GB2261850A

GB2261850A - Device for the zonewise metering of ink on a roller in a printing machine

Info

Publication number: GB2261850A
Application number: GB9221739A
Authority: GB
Inventors: Walter Hofheinz
Original assignee: Heidelberger Druckmaschinen AG
Current assignee: Heidelberger Druckmaschinen AG
Priority date: 1991-10-17
Filing date: 1992-10-16
Publication date: 1993-06-02
Anticipated expiration: 2012-10-16
Also published as: GB2261850B; GB9221739D0; DE9112926U1

Abstract

The invention relates to a device for the zonewise metering of ink on a roller in a printing machine, comprising zone-wide motoring elements (2), featuring supporting areas (5) and metering areas (6), arranged in the axial direction of the roller. The supporting areas (5) are in constant contact with said roller and the motoring areas (6) are adjustable independently of each other to variable distances with respect to said roller. The motoring areas (6) are designed as piezoelectric adjusting elements. <IMAGE>

Description

Device for the zonewise metering of a fluid medium on a roller in a printing machine The innovation relates to a device for the zonewise metering of a fluid medium on a roller in a printing machine comprising zone-wide metering elements having bracing bracing and metering areas in axial direction of said roller, said bracing areas being in constant contact with said roller, and said metering elements being adjustable to variable spacings independently of each other with respect to said roller.

Such a device has already been known from the German Patent 26 48 098 C3. In particular, this patent specification deals with an ink fountain designed for offset or letterpress printing machines including an ink-metering device. Said ink-metering device consists of individual metering elements which may be adjusted to ink gap thicknesses differing zonally. According to a specimen embodiment the metering elements are designed as cylinders which may be turned in circumferential direction, the metering areas being disposed adjacent the bracing areas and being formed as eccentric tapped grooves.

According to another specimen embodiment the metering elements are designed as shiftable flat elements, one side of each of which - in its function as a bracing area - is in direct tangential contact withthe roller, which are tangentially shiftable with respect to said roller and the respective front area of which features a stripping edge followed by an oblique recess extending inwardly and representing a metering area. The metering elements and thus the gap thickness of the ink transferred onto the roller are either adjusted manually or they are controlled via a motor with a potentiometer feedback.

Although said ink-metering device ensures an exact adjustment of the ink-metering elements the adjusting device which is assigned to each ink-metering element and which consists of an eccentric cylinder, an adjusting spindle, a potentiometer and a geared motor, is very costly considering merely the number of parts needed. Moreover, assembling said parts is time-consuming, and the assembled construction itself requires a relative wide space.

It is the object of the present innovation to create a device for metering a fluid medium on a roller, a device whic is of simple design and guarantees an absolute reproducibility of the respective set spacing, in addition to a sensitive zonewise regulation.

This object is achieved in that the metering areas of the metering elements are designed as piezoelectric adjusting elements.

The use of piezoelectric adjusting elements as metering areas of the metering elements has the major advantage that complicted mechanical constructions can be totally dispensed with. By applying high voltage to the piezoelectric adjusting elements the desired distance between metering area and roller is reproducible in each ink zone. As to adjusting travels up to 1000 um said distance may be changed without causing any difficulties. The adjustment accuracy is very high. Furthermore, the piezoelectric elements are known for their quick reaction to voltage changes. Another advantage is the fact that said piezoelectric adjusting elements are virtually not subjected to wear and tear.

In general, it can be stated that the piezoelectric adjusting elements are very well suited to be used as adjusting elements in quick control systems, the positioning being effected with an almost infinite adjusting sensitivity.

In an advantageous development of the method according to the invention the piezoelectric adjusting elements are composed of a plurality of individual piezoelectric layers. In so doing, the working voltages may be kept relatively low.

The innovation is explained in greater detail with reference to the following figures.

Fig.lis a side view of a metering element, engaged at a roller, according to the method of the invention, and Fig. 2 is top view according to the reference letter A in Fig. 1.

Fig. 1 is a side view of a metering element 2 engaged at a fountain roller 1 according to the method of the invention. In a known manner an ink fountain 3 is assigned to said fountain roller 1. The ink 4 is filled into the wedge-shaped space between fountain roller 1 and ink fountain 3. Via a vibrator roller (not illustrated) a thin film of the ink 4 is tranferred from the fountain roller 1 to an inking unit (not illustrated).

The thickness of the ink film is determined by the distance between metering elements 2 and fountain roller 1.

The thickness of the ink layer 4, transferrred zonewise onto the fountain roller 1, is controlled according to the motif to be printed. The metering element 2 consists of a supporting area 5 and a metering area 6. Via a spring-like pressure-exerting element 7 the supporting areas 5 of the metering element 2 are in constant direct with the fountain roller 1 or, via a foil 8, in constant indirect contact therewith. Possible concentricity errors of the fountain roller 1 are compensated for by the spring-like pressure-exerting element 7, thus ensuring that the metering area 6 always features the set distance to the fountain roller 1.

The metering area 6 is designed as a piezoelectric adjusting element. The changes in dimension of the piezoelectric adjusting element depend on the high voltage applied to the high-voltage terminal. As the longitudinal expansion of the piezoelectric adjusting element depends on the voltage applied, a defined gap aperture and thus a defined film thickness of ink 4 can be transferred onto the fountain roller 1 via a change in the voltage. Both the mechanical adjustment of the metering elements and the feedback of the respective position via potentiometer can be dispensed with when using the device according to the invention.

The device according to the invention is, of course, not limited to the transfer of ink 4 onto the fountain roller 1. The device according to the invention may also be used for the application of dampening medium or varnish.

Fig. 2 is a top view of the device embodied in the invention according to the reference letter A in Fig. 1. The metering elements 2 are supported with their supporting areas 5 on the surface of the fountain roller 1. In individual ink zones 10 the ink 4 is applied onto the fountain roller 1 according to the motif to be printed.

According to the invention the metering areas 6 are formed by piezoelectric adjusting elements. Said piezoelectric adjusting elements consist of a plurality of layer of piezoelectric material. The expansion of the metering area 6 is controlled via a high voltage applied to the piezoelectric adjusting elements.

The control as such is effected according to a stored identification line reflecting the relation between applied voltage and change in length of the piezoelectric adjusting element. The metering elements 2a, 2b and 2c indicate the position of the metering areas 6 given different voltages.

Whereas the metering area 6 of the metering element 2a reaches up to the surface of the fountain roller 1 - in this case, no ink is transferred -, the metering areas 6 of the metering elements 2b and 2c feature a defined distance with respect to the fountain roller 1.

It will be appreciated that the invention has been described above by way of example only and that changes may be made without departing from the scope of the invention.

Claims

1. Device for the zonewise metering of a fluid medium on a roller in a printing machine comprising zone-wide metering elements featuring supporting areas and metering areas in axial direction of said roller, said supporting areas being in constant contact with said roller, and said metering areas of said metering elements being adjustable independently of each other to variable distances with respect to said roller, characterized in that said metering areas of said metering elements are designed as piezoelectric adjusting elements.

2. Device according to Claim 1, characterized in that the piezoelectric adjusting elements are composed of a plurality of individual piezoelectric layers.

3. Device for the zonewise metering of a fluid medium on a roller in a printing machine, substantially as hereinbefore described with reference to the accompanying drawings.