Patent Description:
Some type of ink used in the ink-jet printing apparatus causes a precipitate easily as a result of agglomeration of a component in the ink. For example, ink of a watercolor pigment type to agglomerate easily is used as ink for flexible packaging.

In the ink-jet printing apparatus, the ink touches outside air at a nozzle provided at a head. Hence, at a nozzle not used for printing, agglomeration is caused easily as a result of evaporation of a solvent. In response to this, a circulation system of supplying ink to a head and collecting the ink from the head is employed, thereby reducing remaining of the ink in the head to suppress agglomeration at a nozzle. A printing apparatus employing the circulation system is described in <CIT>, for example.

Document <CIT> discloses a recording head which is inclined with respect to the horizontal direction in order to extract air bubbles which accumulate in the upper part of the ink recording head.

The printing apparatus described in <CIT> includes a horizontal reservoir (horizontal tank <NUM>) provided over heads arranged in a horizontal direction and from which ink is supplied to the heads, and a vertical reservoir (vertical tank <NUM>) communicably connected to the horizontal reservoir and extending longer in a top-bottom direction than the horizontal reservoir. The horizontal reservoir is filled with the ink. A gas layer is formed at the top of the vertical reservoir.

In the above-described configuration, slight agglomeration of the ink is accumulated with passage of time to form a precipitate of the agglomeration on the bottom of each of the horizontal reservoir and the vertical reservoir. This precipitate is desirably removed in order to prevent the precipitate from entering the head.

The present invention has been made in view of the foregoing circumstances, and is intended to provide a technique allowing a precipitate in a reservoir to be efficiently prevented from entering a head.

To solve the above-described problem, a first aspect of the present invention is intended for an ink supplier that supplies ink to a plurality of heads in an ink-jet printing apparatus, comprising: a supply reservoir storing the ink to be supplied to the plurality of heads; and a discharge pipe having a pump and used for discharging the ink from the supply reservoir. The supply reservoir includes: a first horizontal reservoir having a cylindrical shape extending in a direction of alignment of the plurality of heads, and having a plurality of supply ports each communicating with one of the plurality of heads; and a first vertical reservoir having a side surface provided with a first opening directly or indirectly communicating with one end of the first horizontal reservoir, and having a cylindrical shape with a closed bottom larger in a top-bottom direction than the first horizontal reservoir. The first horizontal reservoir has a bottom surface that is tilted from a horizontal direction at an angle of tilt equal to or greater than <NUM>° in such a manner as to extend downward from the one end toward the other end. The first horizontal reservoir includes a first discharge port provided at a bottom portion of the first horizontal reservoir at the other end and communicably connected to the discharge pipe.

According to a second aspect of the present invention, in the ink supplier according to the first aspect, the first vertical reservoir includes a second discharge port provided at a lowermost point at a bottom portion of the first vertical reservoir and communicably connected to the discharge pipe.

According to a third aspect of the present invention, in the ink supplier according to the second aspect, the first vertical reservoir has a bottom surface of a planar shape, the bottom surface of the first vertical reservoir is tilted from the horizontal direction at an angle of tilt equal to or greater than <NUM>° in such a manner as to extend upward with distance from the first horizontal reservoir, and the second discharge port is provided at a bottom portion of the first vertical reservoir at an end adjacent to the first horizontal reservoir.

According to a fourth aspect of the present invention, in the ink supplier according to the first aspect, the ink supplier supplies ink to a plurality of heads in an ink-jet printing apparatus. The ink supplier further comprises a collection reservoir storing the ink collected from the plurality of heads. The collection reservoir includes: a second horizontal reservoir having a cylindrical shape extending in the direction of alignment of the plurality of heads, and having a plurality of collection ports each communicating with one of the plurality of heads; and a second vertical reservoir having a side surface provided with a second opening directly or indirectly communicating with one end of the second horizontal reservoir, and having a cylindrical shape with a closed bottom larger in the top-bottom direction than the second horizontal reservoir. The second horizontal reservoir has a bottom surface that is tilted from the horizontal direction at an angle of tilt equal to or greater than <NUM>° in such a manner as to extend downward from the one end toward the other end. The second horizontal reservoir includes a third discharge port provided at a bottom portion of the second horizontal reservoir at the other end and communicably connected to the discharge pipe.

According to a fifth aspect of the present invention, in the ink supplier according to the fourth aspect, the second vertical reservoir includes a fourth discharge port provided at a lowermost point at a bottom portion of the second vertical reservoir and communicably connected to the discharge pipe.

According to a sixth aspect of the present invention, in the ink supplier according to the fifth aspect, the second vertical reservoir has a bottom surface of a planar shape, the bottom surface of the second vertical reservoir is tilted from the horizontal direction at an angle of tilt equal to or greater than <NUM>° in such a manner as to extend upward with distance from the second horizontal reservoir, and the fourth discharge port is provided at a bottom portion of the second vertical reservoir at an end adjacent to the second horizontal reservoir.

According to an seventh aspect of the present invention, in the ink supplier according to any one of the fourth to sixth aspects, each of the plurality of collection ports includes a second cylindrical part forming communication by penetrating the bottom surface of the second horizontal reservoir from top to bottom, the second cylindrical part has an upper end located above the bottom surface of the second horizontal reservoir, and the second cylindrical part has a lower end communicably connected to a pipe coupled the head.

According to a eighth aspect of the present invention, in the ink supplier according to any one of the first to seventh aspects, each of the plurality of supply ports includes a first cylindrical part forming communication by penetrating the bottom surface of the first horizontal reservoir from top to bottom, the first cylindrical part has an upper end located above the bottom surface of the first horizontal reservoir, and the first cylindrical part has a lower end communicably connected to a pipe coupled the head.

According to the first to eighth aspects of the present invention, tilting the bottom surface of the first horizontal reservoir forms a lowermost point at an end of the bottom surface of the first horizontal reservoir. A precipitate in the first horizontal reservoir moves along the tilted bottom surface and gathers at this lowermost point. Providing the discharge port at the lowermost point allows the precipitate in the first horizontal reservoir to be discharged efficiently.

In particular, according to the second and third aspects of the present invention, the first vertical reservoir is also provided with the discharge port at the lowermost point. This allows a precipitate in the first vertical reservoir to be discharged efficiently.

In particular, according to the fourth aspect of the present invention, it is possible to discharge a precipitate in the second horizontal reservoir efficiently like in the first horizontal reservoir.

In particular, according to the fifth and sixth aspects of the present invention, the second vertical reservoir is also provided with the discharge port at the lowermost point. This allows a precipitate in the second vertical reservoir to be discharged efficiently.

In particular, according to the seventh aspect of the present invention, it is possible to reduce a likelihood that a precipitate to move along the bottom surface of the first horizontal reservoir will enter the supply port. Thus, a likelihood of entry of the precipitate into the head through the supply port can be reduced.

In particular, according to the eighth aspect of the present invention, it is possible to reduce a likelihood that a precipitate to move along the bottom surface of the second horizontal reservoir will enter the collection port. Thus, a likelihood of entry of the precipitate into the head through the collection port can be reduced.

A preferred embodiment of the present invention will be described below by referring to the drawings.

A printing apparatus <NUM> including an ink supplier <NUM> according to one preferred embodiment of the present invention will be described below by referring to <FIG> is a schematic view of the printing apparatus <NUM>. The printing apparatus <NUM> performs a coating process, a printing process, and a drying process on an elongated strip-shaped printing medium M while conveying the printing medium M by causing a controller <NUM> to control each part of the apparatus.

More specifically, the printing apparatus <NUM> is a printing apparatus that ejects ink of a watercolor pigment type in an ink-jet method to an elongated strip-shaped film sheet for flexible packaging. The printing medium M is composed of a film made of orientated polypropylene (OPP) or polyethylene terephthalate (PET), for example. However, the material of the printing medium M is not limited to a resin film but may be a different material such as paper. The printing medium M has two surfaces including a front surface on which an image is to be printed and a back surface on the opposite side to the front surface.

The printing apparatus <NUM> includes a conveyance mechanism <NUM>, a coating processor <NUM>, a printing processor <NUM>, and a drying processor <NUM>.

The conveyance mechanism <NUM> is a mechanism for conveying the printing medium M along a predetermined conveyance path. The conveyance mechanism <NUM> includes a feed roller <NUM>, a take-up roller <NUM>, and a large number of other conveyance rollers <NUM>. The feed roller <NUM>, the take-up roller <NUM>, and some of the conveyance rollers <NUM> are rotating rollers that are caused to rotate by a motor, for example. Some of the other conveyance rollers <NUM> are driven rollers that are caused to rotate in response to the motion of the printing medium M.

When the printing apparatus <NUM> is driven, the feed roller <NUM>, the take-up roller <NUM>, and the rotating rollers as some of the conveyance rollers <NUM> rotate. Thereby, the printing medium M is unwound from the feed roller <NUM>, subjected to the coating process by the coating processor <NUM>, the printing process by the printing processor <NUM> and the drying process by the drying processor <NUM>, and then is wound onto the take-up roller <NUM>. In <FIG>, arrows indicating a conveyance direction are given to the front surface of the printing medium M.

The coating processor <NUM> is a unit for coating the front surface of the printing medium M with a liquid primer (coating liquid). The coating processor <NUM> includes a pan <NUM> and gravure roller <NUM>. The pan <NUM> stores the liquid primer. The gravure roller <NUM> is a roller for coating the front surface of the printing medium M conveyed by the conveyance mechanism <NUM> with the primer. The gravure roller <NUM> is arranged in such a manner as to be partially dipped in the primer stored in the pan <NUM>.

The gravure roller <NUM> rotates relative to the printing medium M conveyed with the front surface placed on a lower side while holding the primer on an outer peripheral surface of the gravure roller <NUM>, thereby coating the front surface of the printing medium M with the primer. A direction of travel of the printing medium M and a direction of the rotation of the gravure roller <NUM> (indicated by an arrow in <FIG>) are opposite to each other. Specifically, the gravure roller <NUM> coats the front surface of the printing medium M with the primer in a so-called reverse kiss method.

The printing processor <NUM> includes a housing <NUM>, a color printing unit <NUM>, and a white printing unit <NUM>. The color printing unit <NUM> and the white printing unit <NUM> are arranged in the housing <NUM>. The color printing unit <NUM> ejects inks of a plurality of colors from above to the printing medium M conveyed with the front surface placed on an upper side. According to the present preferred embodiment, the color printing unit <NUM> has four head units <NUM> from which inks of respective colors are ejected. The inks ejected at the color printing unit <NUM> are inks of cyan, magenta, yellow, and black, for example. The white printing unit <NUM> ejects a white ink from above to the printing medium M conveyed with the front surface placed on an upper side. The white printing unit <NUM> has one head unit <NUM> from which an ink of white is ejected.

A detailed configuration of the head unit <NUM> and that of the ink supplier <NUM> for supplying ink to a plurality of heads <NUM> of the head unit <NUM> will be described later.

The printing processor <NUM> further includes a preliminary drying unit (not shown in the drawings) provided downstream from the color printing unit <NUM> and upstream from the white printing unit <NUM>, and a preliminary drying unit (not shown in the drawings) provided downstream from the white printing unit <NUM>. These drying units are used for drying ink ejected to the front surface of the printing medium M.

The drying processor <NUM> is a unit for drying the ink ejected to the front surface of the printing medium M at the printing processor <NUM>. The drying processor <NUM> includes a drying furnace <NUM> as a housing. In the drying furnace <NUM>, the conveyance mechanism <NUM> forms an S-shape conveyance path for the printing medium M. The conveyance mechanism <NUM> includes air turn bars <NUM> instead of the conveyance roller <NUM> provided at positions to touch the front surface of the printing medium M in the drying furnace <NUM>.

The controller <NUM> is composed of a computer including a processor such as a CPU, a memory such as a RAM, and a storage part such as a hard disk drive, for example. The printing apparatus <NUM> controls the operations of the conveyance mechanism <NUM>, the coating processor <NUM>, the printing processor <NUM>, and the drying processor <NUM> described above, and the operation of each part of the ink supplier <NUM> described later according to a computer program. By doing so, the printing process proceeds in the printing apparatus <NUM>.

The configuration of the ink supplier <NUM> for supplying ink to the plurality of heads <NUM> of the head unit <NUM> will be described next by referring to <FIG>.

As shown in <FIG>, the head unit <NUM> includes the plurality of heads <NUM> aligned in a horizontal direction (a direction perpendicular to the plane of paper of <FIG>). In <FIG>, heads <NUM> indicated by dashed lines connected to a collection reservoir <NUM> are the same as heads <NUM> indicated by solid lines connected to a supply reservoir <NUM>. In terms of the layout of the drawing, these heads <NUM> are illustrated twice.

The ink supplier <NUM> includes the supply reservoir <NUM> and the collection reservoir <NUM> of the head unit <NUM>, a drum tank <NUM>, and a buffer tank <NUM> that function as storages of the ink. The ink supplier <NUM> includes a first transport unit <NUM>, a second transport unit <NUM>, a third transport unit <NUM>, and a fourth transport unit <NUM> that function as means of transporting the ink between corresponding storages.

The head unit <NUM> includes the plurality of heads <NUM>, the supply reservoir <NUM>, and the collection reservoir <NUM>. Each of the heads <NUM> has a plurality of ejection nozzles provided at a surface of the bottom of the head <NUM> for ejecting the ink to the printing medium M.

The supply reservoir <NUM> is an ink storage storing the ink to be supplied to the head <NUM>. The supply reservoir <NUM> includes a first horizontal reservoir <NUM> and a first vertical reservoir <NUM>.

The first horizontal reservoir <NUM> is a cylindrical storage extending substantially horizontally in the direction of the alignment of the plurality of heads <NUM>. The first horizontal reservoir <NUM> has one end communicably connected to the first vertical reservoir <NUM>. The first horizontal reservoir <NUM> is closed at the other end. The first horizontal reservoir <NUM> has a bottom provided with a plurality of supply ports <NUM> forming communication between the inside and outside of the first horizontal reservoir <NUM> in a top-bottom direction. Each of the supply ports <NUM> is communicably connected through a supply pipe <NUM> to the head <NUM> arranged below the supply port <NUM>.

The first vertical reservoir <NUM> is a cylindrical storage with a covered top and a closed bottom. The first vertical reservoir <NUM> is larger in the top-bottom direction than the first horizontal reservoir <NUM>. The first vertical reservoir <NUM> has a side surface where a first opening <NUM> directly communicating with the one end of the first horizontal reservoir <NUM> is provided.

The first vertical reservoir <NUM> includes a level sensor <NUM>. A detection signal from the level sensor <NUM> allows the controller <NUM> to determine the amount of the ink stored in the supply reservoir <NUM>. The level sensor <NUM> may be a floating level sensor or a level sensor of a different type.

At the supply reservoir <NUM>, the first horizontal reservoir <NUM> is filled with the ink and the amount of the ink stored in the first vertical reservoir <NUM> is adjusted in such a manner as to form a gas layer of a certain extent at the top of the first vertical reservoir <NUM>. The gas layer in the first vertical reservoir <NUM> is connected to a pressure adjuster <NUM>. By doing so, a pressure in the first vertical reservoir <NUM> is kept at a predetermined negative pressure for supply reservoir.

The collection reservoir <NUM> is an ink storage storing the ink collected from the head <NUM>. The collection reservoir <NUM> includes a second horizontal reservoir <NUM> and a second vertical reservoir <NUM>.

The second horizontal reservoir <NUM> is a cylindrical storage extending substantially horizontally in the direction of alignment of the plurality of heads <NUM>. The second horizontal reservoir <NUM> has one end communicably connected to the second vertical reservoir <NUM>. The second horizontal reservoir <NUM> is closed at the other end. The second horizontal reservoir <NUM> has a bottom provided with a plurality of collection ports <NUM> forming communication between the inside and outside of the second horizontal reservoir <NUM> in the top-bottom direction. Each of the collection ports <NUM> is communicably connected through a collection pipe <NUM> to the head <NUM> arranged below the collection port <NUM>.

The second vertical reservoir <NUM> is a cylindrical storage with a covered top and a closed bottom. The second vertical reservoir <NUM> is larger in the top-bottom direction than the second horizontal reservoir <NUM>. The second vertical reservoir <NUM> has a side surface where a second opening <NUM> directly communicating with the one end of the second horizontal reservoir <NUM> is provided.

The second vertical reservoir <NUM> includes a level sensor <NUM>. A detection signal from the level sensor <NUM> allows the controller <NUM> to determine the amount of the ink stored in the collection reservoir <NUM>. The level sensor <NUM> may be a floating level sensor or a level sensor of a different type.

At the collection reservoir <NUM>, the second horizontal reservoir <NUM> is filled with the ink and the amount of the ink stored in the second vertical reservoir <NUM> is adjusted in such a manner as to form a gas layer of a certain extent at the top of the second vertical reservoir <NUM>. The gas layer in the second vertical reservoir <NUM> is connected to a pressure adjuster <NUM>. By doing so, a pressure in the second vertical reservoir <NUM> is kept at a predetermined negative pressure for collection reservoir. The negative pressure for collection reservoir is a pressure smaller than the negative pressure for supply reservoir. Specifically, a difference between atmospheric pressure and the negative pressure for collection reservoir is larger than a difference between atmospheric pressure and the negative pressure for supply reservoir.

The drum tank <NUM> is an ink storage having a maximum capacity for ink storage. The ink is supplied from the drum tank <NUM> to the supply reservoir <NUM> and the collection reservoir <NUM> in the head unit <NUM> through the buffer tank <NUM>.

The buffer tank <NUM> stores the ink temporarily. The buffer tank <NUM> has a capacity for ink storage less than that of the drum tank <NUM> and greater than those of the supply reservoir <NUM> and the collection reservoir <NUM>. The drum tank <NUM> and the buffer tank <NUM> are arranged in areas separate from the head unit <NUM>.

The buffer tank <NUM> is provided with a temperature sensor <NUM>, a heater <NUM>, a level sensor <NUM>, and an agitating unit <NUM>.

The temperature sensor <NUM> detects the temperature of the ink stored in the buffer tank <NUM>. The heater <NUM> is attached to an outer wall of the buffer tank <NUM> and heats the ink in the buffer tank <NUM>. The controller <NUM> controls the heater <NUM> on the basis of the temperature of the ink detected by the temperature sensor <NUM>.

The level sensor <NUM> detects the height of the ink stored in the buffer tank <NUM>, and outputs result of the detection to the controller <NUM>. The agitating unit <NUM> agitates the ink stored in the buffer tank <NUM> to prevent non-uniformity of heating and non-uniformity of concentration.

The first transport unit <NUM> transports the ink from the drum tank <NUM> to the buffer tank <NUM>. The first transport unit <NUM> includes a pipe <NUM>, and a valve <NUM>, a pump <NUM>, and a valve <NUM> interposed in the pipe <NUM>. The pipe <NUM> has one end placed in an ink storage region in the drum tank <NUM>. The pipe <NUM> has the other end communicating with the inside of the buffer tank <NUM>. The valves <NUM> and <NUM> are opened and the pump <NUM> is actuated by the controller <NUM>, thereby feeding the ink stored in the drum tank <NUM> to the buffer tank <NUM> through the pipe <NUM>.

The second transport unit <NUM> transports the ink from the buffer tank <NUM> to the collection reservoir <NUM>. The second transport unit <NUM> includes a pipe <NUM>, and a pump <NUM>, a filter <NUM>, a degassing unit <NUM>, and a valve <NUM> interposed in the pipe <NUM>. The pipe <NUM> has one end placed in an ink storage region in the buffer tank <NUM>. The pipe <NUM> has the other end communicating with the inside of the second vertical reservoir <NUM> of the collection reservoir <NUM>. The filter <NUM> removes a solid component (agglomeration, precipitate) from the ink. The degassing unit <NUM> removes air bubbles from the ink or part of a gas component dissolving in the ink. The valve <NUM> is opened and the pump <NUM> is actuated by the controller <NUM>, thereby feeding the ink stored in the buffer tank <NUM> to the second vertical reservoir <NUM> through the pipe <NUM>.

The third transport unit <NUM> transports the ink from the collection reservoir <NUM> to the supply reservoir <NUM>. The third transport unit <NUM> includes a pipe <NUM>, and a pump <NUM>, a filter <NUM>, and a degassing unit <NUM> interposed in the pipe <NUM>. The pipe <NUM> has one end placed in an ink storage region in the second vertical reservoir <NUM> of the collection reservoir <NUM>. The pipe <NUM> has the other end communicating with the inside of the first vertical reservoir <NUM> of the supply reservoir <NUM>. The filter <NUM> removes a solid component (agglomeration, precipitate) from the ink. The degassing unit <NUM> removes air bubbles from the ink or part of a gas component dissolving in the ink. The pump <NUM> is actuated by the controller <NUM>, thereby feeding the ink stored in the second vertical reservoir <NUM> of the collection reservoir <NUM> to the first vertical reservoir <NUM> of the supply reservoir <NUM> through the pipe <NUM>.

The fourth transport unit <NUM> transports the ink from the supply reservoir <NUM> to the buffer tank <NUM>. The fourth transport unit <NUM> includes a pipe <NUM>, and a valve <NUM> and a pump <NUM> interposed in the pipe <NUM>. The pipe <NUM> has one end placed in an ink storage region in the first vertical reservoir <NUM> of the supply reservoir <NUM>. The pipe <NUM> has the other end communicating with the inside of the buffer tank <NUM>. The pump <NUM> is actuated by the controller <NUM>, thereby feeding the ink stored in the first vertical reservoir <NUM> of the supply reservoir <NUM> to the buffer tank <NUM> through the pipe <NUM>.

With the configuration described above, a circulation path for the ink is formed by the supply reservoir <NUM>, the plural sets of supply pipe <NUM>, the head <NUM> and the collection pipe <NUM>, the collection reservoir <NUM>, and the third transport unit <NUM>. By driving the pump <NUM> of the third transport unit <NUM>, the ink is supplied from the second vertical reservoir <NUM> of the collection reservoir <NUM> into the first vertical reservoir <NUM> of the supply reservoir <NUM>. This generates a flow of the ink flowing from the first vertical reservoir <NUM> and returning to the second vertical reservoir <NUM> through the first horizontal reservoir <NUM>, the plural sets of supply pipe <NUM>, the head <NUM> and the collection pipe <NUM>, and the second horizontal reservoir <NUM> of the collection reservoir <NUM>. This ink circulation path is called an "in-head-unit circulation.

As described above, the negative pressure for collection reservoir is a pressure smaller than the negative pressure for supply reservoir. Specifically, a pressure in the second horizontal reservoir <NUM> of the collection reservoir <NUM> is smaller than a pressure in the first horizontal reservoir <NUM> of the supply reservoir <NUM>. Thus, a pressure in the second horizontal reservoir <NUM> communicating with the collection pipe <NUM> is smaller than a pressure in the first horizontal reservoir <NUM> communicating with the supply pipe <NUM> for each of the heads <NUM>, thereby generating a flow of the ink in the head <NUM> from the supply pipe <NUM> toward the collection pipe <NUM>.

A circulation path for the ink is formed by the buffer tank <NUM>, the second transport unit <NUM>, the collection reservoir <NUM>, the third transport unit <NUM>, the supply reservoir <NUM>, and the fourth transport unit <NUM>. Transporting the ink simultaneously through the second transport unit <NUM>, the third transport unit <NUM>, and the fourth transport unit <NUM> generates a flow of the ink flowing from the buffer tank <NUM> and returning to the buffer tank <NUM> through the second transport unit <NUM>, the collection reservoir <NUM>, the third transport unit <NUM>, the supply reservoir <NUM>, and the fourth transport unit <NUM>. This ink circulation path is called an "out-of-head-unit circulation.

If the ink is ejected from the head <NUM> and the ink in the supply reservoir <NUM> is reduced in a printing step or a maintenance step of the head <NUM>, an ink liquid surface in the first vertical reservoir <NUM> is lowered. In this case, the controller <NUM> recognizes reduction in the liquid surface level in the first vertical reservoir <NUM> using a detection signal from the level sensor <NUM>. Then, the controller <NUM> starts to transport the ink through the second transport unit <NUM> and the third transport unit <NUM> in such a manner that a liquid surface level detected by each of the level sensor <NUM> and the level sensor <NUM> falls within a predetermined range. If transport of the ink is already started through the in-head-unit circulation or the out-of-head-unit circulation, the controller <NUM> increases the amount of the ink to be transported through each of the second transport unit <NUM> and the third transport unit <NUM>.

If the ink in the buffer tank <NUM> is reduced by supply of the ink from the buffer tank <NUM> to the head unit <NUM>, an ink liquid surface in the buffer tank <NUM> is lowered. In this case, the controller <NUM> recognizes reduction in the liquid surface level in the buffer tank <NUM> using a detection signal from the level sensor <NUM>. Then, the controller <NUM> transports the ink through the first transport unit <NUM> in such a manner that a liquid surface level detected by the level sensor <NUM> falls within a predetermined range.

Removal of air bubbles and precipitates in the supply reservoir <NUM> and the collection reservoir <NUM> will be described next by referring to <FIG>. <FIG> is a perspective view of the head unit <NUM>. <FIG> is a side view of the head unit <NUM>. Some structures are omitted from the illustrations in <FIG> and <FIG>. <FIG> is a conceptual view showing the behaviors of air bubbles and precipitates in the supply reservoir <NUM>. <FIG> is a conceptual view showing the behaviors of air bubbles and precipitates in the collection reservoir <NUM>.

<FIG> is a perspective sectional view showing a part of the head unit <NUM>. More specifically, <FIG> shows the heads <NUM>, the supply pipes <NUM>, the collection pipe <NUM>, the supply reservoir <NUM>, and the collection reservoir <NUM> of the head unit <NUM>. <FIG> is a perspective view showing a part of the head unit <NUM>. More specifically, <FIG> shows the supply reservoir <NUM>, the collection reservoir <NUM>, and a discharge unit <NUM>.

As shown in <FIG>, <FIG>, and <FIG>, the first horizontal reservoir <NUM> of the present preferred embodiment has a circular cylindrical shape having a circular section. The sectional shape of the first horizontal reservoir <NUM> is a circle maintaining a constant shape from one end 51a connected to the first vertical reservoir <NUM> to the closed other end 51b. Specifically, the first horizontal reservoir <NUM> has a circular cylindrical shape closed at the other end. Thus, a top surface (an internal upper surface) and a bottom surface (an internal lower surface) of the first horizontal reservoir <NUM> are parallel to each other.

Like the first horizontal reservoir <NUM>, the second horizontal reservoir <NUM> of the present preferred embodiment has a circular cylindrical shape having a circular section. The sectional shape of the second horizontal reservoir <NUM> is a circle maintaining a constant shape from one end 61a connected to the second vertical reservoir <NUM> to the closed other end 61b. Specifically, the second horizontal reservoir <NUM> has a circular cylindrical shape closed at the other end. Thus, a top surface (an internal upper surface) and a bottom surface (an internal lower surface) of the second horizontal reservoir <NUM> are parallel to each other.

The first vertical reservoir <NUM> and the second vertical reservoir <NUM> of the present preferred embodiment are housed in a housing <NUM> of a rectangular parallelepiped shape. As conceptually shown in <FIG>, the first vertical reservoir <NUM> is a square cylindrical shape with a covered top and a closed bottom, namely, a rectangular parallelepiped shape. The first vertical reservoir <NUM> has a bottom surface having a planar shape and being parallel to a bottom surface of the housing <NUM>. As conceptually shown in <FIG>, the second vertical reservoir <NUM> is a square cylindrical shape with a covered top and a closed bottom, namely, a rectangular parallelepiped shape. The second vertical reservoir <NUM> has a bottom surface having a planar shape and being parallel to the bottom surface of the housing <NUM>.

As shown exaggeratingly in <FIG>, <FIG>, and <FIG>, the supply reservoir <NUM> and the collection reservoir <NUM> are tilted from the direction of the alignment of the heads <NUM> (namely, the horizontal direction). This tilts the top surface and the bottom surface of the first horizontal reservoir <NUM>, the bottom surface of the first vertical reservoir <NUM>, the top surface and the bottom surface of the second horizontal reservoir <NUM>, and the bottom surface of the second vertical reservoir <NUM> from the horizontal direction.

More specifically, in a range from the closed other end 51b to the one end 51a connected to the first vertical reservoir <NUM> through the first opening <NUM>, the top surface and the bottom surface of the first horizontal reservoir <NUM> are tilted in such a manner as to extend upward from the other end 51b toward the one end 51a.

In a range from the closed other end 61b to the one end 61a connected to the second vertical reservoir <NUM> through the second opening <NUM>, the top surface and the bottom surface of the second horizontal reservoir <NUM> are tilted in such a manner as to extend upward from the other end 61b toward the one end 61a.

The bottom surface of the first vertical reservoir <NUM> is parallel to the bottom surface of the first horizontal reservoir <NUM>. Specifically, the bottom surface of the first vertical reservoir <NUM> is tilted from the horizontal direction. Likewise, the bottom surface of the second vertical reservoir <NUM> is parallel to the bottom surface of the second horizontal reservoir <NUM>. Specifically, the bottom surface of the second vertical reservoir <NUM> is tilted from the horizontal direction.

As described above, the top surface of the first horizontal reservoir <NUM> is tilted in such a manner as to extend upward toward the one end 51a. Thus, as conceptually shown in <FIG>, if air bubbles B are generated in or mixed into the first horizontal reservoir <NUM>, the air bubbles B move toward the one end 51a along the top surface. Then, the air bubbles B move into the first vertical reservoir <NUM> through the first opening <NUM> and are absorbed in the gas layer at the top of the first vertical reservoir <NUM>. By doing so, it becomes possible to remove the air bubbles B from the inside of the first horizontal reservoir <NUM> without providing a pipe for removal of air bubbles to the first horizontal reservoir <NUM> that might be a cause for agglomeration.

Likewise, the top surface of the second horizontal reservoir <NUM> is tilted in such a manner as to extend upward toward the one end 61a. Thus, as conceptually shown in <FIG>, if air bubbles B are generated in or mixed into the second horizontal reservoir <NUM>, the air bubbles B move toward the one end 61a along the top surface. Then, the air bubbles B move into the second vertical reservoir <NUM> through the second opening <NUM> and are absorbed in the gas layer at the top of the second vertical reservoir <NUM>. By doing so, it becomes possible to remove the air bubbles B from the inside of the second horizontal reservoir <NUM> without providing a pipe for removal of air bubbles to the second horizontal reservoir <NUM> that might be a cause for agglomeration.

This configuration of reducing a cause for agglomeration is useful, particularly in the case of using the ink of a watercolor pigment type like in the present preferred embodiment more prone to agglomeration than other types of ink. Furthermore, according to the present preferred embodiment, the first horizontal reservoir <NUM> and the second horizontal reservoir <NUM> are made of resin. By doing so, in the case of using the ink of a watercolor pigment type, it becomes less likely to cause agglomeration of the ink than in a case where the first horizontal reservoir <NUM> and the second horizontal reservoir <NUM> are made of metal.

In the drawings, the supply reservoir <NUM> and the collection reservoir <NUM> are shown to be tilted to an angle of tilt about <NUM>° in <FIG> and <FIG> and to an angle of about <NUM>° in <FIG> and <FIG>. Preferably, the angle of tilt of the top surface of each of the first horizontal reservoir <NUM> and the second horizontal reservoir <NUM> from the horizontal direction is equal to or greater than <NUM>°. Setting the angle equal to or greater than <NUM>° causes air bubbles to move easily along the top surface.

Preferably, the angle of tilt of each of the first horizontal reservoir <NUM> and the second horizontal reservoir <NUM> from the horizontal direction is equal to or less than <NUM>°. If the sectional shape of the first horizontal reservoir <NUM> is constant like in the present preferred embodiment, tilt of the top surface also tilts the bottom surface. This causes a large difference in a distance from the supply port <NUM> at the bottom surface to the head <NUM> between a position adjacent to the one end 51a and a position adjacent to the other end 51b. Hence, if the supply pipes <NUM> have an equal length, larger slack is caused in the supply pipe <NUM> adjacent to the other end 51b. Setting the angle of tilt equal to or less than <NUM>° makes it possible to suppress slack in the supply pipe <NUM> adjacent to the other end 51b. This also applies to the second horizontal reservoir <NUM>.

In consideration of ease of moving air bubbles and layout of the pipes <NUM> and <NUM> as a design issue, the angle of tilt of each of the first horizontal reservoir <NUM> and the second horizontal reservoir <NUM> is more preferably equal to or greater than <NUM>° and equal to or less than <NUM>°.

As conceptually shown in <FIG>, by tilting the bottom surface of the first horizontal reservoir <NUM> in such a manner that the bottom surface extends downward from the one end 51a toward the other end 51b, precipitates P deposited on the bottom surface in the first horizontal reservoir <NUM> move along the bottom surface toward the other end 51b as a lowermost point at the bottom surface.

In this regard, as shown in <FIG> and in an enlarged view in <FIG>, the supply port <NUM> provided at the bottom surface of the first horizontal reservoir <NUM> includes a first cylindrical part 510a penetrating the bottom surface of the first horizontal reservoir <NUM> from top to bottom to form communication between the inside and outside of the first horizontal reservoir <NUM>. The first cylindrical part 510a has an upper end located above the bottom surface (inner surface) of the first horizontal reservoir <NUM>. The first cylindrical part 510a has a lower end located outside the first horizontal reservoir <NUM> and communicably connected to the supply pipe <NUM> coupled the head <NUM>.

As described above, the upper end of the first cylindrical part 510a is located above the bottom surface of the first horizontal reservoir <NUM>. This makes it possible to reduce a likelihood that a precipitate deposited on the bottom surface of the first horizontal reservoir <NUM> and to move toward the other end 51b along the bottom surface will enter the supply port <NUM>, the supply pipe <NUM>, and the head <NUM>.

Likewise, by tilting the bottom surface of the second horizontal reservoir <NUM> in such a manner that the bottom surface extends downward from the one end 61a toward the other end 61b, precipitates P deposited on the bottom surface in the second horizontal reservoir <NUM> move along the bottom surface toward the other end 61b as a lowermost point at the bottom surface.

As shown in <FIG>, the collection port <NUM> provided at the bottom surface of the second horizontal reservoir <NUM> includes a second cylindrical part 610a penetrating the bottom surface of the second horizontal reservoir <NUM> from top to bottom to form communication between the inside and outside of the second horizontal reservoir <NUM>. The second cylindrical part 610a has an upper end located above the bottom surface (inner surface) of the second horizontal reservoir <NUM>. The second cylindrical part 610a has a lower end located outside the second horizontal reservoir <NUM> and communicably connected to the collection pipe <NUM> coupled to the head <NUM>.

As described above, the upper end of the second cylindrical part 610a is located above the bottom surface of the second horizontal reservoir <NUM>. This makes it possible to reduce a likelihood that a precipitate deposited on the bottom surface of the second horizontal reservoir <NUM> and to move toward the other end 61b along the bottom surface will enter the collection port <NUM>, the collection pipe <NUM>, and the head <NUM>.

As conceptually shown in <FIG>, by tilting the bottom surface of the first vertical reservoir <NUM> in such a manner that the bottom surface extends downward toward the first opening <NUM>, precipitates P deposited on the bottom surface in the first vertical reservoir <NUM> move along the bottom surface toward an end adjacent to the first opening <NUM> as a lowermost point at the bottom surface.

Likewise, as conceptually shown in <FIG>, by tilting the bottom surface of the second vertical reservoir <NUM> in such a manner that the bottom surface extends downward toward the second opening <NUM>, precipitates P deposited on the bottom surface in the second vertical reservoir <NUM> move along the bottom surface toward an end adjacent to the second opening <NUM> as a lowermost point at the bottom surface.

As described above, the bottom surface of each of the first horizontal reservoir <NUM>, the first vertical reservoir <NUM>, the second horizontal reservoir <NUM>, and the second vertical reservoir <NUM> has a shape tilted toward the lowermost point at the corresponding bottom surface. As a result, the precipitates P gather at the lowermost point at each bottom surface.

As shown in <FIG>, the first horizontal reservoir <NUM> includes a first discharge port <NUM> penetrating the bottom surface from top to bottom in the vicinity of the other end 51b as the lowermost point at the bottom surface. The first vertical reservoir <NUM> includes a second discharge port <NUM> penetrating the bottom surface from top to bottom in the vicinity of the end thereof adjacent to the first opening <NUM> as the lowermost point at the bottom surface. The second horizontal reservoir <NUM> includes a third discharge port <NUM> penetrating the bottom surface from top to bottom in the vicinity of the other end 61b as the lowermost point at the bottom surface. The second vertical reservoir <NUM> includes a fourth discharge port <NUM> penetrating the bottom surface from top to bottom in the vicinity of the end thereof adjacent to the second opening <NUM> as the lowermost point at the bottom surface. In this way, the discharge port for discharge of a precipitate is provided in the vicinity of the lowermost point at each of the bottom surfaces where the precipitate gathers.

The ink supplier <NUM> includes the discharge unit <NUM> for discharging a precipitate accumulated in the first horizontal reservoir <NUM>, the first vertical reservoir <NUM>, the second horizontal reservoir <NUM>, and the second vertical reservoir <NUM>.

As shown in <FIG>, the discharge unit <NUM> includes a first discharge pipe <NUM>, a second discharge pipe <NUM>, a first solenoid valve <NUM>, a second solenoid valve <NUM>, a third discharge pipe <NUM>, a discharge pump <NUM>, a drain exit <NUM>, and a drip receiver <NUM>.

The first discharge pipe <NUM> includes a first inlet <NUM>, a second inlet <NUM>, an outlet <NUM> (not shown in the drawings), and a pipe section <NUM>. The first inlet <NUM> is connected to the first discharge port <NUM> of the first horizontal reservoir <NUM>. The second inlet <NUM> is connected to the third discharge port <NUM> of the second horizontal reservoir <NUM>. The outlet <NUM> is connected to an input side of the first solenoid valve <NUM>. The pipe section <NUM> branches into a Y-shape. Thus, an incoming liquid from the first inlet <NUM> and an incoming liquid from the second inlet <NUM> are merged to flow out through the outlet <NUM>.

As shown in <FIG> and <FIG>, the second discharge pipe <NUM> includes a first inlet <NUM>, a second inlet <NUM>, an outlet <NUM>, and a pipe section <NUM>. The first inlet <NUM> is connected to the second discharge port <NUM> of the first vertical reservoir <NUM>. The second inlet <NUM> is connected to the fourth discharge port <NUM> of the second vertical reservoir <NUM>. The outlet <NUM> is connected to an input side of the second solenoid valve <NUM>. The pipe section <NUM> branches into a Y-shape. Thus, an incoming liquid from the first inlet <NUM> and an incoming liquid from the second inlet <NUM> are merged to flow out through the outlet <NUM>.

The third discharge pipe <NUM> includes a first inlet <NUM>, a second inlet <NUM>, an outlet <NUM>, and a pipe section <NUM>. The first inlet <NUM> is connected to an output side of the first solenoid valve <NUM>. The second inlet <NUM> is connected to an output side of the second solenoid valve <NUM>. The pipe section <NUM> branches into a Y-shape. Thus, an incoming liquid from the first inlet <NUM> and an incoming liquid from the second inlet <NUM> are merged to flow out through the outlet <NUM>. If only one of the first solenoid valve <NUM> and the second solenoid valve <NUM> is opened, a liquid flows from only one of the first inlet <NUM> and the second inlet <NUM> to flow out through the outlet <NUM>.

The discharge pump <NUM> is a so-called tube pump that squeezes a flexible pipe with a roller to generate a flow of a fluid in the pipe. Even if ink flowing in the pipe contains a precipitate, using such a tube pump as the discharge pump <NUM> makes it possible to deliver the ink together with the precipitate without causing operation failure.

The discharge pump <NUM> is attached to a part of the pipe section <NUM> of the third discharge pipe <NUM> closer to the outlet <NUM> than the Y-shape branch. By doing so, driving the discharge pump <NUM> generates a flow of the ink from the first inlet <NUM> toward the outlet <NUM> and a flow of the ink from the second inlet <NUM> toward the outlet <NUM> in the third discharge pipe <NUM>.

The outlet <NUM> of the third discharge pipe <NUM> is connected to the drain exit <NUM>. The drain exit <NUM> is configured in such a manner as to discharge the ink downward. The drip receiver <NUM> of a dish shape is provided under the drain exit <NUM>. The drip receiver <NUM> is moved by a drip receiver moving mechanism <NUM> between a drip receiving position directly under the drain exit <NUM> (a position in <FIG>) and a retreat position not overlapping the drain exit <NUM> one above the other (not shown in the drawings). An air cylinder is used as the drip receiver moving mechanism <NUM>, for example.

According to the present preferred embodiment, during implementation of a process of discharging the ink by the discharge unit <NUM>, discharge of the ink from the horizontal reservoirs <NUM> and <NUM> and discharge of the ink from the vertical reservoirs <NUM> and <NUM> are conducted separately. A procedure thereof is as follows.

First, the discharge pump <NUM> is driven while the first solenoid valve <NUM> is opened. Opening the first solenoid valve <NUM> forms communication between the outlet <NUM> of the first discharge pipe <NUM> and the first inlet <NUM> of the third discharge pipe <NUM> through the first solenoid valve <NUM>. Driving the discharge pump <NUM> generates a flow of the ink from the first inlet <NUM> toward the outlet <NUM> in the third discharge pipe <NUM>. By doing so, a flow of a fluid from the first inlet <NUM> and a flow of a fluid from the second inlet <NUM> toward the outlet <NUM> are generated in the first discharge pipe <NUM>. As a result, the ink containing a precipitate is sucked through the first discharge port <NUM> of the first horizontal reservoir <NUM> connected to the first inlet <NUM> of the first discharge pipe <NUM> and through the third discharge port <NUM> of the second horizontal reservoir <NUM> connected to the second inlet <NUM> of the first discharge pipe <NUM>, and is then discharged through the drain exit <NUM>. After passage of a predetermined period of time, the first solenoid valve <NUM> is closed. At this time, the discharge pump <NUM> may be stopped or may be kept driven.

Next, the discharge pump <NUM> is driven while the second solenoid valve <NUM> is opened. Opening the second solenoid valve <NUM> forms communication between the outlet <NUM> of the second discharge pipe <NUM> and the second inlet <NUM> of the third discharge pipe <NUM> through the second solenoid valve <NUM>. Driving the discharge pump <NUM> generates a flow of the ink from the second inlet <NUM> toward the outlet <NUM> in the third discharge pipe <NUM>. By doing so, a flow of a fluid from the first inlet <NUM> and a flow of a fluid from the second inlet <NUM> toward the outlet <NUM> are generated in the second discharge pipe <NUM>. As a result, the ink containing a precipitate is sucked through the second discharge port <NUM> of the first vertical reservoir <NUM> connected to the first inlet <NUM> of the second discharge pipe <NUM> and through the fourth discharge port <NUM> of the second vertical reservoir <NUM> connected to the second inlet <NUM> of the second discharge pipe <NUM>, and is then discharged through the drain exit <NUM>. After passage of a predetermined period of time, the second solenoid valve <NUM> is closed and the discharge pump <NUM> is stopped. The process is discharging the ink is performed in this way.

The process of discharging the ink by the discharge unit <NUM> is performed when the printing process by the printing apparatus <NUM> stops. When the printing process stops, a cap to receive the discharged ink is arranged under the head unit <NUM>, for example. Then, as maintenance of the head unit <NUM>, the ink is ejected from the head <NUM> in a purge process, for example, or the process of discharging the ink is performed by the discharge unit <NUM>. Thus, during implementation of the process of discharging the ink by the discharge unit <NUM>, the drip receiver <NUM> is located at the retreat position to cause the ink discharged through the drain exit <NUM> to move toward the cap. For implementation of the printing process thereafter, the head unit <NUM> and the cap are moved away from each other and the head unit <NUM> is located above the printing medium M. At this time, the drip receiver <NUM> is located at the drip receiving position. By doing so, the ink adhering to the periphery of the drain exit <NUM> becomes unlikely to drop onto the printing medium M under the drain exit <NUM>.

While the preferred embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment.

According to the above-described preferred embodiment, the one ends 51a and 61a of the horizontal reservoirs <NUM> and <NUM> directly communicate with the vertical reservoirs <NUM> and <NUM> through the openings <NUM> and <NUM> respectively. However, the present invention is not limited to this configuration. The one ends 51a and 61a of the horizontal reservoirs <NUM> and <NUM> may form indirect communications through connection pipes, for example.

<FIG> is a conceptual view showing the behaviors of air bubbles and precipitates in a supply reservoir <NUM> according to a modification. At the supply reservoir <NUM>, one end 51Ma of a first horizontal reservoir <NUM> and a first opening <NUM> of a first vertical reservoir <NUM> are communicably connected to each other through a connection pipe <NUM>.

In the illustration in <FIG>, a top surface of the first horizontal reservoir <NUM> and a top surface of the connection pipe <NUM> are continuous with each other while extending at the same angle of tilt from the other end 51Mb of the first horizontal reservoir <NUM> to the first opening <NUM>. By doing so, the top surface from the other end 51Mb of the first horizontal reservoir <NUM> to the first opening <NUM> is tilted from the horizontal direction at a predetermined angle of tilt in such a manner as to extend upward from the other end 51Mb toward the one end 51Ma of the first horizontal reservoir <NUM>. By doing so, even if the first horizontal reservoir <NUM> and the first vertical reservoir <NUM> are communicably connected to each other indirectly through the connection pipe <NUM>, air bubbles in the first horizontal reservoir <NUM> are still allowed to move along the top surface of the first horizontal reservoir <NUM> and the top surface of the connection pipe <NUM> into the first vertical reservoir <NUM> through the first opening <NUM>.

According to the above-described preferred embodiment, the respective bottom surfaces of the vertical reservoirs <NUM> and <NUM> have planar shapes tilted from the horizontal direction. Thus, the lowermost points at the bottom surfaces are located at ends of the bottom surfaces of the vertical reservoirs <NUM> and <NUM>, and the discharge ports <NUM> and <NUM> are provided in the vicinity of the end of the vertical reservoir <NUM> and in the vicinity of the end of the vertical reservoir <NUM> respectively. However, the bottom surfaces of the vertical reservoirs <NUM> and <NUM> are not limited to planar shapes. For example, each of the bottom surfaces may have a funnel shape pointed downward further at a position closer to the center to locate a lowermost point at the center of the bottom surface, and a discharge port may be provided at the center of the bottom surface.

The ink used in the above-described preferred embodiment is ink of a watercolor pigment type. However, the present invention is not limited to this configuration. The ink may be oil-based ink or dye-based ink.

According to the above-described preferred embodiment, the printing apparatus <NUM> includes the coating processor <NUM> and the drying processor <NUM>. However, the present invention is not limited to this configuration. The ink supplier of the present invention may be used in a printing apparatus to perform only the printing process.

Claim 1:
An ink supplier (<NUM>) that supplies ink to a plurality of heads (<NUM>) in an ink-jet printing apparatus (<NUM>), comprising:
a supply reservoir (<NUM>) storing said ink to be supplied to said plurality of heads (<NUM>); and
a discharge pipe (<NUM>,<NUM>,<NUM>) having a pump (<NUM>) and used for discharging said ink from said supply reservoir (<NUM>),
said supply reservoir (<NUM>) including:
a first horizontal reservoir (<NUM>) having a cylindrical shape extending in a direction of alignment of said plurality of heads (<NUM>), and having a plurality of supply ports (<NUM>) each communicating with one of said plurality of heads (<NUM>); and
a first vertical reservoir (<NUM>) having a side surface provided with a first opening (<NUM>) directly or indirectly communicating with one end (51a) of said first horizontal reservoir (<NUM>), and having a cylindrical shape with a closed bottom larger in a top-bottom direction than said first horizontal reservoir (<NUM>),
said first horizontal reservoir (<NUM>) having a bottom surface that is tilted from a horizontal direction at an angle of tilt equal to or greater than <NUM>° in such a manner as to extend downward from said one end (51a) toward the other end (51b),
wherein said first horizontal reservoir (<NUM>) includes a first discharge port (<NUM>) provided at a bottom portion of said first horizontal reservoir (<NUM>) at said other end (51b) and communicably connected to said discharge pipe (<NUM>,<NUM>,<NUM>).