Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
1998-01-08
2001-12-04
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S019000
Reexamination Certificate
active
06325477
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 formation device. The present invention also concerns a product reservoir, notably an ink reservoir for an image formation device. It also concerns a device for processing electrical signals intended to be used in a device for determining the quantity of product present in a reservoir.
For image formation devices, such as printers, which use ink jet technology, numerous devices and methods have been designed for determining the quantity of ink present in the reservoir.
The document U.S. Pat. No. 4,700,754 describes a device for detecting the quantity of liquid ink in a flexible reservoir contracting as the ink level decreases. The external bottom wall is coated with a conductive layer constituting one pole of a capacitor. The wall of the reservoir serves as a dielectric of the capacitor thus produced whilst the ink surface in contact with the bottom wall constitutes the second pole of the capacitor. A measuring electrode placed at the centre of the reservoir connects the ink to a measuring device. When the ink level decreases, the surface area of ink facing the conductive layer coated on the wall decreases, and therefore the value of the equivalent capacitance also decreases. The fact that the reservoir is flexible enables the measuring electrode to remain in contact with the ink.
This type of detection is used for a cartridge having flexible walls and cannot be applied to rigid cartridges. This is because contact between the measuring circuit and the ink can be made only if the top wall, when it is crushed, forces the measuring electrode to be in contact with the ink.
In addition, it is necessary to provide an electrode in contact with the ink in the reservoir, which complicates the manufacture of the reservoir and increases the cost thereof.
Moreover, it is difficult to know the ink level if the latter is below a level lying between the measuring electrode and the bottom wall. This is because the measuring electrode cannot go down as far as the base of the reservoir. The measurement range is thus limited in the lower values. However, it is precisely when there is very little ink remaining in the reservoir that it is advantageous to be alerted so as to change the reservoir or fill it.
The document EP-A-0 028 399 describes a device for detecting a minimum quantity of ink in a reservoir. A resonant circuit includes a resistor and a capacitor whose poles are formed by two metal plates between which the ink reservoir is situated. The reservoir containing the ink forms the dielectric of the capacitor. As the quantity of ink decreases, the value of the capacitance of the capacitor thus formed varies.
The resonant circuit is calibrated so that its resonant frequency corresponds to a predetermined quantity of ink in the reservoir. The maximum voltage at the terminals of the resistor is thus achieved for this predetermined quantity of ink which constitutes a threshold.
By measuring the voltage at the terminals of the resistor of the resonant circuit, the passing of the threshold is detected, and a warning signal is activated.
According to this document, only the passing of a threshold is measurable, and consequently only a quantity of ink can be detected. Under these circumstances, this device is of interest if the quantity of ink detected is small, in order to alert the user just before there is no more ink in the reservoir.
However, it is very difficult with this device to determine accurately what voltage corresponds exactly to a small quantity of ink. It is then necessary to provide a safety margin in order to alert the user before the reservoir is empty. This safety margin, for example around 20 percent of the total quantity of ink, results in a waste of ink, since the user will change the reservoir whilst there is still ink inside.
The present invention aims to remedy the drawbacks of the prior art by providing a device and method for determining the quantity of product present in a reservoir, which determines, with satisfactory reliability and with precision, a predetermined quantity of product, whilst being simple and economical to implement.
For this purpose, the invention proposes a method for determining the quantity of product present in a reservoir, characterised in that it includes the steps of:
connecting the said product to a predetermined potential,
establishing an electrical field through the product present in the reservoir,
measuring the electrical field passing through the product, in order to produce an electrical signal representing the electrical field, and
processing the electrical signal in order to produce a signal representing the quantity of product present in the reservoir, and to detect the interruption of the connection of the product to the predetermined potential, the said interruption corresponding to a predetermined quantity of product present in the reservoir.
In general terms the invention applies to any product, notably a consumable product used in a given device.
Preferably, the invention applies to ink contained in the reservoir of an image formation device. “Ink” here designates any liquid, solid, gaseous or powder product intended to modify an optical or physical factor of the printing medium.
The method according to the invention not only has the advantage of resolving the technical problems set out above, but also of being adaptable to a large number of existing devices.
By virtue of the invention, the predetermined quantity of product which is determined with precision is for example a zero, or quasi-zero, quantity, or any other quantity, according to the requirements relating to each application of the invention.
According to one of the aspects of the invention, the connection of the product to the predetermined potential is a connection of the capacitive type, advantageously avoiding direct contact of the product with a part at a potential.
According to a preferred characteristic, the step of processing the electrical signal includes the detection and storage in memory of the amplitude of the electrical signal and the comparison of the said amplitude with at least one amplitude previously detected and stored to memory.
This comparison makes it possible to monitor the change in amplitude and to detect an abrupt change in the values measured, which indicates the interruption of the connection of the product to the predetermined potential.
According to one characteristic of the invention, the method also includes the step of indicating the detection of the said predetermined quantity of product present in the reservoir, or the step of transmitting a signal representing the detection of the said predetermined quantity of product present in the reservoir to a remote device so that it displays a message representing the detection of the said predetermined quantity.
The user is thus alerted to the fact that the predetermined quantity is reached. For example, if this quantity is zero, or quasi-zero, he can fill the reservoir or replace it with a full reservoir.
According to a preferred characteristic, the processing step includes the detection of the amplitude of the electrical signal, and the production of the signal representing the quantity of product from a value given by a calibration table according to the amplitude detected.
The method also includes the step of displaying a representation of the quantity of product present in the reservoir, or the step of transmitting the signal representing the quantity of product present in the reservoir to a remote device so that it displays a representation of the quantity of product present in the reservoir.
This product being a consumable product used in a given device, the user knows at any moment the quantity of product remaining in the reservoir and is thus capable, for example, of deciding to fill the reservoir before it is completely empty, or to replace the empty reserv
Coudray Pascal
Froger Marie-Helene
Barlow John
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Stephens Juanita
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