Abstract:
A power takeoff having an output shaft, an output gear and a connect-disconnect clutch mechanism for connecting the output gear to the output shaft, the clutch mechanism, including a clutch hub, a disc stack slidably mounted between the output gear and the clutch hub and a piston for compressing the disc stack thereby to bring the output shaft into rotatable engagement with the transmission of an engine; in which the clutch hub is normally biased by a spring away from the piston but is confined by snap rings to limit the hub&#39;s movement along the output shaft in such a manner so that substantially no operational force is placed on the snap rings during compression of the disc stack.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to an ink-jet printhead, and more particularly to an ink-jet printhead provided with a filter for removing foreign matter from ink.  
         [0002]     Japanese Patent Application Provisional Publication HEI 9-314836 discloses an ink-jet printhead having a laminated structure and actuated by a piezoelectric actuator on demand. The disclosed ink-jet printhead is constructed from substantially six plates stacked together in a laminated body. Assuming that the uppermost plate is the first plate and the lowermost one the sixth plate, the second plate sandwiched between the first and third plates is formed with a plurality of small openings that function as pressure generating chambers. The fifth plate sandwiched between the fourth and sixth plates is provided with a plurality of large openings that define common ink supply chambers.  
         [0003]     The common ink supply chambers are filled with ink supplied from an external ink tank, which ink is then distributed to the plurality of pressure generating chambers through ink channels formed in the third and fourth plates.  
         [0004]     Each pressure generating chamber is in fluid communication with a corresponding one of a plurality of nozzle orifices formed in the sixth plate or the lowermost plate. Further, a piezoelectric vibration plate is fixed on the top surface of the first plate so as to selectively compress each pressure generating chamber. When one of the pressure generating chambers is compressed, an ink droplet ejects from the nozzle orifice corresponding to the compressed pressure generating chamber.  
         [0005]     The fourth plate is provided with recesses that are formed at areas facing the common ink supply chambers. These recesses isolate vibration generated by the piezoelectric vibration plate.  
         [0006]     An ink supply channel is formed in the laminated body of the ink-jet printhead through which ink from the external ink tank flows into the common ink supply chambers. Generally, a separate plate-like filter is attached to the inlet of the ink supply channel for removing foreign matter from the ink flowing into the common ink supply chambers, since such foreign matter might clog up the nozzle orifices of the printhead. The filter is an essential component of the ink-jet printhead. However, it increases the component count of the ink-jet printhead, and also requires additional work for attaching it to the ink-jet printhead.  
         [0007]     Therefore, there is a need for an ink-jet printhead that does not require attaching a filter thereto for filtering ink supplied from an external ink tank.  
       SUMMARY OF THE INVENTION  
       [0008]     The present invention is advantageous in that an ink-jet printhead is provided that satisfies the above mentioned need.  
         [0009]     An ink-jet printhead according to an aspect of the invention includes a cavity unit and an actuator stacked together. The cavity unit is provided with a row of nozzle orifices and a row of pressure chambers communicating with the respective nozzle orifices. The actuator has a plurality of active portions for selectively actuating the respective pressure chambers to eject ink through the respective orifices. The cavity unit is a stack of plates including a cavity plate formed with the pressure chambers, a manifold plate formed with a manifold chamber and an intervenient plate interposed between the cavity plate and the manifold plate. The manifold chamber supplies ink from an external ink supply source to each of the pressure chambers. The intervenient plate is formed with a filter portion which filters ink provided from the external ink supply source to the manifold chamber. The intervenient plate is formed with a damper wall facing the manifold chamber. The damper wall has a partial thickness of the intervenient plate.  
         [0010]     In the ink-jet printhead arranged as above, it is not necessary to additionally attach a separate ink filter to the ink-jet printhead since the intervenient plate includes a filter portion. Thus, the ink-jet printhead can be easily assembled.  
         [0011]     Optionally, the damper wall defines a recess on a side of said intervenient plate opposite from the manifold plate. Further optionally, the recess may be sealed with a base plate interposed between the cavity plate and the intervenient plate.  
         [0012]     Optionally, the intervenient plate may be formed with a plurality of restricting channels which bring the pressure chambers in fluid communication with the manifold chamber. The restricting channels may be tapered from the manifold chamber toward the respective pressure chamber. A base plate may be further interposed between the cavity plate and the intervenient plate, which base plate is formed with a plurality of ink channels that bring the restricting channels in fluid communication with the respective pressure chambers.  
         [0013]     Optionally, the filter portion may be formed in a locally thin region of the intervenient plate. Further optionally, the filter portion may include a plurality of small holes penetrating the intervenient plate in the locally thin region.  
         [0014]     Optionally, the ink-jet printhead may further comprise a cover plate stacked on a side of the manifold plate opposite from the intervenient plate, so that the manifold chamber can be defined by an opening formed through the manifold plate and sandwiched between the intervenient plate and the cover plate.  
         [0015]     When the intervenient plate includes the filter portion, the damper wall, and a plurality of restricting channels, the plurality of restricting channels and the filter portion may be arranged outside the damper wall.  
         [0016]     In the above case, both of the manifold chamber and the damper wall may be formed in elongated shapes so that the manifold chamber extends, at its lengthwise end, beyond the damper wall, and the filter portion is formed at a position corresponding to the lengthwise end of the manifold chamber.  
         [0017]     Alternatively, both of the manifold chamber and the damper wall may be formed in elongated shapes and the restriction channels may be arranged along an outer side edge of the damper wall, in a lengthwise direction of the manifold chamber to fall within an outer region of the manifold chamber, and the damper wall may overlap an inner region of the manifold chamber.  
         [0018]     In an ink-jet printhead according to another aspect of the invention is provided with a plurality of nozzle orifices, a plurality of pressure chambers, and a common ink chamber. The plurality of nozzle orifices are formed on one surface of the ink-jet print head. The plurality of pressure chambers are in fluid communication with respective ones of the nozzle orifices. Each pressure chamber is filled with ink and selectively pressurized to eject the ink from a corresponding one of the nozzle orifices. The common ink chamber is filled with ink to be supplied to the pressure chambers. The ink channel extends from the common ink chamber to supply therethrough ink from an external ink supply source.  
         [0019]     The ink-jet print head is further provided with a substrate placed between the plurality of pressure chambers and the common ink chamber so as to damp pressure wave propagating from the pressure chambers toward the common ink chamber. An ink filter is integrally formed in the substrate and disposed in the ink channel to remove foreign matter from the ink flowing into the common ink chamber.  
         [0020]     The ink filter may include a plurality of through holes formed in the substrate in a cluster. Further, the substrate may have a recess on one side thereof, and the plurality of through holes may be formed in a portion of the substrate defining the recess. In some cases, the recess is formed on a side of the substrate from which the ink from the external ink supply source enters the ink filter.  
         [0021]     The plurality of through holes may be formed by laser ablation. In this case, the substrate may be made of synthetic resin. The recess may be formed by plasma etching.  
         [0022]     Optionally, the substrate may have a low stiffness region which has a lower mechanical stiffness than a remaining portion of the substrate. The low stiffness region may extend over the plurality of pressure chambers. Such low stiffness region can be formed as a recess on one side of the substrate, for example. 
     
    
     BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS  
       [0023]      FIG. 1  is an exploded perspective view of a cavity unit of an ink-jet printhead according to an embodiment of the invention;  
         [0024]      FIGS. 2 and 3  are enlarged cross-sectional views of the ink-jet printhead according to the embodiment of the invention taken along lines II-II and III-III of  FIG. 1 , respectively; and  
         [0025]      FIG. 4  is an enlarged perspective view of a part of an intervenient plate of the ink-jet print head shown in  FIGS. 2 and 3 . 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0026]     Hereinafter, an piezoelectric type ink-jet printhead  100  according to an embodiment of the invention will be described with reference to the accompanied drawings.  
         [0027]      FIG. 1  is an exploded perspective view of a cavity unit  102  of the ink-jet printhead  100 .  FIGS. 2 and 3  are enlarged cross-sectional views of the ink-jet printhead  100  taken along lines II-II and III-III of  FIG. 1 , respectively.  
         [0028]     As shown in  FIGS. 2 and 3 , the ink-jet printhead  100  includes a plate type piezoelectric actuator  104  mounted on the top of the cavity unit  102 . The piezoelectric actuator  104  is connected with an external controller (not shown) through a flexible flat cable (not shown) connected to the upper surface of the piezoelectric actuator  104 . The ink-jet printhead  100  is configured so as to eject ink downwards therefrom through a plurality of nozzle orifices  106  open toward the bottom of the cavity unit  102 .  
         [0029]     As shown in  FIG. 1 , the cavity unit  102  is formed from a plurality of thin plates, i.e., a cavity plate  108 , a base plate  110 , an intervenient plate  112 , two manifold plates  114  and  116 , a cover plate  118 , and a nozzle plate  120 , which are adhered to each other in a laminated stack in this order from the top. In the present embodiment, the intervenient plate  112  and the nozzle plate  120  are made of synthetic resin, such as polyimide resin, while the other plates ( 108 ,  110 ,  114 ,  116 ,  118 ) are made of 42% nickel steel to a thickness of about 50 μm to about 150 μm. It should be noted, however, the intervenient plate  112  and the nozzle plate  120  may also be made of metal.  
         [0030]     As will be described hereinafter, the above-mentioned plates of the cavity unit  102  are provided with openings and recesses which are formed by means of electrolytic etching, plasma etching, excimer laser ablation, or the like.  
         [0031]     The nozzle plate  120  is provided with two rows of staggered nozzle orifices  106  extending in the lengthwise direction of the nozzle plate  120 . In each row, the nozzle orifices  106  are located at regular intervals. Each nozzle orifice is formed in small diameter, which is about 25 μm in the present embodiment.  
         [0032]     The cavity plate  108  is provided with two rows of staggered pressure chambers  122 . As shown in  FIG. 2 , each of the pressure chambers  122  is positioned in association with the corresponding nozzle orifice  106 . Each pressure chamber  122  is oriented with one end in the lengthwise direction thereof nearer to the center of the cavity plate  108  and the other end nearer to the outside of the cavity plate  108 . Note that the former end will be referred to hereinafter as a center side end  122   a  and the later as an outside end  122   b . The center side end  122   a  of each pressure chamber  122  is in fluid communication with the corresponding nozzle orifice  106  through an ink channel  124  that is formed by through holes provided in the base plate  110 , the intervenient plate  112 , the two manifold plates  114  and  116 , and the cover plate  118 . The outside end  122   b  of each pressure chamber  122  is in fluid communication with corresponding one of a pair of manifold chambers  126  through a through hole  128 , or an ink channel, formed in the base plate  110  and a restricting channel  130  formed in the intervenient plate  112 . Each restricting channels  130  are formed such that the cross section thereof gradually decreases toward the base plate  110 .  
         [0033]     The pair of manifold chambers  126 , which function as common ink chambers, are defined by openings ( 114   a ,  114   b ,  116   a  and  116   b ) formed in the two manifold plates  114  and  116 . The pair of manifold chambers  126  is located on both sides of the rows of the nozzle orifices  106  (or the rows of ink channels  124 ). As shown in  FIG. 1 , each of the pair of manifold chambers  126  has an elongated form that extends in the direction of the row of the nozzle orifices  106  or the row of the pressure chambers  122 . Each of the manifold chambers  126  is placed below the corresponding row of the pressure chambers  122 . One end  126   a  of each of the manifold chambers  126  extends in the lengthwise direction from the corresponding row of the pressure chambers  122 .  
         [0034]     As shown in  FIG. 2 , the upper surface of each manifold chamber  126  is defined by the undersurface of the intervenient plate  112  adhered to top of the upper manifold plate  114 . The bottom of each manifold chambers  126  is defined by the top surface of cover plate  118  adhered to the undersurface of the lower manifold plate  114 .  
         [0035]     Referring to  FIGS. 1 and 2 , a pair of elongated recesses (damper chambers)  132  are formed in the intervenient plate  112  on the side facing the base plate  110 . The bottom of each recess  132  is a thin wall which will be referred to hereinafter as damper wall  112   a . The recesses  132  have substantially the same length as the rows of the pressure chambers  122  and extend below the rows of the pressure chambers  122 . In other words, the recesses  132  are located between the rows of the pressure chambers  122  and the manifold chambers  126  so that the damper walls  112   a  form part of the upper walls of respective manifold chambers  126 . Note that the recesses  132  do not extend up to the ends  126   a  of the manifold chambers  126 .  
         [0036]     Each recess  132  has a shorter width (dimension in the direction perpendicular to the lengthwise direction thereof) than the corresponding manifold chamber  126 . Each recess  132  is located such that the side edges of the recess  132  and the manifold chamber  126  nearer to the ink channels  124  are aligned with each other. As shown in  FIG. 2 , the side edge of each recess  132  that is opposite from the ink channels  124  is displaced from the corresponding side edge of the corresponding manifold chamber  126 , providing a space for forming the row of restricting channels  130  in the intervenient plate  112  along the lengthwise direction of the recess  132 . Thus, the restricting channels  130  are in fluid communication with the manifold chamber  126  in the vicinity of the side thereof opposite from the ink channels  124 .  
         [0037]     Referring to  FIG. 1 , the intervenient plate  112  is provided with a plurality of staggered through holes, which are part of the ink channels  124 , at substantially the middle of the intervenient plate  112  in the width direction, or at a region between the pair of the recesses  132 . Further, the intervenient plate  112  is formed with a pair of filter portions  134  located near one end thereof in the lengthwise direction.  
         [0038]      FIG. 4  is an enlarged perspective view of a part of the intervenient plate  112 . As shown in  FIG. 4 , each of the pair of filter portions  134  includes a recessed thin-walled portion  134   a  provided with a plurality of small filter holes  134   b  penetrating the thin-wall portion  134   a.    
         [0039]     In the present embodiment, the recess  132  and the thin-wall portion  134   a  of the intervenient plate  112  are formed by means of plasma etching, while the restricting channel  130  and the filter holes  134   b  of the filter portion  134  are formed by laser ablation using excimer laser. Plasma etching and laser ablation allow simultaneous forming of the recess  132  and the thin-walled portion  134   a , and simultaneous forming of the through holes for the ink channels  124 , the restricting channels  130  and the filter holes  134   b , which in turn allows forming the small restricting channels  130  and the small filter holes  134   b  at accurate positions and in precise forms. Note that the restricting channels  130  should be formed precisely since they are required to supply a sufficient amount of ink to the pressure chambers  122  from the manifold chambers  126  while preventing ink from flowing back into the manifold chambers  126  due to the pressure wave generated within the pressure chambers  122 . Further, the accurately positioned holes and recesses (the through holes for the ink channels  124 , the recesses  132 , the restricting channels  130  and the filter holes  134   b ) in the intervenient plate  112  facilitate the alignment of the intervenient plate  112  with the base plate  110  and the manifold plates  114  and  116 .  
         [0040]     Referring now to  FIGS. 1 and 3 , the filter portions  134  are formed so as to be located above the ends  126   a  of the manifold chambers  126 . The cavity plate  108  and the base plate  110  placed above the intervenient plate  112  are formed with a pair of through holes  136   a  and a pair of through holes  136   b , respectively, at positions corresponding to the filter portions  134 . The through holes  136   a  and  136   b  form two ink supply channels  136  extending upwardly from respective filter portions  134 .  
         [0041]     Ink from an external ink supply source (not shown) is provided into both of the ink supply channels  136  from the top thereof. The ink passes through each filter portion  134  by which foreign matter, such as dust, is removed therefrom. Then, the ink flows into the pair of manifold chambers  126  and is distributed to the pressure chambers  122  through the restriction channels  130  and the through holes  128  (see  FIG. 2 ). Further, the ink flows from the pressure chambers  122  into the corresponding ink channels  124  and finally reaches the corresponding nozzle orifices  106 .  
         [0042]     The piezoelectric actuator  104  has substantially the same configuration as that disclosed in Japanese Patent Application Provisional Publication No. P2001-162796, the disclosure of which is hereby incorporated by reference. The piezoelectric actuator  104  includes a stack of a plurality of piezoelectric sheets (not shown). Each piezoelectric sheet has a thickness of about 30 μm. A plurality of narrow separate electrodes (not shown) is printed on the upper surface of every two piezoelectric sheets at positions corresponding to the pressure chambers  122 . Further, a common electrode is printed on the upper surface of each of the remaining piezoelectric sheets, which common electrode is shared among the above-mention plurality of separate electrodes. The common electrodes and the separate electrodes are electrically connected with a plurality of connection terminals (not shown) formed on the top surface of the uppermost piezoelectric sheet through conductive lines (not shown) formed to extend vertically on a side wall of the piezoelectric actuator  104 . The plurality of connection terminals are further connected with the conductive lines of the previously mentioned flexible flat cable.  
         [0043]     If voltage is applied between the common electrode and selected one of the separate electrodes, the portion of the piezoelectric actuator  104  therebetween, which will be referred to hereinafter as active portion, deforms in the direction the piezoelectric sheets are stacked. By selectively deforming the active portion, the volume of the corresponding pressure chamber  122  can be reduced which causes an ink droplet to be ejected from the corresponding nozzle orifice  106 .  
         [0044]     The deformation of the piezoelectric actuator generates a pressure wave in the pressure chamber  122 . The pressure wave includes not only a forward component that propagates toward the corresponding nozzle orifice  106  but also a backward component that propagates toward the manifold chambers  126  or the common ink chambers.  
         [0045]     As may be understood from  FIG. 2 , the backward component of the pressure wave propagates through the through hole  128 , the restriction channel  130 , and the manifold chamber  126 . Since the damper wall  112   a  is a thin wall, it has a lower mechanical stiffness than the remaining portion of the intervenient plate  112  and can resiliently deform. Thus the damper wall  112   a  vibrates in accordance with the pressure wave and thereby effectively absorbs the pressure wave. Further, the air sealed in the recess (damper chamber)  132  of the intervenient plate  112  by the base plate  110  also damps the pressure wave propagating therethrough. Thus, the pressure wave that affects the other pressure chambers  122  becomes quite week, and does not cause the so called cross-talk between the pressure chambers  122 .  
         [0046]     The vibration of the damper wall  112   a  causes a change in the volume of the recess (damper chamber)  132 . This change, however, does not affect the volume of the pressure chambers  126  nor cause deformation of cavity plate  108  since the base plate  110  having a constant thickness and appropriate stiffness is interposed between the intervenient plate  112  and the cavity plate  108 , or between the recesses (damper chambers)  132  and the pressure chambers  122 . Accordingly, the vibration of the damper walls  112   a  of the intervenient plate  112  does not affect the ink ejection property of the ink-jet printhead which may deteriorate the printing quality.  
         [0047]     As shown in  FIG. 1 , the plurality of the restricting channels  130  and the pair of filter portions  134  of the intervenient plate  112  are arranged outside each recess  132  and along the periphery of each recesses (damper chamber)  132 . More specifically, each row of the restricting channels  130  are formed adjacent to the side edge of the corresponding recess  132  on the side opposite from the rows of the ink channels  124  so as to extend along that side edge, or in the lengthwise direction of the corresponding recess  132 . Further, each filter portion  134  is located adjacent to one end of the corresponding recess  132  in the lengthwise direction thereof. This reasonable arrangement allows the pair of recesses  132 , the pair of filter portions  134 , and the rows of restricting channels  130  to be formed in a small area of the intervenient plate  112  while keeping dimensions of the recess (damper chamber)  132  or the damper wall  112   a  sufficiently large to obtain a high damping effect.  
         [0048]     It may be appreciated from the description herein above that since the recesses (damper chamber)  132 , the restricting channels  130 , the filter portions  134 , and the ink channels  124  are all formed in one intervenient plate  112 , the above-mentioned holes or recesses can be formed in precise shapes and at accurate relative positions. The precisely shaped and accurately positioned holes and recesses in the intervenient plate  112  facilitate the alignment of the intervenient plate with other plates, such as the base plate  110  and the manifold plates  114  and  118 , at the time of assembling the cavity unit  102 , and also reduce the alignment error between the plates.  
         [0049]     Further, since the filter holes  134   b  are formed in the thin-walled portion  134   a  of the filter portion  134 , the effective area of the filter portion  134  does not decrease even if the base plate  110  is stacked onto the intervenient plate  112  without being accurately aligned with the intervenient plate  112 . In addition, since the thin-walled portion  134   a  is relatively thin, the plurality of filter holes  134   b  can be formed in a short time and hence the manufacturing efficiency of the ink-jet print head can be enhanced. Further, unlike the case where a separate filter is disposed on the intervenient plate  112  to underlie the through hole  136 , no undesirable clearance is created between the intervenient plate  112  and the base plate  110  because the filter portion  124  is formed integrally in the intervenient plate  112 .  
         [0050]     The manifold chambers  126  are designed to have a same thickness as the overall thickness of the two manifold plates  114  and  116 . Thus, the manifold chambers  126  with an accurate depth can be made by simply forming openings in the two manifold plates  114  and  116  and piling up them on the cover plate  118  which forms the bottom of the manifold chambers  126 .  
         [0051]     In the intervenient plate  112 , the plurality of the restricting channels  130  and the pair of filter portions  134  are arranged around the recesses (damper chamber)  132 . This reasonable arrangement allows the pair of recesses  132 , the pair of filter portions  134 , and the rows of nozzle like channels  130  to be formed in a small area of the intervenient plate  112  while keeping the recess (damper chamber)  132  or the damper wall  112   a  sufficiently large to obtain a high damping effect thereby.  
         [0052]     While the invention has been described in detail with reference to specific embodiments thereof, it would be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention, the scope of which is defined by the attached claims.  
         [0053]     For example, the two manifold plates  114  and  116  may be replaced with a thick single manifold plate, or with a stack of three or four thin manifold plates.  
         [0054]     Further, the single piezoelectric actuator  104  may be replaced with a plurality of small separate piezoelectric actuators fixed on the cavity unit  102  at positions corresponding to respective pressure chambers  122 . Further more, the actuator  104  for providing pressure to the pressure chambers  122  are not limited to piezoelectric type actuators but any other suitable type of actuators may be utilized.  
         [0055]     The present disclosure relates to the subject matter contained in Japanese Patent Application No. P2002-273478, filed on Sep. 19, 2002, which is expressly incorporated herein by reference in its entirety.