EP0012887B1 - Ink jet printer for vertical and horizontal printing - Google Patents

Description

Technical area

The present invention relates to an inkjet printer capable of printing horizontally and vertically.

State of the prior art

In a conventional ink-jet printer of the type described, for example, in US Pat. No. 3,596,275, a pressurized ink jet leaving a nozzle is exposed to disturbance and is divided into droplets at a predetermined distance from the outlet of the nozzle. The droplets thus formed receive a charge imparted to them by a charging electrode and then pass between a pair of deflection electrodes to which a high voltage is applied. The value of the charge applied to the ink droplets by said electrode determines the extent of the vertical deviation which is imparted to them so that characters or symbols can be formed by the droplets on a printing medium, such as 'a sheet of paper, placed in the immediate vicinity of said deflection electrodes. In general, if no characters are to be formed on the paper, the droplets receive no charge, or receive only a weak charge, and therefore are not deflected as they pass between the deflection electrodes; they are then intercepted by a gutter, from where they are brought back to their starting point for reuse in the system. One such printer is the IBM 6640 printer which is part of the IBM 6 system.

It follows from the above that the vertical deviation imparted to the ink droplets makes it possible to form a column of dots on the sheet of paper or other support. Each of the droplets of a column thus formed receives a slightly larger charge than the previous droplet, so that the column is traced, in the example cited, from bottom to top. The characters are thus formed, within a particular matrix, by means of a series of columns. In general, the various elements of the print head are located on a carriage which moves in a predetermined direction along the surface of the paper or other medium.

Some languages, such as Japanese, can be printed vertically or horizontally on the media. It is therefore essential that the series of ink droplets is deflected vertically for the purposes of horizontal printing and horizontally for the purposes of vertical printing. This result can obviously be obtained by using pairs of horizontal and vertical deflection plates, the excitation of a chosen pair making it possible to carry out a horizontal or vertical printing. However, an ink mist tends to accumulate, in such cases, on the plates which are not excited, which requires periodic cleaning of the device. Furthermore, the voltage applied to the deflection electrodes is necessarily very high, so that switching the power supply from one pair of plates to another is difficult, the power supply normally having to be cut off before each switching. This difficulty could obviously be avoided by using a separate power supply for each pair of plates, but this is not necessary in the case of the printer of the present invention, which can operate correctly without having to provide the necessary electrical circuits associated with such duplication of power supplies.

US Pat. Nos. 3,715,219, 3,786,516 and 3,938,163 describe horizontal and vertical deflection electrodes, but which are not intended to allow printing in one direction or the other. These three patents describe the electrical means used to modify the electric field for different purposes, for example to compensate for the lateral speed of the series of ink droplets during printing. No reference is made in these patents to the placement of plates obtained mechanically or by rotation so as to allow the ink-jet printer to print characters vertically or horizontally.

The IBM Technical Disclosure Bulletin, vol. 15, n ° 9, February 1973 describes an ink-jet printer in which the rotation of the deflection plates around an axis perpendicular to the printing medium makes it possible to print slightly inclined characters, such as italic characters, from data relating to a conventional typeface. However, this document does not describe the possibility of printing vertically or horizontally from the ink-jet printer of the present invention.

Statement of the invention

The present invention relates to a printer according to claim 1.

One of the objects of the present invention is therefore to modify the orientation of the electric field in an ink-jet printer so as to make vertical printing as well as horizontal printing possible.

Another object of the present invention is to allow the use of a single pair of plates to create the deflection electric field required for the purposes of horizontal printing and vertical printing.

Other objects, characteristics and advantages of the present invention will emerge more clearly from the following description, made with reference to the drawings appended to this text, which represent a preferred embodiment thereof.

Brief description of the figures

• Figure 1 is a partial schematic view of an inkjet printer incorporating the device of the present invention.
• Figure 2 is a partial enlargement of part of the device shown in Figure 1, taken along line 2-2 of Figure 1.
• Figure 3 shows the part of the device of Figure 2, but shows some parts of it in a different position.
• Figure 4 schematically shows the device of Figures 1 to 3 in the positions indicated in Figures 2 and 3 and its interconnection with the drive devices of the carriage and the platen that the printer comprises.
• Figure 5 is similar to Figure 4 and shows schematically the circuits necessary to switch the printer so that a horizontal or vertical print of the characters is obtained.
• Figure 6 is a partial side view of another embodiment of the device of the present invention which provides a vertical or horizontal impression.
• Figure 7 is a partial section taken along line 7-7 of Figure 6.

Description of an embodiment of the invention

FIG. 1 schematically shows an ink-jet printer produced in accordance with the present invention. Pressurized ink 1 is expelled from a nozzle 2a which comprises, for example, a droplet generator, in the form of a jet. Normally, this jet is divided into droplets having almost random dimensions and spacing, but in this case a vibration is imparted to the ink inside the nozzle cavity (not shown) at an ultrasonic frequency fixed, by means, for example, of a circuit (not shown) which excites a piezoelectric crystal contained in the droplet generator 2. The pressure waves cause the jet 1 to be divided into a series of droplets having dimensions and uniform spacing at well-determined distances from the outlet of the nozzle 2a. A typical droplet generator is described in the publication "IBM Technical Disclosure Bulletin", vol. 21, n ° 5, October 1978, pp. 1949-1950.

The application of a voltage to a charging electrode 4 which surrounds the point of formation of the droplets has the effect of imparting to each of the latter a charge of a predetermined value. Each droplet retains the charge which is thus imparted to it throughout the duration of its journey to a plate 30 on which is placed a sheet of paper or other printing medium.

The ink droplets then pass through an electric field generated by applying a high voltage of fixed value to a pair of deflection plates 11 and 12 arranged horizontally. The charge applied to each droplet having a determined value, any droplet can be deflected vertically by a desired distance. In the case of the IBM 6640 printer, the droplets are deflected vertically from bottom to top and form a column of dots on the paper. The droplets which are not used for the purposes of printing receive no charge and are intercepted by a gutter 6 and brought back to a pump 6d via a reservoir 6a, a filter 6b and a supply ink 6c. The pump 6d continuously supplies ink to the droplet generator 2. A conventional ink recirculation system for such a printer is described in US Pat. No. 3,929,071. Furthermore, since the importance the vertical deflection of a charged ink droplet and the height of its point of impact on the paper held by the plate 30 are directly a function of the time interval during which it remains between the deflection plates 11 and 12, it is necessary to precisely control the speed of the droplets. Several servo systems making it possible to control the speed of the droplets by controlling the pump so as to obtain the pressure required in the droplet generator 2 are described in patent US-A-3,787,882 and in French patent application FR-A -2 405 754, filed by the plaintiff on September 8, 1978.

The droplet generator 2, the charging electrode 4, the deflection plates 11 and 12, and the gutter 6 are mounted on a carriage 7 which is driven horizontally along a predetermined path, that is to say perpendicular to the plane of the sheet of paper on which Figure 1 is plotted, at a relatively constant speed during the printing operation. The droplets can thus be deposited in suitable locations inside a character-forming frame or a screen, so as to print the desired character or symbol. The carriage 7 is driven by a device 7a, such as a motor operating in direct current, under the control of electronic circuits (not shown). The device 7a and the electronic circuits used to drive the carriage are described in detail in European patent application EP-A-0010199 filed by the applicant on September 24, 1979. It will be noted that the electric field is practically perpendicular to the direction in which the carriage moves.

When the inkjet printer is in operation, it is essential that means be provided to indicate the position of the carriage at all times, so that the start of printing of each column can be determined and that the The charging electrode can receive the voltage required to cause an appropriate deflection of the ink droplets. On the other hand, means must equal ment be provided to determine the direction in which the carriage moves. In this regard, a detector 9, comprising a matrix 9a of elements which emit and receive light and a concave mirror 9b, is arranged on the carriage, the elements 9a and 9b being located on either side of a fixed reference network 9c which is mounted on the chassis of the machine. The network 9c makes it possible, in conjunction with the matrix and the mirror, to generate signals which are transmitted to the electronic circuits of the machine to apply a voltage to the charging electrode and to control the drive device 7a of the carriage 7 The detection method and device are described in more detail in European patent application EP-A-0 006 443 filed by the applicant on May 22, 1979. The detection circuits are also described in the European patent application EP-A-0006482 filed by the applicant on ¹ June 1979.

The network 9c consists of opaque and transparent parts which are offset by 90 ° relative to each other. The detection matrix comprises a pair of light sources and a pair of detectors, the light passing through the array being reflected by the mirror 9b and striking the detectors which, with the circuits associated with them, alternately generate a signal which , in conjunction with a counter, allows the transitions to be counted (opaque parts with transparent parts), and therefore indicates the absolute position of the carriage 7 at any point along its route.

According to the present invention, means are provided for modifying the electric field existing between the deflection electrodes 11 and 12 so as to allow horizontal printing as well as vertical printing. This modification of the electric field is carried out by causing a mechanical rotation of the electrodes, which then pass from the position indicated in FIG. 2, corresponding to the case of a horizontal (conventional) printing at the position represented in FIG. 3, used in the vertical printing.

In the preferred embodiment of the invention, the deflection electrodes 11 and 12 are mounted on a cylinder 13 having a central recess 13a inside which they are partially arranged. These electrodes have surfaces 11a and 12a arranged facing each other and which are preferably equidistant from the longitudinal axis of the nozzle 2a (see Figure 1). On the other hand, the charging electrode 4 can be placed inside the cylinder near the nozzle 2a or be mounted separately, depending on its configuration.

In order to obtain the desired modification of the position of the electrodes 11 and 12, the cylinder 13 is rotatably mounted in a sleeve 14a which is connected, by means, for example, of elements 15 and 16 acting as a support, to the carriage 7 The internal diameter of the sleeve 14a is such that it can receive the cylinder 13. The sleeve 14a can optionally be divided along the line 14b into two parts constituting an upper half 17 and a lower half 18. The upper half 17 can have at its periphery a slot 19 intended to receive, in the example shown, a rod 20, one of the ends of which is connected to the cylinder 13 and the opposite end of which is located outside the upper half 17 , ends with a handle 21.

Adjustable stops 22 and 23 can be arranged at the periphery of the upper half 17 so as to limit the displacement of the rod 20 in the slot 19 and to ensure correct positioning of the rod 20 and therefore of the cylinder 13 and the electrodes 11 and 12.

Although different means, for example solenoids or a drive mechanism comprising pinions and a rack, etc., can be used to move the sleeve and cause a rotation of the electric field, it will preferably be used, for the sake of simplicity , the means described above.

In the IBM 6640 printer, the deflection electrodes are fixed and occupy the position which is that of the electrodes 11 and 12 in FIG. 2. The circuits necessary to ensure the printing functions are described in the European patent application EP- A-0 013 296 filed by the applicant on October 12, 1979. A drive device (including the electronic circuits associated with it) corresponding to the electronic circuits of the IBM 6640 printer is described in detail in the patent application European EP-A-0 010199

To modify such a printer so that it can print horizontally (the deflection electrodes then being oriented as shown in Figure 2), but also vertically (the orientation of the electrodes being that shown in Figure 3), it is necessary that the platen of the printer is driven practically in the same way as the carriage 7 is driven by the device 7a. The platen drive device can take any conventional form, but it is essential that the electronic circuits of the printer make it possible to determine the position of the paper placed on the platen so that, for example, the starts and stops '' perform in such a way that functions for determining the end of the paper, the margin, positioning the first character, etc. are performed. To this end, the plate 30 may comprise a disc 31 which is connected to the shaft 32 of the printer and which may comprise a network of markers 33 identical to the network described in European patent application EP-A-0 006 441 , but which is here circular. Furthermore, the network 33 may include a detector 34 which is identical to that described in said European patent application EP-A-0 006 441 which comprises a matrix 35 of elements which emit and which receive light as well as a mirror 36 between which the disc 31 rotates. An appropriate discontinuity can therefore be provided in said network so as to serve as a starting point for the rotation of the plate, which is ensured by the drive device, which can be identical to that described in the above-mentioned European patent application EP-A00199. Although various other devices can be used to drive the carriage and the stage, the drive device described here is preferably used.

Reference will now be made to FIG. 4, on which is shown the cylinder 13 comprising the deflection electrodes 11 and 12 which occupy in the FIG. A position corresponding to a horizontal impression, the electric field then being oriented vertically and the printing of ink droplets also occur vertically. So that the execution of certain functions, such as carriage return, tabulation, spacing, rear spacing and normal exhaust, is performed for example under the control of a microprocessor of the type used in the IBM 6 system used in conjunction with an IBM printer 6640, has the effect of exciting either the carriage drive device, or the plate drive device, or even these two devices at the same time (for example, to shift a line so as to advance one step the plate in the case of a horizontal impression, or to pass from one column to the other in the case of a vertical impression), it is necessary to make a minor modification to the existing electronic circuits so that the either of these drives be put into operation during the printing operation. To this end, as shown in FIG. 4, the cylinder 13 can be provided with means making it possible to pass from the putting into service of the carriage driving device (in the case of horizontal printing) to that of the platen drive (in the case of vertical printing), or vice versa. In the present example, the means used for this purpose comprise a switch 40, the single pole 41 of which can pass from an upper contact 42 to a lower contact 43 and vice versa. When the switch is in its normal position, such as that shown in Figure 4, all signals related to the functions mentioned above can be applied to the carriage drive control circuit, however only when printing is done vertically , the pole 41 comes into contact with the element 43, thereby rendering the logic A associated with the carriage control circuit inoperative and putting into service the logic B associated with the circuit drive control circuit. Each of these two logics can comprise several AND gates with two inputs, the common inputs being respectively connected to contact 42 and to contact 43 of switch 40. Thus, when contact 42 is energized (see Figure 4), the first input of all the AND gates of logic A are at the high level, so that it is sufficient that a second entry of one or more of the AND gates corresponding to the functions of carriage return (RET. CH.), of tabulation (TAB. ), spacing (ESP.), rear spacing (ESP. REAR) and exhaust (ESCAPE) is energized so that a suitable output is applied to the carriage drive control circuit. The same goes for logic B when the contact 43 of the switch is energized, the output of the logic then being sufficient to energize the drive control circuit of the circuit board.

The switch 40 may be of the magnetic type and the cylinder 13 may include a magnet 44 so that, when the handle 21 is passed from the position corresponding to a horizontal impression to the position corresponding to a vertical impression (respectively shown on Figure 4 in solid and dotted lines), the magnet rotates counterclockwise and causes the pole 41 to pass from its first position to the second. It is thus possible to select one or the other of the logics A and B respectively associated with the drive of the carriage and that of the plate. The output lines 44 and 45 pertaining to the “carriage return” function are connected in a cross so that, when a “carriage return” signal is obtained on the corresponding line, the circuit for driving the plate can be energized, for example during a predetermined time interval to allow the platen to move to the position corresponding to the next printing line. Similarly, when the pole 41 is in contact with the element 43 and the printing occurs vertically, when a signal “return from the carriage is applied to the logic B and to the circuit for controlling the drive of the plate, a signal is also applied to the carriage drive control circuit so that the latter moves a predetermined distance along its horizontal path. A “carriage return” signal can thus be used to cause an offset or a displacement of the printing position independently of the printing mode.

Furthermore, given that, when the printing is carried out horizontally, the orientation of the electric field and of the sequences of droplets is vertical, and that, when the printing is carried out vertically, the orientation of the field and of the sequences of droplets is horizontal, it is necessary, when passing from one orientation to another, to shift by 90 ° the data transmitted to the charging electrode 4 of the printer and concerning the printing of a character forming part of a given assortment of block letters. Although this can be achieved by different methods, the simplest way to do this is to provide for the use of two switchable sets of characters. In the inkjet printer IBM 6640, the character selection and character matching signals are applied to a character generator 50 which transmits an address to an unalterable memory in which assorted characters are stored, and which receives from this memory data relating to the printing, column by column, of the desired character, this data then being transmitted to a logic for positioning the ink droplets 51, which generates digital data representing the voltage to be applied to the charging electrode 4 via a digital / analog converter 52. However, in the printer described here, a selection must be made at the level of the character sets so as to be able to transmit the required data, depending on whether the printing is done vertically or horizontally. For example, as shown in Figure 5, in which the letter H is printed in mode A and in mode B, when the carriage 7 moves horizontally and the ink droplets are printed vertically (mode A), that the assortment of characters A (associated with mode A) be chosen. In this regard, the magnetic switch may include a second pole 41a with which are associated a first contact 42a and a second contact 43a, which allows one or the other of said sets to be implemented depending on the position of the pole 41a. As before, the pole 41a a can be passed from contact 42a to contact 43a to select assortment A via an exclusive OR gate 53, or vice versa to select assortment B. It is therefore unnecessary to modify the electronic circuits of the printer for the purpose of selecting one or the other of the assortments of characters depending on whether the printing is to take place horizontally or vertically. Various methods can be used for the selection of character sets; for example, the method described in patent US Pat. No. 3,964,591 makes it possible to pass from one assortment to another by selecting different parts of the memory. In this regard, it will be noted that any method can be employed insofar as it makes it possible to select one or the other of the assortments of characters when switching from horizontal printing mode to vertical printing mode.

The character positioning logic can be of the type described in the above-mentioned European patent application EP-A-0013296. However, taking into account the relative speed at which the carriage 7 moves, or the speed of the paper when the printing takes place vertically, it may not be possible to employ the method described in the patent US-A- 4,086,601 to compensate for the aerodynamic effects to which the droplets may be subject or the interactions which may occur between the charged droplets. These difficulties can be avoided by using the suction device described in US-A-4,097,872.

A variant of the device of the present invention is shown in Figures 6 and 7. The different elements which, in these figures, are similar to those shown in Figures 1 to 5 have the same reference numbers. In this variant, the cylinder has been replaced by a carriage 60 comprising recesses 61 and 62 in which two pairs of deflection electrodes are respectively housed: 63, 64 and 65, 66. The carriage 60 can be mounted, for example, in a slide 67 in dovetail so as to allow the alignment of the recess 61 or 62 with the nozzle 2a for the purposes, respectively, of a horizontal impression or a vertical impression. In order to obtain a precise alignment of the nozzle 2a and the center of the recess 61 or 62, that is to say between the deflection electrodes 63, 64 or 65, 66, provision is made at the opposite ends of the slide of the stops 68 and 69 which limit the movement of the carriage between the positions which it must occupy for the purposes of a horizontal or vertical printing (see Figure 7). As shown in Figures 6 and 7, the movement of the carriage can be achieved, for example, by means of a handle 70 connected thereto.

It follows from the above that the device of the present invention makes it possible to modify the direction in which printing is carried out by an ink-jet printer by simply orienting the electric field in one of two mutually perpendicular directions which are practically perpendicular to the desired path of the ink droplets. On the other hand, the implementation of one or the other of the drive devices respectively associated with the carriage and the printing medium so that the orientation of the electric field is practically perpendicular to the direction in which the movement is carried out, allows printing to be carried out in the chosen direction.

Although the essential characteristics of the invention applied to a preferred embodiment of the invention have been described in the foregoing and represented in the drawings, it is obvious that a person skilled in the art can provide all of them. modifications of form or detail which it judges useful, within the framework defined by the claims.

Claims (13)

1. An ink jet printer, of the type which comprises :

a nozzle (2a) for issuing ink drops ;

a first electrode (4) for imposing a charge the ink drops in accordance with signals corresponding to characters or symbols to be printed ;

a print support (3d) upon which images can be formed which are representative of the signals corresponding to the charge imposed upon said ink drops, means (11, 12) for forming an electric field substantially perpendicular to the path of said ink drops, said electric field effecting deflection of said ink drops in accordance with the amplitudes of the charges upon saik ink drops ;

means (7, 7a) for deflecting relative movement between said nozzle (2a) and said print support (30) in at least a selected one of vertical and horizontal directions ;

a printer characterized in that it further includes means (13, 21, 40) coupled to said means for effecting relative movement between said nozzle and said print support for orientating said electric field orthogonally to the direction of the selected relative movement.

2. An ink jet printer in accordance with claim 1, characterized in that said means for forming said electric fields comprises a pair of deflection electrodes (11, 12) positionned on opposite sides of the streams of ink drops.

3. An ink jet printer in accordance with claim 2, characterized in that it includes a carrier (7) mounting said nozzle (2a), said first electrode (4) and the deflection electrodes (11, 12).

4. An ink jet printer in accordance with claim 3, characterized in that said means for orienting said field comprises a cylinder (13) defining a central bore (13a), said deflection electrodes (11, 12) being mounted within said bore.

5. An ink jet printer in accordance with claim 4, characterized in that it includes a pedestal (14a) connected to said carrier (7) said pedestal being mounted so as to permit rotational movement of said cylinder relative to said pedestal.

6. An ink jet printer in accordance with claim 5, characterized in that cylinder (13) comprises a handle (21) and means (22, 23) to limit the rotational movement of said cylinder.

7. An ink jet printer in accordance with claim 6, characterized in that said pedestal on said carrier includes a sleeve circum: scribing said cylinder (13), a radially extending slot (19) in said sleeve in order to receive said handle (21).

8. An ink jet printer in accordance with claim 7, characterized in that said means (22, 23) to limit rotational movement of said cylinder comprises adjustable stop means on said sleeve.

9. An ink jet printer in accordance with claim 3, characterized in that means for effecting relative movement comprises : carrier drive means (7a) for effecting movement of said carrier (7) in a path parallel to print support (30), and print support drive means (30) for effecting displacement of said print support in a path perpendicular to the path of movement of said carrier.

10. An ink jet printer in accordance with the claim 9, characterized in that in that it includes means for selecting, according to the orientation of said electric field, one or the other of said drive means.

11. An ink jet printer according to claim 10, characterized in that it includes at least two type font means, and it that it further includes means for selecting, according to the orientation of said electric field, on or the other of said type font means.

12. An ink jet printer in accordance with claim 3, characterized in that it includes a second pair of deflection electrodes (63, 64, 65, 66), mounting means on said carrier (60) and holding said first and second deflection electrode pairs in spaced apart relationship, said deflection pairs being positioned at substantially right angles to one another to form electric fields for orienting said electric field comprising means (67) for shifting said mounting means from a first position, where in the deflection electrodes of said first pair are positionned on opposite sides of the path of the stream of ink drops, to a second position wherein the deflection electrodes of said second pair are positioned on opposite sides of said path.

13. An ink jet printer in accordance with claim 12, characterized in that it includes stop means (68, 69) for limiting the movement of said mounting means between said first and second positions.

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