Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
1997-07-02
2001-07-03
Grimley, Arthur T. (Department: 2852)
Incremental printing of symbolic information
Ink jet
Controller
C399S061000
Reexamination Certificate
active
06254212
ABSTRACT:
The present invention concerns, in general terms, a method and device for determining the quantity of product present in a reservoir, and more particularly for determining the quantity of ink present in the reservoir of an image forming device.
For image forming devices, such as printers, which use ink-jet technology, numerous devices and methods have been designed to determine the quantity of ink.
A first known type of detection uses the electrical characteristics of ink by measuring the resistance thereof between two electrodes.
The document EP-A-0 370 765 describes a device for detecting the quantity of ink present in a reservoir, comprising two electrodes positioned in the channel connecting an ink ejection head to the ink reservoir and a means of detecting the electrical resistance between the two electrodes. The first electrode is situated close to the ejection head while the second is distant from it. A potential difference is applied between these two electrodes. The resistance of the ink present in the reservoir is measured. The result shows that the resistance measured increases non-linearly when the quantity of ink in the reservoir falls.
The measurement of a resistance between two electrodes does not allow the quantity of ink to be measured precisely. This is because the variation in the resistance of the ink present in the reservoir, as a function of the variation in the quantity of ink, is a complex relationship, having a curve such that it approaches an “all or nothing” relationship.
A second known type of detection uses the electrical characteristics of the ink by measuring the capacitance thereof.
The document U.S. Pat. No. 4,700,754 describes detection of the level of liquid ink in a flexible reservoir which retracts as the level of ink falls. The bottom external wall is coated with a conductive layer forming an electrode of a capacitor. The wall of the reservoir serves as a dielectric for the capacitor thus produced while the surface of ink in contact with the bottom wall constitutes the second face of the capacitor. A measurement electrode positioned at the centre of the reservoir connects the ink to a measuring device. When the level of ink falls, the ink surface opposite the conductive layer coated on the wall falls, and so the value of the equivalent capacitance also falls. The fact that the reservoir is flexible enables the measurement electrode to remain in contact with the ink.
This second type of detection is used for a cartridge with flexible walls and cannot be applied to rigid cartridges. This is because the contact between the measurement circuit and the ink can be produced only if the top wall, when it is crushed, forces the measurement electrode to make contact with the ink.
Moreover, this measurement of the level of ink is possible only for liquid ink contained in a reservoir without a porous body.
In addition, it is difficult to know the level of ink if this is below a level between the measurement electrode and the bottom wall. This is because the measurement electrode is unable to descend to the bottom of the reservoir. The range of measurement is thus limited for the low values.
Moreover, more and more image forming devices have several different coloured ink reservoirs for producing more elaborate pictures.
The reservoirs are for example combined in the same cartridge, or if they are independent, they are situated close to one another for practical reasons of use.
The devices and methods known for determining the quantity of ink in a single reservoir cannot easily be adapted to determining the quantity of ink present in a selected one of several reservoirs situated close to one another.
Thus the document U.S. Pat. No. 4,145,927 describes a device for measuring the quantity of liquid present in a reservoir. This method measures the capacitance between two metal plates fixed parallel on the external wall of the reservoir. The two plates are the terminals of a capacitor, the dielectric of which is formed by the wall of the reservoir and the liquid contained in the reservoir.
In order to measure quantities of liquid present in several reservoirs, it is necessary to provide as many pairs of plates as there are reservoirs, which complicates the implementation and increases the cost thereof.
Also, if the liquid is accidentally connected to earth, for example by means of parasitic connections, the device no longer operates and no longer gives a measurement of the quantity of liquid present in the reservoir.
Moreover, the document U.S. Pat. No. 5,315,872 discloses a device for measuring the quantity of liquid present in a reservoir, the walls of which are composed of conductive particles. An electrically isolating layer is disposed on the internal surface of the reservoir and the liquid is connected to earth. The capacitance between the conductive walls of the reservoir and earth is measured. The variation in capacitance is due to the variation in the quantity of liquid present in the reservoir.
This device is not suited to measuring the quantity of liquid in several reservoirs situated close to one another, or several compartments of one reservoir.
This is because, under these conditions, it is difficult to dissociate the measurements made in each of the reservoirs, that is to say to measure the quantity of liquid present in one reservoir, independently of the quantities of liquid present in the other reservoirs.
Also, for reasons of cost and ease of implementation, it is not desirable to have as many measuring devices as reservoirs.
A first object of the present invention is to overcome the drawbacks of the prior art by providing a device and method for determining the quantity of product present in a reservoir which gives, with a satisfactory degree of reliability, the quantity of product in the largest range of measurement, while being simple and economical to implement.
A second object of the present invention is to measure the quantity of product present in a selected one of several reservoirs situated close to one another. The device and method according to the invention give, with a satisfactory degree of reliability, the quantity of product in the selected reservoir, while being simple and economical in design and implementation.
In the course of their research, the inventors observed that an electrical excitation of a product modifies the electrical characteristics of the product, and that this modification depends not only on the excitation signal, but also on the quantity of product. In the light of this, the invention consists of analyzing the effects produced by an electrical excitation of the product.
In a first aspect of the present invention, the electrical excitation of the product leads to electromagnetic radiation therein. The invention then consists of analyzing the radiation produced by an electrical excitation of the product.
To this end, the invention provides a method of determining a quantity of product present in a reservoir, characterised in that it includes the steps of:
applying a predetermined excitation signal to the product present in the reservoir, so that the product radiates an electromagnetic signal,
sensing the electromagnetic signal radiated by the product with a sensing means producing an electrical signal representing the electromagnetic signal, and
processing the electrical signal to produce a signal representing the quantity of product present in the reservoir.
In a second aspect of the present invention, the electrical excitation of the product leads to the formation of an electric field therein. The invention then consists of analyzing the electric field produced by an electrical excitation of the product.
The invention also enables measurement of the quantity of product present in a selected one of several reservoirs situated close to one another.
The invention then consists in the main of connecting one of the products, the quantity of which it is wished to measure, to a predetermined potential, and then establishing an electric field across the reservoirs and measuring this electric field.
During th
Coudray Pascal
Froger Marie-Helene
Truffaut Christophe
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Grimley Arthur T.
Tran Hoan
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