Abstract:
In a system and method for using a wiper to clean a nozzle plate of an inkjet head, a spring is disposed between the wiper and a mounting body, and the mounting body has a top portion and a bottom portion. The wiper is disposed proximate the top portion of the mounting body relative to the bottom portion of the mounting body. In addition, the wiper blade is transported across the face of a nozzle plate for wiping portions of the nozzle plate. A distance between the wiper blade and the bottom end of the mounting body is varied in accordance with variations in distances between the portions of the nozzle plate and the bottom portion of the mounting body.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims the benefit of Cyman, Jr. et al., U.S. Provisional Patent Application No. 61/762,713, filed on Feb. 8, 2013, and entitled “Apparatus and Method for Wiping an Inkjet Cartridge Nozzle Plate.” The entire contents of such application are incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    1. Field of the Disclosure 
         [0003]    The present disclosure relates generally to inkjet printing systems and more particularly to an apparatus and method for wiping a nozzle plate of an inkjet cartridge used in such printing systems. 
         [0004]    2. Description of the Background of the Disclosure 
         [0005]    High-speed printing systems typically include one or more imaging units. Each imaging unit has one or more inkjet cartridges and a controller controls each inkjet cartridge to eject a fluid (such as ink or other composition) onto a receiving surface. Each inkjet cartridge includes a nozzle plate that includes a plurality of orifices (nozzles) through which ink from inside the inkjet cartridge may be controllably ejected. 
         [0006]    An inkjet cartridge typically includes a fluid chamber and one or more nozzles. Pressure inside of the fluid chamber is increased relative to ambient air pressure to force a drop of fluid through the nozzle(s). One type of inkjet cartridge uses a piezoelectric element that deforms a wall of the fluid chamber to reduce the volume thereof and thereby increase the pressure within the fluid chamber. Alternately, a heating element may be used to vaporize some of the fluid (or a constituent of the fluid such as a fluid carrier or a solvent) in the fluid chamber to form a bubble therein, which increases the pressure inside the fluid chamber. A controller controls the current that is passed through the piezoelectric element to control the deformation thereof or to control the current through the heating element in turn to control the temperature thereof so that drops are formed when needed. Other types of inkjet technologies known in the art may be used in the printing systems described herein. 
         [0007]    In a printing system, an inkjet cartridge is secured to a carrier and disposed such that the nozzles of the inkjet cartridge are directed toward the receiving surface. The carrier may be manufactured from steel or other alloys that can be milled to a high precision. More than one inkjet cartridge may be secured to a carrier in this fashion in a one or two-dimensional array. 
         [0008]    Dried ink, dust, paper fibers, and other debris can collect on a nozzle plate or in a nozzle of an inkjet cartridge and prevent proper ejection of ink from the nozzles thereof. The controller of a printing system can undertake periodic cleaning cycles during which ink is purged from the nozzle to release any debris in or near such nozzle. The purged ink and/or debris must be removed from the nozzle plate in the vicinity of the nozzles so that such purged ink and/or debris does not collect thereon and dry to create further debris that will later interfere with ejection of ink from nozzles of the cartridge. 
       SUMMARY 
       [0009]    According to one aspect of the present disclosure, an apparatus to clean a nozzle plate of an inkjet head includes a wiper blade, a mounting body, a spring, and a controller. The mounting body has a top portion and a bottom portion, the top portion being closer to the wiper blade than the bottom portion. The spring is disposed between the wiper blade and the bottom portion of the mounting body. A first portion of the spring is coupled to the wiper blade and a second portion of the spring is coupled to the mounting body. Compression of the spring varies, thereby varying a distance between the wiper blade and the bottom portion of the mounting body, as the wiper blade is transported across a face of the nozzle plate to clean the nozzle plate. 
         [0010]    According to another aspect of the present disclosure, a method for using a wiper to clean a nozzle plate of an inkjet head includes the step of transporting the wiper blade across the face of a nozzle plate for wiping portions of the nozzle plate. A spring is disposed between the wiper blade and a mounting body, wherein a top portion of the mounting body is closer to the wiper blade than a bottom portion of the mounting body. The method includes the further step varying a distance between the wiper blade and the bottom portion of the mounting body in accordance with variations in distances between the portions of the nozzle plate and the bottom portion of the mounting body. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a plan view of a cleaning unit of a printing system; 
           [0012]      FIG. 2  is an isometric view of a wiper used in the cleaning unit of  FIG. 1 ; 
           [0013]      FIGS. 3A and 3B  are a sectional views taken generally along the lines  3 - 3  of  FIG. 2 ; 
           [0014]      FIG. 4  is an exploded view of the wiper of  FIG. 2 ; 
           [0015]      FIGS. 5A-5C  are a sectional views of another wiper used in the cleaning unit of  FIG. 1 ; and 
           [0016]      FIG. 5D  is a plan view of a wiper holder of the wiper of  FIGS. 5A-5C . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0017]    Provisional U.S. Patent Application Ser. No. 61/685,002, filed Mar. 9, 2012, discloses a printing system that includes a printing unit and a cleaning unit, the entire contents of such application are incorporated herein by reference. The printing unit includes a carrier onto which a plurality of inkjet cartridges is disposed. Referring to  FIG. 1 , one embodiment of the cleaning unit  102  includes a wiper unit  302 , a cleaning bay  306 , and a wiper wash unit  312 . 
         [0018]    The wiper unit  302  includes a plurality of wipers  304  for wiping a nozzle plate of an inkjet cartridge. Some or all of the wipers  304  disclosed in the above-identified Provisional U.S. Patent Application Ser. No. 61/685,002 may be replaced by the wiper disclosed herein. Referring to  FIG. 2  of the present application, one embodiment of a wiper  304  includes a wiper blade  506  extending outwardly from a mounting body  556 . A mounting plate  512  disposed at a bottom end of the mounting body  556  includes screw holes  514  that are used to attach the mounting plate  512  (and therefore the wiper  304 ) to a mounting structure of the wiper unit  302 . The wiper  304  also includes a port  510  that descends downwardly therefrom. Such port  510  may be connected to a fluid line through which a pressurized fluid, for example, air, may be supplied. 
         [0019]    Referring to  FIG. 3A , in one embodiment, the wiper blade  506  is attached to a wiper blade holder  548  and the wiper blade holder  548  is attached to a top bar  550  of a leaf spring  552 . It should be apparent that the wiper blade  506  may be attached directly to the top bar  550  of the leaf spring  552 . A bottom bar  554  of the leaf spring  552  is attached to a threaded shaft  557  of the wiper  304 . In one embodiment, a bolt  557  secures the bottom bar  554  to the threaded shaft  559 . The wiper blade holder  548  and the leaf spring  552  are disposed atop the mounting body  556 . 
         [0020]    A bolt  560  couples the top bar  550  and the bottom bar  554  of the leaf spring  552 . The bolt  560  is adjusted to pre-compress the leaf spring to limit travel thereof Such pre-compression of the leaf spring prevents the wiper blade  506 , the leaf spring  552 , or any other component of the wiper unit  302  from contacting the nozzle plate  110  of the inkjet cartridge as the wiping unit  302  is when in a non-wiping positions.  FIG. 3A  shows the wiper  304  in a wiping position. As described further below, the wiper blade holder  548  has been urged upward until a wiper blade  506  is in contact with a nozzle plate  110 . Sufficient pressure is applied by the wiper blade  506  to the nozzle plate  110  to compress the leaf spring  552  and thereby move the top bar  550  downwardly toward the bottom bar  554 .  FIG. 3B  shows the wiper  304  when, for example, the wiping unit  302  in a non-wiping position. When the wiping unit  302  is in such non-wiping position, the cylinder  600  of the wiper  304  may be retracted downward toward the mounting  512 . Because the wiper blade is not in contact with the nozzle plate  110 , the leaf spring  552  is released and the top bar  550  is thereby moved upwardly away from the bottom bar  554 . The bolt  560  is adjusted to establish a maximum distance the wiper blade  506  may be displaced by the leaf spring  552  in a direction parallel to a direction C-C. In one embodiment, the bolt  560  is adjusted to provide a maximum displacement of the wiper blade  506  of approximately 0.23 cm (0.09 inches). 
         [0021]    Referring once again to  FIGS. 2 and 3A , in some embodiments, the leaf spring  552  is manufactured from a material that allows the top bar  550  of the leaf spring  552  to exert torque about an axis B-B. In one embodiment, the material of the top bar  550  of the leaf spring  552  is selected so that such top bar  550  may exert up to between approximately 28.35 grams and approximately 70.9 grams (1.0 ounces and 2.5 ounces) of load due to torque about the axis B-B. In some embodiments, the leaf spring is manufactured from stainless steel. It should be apparent that other materials including, for example, another metal alloy, a metal, a plastic, or a polymer may be used to manufacture the leaf spring. 
         [0022]    During operation, securing the wiper blade  506  of the wiper  304  to the leaf spring  552  allows the wiper blade  506  to adjust for variation in the distance between the bottom of nozzle plate  110  being wiped and the mounting plate  512 . Such variation may occur, for example, if the nozzle plate  110  is not perfectly planar or if the plane of the nozzle plate  110  is not parallel to the plane of the mounting plate  512 . The wiper blade  506  can also adjust for differences in the distances between the mounting plate  512  and the nozzle plates  110  of different inkjet cartridges wiped by the wiper blade  506 . Other sources for such variation will be apparent to those having skill in the art. 
         [0023]    Further, attaching the wiper blade  506  of the wiper  304  to the leaf spring  552  allows control over the force exerted by a nozzle plate  110  being wiped on the face  562  of the wiper blade  506  and how much the wiper blade  506  flexes in response to such force. Similarly, the use of the leaf spring  552  in this manner allows control over the wiping force exerted by the wiper blade  506  on the nozzle plate  110  and the amount and viscosity of fluid on the nozzle plate  110  that may be removed by the wiper blade  506 . It should be apparent to those of skill in the art that such control can improve the effectiveness of wiping by the wiper blade  506 , prevent damage to the wiper blade  506 , and prevent damage to the nozzle plate  110  (e.g., because of excessive force applied thereto by the wiper blade  506 ). 
         [0024]    Referring to  FIGS. 3A ,  3 B, and  4 , as noted above, the bolt  557  secures the bottom bar  554  of the leaf spring  552  to a top portion of the threaded shaft  559 . The threaded shaft  559  is threaded to an interior portion of a cylinder  600 . The cylinder  600  extends downwardly into an interior cavity  520  of the mounting body  556  of the wiper  304 . A threaded portion  602  of the cylinder  600  screws into a bolt  604  that is disposed in the interior cavity  520  of the mounting body  556 . An amount of the threaded shaft  559  that is screwed onto the cylinder  600  may be increased or decreased to adjust the distance between the bottom bar  554  and the mounting plate  512 . Such an adjustment is typically undertaken before the wiper  304  is used to wipe the nozzle plate  110  of the inkjet cartridge to establish the resting position of the bottom bar  554  relative to the mounting plate  512 . It should be apparent that adjusting such distance also adjusts the distance between the top portion  562  of the wiper blade  506  and the bottom of the nozzle plate  110  of an inkjet cartridge when the wiper  304  is not being used and is in a retracted position downward toward the mounting plate  512 . In one embodiment, such distance is adjusted to be approximately 0.13 cm (0.05 inches). 
         [0025]    The port  510  is coupled to an output port  516  that opens into the cavity  520 . During operation of the wiper  304 , pressurized fluid is supplied through the port  510  and exhausted via the port  516  into the cavity  520  of the mounting body  556 . The pressurized fluid in the cavity  520  increases pressure within such cavity  520  and urges the cylinder  600  and the bolt  604 , which act as a piston, to move upward in the direction C-C. Such movement of the cylinder  600  and the bolt  604  causes the leaf spring  552  and the wiper  304  secured thereto to rise. The upward movement of the cylinder  600  and the bolt  604  also compresses a spring  606  disposed in the interior of the wiper  304 . A fluid controller (not shown) actuates a source of pressurized gas (not shown) to supply the pressurized fluid to the port  510  to lift the leaf spring  552  and the wiper blade  506  until the wiper blade  506  is at a predetermined distance from the mounting plate  512 . The predetermined height is selected so that the wiper blade  506  at such distance contacts the nozzle plate  110  of an inkjet cartridge with a predetermined force. In one embodiment, such predetermined force is between approximately 28.35 grams and approximately 70.9 grams (1.0 ounce and 2.5 ounces). A motion controller (not shown) thereafter moves the wiper unit  302  and, therefore, the wiper blade  506  across the nozzle plate  110  of the inkjet cartridge to wipe ink and debris therefrom. 
         [0026]    After the wiper  304  has wiped the nozzle plate  110 , the controller causes the pressurized fluid to be released from the cavity  520  through the ports  516  and  510 . It should be apparent to those having skill in the art that the controller may operate one or more valves and/or pumps to release the pressurized fluid from the cavity  520 . Typically, the released fluid is exhausted to the environment or returned to the source of the gas. Releasing the fluid causes the spring  606  to decompress and thereby urge the cylinder  600  and the bolt  604  to move downward. 
         [0027]    In some embodiments, a compression spring disposed inside the mounting body  556  of the wiper  304  may be used instead of the leaf spring  552  to allow the wiper blade  506  to compensate for variations in distance between nozzle plate  110  and the mounting plate  512 . Referring to  FIGS. 5A and 5B , an internal compression spring  608  is disposed between the wiper blade holder  548  and a piston  610 . The wiper blade holder  548  is coupled to a shaft  612  and the shaft  612  is disposed in piston  610 . A setscrew  614  extends from the shaft  612  and is threaded to an interior wall  615  of a cylinder  616  that surrounds both the piston  610  and the shaft  612 . Threading the setscrew  614  in this manner sets the amount of compression load of the internal spring  608 . Referring also to  FIG. 5C , a pin  618  is affixed to the piston  610  and the cylinder  616  includes a slot  620 . The cylinder  616  is disposed so that the pin  610  is positioned within the slot  620 . The pin  618  and the slot  620  act together to limit the maximum upward and downward travel of the cylinder  616  and thereby the shaft  612  in the direction C-C. The pin  618  may also prevent rotation between the shaft  616  and the piston  610  about the axis F-F. The piston  610  may be urged upward and downward as described above and thereby lift or drop the cylinder  616 , the compression spring  608 , the shaft  612 , and the wiper  506 . 
         [0028]    Referring to  FIGS. 5A and 5D , in one embodiment, the wiper blade holder  548  is coupled to a shaft  622  by a pin  624 . The shaft  622  is either integral to or secured to the shaft  612 . The shaft  622  includes a bore through which the pin  624  is passed. In some embodiments, the pin  624  is adjusted to allow the wiper blade holder  548  to rotate about the axis of the pin  624  (i.e., in the direction E-E to further conform to variations in distance between the nozzle plate  110  and the mounting plate  512 ). 
         [0029]    Other types external and/or internal springs may be used to support a wiper blade  506  such that the wiper blade  506  may accommodate variations in the orientation of nozzle plates  110  wiped thereby. 
       INDUSTRIAL APPLICABILITY 
       [0030]    Numerous modifications to the present embodiments will be apparent to those skilled in the art in view of the foregoing description. Accordingly, this description is to be construed as illustrative only and is presented for the purpose of enabling those skilled in the art to make and use the embodiments and to teach the best mode of carrying out same.