WO2009124346A1

WO2009124346A1 - A method and arrangement for stirring inks

Info

Publication number: WO2009124346A1
Application number: PCT/AU2009/000431
Authority: WO
Inventors: Steven Charles Richardson; Gordon James Zerf
Original assignee: Impression Technology Pty Limited
Priority date: 2008-04-08
Filing date: 2009-04-08
Publication date: 2009-10-15

Abstract

An ink stirring arrangement including a container (1.014), a stirrer (1.012), a motor (1.008), and a motor speed control arrangement (1.004), (1.016), wherein the speed control arrangement is adapted to maintain the speed of stirring below the speed at which turbulence occurs.

Description

A Method and Arrangement for Stirring Inks

Field of the invention

[001] This invention relates to a method and arrangement for stirring inks.

[002] The invention is particularly suited for stirring white ink. The invention is suitable for use with ink jet printers, and can be used to advantage in printing on garments.

Background of the invention

[003] White inks use a pigment, typically rutile (TiO₂) and a carrier, which may be, for example, a commercially available heat activated polymer.

[004] The TiO₂T tends to settle out of from the carrier, and thus must be stirred regularly. One problem is that excessive agitation at high speed can cause air bubbles to be entrained in the ink. This in turn can cause problems in printing, for example, by causing the print head to stop jetting and thus block.

[005] A known stirrer used a magnetic stirring arrangement having a speed selection control. This was also found to be subject to over agitation when users were not fully trained in the use of the device. Resulting problems included abrasion of the pill and bubble entrainment.

Summary of the invention

[006] We have found that limiting the speed of the stirring action can avoid entrainment of air in the ink. In particular limiting the speed of a stirrer to about 1 revolution per second or less can produce satisfactory results. We have found that, for a container a speed of 70 rpm for a paddle of 80 mm by 20 mm was satisfactory.

[007] The invention provides an ink stirring arrangement including a container, a stirrer, a motor, and a motor speed control arrangement, wherein the speed control arrangement is adapted to maintain the speed of stirring below the speed at which turbulence occurs. [008] The invention also provides an ink supply arrangement including an ink container, a circulating pump, an ink distributing manifold, one or more print heads, wherein the manifold is adapted to return unused ink to the container, and wherein the pump is a pulse-action pump.

[009] The invention further provides an ink distribution manifold including an inlet port, a return port, one or more outlet ports, and a back pressure adjuster adapted to influence the pressure at the or each outlet port. According to an embodiment of the invention, there is provided a method of stirring ink in which the stirring speed is maintained below the speed of entrainment of air.

[010] The invention also provides apparatus for controlling the speed of a stirrer to below the speed of entrainment of air.

[011] The apparatus includes a controllable voltage supply, a current limiting device, and a drive motor connected to drive a stirrer.

[012] The motor can be connected to the stirrer via a gearing arrangement.

[013] The invention also provides apparatus for controlling the stirring of ink during active and sleep phases of operation.

[014] The apparatus can include a controller adapted to control the application of power to the motor in accordance with one of two or more modes of operation.

[015] The apparatus can include detector to detect j amming of the rotor.

[016] The invention also provides an ink delivery system including an ink stirring apparatus, a peristaltic pump, connected to deliver ink to a print head from the ink container, and to return unused ink to the container.

[017] The system can also include a manifold for distributing the ink to two or more print heads.

[018] The units of the system can be interconnected by flexible tubing.

[019] The system can operate in two or more modes.

[020] A first mode can be an active mode. [021] The invention also provides a method of stirring ink to reduce entrainment of air, the method including the step of stirring the ink at a speed below the speed at which turbulence colours.

[022] The invention also provides a method of maintaining ink during quiescent periods, the method including the step of using circulating the ink through an ink delivery system using a pulsating pumping action.

Brief description of the drawings

[023] An embodiment or embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[024] Figure 1 is a block schematic diagram of apparatus according to an embodiment of the invention;

[025] Figure 2 is a schematic illustration of a system according to an embodiment of the invention;

[026] Figure 3 is a perspective illustration of a manifold according to an embodiment of the invention.

[027] The numbering convention used in the drawings is that the digits in front of the full stop indicate the drawing number, and the digits after the full stop are the element reference numbers. Where possible, the same element reference number is used in different drawings to indicate corresponding elements.

Detailed description of the embodiment or embodiments

[028] The invention will be described with reference to the drawings.

[029] Figure 1 shows a block schematic diagram of ink stirring apparatus according to an embodiment of the invention.

[030] A power supply, indicated schematically as battery 1.002 supplies DC power to a power controller 1.004. A current limiting resistor 1.006 is connected in series with DC motor 1.008. DC motor 1.008 drives gear chain 1.010, which, in turn drives paddle 1,012. The paddle stirs the ink in the container 1.014. Preferably, the stirring speed is selected to be below the speed at which turbulence occurs.

[031 ] In a container 1.002 of 90mm inside diameter and 100mm height, a paddle of the order of 80 mm width and 20 mm height spaced about 5mm above the bottom of the tank was found to produce good results when operated at 70 rpm.

[032] A function controller 1.016 is adapted to control the voltage/power controller output. The function controller 1.016 can be, for example, a programmable controller or microprocessor.

[033] The power controller 1.004 can be, for example, a controllable voltage regulator, or a duty cycle controlling switch which can vary the duty cycle of the output by varying the ration of ON and OFF periods. Where a duty cycle control is used, a filter 1.001 can be included to smooth the output from the voltage/power controller 1.004 before it is applied to the motor 1.008.

[034] The motor can be, for example a DC motor adapted to operate with an input supply of 4.5v to 18v.

[035] The function controller 1.016 can have one or more control modes. For example, the controller can be adapted to control the motor in a first mode when the ink is being used (active mode) and a second mode when the printer is inactive (sleep mode).

[036] The current limiting resistor can be, for example, an incandescent light globe having an impedance selected to limit the current to below the maximum current rating of the motor when the maximum voltage is applied. In one embodiment a 12OmW 12v globe was used.

[037] hi normal operation with a 12v supply, the voltage drop across the motor will be of the order of 11.5v and the drop across the lamp will be of the order of 0.5v, which is insufficient to illuminate the globe. However, if the motor stalls, the drop across the lamp will rise to about 1Ov, and the globe will be illuminated, providing a visual indication of the problem.

[038] In an alternative embodiment, an automatic protection device, such as a relay can be used to cut off the current. The relay can be connected in parallel with the limiting resistor and can include a zener diode to set the voltage at which current will flow in the relay.

[039] In one embodiment, the value of the impedance of the globe 1.006 can be chosen to control the operation of the motor to a desired speed for a given input voltage.

[040] In the embodiment shown in Figure 1, a function controller 1.016 and a voltage or power controller 1.004 are used to select operating modes, hi the active mode, during printing, the function controller 1.016 controls the voltage/power controller so that the motor 1.008 runs at a predetermined speed. Thus the function controller 1.016 causes the voltage/power controller 1.004 to deliver the required amount of power to the motor 1.008 to run at, for example 70 rpm.

[041] In a first sleep mode, the motor can be switched off. In an alternative, the operation the function controller 1.016 can implement a timer function so the motor can be operated intermittently.

[042] The lowest duty cycle and rotation speed can be selected to maintain the ink.

[043] Rubber shrouds can be applied to the motor to prevent the ink from entering the motor and gear train.

[044] Figure 2 schematically illustrates an ink supply system according to an embodiment of the invention.

[045] A paint container 2.020 is connected to a filter 2.022 which is connected to a circulating pump 2.024. The pump supplies the ink to a manifold 2.028 through ink delivery pipe 2.026. The manifold 2.028 delivers the ink to the selected print head 2.030, and unused ink is returned to the container via return pipe 2.032.

[046] The pump 2.024 is preferably a peristaltic pump which provides a pulsed pumping action. Preferably the pump operates at about 140 pulses per minute.

[047] The container 2.020 can include a stirrer arrangement as described in relation to Figure 1. [048] In a further sleep mode, the peristaltic pump 2.024 is operated continuously, and the stirrer is switched off.

[049] In a variation of this sleep mode, the operation of the stirrer can be intermittent.

[050] The pulsed pump action can also assist in inhibiting the adherence of the ink to the inner walls of the pipes. The pipes can be made from flexible tube such as silicone tube or tygon ™ tube.

[051] The manifold of Figure 3 has an inlet port 3.044 and a return port 3.045 connected by pipes 3.048, 3,050. An array of outlet ports such as 3.052, 3.054, 3.056, 3.058 are supplied from the inlet port. A back pressure adjusting arrangement illustrated by grub screw 3.060 is used to set the required back pressure to obtain the desired flow of ink to the print head outlets.

[052] Typically a print head has between 3 and 8 ranks of nozzles which would normally jet different coloured inks. Each rank has it's own ink supply line so the manifold splits or diverts the flow of ink coming into the inlet port down each of the four outlet ports and then out of the exhaust port. By restricting the exhaust port, pressure can be created in the outlet ports.

[053] In this specification, reference to a document, disclosure, or other publication or use is not an admission that the document, disclosure, publication or use forms part of the common general knowledge of the skilled worker in the field of this invention at the priority date of this specification, unless otherwise stated.

[054] In this specification, terms indicating orientation or direction, such as

"up", "down", "vertical", "horizontal", "left", "right" "upright", "transverse" etc. are not intended to be absolute terms unless the context requires or indicates otherwise.

[055] Where ever it is used, the word "comprising" is to be understood in its

"open" sense, that is, in the sense of "including", and thus not limited to its "closed" sense, that is the sense of "consisting only of. A corresponding meaning is to be attributed to the corresponding words "comprise", "comprised" and "comprises" where they appear. [056] It will be understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text. AU of these different combinations constitute various alternative aspects of the invention.

[057] While particular embodiments of this invention have been described, it will be evident to those skilled in the art that the present invention may be embodied in other specific forms without departing from the essential characteristics thereof. The present embodiments and examples are therefore to be considered in all respects as illustrative and not restrictive, and all modifications which would be obvious to those skilled in the art are therefore intended to be embraced therein.

Claims

1. An ink stirring arrangement including a container, a stirrer, a motor, and a motor speed control arrangement, wherein the speed control arrangement is adapted to maintain the speed of stirring below the speed at which turbulence occurs.

2. An ink supply arrangement including an ink container, a circulating pump, an ink distributing manifold, one or more print heads, wherein the manifold is adapted to return unused ink to the container, and wherein the pump is a pulse-action pump.

3. An ink distribution manifold including an inlet port, a return port, one or more outlet ports, and a back pressure adjuster adapted to influence the pressure at the or each outlet port.

4. A method of stirring ink to reduce entrainment of air, the method including the step of stirring the ink at a speed below the speed at which turbulence colours.

5. A method of maintaining ink during quiescent periods, the method including the step of using circulating the ink through an ink delivery system using a pulsating pumping action.