GB1562878A

GB1562878A - Ink-jet printers

Info

Publication number: GB1562878A
Application number: GB1724478A
Authority: GB
Original assignee: ITT Creed Ltd
Current assignee: ITT Creed Ltd
Priority date: 1978-05-02
Filing date: 1978-05-02
Publication date: 1980-03-19
Also published as: DE2916881A1

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 inkiet printers.

There are, broadly, two kinds of ink-jet printers: those in which a stream of ink drops is continuously ejaculated from a nozzle and is selectively deflected so that desired drops land on a record web while the remainder pass to a drain, which usually returns them to the ink reservoir; and those in which drops of ink are only ejaculated from the nozzle on demand in order to mark a record web. The later kind may be divided into two sub-kinds: those in which the ink is static in the nozzle until an ejaculating impulse is applied to either the fluid or the nozzle; and those in which ink flows in a continuous stream within a body of which the nozzle is a part and a drop is driven from the stream and out of the nozzle in response to an ejaculatory impulse.

In either of the two sub-kinds just described, if there is no call for printing for extended periods of time, ink tends to dry in the nozzle and gradually clog it. Slow to-dry inks can be obtained which contain a considerable amount of humectant, such as glycerine, but these inks are not conducive to high-quality printing since the ink tends to spread on the record web before it dries. Preferably, therefore, an ink which dries fairly quickly is desirable, and some means of keeping the nozzle free of ink during idle periods is needed.

According to the present invention, there is provided an ink-jet printer comprising: a print head having a channel therethrough and a nozzle through which, in use, inkdrops, diverted from a current of ink in the channel, may be ejaculated; an ink reservoir; and two pumps connected each in a pipe connection between print head and reservoir; whereby in a first mode of operation ink is fed by the pumps from the reservoir, through one pump, through the print head, through the other pump and delivered back to the reservoir, and in a second mode of operation, ink is drawn away from the print head by both pumps.

Embodiments of the invention are described below with reference to the accompanying drawings, of which: Figure 1 shows the basic idea of the invention; Figure 2 shows a practical realisation of that basic idea; and Figure 3 shows a crossover connector which may be used in the apparatus of Figure 2.

Referring to Figure 1, an ink-jet printer contains, inter alia, a print head 1 comprising a nozzle 1A which is part of a body 1B.

A pipe 2A connects a first port in the body to a first fluid pump 3A, upstream, and a pipe 2B connects a second port in the body to a second fluid pump 3B, downstream.

Pipes 2C and 2D connect pumps 3A and 3B respectively to an ink reservoir 4. In use, during printing, pump 3A draws ink from the reservoir 4 through pipe 2C and drives it through pipe 2A into print head 1 where it flows through a channel 1C, shown as a dotted line, past nozzle 1A, and out into pipe 2B. Pump 3B draws it through pipe 2B and drives it through pipe 2D to the reservoir. Suitable means, not shown, in the print head can divert drops of ink on demand from the ink in channel 1C into the nozzle, whence it is ejaculated onto a record web.

When any prolonged pause occurs in the printing process the sens of the upstream pump 3A can be reversed so that both pumps draw ink away from the print head 1. Air then enters through nozzle 1A and both the nozzle and the channel 1C are effectively cleared of ink so that clogging is prevented.

The two pumps should deliver fluid at the same rate and a practical pump arrangement is shown in Figure 2 where the two pumps are screw-pumps in a common pump chamber and driven on a common shaft from a common motor. With this arrangement one pump cannot be physically reversed with respect to the other and so a changeover connector must be connected to the inlet and outlet of the upstream pump. This changeover connector is indicated as 2X. In the position shown, ink is caused to flow through the print head, passing through pipes 2L and 2M of the changeover connection. If pipe 2L is disconnected from pipes 2C' and 2C", and pipe 2M is disconnected from pipes 2A' and 2A", while pipe 2K is connected to pipes 2A' and 2C", and pipe 2N is connected to pipes 2C' and 2A", then ink is drawn away from the print head by both pumps as described with reference to Figure 1.

The changeover arrangement of Figure 2 may be replaced by that shown in Figure 3. Pumps, pipes, print head and reservoir are shown very schematically, but correspond to the parts shown in Figure 2. The changeover connector 5 comprises a body 5A with a bore in which a spool 5B is rotatable. Body 5A has eight ports 5K, 5L, 5M, 5N, 5W, 5X, 5Y and 5Z.Spool 5B which fits in body SA in a sealing manner has four bores 5P, 5Q, 5R and 5S so arranged that in one position of rotation of the spool bore 5P connects ports 5K and 5W, and bore 5S connects ports 5N and 5Z, while in a second position of rotation of the spool, bore 5Q connects ports 5L and 5X, and bore 5R connects ports 5M and 5Y.As shown, bores 5P and 5S are parallel to each other and are perpendicular to bores 5Q and 5R while all the ports have their axes in a common plane, so that a quarter-turn of the spool is necessary to change the connections. As shown the ports are connected to the pipes 2A', 2A", 2C', 2C" by external branch pipes 2K' and 2M', 2M" and 2N", 2L' and 2N', 2K" and 2L" respectively. Alternatively the branch pipes could be channels within an extended body 5A', shown in dashed lines, with only four ports for external connection.

WHAT WE CLAIM IS:- 1. An ink-jet printer comprising: a print head having a channel therethrough and a nozzle through which, in use, inkdrops, diverted from a current of ink in the channel, may be ejaculated; an ink reservoir; and two pumps connected each in a pipe connection between print head and reservoir; whereby in a first mode of operation ink is fed by the pumps from the reservoir, through one pump, through the print head, through the other pump and delivered back to the reservoir, and in a second mode of operation, ink is drawn away from the print head by both pumps.

2. A printer as claimed in Claim 1, wherein one pump draws ink away from the head in both modes, and the other pump, by virtue of reversible connections, in the first mode delivers ink to the print head and in the second mode draws ink away from the print head.

3. A printer as claimed in Claim 4, wherein the reversible connections comprise a connector having a body with four pairs of co-operating ports or channels therein, and a rotatable spool contained in a bore in the body and having four bores in it, whereby, in a first rotary position of the spool, a first pair and a second pair of ports or channels are respectively connected by a first and a second bore in the spool, and in a second rotary position, a third pair and a fourth pair of ports or channels are respectively connected by a third and a fourth bore in the spool.

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

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. effectively cleared of ink so that clogging is prevented. The two pumps should deliver fluid at the same rate and a practical pump arrangement is shown in Figure 2 where the two pumps are screw-pumps in a common pump chamber and driven on a common shaft from a common motor. With this arrangement one pump cannot be physically reversed with respect to the other and so a changeover connector must be connected to the inlet and outlet of the upstream pump. This changeover connector is indicated as 2X. In the position shown, ink is caused to flow through the print head, passing through pipes 2L and 2M of the changeover connection. If pipe 2L is disconnected from pipes 2C' and 2C", and pipe 2M is disconnected from pipes 2A' and 2A", while pipe 2K is connected to pipes 2A' and 2C", and pipe 2N is connected to pipes 2C' and 2A", then ink is drawn away from the print head by both pumps as described with reference to Figure 1. The changeover arrangement of Figure 2 may be replaced by that shown in Figure 3. Pumps, pipes, print head and reservoir are shown very schematically, but correspond to the parts shown in Figure 2. The changeover connector 5 comprises a body 5A with a bore in which a spool 5B is rotatable. Body 5A has eight ports 5K, 5L, 5M, 5N, 5W, 5X, 5Y and 5Z.Spool 5B which fits in body SA in a sealing manner has four bores 5P, 5Q, 5R and 5S so arranged that in one position of rotation of the spool bore 5P connects ports 5K and 5W, and bore 5S connects ports 5N and 5Z, while in a second position of rotation of the spool, bore 5Q connects ports 5L and 5X, and bore 5R connects ports 5M and 5Y.As shown, bores 5P and 5S are parallel to each other and are perpendicular to bores 5Q and 5R while all the ports have their axes in a common plane, so that a quarter-turn of the spool is necessary to change the connections. As shown the ports are connected to the pipes 2A', 2A", 2C', 2C" by external branch pipes 2K' and 2M', 2M" and 2N", 2L' and 2N', 2K" and 2L" respectively. Alternatively the branch pipes could be channels within an extended body 5A', shown in dashed lines, with only four ports for external connection. WHAT WE CLAIM IS:-

1. An ink-jet printer comprising: a print head having a channel therethrough and a nozzle through which, in use, inkdrops, diverted from a current of ink in the channel, may be ejaculated; an ink reservoir; and two pumps connected each in a pipe connection between print head and reservoir; whereby in a first mode of operation ink is fed by the pumps from the reservoir, through one pump, through the print head, through the other pump and delivered back to the reservoir, and in a second mode of operation, ink is drawn away from the print head by both pumps.