GB1559970A

GB1559970A - Ink-jet printers

Info

Publication number: GB1559970A
Application number: GB1978278A
Authority: GB
Original assignee: ITT Creed Ltd
Current assignee: ITT Creed Ltd
Priority date: 1978-05-16
Filing date: 1978-05-16
Publication date: 1980-01-30
Also published as: DE2916263A1

Description

(54) INK-JET PRINTERS (71) We, ITT CREED LIMITED, a British Company, of Crowhurst Road, Hollingbury, Brighten 6,Sussex, England, do herebv 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 inkjet printers.

According to the present invention there is provided an ink-jet printer comprising an ink-droplet ejaculating head connected between the output of a first pump and the intake of a second pump wherein the two pumps are screw pumps connected on a common shaft to a common driving motor, but with screws of opposite hand and with their intakes substantially adjacent, so that there is no need for a seal between the two pumps.

An embodiment of the invention and its relevance to the prior art is described below with reference to the accompanying drawings, of which: figure 1 shows a basic screw pump; figure 2 shows an ink-droplet producing head positioned between two pumps; figure 3 shows two screw pumps driven by one shaft but in a single pump housing, and figure 4 shows how the arrangement of figure 3 is modified according to the invention to avoid leakage problems between the two pump sections.

In figure 1 there is shown a fluid pump which comprises a screw I turning in a housing 2 and pumping a fluid from an intake pipe 3 to an output pipe 4. A motor 5 turns the screw For best results, a long fine screw with a comparatively large clearance between screw and housing is used. The pump is driven at high speed and thus the output from the pump is delivered with negligible pressure variation caused by either cogging (which would be apparent if the motor were to be run at low speed) or manufacturing variations (which would show up with a short screw or a close fit between screw and housing).

For a balanced condition of flow through the printhead 6 in figure 2 two practically identical pumps A and B are used, one on either side of the print-head. An ink supply 7 is the source for ink drawn in by pump A and is the sink for ink put out by pump B. The print-head is of the kind in which a stream of ink flows through it past a nozzle continuously and droplets are ejaculated through the nozzle on demand.

The pumps A and B are ideally driven at the same speed and by the same motor. Figure 3 shows two such pumps Al and B1 as in figure 1 arranged in tandem and driven on one shaft by the same motor. The output of pump A1 is adjacent to the intake of pump B and, because the print-head is connected between this output and this intake a seal 8 must be placed between the pumps lest the flow to the print-head be by-passed by leakage. Such a seal, however, causes a frictional drag which is undesirable.

Therefore, in the embodiment of the invention shown in figure 4, two screw pumps are arranged in the same housing and driven by the same motor but the two screws are of opposite hand and have their intakes adjacent. Thus delivery of ink from pump A1l to the print-head cannot be by-passed to the intake of pump B1l. If there were any leakage between the pumps it would be from the intake of pump lB"to the intake of pump A so that some ink which had already been through the print-head would go through it again without visiting the reservoir. This avoids the need for any seal between the pumps.

WHAT WE CLAIM IS 1. An ink-jet printer comprising an inkdroplet ejaculating head connected between the output of a first pump and the intake of a second pump wherein the two pumps are screw pumps connected on a common shaft to a common driving motor, but with screws of opposite hand and with their intakes substantially adjacent, so that there is no need for a seal between the two pumps.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. (54) INK-JET PRINTERS (71) We, ITT CREED LIMITED, a British Company, of Crowhurst Road, Hollingbury, Brighten 6,Sussex, England, do herebv 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 inkjet printers. According to the present invention there is provided an ink-jet printer comprising an ink-droplet ejaculating head connected between the output of a first pump and the intake of a second pump wherein the two pumps are screw pumps connected on a common shaft to a common driving motor, but with screws of opposite hand and with their intakes substantially adjacent, so that there is no need for a seal between the two pumps. An embodiment of the invention and its relevance to the prior art is described below with reference to the accompanying drawings, of which: figure 1 shows a basic screw pump; figure 2 shows an ink-droplet producing head positioned between two pumps; figure 3 shows two screw pumps driven by one shaft but in a single pump housing, and figure 4 shows how the arrangement of figure 3 is modified according to the invention to avoid leakage problems between the two pump sections. In figure 1 there is shown a fluid pump which comprises a screw I turning in a housing 2 and pumping a fluid from an intake pipe 3 to an output pipe 4. A motor 5 turns the screw For best results, a long fine screw with a comparatively large clearance between screw and housing is used. The pump is driven at high speed and thus the output from the pump is delivered with negligible pressure variation caused by either cogging (which would be apparent if the motor were to be run at low speed) or manufacturing variations (which would show up with a short screw or a close fit between screw and housing). For a balanced condition of flow through the printhead 6 in figure 2 two practically identical pumps A and B are used, one on either side of the print-head. An ink supply 7 is the source for ink drawn in by pump A and is the sink for ink put out by pump B. The print-head is of the kind in which a stream of ink flows through it past a nozzle continuously and droplets are ejaculated through the nozzle on demand. The pumps A and B are ideally driven at the same speed and by the same motor. Figure 3 shows two such pumps Al and B1 as in figure 1 arranged in tandem and driven on one shaft by the same motor. The output of pump A1 is adjacent to the intake of pump B and, because the print-head is connected between this output and this intake a seal 8 must be placed between the pumps lest the flow to the print-head be by-passed by leakage. Such a seal, however, causes a frictional drag which is undesirable. Therefore, in the embodiment of the invention shown in figure 4, two screw pumps are arranged in the same housing and driven by the same motor but the two screws are of opposite hand and have their intakes adjacent. Thus delivery of ink from pump A1l to the print-head cannot be by-passed to the intake of pump B1l. If there were any leakage between the pumps it would be from the intake of pump lB"to the intake of pump A so that some ink which had already been through the print-head would go through it again without visiting the reservoir. This avoids the need for any seal between the pumps. WHAT WE CLAIM IS

1. An ink-jet printer comprising an inkdroplet ejaculating head connected between the output of a first pump and the intake of a second pump wherein the two pumps are screw pumps connected on a common shaft to a common driving motor, but with screws of opposite hand and with their intakes substantially adjacent, so that there is no need for a seal between the two pumps.

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