an arm 99 on a sleeve 109 when the roller 92 is lifted by au increased tension of the web, and the brake 107 is thereby applied if the rod 66 and arms 250, 65 are in the re-winding position as shown in Fig. 1. When the arms 250, 65 are moved to the right for the printing operation, this brake device is rendered inoperative by an incline 104 on the rod 66. The shafts 50, 60 also are provided with brakes 111, 112 similar to the brake 107 of the head 89, operated by an arm 118 on the shaft 117. This arm 118 is moved by the cam projection on the arm 98 when the roller 92 falls owing to reduced tension, and one of the brakes 111, 112 is applied according to the position of the rod 66 and inclines 114, 116 theron. The application of the brake 111 slows up the roll 34 to tighten the web, while the application of the brake 112 slows up the roll 39 for the same purpose. The printing-press is driven by an electric motor in a controlling circuit including a, switch A operated automatically by an arm 119 engaged by one of the blocks 42 so as to stop the machine when the roll 39 is nearly exhausted, and the motor 64 is in a circuit including a switch B operated by an arm 121 and a block 37 to stop the rewinding when the roll 34 is exhausted. Means is provided for stopping the main press motor or the motor 64 on a breakage of a set-off web. This comprises sliding rods 123, 124 adapted to engage arms 125, 126 to open the switches A, B. These rods are pivoted to bell-crank levers 127, 128 connected by a rod 129 with one of the arms carrying the roller 92. Suitable controlling circuits are described, both for a single web 31, as shown in Fig. 1, and for a number of sections of a. multiple press each having the arrangement shown in Fig. 1. The circuit of the motor 64 includes the solenoid 80 which is energized to attract the heavy armature 79 and so release the latch 68 when the circuit of the motor 64 is closed. When the main press motor circuit is broken, a solenoid therein releases an armature to close the circuit of the motor 64. In addition to the switch A and usual hand-operated switches, the press motor circuit includes a switch C held closed by a lug 139 on the arm 250 in its right-hand position, and opened by a spring to break the circuit when the arm moves to the left as shown in Fig. 1.