GB2266270A

GB2266270A - Ductor roller drive for a printing press.

Info

Publication number: GB2266270A
Application number: GB9307873A
Authority: GB
Inventors: Josef Haase
Original assignee: Heidelberger Druckmaschinen AG
Current assignee: Heidelberger Druckmaschinen AG
Priority date: 1992-04-24
Filing date: 1993-04-16
Publication date: 1993-10-27
Anticipated expiration: 2013-04-16
Also published as: DE4213471A1; GB9307873D0; GB2266270B; JPH0623962A

Abstract

The invention relates to a ductor roller (1) drive for a printing press, wherein a ductor roller which is mounted on at least one crank (5) is pivotable forth and back between a slowly rotating fountain (3) roller and a relatively faster rotating distributor roller (4) in accordance with the work cycle of the machine. Differential gearing is provided for cyclic adjustment of the circumferential speed of the ductor roller to the different circumferential speeds of the fountain roller and the distributor roller. The ductor roller may be driven from an electric motor via a harmonic drive gear or cam gears (Figs 4, 5 not shown). <IMAGE>

Description

1.522 6 6. 9, c 7 0 DUCTOR ROLLER DRIVE FOR A PRINTING PRESS The invention

relates to a ductor roller drive for a printing press wherein a ductor roller which is mounted on at least one crank is pivotable back and forth between a slowly rotating fountain roller and a relatively faster rotating distributor roller in accordance with the work cycle of the machine, and wherein there is provided a gearing for cyclic adjustment of the circumferential speed of the ductor roller to the different circumferential speeds of the fountain roller and the distributor roller.

In inking units of printing presses, particularly in sheet-fed rotary offset printing presses.. it is common that ductor rollers are mounted on pivot levers, mostly in a freely rotatable manner, and pivotable between a fountain roller rotating at a lower speed and a first ink distributor roller or the like of the inking unit rotating at a considerably higher speed relative to said fountain roller. The ink received by the ductor roller from the fountain roller is transferred to the distributor roller in a manner that the ductor roller, through its contact with the fountain roller and the distributor roller, is driven by friction; thus, in the machine cycle the ductor roller is abruptly accelerated while being in contact with the distributor roller and is abruptly decelerated while being in contact with the fountain roller.

The German Patent DE 26 10 126 discloses a periodically alternating coupling of the ductor roller with the distributor roller and the fountain roller in accordance with the machine cycle through two gear trains and two magnetic couplings, so that the ductor roller, while being in contact with the distributor roller or with the fountain roller, is always driven at the same rotational speed. It is to be achieved that the contacts between the rollers take place at the same circumferential speed, thereby avoiding an irregular flow pattern of the transferred ink due to uneven thickness of the ink film, said irregular flow pattern being referred to hereinafter as scraping edges.

With the arrangement disclosed in U.S. Patent No. 3,688,696 this objective is to be reached by means of a belt drive which connects the ductor roller to a controllable motor. At the high printing speeds of modern printing presses there cannot be achieved a reliable result with this configuration.

For the cyclic acceleration and deceleration of the circumferential speed of the ductor roller, the German Patent No. DE 29 44 823 makes known the coupling of the ductor roller with a spring load through a planetary gear whereby the ductor roller is accelerated while being pivoted to the distributor roller and is decelerated while being pivoted to the fountain roller. The German Patent Application No. DE-OS 30 02 592 discloses that for the prevention of scraping edges in ink transfer the same effect can be achieved by the cyclic coupling of the ductor roller with a rotary stabilizer through variable gearing. In both cases considerable effort and expenditure are made for the prevention of scraping edges in ink transfer.

The present invention, however, has a different approach. Increased printing speeds also have lead to increased noise. Tests have shown that noise in inking units of printing presses of the type as described hereinabove, having a slowly rotating fountain roller and a considerably faster rotating distributor roller, is essentially the result of the socalled ductor-induced shock caused by high angular acceleration acting on the ductor roller as it comes in contact with the distributor roller, whereby the ductor roller is abruptly accelerated from an almost latent state to machine speed.

Accordingly, it is the object of the invention to provide a ductor roller drive, which accelerates the circumferential speed of the ductor roller on its pivot path to the 3 distributor roller to the circumferential speed of the distributor roller.

According to the present invention, the ductor roller has a drive which is actuable in accordance with the work cycle of the machine at the start of the pivoting movement of said ductor roller, and wherein said ductor roller is coupled with said drive through a differential gearing which accelerates said ductor roller to the circumferential speed of said distributor roller.

It is an essential advantage, as compared to the known configurations, that the ductor roller is accelerated already on its pivot path from the fountain rol-ler to the distributor roller to the circumferential speed of the distributor roller through a separate motoric drive. Both, the ductor roller and the distributor roller then roll off against each other at approximately the same circumferential speed, so that an acceleration of the ductor roller to an extent that it would cause a ductor shock does not take place any more. The ductor roller is permanently coupled with the drive motor via the differential gearing, and after the ductor roller has pivoted away from the distributor roller in the direction of the fountain roller a deceleration of the circumferential speed of the ductor roller takes place through internal friction of the differential gearing and the drive motor, so that the ductor roller, on its approach to the fountain roller, is practically decelerated again to the circumferential speed of the fountain roller. However, this should not exclude that actuation of this drive can also be provided through a decelerating differential gearing.

A preferred embodiment of the invention provides an electric-motor drive for the ductor roller. the electric-motor drive being actuated in accordance with the work cycle of the machine and being coupled with the ductor roller through a differential gearing with a varying gear ratio during one revolution. Differential gearing of the type known in the printing machine industry as harmonic drive gear, being of compact, spacesaving design, is primarily suitable, but other types of differential gearing of the state of the art, for example cam gears, chain gears etc. can also be used. The use of a harmonic drive gear has the added advantage that it is adjustable, if necessary, so that the acceleration of the ductor roller on its pivot path to the distributor roller can be optimally regulated.

The present invention is now described by way of example with reference to the accompanying drawings, in which:- FIGURE 1 is a cross-section of the inking unit of a printing unit having a pivotally arranged ductor roller; FIGURE 2 is an enlarged side-elevational view of Figure 1, showing the fountain roller, the ductor roller and the distributor roller; FIGURE 3 is a plan view of the drive side of the ductor roller, the inking roller and the distributor roller; FIGURE 4 is a schematic view of a suitable differential gearing; and FIGURE 5 is an illustration of a differential cam gear in various states of operation.

The ductor roller 1 of the inking unit of a printing press 2 is pivotally mounted between the fountain roller 3 and a first distributor roller 4 of the inking unit. The shaft of the ductor roller 1, with both its ends, is rotatably mounted on a crank 5 having a fixed bearing 6 on one end thereof, so that the ductor roller 1 is pivotable about the axis of this bearing between an engagement with the inking roller 3 and the distributor roller 4.

The drive of the ductor roller 1 consists of a periodically actuatable electric motor 7, the shaft of the electric motor 7 being coupled with the shaft 9 of the ductor roller 1 through a differential gearing 8. The periodically actuated electric motor 7 acts on the shaft 9 of the ductor roller 1 through the differential gearing 8 and accelerates the ductor roller 1 on its pivot path from the inking roller 3 to the distributor roller 4. Conventional differential gearing enables a regulation of the acceleration in such a way that the ductor roller 1, on its approach tothe distributor roller 4, has about reached the circumferential speed of the distributor roller 4, so that no ductor shock is caused. During the cyclic pivoting of the ductor roller 1 back to the fountain roller 3 the drive motor 7 is switched off. Then, a freewheel provided between the differential gearing 8 and the shaft 9 of the ductor roller 1 can become active.. and at the same time there can take place a deceleration of the ductor roller 1 through friction forces, if necessary, so that the adjustment of the circumferential speed of the ductor roller to the circumferential speed of the fountain roller can be achieved. If need be, this deceleration of the ductor roller on its pivot path to the fountain roller can also be achieved through the same drive; however, this is to be considered as an optional measure which normally is not required. In the exemplary embodiment of the differential gearing illustrated in Fig. 4 the electric motor 7 drives the entry-part 11 of a harmonic drive gear 12 via a bevel gear 10, and the exit part 13 of the harmonic drive gear 12 drives a gear 14.. for example, via a freewheel, said gear 14 being coupleable with the shaft 9 of the ductor roller 1. The gear ratio between the entry part 11 and the exit part 13 of the harmonic drive gear 12 is determined by a main shaft mounted generator 16 which connects the entry and exit parts 11, 13 with each other, and which is adjustable from the outside by a shaft 15. Such harmonic drive gears are coventional and not subject to the invention.

6 - Fig. 5 is a schematic illustration of a differential cam gear in various positions which is also suitable for the intended acceleration of the ductor roller 1. A disk 17 being drivable by the drive motor 7 carries a driving pin 18 which is suited to engage in a notch 19 of a second disk 20 being coupleable with the shaft 9 of the ductor roller 1 through a freewheel or the like. Both disks 17 and 20 are provided with toothing in a segment thereof; however, the toothing of the disks 17 and 20 engages in each other only when the driving pin 18 of the one disk has left the notch 19 of the other disk. While the driving pin 18 passes through the notch 19, an acceleration or deceleration of the disk which is provided with the notch takes place. When the segmental toothing of both disks 17 and 20 is in engagement, a transmission of torque takes place at a fixed gear ratio. Such differential cam gears according to Fig. 5 can be designed for angular acceleration as well as for angular deceleration. Cam gears of this type belong to the state of the art and are not subject to the invention.

It will of course be understood that the present invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention.

7

Claims

CLAIMS:

1. Ductor roller drive for a printing press, wherein a ductor roller which is mounted on at least one crank is pivotable back and forth between a slowly rotating fountain roller and a relatively faster rotating distributor roller in accordance with the work cycle of the machine, and wherein there is provided a gearing for cyclic adjustment of the circumferential speed of the ductor roller to the different circumferential speeds of the fountain roller and the distributor roller, wherein the ductor roller has a drive which is actuable in accordance with the work cycle of the machine at the start of the pivoting movement of said ductor roller, and wherein said ductor roller is coupled with said drive through a differential gearing which accelerates said ductor roller to the circumferential speed of said distributor roller.

2. Ductor roller drive according to claim 1 in which the ductor roller has an electric-motor drive which is electrically actuable in accordance with the work cycle of the machine and coupled with the ductor roller through a differential gearing with a varying gear ratio during one revolution.

3. Ductor roller drive according to claim 1 or 2 in which the ductor roller has a drive consisting of a motor and a differential cam gear and acting periodically according to the work cycle of the machine.

4. Ductor roller drive according to any one of the preceding claims in which the differential gearing is a harmonic-drive gear, with a continuously variable gear ratio.

5. Ductor roller drive substantially as hereinbefore described with reference to the accompanying drawings.

Amendments to the claims have been filed as follows 1. Ductor roller drive for a printing press, wherein a ductor roller which is mounted on at least one crank is pivotable back and forth between a slowly rotating fountain roller and a relatively faster rotating distributor roller in accordance with the work cycle of the machine, and wherein there is provided a gearing for cyclic adjustment of the circumferential speed of the ductor roller to the different circumferential speeds of the fountain roller and the distributor roller, wherein the ductor roller has an electromotive drive which is actuable, in accordance with the work cycle of the machine at the start of the pivoting movement of said ductor roller, and wherein said electromotive drive is coupled with said ductor roller through a differential gearing which accelerates said ductor roller to the circumferential speed of said distributor roller.

2. Ductor roller drive according to claim 1 in which the ductor roller has an electrically activatable drive motor an an adjustable differential gearing with a continuously variable transmission ratio.

3. Ductor roller drive according to claim 2 wherein the gearing comprises a hormonic drive gear.

4. Ductor roller drive according to claim 1 in which the ductor roller has a periodically active drive consisting of a motor and a differential cam gear.