Abstract:
To reduce a quantity of uselessly consumed ink when an ink jet head is recoverably activated, the capacity of an ink path communicated with a group of ejecting ports having a small flow rate coefficient is determined to be smaller than that of an ink path communicated with a group of ejecting ports having a large flow rate coefficient. While all of plural groups of, ejecting ports are fully covered with a common recovering cap with the aid of sucking means, ink is, sucked from the plural groups of ejecting ports. When the ink remaining in the region extending from the plural groups of ejecting ports to predetermined positions in a plurality of ink paths communicated with the plural groups of ejecting ports is discharged, ink discharging positions are dislocated to predetermined positions in a plurality of ink paths to positionally coincide with the predetermined positions in the substantially same timing relationship after ejection recovering treatment starts to be conducted.

Description:
This application is a continuation of application Ser. No. 09/266,686 filed Jun. 28, 1994, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates generally to an ink jet head, an ink jet apparatus and a method of recoverably activating in the apparatus. 
     In the case that the ink jet apparatus is kept unused for a long time or in the case that some specific ejecting ports among a plurality of ejecting ports is rarely used compared with other ejecting ports, there sometimes arises a malfunction that ink is improperly ejected from the ejecting ports. The reason why the foregoing improper ink ejection occurs consists in that water in ink is evaporated from the ejection ports or water in ink is evaporated from an ink chamber communicated with the ejection ports. In addition, there arises another malfunction that some ink droplets, some water droplets or dust particles adhere to the ejection surface of an ink jet head having a plurality of ejecting ports formed thereon, causing each ejected ink droplets to be pulled by the adhered foreign materials with the result that the ejecting direction is deviated from a predetermined one. 
     To prevent the foregoing malfunction from arising, a conventional ink jet apparatus is equipped with means as noted below to serve as a so-called ejection recovering system. This ejection recovering system is exemplified by e.g., preliminary ejecting means for discharging ink having an increased viscosity in a predetermined ink receiving medium prior to each recording operation, ink sucking means for removing some adhered materials from ejecting ports and a common ink chamber by sucking ink therefrom, ink sucking means for removing air bubbles introduced in ink at the time of ink reservoir replacement, and capping means for preventing water in ink from being vaporized from ejecting ports. 
     However, the conventional ejection recovering system has some following problems. Specifically, the ink jet apparatus is unavoidably fabricated at an increased cost attributable to necessity for disposing the preliminary ejecting means, the ink sucking means or the capping means. In addition, it is practically difficult to design and construct the ink jet apparatus with small dimensions because of necessity for reserving a space required for disposing the preliminary ejecting means, the ink absorbing means or the capping means. Additionally, it is necessary that an ink reservoir, a suction pump and associated pipings are arranged for executing preliminary ejection or ink suction, and moreover, accumulatively store waste ink in a certain container. 
     With respect to an ink jet apparatus capable of recording colored images, development works have been hitherto conducted for providing an ink jet apparatus including an ink jet head having plural groups of ejecting ports for black ink, yellow ink, magenta ink and cyan ink formed thereon, ink reservoirs independently disposed corresponding the groups of ejecting ports, a recovering cap common to the ejecting ports, and an ejection recovering unit. This kind of ink jet apparatus is often designed and constructed to record an image colored with two or three kinds of colors other than black. In this case, when a quantity of color ink per one dot is equalized to that of black ink, the diameter of a printed dot recorded on a recording medium is excessively enlarged. In view of the foregoing fact, when each dot is recorded with color ink, the diameter of each injecting port is reduced or the cross-sectional area of an injection nozzle is reducibly varied. To practice a so-called bubble jet recording system for ejecting liquid droplets by heating electrothermal transducers, a measure is taken such that a surface area of each heating elements is reduced or a distance between the heat generating element and an ejection orifice is changed to another one. 
     An ink jet apparatus using plural kinds of inks each having a different color and/or different depth of color employed therefor includes an ink jet head or an ink jet head unit having plural groups of ejecting ports formed therein, and the nozzle cross-sectional area of each ejecting port among a group of ejecting ports and the diameter of the same each varies from plural groups of ejecting ports. In addition, this ink jet apparatus includes an ejection recovering unit but this ejection recovering unit has the following shortages. Specifically, in the case that a magnitude of resistance against flowing of ink differs from each of plural groups of ejection ports and a sucking operation is achieved by a common recovering cap, a quantity of ink sucked by a single recovering operation each varies from plural groups  23  of ejecting ports. Consequently, a large quantity of ink is sucked by each ejection port among a group of ejecting ports having a large flow rate coefficient but a small quantity of ink is sucked by each ejection port among a group of ejecting ports having a small flow rate coefficient. If a quantity of ink sucked by each ejecting port during each sucking operation each varies from plural groups of ejecting ports, ink should be sucked from plural groups of ejecting ports in such a manner as to match with the quantity of ink sucked by the group of ejecting ports where a magnitude of resistance against flowing of ink is maximized, in order to remove air bubbles introduced in ink at the time of ink reservoir replacement or discharge ink having an increased viscosity in an ink path. For this reason, a quantity of ink in excess of a required quantity is sucked from other groups of ejecting ports and then uselessly wasted therefrom. 
     A flow rate coefficient of plural groups of ejection ports adapted to eject plural kinds of inks each having a different kind of color and/or different depth of color is substantially determined depending on a sum of the cross-sectional area of each ejecting ports involved in each of plural groups of ejecting ports. Obviously, the sum of the cross-sectional area of all the ejecting ports is determined based on the cross-sectional area of each ejecting port and the number of ejecting ports. Thus, in the case that plural groups of ejecting ports each having a different flow rate coefficient are subjected to ejection recovering treatment by utilizing the pressure in the fully capped state in consideration of the current technical tendency for reducing the number of components constituting the ink jet apparatus and simplifying the structure of the ink jet apparatus, the aforementioned malfunctions are liable to arise. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in consideration of the aforementioned background. 
     An object of the present invention is to provide an ink jet head for an ink jet apparatus which assures that a quantity of uselessly consumed ink when the ink jet head is recoverably activated can be reduced. 
     Another object of the present invention is to provide an ink jet apparatus in which an ink jet head of the foregoing type is installed. 
     Further object of the present invention is to provide a method of recoverably activating an ink jet apparatus of the foregoing type. 
     According to a first aspect of the present invention, there is provided an ink jet head including plural groups of ejecting ports each having a different flow rate coefficient, wherein a capacity of an ink path communicated with a group of ejecting ports having a small flow rate coefficient is smaller than that of an ink path communicated with a group of ejecting ports having a large flow rate coefficient. 
     In addition, according to a second aspect of the present invention, there is provided an ink jet apparatus having an ink jet head of the foregoing type installed therein, wherein the ink jet head includes plural groups of ejecting ports each having a different flow rate coefficient in such a manner that a capacity of an ink path communicated with a group of ejecting ports having a small flow rate coefficient is smaller than that of an ink path communicated with a group of ejecting ports having a large flow rate coefficient, and sucking means is arranged for sucking ink from the plural group of ejecting ports in the state that the latter are fully covered with a common recovering cap. 
     Additionally, according to a third aspect of the present invention, there is provided a method of recoverably activating an ink jet apparatus including plural groups of ejecting ports each having a different flow rate coefficient by utilizing the pressure applied to the ejecting ports, all the plural groups of ejecting ports being subjected to ejection recovering treatment, wherein the method comprises a step of discharging the ink remaining in the region extending from the plural groups of ejecting ports to predetermined positions in a plurality of ink paths communicated with the plural groups of ejecting ports and a step of allowing ink discharging positions to be dislocated to the predetermined positions in the plurality of ink paths to positionally coincide with the same in the substantially same timing relationship after the ejection recovering treatment starts to be conducted. In other words, a characterizing feature of this method consists in that limitative positions where ink is discharged from an ink path including a common ink chamber communicated with ejecting ports involved in a certain group of ejection ports on the common basis and an ink feeding path from which ink is fed to the common ink chamber are substantially positionally coincident with each other among plural groups of ejection ports. 
     With this construction, e.g., the ink remaining in the ink path extending from the ejecting ports to a joint portion between the ink feeding path and the ink chamber is discharged in the substantially same timing relationship after the ejection recovering treatment starts to be conducted. Otherwise, e.g., the ink remaining in the region extending from the ejecting ports to the joint portion between the ink path and an ink reservoir is discharged in the substantially same timing relationship. 
     In this case, according to the present invention, since the ink reservoir usually has a comparatively large capacity, the aforementioned technical problem does not substantially arise with the ink reservoir. Therefore, it is not necessary that the foregoing part of the ink reservoir is involved in the ink path of the present invention. 
     The ink reservoir serving to feed ink to the ink reservoir can be integrated with the ink jet head. Otherwise, the ink reservoir can be arranged so as to be separated from the ink jet head. It is acceptable that partitioning means for partitioning a group of ejecting ports having a different flow rate coefficient from each other is disposed in the recovering cap. 
     According to the present invention, since a sum of the capacity of the ink feeding path and the capacity of the common chamber is determined depending on the flow rate coefficient of each nozzle, ejection recovering treatment can reliably be conducted for each of the group of ejection ports by performing an ejection recovering operation with the aid of a single recovering cap, whereby a quantity of ink to be uselessly wasted during each ejection recovering operation can be reduced. In other words, a small quantity of ink to be sucked during each ejection recovering operation is discharged from a group of ejecting ports having a small nozzle flow rate coefficient, and moreover, a quantity of ink required for removing air bubbles in ink having an increased viscosity can be reduced. Thus, it is possible to recoverably activate the ink jet head without fail. 
     The above and other objects, effects, features and advantages of the present invention will become apparent from the following description which of embodiments thereof taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of an ink jet head constructed in accordance with an embodiment of the present invention, showing the ink jet head constituting a part of an ink jet recording apparatus in the exploded state; 
     FIG. 2 is a perspective view of the ink jet recording apparatus to which the present invention is applied, showing by way of example an appearance of the ink jet recording apparatus; 
     FIG. 3 is a perspective view which shows an appearance of each of the ink jet head and a recovering cap; 
     FIG. 4 is a sectional view of the ink jet head, showing that the latter is held in the capped state; and 
     FIG. 5 is a sectional view of an ink jet head constructed in accordance with another embodiment of the present invention wherein the ink jet head constitutes a part of the ink jet recording apparatus. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will now be described in detail hereinafter with reference to FIG. 1 to FIG. 5 which illustrate preferred embodiments thereof. 
     FIG. 2 is a perspective view of an ink jet recording apparatus to which the present invention is applied, showing that a cartridge type ink jet head is installed in the ink jet recording apparatus. 
     As shown in FIG. 2, an ink jet head  120  is mounted on a carriage  116 . This ink jet head  120  includes plural arrays of nozzles  103   b ,  103   c ,  103   m  and  103   y  each of which serves to eject ink to the recording surface of a recording paper conveyed by a platen  124  while facing to the latter. The carriage  116  is supported by two guide shafts  115  and  119  extending in parallel to each other so as to enable it to be slidably displaced along the guide shafts  115  and  119 . The carriage  116  is operatively connected to a part of an endless driving belt  118  for transmitting the driving power generated by a driving motor  117  to the carriage  116 . In addition, the carriage  116  is arranged in such a manner as to enable the ink jet head  120  to be reciprocably displaced within the range defined by the full width of the recording paper. 
     The ink jet recording apparatus includes an ejection recovering unit  126  which is disposed at the position located to one end of the displacement path of the ink jet head  120 , e.g., a home position of the latter. The ejection recovering unit  126  performs a capping operation for the ink jet head  120  via a power transmitting mechanism  123  adapted to transmit the driving power generated by a motor  122  to the ejection recovering unit  126 . The ejection recovering unit  126  includes a recovering cap  126 I which serves to suck ink from the ink jet head  120  during a capping operation performed for the ink jet head  120  with the aid of suitable sucking means disposed in the ejection recovering unit  126  or pump ink to the ink jet head  120  with the aid of suitable pressuring means disposed in an ink path in order to forcibly discharge (expel) ink from a plurality of ejecting ports  111 . With this construction, the ejection recovering unit  126  executes ejection recovering treatment for removing the ink having an increased viscosity from each nozzle  103 . It should be added that the ink jet head  120  is protected from deterioration of its performances by performing a capping operation for the ink jet head on completion of each recording operation. 
     A blade  130  for a wiping member molded of a silicone rubber or the like is disposed on the side wall of the ejection recovering unit  126 . This blade  130  is held by a blade holding member  131  in the cantilever-like state. Similar to the ejection recovering unit  126 , the blade  130  is actuated by the motor  122  and the power transmitting mechanism  123 . The blade  130  can come in slidable contact with an ejection surface of the ink jet head  120 . Specifically, the blade  130  is projected into the displacement path of the ink jet head  120  at a suitable time during a recording operation performed by the ink jet head  120  or after completion of the ejection recovering treatment in order to remove dew, moisture, dust particles on the ejection surface of the ink jet head  120  by a wiping operation of the blade  130  performed as the ink jet head  120  is reciprocably displaced in that way. 
     FIG. 3 is a perspective view which shows an appearance of each of the ink jet head  120  and the recovering cap  126 I. In the case that the ink jet head  120  is kept unused for a long time, resulting in the viscosity of ink in the nozzles  103   b ,  103   c ,  103   m  and  103   y  and in common ink chambers  104   b ,  104   c ,  104   m  and  104   y  being increased or in the case that air bubbles introduced into the ink jet head  120  from a joint portion at the time of replacement of an ink reservoir  112  with another one are removed from the ink jet head  120 , the recovering cap  126 I comes in close contact with the ejection surface of the ink jet head  120 . Subsequently, a pump (not shown) is driven to suck ink from the ink jet head  120 , causing the latter to be subjected to ejection recovering treatment. At this time, a small quantity of ink is sucked from color ink nozzles  103   c ,  103   m  and  103   y  each having a small flow rate coefficient compared with black ink nozzle  103   b . However, since common ink chambers  104   c ,  104   m  and  104   y  and ink feeding paths  106   c ,  106   m  and  106   y  from which ink is sucked have a small inner capacity, respectively, it is possible to recover not only the black nozzle  103   b  but also the color ink nozzles  103   c ,  103   m  and  103   y  by performing the same recovering operations as mentioned above. 
     On the assumption that a differential pressure is designated by p, a cross-sectional area of the nozzle  103  is designated by F, a density of ink is designated by ρ and a flow rate of ink is designated by Q, a flow rate coefficient of the nozzle  103  designated by α is represented by the following equation (1). 
     
       
         α= Q/{F ·(2 p /ρ) ½ }  (1) 
       
     
     When a sum of the inner capacity of the common ink chamber  104 , the inner capacity of each ink feeding path  106  and the inner capacity of the nozzle  103  is designated by S, it is necessary that the condition as defined by an inequality of Q&gt;S is satisfactorily established. 
     FIG. 1 is a partially exploded perspective view which shows the structure of an ink jet head  120  constructed in accordance with an embodiment of the present invention. This ink jet head  120  is constructed such that a plurality of heat generating resistors  101 , a plurality of electrodes  102  and a plurality of protective layers (not shown) are successively laminated one above another by employing a spattering process, a CVD process, an electron beam irradiating process or the like, and thereafter, the nozzle  103  and the common ink chambers  104  are formed by employing a photoetching process. An ink feeding port  105  is formed through a ceiling plate of each common ink chamber  104 . Ink is fed to each common ink chamber  104  from an ink reservoir  112  via an ink feeding path  106  communicated with the ink feeding port  105 . In the shown case, the ink jet head  120  includes four common ink chambers  104   b ,  104   c ,  104   m  and  104   y  which are communicated with ink reservoirs  112  for black ink, cyan ink, magenta ink and yellow ink. Thus, each different colored inks are ejected from nozzles  103   b ,  103   c ,  103   m  and  103   y  communicated with the four common ink chambers  104   b ,  104   c ,  104   m  and  104   y . Especially, the nozzle  103   b  is used for ejecting black ink therefrom. This black ink nozzle  103   b  is designed to eject a liquid droplet having a volume larger than that of each of the other color ink nozzles  103   c ,  103   m  and  103   y . For example, an ink jet head  120  capable of recording 360 dots per inch (d.p.i.) is employed for practicing this embodiment, and a volume assumed by each liquid droplet of black ink ejected from the ink jet head  120  is determined to range from about 65 to 95 pico liters (p.l.), preferably from about 75 to 85 p.l. On the other hand, a volume assumed by a liquid droplet of each of cyan ink, magenta ink and yellow ink ejected from the same is determined to range from 30 to 50 p.l., preferably 32 to 45 p.l. in consideration of shooting of liquid droplets onto a recording medium in the overlapped state. An example of dimensions employed for designing each nozzle  103  advantageously usable for ejecting liquid droplets each having the foregoing volume is shown in Table 1. 
     
       
         
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                 dimensions of 
                 dimensions 
                   
               
               
                   
                   
                 each nozzle 103 
                 of ejection 
                 number 
               
               
                   
                 dimensions 
                 (width × height 
                 port (width 
                 of 
               
               
                 color 
                 of heater 
                 × length) 
                 × height) 
                 nozzles 
               
               
                 of ink 
                 unit : μm 
                 unit : μm 
                 unit : μm 
                 103 
               
               
                   
               
             
             
               
                 black 
                 40 × 100 
                 55 × 33 × 300 
                 35 × 33 
                 64 
               
               
                 color 
                 20 × 105 
                 50 × 33 × 300 
                 25 × 33 
                 24 for 
               
               
                   
                   
                   
                   
                 each 
               
               
                   
                   
                   
                   
                 color 
               
               
                   
               
             
          
         
       
     
     FIG. 4 is a schematic sectional view which shows the state that the ink jet head  120  shown in FIG. 1 is capped with the recovering cap  126 . An inner capacity of each of the common color ink chambers  104   c ,  104   m  and  104   y  is set to about 3 mm 3 . An inner capacity of the common ink chamber  104   b  for black ink is set to about 7.5 mm 3 . An inner capacity of each of color ink feeding paths  106   c ,  106   m  and  106   y  for feeding color inks to the common ink chambers  104   c ,  104   m  and  104   y  from the color ink reservoir  112 C is set to 1.8 mm 3 . In addition, an inner capacity for the black ink feeding path  106   b  is set to 3.6 mm 3 . Additionally, foreign material trapping means for trapping dust particles, air bubbles or the like may be disposed at the intermediate position of each ink feeding path  106  or at one end of the same. 
     To assure that the recovering cap  126 I elastically comes in close contact with the outer edge of the ejecting surface of the ink jet head  120 , it is molded of a rubber-like elastic material such as a silicone rubber or the like. A rectangular rib having a width of about 0.3 mm is projected from the front surface of the recovering cap  126 I in order to improve the close contact state between the ink jet head  120  and the recovering cap  126 I when the whole ejection surface of the ink jet head  120  is covered with the ink jet head  120 . In addition, a suction hole  108  is formed through the recovering cap  126 I. A suction tube  109  is connected to the suction hole  108 . A waste ink absorbing block  110  is disposed in front of the suction hole  108 . This waste ink absorbing block  110  serves to absorb the ink droplets remaining in the recovering cap  126 I. The ink jet head  120  includes a plurality of ejection ports  111   y ,  111   m ,  111   c  and  111   b  which are arranged in accordance with the order of yellow ink, magenta ink, cyan ink and black ink as seen from above in FIG. 4. A distance between adjacent arrays of nozzles among plural arrays of nozzles  103   y ,  103   m ,  103   c  and  103   b  is set to be wider than a normal nozzle pitch. The suction tube  109  is connected to a pump (not shown). 
     In this embodiment, the ink reservoir  112  is designed in a two-reservoir system composed of a black ink reservoir  112 B and a color ink reservoir  112 C. The interior of the color ink reservoir  112 C is divided into three sections, one of them being a section for cyan ink, other one being a section for magenta ink and another one being a section for yellow ink. The color ink reservoir  112 C may be designed to exhibit an integral structure like in this embodiment. Otherwise, it may be designed in a separate type including a plurality of sections separated from each other corresponding to the number of ink colors. Usually, the ink reservoirs  112  are mounted on the carriage  116  together with the ink jet head  120 . Otherwise, these ink reservoirs  112  are arranged independently from the carriage  116 , and the ink reservoirs  112  and the ink jet head  120  are connected to each other via ink feeding tubes extending therebetween. 
     The foregoing embodiment has been described above with respect to the ink jet head  120  including plural arrays of nozzles  103  mounted on a common base plate  100 . Alternatively, the plural arrays of nozzles  103  may distributively be formed on a plurality of base plates. 
     FIG. 5 is a sectional view which shows an ink jet head constructed in accordance with another embodiment of the present invention. 
     In this embodiment, the ink jet head includes a recovering cap  126 II which is divided into a cap portion for color inks and a cap portion for black ink with a partition rib  113  disposed therebetween. Suction holes  108 B and  108 C communicated with suction tubes  109 B and  109 C are formed through the foregoing two cap portions. Waste ink absorbing blocks  110 B and  110 C are disposed in front of the suction holes  108 B and  108 C. Each of the waste ink absorbing blocks  110 B and  110 C serves to absorb the ink droplets remaining in the recovering cap  126 II. The suction tubes  109 B and  109 C are connected to a common pump (not shown) via an adapter  114  and a pump tube  115  extending between the adapter  114  and the pump. The partition rib  113  is effective not only for preventing black ink and color inks from being mixed with each other but also for preventing other kind of ink from entering the nozzle  103 . It desirable that the partition rib  113  in the recovering cap  126 II exhibits a complete partitioning function. It should be noted that the partition rib  113  is practically effective for preventing inks from being mixed with each other even though it exhibits an insufficient partitioning effect. 
     Also with respect to the recovering cap  126 II constructed in the above-described manner, a quantity of ink ejected from each of the color ink nozzles  103   c ,  103   m  and  103   y  each having a small flow rate efficient is small compared with that of the black ink nozzle  103   b . However, since an inner capacity of each of the common color ink chambers  104   c ,  104   m  and  104   y  and the color ink feeding paths  106   c ,  106   m  and  106   y  each having necessity for sucking ink from the former is designed to be correspondingly small, it is possible to recoverably activate not only the black ink nozzle  103   b  but also the color ink nozzles  103   c ,  103   m  and  103   y  every time suction recovering treatment is executed. 
     Especially, among various types of ink jet recording systems, the ink jet head constructed in accordance with this embodiment exhibits advantageous effects when it is employed for a recording head and a recording apparatus each operable in accordance with an ink jet system wherein jetting liquid droplets are formed by utilizing thermal energy to perform a recording operation therewith. 
     With respect to a typical structure and a principle of operation of the ink jet recording system, it is recommendable that reference is made to U.S. Pat. Nos. 4,723,129 and 4,740,796 each of which discloses the fundamental principle of the foregoing system. This system is applicable either of a so-called on-demand type and a continuous type. Especially, in the case that the on-demand type is employed, thermal energy is generated in each electrothermal transducer by applying at least one driving signal to the electrothermal transducer disposed corresponding to a sheet of porous material or a liquid passage having ink received therein so as to quickly elevate the present temperature in excess of a level of inducing a phenomenon of nuclear boiling based on the recording informations, causing a phenomenon of film boiling to appear on the heating portion of an ink jet head. This leads to a desirable result that an ink vapor bubble is formed in ink in the one-to-one relationship in response to a driving signal. As the ink vapor bubble thermally grows and contracts, ink is ejected through an ejection port to form at least one liquid droplet. Since the ink vapor bubble is adequately grown and contracted when the driving signal is prepared in the form of a pulse, the ink can be ejected from the ink jet head with excellent responsiveness. 
     With respect to the pulse-shaped driving signal, it is recommendable that reference is made to U.S. Pat. Nos. 4,463,359 and 4,345,262 each of which discloses an acceptable shape of each pulse. In addition, when the conditions as disclosed in U.S. Pat. No. 4,313,124 are employed in operative association with a temperature elevation rate of the heating portion of the ink jet head, each recording operation can be achieved with more excellent results. 
     With respect to the structure of the ink jet head, it is recommendable that reference is made to U.S. Pat. Nos. 4,558,333 and 4,459,600 each of which discloses the technical concept that the heating portion of the ink jet head is disposed in the bent region thereof, in addition to the combined structure made among ejection ports, liquid passages (linearly extending liquid passages or liquid passages extending at a right angle relative to two liquid passage portions thereof) and electrothermal transducers as disclosed in the official gazettes of the first-mentioned U.S. patents. It should be noted that the technical concept disclosed in the foregoing prior inventions is involved in the present invention. 
     In addition, with respect to the structure of a plurality of electrothermal transducers, it is recommendable to reference is made not only to Japanese Patent Application Laying-Open No. 59-123,670 which discloses the structure that a common slit serves as an ejecting portion of each electrothermal transducer but also to Japanese Patent Application Laying-Open No. 59-138,461 which discloses the structure that an opening portion for absorbing a series of pressure waves induced by the thermal energy is formed corresponding to the ejecting portion so as to allow the ink jet head of the present invention to be constructed with advantageous effects. 
     Additionally, the present invention is advantageously applicable to a so-called full-line type recording head having a width corresponding to a maximum recording width. This type of recording head may be constructed such that the whole length of the recording head is composed of a plurality of recording heads to be combined with each other. Alternatively, the recording head may be constructed such that the whole length of the recording head is composed of a length of a single recording head designed in an integral structure. 
     Further, the present invention is advantageously applicable to an exchangeable tip type ink jet head constructed such that it can electrically be connected to a main body of the ink jet apparatus, and moreover, ink can be fed to the ink jet head from the main body of the ink jet head. Further, the present invention is likewise advantageously applicable to a cartridge type ink jet head integrated with an ink reservoir. 
     In each of the aforementioned embodiments of the present invention, description has been made on the assumption that ink to be ejected from the ink jet head is prepared in the form of a liquid. Alternatively, the ink may be prepared such that it is kept solid at a room temperature or at a temperature lower than the room temperature but it is softened or liquidized at the room temperature or less. Since the temperature of the ink is usually controlled in conformity with the ink jet recording system such that the viscosity of the ink is maintained within the stable ink ejecting range by properly regulating the temperature of the ink itself within the range of 30° C. or more to 70° C. or less, the ink may be prepared such that it is kept liquid when a recording operation start command signal is inputted into the ink jet head. 
     In addition, to prevent the temperature of the ink from being excessively raised up in excess of a predetermined temperature by utilizing the thermal energy for changing the solid state of the ink to the liquid state of the same or to prevent the ink from being vaporized, it is preferable that the ink is prepared such that it is kept solid while it is not practically used. At any rate, the present invention can be applied to the case that ink is liquidized on receipt of the thermal energy in response to a recording operation start command signal so as to allow liquid ink to be ejected from the recording head or the case that each ink droplet starts to be solidified when it is shot onto a recording medium. 
     Further, according to the present invention, it is acceptable that the ink jet apparatus is practically used as an image output terminal apparatus for an information processing device such as a word processor, a computer or the like. Additionally, the ink jet apparatus may be constructed in the type of a copying machine electrically combined with an optical reader or a facsimile apparatus having a signal sending/receiving function. 
     While the present invention has been described above with respect to a few preferred embodiments thereof, it should of course be understood that the present invention should not be limited only to these embodiments but various changes or modification may be made without departure from the scope of the present invention as defined by the appended claims.