Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1999-05-06
2001-10-09
Le, N. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06299280
ABSTRACT:
The invention concerns the transmission of information between two elements movable with respect to each other along a path; it relates in particular but not exclusively to the transmission of information between the control for a print head and the latter within a printing device, and/or vice versa. In practice, such a printing is effected on paper, but can also be effected on any other medium, notably textile (for example in roll form), plastic materials, etc.
In printing devices using inkjet technology, the ink cartridge and its print head are mounted on a reciprocating carriage actuated by a motor. This movement takes place over the entire width of the sheet.
In order to transmit the digital information necessary for the correct functioning of the print head, a flexible cable provides an electrical connection between the central unit of the printing device and its print head.
This cable must meet a certain number of mechanical constraints. It must be sufficiently flexible to be able not to interfere with the movement of the carriage and in particular long enough to be able to move the carriage over the entire length of the printing medium.
It should be noted that ink-jet technology is used for printing documents whose size can range up to A0 format.
This type of electrical connection has a certain number of defects.
The first is related to the length of the cable, which is greater, the longer the printing medium. This has a direct effect on the cost of this cable.
The need to have qualities of resistance to deflection for this long cable also increases the cost of the device.
Another method of transmitting information between the processing unit and the print head consist of using a means of optical transmission of the data to the carriage. This is described notably in the document EP-94306138, which proposes a printer provided with an optical transmission link for the transmission of data between the device controlling the printer and its print head mounted on a reciprocating carriage. The print data are conveyed from the control to the head, passing through a fixed point on the edge of the carriage, and the status data can be conveyed in the reverse direction. In addition, power is supplied to the head by two parallel rails on which the carriage is supported in order to be moved in a reciprocating motion by the motor driving the carriage mounted on the chassis. This carriage is provided with conductive lugs in sliding contact with these rails. The information is in practice transmitted by an infrared light beam.
This type of connection has a certain number of defects.
The first is related to the cost of the optical links. The components used for this type of link are relatively expensive, in particular when the information transmission rates are of the order of several hundreds of kilobits per second.
In addition, the use of ink-jet technology for color printing requires transmission rates of the order of megabits per second.
However, transmission of information optically can take place only through a single optical link. It is difficult in fact to produce optical links in parallel. These interfere with each other.
The field of application of the optical method for the transmission of printing data is therefore limited.
In fact this type of problem is found in other applications where information is to be transmitted from a first body to a second body movable with respect to the first, without it being wished to use a flexible connecting cable.
The invention aims to mitigate the aforementioned drawbacks, by virtue of a mode of transmitting information which does not require a flexible cable between the chassis of the printer and the carriage, while guaranteeing good reliability, at moderate cost and with a significant transmission rate, affording in this regard a parallel transmission of several streams of information.
In general terms the invention proposes to proceed by means of a capacitive transmission, through at least one capacitor formed by two plates fixed respectively to two bodies in relative movement and which remain opposite each other, at a constant distance, during this relative movement, so that the said capacitor has a substantially constant capacitance.
It should be noted that one of these plates must in practice have a size at least equal to the relative movement between the bodies; in addition, accurately maintaining the capacitance of the capacitor entirely within the relative movement between the bodies assumes very precise control of the separation between the plates, which a priori appears all the more difficult, the greater the movement. It has however been found that the quality of the guidance which can be obtained during the movement of a body, such as a printing carriage, with respect to another body, such as the chassis of a printing machine, and the accuracy with which plates or tracks along a path between bodies could be produced, such as the aforementioned ones, were sufficient to obtain a substantially constant capacitance.
It could also be feared that the presence of large plates would have the drawback of collecting numerous parasitic signals, liable to interfere with the transmission of information to an unacceptable degree. Tests showed however that this risk was in reality much lower than might be imagined.
More precisely the invention proposes a method of transmitting digital information between a first device carried by a first body and a second device carried by a second body movable with respect to the said first body along a path within a given range of movement, according to which:
at least one first electrically conductive main plate is disposed on the first body and a second electrically conductive main plate is disposed on the second body so that these main plates remain opposite each other, at a constant distance from each other, when there is a relative movement of the second body with respect to the first body within its range of movement along the path and thus constitute a main capacitor with a constant capacitance;
and, in order to transmit information from one of the devices to the other, this information is coded into at least one binary coded signal, this coded signal is applied to the main capacitor, the signal received is decoded and the decoded received signal is transmitted to the other device.
Naturally the transmission is effected notably from the fixed device (in practice the first device) to the movable device (in practice the second device).
There may be several main capacitors, intended to allow the transmission of several information flows in parallel.
There may also be secondary capacitors, to allow the transmission of secondary information or other signals. Thus, advantageously:
a first electrically conductive secondary plate is disposed on the first body and a second electrically conductive secondary plate is disposed on the second body so that these secondary plates remain opposite each other, at a constant distance from each other, when there is a relative movement of the second body with respect to the first body within its range of movement along the path and thus constitute a secondary capacitor with a constant capacitance; and
by means of this secondary capacitor at least one other information signal is transmitted from one of the devices to the other.
This other item of information can be a reference concerning the coding, intended to afford effective decoding. This may be the indication of a coding frequency, and the indication of the transition times during this coding: thus, in a preferred fashion, by means of this secondary capacitor a clock signal with a frequency advantageously included within the passband of the said secondary capacitor is transmitted. This clock frequency is for example around 1 to 10 Mhz.
The main and secondary capacitors can have different capacitances. However, they advantageously have substantially equal capacitances, which makes it possible to transmit signals with similar characteristics by means of them. This is why, preferably, the main capacitor is designed so
Coudray Pascal
Froger Marie-Helene
Canon Research Centre France S.A.
Fitzpatrick ,Cella, Harper & Scinto
Hsieh Shih-Wen
Le N.
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