WO1998028144A1

WO1998028144A1 - Continuous inkjet printer

Info

Publication number: WO1998028144A1
Application number: PCT/GB1997/003483
Authority: WO
Inventors: Philip Peter Bailey; Danny Palmer
Original assignee: Domino Printing Sciences Plc
Priority date: 1996-12-23
Filing date: 1997-12-18
Publication date: 1998-07-02
Also published as: GB9626704D0

Abstract

In a multi-nozzle ink jet printer, a three-point contact arrangement (13) between a drop generator (2) mount (4) and a support (7) is provided in a plane perpendicular to the plane (3) of the droplet streams, whereby the position of the mount (4) relative to the support (7) in the plane perpendicular to the droplet streams is very accurately defined so that, in turn, the plane of the droplet streams is fixed accurately with respect to other components of the print head secured to the support (7) and, in particular, the row of charge electrodes (9') and the gutter.

Description

CONTINUOUS INKJET PRINTER

The present invention relates to continuous in jet (CIJ) printers and, more particularly, to a mechanism for accurately positioning components of the printhead of a CIJ printers of the multi-nozzle type.

Multi-nozzle continuous inkjet printers have been developed in order to provide high quality, high speed printing. A row of inkjet nozzles at very close spacings are provided and individual streams of ink issue from each of the nozzles continuously in use, being broken up into individual droplets automatically. The individual droplets are charged appropriately to cause them to be printed or else deflected into a gutter. Printers of this type are described, for example, in US-A-4613871 and US-A-4427986. The printers described in these specifications are of the type generally known as binary continuous multi-jet.

Multi-jet printers of this type have alignment and set-up requirements which are additional to those of single jet printers, it being necessary to ensure that the rows of nozzles or jets are accurately aligned with the gutter, that each stream of droplets is accurately aligned with a respective charge electrode and that the charge electrodes are uniformly spaced from the respective droplet streams, ie. that the plane of the droplet streams and the row of charge electrodes are parallel to one another. These issues are addressed in US-A-5477254.

Achieving accurate parallel alignment of the plane containing the individual droplets streams and the row of respective charge electrodes and the gutter are critical requirements in order to avoid (a) inappropriate charges being applied to droplets (b) mis-direction of ink outside the gutter. It is therefore necessary to fix the position of the droplet generator with certainty. Since the droplet generator may need to be removed for servicing this presents a problem which has to be addressed. The present invention aims to achieve a simple, but effective means of maintain parallelism between the plane of the droplet streams and the row of charge electrodes, but allows adjustment of the position of the drop generator as required by accurately locating the drop generator in a fixed position in the direction perpendicular to the plane of the droplet streams.

According to the present invention there is provided a multi-nozzle drop generator providing, in use, a plurality of droplet streams disposed in a plane; a drop generator support; a mount securing the drop generator to the support; and, a three-point contact arrangement between the mount and the support, the three point contacts being disposed in a plane perpendicular to the plane of the droplet streams.

By providing a three-point contact arrangement between the mount and the support in a plane perpendicular to the plane of the droplet streams the position of the mount relative to the support in the plane perpendicular to the droplet streams is very accurately defined so that, in turn, the plane of the droplet streams is fixed accurately with respect to other components of the printhead and, in particular, the row of charge electrodes and the gutter.

One example of a printhead constructed in accordance with the present invention will now be described with reference to the accompanying drawings in which:

Figure 1 is a side elevational view of part of the printhead; and

Figure 2 is a plane view of the same part of the printhead.

The printhead 1 has a drop generator 2 (shown in outline) from which, in use, issue plural parallel streams of ink 3 which break up into droplets (in the figures the plane of the streams of droplets is perpendicular to the plane of the paper) . The droplet generator 2 is mounted in a mount comprised by a flexure 4 which is preferably of the type described in our British Patent application 9626683.8 and our co-pending PCT ^' Patent Application reference MJB05545 O. The drop generator 2 is secured in fixed position on the flexure 4 so that it is adjustable (as described in our co-pending application) in the direction normal to the plane of the paper in Figure 1, but is fixed in position transverse to the plane of the droplet streams 3. The flexure 4 has a generally trapezium-shaped flange 5 which engages a corresponding recess 6 in a support 7. The support 7 also mounts, in a pivoting fashion, a mounting plate 8 which carries a charge electrode support 9 and a deflection electrode 10, the spacing of the charge electrodes and deflection electrode 10 being adjusted by means of a screw 11 located in a screw-threaded bore 12 in the mounting plate 8 , the end of the screw abutting against the side of the drop generator 2 as shown in Figure 1. The gutter is not shown, but may be similarly movable.

The drop generator 2 may need to be removed for servicing, replacement or cleaning during the printers working life, but it is important that, on replacement, it is again accurately positioned in the same relationship to the charge electrodes and deflection electrode 10. In order to achieve this, the recess 6 in the support 7 has three raised protrusions providing contacts 13 on its side faces 19,20, a pair of protrusions 13 on the side face 19 and a single protrusion 13 on the side face 20, so that the side faces 14,15 of the flange 5, which face the side faces 19,20 respectively, are positionable only in one, accurately defined, position relative to the support 7. A screw 16 located in a bore 17 in the top flange 5 and engaging a corresponding screw-threaded bore 18 in the support 7 secures the flange 5 in position within the recess 6. A support abutment 19 disposed underneath the support 7 fixes the position of and supports the flange 5 in the up and down direction as seen in Figure 1. By this means, very accurate positioning of the drop generator is assured even after it has been removed for servicing etc. and replaced.

Claims

1. A multi-jet CIJ printer comprising a multi-nozzle drop generator providing, in use, a plurality of droplet streams disposed in a plane; a drop generator support; a mount securing the drop generator to the support; and, a three-point contact arrangement between the mount and the support, the three point contacts being disposed in a plane perpendicular to the plane of the droplet streams.

2. A printer according to claim 1, wherein the drop generator support has a recess, the recess having a pair of side faces disposed at an angle to one another, and wherein the mount has a flange disposed within the recess and having a pair of side faces opposing respective side faces of the recess, the contacts comprising a first raised protrusion on a first side face of the recess abutting a first side face of the flange, and second and third raised protrusions on the second side face of the recess abutting the second side face of the flange.

3. A printer according to claim 2 , wherein the mount is secured to the support by a screw-threaded fastening extending through the flange of the mount substantially centrally between the side faces thereof and engaged with the support substantially centrally between the side faces thereof.

4. A printer according to any of claims 1 to 3 , wherein the support includes an abutment disposed to face in a direction transverse to the plane of the three contacts to support the mount in a second plane transverse to the plane of the three contacts.