Abstract:
A modular printhead assembly facilitates the manufacture of printers with print zones of differing widths. The printhead assembly includes a pair of end pieces and a plurality of rods that extend between the end pieces in parallel. The rods pass through holes in lugs extending from carriers configured for the mounting of printheads. Plates are interposed between the printheads and the carriers to enable actuators to move the plates and printheads within the perimeters of the carriers to adjust the stitch and roll alignments of the printheads.

Description:
TECHNICAL FIELD 
     This disclosure relates generally to inkjet imaging devices, and, in particular, to print bar assemblies in inkjet printers. 
     BACKGROUND 
     In general, inkjet printers include a plurality of printheads that are mounted to a print bar assembly frame. The frame is a unitary die cast structure having two sides with a plurality of bars or rods extending in parallel between the sides. Printheads are then mounted to carriers, which are mounted to the bars at particular positions to provide the appropriate pixel resolution for images generated by the printer. A print zone of a printer is the area within a printer where an ink image is formed for media passing through the printer. In some standard size printers, the print bar assembly is formed to produce images with an 8.5 inch, 24 inch, 36 inch, or 40 inch width. Each different image width requires a different die cast frame. These die cast frames are quite expensive and cannot be adapted to any width other than the print zone width for which the frame was cast. Having print bar assemblies that can be modified to accommodate different image widths would be beneficial. 
     SUMMARY 
     In one embodiment a printer includes a print bar assembly that enables the assembly to be built with different widths without having to obtain different die cast frames. The printer includes a media transport configured to move media through the printer to form an ink image on the media, a first member having three linearly arranged receptacles, a second member having three linearly arranged receptacles, a first rod, a second rod, and a third rod. Each rod has a first end and a second end, the first end of each rod being positioned within one of the receptacles in the first member in a one-to-one correspondence and the second end of each rod being positioned within one of the receptacles in the second member in a one-to-one correspondence to enable the first, the second, and the third rods to extend parallel to one another from the first member to the second member. The printer also includes a first frame having a perimeter, a pair of flanges extending from a first side of the first frame and a third flange extending from a second side of the first frame, the second side of the first frame being opposite the first side of the first frame, each flange extending from the first frame having a hole in the flange, the first rod passing through the holes in the pair of flanges of the first frame and the second rod passing through the hole in the third flange of the first flange. A second frame in the printer has a perimeter, a pair of flanges extending from a first side of the second frame and a third flange extending from a second side of the second frame, the second side of the second frame being opposite the first side of the second frame, each flange extending from the second frame having a hole in the flange, the third rod passing through the hole in the third flange of the second frame and the second rod passing through the holes in the pair of flanges of the second frame. A first printhead is mounted within the first frame, and a second printhead is mounted within the second frame. A controller is operatively connected to the first printhead and the second printhead, and is configured to operate the first printhead and the second printhead to form the ink image for the media. 
     The manufacture of printhead assemblies for producing images of different widths has been facilitated by a modular print bar assembly. The modular print bar assembly includes a first member having three linearly arranged receptacles, a first actuator mounted to the first member between two of the linearly arranged receptacles and a second actuator mounted to the first member between two of the linearly arranged receptacles. The first actuator and the second actuator are not mounted between the same two linearly arranged receptacles. The assembly also includes a second member having three linearly arranged receptacles, and a first rod, a second rod, and a third rod. Each rod has a first end and a second end, the first end of each rod being detachably positioned within one of the receptacles in the first member in a one-to-one correspondence and the second end of each rod being detachably positioned within one of the receptacles in the second member in a one-to-one correspondence to enable the first, the second, and the third rods to extend parallel to one another from the first member to the second member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a depiction of the components of a modular print bar assembly and the different configurations that can be achieved with the modular print bar assembly. 
         FIG. 2A  is a side view of an end member of a modular print bar assembly used in a cut sheet printer or an endless belt intermediate printer. 
         FIG. 2B  is a side view of an end member of a modular print bar assembly used in a web printer or a rotating drum intermediate printer. 
         FIG. 3  is an exploded view of a printhead assembly configured to be mounted to the print bar assembly of  FIG. 1 . 
         FIG. 4A  is a perspective view of a printhead plate mounted to a frame configured for mounting to the print bar assembly of  FIG. 1 . 
         FIG. 4B  is a top view of a printhead plate mounted to a frame shown in  FIG. 4A . 
         FIG. 5  is a perspective view of a printhead mounted to a printhead plate and frame configured for mounting to the print bar assembly of  FIG. 1 . 
         FIG. 6  is a cross-sectional view of the printhead plate and frame taken along lines  6 - 6  in  FIG. 4 . 
         FIG. 7  is a perspective view of the assembly shown in  FIG. 5  from an opposite side. 
         FIG. 8  is a perspective view of an arrangement of printhead assemblies that can be supported by the print bar assembly of  FIG. 1 . 
         FIG. 9  is a perspective view of the arrangement of printhead assemblies shown in  FIG. 8  supported by one of the print bar assemblies shown in  FIG. 1 . 
         FIG. 10  is a perspective view of another arrangement of printhead assemblies that ca be supported by the print bar assembly of  FIG. 1 . 
         FIG. 11  is a perspective view of a link that conjoins adjacent printhead assemblies in the arrangement shown in  FIG. 8 . 
         FIG. 12  is a schematic diagram of a prior art continuous direct-to-media printer. 
     
    
    
     DETAILED DESCRIPTION 
     For a general understanding of the present embodiments, reference is made to the drawings. In the drawings, like reference numerals have been used throughout to designate like elements. As used herein, the terms “printer,” “printing device,” or “imaging device” generally refer to a device that produces an image with one or more colorants on print media and may encompass any such apparatus, such as a digital copier, bookmaking machine, facsimile machine, multi-function machine, or the like, which generates printed images for any purpose. Image data generally include information in electronic form that are rendered and used to operate inkjet ejectors in one or more printheads to form an ink image on the print media. These data may include text, graphics, pictures, and the like. The operation of producing images with colorants on print media, for example, graphics, text, photographs, and the like, is generally referred to herein as printing or marking. 
     The term “printhead” as used herein refers to a component in the printer that is configured with inkjet ejectors to eject ink drops onto an image receiving surface. A typical printhead includes a plurality of inkjet ejectors that eject ink drops of one or more ink colors onto the image receiving surface in response to firing signals that operate actuators in the inkjet ejectors. The inkjets are arranged in an array of one or more rows and columns. In some embodiments, the inkjets are arranged in staggered diagonal rows across a face of the printhead. Various printer embodiments include one or more printheads that form ink images on an image receiving surface. Some printer embodiments include a plurality of printheads arranged in a print zone. An image receiving surface, such as a print medium or the surface of an intermediate member that carries an ink image, moves past the printheads in a process direction through the print zone. The inkjets in the printheads eject ink drops in rows in a cross-process direction, which is perpendicular to the process direction across the image receiving surface. 
     In an indirect printer, the printheads eject ink drops onto the surface of an intermediate image receiving member, for example, a rotating drum or an endless belt. A transfix roller is selectively positioned against the intermediate image receiving member to form a transfix nip. As a media sheet passes through the transfix nip in synchronization with the ink image on the intermediate image receiving member, the ink image transfers and fixes to the media sheet under pressure and heat in the transfix nip. The transfer and fixation of the ink image are well known to the art and are referred to as a transfix process. 
     In a direct printer, the printheads eject ink drops directly onto a print medium, for example, a paper sheet or a continuous media web. After ink drops are printed on the print medium, the printer moves the print medium through a nip formed between two rollers that apply pressure and, optionally, heat to the ink drops and print medium. One roller, typically referred to as a “spreader roller” contacts the printed side of the print medium. The second roller, typically referred to as a “pressure roller,” presses the media against the spreader roller to spread the ink drips and fix the ink to the print medium. 
     For a general understanding of the environment for the system and method disclosed herein as well as the details for the system and method, reference is made to the drawings. In the drawings, like reference numerals have been used throughout to designate like elements.  FIG. 12  depicts a prior-art inkjet printer  5 . For the purposes of this disclosure, an inkjet printer employs one or more inkjet printheads to eject drops of ink onto a surface of an image receiving member, such as paper, another print medium, or an indirect member, such as a rotating image drum or belt. The printer  5  is configured to print ink images with a liquid ink. As used herein, liquid ink refers to melted solid ink, heated gel ink, aqueous inks, ink emulsions, ink suspensions, ink solutions, or the like. 
     The printer  5  includes a controller  50  to process the image data before generating the control signals for the inkjet ejectors to eject colorants. Colorants can be ink or any suitable substance, which includes one or more dyes or pigments and is applied to an image receiving surface to form an ink image. The colorant can be black or any other desired color, and some printer configurations apply a plurality of different colorants to the media. The ink image can be formed on or transferred to media, which includes any of a variety of substrates, including plain paper, coated paper, glossy paper, or transparencies, among others, and the media can be available in sheets, rolls, or other physical formats. 
     The printer  5  is an example of a direct-to-web, continuous-media, inkjet printer that includes a media supply and handling system configured to supply a long (i.e., substantially continuous) web of media  14  of “substrate” (paper, plastic, or other printable material) from a media source, such as spool of media  10  mounted on a web roller  8 . The media web  14  includes a large number (e.g. thousands or tens of thousands) of individual pages that are separated into individual sheets with commercially available finishing devices after completion of the printing process. 
     The printer  5  includes a media transport using one or more actuators, such as electric motors, to rotate rollers that are arranged along the media path that move the media web  14  in the process direction P at a predetermined linear velocity. In the printer  5 , the media web  14  is unwound from the source  10  as needed and a variety of motors, not shown, rotate one or more rollers  12  and  26  to propel the media web  14  in direction P. The media conditioner includes rollers  12  and a pre-heater  18 . The rollers  12  and  26  control the tension of the unwinding media as the media moves along a path through the printer. In alternative embodiments, the printer transports a cut sheet media through the print zone in which case the media supply and handling system includes any suitable device or structure to enable the transport of cut media sheets along a desired path through the printer. The pre-heater  18  brings the web to an initial predetermined temperature that is selected for desired image characteristics corresponding to the type of media being printed as well as the type, colors, and number of inks being used. 
     The media web  14  continues in direction P through the print zone  20  past a series of print bar assemblies  21 A,  21 B,  21 C, and  21 D. Each of the print bar assemblies  21 A- 21 D effectively extends across the width of the media and includes one or more printheads that eject ink directly (i.e., without use of an intermediate or offset member) onto the media web  14 . In printer  5 , each of the printheads ejects a single color of ink, one for each of the colors typically used in color printing, namely, cyan, magenta, yellow, and black (CMYK). 
     The controller  50  of the printer  5  receives velocity data from encoders mounted proximately to the rollers positioned on either side of the portion of the path opposite the four printheads to calculate the linear velocity and position of the web as the web moves past the printheads. The controller  50  uses the media web velocity data to generate firing signals for actuating the inkjet ejectors in the printheads to enable the printheads to eject four colors of ink with appropriate timing and accuracy for registration of the differently colored patterns to form color images on the media. The inkjet ejectors actuated by the firing signals correspond to digital data processed by the controller  50 . The digital data for the images to be printed can be transmitted to the printer, generated by a scanner (not shown) that is a component of the printer, or otherwise generated and delivered to the printer. 
     Associated with each print bar assembly is a backing member  24 A- 24 D, typically in the form of a bar or roll, which is arranged substantially opposite the corresponding print bar assembly on the back side of the media. Each backing member positions the media at a predetermined distance from the print bar assembly opposite the backing member. The various backer members can be controlled individually or collectively. 
     Following the print zone  20  along the media path are one or more “mid-heaters”  30 . A mid-heater  30  can use contact, radiant, conductive, and/or convective heat to control a temperature of the media. The mid-heater  30  brings the ink placed on the media to a temperature suitable for desired properties when the ink on the media is sent through the spreader  40 . 
     Following the mid-heaters  30 , a fixing assembly  40  applies heat and/or pressure to the media to fix the images to the media. The fixing assembly includes any suitable device or apparatus for fixing images to the media including heated or unheated pressure rollers, radiant heaters, heat lamps, and the like. In the embodiment of the  FIG. 5 , the fixing assembly includes a “spreader”  40 , which applies a predetermined pressure, and in some implementations, heat, to the media. The function of the spreader  40  is to flatten the individual ink droplets, strings of ink droplets, or lines of ink on web  14  and flatten the ink with pressure and, in some systems, heat. The spreader flattens the ink drops to fill spaces between adjacent drops and form uniform images on the media web  14 . The spreader  40  includes rollers, such as image-side roller  42  and pressure roller  44 , to apply heat and pressure to the media. 
     The spreader  40  can include a cleaning/oiling station  48  associated with image-side roller  42 . The station  48  cleans and/or applies a layer of some release agent or other material to the roller surface. The release agent material can be an amino silicone oil having viscosity of about 10-200 centipoises. A small amount of oil transfers from the station to the media web  14 , with the printer  5  transferring approximately 1-10 mg per A4 sheet-sized portion of the media web  14 . 
     In printer  5 , the controller  50  is operatively connected to various subsystems and components to regulate and control operation of the printer  5 . The controller  50  is implemented with general or specialized programmable processors that execute programmed instructions. The instructions and data required to perform the programmed functions are stored in a memory  52  that is associated with the controller  50 . The memory  52  stores programmed instructions for the controller  50 . 
     In the controller  50 , the processors, their memories, and interface circuitry configure the controllers and/or print zone to perform the printer operations. These components can be provided on a printed circuit card or provided as a circuit in an application specific integrated circuit (ASIC). Each of the circuits can be implemented with a separate processor or multiple circuits can be implemented on the same processor. Alternatively, the circuits can be implemented with discrete components or circuits provided in VLSI circuits. Also, the circuits described herein can be implemented with a combination of processors, ASICs, discrete components, or VLSI circuits. The controller  50  is operatively connected to the printheads in the printhead units  21 A- 21 D. The controller  50  generates electrical firing signals to operate the individual inkjets in the printhead units  21 A- 21 D to eject ink drops that form printed images on the media web  14 . 
     In the previously known printers, such as the prior art printer  5  shown in  FIG. 1 , the printheads were mounted onto die cast units as noted above and these assemblies could not be configured for different widths of print zones. A new printhead module has been developed that is scalable to enable the width of the print bar to correspond to any number of printheads. Thus, the print bar assembly can be anywhere from one to N printheads provided the rods  108  are long enough to accommodate N printheads. Such a print bar assembly  100  is shown in  FIG. 1 . The assembly  100  is comprised of end members  104  and at least three rods  108 . Each end member  104  includes three linearly arranged receptacles  112  that are configured to receive an end of one of the rods  108 . An actuator  120  is positioned between two consecutive receptacles  112  in one of the end members  104 . These actuators, as described below, are configured to adjust a stitch position of the print bar. End members  104  also include a handle  116  to facilitate the mounting of a print bar assembly to a frame in a printer. The rods  108  are precision cut steel rods, such as the Thomson 60 Case® Standard Shafts available from Thomson Industries, Inc. of Radford, Va., although other sources and metals can be used to form the rods. These shafts are cut to predetermined lengths to enable the end members and three rods to be assembled as shown in  FIG. 1  to form a print bar assembly. As used in this document, a “frame” refers to a structure having a perimeter and an opening into which another object can be mounted or fitted. As used in this document, a “plate” refers to any structure that supports another object. Also, as used in this document, a “rod” or “bar” refers to an elongated member having two ends and a generally uniform cross-section between the two ends. 
       FIG. 2A  is a side view of a print bar assembly  100  with two printheads  124  mounted to the assembly. This print bar assembly is configured for use in a cut sheet printer. Consequently, the printheads  124  eject ink onto a relatively flat media surface. To form the assembly to hold the printheads at an appropriate gap from the relatively flat media surface, the end member  104  has a straight, horizontal profile.  FIG. 2B  is also a side view of a print bar assembly  100  with two printheads  124  mounted to the assembly. This print bar assembly is configured for use in a web printer, such as the one shown in  FIG. 5 . Consequently, the printheads  124  eject ink onto a media surface curved by the backer rollers  128 . To form the assembly to hold the printheads at an appropriate gap from the curved media surface, the end member  104  is angled from the center of the member outwardly towards the two ends of the member. Consequently, end members  104  configured for cut sheet printers or endless belt intermediate printers have a flat, horizontal side profile as shown in  FIG. 2A , while end members  104  configured for web printers or rotating drum intermediate printers have a double canted profile as shown in  FIG. 2B . 
     An exploded view of a modular system for mounting a printhead to a print bar assembly is shown in  FIG. 3 . The system includes a printhead  124 , a printhead plate  128 , a frame  132 , a stitch control mechanism  180 , and a roll control mechanism  190 . The frame  132 , which is made of aluminum, has an opening  136  around which a perimeter of the frame is formed. Three flanges  140   a ,  140   b , and  140   c  extend from the frame  132 . Two flanges  140   a ,  140   b  extend from one side of the frame  132  and each flange has a bushing  148  with an opening  144  that is precision fit onto one of the rods  108 . The third flange  140   c  extends from an opposite side of the frame  132  and has a bushing  150  with a slotted bore ( FIG. 4 ). The third flange  140   c  is approximately at the middle of the side of the frame  132  from which it extends, while the other two flanges  140   a ,  140   b  are positioned near the ends of the side of frame  132  from which they extend. This three point configuration helps prevent the frame  132  from binding on the two rods  108  to which the frame is mounted, as described below, when the frame  132  slides on the rods  108 . Alternatively, four flanges, one at each corner of the frame, could be used to mount the frame to the rods. The slotted bushing  150  mounted within the flange  140   c  provides larger tolerances for shaft-to-shaft spacing and enables the flanges on the frame to expand and contract without affecting shaft alignment under changing thermal conditions within a printer. 
     The printhead  124  is mounted to the printhead plate  128  by two spring-loaded screws  152  provided on opposite sides of the printhead. These screws  152  are received within threaded receptacles  156  in the printhead plate  128 . The printhead plate  128 , which is also made of aluminum, is attached to the frame  132  by biasing members  160 , such as the springs shown in  FIG. 3 . These biasing members  160  extend through holes  164  in the frame  132  and attach to an underside of the frame  132 . As shown in  FIG. 6 , one end of each biasing member  160  engages a hole in a ledge  220  in each of the holes  164 . Once the biasing members  160  are attached to the ledges  220  in the holes  164 , the biasing members  160  urge the printhead plate  128  into contact with the frame  132 . Landing pads  168  are made of hardened steel and are positioned on the upper surface of the frame  132  to be opposite threaded members  172 , such as set screws, in printhead plate  128 . Once the printhead plate  128  is attached to the frame  132  by the biasing members  160 , the ends of the threaded members  172  are turned to contact the pads  168  and level the plate  128  and the printhead  124  with reference to the frame  132 . 
       FIG. 4A  shows the plate  128  attached to the frame  132  by the biasing members  160  passing through the holes  164  in the frame. A stitch control mechanism  180  ( FIGS. 4A and 4B ) is positioned on the frame  132  to move the plate  128  and the printhead  124  in a bi-directional manner within a length of the opening  136 . The mechanism  180  includes an actuator  120  having an output shaft  182  that engages a block  184 , which has a V-shaped notch into which the pointed end of shaft  182  fits. The block  184  is secured to the plate  128  by a screw  186 . A biasing member  188  is positioned between the block  184  and a side of frame  132 . This biasing member  188  urges block  184  towards the end of the output shaft  182  of the actuator  120  so the block  184  and the output shaft  182  remain in contact with one another. Consequently, as a controller operates the actuator  120  to move the output shaft into and out of the actuator, the distance d between the frame  132  and the plate  128  changes. The change in this distance moves the plate and the printhead in the directions indicated by the double-headed arrow adjacent the stitch control mechanism  180  shown in the figure. 
     At the opposite corner of the frame  132  on a diagonal from the stitch control mechanism  180  shown in  FIG. 4A  and  FIG. 4B  is a roll control mechanism  190 . The mechanism  190  rotates the plate  128  and the printhead  124  in the zc-xc plane. The mechanism  190  includes an actuator  120  having an output shaft with a flat end that engages an arm  194  of a pivoting member  198 , which pivots about pin  202  extending from a platform to which the actuator  120  is mounted. A biasing member  204  extends between a bolt  208  in plate  128  and a notched pin  210  in frame  132  to urge plate  128  towards the pivoting member  198  throughout the range of motion of the pivoting member  198 . This configuration enables the plate  128  to rotate about the screw  186  while the pivoting member  198 , the arm  194 , and the output shaft of the actuator  120  remain in contact with one another as the actuator moves the pivoting member  198  through its range of motion. Consequently, as a controller operates the actuator  120  to move the output shaft  192  into and out of the actuator, the arm  194  rotates the pivoting member  198  about the pin  202  causing the plate  128  to rotate about the screw  186  in the double-headed rotational direction shown in  FIG. 4A  and  FIG. 4B . 
     The assembly  210  of the printhead  124 , printhead plate  128 , and the frame  132  is shown in  FIG. 5 . The printhead  124  is secured to the printhead plate  128  by the threaded members  152  and the printhead plate  128  is mounted to the frame  132  by the biasing members  160 , only one of which is visible in  FIG. 5 . Threaded members  172  are then manipulated to level a face  216  ( FIG. 7 ) of the printhead  124 . Stitch control mechanism  180  and roll control mechanism  190  can be used to position the printhead  124  within the opening  136  for proper stitch and roll alignment, respectively, with other printheads mounted to a print bar assembly  100  as described below. The assembly  210  is shown from the opposite side in  FIG. 7 . In this view, the face  216  of the printhead is visible as well as the cap screws  214  that are used to engage and secure the platforms to which the stitch control mechanism  180  and the roll control mechanism  190  are mounted. The printhead face  216  is recessed with respect to the plate  128  as is the frame  132  as well. 
       FIG. 8  shows an arrangement of six assemblies  210  in a staggered array to enable a printer to print a continuous line in a cross-process direction X of a print zone. The surface being printed moves in the process direction P. The arrangement of stitching printheads shown in  FIG. 8  is known, but the structure of the assemblies  210  and the structure of the assembly  100  enable modular formation of a print zone heretofore unknown. In this staggered modular arrangement, the third flange  140   c  of each assembly  210  in row  230  is sandwiched between a flange  140   a  of one assembly  210  in row  234  and a flange  140   b  of another assembly in row  234 . Thus, as is described below, the middle rod  108  of an assembly  100  can pass through the flanges of the assemblies in both rows  230  and  234  to conjoin the assemblies  210 . One of the other remaining rods  108  passes through the flanges  140   c  of the assemblies  210  in row  234  and the other rod  108  passes through flanges  140   a  and  140   b  of the assemblies  210  in row  230 . Thus, the length of the rods  108  determine the number of assemblies  210  that can be used to form a printhead array and the width D of an ink image in the cross-process direction. Such an arrangement of assemblies  210  on an assembly  100  is shown in  FIG. 9 . 
     An alternative arrangement of assemblies  210  is shown in  FIG. 10 . In this arrangement, the inkjet ejectors in the printheads are aligned in the process direction Y. The uppermost rod  108  of an assembly  100  passes through one or more flanges  140   c , depending upon the length of the rod and the number of assemblies positioned adjacent to one another in the cross-process direction X. The lowermost rod  108  of an assembly  100  passes through one or more pairs of flanges  140   a  and  140   b , depending upon the length of the rod and the number of assemblies positioned adjacent to one another in the cross-process direction X. The remaining rods  108  of the assembly pass through pairs of flanges  140   a  and  140   b , each flange in each pair being equidistant from a flange  140   c  of an adjacent assembly  210 . This arrangement enables rows and columns of assemblies to form a structure that accomplishes what a single printhead would if a single printhead could be constructed on such a scale. 
     In printers in which the modular assembly  100  is used for mounting printhead assemblies  210 , thermal energy in the print zone can affect the assembly  100 . Specifically, rods  108  and the end members  104  can expand if the temperatures of the metals used to form these components reach appropriate temperatures. As the rods expand and lengthen, the assemblies  210  can move with the rods and affect the stitching between printheads. To address the issues arising from these phenomena, a link connects the flanges of adjacent frames. Specifically, as shown in  FIG. 11 , the printhead labeled “ 1 ” is conjoined to the printhead labeled “ 2 ” by link  250  and the printhead labeled “ 3 ” is conjoined to the printhead labeled “ 4 ” by the link  254 . To achieve this connection, the flange  140   b  of the printhead labeled “ 1 ” receives a screw  258  that traps one end of the link  250  against flange  140   b  and the flange  140   c  of the printhead labeled “ 2 ” receives a screw  262  that traps another end of the line  250  against the flange  140   c . Similarly, link  254  is connected to the printhead labeled “ 3 ” and the printhead labeled “ 4 .” The links  254  and  258  are made of a material that has a low coefficient of thermal expansion, such as Invar, which is a known nickel-iron alloy. The links and the conjoined frames also affect the movement of other conjoined frames. For example, in  FIG. 11 , the frames for the printheads labeled “ 3 ” and “ 4 ,” act on the frame for the printhead labeled “ 2 ,” which is conjoined to the frame for the printhead labeled “ 1 .” Thus, the links hold the frames  132  together in their stitched relationship and enable the elongating rods  108  to slide through the slotted bushings  148  in the openings  144  of the flanges through which a rod passes. Consequently, the arrangement of the assemblies  210  on the assembly  100  is relatively immune to the thermal expansion of the assembly  100 . Additionally, linking the frames together in this manner enables the two actuators  120  mounted to one of the end frames  104  to push or retract the closest frame  132  to the actuator and the remaining frames in the row corresponding to the actuator  120  respond as well. 
     In operation, a plurality of rods  108  of different lengths are obtained and end members  104  are fabricated. Printhead plates  128  are mounted to frames  132  with the biasing member  160  and printheads  124  are mounted on the plates  128  with screws  152 . The printheads  124  are leveled with screws  172 . The printheads  124  are arranged in an appropriate array for the print zone being constructed and rods  108  are passed through flanges of frames  132  to hold the arrangement together. One end member  104  is positioned to receive the ends of the rods at one side of the arrangement and then another end member  104  is positioned to receive the ends of the rods at the opposite side of the assembly  100 . The ends of the rods frictionally fit within the linearly arranged receptacles in the end members to enable the end members to be removed from the assembly  100  later. Links, such as links  250  and  254 , are mounted to flanges to conjoin adjacent printheads on the assembly  100 . The handles  116  of the two end members  104  are used to carry and position the assembly  100  in a printer where the assembly is mounted. The reverse of this procedure can be performed to disassemble the printhead array and install new rods of a different length to enable a different number of printhead assemblies to be arranged for a print zone of another width. 
     It will be appreciated that variations of the above-disclosed apparatus and other features, and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art, which are also intended to be encompassed by the following claims.