GB1598779A - Ink-jet printers - Google Patents

Description

(54) INK-JET PRINTERS (71) We, ITT CREED LIMITED, a British Company of Crowhurst Road, Hollingbury, Brighton 6, Sussex, England, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to ink-jet printers and represents an improvement in or modification of the invention described and claimed in the complete specification of our co-pending application no. 8546/77 (Serial No. 1521874).

In said specification there is claimed an ink-jet printer comprising: a print-head consisting of a droplet generator, a droplet deflector, a droplet catcher and a record medium, the droplet deflector being a controlled pneumaticjet capable of acting on the stream of droplets which issues from the droplet generator so as to determine whether the stream will mark the record medium or enter the droplet catcher; an ink source interconnected to the print-head to deliver ink to the droplet generator; a supply of air under pressure to actuate the droplet generator and the droplet deflector; sensor elements to monitor the passage and position of the stream of droplets; and a central control unit to coordinate the control of the deflector with the passage and position of the droplet stream and with selective input signals relating to characters or pictures to be marked on the record medium.

In the specific embodiment described in said specification, the controlled pneumatic jet is produced from an external supply of air under pressure.

For some applications, it is convenient to dispense with the external air supply and produce the jet from a self-contained air chamber of which one wall is constituted by a diaphragm under the control of the input signals.

According to the present invention there is provided an ink-jet printer comprising an ink-droplet ejaculating head, a pneumatic impulse generator and a nozzle connected to the generator and positioned to direct puffs of air cross the trajectory of ink droplets ejaculated by the head, where the impulse generator comprises a chamber sealed except for its connection to the nozzle and having one of its walls formed by an electricallyoperable diaphragm, whereby the selective application of electrical impulses to the diaphragm causes corresponding puffs of air to issue from the nozzle and deflect any droplet passing the nozzle at that instant.

Embodiments of the invention are described below with reference to the accompanying drawings, of which: Figure 1 shows a basic arrangement of an ink-drop deflecting system; Figure 2 shows a compact arrangement of the system shown basically in figure 1, and Figure 3 shows a bi-axial ink-drop deflecting system.

In figure 1 there is shown an ink-dropletejaculating head, 1, such as described, for instance, in our application 8,547/77 (Serial No. 1527.444). Ink droplets produced by this head will, if undisturbed, travel in an idle trajectory until they strike a record web, 2.

To cause the droplets to land at points other than the end of the idle trajectory they must be deflected. One way of doing this is by selectively applying puffs of air to the stream of droplets in this trajectory. To this end, a nozzle 3 is located near to one point in the idle trajectory so as to blow across the stream perpendicularly and is connected to a pneumatic impulse generator 4 by a pipe 5.

The impulse generator 4 comprises a chamber sealed except for the outlet to the pipe and having one wall formed by a piezoelectric diaphragm 6 i.e. a diaphragm associated with a piezoelectric device. Each time an electrical impulse is given to the diaphragm it flexes and drives air from the chamber along the pipe 4 and out of the nozzle 3 to deflect any droplet passing at that instant. The size of the electrical impulse can control the force in the expelled air so that the one nozzle can be used to deflect droplets to more than one other trajectory. With a ratio between diaphragm area and nozzle area of at least 400, a diaphragm deflection of only 1 mil gives an appreciable droplet deflection.

In figure 2, the generator, pipe, and nozzle have all become part of the print head and are respectively indicated as 4', 5' and 3'.

Taking the record web 2 to be in a vertical plane the head is then capable of drawing vertical lines over a limited range on the paper. If it is also movable across the plane of the paper in a horizontal direction, characters can be drawn mosaic-fashion, using a nxm matrix. With such a head it has been found possible to form characters at a rate of 50 characters per second, using a 9-row-by-7column matrix and producing droplets at 5000 per second.

In figure 3 a further extension of the basic arrangement has two nozzles arranged perpendicularly to each other. Thus a droplet can be given not only a vertical deflection but also a horizontal deflection and the head may be held stationary during the formation of a character. Using the same size matrix and rate of droplet production as before, the rate of character formation can then be doubled to 100 characters per second.

It is to be understood that the diaphragm 6 need not be influenced by piezoelectric means. Other forms of electrical control, for example electro-magnetic, can equally be adopted.

WHAT WE CLAIM IS: 1. An ink-jet printer comprising an inkdroplet ejaculating head, a pneumatic impulse generator and a nozzle connected to the generator and positioned to direct puffs of air across the trajectory of ink droplets ejaculated by the head, wherein the impulse generator comprises a chamber sealed except for its connection to the nozzle and having one of its walls formed by an electricallyoperable diaphragm, whereby the selective application of electrical impulses to the diaphragm causes corresponding puffs of air to issue from the nozzle and deflect any droplet passing the nozzle at that instant.

2. A printer as claimed in claim 1 in which the diaphragm is operable by piezoelectric means.

3. A printer as claimed in claim 1 or 2 in which the magnitude of the electrical impulse determines the amount of deflection of the droplet.

4. A printer as claimed in claim 1, 2 or 3 in which a second impulse generator similar to the first-mentioned generator is connected to a second nozzle also positioned to direct puffs of air across the trajectory of the droplets, and substantially perpendicular to those puffs issuing from the first nozzle.

5. An ink-jet printer substantially as described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. deflection. In figure 2, the generator, pipe, and nozzle have all become part of the print head and are respectively indicated as 4', 5' and 3'. Taking the record web 2 to be in a vertical plane the head is then capable of drawing vertical lines over a limited range on the paper. If it is also movable across the plane of the paper in a horizontal direction, characters can be drawn mosaic-fashion, using a nxm matrix. With such a head it has been found possible to form characters at a rate of 50 characters per second, using a 9-row-by-7column matrix and producing droplets at 5000 per second. In figure 3 a further extension of the basic arrangement has two nozzles arranged perpendicularly to each other. Thus a droplet can be given not only a vertical deflection but also a horizontal deflection and the head may be held stationary during the formation of a character. Using the same size matrix and rate of droplet production as before, the rate of character formation can then be doubled to 100 characters per second. It is to be understood that the diaphragm 6 need not be influenced by piezoelectric means. Other forms of electrical control, for example electro-magnetic, can equally be adopted. WHAT WE CLAIM IS:

1. An ink-jet printer comprising an inkdroplet ejaculating head, a pneumatic impulse generator and a nozzle connected to the generator and positioned to direct puffs of air across the trajectory of ink droplets ejaculated by the head, wherein the impulse generator comprises a chamber sealed except for its connection to the nozzle and having one of its walls formed by an electricallyoperable diaphragm, whereby the selective application of electrical impulses to the diaphragm causes corresponding puffs of air to issue from the nozzle and deflect any droplet passing the nozzle at that instant.

2. A printer as claimed in claim 1 in which the diaphragm is operable by piezoelectric means.

3. A printer as claimed in claim 1 or 2 in which the magnitude of the electrical impulse determines the amount of deflection of the droplet.

4. A printer as claimed in claim 1, 2 or 3 in which a second impulse generator similar to the first-mentioned generator is connected to a second nozzle also positioned to direct puffs of air across the trajectory of the droplets, and substantially perpendicular to those puffs issuing from the first nozzle.

5. An ink-jet printer substantially as described with reference to the accompanying drawings.