Abstract:
The objective of the present invention is to provide a compact pump capable of simultaneous sucking/discharging desired volumes of fluid in a plurality of systems, which does not exist up to now. The pump comprises as follows attains the objective; a separating wall dividing a cylinder into a plurality of fluid compartments, discharging ports and sucking ports mutually arranged at opposite sides of the respective fluid compartments with respect to longitudinal direction, a plurality of pistons accommodated in the respective fluid compartments so as to slide in the respective fluid compartments and to divide respective fluid compartments into two rooms and a common piston rod for the pistons passing through the separating wall to reciprocate the pistons in fluid compartments respectively.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a pump for sucking and discharging fluid, to a sucking device for recovering liquid ejection equipped with the pump to keep a good ejection status and to an image forming apparatus equipped with the pump, particularly suitable for an ink-jet printer equipped with a plurality of eject heads.  
           [0003]    2. Brief Description of the Related Art  
           [0004]    The ink-jet printing is a method where an image is formed on a printing medium by ejecting tiny liquid droplets from eject ports of the ink-jet head and depositing them on the medium. In this kind of ink-jet head it is difficult to keep smooth ejection or impossible to eject the liquid due to clogging caused by liquid thickening as a result of drying liquid in liquid paths, by tiny foreign particles stuck to eject ports or by bubbles generated in ink in liquid paths.  
           [0005]    As measures recovering such poor ejection status in the ink-jet head, a sucking method to remove thickened ink or bubbles in liquid paths from eject ports by reducing a pressure in liquid head with the aid of a pump is usually used. As the pump for the sucking, a plunger pump where a piston moves reciprocatingly in a cylinder or a tube pump where a flexible tube is ironed by a roller attached to the periphery of a rotating rotor, is selected according to conditions such as spacing efficiency and costs etc.  
           [0006]    In an ink-jet color printer where several color inks for forming color images are used, usually two or more ink-jet head are used for accommodating several color inks. A unit having corresponding number of pumps, that works simultaneously, to ink-jet heads or a unit with one pump that works according to a time shared schedule for each ink-jet head is known as a sucking device for recovering liquid ejection equipped in the ink-jet printer.  
           [0007]    Rough structures of such conventional sucking devices for liquid recovery are illustrated in FIG. 9 and FIG. 10. The device in FIG. 9 has pumps corresponding numbers to ink-jet heads, while the device in FIG. 10 has one pump to a plurality of ink-jet heads (In FIG. 10 two heads are illustrated.)  
           [0008]    In FIG. 9 two ink-jet heads  53  and  54  are mounted on a carriage  52  which moves reciprocatingly along a guide rod  51 . At the home position of the carriage  52 , a pair of cap members  57 ,  58  that cover eject ports (not shown in FIG. 9) are arranged respectively so as to face and to move backward/forward against eject surfaces  55 ,  56  where ejects ports are formed. Plunger pumps  61 ,  62  are respectively connected to cap members  57 ,  58  via sucking pipes  59 ,  60 . During sucking operations for recovering liquid ejection, cap members are pressed to eject surfaces  55 ,  56  and plunger pumps  61 ,  62  are activated so as to suck thickened ink in ink-jet heads  53 ,  54  and then so as to discharge the sucked ink to a waste ink tank (not shown in FIG. 9) via discharging ports  63 ,  64 .  
           [0009]    In FIG. 10 at the home position of the carriage  52 , a pair of cap members  57 ,  58  that cover eject ports (not shown in FIG. 10) are arranged respectively so as to face and to move backward/forward against eject surfaces  55 ,  56  where eject ports are formed. A plunger pump  61  is connected to a cap member  57  via a sucking pipe  59  while a cap member  58  covers an eject surface  56 . During sucking operations for recovering liquid ejection cap members  57 ,  58  are pressed to eject surfaces  55 ,  56  and a plunger pump  61  is activated so as to suck thickened ink and the like in ink-jet heads  53  and then so as to discharge to a waste ink tank (not shown in FIG. 10) via a discharge port  63 . Then cap members  57 ,  58  are removed from eject surfaces  55 ,  56  and the carriage  52  is transferred to a position where the eject surface  56  of the other ink-jet head  54  faces the cap member  57 . Again the cap member  57  is pressed to the eject surface  56  and the plunger pump  61  is activated so as to suck thickened ink and the like in ink-jet head  54  and then so as to discharge to the waste ink tank (not shown in FIG. 10) via the discharge port  63 .  
           [0010]    Since pumps such as  61 ,  62  and so forth corresponding numbers to ink-jet heads such as  53 ,  54  and so forth are required in the device shown in FIG. 9, namely corresponding numbers of comprising parts are required, it is inevitable to increase the production cost of the device. In addition, since space to accommodate respective pumps  61 ,  62  and so forth is required, the larger sized sucking device i.e. a larger sized casing for the ink-jet printer is inevitable, which also leads to a cost increase.  
           [0011]    Though the above-mentioned problems are solved by the conventional sucking device for recovering liquid ejection shown in FIG. 10, another problem where operating efficiency of the printer is lowered due to increased duration for the sucking operations for recovering liquid ejection against respective ink-jet heads  53 ,  54 , which are carried out on the time sharing schedule. A further problem, a complicated controlling procedure for the recovering operations is required, is caused, since ink volumes sucked from ink-jet heads  53 ,  54  by one pump  61  should be set respectively.  
         SUMMARY OF THE INVENTION  
         [0012]    One of the objectives of the present invention is to provide a compact pump that sucks and discharges fluid with respective desired volumes simultaneously in a complicated system.  
           [0013]    The other objective of the present invention is to provide a sucking device for recovering liquid ejection and an image forming apparatus equipped with the pump which keeps liquid ejected from liquid eject ports in good ejecting status.  
           [0014]    A first embodiment is a pump comprising; at least one separating wall dividing an internal space of a cylinder into a plurality of fluid compartments with respect to a longitudinal direction of the cylinder, a plurality of discharging ports connected respectively to the fluid compartments at one side of the cylinder with respect to the longitudinal direction, a plurality of sucking ports connected respectively to the fluid compartments at other remaining side of the cylinder with respect to the longitudinal direction, a plurality of pistons accommodated in the respective fluid compartments so as to slide in the respective fluid compartments and to divide respectively the fluid compartments into two rooms and a piston rod for common use to the respective pistons passing through the separating wall to reciprocate the pistons in the fluid compartments respectively.  
           [0015]    According to the present invention pistons in fluid compartments are respectively moved by one piston rod so that liquid in each fluid compartment is sucked via each sucking port and discharged via each discharging port in accordance with the reciprocating movements of the piston rod.  
           [0016]    Further a plurality pairs of stoppers arranged on the piston rod so as to face each other at both sides of respective pistons to regulate slide movements of the pistons along the piston rod, connecting paths formed between the piston rod and stoppers for connecting two compartments and switching valves to shut connecting paths during the forward movements of the piston rod toward discharging ports and to open connecting paths during the backward movements of the piston rod toward sucking ports may be arranged in the pump according to the first embodiment.  
           [0017]    Respectively different fluid volumes sucked via sucking ports and discharged via discharging ports in accordance with the reciprocating movements of the piston rod may be attained by arranging different effective cross sectional areas of respective fluid compartments.  
           [0018]    A second embodiment the present invention is a sucking device for recovering liquid ejection to maintain good ejecting status of the liquid ejected from eject ports having a plurality of cap members covering the eject ports of a plurality of liquid eject heads to eject liquid respectively and a pump for sucking liquid from the eject ports via the cap members, where;  
           [0019]    the pump has at least one separating wall dividing an internal space of a cylinder into a plurality of liquid compartments with respect to a longitudinal direction of the cylinder, a plurality of discharging ports connected respectively to the liquid compartments at one side of the cylinder with respect to the longitudinal direction, a plurality of sucking ports connected respectively to the liquid compartments at other remaining side of the cylinder with respect to the longitudinal direction and also connected to the cap members, at least two pistons accommodated in the respective liquid compartments so as to slide in the respective liquid compartments and to divide respectively the liquid compartments into two rooms and a piston rod for common use to at least the two pistons passing through the separating wall to reciprocate at least the two pistons in the liquid compartments respectively.  
           [0020]    In the sucking device for recovering liquid ejection according to the second embodiment, further a plurality pairs of stoppers arranged on the piston rod so as to face each other at both sides of respective pistons to regulate slide movements of the pistons along the piston rod, connecting paths formed between the piston rod and stoppers to connect two compartments and switching valves to shut connecting paths during the forward movements of the piston rod toward discharging ports and to open connecting paths during the backward movements of the piston rod toward sucking ports may be arranged.  
           [0021]    Respectively different liquid volumes sucked via sucking ports and discharged via discharging ports in accordance with the reciprocating movements of the piston rod may be attained by arranging different effective cross sectional areas of respective liquid compartments.  
           [0022]    As the above-mentioned liquid, ink and/or treatment liquid to adjust printing property of ink ejected on a printing medium may be used.  
           [0023]    One of a plurality of the liquid eject heads may be used only for black ink while remaining other heads may be used for a plurality of color inks except black ink. In this case sucked volume of the black ink should be set preferably less than accumulated sucked volumes of color inks.  
           [0024]    A third embodiment according to the present invention is an image forming apparatus to maintain good ejecting status of the liquid ejected from eject ports having a portion to install a plurality of liquid eject heads to eject liquid onto a printing medium from respective eject ports so as to form image, a plurality of cap members covering the respective eject ports of liquid eject heads and a pump for sucking liquid from the eject ports via the cap members, where;  
           [0025]    the pump has at least one separating wall dividing an internal space of a cylinder into a plurality of liquid compartments with respect to a longitudinal direction of the cylinder, a plurality of discharging ports connected respectively to the liquid compartments at one side of the cylinder with respect to the longitudinal direction and also connected to the cap members, a plurality of sucking ports connected respectively to the liquid compartments at other remaining side of the cylinder with respect to the longitudinal direction, at least two pistons accommodated in respective liquid compartments so as to slide in the respective liquid compartments and to divide respectively liquid compartments into two rooms and a piston rod for common use to at least the two pistons passing through the separating wall to reciprocate at least the two pistons in the liquid compartments respectively.  
           [0026]    In the image forming apparatus according to the third embodiment, further at least two stoppers arranged on the piston rod so as to face each other at both sides of respective pistons to regulate slide movements of the piston along the piston rod, connecting paths formed between the piston rod and stoppers to connect two compartments and switching valves to shut connecting paths during the forward movements of the piston rod toward discharging ports and to open connecting paths during the backward movements of the piston rod toward sucking ports may be arranged.  
           [0027]    Respectively different liquid volumes sucked via sucking ports and discharged via discharging ports in accordance with the reciprocating movements of the piston rod may be attained by arranging different effective cross sectional areas of respective liquid compartments.  
           [0028]    As the above-mentioned liquid, ink and/or treatment liquid to adjust printing property of the ink ejected on a printing medium may be used.  
           [0029]    One of a plurality of the liquid eject heads may be used only for black ink while remaining other heads may be used for a plurality of color inks except black. In this case sucked volume of the black ink should be set preferably less than accumulated sucked volumes of color inks.  
           [0030]    The portion to install eject heads may have a carriage moving in a direction to cross a transferring direction of the printing medium onto which liquid is ejected from the liquid eject ports. In this case liquid eject heads may be mounted on the carriage demountably via a mounting/demounting means.  
           [0031]    Further, the eject heads may have eject energy generating members to eject liquid from eject ports. In this case electro-thermal energy conversion elements to generate enough thermal energy to cause a film boiling in the liquid may be employed as the eject energy generating members.  
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0032]    [0032]FIG. 1 is a perspective view illustrating an inner structure of a serial ink-jet printer where the image forming apparatus according to the present invention is equipped.  
         [0033]    [0033]FIG. 2 is a plan view of the partially enlarged sucking device for recovering liquid ejection in the embodiment shown in FIG. 1.  
         [0034]    [0034]FIG. 3 is a schematic view illustrating a rough structure of the sucking device for recovering liquid ejection in the embodiment.  
         [0035]    [0035]FIGS. 4, 5,  6  and  7  are cross sectional views illustrating movements of the piston rod in the embodiment according to the present invention. FIG. 4 depicts a status where the piston rod is positioned at the end of the forward movement. FIG. 5 depicts a status where the piston rod starts moving backward. FIG. 6 depicts a status where the piston rod is situated at the end of the backward movement. FIG. 7 depicts a status where the piston rod starts moving forward.  
         [0036]    [0036]FIG. 8 is a sectional view illustrating a pump in the other embodiment according to the present invention.  
         [0037]    [0037]FIG. 9 is a schematic view illustrating a conventional sucking device for recovering liquid ejection.  
         [0038]    [0038]FIG. 10 is a schematic view illustrating other conventional sucking device for recovering liquid ejection.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0039]    Hereinafter embodiments according to the present invention employed in a serial scanning type ink-jet printer are explained in detail by referring FIGS.  1  to  8 . The present invention is not limited in embodiments to be described hereinafter, but embodiments may be combined and also be applied to other technologies including concepts specified in this specification.  
         [0040]    In FIG. 1 a rough structure of an ink-jet printer used in the present embodiment is shown. The following parts or members are respectively fitted to a chassis  350  of the ink-jet printer; a medium transfer mechanism (not shown in FIG. 1) to transfer a medium such as paper set in a transfer tray  101  onto a platen  301 , a carriage driving mechanism to move a carriage  203  along the printing medium in the normal direction to the medium transfer direction where a plurality of ink cartridges  202  of different colors (in FIG. 1 four color cartridges are depicted) are demountably mounted and a sucking device  500  for recovering liquid ejection at a head unit  201  mounted on the carriage  203 .  
         [0041]    The printing media set on the paper supply tray  101  are transferred onto the platen  301  by the medium transfer mechanism. A desired image is formed on the surface of the printing medium by respectively ejected inks from ink-jet heads  11 ,  12  (see FIG. 3) of the head unit  201  mounted on the carriage  203  and by repeating cycles of the medium transfer and movement of the carriage  203  which moves reciprocatingly along a carriage guide rod  360 .  
         [0042]    The head unit  201  in this embodiment consists of two ink-jet heads  11  and  12  mutually combined, more specifically the ink-jet head  11  for ejecting black ink and the ink-jet head  12  for ejecting a plurality of color inks except black ink. The ink-jet head  12  for color inks has a set of several eject ports (not shown in FIG. 1) formed on the eject surface  13  for respective color inks. (In this embodiment three color inks are used.) The ink cartridge  202  storing black ink is connected to the ink-jet head  11  for black ink, while a plurality ink cartridge  202  storing color inks are connected to the ink-jet head  12  for color inks. The carriage driving mechanism has the carriage guide rod  360  that guides the carriage  203  in the driving direction of the carriage. A sucking device  500  for recovering liquid ejection is arranged at a home position located on one end of the moving direction of the cartridge  203 .  
         [0043]    The plan view of the sucking device  500  for recovering liquid ejection according to the present embodiment is shown in FIG. 2 and a schematic structure of the device is shown in FIG. 3. The sucking device  500  for recovering liquid ejection according to the present embodiment has caps  503  for covering eject port surfaces  13  of the respective heads  11 ,  12  to prevent ink existing in eject ports of the heads  11 ,  12  and in ink paths (not shown) connected to these heads from drying or evaporating during non-printing operations, a pump  506  connected to the cap members  503  via flexible connecting pipes  505 , a wiping blade  507  to remove ink and the like stuck to the eject port surfaces  13  of the heads  11 ,  12  and a blade holder  508  to hold the wiping blade  507 .  
         [0044]    A cap holder  504  and the blade holder  508  are arranged to move reciprocatingly accompanying cap members  503  in accordance with reciprocating rotations of a holder reciprocating motor  501  in a direction facing eject surfaces  13  of ink-jet heads  11 ,  12  so as to switch from an operational position to a standby position, and vice versa. At the operational position periphery ribs of the cap members  503  closely contact with the eject surfaces  13  of ink-jet heads  11 ,  12  and a tip of the wiping blade is positioned so as to contact with eject surfaces  13  of ink-jet heads  11 ,  12 , thus heads are swept by moving the carriage  203 . At the standby position, cap members  503  and the wiping blade  507  are brought down respectively from eject surfaces  13  of ink-jet heads  11 ,  12  so as to cause no interference with eject surfaces  13  of ink-jet heads  11 ,  12 , when the carriage  203  moves.  
         [0045]    [0045]FIG. 4 shows partially enlarged structure of a pump  506  in the present embodiment. A plurality (two in the present embodiment) of cylinders  14 ,  15  having the same inner diameters connected in series are separated into a plurality (two in the present embodiment) of liquid compartments by a separating wall  16  formed of an elastically deformable material such as rubber and the like. Discharging ports  17  connected to the waste ink tank (not shown in the figure) are formed on one side of respective liquid compartments with respect to a longitudinal direction of the respective compartments. Sucking ports  18  connected to cap members  503  via flexible connecting pipes  505  are formed on the opposite sides of the liquid compartments with respect to the longitudinal direction. Circular pistons  21  dividing the respective liquid compartments into discharging rooms  19  and sucking rooms  20  are accommodated in respective liquid compartments so as to slide. A piston rod  23  extends through the pistons  21  and the separating wall  16  made of elastically deformable rubber and the like, and an end ring  22  that closes one end of the cylinder  14  located a base side. Rotating force from a motor (not shown) is transmitted to the base side end of the piston rod  23  via a power conversion mechanism  509 ,  510  so that the piston rod  23  moves reciprocatingly. A plurality pairs of stoppers  24 ,  25  are arranged on both sides of respective pistons  21 . Outer diameters of stoppers are set larger than inner diameters of pistons  21  in ring shapes and set smaller than inner diameters of cylinder  14 ,  15 . Pistons  21  can move between these pair of stoppers  24 ,  25  relatively to the piston rod  23 . Connecting paths  26  connecting the respective discharging rooms  19  and respective sucking rooms  20 , are formed between the piston rod  23  and stoppers  24 ,  25 . As shown in FIG. 4 when the piston rod  23  moves leftward, elastically deformable circular protrusions  27  formed on the pistons  21  are pressed against one end surfaces of the stoppers  24  so as to close respective connecting paths  26 . In other words the protrusions  27  formed on the pistons  21  and one end surfaces of the stoppers  24  function as valves for the connecting path.  
         [0046]    In the figures a numerical character “28” is a sealing formed of rubber and the like. As shown in FIG. 6 when the piston rod  23  is positioned at the far end of forward movement pistons  21  are stayed at positions immediately before passing discharging ports  17  so as not to close them. On the other hand as shown in FIG. 4 when the piston rod  23  is positioned at the far end of backward movement pistons  21  are stayed at positions immediately after passing sucking ports  18 . A reciprocating stroke of the piston rod  23 , a distance of a pair of pistons  24 ,  25  and respective thickness of pistons  21  are determined in order to meet the above-mentioned positionings.  
         [0047]    As shown in FIG. 4 when the piston rod  23  starts to move from the far end of forward movement, protrusions  27  formed on the pistons  21  are pressed against one end surfaces of the stoppers  24 , where connections between discharge rooms  19  and sucking rooms  20  are disconnected, ink in the discharge rooms  19  is discharged to the unshown ink waste tank via discharging ports  17  according to the movement of the piston rod  23 . As shown in FIG. 5 when the pistons  21  pass sucking ports  18 , ink is sucked from eject ports of ink-jet heads  11 ,  12  via sucking ports to sucking rooms  20  due to reducing pressure in accordance with volume increase of the sucking rooms.  
         [0048]    Thus ink in the discharging rooms  19  is discharged and ink in ink-jet heads  11 ,  12  is sucked to sucking rooms  20  until the piston rod  23  reaches to the end of the forward movement.  
         [0049]    On the other hands as shown in FIG. 6 when the piston rod  23  starts moving from the end of backward movement, other stopper  25  is pressed against the piston  21  while one end surface of the remaining stopper  24  is located apart from the protrusion  27  formed on the pistons  21 , where discharge rooms  19  and sucking rooms  20  are connected. However, as shown in FIG. 7 ink in the sucking rooms  20  in volume decreasing status flows to the discharging rooms  19  in volume increasing status, since flow resistance in sucking ports  18  is set larger than that in connecting paths  26 .  
         [0050]    By repeating reciprocating movements of the piston rod  23 , thickened ink and bubbles in ink-jet heads  11 ,  12  are sucked intermittently by the pump  506  and discharged into the waste ink tank. In the present embodiment, since the piston rod  23  passes through the cylinder  14 , the liquid compartment in this cylinder is formed smaller than the liquid compartment in the cylinder  15 , consequently sucked and discharged ink volume in the cylinder  14  is less than that in the cylinder  15 . Black ink is sucked from the ink-jet head  11  for the black ink to the cylinder  14  via attached sucking port  18  while several color inks are sucked from the ink-jet head for color inks to the cylinder  15  via attached sucking port  18 , where volume difference of each color relative to the black ink is controlled minimum.  
         [0051]    In order to attain uniform with sucked volumes of respective inks, for example, the inner diameter of the cylinder  14  may be formed smaller than that of the cylinder  15  to reduce the effective volume of the cylinder  14  as shown in FIG. 8, which attains the same sucked volumes in the black ink and the color ink. In FIG. 8 the same characters are used for members or parts having the same functions as in preceding figures.  
         [0052]    In the present embodiment a case where cylinders  14 ,  15  connected in series via the separating wall  16  so as to form two liquid compartments is explained. However, when the ink-jet head  12  is formed as a divided type according to a number of the ink cartridges  202 , numbers of cap members  203  and separating walls  16  may be adjusted to meet modified conditions. In any case one piston rod  23  attains simultaneous sucking procedures for recovering liquid ejection in a plurality of ink-jet heads  11 ,  12 .  
         [0053]    The present invention realizes its most excellent performance in an ink-jet type image forming apparatus where energy generating means (such as electro-thermal conversion element, laser light etc.) for generating energy so as to change phase of the liquid and to eject liquid are arranged. Thus, excellent printing results with high density, finer and more precise quality are obtained.  
         [0054]    It is preferable to apply the basic principle disclosed, for example, in the U.S. Pat. No. 4,723,129 and No. 4,740,796 to the present invention. Although the principle is applicable either to “on demand type” or to “continuous type”, particularly it is more effective to the on-demand type, since the thermal energy is generated to cause a nuclear boiling on the surface of the thermal energy generating means arranged against liquid paths of the liquid eject heads where the liquid is held, namely to cause a film boiling on surfaces of liquid eject heads, by applying at least one driving signal, according to information to be printed. Which, as a result, is effective, since bubbles are formed in the liquid in accordance with respective driving signals. The liquid is ejected via the eject ports and is form at least one droplet by a cycle of growing and shrinking movements of bubbles. Pulse driving signals are more favorable since more responsive liquid ejection is attained due to a quick and proper cycle of growing and shrinking movements of bubbles. Pulse driving signals disclosed in the U.S. Pat. No. 4,463,359 and No. 4,345,262 are suitable as the signals mentioned above. When the conditions disclosed in the U.S. Pat. No. 4,313,124 relating to temperature increasing rate on the surface of the energy generating means, are applied, more excellent printing quality is realized.  
         [0055]    Except arrangements disclosed in the above-referred U.S. patents combining eject ports, liquid paths and electro-thermal energy conversion elements (the straight liquid flow path where electro-thermal conversion elements are arranged along liquid path or perpendicular liquid flow path where electro-thermal conversion elements are arranged at the opposite side of eject ports with respect to liquid path), arrangements disclosed in the U.S. Pat. No. 4,558,333 and No. 4,459,600 where energy generating members are arranged at curved areas of liquid paths may be employed in the present invention. In addition, the arrangement disclosed in the Japanese laid open patent No. 59-123670 where common slits are shared among a plurality of electro-thermal conversion elements as eject ports and the arrangement disclosed in the Japanese laid open patent No. 59-138461 where openings to absorb pressure wave from thermal energy are arranged against eject portions are also effectively employed in the present invention. In other words, the present invention realizes reliable and effective printings, regardless of arrangements of liquid eject heads.  
         [0056]    The present invention may be effectively applied to a full line type liquid eject heads having a length corresponding to maximum width of a printing medium on which an image forming apparatus prints images. The full line type liquid eject heads are obtained by combining a plurality of liquid eject heads to fulfill the required width or by a liquid eject head formed in one piece.  
         [0057]    A solid liquid eject head fixed to the carriage which moves reciprocatingly, a tipped liquid eject head demoutably mounted on the carriage where electrical connections to the apparatus and liquid supply from the apparatus are attained or a cartridge where a liquid eject head and a tank for storing liquid are formed in one piece, is also effectively employed in the above-mentioned serial type printer.  
         [0058]    It is preferable to add auxiliary means to the arrangement of the image forming apparatus, since effects according to the present invention are enhanced more. More specifically, the auxiliary means may be a cleaning means for the liquid eject head, pressure application means, auxiliary heating means used together with the electro-thermal conversion means or other heating elements, or a combination of them and auxiliary eject means used except printing etc.  
         [0059]    The present invention is quite effectively used in a printing apparatus having at least one of the following functions; printing modes to select a plurality of colors or mixed colors for full color printing. In this case for adjusting printing quality according to kinds of printing media and printing modes, it is effective to eject print adjusting liquid (printing quality enhancer) from the common liquid eject heads or an exclusive eject head.  
         [0060]    In the embodiment of the present invention mentioned above, ink which solidifies at or less than room temperature and softens or melts at room temperature, may be used. Or since usually in ink-jet printings liquid temperature is controlled between 30° C. and 70° C. so as to keep liquid viscosity suitable for stable ejection, ink which liquefied when signals are applied, may be also used. In addition, ink which is solid at room temperature but is liquid when heated may be used, since temperature rising in ink and as a result evaporation of the ink is suppressed by a phase change where generated thermal energy is used for the phase change from a solid state to a liquid state. Any ink with a property liquefied for ejecting only when thermal energy applied, such as ink liquefied by applied thermal energy in accordance with printing signals, ink that starts solidifying just when it is deposited on printing media may be used. The liquid bearing above-mentioned properties may be used in ways disclosed in the Japanese laid open patents No. 54-56847 and No. 60-71260 where ink is stored in the solid or liquid form in concave pits or through holes of the porous sheet arranged so as to face against electro-thermal conversion elements. In the invention the film boiling method is the most effective for the above-mentioned liquids.  
         [0061]    The image forming apparatus according to the present invention is used not only as an image outputting terminal for an information processing unit such as a computer and the like, but also a copying device combined a reading device, a facsimile equipped with transmitting/receiving functions and a textile printing apparatus etc. Sheet formed or extending paper and cloth, or wood, stone, plastic, glass and metal in sheet form, or further a 3-dimensionally structured body may be used as the printing medium.  
         [0062]    The pump according to the present invention realizes more compact devices and apparatuses with reduced manufacturing costs, since sucking from sucking ports and discharging from discharging ports in respective fluid compartments divided by the separating wall are carried out by the reciprocating movements of one piston rod.  
         [0063]    Particularly since the separating wall dividing the cylinder into a plurality of the fluid compartments is formed, fluid in respective fluid compartments can be discharged due to a slight (positive) pressure change caused by movements of the pistons. Which can avoid a problem where the fluid stays in cylinders and finally sticks to the walls of cylinders. Since respective sucking ports are arranged on the same side of the cylinders while respective discharging ports are arranged on the opposite sides with respect to the longitudinal direction of the cylinders, and since cylinders are arranged in series configuration via the separating wall, sucking and discharging fluid in respective fluid compartment can be executed on the same timing. Thus a pump with easy maneuverability can be provided.  
         [0064]    Also the sucking device for recovering liquid ejection or the image forming apparatus according to the present invention realizes more compact devices and apparatuses with reduced manufacturing costs, since sucking from sucking ports and discharging from discharging ports in respective liquid compartments divided by the separating wall are carried out by the reciprocating movements of one piston rod.  
         [0065]    When volumes of fluid or liquid sucked to a respective plurality of fluid or liquid compartments and discharged from discharging ports are adjusted differently, most preferable sucking/discharging operations in respective fluid or liquid compartments are attained.  
         [0066]    Volumes of liquid sucked to a respective plurality of liquid compartments and discharged from discharging ports in response to the reciprocating movements of the piston rod may be respectively determined by adjusting effective cross sectional areas differently.  
         [0067]    The wasted black ink may be suppressed by setting sucked volume of the black ink from the liquid head for the black ink lower than the accumulated sucked volume of color inks from liquid heads for color inks.