Ink barrier for Fluid reservoir vacuum or pressure line

IS 2 175 272 T3

DESCRIPTION

Ink barrier for vacuum or pressure pipe of the fluid reservoir.

This invention relates to barriers to prevent ink from leaking out of an ink reservoir to which a vacuum or pressure pipe is connected.

In many inkjet systems, an inkjet printhead contains a reservoir from which ink is supplied to pressure chambers to eject ink droplets through a series of holes in response to ejection signals. of the drops. As the ink in the tank is used, air is drawn into the tank through a ventilation duct. In addition, to prevent ink dripping through the ink jet holes to which the tank is connected, a slight negative pressure is normally applied to the tank vent duct and to expel the contaminated ink from the ink jet holes, a slight negative pressure is applied to the tank vent duct. applies positive pressure to the ventilation duct.

In certain cases, an ink jet print head must be arranged to operate in different orientations, for example, with the series of holes aligned in a generally horizontal direction and, ejecting the drops in a generally horizontal direction, or with the series of holes aligned in a generally vertical direction and oriented to eject drops horizontally, or with the series of the holes aligned in a generally horizontal direction and oriented to eject the drops vertically downward. However, in an inkjet print head adapted for use in such a variety of orientations, care must be taken to prevent ink from flowing into the reservoir vent duct or associated vacuum or pressure tubing, not only in each of the orientations during normal use, but also when the inkjet print head is completely inverted or shaken during handling.

In order to prevent the ink from reaching the tank ventilation duct, the patent by Yuki et al. No. 4,648,273 provides a passage through the labyrinth containing spaced barrier walls that lead to a chamber from which the ventilation duct opens to the atmosphere. In Deur et al patents No. 5,276,468 and 5,386,224, a U-shaped air path extends between an ink reservoir and a vent duct, for the purpose of retaining impurities from the air entering the vent duct before reaching the reservoir. The Cowger et al. No. 4,931,811 shows labyrinth and U-shaped spiral trajectories directed to isolate a liquid valve from the atmosphere and from an ink reservoir, respectively. In that patent, the U-shaped paths have a dimension small enough that the ink forms a complete meniscus across the cross section at any location on the path, so that the portion of the path that receives the ink is completely full of ink. Also, the path is long enough that any ink that has been drawn into the ink path will flow back into the ink jet reservoir when the reservoir pressure is reduced. However, none of the above techniques describe a reservoir arrangement to prevent ink from the reservoir from leaking through a ventilation duct or vacuum or pressure tubing connected to the reservoir when the print head was oriented in either of the reservoirs. three orthogonal orientations to each other.

Accordingly, it is an object of the present invention to provide an ink barrier for a vacuum or pressure pipe of a tank, which overcomes the drawbacks of the prior art.

Another object of the invention is to provide an ink barrier for a tank ventilation duct connected to a vacuum or pressure pipe, which allows the print head to be positioned in any of the three orthogonal orientations to each other, without allowing it to come off. the ink through the vacuum or pressure tubing.

These and other objects of the invention are achieved by providing a recording head having the features of claim 1 of the appended claims and an ink jet system as defined in claim 12 of the appended claims.

In the following description, a tube having the characteristics set forth in claim 1 is referred to as a U-shaped tube or tube in

OR.

In order to ensure that any ink that enters the open end of the U-tube when the reservoir is shaken or inverted during handling will not pass into the ventilation duct or the vacuum or pressure line, the internal diameter of the The path within the U-tube may advantageously be small enough to cause the ink to form a plug, preventing the passage of air. As a result, when ink is removed from the reservoir during inkjet head operation, the resulting reduction in air pressure within the reservoir will push back any ink that has entered the U-tube path and into the reservoir. .

In the attached drawings:

The objects and additional advantages of the invention will be obvious from reading the following description, in conjunction with the accompanying drawings in which:

Fig. 1 is a schematic view illustrating a representative embodiment of the ink jet recording head containing a tank with an ink barrier according to the invention;

Fig. 2 is a perspective side view of the ink jet recording head of Fig. 1 with a tank wall removed to illustrate the interior arrangement thereof; and Fig. 3 is an exploded perspective view of the arrangement shown in Fig. 2 illustrating the components that

ES 2 are assembled to produce the tank layout.

The inkjet tank of the present invention is intended for use in an inkjet printing system, as described in U.S. Patent No. 5,489,925, in which an inkjet printing head ink can be operated in any of three orientations orthogonal to each other. Such a topical inkjet system, shown in Fig. 1, includes a main control unit 10 containing a remote ink supply reservoir 12 which is connected via an ink supply conduit 14 on a cable 15 to an ink jet print head 16 and a control unit 18 of the pressure that is connected to the print head 16 by ink jet via an air duct 19, also carried by the cable 15. Furthermore, the main control unit 10 includes a temperature control unit 22 for controlling the temperature of the heat-melt ink in various portions of the ink jet system.

To facilitate the positioning of the print head 16 adjacent to the different types of objects to which the print is applied, the print head is movably supported on a vertically arranged column 24, so that it is closed by a clamp 26 in any position. desired vertical on the column. In addition, the print head 16 is supported for pivoting movement in any vertical plane by a universal connection 28 that can be clamped, so that the print head can be oriented to allow a linear series of ink jet holes 30. in oil, best seen in Fig. 2, to project the ink horizontally, either in a horizontal line or a vertical line, or downwards.

According to conventional practice, the hole line 30 was inclined at an angle with respect to the direction of movement of the objects to be imaged in order to increase the resolution of the image, that is, to decrease the spacing. of adjacent lones in the image. In the arrangement shown in the drawings, the objects to be printed pass in a generally horizontal direction with respect to the orientation of the print head 16 shown in Fig. 2, but the angular orientation of the print head may be varied to increase or decrease. decrease the resolution. However, when making such orientation adjustments, care must be taken to ensure that the open end 92 of the U-shaped tube discussed below is above the level of the ink in the reservoir.

In the arrangement illustrated in Fig. 1, the print head was arranged with the surface containing the holes 30 of the print head (shown in Fig. 2) in a horizontal orientation, as shown in continuous lines to cause the holes to project downward a trail of ink droplets 31 onto the upper surfaces 32 of a series of containers 34 that are conveyed in a horizontal direction by a conveyor 36 , thus allowing the appropriate information to be printed on the

272 T3 4 upper surface of each of the tanks. If desired, as shown in the dotted lines in Fig 1, the print head can be lowered onto the column 24 and the universal connection 28 can be arranged to clamp the head 16 in an orientation corresponding to that shown. in Fig. two but with the series of holes 30 facing the sides 37 close to the containers 34, in such a way as to cause the information to be printed on a near side of each of the tanks as it is transported by the conveyor 36 until it passes the storage head. impression.

In still another position of the print head, the printing system of the invention can be arranged to print a series of labels 38 carried on a belt 40 in a vertical direction from a reel 42 to another reel 44 by adjusting the universal connection 28 to join with Clamp the print head in a vertical orientation, as shown in the dotted outline in Figure 1, such that the series of holes 30 faces the labels 38 as they are conveyed in the vertical direction.

The ink supply reservoir 12 in the main control unit 10, which has a sealing cover 46, is arranged to receive a block 48 of solid heat-melt ink and has a thermostatically controlled heater 50, connected by a pipe 52 to the temperature control unit 22. The temperature control unit 22 is arranged to control the heater 50 so that it heats the melt ink block 48 sufficiently to melt it and to keep the ink in the supply reservoir 12 at a temperature just below. above its melting point, so that it is liquid enough that it can be transferred by pump 53 through supply conduit 14 to printhead 16 as required. At the same time, the temperature of the ink in the supply tank 12 is kept low enough so that no appreciable degradation takes place, even though the ink is continuously kept at this temperature for several days or weeks. Similarly, the ink supply conduit 14 contains a thermostatically controlled heater 54 connected via pipe 56 to the temperature control unit 22, so that the supply pipe is also continuously maintained in a liquid state, albeit at a temperature low enough that no appreciable degradation occurs.

As shown in Figures 2 and 3, the ink jet recording head 16 includes a housing 58 that contains a reservoir 60 in the form of an internal cavity 61 in the housing 58 that receives the ink through the supply conduit 14 for its replenishment when needed. As shown in Fig. 3, the supply conduit connects to a filter 62 inserted in an internal path 64 that communicates with the cavity 61 of the reservoir.

In order to heat the fusing ink by

ES 2 175 272 T3 heat contained in the tank, a heating element 66 received in a cylindrical cavity 67 in the housing is connected through the pipes 68 in the cable 15 to the temperature control unit 22 and, to avoid the overheating, A thermal fuse assembly 69 is provided connected via corresponding pipes 70 to the temperature control unit 22 to interrupt the supply of power to the heater 66 in the event of an overheating condition. The temperature of the ink in the print head is maintained at a determined level by a temperature sensing thermistor 71 connected via pipes 72 to the temperature control unit 22.

In order to detect a low ink condition in reservoir 60 and for that reason to initiate replenishment through line 14, a low ink sensor 74 is placed within reservoir cavity 61, as shown in Fig. Fig. 2, in a location so that it is covered with ink in any of the three mutually orthogonal orientations of the print head described above, until the volume of ink within the reservoir has been reduced to approximately one-half to one-third of its size. normal capacity. When these conditions occur, ink low sensor 74 sends a signal through corresponding lines 76 to pump 53 to transfer ink from supply reservoir 12 to reservoir 60 of the print head.

To transport ink from reservoir 60 to series of holes 30 in any of three mutually orthogonal orientations of printhead 16, reservoir 60 includes a triangular path 78 at one end of cavity 61 that leads to an outlet 80 arranged spaced relative to a lower corner of cavity 61. Path 78 communicates even with the corner of the reservoir cavity that was at the lowest level in any of the three print head orientations previously described with respect to Fig. 1. As seen in Fig. 2, The path 78 and the outlet 80 are in the lower right front portion of reservoir 60. The outlet 80 leads to a conduit 81 that carries ink to adjacent pressure chambers of the conventional type (not shown) associated with each of the holes 30 to cause the ink drops to be expelled therefrom in response to signal signals. ejecting the ink in the usual way.

Thus, when the print head was in the vertical orientation illustrated in Fig. 2 and facing the surface 37 of a package 34, as shown in the dotted lines in Fig. 1, the lower portions of the Path 78 and outlet 80 are in line with the bottom of the tank cavity 61. Also, when the print head was in the horizontal orientation shown with solid lines in Fig. 1, that is, with holes 30 facing the top of a package 34, path 78 and outlet 80 are also at a location corresponding to the bottom of reservoir cavity 61. Finally, when the print head is pivoted upward from the orientation shown in solid lines in Fig. 1 to face the labels 38 on the ribbon 40, as shown in the dotted lines in Fig. 1, path 78 and outlet 80 were located below the ink level in reservoir cavity 61.

As the ink is used during the operation of the print head, the ink level in the reservoir decreases and, as a result, air enters the reservoir through a vent 82 that was connected through line 19 to the pressure control unit 18 in the control unit 10. According to the invention, the ventilation duct 82 enters the reservoir cavity 61 at a location diametrically opposite to the triangular path 78 and to the outlet 80, that is, in the upper left rear part of the reservoir, as seen in the Fig. 2. Inside the tank cavity, the ventilation duct 82 was connected to the upper end of a section 84 of a U-shaped tube 86 which, as best seen in Fig. 3, consists of an upper portion with two parallel sections 84 and 88 and a lower portion 90 that connects to sections 84 and 88 and extends in a substantially horizontal direction. As shown in Fig. 2, the section 84 extends downwardly from the vent 82 along the rear wall of the reservoir cavity 61 and the lower portion 90 extends along the bottom wall of the reservoir cavity, that is that is, below the normal mononymous level of ink in the tank, while another span 88 extends upward along the rear wall adjacent span 84 with the end of span 88 having an end 92 that was open to the atmosphere within the reservoir.

When the print head reservoir 60 was in its normally full state after being filled with ink from the far ink supply reservoir 12, the ink level was below the open end 92 of the U-shaped tube at each point. one of the three print head orientations described above, such that the ink was not caused to enter the open end 92 of the U-shaped tube during normal operation in either of these orientations. As mentioned above, if the angular position of the print head is changed to vary the angle of the hole line 30 with respect to the direction of movement of the objects to be printed, the maximum ink level of the printhead should be controlled. reservoir so that it is below the open end 92 of the U-shaped tube.

However, it is possible that the print head may be turned during handling or adjustment so that the open end of the U-shaped tube is below the ink level or that the reservoir may be agitated so that the ink enters the open end of the U-shaped tube. In order to prevent ink entering the U-shaped tube from entering the vacuum and pressure pipe 19 connected to the ventilation duct 82, the internal diameter

ES 2 175 272 T3 of the path in the U-shaped tube is made small enough, that is, less than about 3 mm in diameter, to cause the ink to form a plug, preventing the passage of air. In this way, when operation of the print head forces the ink out of the reservoir 60, the resulting pressure reduction in the reservoir air gap will push the ink out of the open end 92 of the U-tube and back inside. of the deposit.

In addition, the length of the U-shaped tube is made long enough so that if the tilt or reversal of the print head causes the open end 92 of the U-shaped tube to fall below the ink level of the reservoir, the lower end 90 of the U-shaped tube that joins the lengths 84 and 88 was at the same time at least partially above the ink level of the reservoir. This produces a differential pressure that tends to prevent the ink from passing further into the tube and prevents the transfer of the ink from the reservoir into the ventilation duct and associated pressure or vacuum piping.

In a topical reservoir arrangement according to the invention, reservoir 60 has a cavity 61 that is approximately 4.5 cm high, 2.5 cm wide, and 2.5 cm deep and a triangular path 78 that is approximately 2.5 cm long, 2 cm high at the long end and 0.3 cm wide. In this case, the normal reservoir capacity is approximately 30cc and the ink low sensor 74 was positioned to indicate a low ink condition with approximately 10-15cc of ink remaining in the reservoir in each of the three orientations described. previously. Also, with the triangular path 78 and the tank outlet 80 at the location described above, the volume of ink remaining in the tank can be reduced to about 10% of its normal capacity, that is, about 3 cc, before it is air could enter the duct leading to the ink ejection holes 30.