DE19642899A1 - Inductive ink level detection device for ink supplies - Google Patents

Abstract

An ink level detection mechanism 14 comprises a flexible ink container 16, e.g. in the form of a collapsible bag contained within a cartridge (10, Fig. 1), for storing an ink supply used by an inkjet pen. The ink container has opposing sides which move relative to one another depending upon an amount of ink held therein and which carry a pair of electrically conductive coils 30, 32 formed on the opposing sides of the container. The coils 30, 32 move relative to one another in conjunction with the movement of the container sides, and an ink level sensing circuit 50 connected to the coils generates a signal which induces a magnetic field between the pair of coils. The circuit 50 senses the level of ink within the container 16 by detecting change in the field as the coils 30, 32 are moved relative to one another. The field strength increases as the coils 30, 32 are moved closer together, thereby improving the quality of the measurement as the ink is used from the container.

Description

This invention relates to ink level detection directions and in particular to an inductive ink level detecting device for detecting a residual ink amount in an ink tank of an ink-jet pen.

An inkjet printer is a type of non-impact Printer, which signs and other images by steuerba res spraying ink droplets from a printhead forms. A conventional type of ink jet printhead is from an exchangeable cassette or from an exchange Baren pin, which is removable on a movable carriage is attached. The pen raises liquid in a controllable way Ink ejected through a plurality of nozzles in the form of droplets, wel fly over a small air gap and onto a land on a recording medium.

Ink droplets are localized from individual nozzles th heating. A small heating element, which typically in the form of a thermal resistor is formed, is arranged at each nozzle. An electri Current flows through the element to heat it up. The heated element vaporizes a tiny volume of ink, wel It is ejected through the nozzle. The heating elements are generally formed on a single silicon wafer chip, where thanks to the replaceable pin when assembling easy and is favorable in the production.

An ink reservoir is held in a container, the egg NEN part of an independent cassette forms of the Pen is disconnected. The pen pulls ink from the container during printing. The container can be used as a fixed chamber or configured as a flexible bag. During the  When pen ink is used, the ink supply in the container becomes slowly emptied. Printers are often designed to adjust the level to detect residual ink in the container and the user informing when it is time to extend the pen replenish or refill. Depending on the structure is either the entire pen or ink tank of the Stif exchanged. The empty pen or container becomes thrown away or recycled.

There are essentially three different types known techniques for detecting the level of residual ink in Ink tanks: a capacitive sensing, a resistive Detection and magnetic detection. U.S. patent No. 4,415,886 describes a residual ink detection apparatus tion for detecting the amount of residual ink in a Tintenbe container using a capacitive detection. The Be Container is as a flexible bag with a top and egg formed on the lower sheet. A metal thin film layer is on both the upper and the lower plate assigns to a pair of spaced-apart condensa to form gate electrodes. A pulse generating circuit lays Pulses to the capacitor electrodes, wherein the elektrosta table capacitance between the electrodes is measured. If the ink tank is full, the capacity of the electric the small pair. As the ink is being emptied, it rises Capacity of the electrode pair. The disadvantage of this Type of capacitive sensing element is assigned, be is that it does not work very well when It is used with conductive inks. To be sufficient to achieve behavior with conductive ink supplies, If a signal with very high frequency (in the magnitude tion of several MHz) passed through the capacitor who the. Generating a high frequency signal is not possible ne desirable operating condition for an ink jet printer.

U.S. U.S. Patent No. 4,700,754 describes an ink level Detector for a collapsible ink container, wel  cher also uses a capacitive detection. Instead of the use of two electrodes ge on the pocket ge The device described in U.S. Pat. patent No. 4,700,754, the capacity between the liquid ink and an electrically conductive Beschich tion, which is formed on the ink tank. This kapazi tive detection technology has a disadvantage in that she works as a switch-type alarm detector who either off or on, depending on whether the Ink supply has been drained to a certain level is. The measured capacity is proportional to the area the ink that covers the layer with the electrode. As soon as As the ink nears draining, it takes up the capacity very strong, creating a level transition for on / off He is formed. The capacitive ink level detector does not work as a measuring device, which continuously monitors changing levels of residual ink.

U.S. U.S. Patent Nos. 4,202,267, 4,551,734, 4,719,475, 5,289,211 and 5,388,395 describe all over-technology techniques waking of residual ink level in an ink tank Measurement of the change of an electrical resistance zwi a pair of electrodes.

Japanese Application No. 60-92861 describes a tin tentasche with a magnetic sheet on a surface pocket and a proximity line switch under an opposite surface is arranged. As soon as the ink is depleted, the bag falls to a point together, where the line switch is triggered to on show that the ink level is low. This technique is limited in that it is only a two-state sensor, and Although such that the switch is either on or off. It There is no way to gradually change the Tin supply or inventory.

The object of the present invention is to provide a Ink level detecting device, an ink level detector,  an ink supply cartridge and an ink jet pen create, which make it possible to continuously the ink level to monitor in an ink tank.

This object is achieved by an ink level detection device tion according to claim 1, by an ink level detector according to Claim 5, by an ink supply cartridge according to claim 9 and by an ink jet pen according to claim 10 ge solves.

An ink level detecting device has a flexible one An ink container for storing an ink supply that is from a Inkjet pen is used on. The ink tank has opposite sides that are relative to one another depending on the amount of ink contained in the same is, move. In one implementation, the ink sheet is container formed as a flexible plastic bag.

The ink level detecting device further includes a pair of electrically conductive coils on the against Overlying sides of the ink container are formed. at In an implementation, the coils are metal thin-film conductors printed on the container sides. In this way and Way, the coils move relative to each other with the movement of the opposite sides of the flexible Container.

An ink level detection circuit is ver with the coils ver prevented. The ink level detection circuit generates a Si gnal, which is an electromagnetic field between the spu lenpaar induced. The ink level detection circuit detects then detecting an ink level in the ink container a field change while the coils relative to each other to be moved. The field strength increases as soon as the coils be moved closer to each other.

The inductive ink level detecting device is opposite Systems according to the prior art are advantageous in that  the field grows more strongly than the ink from the container is emptied, giving a more accurate measurement of the ink level allows the ink in the container to empty state approximates. In addition, the inductive ink level Detector used with conductive inks who used the.

Preferred embodiments of the present invention will be described below with reference to the accompanying drawing explained in more detail. Show it:

Fig. 1 is a schematic representation of an ink-jet pen;

Fig. 2 is a schematic representation of an ink level sensing device for an ink jet pen constructed in accordance with one aspect of this invention; and

Fig. 3 is a circuit diagram of the Tintenpegelerfas sungsvorrichtung.

Fig. 1 shows a replaceable ink jet supply cartridge 10 for supplying ink to an ink jet pen used in an ink jet printer. The cartridge 10 is a one-piece disposable storage container having a rigid housing 12 and a Tintenpegelerfassungsvorrich device 14 which is held in the housing 12 . The ink storage cartridge 10 further includes a fluid port 15 which provides an exit for the liquid ink for use by the print head. However, in other implementations, the ink level sensing device 14 itself could form part of an inkjet pen. As used in this application, the terms "pen" and "printhead" are essentially interchangeable.

Fig. 2 shows the ink level sensing device 14 constructed in accordance with one aspect of this invention. The Tin tenpegelerfassungsvorrichtung 14 has a flexible Tin tenbehälter 16 in the form of a flexible, zusammenklappba ren pocket. The ink bag 16 defines an ink reservoire chamber 18 , which holds liquid ink. In one implementation, the ink bag 16 is constructed using multilayer plastic sheets which are sealed along its periphery to form the ink reservoir chamber 18 . The ink bag 16 is preferably dimensioned and constructed for use with a replaceable ink jet pen.

The ink bag 16 has opposite sides 20 and 22 which move relative to each other depending on the amount of ink held in the chamber 18 . The ink pocket 16 has at least one tubular outlet port 15 which is in fluid communication with the chamber 18 through which the liquid ink is transferred to the nozzles for ejection.

The ink level detecting device 14 has a pair of electrically conductive coils 30 and 32 provided on opposite sides 20 and 22 of the ink tank 16 , respectively. Conductors 34 and 36 connect the coils 30 and 32 to an ink level detection circuit 50 , which is described in more detail below.

In the illustrated implementation, the coils 30 , 32 and the conductors 34 , 36 are formed directly on the sides 20 , 22 as me tallische thin-film conductors. The printed conductors may be formed on the inside, on the outside or inside the multi-layered side walls forming the pocket 16 . The thin film conductors forming the coils 30 and 32 can be printed on the plastic bag using photolithographic techniques, or they can be attached to the bag using adhesives.

The coils 30 , 32 move relative to each other in conjunction with a movement of the sides 20 , 22nd As noted above, the pocket sides 20 , 22 move relative to each other depending on the amount of residual ink that is in the ink bag 16 . When the ink bag 16 is full, the spools 30 , 32 are spaced a maximum distance apart. As ink is withdrawn from the ink bag 12 during printing, the spools 30 , 32 move toward each other.

The ink level detection circuit 50 generates a signal which induces an electromagnetic field between the pair of coils 30 , 32 and detects an ink level in the ink tank 16 by detecting a change in the field as the coils 30 , 32 are moved relative to each other. The ink level detection circuit 50 is connected to the coils 30 , 32 via respective conductors 34 , 36 . The ink level detection circuit 50 may be constructed as part of the replaceable ink cartridge, in which case it outputs an ink discharge signal to the ink jet printer. Alternatively, the ink level detection circuit 50 may be constructed separately from the replaceable ink cartridge as part of the continuous control circuitry of the printer. In this latter case, the conductors 34 , 36 are bounded by contacts which are positioned to make connection with conductive receiving surfaces when the stylus is installed in the printer to thereby energize the coils 30 , 32 with the ink level detection circuit removed 50 to couple.

FIG. 3 is a circuit diagram of the ink level sensing device 10 . The ink level detection circuit includes a power generator 52 , a sensor 54, and an ink level monitor 56 . The power generator 52 generates and applies a current to the coil 30 . The current signal may be applied in any type of alternating waveform, where examples thereof are a square wave or a sine wave. The current signal is oriented through the coil 30 to induce an electromagnetic field between the two coils 30 , 32 . The field is aligned along an axis which runs transversely to the sides of the pocket 16 . The strength of the field varies according to the distance of the inter mediate space between the two coils 30 and 32nd The distance is first large and then narrowed, while the ink tentasche is emptied from a full ink supply to an empty ink tenvorrat.

The sensor 54 detects a voltage across the second coil 32 which is induced by the field. The voltage is an indication of the field strength. The ink level monitor 56 uses the voltage used by the sensor 54 to derive a value indicating the residual ink level. When the value calculated by the ink level monitor 56 indicates a point indicating a low or nearly empty ink supply, the ink level detection circuit 50 outputs a control signal to the ink jet printer control unit indicating that the ink level is low. The inkjet printer can then inform the user to swap out the pen or replenish the ink reservoir.

In the illustrated implementation, the current generator 52 generates the current signal from a voltage source. This input voltage is sent to the ink level monitor 56 . The output voltage measured by the sensor 54 is also sent to the ink level monitor 56 . The ink level monitor 56 calculates a ratio of the output voltage to the input voltage to produce a value indicative of the residual ink level in the ink chamber.

The ink level detector was simulated using 1.905 cm (3/4-inch coil) coils, each having ten turns. A sinusoidal current signal with a frequency of 1 MHz and a current rms value of about 100 mA _rms (rms = root mean square) were generated using a sinusoidal voltage source which generates an input voltage of 1.2 Vin _rms . The current was applied to the first coil 30 . A voltage _{sensor was} coupled to the second coil 32 to measure an output voltage Vout _rms . The spacing of the gap between the coils was changed dynamically, measuring the distance at various points representative of ink depletion in the ink bag. A ratio of the output voltage Vout _rms to the input voltage Vin _rms was calculated at each point. Table 1 presents the results:

Gap (mm) strength ratio 11.5 0.15 9.2 0.21 6.9 0.28 4.6 0.38 2.4 0.59 0 1.00.

As can be seen in the results of Table 1, increased the signal strength, while the gap narrows has been. This is useful because the inductive ink detection Device for detecting changes in the remaining ink volume mens becomes more accurate as the ink supply deflates becomes. This accuracy allows the printer to more accurately to detect when the ink level is low and when it is Time is to inform a user that the Ink cartridge or the pen must be replaced.

In the above implementation, one coil is driven with a current or voltage source while the induced voltage of the other coil is measured. In another implementation, the coils 30 and 32 are serially connected. The same signal is passed through the serially connected coils 30 , 32 to induce an electromagnetic field between them. When the coils are wound in the same direction, the field strength increases while the ink is discharged from the ink bag. In contrast, when the coils are wound in opposite directions, the field strength decreases as the ink is discharged from the pocket.

Claims (10)

An ink level detecting device ( 14 ) having the following features:
a flexible ink container ( 16 ); and
a pair of electrically conductive coils ( 30 , 32 ) disposed on opposite sides ( 20 , 22 ) of the ink container ( 16 ), the coils ( 30 , 32 ) relative to each other depending on an amount of ink in the Ink tank ( 16 ) is held, move. 2. An ink level detecting device according to claim 1,
wherein the ink container ( 16 ) has a flexible bag. 3. An ink level detecting apparatus according to claim 1 or 2, wherein the conductive coils ( 30 , 32 ) on the ink container ( 16 ) are formed. The ink level detecting device according to any one of the preceding claims, wherein the conductive coils ( 30 , 32 ) are connected in series. 5. Ink level detector with the following features:
a pair of electrically conductive coils ( 30 , 32 ) which are arranged on opposite sides of a Tintenbehäl ester and move relative to each other in conjunction with an ink level of the ink container; and
an ink level detecting circuit ( 50 ) connected to the coils for inducing a field between the pair of coils ( 30 , 32 ) and an ink level of the ink reservoir by detecting a change in the field as the coils move relative to each other , capture. The ink level detector of claim 5, wherein the signal is applied to a first coil ( 30 ) while inducing a voltage on a second coil ( 32 ) through the field. The ink level detector according to claim 5 or 6, wherein the coils ( 30 , 32 ) are serially connected. The ink level detector according to any one of claims 5 to 7, wherein the panel has a thickness which increases as the coils ( 30 , 32 ) are moved closer to each other. 9. Ink supply cassette, which contains an ink level detector according to any one of claims 1 to 8. 10. Ink jet pen with an ink level detection A device according to any one of claims 1 to 8.