Patent Publication Number: US-2021162763-A1

Title: Fluid ejection inter-module gap

Description:
BACKGROUND 
     Fluid ejection systems, such as three-dimensional printers or flat media printers, sometimes utilize fluid ejection modules supported in an end-to-end relationship so as to collectively span a wider region onto which a fluid is to be dispensed. Such modules may include rows of individual fluid ejection devices or heads, sometimes referred to as ejection heads. The fluid ejection heads are sometimes serviced with a wiper that moves between the modules across the heads. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view schematically illustrating portions of an example fluid ejection system. 
         FIG. 2  is a side view schematically illustrating portions of an example fluid ejection system. 
         FIG. 3  is a side view schematically illustrating portions of an example fluid ejection system. 
         FIG. 4  is a side view schematically illustrating portions of an example fluid ejection system. 
         FIG. 5  is a side view of portions of an example fluid ejection system. 
         FIG. 6  is a flow diagram of an example fluid ejection head wiping method. 
         FIG. 7  is a bottom view of portions of an example fluid ejection system. 
         FIG. 8  is a bottom perspective view of portions of an example fluid ejection system. 
         FIG. 9  is a bottom perspective view of portions of an example fluid ejection system. 
         FIG. 10  is a bottom perspective view of portions of an example fluid ejection system. 
         FIG. 11  is a sectional view of portions of the example fluid ejection system of  FIG. 10 , illustrating portions of an example wiping subsystem. 
         FIG. 12  is a bottom perspective view of portions of the example fluid ejection system of  FIG. 11 . 
         FIG. 13  is an enlarged sectional view of portions of the example fluid ejection system of  FIG. 12 . 
         FIG. 14  is an enlarged sectional view of portions of an example fluid ejection system. 
         FIG. 15  is a bottom perspective view of portions of an example fluid ejection system. 
         FIG. 16  is a bottom perspective view of portions of the example fluid ejection system of  FIG. 15 . 
         FIG. 17  is a bottom perspective view of portions of an example fluid ejection system. 
     
    
    
     Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements. The figures are not necessarily to scale, and the size of some parts may be exaggerated to more clearly illustrate the example shown. Moreover, the drawings provide examples and/or implementations consistent with the description; however, the description is not limited to the examples and/or implementations provided in the drawings. 
     DETAILED DESCRIPTION OF EXAMPLES 
     Disclosed herein are example fluid ejection systems, methods and shrouds that enhance servicing and wiping of ejection heads. The disclosed ejection systems, methods and shrouds reduce or eliminate the bump or bounce that otherwise occurs as a wiper moves from one fluid ejection module to another fluid ejection module. The disclosed ejection systems, methods and shrouds reduce or eliminate such bounce by reducing the gap between consecutive end-to-end ejection modules, the inter-module gap. 
     In one implementation, the inter-module gap is a mesoscale gap, a gap of at least 0.1 mm and no greater than 5 mm. In one implementation, a module Is less than or equal to 1.3 mm. In one implementation, the wiper is rounded with a diameter, wherein the inter-module gap is less than or equal to 7% of the diameter. In one implementation, the wiper comprises a roller having the diameter, wherein the inter-module gap is less than or equal to 7% of the diameter. In another implementation, the inter-module gap is sized such that the wiper, when moving from the first module to the second module, contacts a bridging surface of a bumper disposed between bodies of the first module and the second module before contacting the body of the second module. In one implementation, the fluid ejection module comprises a bumper mounted to or integrally formed as part of the fluid ejection module. In one implementation, the bumper is provided as part of or mounted to a shroud having a rim outwardly extending from an end wall, wherein the bumper, providing a bridging surface, also outwardly extends from the end wall. 
     Disclosed is an example fluid ejection system that may include a first fluid ejection module and a second fluid ejection module. The first fluid ejection module may include a first end, a first module face and a first row of first ejection heads having first ejection faces along the first module face. The second fluid ejection module may include a second end opposite the first end, a second module face and second ejection heads having second ejection faces along the second module face. The first module face and the second module face are spaced apart by a mesoscale inter-module gap. 
     Disclosed is an example method for wiping fluid ejection heads of consecutive fluid ejection modules. The method may include moving a wiper along a first ejection face of a first fluid ejection head on a first module, moving the wiper from the first module across a lower face of the first module adjacent the first ejection face towards a second module, moving the wiper across at least one bridging surface of at least one bumper and across an inter-module gap onto the second module, wherein the wiper contacts the at least one bridging surface prior to contacting the second module, moving the wiping roller across a lower face of the second module, and moving the wiping roller along a second ejection face of a second fluid ejection head on the second module. 
     Disclosed is an example shroud for fluid ejection heads of a fluid ejection module. The shroud may include a panel extending in a plane and having openings through which the fluid ejection heads project, an end wall projecting from the panel, a rim extending outwardly from the end wall away from the panel, and a bumper extending outwardly from the end wall away from the panel, the bumper having a bridging surface spaced from the rim proximate the plane of the panel to reduce an inter-module gap. 
       FIG. 1  schematically illustrates portions of an example fluid ejection system  20 . Fluid ejection system  20  reduces or eliminates the bump or bounce that otherwise occurs as a wiper moves from one fluid ejection module to another fluid ejection module. The disclosed ejection systems, methods and shrouds reduce or eliminate such bounce by reducing the gap between consecutive end-to-end ejection modules, the inter-module gap. Fluid ejection system  20  comprises fluid ejection modules  24 A,  24 B (collectively referred to as modules  24 ). 
     Fluid ejection modules  24  each comprise a module face  26  and a row  27  of fluid ejection heads  28 . Module faces  26  comprise the lower surfaces or faces of modules  24  that face the underlying region onto which fluid is ejected. In one implementation, module faces  26  are coplanar and extend between fluid ejection heads  28 . As will be described hereafter, during wiping of fluid ejection heads  28 , a wiper is moved across and bears against module faces  26  as the wiper moves from one head  28  to another and moves between modules  24 . 
     Ejection heads  28  each have an ejection face  30  through which fluid is controllably ejected. In one implementation, each of ejection heads  28  comprises an individual die or a group of dies (sometimes referred to as slivers) joined together to form the individual ejection head. Each ejection head  28  may comprise a row or multiple rows of fluid ejection nozzles or orifices adjacent chambers, wherein fluid supplied to such chambers is forcefully displaced through the orifices to jet droplets of fluid from the ejection faces. Each of modules  24  supports and joins its respective group or array of heads  28  as a single unit which may be mounted or supported as part of fluid ejection system  20 . 
     As further shown by  FIG. 1 , modules  24  have opposing ends  34 A,  34 B (collectively referred to as ends  34 ). Ends  34  face in directions parallel to the axes along which rows  27  extend. Ends  34  face one another and separate module faces  26  of modules  24  by an inter-module gap G. The inter-module gap G is the space between the closest points or surfaces of module faces  26  in a direction parallel to the direction of rows  27 . The inter- module gap is the space that a wiper must traverse as it is moved from an edge of one of modules  24  on to and across the opposite edge of another one of modules  24 . 
     In systems where the fluid ejection heads  30  are wiped using a wiper having a convex wiping profile, whether rounded, or polygonal, the apex of the wiping profile may temporarily dip or project into the inter-module gap G as it leaves one module and prior to reaching the consecutive module. Continued movement of the wiper towards the consecutive module may result in the apex of the wiper jumping or bouncing out of the inter-module gap G and onto the consecutive module. This jumping or bouncing may cause air to be ingested through the nozzle orifices of the initially engaged fluid ejection head  28 , potentially reducing performance of system  20 . 
     To reduce or eliminate such bouncing, modules  24  are supported, shaped and dimensioned such that the inter-module gap G is within a mesoscale range. For purposes of this disclosure, for a gap to be within the mesoscale range or to be a “mesoscale gap”, the gap is at least 0.1 mm and no greater than 5 mm. In one implementation, the gap is no greater than 1.3 mm. Because inter-module gap G is a mesoscale gap, the convex profile of the wiper dips or project into the inter-module gap G to a lesser extent or not at all as it crosses the inter-module gap G. As a result, such bouncing and potential air ingestion is reduced or eliminated. 
       FIG. 2  schematically illustrates portions of an example fluid ejection system  120 . Fluid ejection system  120  is similar to fluid ejection system  20  described above except that fluid ejection system  120  is additionally illustrated as comprising convex wiper  150 . Convex wiper  150  has a convex profile  152  which faces surfaces  26  as wiper  150  is moved across faces  26  in the direction indicated by arrow  154 . Convex profile  152  has an apex  156 . In the example illustrated, convex profile  152  is curved or rounded. In other implementations, convex profile  152  may be polygonal, having multiple facets that form the overall convex profile  152 . 
     During wiping of an individual fluid ejection face  30  of an individual fluid ejection head  28 , convex wiper  150  presses a wiping surface against the fluid ejection face  30  so as to remove fluid remnants and clean fluid ejection faces  30 . In one implementation, the wiping surface may comprise a rubber or elastomeric material along at least portions of profile  152  so as to contact fluid ejection faces  30 . 
     In another implementation, the wiping surface may comprise a fluid absorbent surface along at least portions of profile  152 . In one implementation, the fluid absorbent surface may comprise a fluid absorbent fabric or other absorbent material fixed or retained relative to wiper  150  along at least portions of profile  152  so as to contact and wipe across the fluid ejection faces  30  of fluid ejection heads  28  as wiper  150  is moved in the direction indicated by arrow  154 . In yet another implementation, convex wiper  150  may comprise a web of fluid absorbent material that is moved between profile  152  and the opposing module  24 A,  24 B, either during wiping of a fluid ejection head  28  or between the wiping of different fluid ejection heads  28 . In one implementation, the web may be held against profile  152  so as to have a corresponding profile. In another implementation, the web may tangentially extend across the apex  156 , wherein the apex  156  of wiper  150  presses the web of wiping material against the fluid ejection face  30  of a fluid ejection head  28  during wiping. 
     In the example illustrated, the inter-module gap G between faces  26  of modules  24  is based upon a size and dimensioning of profile  152  and of apex  156 . In one implementation, profile  152  is rounded, the curved or rounded surface having a diameter (radius of curvature). In such an implementation, the inter-module gap G provided between modules  24  is based upon the diameter/radius of curvature so as to reduce or eliminate an extent to which the apex  156  projects into the gap G as it traverses the gap G. In such an implementation, the inter-module gap G is no greater than 7% of the diameter of profile  152 . In some implementations, the inter-module gap G may be greater than 1.3 mm but no greater than 7% of the diameter of profile  152 . 
       FIG. 3  schematically illustrates portions of an example fluid ejection system  220 . Fluid ejection system  220  is similar to fluid ejection system  120  except that fluid ejection system  220  comprises a wiper in the form of a wipe roller  250 . Those remaining components of fluid ejection system  220  which correspond to components of fluid ejection system  120  are numbered similarly. 
     As with convex wiper  150 , wipe roller  250  has a convex profile  152  which faces surfaces  26  as wiper  250  is moved/rolled across faces  26  in the direction indicated by arrow  154 . Convex profile  152  has an apex  156  closest to the plane or planes containing surfaces  26 . In the example illustrated, convex profile  152  is curved or rounded. In other implementations, convex profile  152  may be polygonal, having multiple facets that form the overall convex profile  152 . 
     During wiping of an individual fluid ejection face  30  of an individual fluid ejection head  28 , convex wiper  250  presses a wiping surface against the fluid ejection face  30  so as to remove fluid remnants and clean fluid ejection faces  30 . In one implementation, the wiping surface may comprise a rubber or elastomeric material along at least portions of profile  152  so as to contact fluid ejection faces  30 . 
     In another implementation, the wiping surface may comprise a fluid absorbent surface along at least portions of profile  152 . In one implementation, the fluid absorbent surface may comprise a fluid absorbent fabric or other absorbent material fixed or retained relative to wipe roller  250  along at least portions of profile  152  so as to contact and wipe across the fluid ejection faces  30  of fluid ejection heads  28  as wipe roller  250  is moved in the direction indicated by arrow  154 . In yet another implementation, wipe roller  250  may comprise a web of fluid absorbent material that is moved between profile  152  and the opposing module  24 A,  24 B, either during wiping of a fluid ejection head  28  or between the wiping of different fluid ejection heads  28 . In one implementation, the web may be held against profile  152  so as to have a corresponding profile. In another implementation, the web may tangentially extend across the apex  156 , wherein the apex  156  of wipe roller  250  presses the web of wiping material against the fluid ejection face  30  of a fluid ejection head  28  during wiping. In one implementation, liberal or  250  is itself rotated about axis  252  as it is being moved across and wiping fluid ejection faces  30  of fluid ejection heads  28  as indicated by arrow  154 . 
     In the example illustrated, the inter-module gap G between faces  26  of modules  24  is based upon a size and dimensioning of profile  152  and of apex  156 . In one implementation, profile  152  is rounded, the curved or rounded surface having a diameter (radius of curvature). In such an implementation, the inter-module gap G provided between modules  24  is based upon the diameter/radius of curvature so as to reduce or eliminate an extent to which the apex  156  projects into the gap G as it traverses the gap G. In such an implementation, the inter-module gap G is no greater than 7% of the diameter of profile  152 . In some implementations, the inter-module gap G may be greater than 1.3 mm but no greater than 7% of the diameter of profile  152 . 
       FIG. 4  schematically illustrates portions of an example fluid ejection system  320 . Fluid ejection system  320  is similar to fluid ejection system  220  described above except that fluid ejection system  320  is illustrated as comprising fluid ejection module  324 A in place of module  24 A. Those remaining components of fluid ejection system  320  which correspond to components of fluid ejection system  220  are numbered similarly. 
     Fluid ejection module  324 A is itself similar to fluid ejection module  24 A except that fluid ejection module  324 A is specifically illustrated as comprising main body  325  and bumper  327 . Main body  325  comprises at least one structure that extends between and connects the fluid ejection heads  28  as a single unit. Main body  325  has a lower face  329  that cooperates with bumper  327  to form the module face  26 . In one implementation, the lower face  329  is provided by a shroud that forms part of main body  325 , the shroud having openings through which fluid ejection heads  28  project or through which fluid from fluid ejection heads  28  is jetted. In one implementation, lower face  329  extends in a plane is coplanar with module face  26  of module  24 B. 
     Bumper  327  outwardly projects from an end of main body  325  towards module  24 B, wherein the outer tip  331  of bumper  327  forms the end of module  324 A and is spaced from the end of face  26  of module  24 B to define the inter-module gap G. In one implementation, the inter-module gap G extending between the tip  331  of bumper  327  and module face  26  of module  24 B a mesoscale gap. In one implementation, the a module gap G is no greater than 1.3 mm. In another implementation, the inter-module gap G is no greater than 7% of a diameter or radius of curvature of the profile  152 , whether it be that of wipe roller  250  or convex wiper  150 . 
     Bumper  327  has a bridging surface  333  facing the same direction of fluid ejection faces  30 . In the example illustrated, bridging surface  333  extends in a plane parallel to a plane containing module faces  26  of module  324 A and  24 B. In one implementation, bridging surface  333  is coplanar with module faces  26 , wherein the bridging surface  333  is flush with module faces  26 . In another implementation, bridging surface  333  may be slightly recessed with respect to module faces  26 , wherein wipe roller  250 , when moving from module  324 A to module  24 B contacts bridging surface  333  prior to contacting module  24 B. In one implementation, bridging surface  333  is recessed from module faces  26  by no greater than 0.25 mm. 
       FIG. 5  schematically illustrates portions of an example fluid ejection system  420 . Fluid ejection system  420  is similar to fluid ejection system  320  except that fluid ejection system  420  comprises fluid ejection modules  424 A and  424 B (collectively referred to as modules  424 ). Each of modules  424  is similar to module  324 A described above except that modules  424 A and  424 B comprise bumpers  427 A and  4276 , respectively (collectively referred to as bumpers  427 ), that project from main body  325  towards one another and have tips  431  that are spaced from one another in which cooperate with one another so as to form inter-module gap G. 
     In one implementation, the inter-module gap G extending between the tip  431  of bumper  427 A and tip  431  of bumper  427 B is a mesoscale gap. In one implementation, the inter-module gap G is no greater than 1.3 mm. In another implementation, the inter-module gap G is no greater than 7% of a diameter or radius of curvature of the profile  152 , whether it be that of wipe roller  250  or convex wiper  150 . 
     Each of bumpers  427  has a bridging surface  333  facing same direction of fluid ejection faces  30 . In the example illustrated, bridging surface  333  extends in a plane parallel to a plane containing module faces  26  of modules  424 . In one implementation bridging surface  333  is coplanar with module faces  26 , wherein the bridging surface  333  is flush with module faces  26 . In another implementation, bridging surface  333  may be slightly recessed with respect to module faces  26 , wherein wipe roller  250 , when moving from module  424 A to module  424 B contacts bridging surface  333  prior to contacting module  424 B. In one implementation, bridging surfaces  333  are recessed from module faces  26  by no greater than 0.25 mm. 
       FIG. 6  is a flow diagram of an example fluid ejection module wiping method  500 . Method  500  facilitates wiping of fluid ejection heads of two end-to-end fluid ejection modules with reduced bouncing of a wiper during movement of the wiper from one module to another module to reduce air ingestion. Method  500  facilitates such reduced bouncing by reducing the size of an inter-module gap between such modules. In the example illustrated, method  500  reduces the size of the inter-module gap using at least one bumper between the modules and proximate the fluid ejection faces of the modules. 
     As indicated by block  504 , a wiper is moved along the first ejection face of a first fluid ejection head on a first fluid ejection module. As indicated by block  508 , wiper is further moved from the first module across a lower face of the first module adjacent the first ejection face towards a second module. As indicated by block  512 , wiper is then moved across at least one bridging face of at least one bumper and across an inter-module gap onto the second module. During such movement, the wiper contacts the at least one bridging surface prior to contacting the second module. As indicated by block  516 , the wiper is moved across a lower face of the second module. As indicated by block  520 , the wiper is then moved along a second ejection face of a second fluid ejection head on the second module. Because the wiper contacts the least one bridging surface prior to contacting the second module, the least one bridging surface temporarily supports the wiper during the crossover, reducing or eliminating bounce of the wiper as it initiates contact with the second module. 
       FIG. 7  is a bottom view of portions of an example fluid ejection system  620 . Fluid ejection system  620  is similar to fluid ejection system  420  except that fluid ejection system  620  comprises fluid ejection modules  624 A and  624 B (collectively referred to as modules  624 ). Modules  624  are similar to modules  424  described above except that body  325  each surround and support multiple parallel rows  627  of fluid ejection heads  28  along their lengths. Modules  624 A and  624 B further comprise bumpers  627 A and  627 B, respectively (collectively referred to as bumper  627 ). Bumpers  627  are similar to bumpers  427  described above except that bumpers  627  are specifically illustrated as having a width corresponding to a width of their respective module  624 . In other words, bumper  627 A extends across or spans across the ends of both of rows  627  of module  624 A. Likewise, bumper  627 B extends across or spans across the ends of both of rows  627  of modules  624 B. in one implementation, wipe roller  250  also has a width so as to concurrently wipe both of throws  27  of fluid ejection heads  28  on one of module  624 . In such an implementation, bumper  627  evenly supports wipe roller  250  across the width of module  624  as the wipe roller  250  crosses the inter-module gap G defined by the outermost answer tips of bumpers  627 . 
       FIG. 8  is a bottom view illustrating portions of an example fluid ejection system  720 .  FIG. 8  illustrates a juncture of two example end-to-end fluid ejection modules  724 A and  724 B (collectively referred to as module  724 B). Modules  724 A,  724 B each comprise a main body  725  supporting a bumper. The main body  725  of module  724 A supports bumper  727 A while main body  725  of module  724 B supports bumper  727 B. Each main body  725  comprises a module face  726  and rows  727 - 1 ,  727 - 2  of fluid ejection heads  728 . Module faces  726  extend about fluid ejection faces  730  of fluid ejection heads  728 . Module faces  726  of module  724  are substantially coplanar with one another. 
     Fluid ejection heads  728  are similar to fluid ejection heads  28  described above. Each of fluid ejection heads  728  comprises a fluid ejection die or multiple fluid ejection dives joined together as a unit or head. Each fluid ejection head  728  may comprise a plurality of parallel rows of fluid ejection orifices or nozzles through which fluid is ejected. For example, in one implementation, each row of nozzles may comprise a series of chambers supplied with fluid that is displaced through the orifices by fluid actuator. Examples of such a fluid actuator that may be utilized include, but are not limited to, thermal actuators, piezo-membrane based actuators, electrostatic membrane actuators, mechanical/impact driven membrane actuators, magnetostrictive drive actuators, electrochemical actuators, other such microdevices, or any combination thereof. 
     In the example illustrated, each main body  725  comprises a shroud  770  having openings  772  exposing a fluid ejection face  730  of respective fluid ejection head  728 . In the example illustrated, fluid ejection faces  730  are parallel to module faces  726 . In the example illustrated, fluid ejection heads  728  project through and beyond their respective openings  772 . In other implementations, fluid ejection had  728  may be flush or may be slightly recessed within their respective opening  772 . Each shroud  770  comprises a panel  780  forming the module face  726  and having the openings through which the fluid ejection heads  728  are exposed, an end wall  782  and a rim  784  outwardly projecting from the end wall  728 . 
     In the example illustrated, bumpers  727  are formed as part of the shroud, formed below (above in  FIG. 8 ) their respective rim  784  outwardly extending from end wall  782  away from panel  780 . Each of bumpers  727  fills in the gap formed by the projecting rim  784  and provide a bridging surface  733  such that the inter-module gap between panels  780  is smaller. 
     As further shown by  FIG. 8 , the rows  727 - 1 ,  727 - 2  of fluid ejection head  728  of each of modules  724  are staggered relative to one another. In the example illustrated, the ends of modules  724  are each oppositely stepped, facilitating the overlap of row  727 - 1  of module  724 A with respect to row  727 - 2  of module  724 B. This overlap facilitates gapless printing or fluid ejection. 
     In the example illustrated, each of bumpers  727  continuously extends along the entire width of the respective module  724 , across entire width of a respective main body  725 . The reverse stepping of module  724  further results in row  727 - 1  of module  724 A extending beyond a first portion of bumper  727 A and a second portion of bumper  727 A projecting beyond an end of row  727 - 2  of module  724 B. Similarly, the reverse stepping of module  724  results in row  727 - 2  of module  724 B extending beyond a first portion of bumpers  727 B and a second portion of bumper  727 B projecting beyond an end of row  727 - 1  of module  724 A. 
     As with bumpers  427  described above, bumpers  727  reduce the size of any inter-module gap G. In one implementation, the opposing bumpers  727  along panel  780  are spaced by gap within the mesoscale range. In one implementation, the opposing bumpers are spaced by a distance no greater than 1.3 mm. In another implementation, the inter-module gap G is no greater than 7% of a diameter or radius of curvature of the profile  152 , whether it be that of wipe roller  250  or convex wiper  150  (shown and described above). 
     Each of bumpers  727  has a bridging surface  733  facing same direction of fluid ejection faces  730 . In the example illustrated, bridging surface  733  extends in a plane parallel to a plane containing module faces  726  of modules  724 . In one implementation bridging surface  733  is coplanar with module faces  726 , wherein the bridging surface  733  is flush with module faces  726 . In another implementation, bridging surface  733  may be slightly recessed with respect to module faces  726 , wherein wipe roller  250  (shown and described above), when moving from module  724 A to module  724 B contacts bridging surface  733  prior to contacting module  724 B. In one implementation, bridging surfaces  733  are recessed from module faces  726  by no greater than 0.25 mm. 
     In one implementation, each of bumpers  727  is connected to end wall  782  of shroud  770 . In one implementation, each of bumpers  727  is formed from a polymer or rubber material while shroud  770  is formed from a metal. In such an implementation, each of bumpers  727  may be attached through adhesive, heat staking or other methods. In other implementations, each of bumpers  727  may be formed from a metal material which is spot welded or otherwise fixed to end wall  782  of shroud  770 . 
       FIG. 9  schematically illustrates portions of an example fluid ejection system  820 . Fluid ejection system  820  is similar to fluid ejection system  720  described above except that each of modules  724  comprises spaced bumpers  827 - 1  and  827 - 2  (collectively referred to as bumpers  827 ) in place of a single bumper  727 . Each of bumpers  827  comprises a polymer or rubber material secured to end wall  782  of shroud  770 . Each of bumpers  827  may be attached through adhesive, heat staking or other methods. In other implementations, each of bumper  827  may be formed from a metal material which is spot welded or otherwise fixed to and wall  782  of shroud  770 . Each of bumpers  827  has a width greater than or equal to a width of fluid ejection face  730  of the fluid ejection heads  728 . 
     As with bumpers  727  described above, bumpers  827  reduce the size of any inter-module gap G. In one implementation, opposing bridging surfaces  733  of bumpers  727  are spaced by a distance within the mesoscale range. In one implementation, the opposing bridging surfaces  733  of bumper  727  are spaced by a distance no greater than 1.3 mm. In another implementation, the inter-module gap G is no greater than 7% of a diameter or radius of curvature of the profile  152 , whether it be that of wipe roller  250  or convex wiper  150  (shown and described above). 
     Bridging surfaces  833  face in a same direction as fluid ejection faces  730 . In the example illustrated, each bridging surface  733  extends in a plane parallel to a plane containing module faces  726  of modules  724 . In one implementation bridging surface  833  is coplanar with module faces  726 , wherein the bridging surface  833  is flush with module faces  726 . In another implementation, bridging surface  833  may be slightly recessed with respect to module faces  726 , wherein wipe roller  250  (shown and described above), when moving from module  724 A to module  724 B contacts bridging surface  833  prior to contacting module  724 B. In one implementation, bridging surfaces  833  are recessed from module faces  726  by no greater than 0.25 mm. 
       FIGS. 10-13  illustrate portions of an example fluid ejection system  920 .  FIG. 10  is a perspective view illustrating portions of an example bumper  927 - 1  mounted to shroud  770  (described above) for use as part of a fluid ejection module  924 A and fluid ejection module  924 B shown in  FIG. 12 . Bumper  927 - 1  comprises a stamped sheet metal strip bent or otherwise forming a bridging surface  933  which is flush with the adjacent portions of panel  780  of main body  725 . In one implementation, bumper  927 - 1  is attached to the metal of shroud  770  by spot welding. In yet other implementations, bumper  927 - 1  may be secured to end wall  782  by adhesives or fasteners such as rivets. In some implementations, bumper  927 - 1  may be integrally formed as part of a single unitary body with shroud  770 . For example, bumper  927 - 1  may comprise an extension of panel  780 . Bumpers  927 - 2  (shown in  FIGS. 12 and 13 ) may be formed and secured in a similar fashion. 
       FIGS. 11 and 12  illustrate an example wiping subsystem  980  of fluid ejection system  920 . Wiping subsystem  980  wipes fluid ejection faces  730  of fluid ejection heads  728 . Wiping subsystem  980  comprises support  1049 , wipe roller  1050 , bias spring  1052 , wiping web supply  1054 , waste wiping web take-up roller  1056 , take-up drive  1058 , tension rollers  1060  and service station actuator  1064 . Support  1049  comprise a housing, bracket or other structure that supports remaining components of subsystem  980  such that the components may be moved as a unit relative to and across modules  924  by service station actuator  1064 . Wipe roller  1050  is similar wipe roller  250  described above. In the example illustrated, wipe roller  250  rotates about a rotational axis  1066 . Wipe roller  1050  rotates as a web  1068  of wiping material, that is an absorbent wipe material, is supplied about roller  1050 , between the apex  956  of roller  1050  and module surfaces  726  of modules  924 . 
     Bias spring  1052  resiliently biases roller  150  towards module faces  726  and towards fluid ejection faces  730 . Wiping web supply  1054  comprises a roll of wiping material. Waste wiping web take-up roller  1056  takes up portions of web  1068  that have been used, that may contain absorbed fluid taken from the fluid ejection faces  930  of fluid ejection heads  728 . Take-up drive  1058  comprises an electrically powered motor that rotates roller  1056  to controllably move web  1068  across apex  956  of roller  1050 . Tension rollers  1060  maintain web  1068  in tension. Service station actuator  1064  (schematically illustrated) comprises a drive for moving support  1049  (and the remaining components of wiping subsystem  980 ) across modules  924 A,  924 B. 
     As shown by  FIG. 12 , fluid ejection modules  924 A,  924 B (collectively referred to as fluid ejection modules  924 ) are each similar to fluid ejection modules  724  except that fluid ejection modules  924  each comprise bumpers  927 - 1  and  297 - 2 . As with bumpers  827 , bumpers  927 - 1  extend opposite to one another and bumpers  927 - 2  extend opposite to one another, bridging between the modules  924  to define the smaller inter-module gaps between the ends of such opposing bumpers  927 . 
       FIG. 13  illustrates two of the opposing bumpers, bumpers  927 - 1  of modules  924  in more detail. As shown by  FIG. 13 , each of modules  927 - 1  form the bridging surface  933  which reduces the inter-module gap from G′ to G. In one implementation, the inter-module gap G is reduced by at least 40%. In one implementation, the inter-module gap G is reduced to a gap of no greater than 1.3 mm. In another implementation, the inter-module gap G is no greater than 7% of a diameter or radius of curvature of the profile  152  of wipe roller  1050 . The reduced inter-module gap reduces bouncing of wipe roller  1050  and the backed wiping web as wipe roller  1050  crosses between consecutive modules  924 . 
     As shown by  FIG. 14 , in other implementations, bumpers  927 - 1  (as well as bumpers  927 - 2 ) may be slightly recessed from module face  726 , wherein wipe roller  1050  and web  1068 , during movement from module  924 A to module  924 B (and vice versa) bear upon at least one of bridging services  933  prior to reaching the opposing edge of the destination module. In one implementation, bridging services  933  are spaced from module faces  726  by a spacing S of no greater than 0.25 mm. In yet other implementations, the spacing may vary depending upon the diameter of wipe roller  1050 . 
       FIGS. 15 and 16  illustrate portions of an example fluid ejection system  1120 . System  1120  is similar to system  920  described above except that each of modules  924  comprises bumpers  1127 - 1 ,  1127 - 2  (collectively referred to as bumpers  1127 ) in place of bumpers  927 - 1 ,  927 - 2 . Those remaining components of system  1120  which correspond to components of system are numbered similarly and/or are shown in  FIGS. 11 and 12 . 
     Bumpers  1027  are similar to bumpers  927  except that bumpers  1027  comprise looped bumpers, a loop of material or an open loop of material joined to end wall  782  of shroud  770 . In one implementation, bumpers  1127  comprise a loop or partial loop of wire spot welded at multiple points to end wall  782  of shroud  770 . In another implementation, bumpers  1027  may be joined to end wall  782  through adhesive, fasteners or the like. In yet other implementations, bumpers  1127  may be formed from a polymer which is joined to end wall  782 . 
     As with the above described bumpers, bumpers  1127  reduce the inter-module gap from G′ to G. In one implementation, the reduced inter-module gap G is no greater than 1.3 mm. In another implementation, the inter-module gap G is no greater than 7% of a diameter or radius of curvature of the profile  152  of wipe roller  1050  (shown in  FIGS. 11 and 12 ). The reduced inter-module gap reduces bouncing of wipe roller  1050  and the backed wiping web  1068  as wipe roller  1050  crosses between consecutive modules  924 . 
       FIG. 17  illustrates another implementation of example bumpers that may be provided on a shroud of a fluid ejection module.  FIG. 17  illustrates shroud  770  supporting bumpers  1227 - 1 ,  1227 - 2  (collectively referred to as bumpers  1227 ). Bumpers  1227  comprise blocks of material, such as blocks a metal or polymer material, secured to end wall  782  of shroud  770 . Such blocks may be secured in wall  782  through welding, adhesives, fasteners or interlocking mechanisms. 
     Such blocks forming bumpers  1227  have a thickness so as to reduce the inter-module or gap between consecutive modules. As with the above described bumpers, bumpers  1227  reduce the inter-module gap from G′ to G. In one implementation, the inter-module gap is no greater than 1.3 mm. In another implementation, the inter-module gap G is no greater than 7% of a diameter or radius of curvature of the profile  152  of wipe roller  1050  (shown in  FIGS. 11 and 12 ). The reduced inter-module gap reduces bouncing of wipe roller  1050  and the backed wiping web  1068  as wipe roller  1050  crosses between consecutive modules  924 . 
     Although the present disclosure has been described with reference to example implementations, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the claimed subject matter. For example, although different example implementations may have been described as including features providing one or more benefits, it is contemplated that the described features may be interchanged with one another or alternatively be combined with one another in the described example implementations or in other alternative implementations. Because the technology of the present disclosure is relatively complex, not all changes in the technology are foreseeable. The present disclosure described with reference to the example implementations and set forth in the following claims is manifestly intended to be as broad as possible. For example, unless specifically otherwise noted, the claims reciting a single particular element also encompass a plurality of such particular elements. The terms “first”, “second”, “third” and so on in the claims merely distinguish different elements and, unless otherwise stated, are not to be specifically associated with a particular order or particular numbering of elements in the disclosure.