Measuring and testing – Liquid level or depth gauge – Immersible electrode type
Reexamination Certificate
1998-03-24
2001-06-19
Williams, Hezron (Department: 2856)
Measuring and testing
Liquid level or depth gauge
Immersible electrode type
C073S29000R, C324S658000, C324S660000, C324S661000, C324S662000, C324S663000, C361S284000, C361S289000, C361S290000
Reexamination Certificate
active
06247363
ABSTRACT:
The invention relates to a method for determining a quantity of consumable product present in a reservoir forming part of a movable appliance able to move along a predetermined path.
The invention also concerns a device for measuring a quantity of consumable product present in a reservoir forming part of such a moving appliance and, by way of application, an inkjet document printing device of the type having a removable and/or exchangeable movable appliance comprising at least one ink reservoir and provided with a measuring device in question.
Several principles used notably in printing devices using inkjet technology are known, for measuring the level of ink in a reservoir or at least for detecting a minimum level making it possible to indicate to the user the need to fill a reservoir or most often to change a cartridge containing such a reservoir.
For example, U.S. Pat. No. 4,700,754 describes a method for detecting the presence of a quantity of ink in a flexible reservoir contracting as the ink is consumed. The bottom wall of this reservoir is coated with a conductive layer constituting the electrode or plate of a capacitor. The wall of the reservoir serves as a dielectric and the ink constitutes the second plate of the capacitor. It must be conductive and an electrode is immersed therein in order to connect the ink to the measuring device. When the quantity of ink falls, the ink surface opposite the conductive layer coated on the external wall of the reservoir decreases and consequently the value of the equivalent capacitance also decreases. This principle has a certain number of failings. In the first place, the reservoir must have flexible walls since galvanic contact between the measuring circuit and the ink can be effected only if the top wall (by collapsing) forces the electrode to remain in contact with the ink. The measuring arrangement, requiring an electrode in contact with the ink in the reservoir, is relatively complex. It is also difficult to know the level of ink when this is less than the distance separating the contact electrode from the bottom wall. In addition, it is necessary to change the frequency of the measuring signal continually in order to evaluate the ink level, which requires the use of complex and expensive electronic systems.
In addition, the document EP 0 028 399 describes a method for detecting the minimum level of ink in a reservoir, using an oscillating circuit whose capacitor is formed by two metal plates between which is situated the ink reservoir. The latter therefore fills the dielectric space of the said capacitor and the quantity of ink has a direct influence on the permittivity of the said dielectric space and therefore the value of the capacitance. The oscillating circuit is calibrated so that its resonant frequency and therefore the maximum voltage at its measuring resistor is achieved when the ink level reaches a predetermined low value. When the resonance is reached, a signal which can be used for indicating is sent. Consequently, with such a system, the only information available is an indication that the ink level is or is not above a predetermined low threshold. If it is wished to obtain more precise information relating to the quantity of ink present in the reservoir, it would be necessary to increase the number of reference values using, for example, an analogue to digital converter. Such a solution is very expensive.
The invention concerns a type of measurement as described above in which the quantity of ink contained in a reservoir is situated, at least during the measuring time, in the dielectric space of a capacitor in order to affect the permittivity thereof.
The invention relates to a simple measuring system operating at a fixed frequency and not requiring the use of an analogue to digital converter.
The invention preferably aims to indicate a measurement of the quantity of ink remaining in the reservoir and not only to indicate that a predetermined value, constituting a low level, has been reached.
The invention relates to a device for measuring an ink level in a printing device comprising an exchangeable cartridge enclosing an ink reservoir, the arrangement requiring no or practically no modification to the cartridge.
The invention relates to a concept which can be used for any type of ink cartridge, with a flexible or rigid reservoir.
The basic idea of the invention involves establishing a biunique relationship between the quantity of ink present in a reservoir engaged in the dielectric space of he capacitor and a distance travelled by this reservoir secured to an appliance which is able to move between two positions, so that a signal transmitted by the said capacitor reaches a predetermined level.
According to the invention, a capacitor is formed through which a signal is caused to pass, the reservoir containing the ink being placed in the dielectric space of this capacitor, and this dielectric space is modified by moving at least the reservoir, or even one of the plates of the capacitor with it in order to vary the value of the capacitance, and consequently modify the value of the signal transmitted by this capacitor. According to the position of the reservoir when a predetermined threshold is reached, a distance of movement of the reservoir is determined which represents the quantity of product which it contains.
In other words, the invention therefore concerns a method for determining a quantity of consumable product present in a reservoir forming part of a movable appliance able to move along a predetermined path, which comprises the steps of:
forming a capacitor from two conductive plates situated along the said path so that the said path passes through the dielectric space of the said capacitor,
applying a signal to the said capacitor and measuring a resulting signal depending on the value of the capacitance of the capacitor,
moving the said reservoir along a portion of the said path passing through the said dielectric space,
determining the distance travelled by the said reservoir between two positions, a variable position through which the said resulting signal passes through a predetermined threshold value and a fixed position, and
deducing the said quantity of product present in the reservoir as a function of the said distance.
According to a preferred variant, the method includes placing the said reservoir in a predetermined starting position in which it is situated in the said dielectric space and then moving it in a direction suitable for reducing the value of the capacitance of the capacitor until the resulting signal reaches the predetermined threshold value and measuring the distance through which the reservoir has been moved at the moment the threshold value is reached in order to deduce therefrom the said quantity of product.
The invention also concerns a device for determining the quantity of consumable product present in a reservoir forming part of the movable appliance made to move along a guide means under the action of a drive means, that has:
a capacitor formed by two conductive plates installed along the guide means so that the reservoir can engage in the dielectric space of this capacitor,
signal generation means connected so as to apply this signal to the capacitor,
receiving means for picking up a resulting signal transmitted by the capacitor in response to the signal,
comparative means for comparing the resulting signal with a predetermined threshold value, these comparative means producing an output signal when the resulting signal reaches the threshold value,
means for measuring the movement of the movable appliance and means for establishing an item of information representing the quantity of consumable product as a function of a distance travelled by the movable appliance between two positions, a predetermined position and a position in which the threshold value is reached.
Preferably, the movable appliance is moved by a stepping electric motor. In this case, the distance travelled by the reservoir is determined by counting the number of steps of the motor during the travel of the
Coudray Pascal
Froger Marie-Hélàne
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Loo Dennis
Williams Hezron
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