Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
1998-06-25
2001-11-20
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S019000
Reexamination Certificate
active
06318826
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a device for determining a quantity of consumable product present in a reservoir comprising for example at least two compartments, one where the product is in the free state and the other where it is in the captive state.
The invention relates particularly to determination of the quantity of ink remaining in such a reservoir equipping a printing device, more particularly a printing device using ink-jet technology.
A number of ways for detecting a level of ink in a reservoir of a printing device are known. Notably, association with the reservoir is known of a capacitive arrangement to which an excitation signal, generally a high-frequency alternating signal, is applied. It is known that the signal transmitted by such a capacitive arrangement varies according to the quantity of ink remaining in the reservoir. This variation can therefore be used to indicate to the user the fill level of the reservoir or at least the fact that a minimum level has been reached. Such information allows the user to refill the reservoir or to change a cartridge comprising such a reservoir often associated with an ink-jet print head. The capacitive arrangement is such that at least one capacitor of relatively small capacitance (a few picofarads) is constituted so that the reservoir is located or can be located at a given instant between electrodes of such a capacitor.
By way of example, the document EP 0 028 399 describes a method for detecting the minimum level of ink in a reservoir, using a resonant circuit, the capacitor of which is formed by two metal plates (electrodes) between which the ink reservoir is located. The latter therefore fills the dielectric space of such a capacitor and the quantity of ink has a direct effect on the permittivity of the said dielectric space, and therefore the value of the capacitance. The resonant circuit is calibrated so that its resonant frequency and the maximum voltage at its measurement resistance are reached when the level of ink has fallen to a predetermined value. When resonance is achieved, a signal which can be used for signalling is sent. Consequently, with such a system, the only information available is an indication of the fact that the ink level is or is not above a predetermined low threshold.
A reservoir made of insulating material is also known, comprising two compartments, respectively an upstream compartment where the consumable product (conductive ink) is in the free state and a downstream compartment where the same product is in the captive state, that is to say for example impregnating a porous body. The two compartments communicate by means of a passage while the downstream compartment filled with a porous body communicates with a flow output for consumption of the said product. As is known, the porous body makes it possible to better control the flow of the liquid to the device consuming this liquid, in particular the ink-jet print head in the case of a document printing device.
On the other hand, a larger quantity of ink can be stored, all things being equal in other respects, in the upstream compartment which lacks a porous body. The liquid contained in the upstream compartment is progressively absorbed by the porous body as the liquid flows out of the downstream compartment.
When the upstream compartment is empty, the porous body progressively contains less in liquid product, until it is completely drained.
SUMMARY OF THE INVENTION
One aim of the invention is to indicate a measurement of the quantity of consumable product remaining in the reservoir until it is completely or practically completely drained of product, throughout the duration of use, that is to say before and after the compartment is drained, in order to allow the user to fill the reservoir again or to change it, at the proper moment.
According to the invention, these aims are achieved by the particular structure of the capacitive arrangement associated with such a compartmental reservoir, where the consumable product is electrically conductive.
This is because, where the consumable product, that is to say the ink, is an electrically conductive product, and where the walls of the reservoir are made of insulating material, the capacitive arrangement indicated above can be constituted by one or more capacitors. Each capacitor is in fact defined by a metallic external conductive electrode, applied against a face of the said reservoir, on the one hand, and by the conductive liquid itself contained in the reservoir and constituting another electrode, the surface area of which is, as it were, variable and depends on the quantity of product contained in the reservoir at a given instant. In this case, the dielectric of the capacitor is constituted by the insulating wall of the reservoir.
More particularly, the invention concerns a device for determining a quantity of electrically conductive liquid consumable product contained in a reservoir made of insulating material, comprising at least one volume where the said product is in the captive state, of the type also having a capacitive arrangement including conductive electrodes applied on external surfaces of the said reservoir, an excitation signal generator connected to the said capacitive arrangement and detection and measurement means capable of receiving and processing a resulting signal transmitted by the said capacitive arrangement and representing the quantity of consumable product present in the said reservoir, characterised in that the said capacitive arrangement has capacitors associated with the said volume and comprising at least two electrodes applied on two opposite faces of the reservoir, and in that these two electrodes are situated on either side of the said volume where the product is in the captive state and offset with respect to one another in order to be located respectively in the vicinity of two opposite ends of this volume.
By way of a preferred application, the said reservoir made of insulating material comprises at least one upstream compartment where the said product is in the free state and one downstream compartment giving substance to an aforementioned volume where the said product is in the captive state, the two compartments communicating by means of a passage.
According to one possible embodiment, the ink in the downstream compartment impregnates a porous body. It has been noted that such a porous body impregnated with a conductive ink behaves as an impedance with however an essentially real component. It is in this sense that it can be considered that the ink is conductive as indicated above, including in the downstream compartment.
According to another possible embodiment, the device is again characterised in that capacitors associated with the upstream compartment, comprising two electrodes applied on two faces of the upstream compartment, each extend over at least part of the said face being disposed facing one another so as to flank at least part of the said upstream compartment situated in the vicinity of the said passage.
Thus two electrodes respectively applied against faces of the two compartments are joined together and connected to the excitation signal generator, which may be a high-frequency alternating signal generator, while two electrodes respectively applied against other faces of these two compartments are joined together and connected to the said detection means. These therefore receive a signal returned or transmitted by the capacitive arrangement in response to the excitation signal delivered by the said generator and this signal represents the quantity of liquid product remaining in the reservoir. The detection means may include an envelope detector and, in cascade with the latter, an analogue to digital converter connected to convert the signal coming from the envelope detector into digital information.
Where such a device for determining the quantity of product contained in the reservoir is associated with a document printing device, the microprocessor-based main processing circuit of this printing device controls the input
Coudray Pascal
Froger Marie-Helene
Barlow John
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Stewart Jr. Charles W.
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