WO1998028152A1

WO1998028152A1 - Flexure for continuous inkjet printer

Info

Publication number: WO1998028152A1
Application number: PCT/GB1997/003481
Authority: WO
Inventors: Jerzy Marcin Zaba
Original assignee: Domino Printing Sciences Plc
Priority date: 1996-12-23
Filing date: 1997-12-18
Publication date: 1998-07-02
Also published as: GB9626683D0

Abstract

A flexure (1) of the type comprising a pair of end portions (2, 2') interconnected by integral thin flexible parallel beam portions (4), is provided for use in an inkjet printer. The flexure has portions (7, 9) projecting inwardly from each end portion and adjusters (12-15) operatively engaged with the projecting portions for adjusting the positions of the projecting portions (7, 9) relative to one another in a direction transverse to the direction of the flexible beam portions (4), so that the end portions (2, 2') can be adjusted in position relative to one another in parallel, in turn to adjust the position of the charge electrodes (20) and the droplet streams (22) into alignment with one another.

Description

FLEXURE FOR CONTINUOUS INKJET PRINTER

The present invention relates to continuous in jet (CIJ) printers and, more particularly, to flexures for adjusting the relative position of printhead components in 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 all 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 alignment between the individual droplets streams and their respective charge electrodes is a particularly critical requirement in order to avoid inappropriate charges being applied to droplets. The use of a flexure of the type in IBM Technical Disclosure Bulletin Volume 20, No. 1 of June 1977 and referred to therein as a cardo spring, has advantages in this regard. A flexure of this type has a pair of end portions interconnected by integral parallel flexible thin beam portions which allow for parallel motion of the end portions relative to one another. However, the construction occupies considerable space as it provides, effectively, a rectangular open space between the flexible beams. Space is always at a premium in CIJ multi-jet printers and the present invention is aimed at reducing this problem.

According to the present invention therefore a flexure of the type comprising a pair of end portions interconnected by integral thin flexible parallel beam portions has portions projecting inwardly from each end portion and an adjustment mechanism operatively engaged with the projecting portions and adapted to adjust the positions of the projecting portions relative to one another in a direction transverse to the direction of the flexible beam portions, whereby the end portions are likewise adjustable in position relative to one another in parallel.

Providing the adjustment mechanism internally of the flexure results in a considerable decrease in the space occupied by the flexure.

Preferably, the projection from one end portion comprises a yoke, the projection from the other end portion projecting into the yoke and a pair of adjusters are provided one on each side of the yoke and engaging the other projection.

The adjusters preferably comprise screws which are threaded in respective bores in one of the projections and which have end abutments engaging in corresponding sockets in the other projection. When such a flexure is used to mount the gun body or droplet generator of a multi-nozzle CIJ printer an extremely compact and relatively stress-free mounting can be achieved whilst allowing the required degree of adjustment of the position of the gun body or droplet generator parallel to the row of nozzles in order to achieve accurate alignment with the charge electrodes. The invention includes a multi-nozzle CIJ printhead incorporating a flexure of the type defined above.

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

Figure 1 is a first face view of the flexure in its "neutral" position;

Figure 2 is a view corresponding to that of Figure 1 but with the flexure shown in a flexed position; and Figure 3 is a partially sectioned side view of the flexure, shown mounted on a support.

The flexure 1 has end portions 2, 2¹ which are interconnected by integral thin flexible parallel beam portions 4 and is formed of stainless steel or a similar material. The lower end portion 2' is provided by separate halves 3, 3' connected by a bridging portion 5 which, in this example, provides a pair of mounting apertures 6 for mounting of a gun body or droplet generator 16 of a CIJ printer (see Figure 3) . Extending from the bridging portion 5 of the end portion 2 ' is a central protrusion 7 which is disposed between the ends 8 of a yoke-like protrusion 9 extending inwardly of the flexure from the upper (as seen in the Figures) end portion 2. The upper end portion 2 has a mounting aperture 10 and (on the side opposite that which is seen in Figures 1 & 2) a flange 11 which is also used for mounting the flexure to a supporting frame 17 as described in our British Patent application no. 9626704.2 and our co-pending International Patent application reference MJB05497WO. A pair of adjusting screws 12 are located in corresponding screw-threaded bores 13 in the end portions 8 of the yoke-like projection 9 and each of the screws 12 has an end 14 which engages in a corresponding socket 15 in the protrusion 7. The screws 12 thus control the relative positions of the projections 7, 9 and thus ^'of the end portions 2, 2¹ in the direction generally perpendicular to the parallel beam portions 4 and allow adjustment from the neutral position shown in Figure 1 to a flexed position shown in Figure 2 for example, by appropriate rotation of the screws in opposite directions. In Figure 2 the lower end portion 2' can be seen to be displaced leftwards, whilst maintaining parallelism with the upper end portion 2, the beam portions 4 enabling the flexure to take place in parallel fashion. Figure 3 illustrates the flexure from the side, partially sectioned, and shows a multi-nozzle droplet generator 16 mounted on the flexure 1 via the mounting apertures 6 (the mounting screws have been left out for clarity). Also shown is a mounting plate 18, supported hingedly on the support 17 , and carrying a charge electrode support 19 which, in turn carries a plurality of charge electrodes 20 (in a row normal to the plane of the paper in Figure 3) . The mounting plate 18 also carries a deflector electrode 21. In use plural streams 22 of droplets are produced from the nozzles in a plane (normal to the plane of the paper in Figure 3) for selective charging and deflection.

The flexure 1 enables the individual streams 22 to be accurately adjusted into alignment with their corresponding charge electrodes 20.

Claims

1. A flexure of the type comprising a pair of end portions interconnected by integral thin flexible parallel beam portions, the flexure having respective portions projecting inwardly from each end portion; and an adjustment mechanism operatively engaged with the projecting portions and adapted to adjust the positions of the projecting portions relative to one another in a direction transverse to the direction of the flexible beam portions, whereby the end portions are adjusted in position relative to one another in parallel.

2. A flexure according to claim 1, wherein the projection from one end portion comprises a yoke, the projection from the other end portion projects into the yoke, and the adjustment mechanism comprises a pair of adjusters, one on each side of the yoke and engaging the other projection.

3. A flexure according to claim 2, wherein the adjusters comprise screws which are threaded in respective bores in one of the projections and which have end abutments engaging in corresponding sockets in the other projection.

4. A multi-nozzle CIJ printhead incorporating a flexure according to any of claims 1 to 3.

5. A multi-nozzle CIJ printhead according to claim 4, comprising a droplet generator having a plurality of nozzles disposed in a row, and a corresponding plurality of charge electrodes, wherein the flexure mounts the droplet generator to provide the required degree of adjustment of the position of the droplet generator parallel to the row of nozzles in order to achieve accurate alignment of the charge electrodes with droplet streams issuing from the nozzles in use.

6. A CIJ printer having a printhead according to claim 4 or claim 5.