Patent GB-1092489-A (GB)
Title: Improvements in or relating to sheet-fed printing presses
Inventor: OGDEN PETER JAMES
IPC: B41F33/14
Filed: 1965-05-05
Abstract: 1,092,489. Printing machines. VICKERS Ltd. April 27, 1966 [May 5, 1965], No. 19053/65. Headings B6B and B6C. An electrical system for controlling the tripping of the printing and auxiliary functions of a printing press, according to whether a sheet is presented correctly or is absent or incorrectly presented, comprises (a) a normallyclosed switch 4 operated by a sheet-sensing device so as to be maintained closed if a sheet is correctly presented to the feed mechanism, and opened if no sheet or an incorrectly positioned sheet is presented, (b) a relay 3 in series with the switch 4 and which when actuated changes over a switch 12 so as to cause energization of coils 9, 10 &c., changing over contacts 15, 16, 17 &c., to restore the parts of the press to operating position, and (c) two circuits comprising parallel switches 5, 6 and parallel switches 7, 8, 11 in series with the parts 3, 4. The switch 12 also causes energization of one of two relay coils 13, 14, the coil 13 when operative preventing presentation of a sheet to the machine and the coil 14 when operative allowing the presentation of sheets to the machine to proceed normally. The switch 5 is operated by a press-driven cam, the switch 6 is closed by relay 3, the switches 7, 8 are closed by the coils 9, 10, and the switch 11 is closed when a starting handle or switch is manually operated to close another switch and start the feeding of sheets to the press from a sheetseparating and forwarding mechanism 20, Fig. 2 (not shown). A cam-operated switch 18 controls the circuit of the sensing device so that the switch 4 is operated only during the period when a sheet is normally correctly presented. With the power supply at 1, 2 interrupted, all the switches are positioned as shown in Fig. 1, except that switch 5 may be open or closed depending on the position in which the machine has stopped. In this condition, the circuit of relay 3 is not completed and contacts 15 ... 17 are in tripping positions. If, now the machine is started, power is supplied to the circuit shown, and the aforementioned handle is operated to close the switch 11 and start the sheet-separating mechanism, the machine remains in tripped condition until a sheet reaches the feed mechanism of the machine, since the switch 5 is closed during and for a shorter time than the switch 18 controlling the sensing device is closed, and the switch 4 is opened by the sensing device as no sheet is present. When a sheet is correctly presented, the switch 4 is maintained closed during the period the switch 5 is closed, and the circuit of relay 3 is completed through switch 11. Energization of relay 3 causes closing of the switch 6 and the change-over of switch 12, the latter causing coils 9, 10 to close contacts 7, 8 and changeover contacts 15 ... 17 so that the parts of the machine are now in operative position, and at the same time rendering the coil 14 operative so that sheet feed proceeds normally. The machine now continues to run normally so long as sheets are correctly presented, since although the manual switch 11 is now released, contacts 4, 6, 7, 8 remain closed to complete the circuit of the relay 3 and the sheet-separating mechanism continues to operate as long as coil 10 is operative. If, however, absence of a sheet or an incorrectly positioned sheet is detected by the sensing device, the switch 4 is opened, the relay 3 is rendered inoperative, and contact 12 is changed over so that the machine is tripped and sheet separation and feed stopped. If, after initiation of tripping due to the faulty feed of a sheet, the sheet position is corrected due to the continuing movement of the feed tapes before they stop, relay 3 remains inactive and the machine remains tripped until the aforementioned handle is operated again. The relays 9, 10 could also be employed to disable a sheetcounter and a device spraying powder on to the printed sheets. The disabling of the printing mechanisms is not effected by the contacts 15 ... 17 alone but by these contacts in cooperation with cam-operated switches so as to cause the disabling mechanisms to operate at the correct times in the machine cycle. Speed-reducing mechanism.-When the coils 9, 10 are not energized, i.e. the machine is disabled, a switch 103, 104, Fig. 9 (not shown), causes a pilot motor to move the brush gear of the main motor so as to reduce its speed. Energization of the coils causes the main motor to be speeded up. Sheet-detectors; grippers; front stops.-The sheet-sensing device 25, Fig. 2 (not shown), may be photo-electric, supersonic or electromechanical, but as described, comprises two lamps 91, Fig. 8 (not shown), which direct two narrow beams of light towards areas of the lower end of a feed-table (22), which areas are spaced apart transversely of the sheet movement. If, and only if, both these beams impinge on a sheet correctly positioned in contact with front stops, light is reflected on to two photoelectric cells (95) causing a relay (97) operating the switch 4 to remain de-energized and the switch 4 to remain closed. If the sheet is incorrectly positioned the relay is energized to open the switch 4 thus causing the machine to be tripped as already described. The sheets 110, Fig. 10, are fed from the table to the machine by grippers 111, 123, one jaw 111 of which is fixed to and the other 123 pivoted on an oscillating lever 121. Fixed to the jaw 123 is a lever 124 carrying rollers 125, 125A and urged anti-clockwise by a spring. A camcontrolled arm 126 allows the grippers to close at the requisite time during normal operation of the machine. During such operation, a cam 128 pivoted at 140 and having a pin-and-slot connection 129 with arm 126 is moved away from roller 125A by a spring 143. If, however, a sheet is incorrectly fed or is missing, energizing of a relay coil 13, Fig. 1, causes a coil 162, Fig. 11 (not shown), to be energized, and a stop (152) to engage an arm (151) on pivot 140. Cam 128 then remains in operative position and closure of the grippers is prevented. An extension (161) of the stop (152) engages an arm (157) fast with the cam-operated front stop (115) and prevents the movement of the stop (115) to inoperative position under spring action. Cylinder trips.-The machine described is a multicolour litho offset printing machine, and each offset cylinder 27A, Fig. 3 (not shown), is tripped when the machine is disabled as described in connection with Fig. 1. For this purpose, the shaft (27c) of the cylinder is eccentrically mounted in a bush (45) rotated by links (49, 50) from a shaft 51, Fig. 4. Fixed to the shaft 51 is an arm 52, having pivoted thereto a double pawl 53, 54. Rotatably embracing the shaft 51 are two arcuate plates 55, 56 the right-hand ends of which are periodically moved towards one another by a linkage operated by a cam 60. With the pawl in the position shown in Fig. 4, the plate 55 during its movement engages the pawl part 53 and rotates the shaft 51 so as to cause disengagement of the offset cylinder from the plate and impression cylinders. If, however, the pawl is moved clockwise from the position shown, the pawl part 54 is engaged by the plate 56 and the shaft 51 is rotated to move the offset cylinder to printing position. The position of the pawl is determined by two solenoids 63, 64, Fig. 5 (not shown), causing respectively anti-clockwise and clockwise movement of the pawl, the solenoid (63) being energized when a contact such as 15, Fig. 1, is in the position shown in that Figure, i.e. no sheet is being correctly presented, and the solenoid (64) being energized when the contact is changed over due to sheets being correctly presented. Inking and damping apparatus each includes a roller 69, Fig. 6, to which ink or damping fluid is transferred by a messenger roller 71 from a supply roller 78. The roller 71 is carried by an arm 72 fixed to a shaft 73 oscillated by a cam 74 through a linkage 75 ... 77. If the machine is disabled, i.e. contacts 15 ... 17, Fig. 1, are in their upper position, one of the contacts causes a solenoid 82 to be energized so as to move a catch 81 into the path of a projection 80 fixed to the shaft 73 so as to stop the supply of ink or fluid.