Abstract:
An ink jet print head is provided which includes: a print element substrate; a plate accommodating the print element substrate by enclosing a side peripheral portion of the print element substrate; an electric wiring tape member disposed on the plate and having electric wiring portions for the print element substrate; a first sealant filling a space surrounding the print element substrate enclosed by the plate; and a second sealant covering a part of the electric wiring portions. In this construction, stress concentrations in the electric connections are alleviated even if the electric wiring tape used to support the second sealant has a reduced stiffness due to a reduced thickness of the tape. For this purpose, the plate H 1401 ′ is provided with protrusions H 1402  as support members that support the second sealant H 1308  through the extension portions H 1305  of the electric wiring tape.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an ink jet print head that ejects ink onto a surface of a print medium to form an image and more particularly to an ink jet print head having a flexible film substrate mounted on a substrate formed with print elements to generate energy for ejecting ink. 
   2. Description of the Related Art 
   An ink jet printing system generally comprises an ink jet print head having nozzles or ejection openings to eject ink and a supply system to supply ink to the print head. 
     FIGS. 1 to 3  are perspective views showing a representative example of an ink jet print head. This construction basically can properly apply the present invention described later. 
   An ink jet print head H 1000  generally comprises a print element unit H 1002 , an ink supply unit H 1003  and a tank holder H 2000 . As shown in  FIG. 3 , the print element unit H 1002  has a first print element substrate H 1100 , a second print element substrate H 1101 , a first plate H 1200  used as a base, an electric wiring tape H 1300  serving as a flexible wiring member, an electric contact substrate H 2200 , and a second plate H 1400  for accommodating the print element substrates. These are assembled and mounted on the ink supply unit H 1003 . The ink supply unit H 1003  has an ink supply member H 1500 , a flow path forming member H 1600 , a joint seal member H 2300 , a filter H 1700  and a seal rubber H 1800 . These are assembled and accommodated in the tank holder H 2000 . 
   Here, the construction of the print element unit H 1002  will be explained. 
   The print element unit H 1002  is generally manufactured in the following processes. 
   Process 1: Forming a plate assembly by joining the first plate H 1200  and the second plate H 1400 . 
   Process 2: Mounting two print element substrates H 1100  and H 1101  on the plate assembly. 
   Process 3: Positioning electrode terminals H 1302  of the electric wiring tape H 1300  and electrode portions of the print element substrates, and joining the electric wiring tape to the plate assembly. 
   Process 4: Connecting the electrode terminals H 1302  of the electric wiring tape H 1300  and the electrode portions of the print element substrates. 
   Process 5: Sealing the electrical connections. 
   Each of the above processes will be detailed in the following. 
   Process 1 
   The first plate H 1200  is formed with ink supply ports H 1201  to supply a black ink to the first print element substrate H 1100  and cyan, magenta and yellow inks to the second print element substrate H 1101 . The second plate H 1400  is joined to the first plate H 1200  in a way that exposes the ink supply ports H 1201 . Where the ink supply ports H 1201  are exposed, the second plate H 1400  joined to the first plate H 1200  is formed with device holes H 1401  to accommodate the two print element substrates H 1100 , H 1101 . 
   Process 2 
   The first print element substrate H 1100  and the second print element substrate H 1101  are securely bonded with high precision to the exposed portions of the first plate H 1200  through the device holes H 1401 . The positioning of the first and second print element substrates is made with respect to an X-direction positional reference surface H 1204  and a Y-direction positional reference surface H 1205  both formed in the first plate H 1200 . The print element substrates each having a plurality of ink ejection openings have a known construction employed in an ink jet print head. 
   Process 3 
   The electric wiring tape H 1300  is a laminate of a base film, copper foil wires and a wire protecting cover film or solder resist. The base film may, for example, be formed of a polyimide resin to a thickness of about 25–125 μm. The copper foil wires have a thickness of 35 μm and are formed in a predetermined shape to connect the two print element substrates to the electric contact substrate H 2200 . Portions of the electric wiring tape H 1300  that the print element substrates are built into, are formed with device holes H 1304  of almost the same shape as the device holes H 1401 . At two sides of each of the device holes H 1304  which correspond to the electrode portions of the print element substrates, electrode terminals H 1302  plated with gold on their surface are arrayed as connection terminals. The electric wiring tape H 1300  is secured on its cover film side to the surface of the second plate H 1400  through a thermosetting epoxy resin bonding layer. The base film of the electric wiring tape H 1300  is made smooth on its surface as it is engaged with a capping member of the print element unit. 
   Process 4 
   Electric connection between the electric wiring tape H 1300  and the two print element substrates is made by performing an inner lead bonding (abbreviated ILB) on the electrode terminals H 1302  of the electric wiring tape H 1300  and bumps provided in advance on the electrode portions of the print element substrates, for example. 
   Process 5 
   When the electric connections are exposed after ILB, the electrode portions are covered and sealed with a sealant H 1308  ( FIG. 2 ) with excellent sealing and ion interruption capabilities, such as epoxy resin, because fine ink sprays flying from ejection openings or ink drops bouncing back from a print medium may adhere to the electrode portions, corroding the electrode portions and base metals. To form liquid-tight ink communication paths running from the ink supply ports H 1201  to ejection openings H 1107 , the surrounding of each print element substrate and gaps between the print element substrates and the device holes are covered with a sealant H 1307 . 
   The sealant (first sealant) H 1307  applied to the surroundings of the print element substrates is chosen to have a high fluidity and a high elasticity so that the sealant when hardened will not cause stresses such as hardening shrinkage to the print element substrate. The other sealant (second sealant) H 1308  applied to the electric connections is chosen to have a high hardness to provide such properties as wear resistance against rubbing motions of a rubber wiper blade to wipe off ink drops adhering to an ejection opening forming face and durability against being flaked off should a print medium contact it. 
   Then, the electric terminal contact member H 1303  on an electric input side of the electric wiring tape H 1300  and the electric contact substrate H 2200  to transfer electric signals from the printing apparatus body are connected together by, for instance, an ACF (Anisotropic Conductive Film) and the terminal connection portions are also covered with a sealant. 
   The print element unit H 1002  assembled in the above processes and the ink supply unit H 1003  are joined together through the joint seal member H 2300 . Screws H 2400  are fastened into screw fixing bosses H 1517  in the ink supply unit H 1003  through screw setting positions H 1207  provided in two screw setting portions H 1206  of the first plate. At this time, the positional reference surfaces H 1204 , H 1205  of the first plate and its back surface engage abutment portions H 1509 , H 1510 , H 1511  of the ink supply unit H 1003 . This positions the print element unit H 1002  in the X direction (main scan direction), Y direction (sub-scan direction) and Z direction (ink ejection direction). The electric contact substrate H 2200  is positioned and fixed by a terminal positioning pins H 1515  and terminal connecting pins H 1516  of a terminal fixing portion H 1512  of the ink supply unit H 1003  coming into terminal positioning holes H 1309  and terminal connecting holes H 1310  of the electric contact substrate. 
   Then, the tank holder H 2000  is mounted on the assembly of the print element unit H 1002  and the ink supply unit H 1003  to provide an ink jet print head H 1000  of  FIG. 1 . When ink tanks (not shown) are installed in the tank holder H 2000 , ink is supplied from the filter H 1700  of the ink supply unit H 1003  into the ink paths H 1501  in the flow path forming member H 1600 . Ink is further fed from an ink introducing port H 1602  into the print element unit H 1002 . 
   Although the ink jet print head described above has a black ink ejection portion and a color ink ejection portion formed integral as one piece, the similar manufacturing process can also be applied to an ink jet print head with separate print element substrates for individual colors. 
   The ink jet print head, however, has the following problems that may degrade reliability. 
   As described above, the second sealant H 1308  that covers the electric connections between the electric wiring tape H 1300  and the print element substrates is hard and highly durable. Thus, where the second sealant H 1308  is placed over the soft first sealant H 1307 , which seals the outer periphery of the print element substrates, may be cracked when applied a local external force as the first sealant H 1307  deforms. From these cracks ink may seep in, leading to corrosion of electric connections. 
   To solve this problem, a method has been proposed (see Japanese Patent Application Laid-open No. 2002-187273) which involves extending the base film of the electric wiring tape H 1300  at both ends of the arrays of the electrode terminals H 1302  slightly into the device holes and applying the second sealant H 1308  over the extension portions H 1305  so as to cover the electric connections. This document also discloses that the extension portions H 1305  may have a conductive layer to particularly enhance stiffness. 
   SUMMARY OF THE INVENTION 
   As the ink jet printing apparatus have come into widespread use, there is a growing demand for a reduction in cost of the print head used in the apparatus. To meet this demand, it is essential to lower the cost of elements making up the print head. When the base film and the copper foil layer making up the electric wiring tape H 1300 , which are relatively expensive parts, are reduced in thickness as part of the cost reduction effort, it is highly unlikely that the above-mentioned problem cannot be avoided completely with the above construction left unchanged. 
   This problem will be explained by referring to  FIG. 4A  and  FIG. 4B .  FIG. 4A  schematically illustrates the electric wiring tape and device hole and their associated parts in the print element unit, as seen from a side where arrays H 1108  of ink ejection openings H 1007  are formed (surface opposing a print medium).  FIG. 4B  is a schematic cross section taken along the line IVB—IVB of  FIG. 4A . 
   As shown in  FIG. 4A , when a technique disclosed in Japanese Patent Application Laid-open No. 2002-187273 is applied, the base film of the electric wiring tape H 1300  is extended toward both ends of arrays of the electrode terminals H 1302  of the tape connected to the electrode portions H 1104  of the first print element substrate H 1100  in such a way as to cover parts of space between the first print element substrate H 1100  and the device hole H 1401 , with the second sealant H 1308  covering the electric connections and the extension portions H 1305 . 
   However, when the first sealant H 1307  deforms (e.g., due to hardening shrinkage) as shown in  FIG. 4B , the extension portions H 1305  at the corners of the device hole H 1304  of the electric wiring tape H 1300  also deform toward the bottom of the device hole as indicated by arrows. Since the second sealant H 1308  is hard, it cannot follow the deformation, causing local stress concentrations, degrading connection stability. 
   In light of the problem described above, the present invention has been accomplished to provide a highly reliable ink jet print head that clears the above problem. 
   The print head of this invention therefore comprises: 
   a print element substrate disposed on a base and having print elements for ejecting ink and electrode portions to receive a power supply for driving the print elements; 
   an accommodating unit to accommodate the print element substrate by enclosing a side peripheral part of the print element substrate, the accommodating unit being mounted on the base; 
   a resilient wiring member disposed on the accommodating unit and having wiring portions formed thereon to be connected to the electrode portions of the print element substrate; 
   a first sealant filling a space surrounding the print element substrate enclosed by the accommodating unit; 
   a second sealant covering the electrode portions of the print element substrate and a part of the wiring portions of,the wiring member corresponding to the electrode portions; and 
   a support member situated in the space to support the second sealant on the base. 
   With this invention stress concentrations in the electric connections which are feared to occur as a result of reducing the thickness of the base film and copper foil layer making up a wiring member such as an electric wiring tape, which are the relatively expensive wiring member, can be alleviated thereby enhancing the reliability. The provision of the support member that supports the second sealant can improve the reliability and manufacturing stability of the connecting portions between the print element substrate and the wiring member even if the wiring member is reduced in thickness to lower the cost. Particularly if protrusions are provided inside the device hole, which defines the print element substrate accommodating space in the accommodating unit (second plate) that can be formed of a relatively inexpensive material, the number of parts does not increase nor does the part cost rise. Therefore it is possible to provide a highly reliable ink jet print head at low cost. 
   The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of an example ink jet print head that can apply the present invention; 
       FIG. 2  is an exploded, perspective view of a print element unit, an ink supply unit and a tank holder, main constitutional components of the ink jet print head of  FIG. 1 ; 
       FIG. 3  is a further exploded, perspective view of each of the print element unit and the ink supply unit of  FIG. 2 ; 
       FIG. 4A  and  FIG. 4B  are, respectively, a schematic view of an electric wiring tape and a device hole and their associated components of the conventional print element unit, as seen from a side facing a print medium, and a schematic cross section taken along the line IVB—IVB of  FIG. 4A ; 
       FIG. 5  is an exploded perspective view of a print element unit according to a first embodiment of this invention; 
       FIG. 6A  and  FIG. 6B  are, respectively, a schematic view of an electric wiring tape and a device hole and their associated components of the print element unit of  FIG. 5 , as seen from a side facing a print medium, and a schematic cross section taken along the line VIB—VIB of  FIG. 6A ; 
       FIG. 7  is a perspective view showing a construction of a first print element substrate of the ink jet print head that can apply the present invention; 
       FIG. 8  is a perspective view showing a construction of a second print element substrate of the ink jet print head that can apply the present invention; 
       FIG. 9  is a schematic perspective view showing an example construction of an ink jet printing apparatus using the ink jet print head applying this invention; 
       FIG. 10  is an exploded perspective view of a print element unit according to a second embodiment of this invention; 
       FIG. 11  is an exploded perspective view of a print element unit according to a third embodiment of this invention; and 
       FIG. 12  is an exploded perspective view of a print element unit according to a fourth embodiment of this invention. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   Now, the present invention will be described in detail by referring to the accompanying drawings. 
   First Embodiment 
     FIG. 5  is an exploded perspective view of a print element unit according to the first embodiment of this invention.  FIG. 6A  is a schematic view showing an electric wiring tape and a device hole and their associated parts in the print element unit as seen from a side where arrays H 1108  of ink ejection openings H 1007  of the first print element substrate H 1100  are formed (a surface facing a print medium).  FIG. 6B  is a schematic cross sectional view taken along the line VIB—VIB of  FIG. 6A . In these figures, parts identical with those of  FIGS. 1 to 3 ,  FIG. 4A  and  FIG. 4B  are assigned like reference numerals. 
   This embodiment differs from the construction of  FIG. 4A  and  FIG. 4B  in that protrusions H 1402  corresponding to the device hole extension portions H 1305  of the electric wiring tape H 1300  are provided at four corners of each device hole in the second plate H 1400 ′ for the first and second print element substrate H 1100  and H 1101 . The protrusions H 1402  may be formed integral with the second plate H 1400 ′ when the second plate H 1400 ′ is molded from a base material such as ceramic, resin or metal. With this embodiment, this was achieved easily and at low cost by modifying a punched alumina (Al 2 O 3 ) green sheet. 
   Using the second plate H 1400 ′ formed in this manner, the print element unit H 1002  is assembled in the process described above, so that the device hole extension portions H 1305  of the electric wiring tape are supported by the protrusions H 1402  of the second plate, as shown in  FIG. 6B . Thus, if the first sealant H 1307  undergoes hardening shrinkage, the above construction prevents a generation of a force which would otherwise deflect the extension portions H 1305  downward and thereby deform the second sealant H 1308 . Thus, no local stress concentrations occur in the electric connections between the print element substrates and the electric wiring tapes, protecting the connection stability. As a result, a highly reliable ink jet print head can be provided. 
   In this embodiment, the extension portions H 1305  are provided on the electric wiring tape side to support the second sealant H 1308 . In this construction the extension portions H 1305  are formed to positively protrude toward the electric connections to ensure that a step at the end of the electric wiring tape is not situated near the periphery of the sealant H 1308 , thereby making the step coverage of the sealant H 1308  stable and satisfactory. If the peeling of the sealant H 1308  due to such a step does not become an issue, the extension portions H 1305  may not be provided on the electric wiring tape side and instead the protrusions H 1402  of the second plate can be directly covered with the sealant H 1308 , i.e., the protrusions H 1402  of the second plate can directly support the sealant H 1308 . This can also be said of second and third embodiment. 
   While this embodiment has almost square protrusions H 1402  at corners of the device hole H 1401 ′ of the second plate H 1400 ′, the shape of the protrusions is not limited to this one as long as they can effectively support the device hole extension portions H 1305  of the electric wiring tape or the second sealant H 1308 . For example, their square edge portions may be chamfered in an inclined surface or in a curved surface. The protrusions of such shapes can still be molded easily and as one piece with the second plate and produce the similar effect. 
   The second plate H 1400 ′ does not affect the construction of other parts of the print element unit and thus does not require significant changes in the basic design and manufacturing process of the print element unit. Therefore, for the print element substrates H 1100  and H 1101  the known construction of the ink jet print head can be employed. The construction of the print element substrates will be briefly explained referring  FIGS. 7 and 8 . 
     FIG. 7  shows the first print element substrate H 1100  for a black ink.  FIG. 8  shows the second print element substrate H 1101  for color inks. Both of the print element substrates are formed of a silicon substrate H 1110  0.5–1 mm thick having ink supply paths H 1102  one for each color in the form of a long groovelike through-hole, to which the associated inks are introduced from the ink introducing port H 1602  ( FIG. 3 ) of the ink supply unit H 1003 . Further, on each side of the ink supply path H 1102  of each color is arranged an array of electrothermal transducers H 1103  as ejection energy generation means, with the two electrothermal transducer arrays staggered from each other by one-half pitch in the Y direction. At positions corresponding to the electrothermal transducers there are liquid paths formed by ink path walls H 1106  and arrays H 1108  of ink ejection openings H 1107  communicated with the liquid paths and adapted to eject ink onto a print medium. The second print element substrate H 1101  for color inks has integrally formed therein all columns of ejection openings for three colors, yellow, magenta and cyan, with two columns used for each color. The ejection opening columns for individual colors may also be formed in separate pieces. 
   Further, along two sides of the print element substrate in a direction (X direction in the figure) perpendicular to the direction of array of the electrothermal transducers H 1103  (Y direction in the figure) are formed electrode portions H 1104  for connecting the electrothermal transducers formed on the first print element substrate and a drive circuit built into the first print element substrate with external circuits. In the electrode portions H 1104  ball bumps (stud bumps) H 1105  of Au, for example, are formed as by a wire bonding device for connection with the electrode terminals H 1302  of the electric wiring tape H 1300 . 
   Means for generating ink ejection energy are not limited to the electrothermal transducers, which, when energized, generate thermal energy to heat and create a bubble in ink, and other forms of energy generation means may be employed. 
   The print head H 1100  assembled by using the print element unit H 1002  constructed as shown in  FIG. 5  can be mounted on printers, copying machines, facsimiles with a communication system and word processors with a printer unit, and also on industrial printing devices used in combination with a variety of processing devices. By using this ink jet print head, it is possible to print on a variety of print media, such as paper, threads, fibers, cloth, leather, metal, plastics, glass, wood, and ceramics. Word “print” in this specification means imparting to print media not only images having significance or meaning such as letters and figures, but also images with no meaning such as patterns. 
     FIG. 9  is a schematic perspective view showing an example construction of an ink jet printing apparatus using the ink jet print head described above. In this apparatus, a carriage  500  is fixed to an endless belt  501  and is movable along a guide shaft  502 . The endless belt  501  is wound on pulleys  503 , one of which is connected with a drive shaft of a carriage drive motor  504 . Thus, as the motor  504  is operated, the carriage  500  is reciprocally driven (in direction A) along the guide shaft  502  for a main scan. On the carriage  500  is mounted the cartridge type ink jet print head H 1000  which is attached with the same number of ink tanks  404  as the ink colors used. 
   This apparatus has a linear encoder  506  to detect a position of the carriage in the main scan direction. The linear encoder  506  has as one constitutional element a linear scale  507  provided along the direction of travel of the carriage  500  which is formed with slits at a predetermined density and at equal intervals. The linear encoder  506  has as the other constitutional element a slit detection system  508  having a light emitting portion and a light sensor and a signal processing circuit. Thus, as the carriage  500  moves, the linear encoder  506  outputs an ejection timing signal for determining an ink ejection timing and carriage position information. 
   Paper P as a print medium is intermittently fed in a direction B perpendicular to the scan direction of the carriage  500 . The paper P is supported by a pair of roller units  509 ,  510  situated upstream in the direction of paper transport and by a pair of roller units  511 ,  512  situated downstream and is given a predetermined tension by these rollers to secure a flatness or planarity with respect to an ejection opening forming face of the print element unit H 1002  as it is transported. A driving force to each roller unit is transmitted from a paper feed motor not shown. 
   In the above construction, the printing over the same width as the length of the ejection opening arrays of the ink jet print head while the carriage  500  moves and the feeding of paper P are repetitively alternated until the whole paper P is printed. 
   The carriage  500  stops at a home position as required at a print start time or during a printing operation. At this home position is provided a cap member  513  that caps the ejection opening forming face of each ink jet head (in which ejection openings are formed). The cap member  513  has a suction-based recovery means (not shown) to forcibly suck out ink from ejection openings to prevent possible clogging of the ejection openings. At the home position a wiping member  550  to wipe clean the ejection opening forming face of the print element unit H 1002  is arranged vertically movable. 
   Second Embodiment 
     FIG. 10  is an exploded perspective view of a print element unit according to a second embodiment of this invention. In the figure, parts identical with those of  FIG. 1  to  FIG. 3 ,  FIG. 4A  and  FIG. 4B  are given like reference numbers. 
   This embodiment differs from the construction of  FIG. 5  in that while the second plate H 1400  is used which has the device holes H 1401  of the same shapes as shown in  FIG. 4A  and  FIG. 4B , support members H 1403  of the same height as the depth of the device holes H 1401  of the second plate are arranged at four corners of each of the device holes H 1401  of the first and second print element substrates H 1100 , H 1101  so that they are situated below the device hole extension portions H 1305  of the electric wiring tape. In this example, small cubic support members H 1403  (0.6 mm×0.6 mm×0.6 mm) are formed of acrylic material and, after the first and second plates H 1200 , H 1400  have been assembled together, are bonded to the four corners of each of the device holes H 1401 . 
   In other steps, the print element unit H 1002  is assembled in the similar manner to have the device hole extension portions H 1305  of the electric wiring tape supported on the support members H 1403 . Thus, if the first sealant H 1307  undergoes hardening shrinkage, the downward deflection of the extension portions H 1305  can be blocked, preventing local stress concentrations in the electric connections between the print element substrate and the electric wiring tape, thereby maintaining the connection stability. It is therefore possible to provide a highly reliable ink jet print head. 
   Third Embodiment 
     FIG. 11  shows a third embodiment as a variation of the second embodiment. In this example, on a back side of the device hole extension portions H 1305  of the electric wiring tape, i.e., on the side facing the device holes H 1401 , acrylic support members H 1403  of the same thickness as the depth of the device hole are arranged to produce the similar effect to that of the second embodiment. 
   In other steps the print element unit H 1002  is assembled in the similar manner to have the device hole extension portions H 1305  of the electric wiring tape supported on the support members H 1403 . Thus, if the first sealant H 1307  undergoes hardening shrinkage, the downward deflection of the extension portions H 1305  can be blocked, preventing local stress concentrations in the electric connections between the print element substrate and the electric wiring tape, thereby maintaining the connection stability. It is therefore possible to provide a highly reliable ink jet print head. 
   It is noted that the shape of the support members is not limited to the cube or the like as long as they can effectively support the device hole extension portions H 1305  of the electric wiring tape or the second sealant H 1308 . The material of the support members is also not limited to acrylics but may use inexpensive and easily formed materials, such as metal, ceramics and easily molded resin. 
   Fourth Embodiment 
     FIG. 12  is an exploded perspective view of a print element unit according to a fourth embodiment of this invention. In this embodiment, while the second plate H 1400  having the device holes H 1401  of the same shapes as shown in  FIG. 4A  and  FIG. 4B  is used, those protruding portions of the electric wiring tape at the extension portions H 1305  are folded toward the back side, i.e., toward the device hole H 1401  of the second plate H 1400  to form folded portions H 1306  which are used as support members to support the device hole extension portions H 1305  of the electric wiring tape or the second sealant H 1308 . The size of the folded portions is set to 0.6 mm, equal to the height of the device holes H 1401 . This arrangement ensures that if, after the assembly is done as described above, the first sealant H 1307  undergoes hardening shrinkage, the tips of the folded portions H 1306  support the electric wiring tape and blocks its downward deflection, preventing local stress concentrations in the electric connections between the print element substrate and the electric wiring tape, thereby maintaining the connection stability. It is therefore possible to provide a highly reliable ink jet print head. 
   The size of the folded portions may be set otherwise. That is, the front ends of the folded portions H 1306  need not completely contact the upper surface of the first plate H 1200 . The folded portions H 1306  can be sized to allow deformation of the electric wiring tape to such a degree that no undesirable local stress concentrations occur in the electric connections between the electric wiring tape and the print element substrate. 
   The present invention has been described in detail with respect to preferred embodiments, and it will now be apparent from the foregoing to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspect, and it is the intention, therefore, in the apparent claims to cover all such changes and modifications as fall within the true spirit of the invention. 
   This application claims priority from Japanese Patent Application No. 2003-415727 filed Dec. 12, 2003, which is hereby incorporated by reference herein.