GB2170785A

GB2170785A - A sheet printing machine

Info

Publication number: GB2170785A
Application number: GB08526064A
Authority: GB
Inventors: Willi Weisgerber; Michael Alan Whelan
Original assignee: Miller Johannisberg Druckmaschinen GmbH
Current assignee: Miller Johannisberg Druckmaschinen GmbH
Priority date: 1985-02-09
Filing date: 1985-10-22
Publication date: 1986-08-13
Also published as: AT395393B; SE8504213L; CS672985A2; DE3504435A1; NL8502308A; GB8526064D0; JPS61182952A; JPH0519906B2; IT1200110B; FR2577172A1; IT8548527A0; GB2170785B; ATA301085A; CS262423B2; DD239162A5; CH668938A5; SE8504213D0

Abstract

The register bar of a sheet printing machine is mounted on a first roll (2) of said machine, itself carries a plurality of sheet abutments (4) and (5) is adjustable into and out of its normally straight configuration by at least three adjusting screws, (7, 8, 9) of which two (7, 9) engage the register bar (5) in the region of the two ends thereof and one (8) engages it in the centre, each of the adjusting screws (7, 8, 9) being rotatable by remote control, by a respective control motor (10) disposed in the first roll (2) of the printing machine. In such sheet printing machines the individual sheets are accelerated from a preliminary alignment rest position to the peripheral speed of the roll (2) or higher. The roll (2) may be a printing roll, of ceder drum or other roll disposed upstream of the printing roll. Hitherto the setting of the adjusting screws had to be made manually. <IMAGE>

Description

SPECIFICATION A sheet printing machine This invention relates to a sheet printing machine in which individual sheets of paper are accelerated from a preliminary alignment rest position to the peripheral speed, or to a speed which is somewhat higher than the peripheral speed, of a first roll of the printing machine. The first roll may be the printing roll itself or a special feed roll which is disposed upstream of the printing roll. This first roll has a plurality of abutments or feed marks for the paper sheets, which abutments are carried by a register bar. The register bar is adjustable out of its normally straight configuration by at least three adjusting screws, two of which engage the register bar in the region of the two ends thereof and one of which engages the register bar in the middle thereof.

In many cases, the sheet feed speed, which depends primarily on the nature of the material to be printed, is somewhat greater than the peripheral speed of the first roll of the printing machine so that the sheet, being braked by the paper abutments, bulges upwardly and forms a kind of hump before, being entrained by roll grippers, it is applied around a cylinder of the machine. The cylinder is intended to ensure that the sheet bears smoothly against the paper abutments or feed marks.

The roller-type feed system or other gripper-less feed systems in which the paper abutments or feed marks are disposed on the rotating feed roll have the advantage, in comparison with a swing-type feed system or other systems which operate with grippers, that it can be used with sheets in which the leading edge of the sheet may not only be a completely straight contact line, but also may be of concave, convex or slanting configuration.

For this purpose, particularly for many kinds of material to be printed, it is necessary for the sheet feed speed to be greater than the peripheral speed of the roll, which is referred to as 'overfeed'. The deformation of the leading edge of the sheet which occurs at first contact is intended to counteract certain defects which can occur in sheet printing and particularly in offset printing. One of the causes of defects, and this is irrespective of the mode of printing, is trimming differences in the sheets.

Another cause of defects occurs only in offset printing. It depends, inter alia, on the influence of the wetting agent and produces a dimensional alteration in the sheet size, predominantly and increasingly in the trailing region thereof. As the sheet passes through the printing machine therefore, the form of the sheet, with the printed image, changes, and therewith also its position relative to the print image on the printing plates. This problem is particularly serious when for example printing is effected with two or more passes through the machine. In fact, some time elapses between the individual printing operations, and in this connection the 'fanning-out' of the image on the sheet is particularly clear if the paper run direction is incorrectly selected.Further reasons for dimensional variations in a sheet being printed involve the contact pressure to which the sheet is exposed in the printing zones. Other factors which have an influence on the sheet to be printed are the climatic conditions and variations within the room in which the printing machine is located.

In order to compensate for such causes of faults it is known for the paper abutments in the feed cylinder to be moved into a slightly concave or convex form, which form must then necessarily be matched by the leading edge of the sheet. That therefore counteracts the dimensional variation in the sheet.

In the known roll feed systems, the register bar which carries the paper abutments is designed to be bendable as a whole and is provided at its two ends and at its centre with respective adjusting screws, giving therefore a total of three adjusting screws. Adjustment by means of the three adjusting screws gives a concave or convex line which corresponds substantially better to the desired geometrical shape and which is a continuous curve without sudden changes, being the line on which the paper abutments then lie. When making an adjustment, usually only the middle adjusting screw is operated. The two outer adjusting screws can be used if displacement at one side, giving therefore an inclined position, is desired in a particular situation.However, that construction in turn suffers from the disadvantage that the machine must be shut down each time adjustment is required and started up again after the adjustment has been made, and then a check has to be made that the adjustment made is successful. This procedure sometimes has to be repeated a number of times because the desired result is certainly not achieved in every case when making the first adjustment.

There is thus a need for a generally improved sheet printing machine which eliminates or minimises the above discussed disadvantages. Additionally there is a need for a machine in which subsequent adjustment is possible even when the machine is running and which permits immediate observation of the result of the adjustment made, while the desired form of the arrangement of the paper abutments, either concave, convex or also oblique, is also maintained.

According to the present invention, there is provided a sheet printing machine in which individual sheets are accelerated from a preliminary alignment rest position to the peripheral speed, or to a speed which is somewhat higher than the peripheral speed, of a first roll of the printing machine, which first roll is a printing roll or a feeder roll, wherein the first roll has a plurality of abutments, for the sheets, carried by a register bar, wherein the register bar is adjustable into and out of its normally straight configuration by means of at least three adjusting screws, a first of which engage the register bar in the region of one of the ends thereof, a second of which engages the register bar in the region of its other end and a third of which engages the register bar in the region of the middle thereof, and wherein each of the adjusting screws is rotatable by remote control by its own individual control motor, which control motors are disposed in the first roll of the printing machine.

Preferably an indicator means is provided for indicating the actual setting adopted by each adjusting screw and, in automatic operation, for switching off the control motor when the desired actual setting is reached.

This eliminates the fairly laborious operation of manually adjusting the adjusting screws, and adjustment can be carried out while the machine is running. it is also possible, while the machine is running, to vary the gripper "white", in regard to dimensions, to compensate for variations in cut edges, and to vary the degree to which the paper is subject to deceleration (giving rise to a humped configuration thereof).

The control motors may be automatically controllable by regulating signals, by a colour register regulating means which compares image edges or special printing lines or adjusting marks.

For ease of movement and prevention of tilting of the register bar, it is recommended that the adjusting screws be mounted in rolling bearings sub stantiaily without radial and axial play in the register bar.

For a better understanding of the present invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a plan view of part of a first roll of a printing machine of the invention in which a register bar with sheet abutments is installed, and Figure 2 is a view in radial section through the first roll, along line ll-ll in Figure 1 to an enlarged scale of one of the adjusting screws with its control motor and other associated components.

A printing machine of the invention includes a first roll 2 which may be the printing roll itself or another feeder roll which is disposed upstream of the printing roll to which sheets 1 are applied. In the illustrated embodiments, the sheets, preferably of paper, are applied by a roll-type feed system 3 but the design of the sheet feeder system is not part of the present invention The first roll 2 of the sheet printing machine, on which the sheets 1 are laid, has a plurality of sheet or paper abutments 4 which are all secured to a register bar 5 which is mounted in a recess 6 in the roll 2, being a close fit but displaceable therein.

The register bar 5 is adjustable in position by three adjusting screws 7, 8 and 9, so that it can also be set in a concave or convex or even oblique position, with the register bar 5 being elastically deformable for that purpose. The setting of the adjusting screws 7, 8 and 9 is effected by control motors 10 associated one with each screw and disposed in the roll 2. Each control motor 10 drives a gear 12 by way of a pinion 11 which is fixedly connected to the shaft of the motor 10. Each gear 12 is fixedly connected to the respective associated adjusting screw 7, 8 or 9 or is formed in one piece therewith.As each adjusting screw 7, 8 and 9 is provided with a screwthread 13 which co-operates with a corresponding female screwthread in the roll 2, rotation of the adjusting screws 7, 8 and 9 by the control motors 10, by way of the pinions 11 and the gears 12, produces an axial movement of the respective adjusting screw and thus a corresponding movement of the register bar 5. Each of the adjusting screws 7, 8 and 9 is preloaded in one direction by a compression spring 14 and, between the adjusting screw shank and the register bar 5 and the thrust rolling bearings 18, 19, by plate springs, thereby compensating for play. A ball 15 is provided between each compression spring 14 and the shank of the associated adjusting screw.

Each adjusting screw 7, 8, 9 is easily rotatable substantially without axial and radial play, in rolling bearings 20 and 21, and is also mounted in the register bar 5 in such a way as to be prevented from tilting.

The machine also has an indicator means for indicating the actual setting adopted by each of the adjusting screws 7, 8 and 9. In automatic operation and when the desired actual setting is preselected, the indicator means also serves to switch off the control motor 10 of each adjusting screw when it has reached the desired actual setting. The components which form part of said means are not iliustrated in the drawings; they are generally known and may therefore be of any desired known construction.

Claims

1. A sheet printing machine in which individual sheets are accelerated from a preliminary alignment rest position to the peripheral speed, or to a speed which is somewhat higher than the peripheral speed, of a first roll of the printing machine, which first roll is a printing roll or a feeder roll, wherein the first roll has a plurality of abutments, for the sheets, carried by a register bar, wherein the register bar is adjustable into and out of its normally straight configuration by means of at least three adjusting screws, a first of which engage the register bar in the region of one of the ends thereof, a second of which engages the register bar in the region of its other end and a third of which engages the register bar in the region of the middle thereof, and wherein each of the adjusting screws is rotatable by remote control by its own individual control motor, which control motors are disposed in the first roll of the printing machine.

2. A printing machine according to claim 1, wherein the control motors are automatically controllable by regulating signals, by a colour register regulation means operable to compare image edges or special printing lines or adjusting marks on the sheets.

3. A printing machine according to claim 1 or claim 2, including an indicator means for indicating the actual setting adopted by each adjusting screw and, in automatic operation, for switching off the respective control motor when the desired actual setting is reached.

4. A printing machine according to any one of claims 1 to 3, wherein, for the purposes of compensating for play in the respective screwthreads, the adjusting screws are preloaded by compression springs and, between the adjusting screw shank and the register bar, and the thrust rolling bearings, by plate springs.

5. A printing machine according to any one of claims 1 to 4, wherein each adjusting screw is mounted substantially without play axially and radially, in rolling bearings in the register bar.

6. A printing machine according to any one of claims 1 to 4, wherein the register bar is supported relative to the first roll by respective compression springs in the vicinity of each adjusting screw.

7. A sheet printing machine substantially as hereinbefore described with reference to the accompanying drawings.