GB1048150A - Improvements in and relating to dual-head offset printing-machines - Google Patents

Abstract

1,048,150. Offset printing machines. ADDRESSOGRAPH MULTIGRAPH CORPORATION. Dec. 21, 1964 [April 15, 1964], No. 51870/64. Heading B6C. In a rotary offset printing machine comprising first and second printing heads connected in tandem and driven in unison to perform two sequential printing operations on each of a plurality of paper sheets an automatic sequence control apparatus is incorporated for virtually controlling all the machine operations. The machine shown comprises a sheet feed mechanism 34 of the vacuum type, a conveyer table 35, an offset printing head 31, a conveyer 32 which also turns the once-printed sheets over and an offset printing head 61. The head 31 incorporates an inking apparatus 33, a plateetch applicator 36 controlled by an operating handle 37, clamping means 39, a control handle 43 and an automatically controlled blanket cleaner 41. The printing head 61 includes the usual cylinders-as does the head 31- and an inking mechanism 63. Also incorporated is a plate-etch applicator 66 controlled by a handle 67 having a control switch 38. Damping solution is applied by an applicator 69, the blanket of the head being cleaned by an automatically controlled cleaner 71. A control handle 73 is provided for manual control of the principal machine operations other than plate etch application. Associated with the sheet feed mechanism 34 is a sheet counter 44 whilst the printing head 31 also carries the control panel 42 of the machine. In operation, the machine operator sets the counter and starts the machine by actuating the switch 38 in the handle 67 associated with the head 61. At the same time the operator pivots the handles 37, 67 from their " off " positions shown in Fig. 1 to initiate operation of the plate etch applicators 36, 66. Plate etching is manually controlled in both heads and the number of machine cycles required to apply the etching solution to the masters is left to the discretion of the operator. After the plate etching both handles are released to return to their initial positions. When the handle 67 reaches its " home " position it actuates a control switch, whereby automatic sequential operation of the machine is initiated. As a first step the damping solution is applied to the masters for one machine cycle and then the masters are inked for several cycles. Next the blanket of head 31 is imaged for five or six cycles and after two or three " imaging " cycles the sheet feed mechanism 34 is actuated so that the first sheet of paper will be fed to the head 31 at the time that the blanket imaging operat ion is finished. Thus, the machine commences printing the sheets and this is continued until the automatic control halts this process. The blanket of the second head 61 is imaged a predetermined number, e.g. three, machine cycles after such imaging has been initiated in head 31. When the counter 44 registers the required number of copies the automatic control stops the feed mechanism 34. Imaging of the blanket in the head 31 is then interrupted, but ink transfer to the blanket is continued for a further period of time, e.g. three machine cycles. In the next cycle of operation both ink mechanisms 33 and 63 are interrupted whilst in the following cycle the damping applicators 36 and 66 are disengaged from respective master cylinders. Subsequently, the blankets are cleaned by cleaners 41 and 71 for, say, ten machine cycles. Thereafter the machine 30 is stopped entirely and the masters ejected from their associated cylinders by solenoid-operated master ejection devices of the kind disclosed in Specification 946,357. The sheet feed mechanism 34 may be of the kind described in Specification 915,002.