Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
1998-05-22
2001-10-30
Barlow, Jr., John E. (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
Reexamination Certificate
active
06310635
ABSTRACT:
The invention relates to a device for determining a quantity of consumable product present in a reservoir and more especially a reservoir forming part of a movable appliance able to move along a predetermined path.
In this regard, the invention also concerns, as an application, a document printing device which has a movable appliance provided with such an ink reservoir, preferably removable and/or exchangeable and provided with such means for determining the quantity of ink remaining in the reservoir.
Several principles used notably in printing devices using ink jet technology are known for determining the level of ink remaining in a reservoir or at least detecting a minimum level, enabling the user to be alerted to the need to fill a reservoir or, more often, to change a cartridge comprising such a reservoir, generally associated with an ink jet printing head. Some of these principles use a capacitor of relatively low capacitance (a few picofarads) produced in such a way that the reservoir is located or is able to be located at a given moment between two plates of this capacitor, that is to say in the dielectric space thereof. In this way, the quantity of ink present in the reservoir has a direct influence on the overall permittivity of the said dielectric space. This correlation is used to determine the quantity of ink in the reservoir.
For example, the document EP 0 028 399 describes a method for detecting the minimum level of ink in a reservoir, using a resonant circuit whose capacitor is formed by two metal plates between which the ink reservoir is located. 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 on the value of the capacitance.
The resonant circuit is calibrated so that its resonant frequency and the maximum voltage in its measurement resistor is reached when the level of ink reaches a predetermined low level. When the resonance is reached, a signal able to be used for the warning signal is transmitted. Consequently, with such a system, the only information available is an indication of whether or not the level of ink is higher than a predetermined lower threshold.
In the prior system indicated above, the capacitor is associated with an inductor coil and with an alternating signal generator to form the aforementioned resonant circuit. The value of the resonant frequency is therefore
F
0
=
1
2
π
LC
,
where L is the value of the inductance and C the value of the capacitance of the capacitor associated with the reservoir.
However, the value of this capacitance is, as has been seen, around a few picofarads. It would be advantageous for the resonant frequency of this resonant circuit to be situated and to move within a range of frequencies around 1 kHz or a few tens of kHz. However, with a capacitor which has such a low capacitance, the inductance would need to be equal to several tens of henries. This is impracticable, if not technologically then at least in terms of cost. This is why, in a prior device as described above, the resonant frequency is situated and moves within a range of frequencies larger than 1 MHz. Furthermore, the adjustment of this resonant frequency is directly linked to the precision of the inductance. This makes it more difficult to produce, and therefore increases the cost of the device. If it is attempted to reduce the value of the inductance, it becomes necessary to further increase the resonant frequency up to several tens of MHz, and problems of electromagnetic radiation are then encountered.
The invention aims notably to resolve the problems described above by making it possible to define a resonant circuit which incorporates the low-value capacitor associated with the reservoir as indicated but nonetheless having a resonant frequency situated and moving in average frequencies. In this case, average frequency is understood as a frequency between approximately one or few kHz, or indeed several tens of kHz. A resonant circuit of this type is optimum for the application envisaged in that it avoids the need to use expensive or bulky components and/or those requiring fine adjustment. The problems of electromagnetic radiation described above are also avoided.
The invention preferably aims to indicate a measurement of the quantity of consumable product remaining in the reservoir and not simply to indicate that a predetermined value, representing a low level, has been reached.
The invention particularly relates to a device for measuring a level of ink in a printing device comprising an exchangeable cartridge comprising an ink reservoir, the arrangement requiring no or practically no modification of the cartridge.
The basic idea of the invention consists of using the low-value capacitor associated with the reservoir as a component of an electronic circuit forming a notional inductor, that is to say having an impedance comparable to that of an inductor coil, increasing with the frequency, and combining with this circuit forming a notional inductor another capacitor to form the resonant circuit.
More specifically, the invention therefore concerns a device for determining a quantity of consumable product present in a reservoir, of the type comprising:
a capacitor comprising two conductive elements forming the plates thereof, disposed in such a way that the said reservoir is situated at least partly in the dielectric space defined by the said two plates,
a resonant circuit comprising the said capacitor and connected to an excitation signal generator,
detection means connected so as to receive a signal coming from this resonant circuit and representing the said quantity of consumable product,
characterised in that the said capacitor is incorporated into a circuit forming a notional inductor and in that this circuit is associated with another capacitor to form the said resonant circuit.
A notable advantage of the invention lies in the fact that the resonant circuit thus produced is entirely devoid of a winding producing the inductor coil, component which is generally expensive and bulky.
A circuit constituting such a notional inductor is known per se.
In the context of the preferred application to a document printing device, the reservoir is an ink reservoir and is associated with a printing head situated in the immediate vicinity thereof. Such a printing head has a circuit made of silicon or another conductive element which can form one of the plates of the said capacitor. This conductive element can be at least part of the ink ejection control circuit of the said printing head.
In this case, advantageously, a selector controlled by the central unit of the printing device is provided to switch to the said printing head either the ink ejection control circuit or the resonant circuit with gyrator, at the moment when the quantity of ink remaining in the reservoir is to be measured.
Furthermore, one of the plates of the said capacitor is applied to a face of the said reservoir. The latter is made of insulating material and the plate can be produced by a metal plate abutting on a face of the reservoir and applied thereto or even by a metallisation carried by this face of the reservoir.
As a variant, the two plates of the capacitor can be plates applied to two faces of the reservoir, in which case the printing head does not form part of a plate of the said capacitor but simply forms an element occupying its dielectric space.
Of course, the invention also concerns any office machine having a device as defined above, notably for determining the quantity of ink remaining in a reservoir of a printing device. Such an office machine can consist essentially of a printer or a facsimile machine.
The invention also concerns any microcomputer having at least one device for determining ink levels as defined above.
The invention also relates, as a component enabling it to be implemented, to any ink refill cartridge for a device for printing documents characterised in that it has a reservoir and in that a conductive surface car
Coudray Pascal
Froger Marie-Helene
Lorgeoux Mickael
Barlow Jr. John E.
Canon Kabushiki Kaisha
Stewart Jr. Charles W.
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