Abstract:
A liquid dispenser. The dispenser includes a base structure, a plurality of cartridges releasably mounted to the base structure, and a valve fluidly coupled with an applicator head to allow continued contact with and selective deposition of the liquid to a product passing through a travel path between the cartridges. At least one of the cartridges is linked to the base structure through a variable coupling that is linearly responsive to changes in thickness or planarity of the product such that the applicator head automatically maintains constant contact with the product, regardless of such changes, without having to stop the dispenser or ancillary pieces of machinery. The cartridges are hand interchangeable such that liquid can be deposited on either an upper or lower surface of the product without requiring any tools to affect top-down or bottom-up deposition. The applicator head is additionally hand removable from the valve such that it can be attached to or removed from the valve without requiring the use of any tools.

Description:
BACKGROUND OF THE INVENTION 
   This invention relates to a dispenser used in liquid deposition devices, and more particularly to a high speed, high precision glue dispenser that is responsive to sheets of material passing through it such that adhesive can be deposited onto sheets of varying thickness passing through the glue dispenser without manual intervention or loss of contact between the sheets and the dispenser, even if the sheets demonstrate non-planar attributes. 
   Automated gluing systems are routinely used to affect high-speed, repeatable application of adhesives to various substrates. This practice has been used extensively in the manufacture of paper and related products, such as corrugated cardboard, where devices known as flexo folder gluers receive one or more sheets to have them printed, die cut, glued and folded. While in the gluing station portion of the flexo folder gluer, the sheet has one or more rows of continuous adhesive lines or discontinuous adhesive dots deposited onto one or more of its flap surfaces as it travels past a glue applicator head. In a conventional gluing station, the sheet is fed into a gap along a preferred path such that an aligned valve and nozzle can be actuated to deposit a stream of the adhesive onto the desired location on the sheet. The one or more valves are securely mounted to a support structure, such as a mounting plate to ensure consistent adhesive application. While this works well for its intended purpose, it tends to be inflexible in terms of changing the valves out when service is required. In addition, by rigidly fixing the gap spacing, the system is not well-suited to accommodating sheets that demonstrate non-planar attributes (such as curled, warped or related surface undulations), or sheets of differing thickness, as thin sheets tend to float or bounce around, while thick substrates tend to pinch, causing substrate misalignment and subsequent compromise of adhesive deposition. 
   One way to avoid the inaccuracies and down-time of a fixed applicator is to incorporate a “floating” dispenser, where the dispensing member is movable relative to the rest of the applicator due to the use of a slide bearing. While these help reduce the incidence of pinching and subsequent jamming of sheets as they pass by the dispenser, the repeated, intermittent periods of non-contact between the head and the sheets being glued does not adequately allow the system to purge any residual glue from the discharge apertures located on the applicator head. This makes the head prone to the buildup of dried, hardened glue around its discharge apertures, which leads to a concomitant decrease in glue deposition quality. 
   What is needed is a glue dispenser that can adjust automatically to travelling sheets with surface undulations or of differing thickness without requiring the user to adjust the mechanism or otherwise interrupt operation of the machine. What is additionally needed is a way to keep the passing sheet in constant contact with the applicator head during glue deposition without too tight of a fit to promote accurate, repeatable glue application to sheets of differing thickness. 
   SUMMARY OF THE INVENTION 
   This need is met by the present invention, wherein an applicator head and valve are movably coupled to a mounting plate such that the applicator head is always in contact with a sheet, thereby improving the deposition of a liquid thereon. The sheets are not limited to corrugated cardboard, but rather can be any foldable substrate that is held together upon folding by adhesives. Similarly, the liquid deposited need not be glue or related adhesive, but can be any liquid where precise, repeatable application on a generally planar substrate is needed. According to a first aspect of the invention, an applicator head for a liquid dispenser is disclosed. The applicator head comprises an inlet configured to be coupled to a liquid source, an outlet in fluid communication with the inlet, and a shim. The outlet includes a plurality of apertures such that liquid flowing through the outlet exits through the apertures. The shim comprises a proximal end fluidly coupled to the inlet, a distal end fluidly coupled to the outlet, and a flowpath from the proximal end to the distal end, where a substantial portion of the flowpath is divergently-shaped. 
   Optionally, the applicator head has a quick-release mechanism disposed on the inlet. Preferably, this quick-release mechanism enables tool-free insertion and removal of the application head to a liquid source. The apertures may be linearly arranged across a dispensing surface of the outlet, while the dispensing surface can include a flow channel disposed about each of the apertures such that a flow channel extends from each aperture to a trailing edge of the dispensing surface. The applicator head further comprises a plurality of bevelled surfaces adjacent to and tapering away from the plateaued dispensing surface. Preferably, these bevelled surfaces define a faceted outer profile of the applicator head so that its resistance to causing passing sheets to pinch or jam is increased. At least two of the bevelled surfaces are preferably disposed along a lateral side of the applicator head to maximize the number of apertures used for liquid dispensing while maintaining a small contact area. The shim can be interchangeably disposed between the inlet and the outlet such that the proximal and distal ends, as well as the flowpath in between, define a manifold. 
   According to another aspect of the invention, a liquid dispenser is disclosed. The liquid dispenser includes a first cartridge and a second cartridge spaced relative to the first cartridge. The first cartridge includes a first mount, a first inlet guide, a valve coupled to the first mount, and an applicator head fluidly coupled to the valve. The valve is configured to be coupled to a liquid source and an actuation source. The applicator head includes a liquid inlet, a liquid outlet in fluid communication with the liquid inlet, and a shim. The liquid outlet includes a plurality of apertures for dispensing the liquid. The shim is made up of a proximal end fluidly coupled to the liquid inlet, a distal end fluidly coupled to the liquid outlet, and a flowpath, all in a manner similar to that of the previously-discussed aspect. The second cartridge includes a second mount with a second inlet guide disposed relative to the first inlet guide such that a product travel path is defined therebetween, and an outlet guide coupled to the second mount. 
   Optionally, the product travel path converges along the direction of product travel such that the product is guided into contact with a plateaued dispensing surface defined on the liquid outlet. In addition, the converging product travel path is made up of the first and second inlet guides configured as a pair of converging ramps. The first and second cartridges are preferably disposed vertically one above the other, although such placement is not critical. Moreover, the cartridges are interchangeable with one another, while the applicator head is configured to be quick releasable from the valve without the use of any tools. The outlet guide can be a bearing roller, which is slidably adjustable along the direction of product flow. Preferably, the valve is pneumatically or electrically actuated. A liquid deflector shield can be attached to various locations as needed, such as to the second mount, to protect select componentry from the liquid. 
   According to yet another aspect of the present invention, a liquid dispenser is disclosed. The liquid dispenser includes a base structure, a first cartridge releasably coupled to the base structure, a second cartridge releasably coupled to the base structure, and a variable coupling that links at least one of the cartridges to the base structure. The coupling is forcibly biased to define a first gap between an applicator head and an outlet guide on the second cartridge. The coupling moves in response to a force against at least one of the outlet guide and the applicator head, and in so doing defines a second gap that is greater than the first gap. The first cartridge includes a first mount, a valve coupled to the first mount and an applicator head fluidly coupled to the valve. The valve is configured to be coupled to a liquid source and an actuation source, while the applicator head is configured to deposit liquid onto a product while remaining in constant contact with the product. The second cartridge includes a second mount with an outlet guide coupled to the second mount. The first and second mounts on the respective first and second cartridges make up the structural backbone of the cartridges. 
   Optionally, the first mount includes a first inlet guide, while the second mount includes a second inlet guide. The second inlet guide is disposed relative to the first inlet guide such that a product travel path is defined between them. In addition, the bias is affected by a spring mounted between the base structure and the coupling. The applicator head may be configured as previously discussed, including the quick-release and flowpath features. In addition, at least one of the cartridges includes a quick-release mechanism to facilitate easy, tool-less removal and installation of the cartridge. Preferably, the two cartridges are arranged in a substantially vertical relationship with one another, and the coupling is preferably linked to the vertically uppermost of the first and second cartridges. Each of the cartridge first and second mounts may further include a connecting pin configured to permit quick release from the base structure. The connecting pin on each of the mounts is similar, thus facilitating cartridge interchangeability. In addition, since the cartridges are interchangeable, either can be linked to the coupling. Preferably, the first and second cartridges are substantially vertically spaced relative to one another. The coupling may additionally include a cartridge weight compensator configured to at least partially compensate for a vertically downward force component of the weight of the uppermost cartridge. This cartridge weight compensator may be in the form of a fluid-actuated piston, which may more particularly be pneumatically-actuated. In addition, the cartridge weight compensator may apply a variable (including user-defined) force to the coupling. The cartridge weight compensator may also be mounted to the base structure. The liquid dispenser may further include a linear bearing to limit the motion of the coupling along a single axis, such as a substantially vertical axis. This linear bearing may be mounted to either the base structure or the coupling such that it slidably connects the two together. Preferably, the linear bearing has a housing around it to prevent the liquid from contacting the linear bearing. In addition, the direction of movement imparted on the coupling by the cartridge weight compensator is parallel to the direction of movement in the linear bearing. 
   According to still another aspect of the invention, a glue dispenser is disclosed. The glue dispenser includes a base structure, a first cartridge releasably coupled to the base structure, a second cartridge releasably coupled to the base structure, and a variable coupling that links the base structure and at least one of the cartridges. The coupling is movably responsive to the passage of the product such that variations in the thickness or planarity of the product cause the variable coupling and the cartridge to which it is linked to move a proportionate distance while at least one of the outlet guide and the applicator head remain in contact with the product. 
   According to yet another aspect of the invention, a flexo folder gluer for manufacturing containers is disclosed. The flexo folder gluer includes at least a printing station, a die cutting station coupled to the printing station, a gluing station coupled to the die cutting station, a folding station coupled to the gluing station, and a conveying mechanism configured to transport one or more sheets between the printing, die cutting, gluing and folding stations. The glue station is similar to that described in the previous aspect of the invention. 
   According to another aspect of the invention, a method of depositing liquid on a sheet of material is disclosed. The method includes the steps of configuring a liquid dispenser to include a base structure, a first cartridge releasably coupled to the base structure, a second cartridge releasably coupled to the base structure and spaced relative to the first cartridge, and a coupling onto which at least one of the cartridges is mounted. The coupling is linked to the base structure and is biased to define a first gap between an applicator head and an outlet guide, and movable in response to a force against at least one of the outlet guide and the applicator head to a second gap that is greater than the first gap. Additional steps include inserting the sheet of material into the travel path, establishing contact between the applicator head and the sheet of material, and depositing liquid on at least a portion of the sheet of material while the applicator head remains in contact with the sheet of material. The first cartridge includes a first mount, a valve coupled to the first mount, a liquid source and an actuation source, and an applicator head fluidly coupled to the valve. The second cartridge includes a second mount and an outlet guide coupled to the second mount. Optionally, the method comprises the additional step of configuring the applicator head to comprise a liquid inlet, a liquid outlet and a shim as discussed previously. In addition, the sheet of material is a sheet of corrugated cardboard. Moreover, the cartridges can be configured to include respective inlet guides disposed relative to one another such that a travel path for the sheet of material is defined between the inlet guides. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     The following detailed description of the present invention can be best understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which: 
       FIG. 1  shows a block diagram of a flexo folder gluer for printing, cutting, gluing and folding corrugated cardboard, including a gluing station according to the present invention and a stack of flat corrugated sheets prior to passage through the machine; 
       FIG. 2  shows a single sheet of the corrugated cardboard of  FIG. 1 , highlighting the panel and tab locations where glue is often applied; 
       FIG. 3  shows a gluing station according to the present invention; 
       FIG. 4A  shows a first removable cartridge in plan view, with valve and applicator head attached; 
       FIG. 4B  shows the first removable cartridge of  FIG. 4A , in perspective view; 
       FIG. 5A  shows the applicator head removed from the cartridge of  FIGS. 5A and 6B ; 
       FIG. 5B  shows an exploded view of the applicator head of  FIG. 5A ; 
       FIG. 5C  shows an elevation view of the applicator head in a top-down, tab-side position engaging a protruding tab along the travel direction of the corrugated sheet; 
       FIG. 5D  shows an exploded view of an alternate applicator head with a multi-layer shim; 
       FIG. 6A  shows a second removable cartridge in plan view, with outlet guide attached; 
       FIG. 6B  shows the second removable cartridge of  FIG. 6A  in perspective view, with outlet guide attached; 
       FIG. 7A  shows the gluing station of  FIG. 3  in its top-down configuration for depositing glue on an end panel of the corrugated sheet of  FIG. 2 ; 
       FIG. 7B  shows the gluing station of  FIG. 3  in its bottom-up configuration for depositing glue on an end panel of the corrugated sheet of  FIG. 2 ; 
       FIG. 8A  shows the gluing station of  FIG. 3  in its top-down configuration for depositing glue on a tab of the corrugated sheet of  FIG. 2 ; 
       FIG. 8B  shows the gluing station of  FIG. 3  in its bottom-up configuration for depositing glue on a tab of the corrugated sheet of  FIG. 2 ; 
       FIG. 9A  shows the gluing station of  FIG. 3 , with the removable cartridges removed for clarity, prior to the introduction of a corrugated sheet; and 
       FIG. 9B  shows the gluing station of  FIG. 9A  as a corrugated sheet passes therethrough. 
   

   DETAILED DESCRIPTION 
   Referring initially to  FIGS. 1 and 2 , a block diagram highlights the major components of a flexo folder gluer  1  according to the present invention, as well as a typical sheet  10  of corrugated paper on which the flexo folder gluer  1  operates. The flexo folder gluer  1  includes a feeding station  100 , printing station  200 , die cutting station  300 , gluing station  400 , folding station  500  and counter ejector station  600 . It will be appreciated by those skilled in the art that additional components typically associated with flexo folder gluers, such as controllers, conveyors (or similar sheet transport mechanism) and sensing and quality-control equipment, while not shown or discussed, are acknowledged to make up the remainder of the present flexo folder gluer  1 . It will also be appreciated that certain operations may be consolidated, as, for example, gluing station  400  and folding station  500  can form a single station. Other stations, such as printing station  200 , may be accomplished in a series of sub-stations (not shown). A quantity of sheets  10 , shown in the figure as a stack  30 , are introduced from the feeding station  100  to the print station  200  to receive printed indicia thereon by well-known printing methods. Sheet  10 , which is typically corrugated cardboard ranging from a single layer of approximately 3 millimeters (mm) thick up to a multilayer of approximately 15 mm thick, can include a series of panels  12 ,  14 ,  16  and  18  that are defined by creases  22  (alternately referred to as score lines), along which the various panels can be folded to form container structures of a desired dimension. The sheet  10  is typically fed into the flexo folder gluer  1  such that either of edges  15  or  13  can define the leading (or feed) edge, depending on which direction the sheet  10  is fed (as indicated by arrow A) into the feeding station  100 . Lateral edge  17  generally coincides with a remote end panel (shown in the present figure as fourth panel  12 ), while lateral edge  19  generally coincides with a tab  20  used in subsequent folding operations. The gluing station  400  deposits adhesive (glue) along at least a portion of the length of one of the surfaces adjacent the edges  17 ,  19 . As will be shown in more detail below, the gluing station  400  can be configured to deposit “top down”, as shown by lines of adhesive  24  in the figure, or “bottom up” such that adhesive  24  is disposed on the opposing face from that shown. In addition, the flexo folder gluer  1  can be configured to have one gluing station  400  (which would enable the deposition of adhesive  24  on either fourth panel  12  or tab  20 ), or to have two gluing stations spaced apart and facing each other such that double gluing can occur, as both fourth panel  12  or tab  20  can simultaneously receive adhesive  24 . It will be appreciated by those skilled in the art that while the adhesive  24  is shown as continuous lines along the travel path of the sheet  10 , it could also be made up of discontinuous dots or beads (not shown). Sheet  10  can also include die cuts  26  that can be formed in the sheet  10  either prior to insertion of the sheet  10  into the flexo folder gluer  1 , or by die cut station  300  that is part of the flexo folder gluer  1 . Creases  28  (similar to creases  22 ) can be placed across the sheet feed direction A for additional folding options. 
   Referring next to  FIG. 3 , details of the gluing station (alternately referred to as a dispenser)  400  are shown. It will be appreciated by those skilled in the art that while the subsequent discussion is with regard to the dispenser operating on glue and related adhesives, the structure is not so limited, as such structure is equally applicable to the deposition of other liquids (for example, soap, lotion, release varnish or the like) onto a generally planar substrate. Base structure  402  is a plate onto which the remaining components can be secured, and may include additional structure (such as brackets and blocks) to ensure rigid connection to other parts. For example, sensor  440 , used to detect the presence of a sheet (not shown) entering the gluing station  400 , can be rigidly mounted to the base structure as shown. Base structure  402  itself can be attached to flexo folder gluer  1  through conventional attachments, such as rods  403 . The base structure  402  has numerous holes of various spacings to facilitate attachment of various components. A first cartridge  404  is removably mounted to the base structure  402  through a variable coupling  434  which provides a slidable link between the base structure  402  and first cartridge  404 . This slidable link allows coupling  434  and first cartridge  404  attached to it to move up and down vertically in response to passing sheets of differing thickness, or due to undulations in the sheet. First cartridge  404  includes a first mount  410  with a first inlet guide  412 , a valve  414  and applicator head  420  fluidly connected via quick-release coupler  422 . A second cartridge  424  is removably mounted to the base structure  402 , and includes a second mount  426  with a second inlet guide  428  and outlet guide  432  (the latter alternately referred to as a bearing bar). When the cartridges  404 ,  424  are mounted onto the base structure  402 , their placement relative to one another is such that one is situated vertically above the other so that a sheet travel path  430  is defined between them. As previously mentioned, the gluing station  400  can be configured as either “top down” (where the first cartridge  404  is above second cartridge  424 ) such that the glue is placed on an upward-facing surface on the sheet, or “bottom up” (where the second cartridge  424  is above first cartridge  404 ) such that the glue is placed on a downward-facing surface on the sheet. Accordingly, while the operation of the gluing station  400  is described in regard to the “top down” configuration as shown in the figure, it will be appreciated that the “bottom up” configuration is equally applicable. 
   The coupling  434 , which includes a cartridge weight compensator  444  (discussed in more detail below), is connected to the uppermost of the two cartridges (shown presently as first cartridge  404 ) such that the uppermost cartridge moves along a linear path defined by a bearing  446  in the coupling  434 . The slidable link is preferably a linear bearing  446  that is aligned with the vertical axis. To prevent the mechanism of the linear bearing  446  from becoming clogged with glue, a housing  448  is placed around the linear bearing  446 . This is especially beneficial in “bottom up” glue deposition, as it can protect the linear bearing  446  against accidental valve actuation (which generally results from an accidental scanner trigger from jammed sheets or cut-off tabs from a die cutter), where a pressurized stream of glue would otherwise splash the linear bearing  446  and adjacent components. In addition, housing  448  serves as a guard against dust and related airborne contaminants. Products to be glued, such as sheets (not presently shown), pass into the sheet travel path  430  in sequential fashion, to be channeled by the inlet guides  412  and  428 , which together define a convergent path along the sheet travel path  430  that narrows down to allow passage of the sheet between applicator head  420  and outlet guide  432 . Additional sheet inlet guiding is promoted by the inclusion of optional expansion guides  456  that axially align with the convergent path formed by inlet guides  412  and  428  along the length of the inlet guides, but also capture a larger space in front of the inlet guides. Gluing station  400  is mounted so that the lower surface configured to contact the product is in the same horizontal plane as the as the product&#39;s lower surface. Thus, where “top down” gluing is desired, the vertically uppermost part of outlet guide  432  is configured to be in the same horizontal plane as the bottom of a passing sheet, while in the “bottom up” configuration, the engaging surface of the applicator head  420  would be in the same horizontal plane as the sheet&#39;s downward-facing surface. The expansion guides  456  provide additional means of guidance and support in situations where the sheets being fed are not closely aligned with sheet travel path  430 . Such a case of misalignment may occur when a sheet with severe warpage is being fed into the gluing station  400 . Glue enters into valve  414  from a glue source through inlet port  416 , and passes through a quick-release coupler  422  and into applicator head  420 . Actuator power (be it electric or a pressurized fluid) enters through port  418 . Manually-depressible knobs  442  are spring-actuated to allow for quick-release of the cartridges  404 ,  424  from the variable coupling  434  and base structure  402 , respectively. 
   Referring next to  FIGS. 6A and 6B  in conjunction with  FIG. 3 , the placement of the applicator head  420  relative to the outlet guide  432  is relatively narrow along the vertical dimension such that even a thin sheet of corrugated paper passing between them will be in simultaneous contact with both. Outlet guide  432  is made up of a bracket with tangs  432 A that extend parallel to sheet travel path  430 . The tangs  432 A define a substantially smooth path over which the sheet will travel, and can be augmented by a pair of rollers  432 B mounted on a shaft connected to the tangs  432 A. These rollers  432 B can lower the frictional resistance that a passing sheet passing between them and applicator head  420  will experience, thus reducing the likelihood of sheet pinching and jamming. The position of the rollers  432 B along the sheet travel path  430  can be adjusted by moving the rollers  432 B along slotted rail  432 C defined in tangs  432 A. In operation, the sheet first encounters applicator head  420  which deposits one or more parallel rows of glue onto a surface of the sheet. The corrugated sheet is rigid enough that the sheet stays substantially flat between the small contact surface of applicator head  420  and outlet guide  432 . The vertical dimension of a gap  436  formed between the applicator head  420  and outlet guide  432  can vary, depending on the thickness of the sheet. This is accomplished when the leading edge  15  of sheet  10  contacts the uppermost cartridge (in this case, the first cartridge  404 ), which in turn causes the coupling  434  to move the applicator head  420  out of the sheet&#39;s way, while simultaneously compressing spring  438 . In addition, the width of gap  436  can be manually adjusted by varying a gap setting rod  439  disposed concentrically within spring  438 . This allows the force on the passing sheet  10  to be adjusted by changing the compression on the spring  438 . By being movably responsive to the passage of a thicker sheet, the coupling  434  reduces the likelihood of sheet pinching and jamming. Once the thick sheet has passed through gluing station  400 , the spring  438  forces the coupling  434  and mounted first cartridge  404  with applicator head  420  to return to a neutral position (which can be predetermined through adjustment of a pair of hex nuts threaded onto gap setting rod  439  within spring  438 ) to await the arrival of the next sheet. To avoid having to overcome inertial effects due to the weight of the cartridge  404 , a cartridge weight compensator  444  can be mounted between the base structure  402  and the coupling  434 . The compensator  444  is in the form of a fluid-charged (preferably air) cylinder that can produce an upward force that offsets the downward force exerted by the weight of cartridge  404 . 
   Referring next to  FIGS. 4A and 4B  in conjunction with  FIGS. 6A and 6B , details about the structure of the cartridges  404 ,  424  and their mounting scheme are shown. First mount  410  provides the primary backbone of first cartridge  404 . Valve  414  is affixed to first mount  410 , as is first inlet guide  412  and connecting pin  450 , the latter used to engage a spring-biased lock not shown). An aperture in mounting block  452  attached to base structure  402  accepts connecting pin  450 , while the manually-depressible knobs  442 , which are secured in mounting block  452 , are spring-biased to hold connecting pin  450  in place. Since connecting pin  450  is the only part of cartridge  404  being held in place, manual unlocking and disconnecting of the cartridge  404  can be easily accomplished. The aforementioned glue and actuation ports  416 ,  418  on valve  414  are connected to their respective sources with flexible lines (not shown). There is enough extra length (or “play”) in these lines to allow first cartridge  404  to be removed from the “top down” configuration shown, and placed in a “bottom up” configuration without having to disconnect the lines. Applicator head  420  is mounted directly to and fluidly coupled with valve  414  using a quick-release coupler  422 . Proper orientation between the bottom of valve  414  and applicator head is ensured through a slot and pin alignment mechanism  425 . Similarly, second mount  426  provides the primary backbone of second cartridge  424 . As with the first mount  410 , second mount  426  includes a connecting pin  450  to affect a mounting relationship between it and a mounting block  452  attached to the base structure  402 . Since the connection dimensions of the two cartridges and their respective mounts are the same, they may be interchanged through the quick-release features of the connecting pin  450  and manually-depressible knobs  442 . In addition to inlet guide  428  and connecting pin  450 , second mount  426  also holds outlet guide  432 , as well as a splash guard  433 . The splash guard  433  functions to deflect excess glue away from components that would otherwise get clogged up. 
   Referring next to  FIGS. 5A through 5D , details of the applicator head  420  are shown. A sandwich-like construction is made up of a glue inlet  420 A, glue outlet  420 B disposed opposite the glue inlet  420 A, and a shim  420 D containing a manifold between the two. The glue outlet  420 B terminates in an anvil  420 I with a plurality of apertures  420 C, while glue inlet  420 A terminates with an adapter  420 J that engages the quick-release coupler  422 . The shim  420 D is used to seal fluids between the anvil  420 I and the glue inlet  420 A. Flowpath  420 G is machined into the shim  420 D in a shape that will allow the glue to flow from the flow channel inlet  420 E to the apertures  420 C in such a way as to minimize air pocket formation, as well as to allow for a more even glue flow to all apertures. Such an arrangement also decreases latency upon the application and removal of glue pressure, as there is no tortuous path between glue inlet  420 A and flowpath  420 G, thereby minimizing the chance of glue buildup at bends or air pockets along the way. Once the glue enters the main chamber defining a glue flowpath  420 G, the flowpath&#39;s gradually tapered (rather than abruptly changing) shape allows the glue to spread along concentric cylindrical wavefronts such that by the time the waves reach the distal end  420 F of the flowpath, the flow to each of the linearly-arranged apertures  420 C is substantially equal, thus minimizing the chance of starving the outermost apertures. It will be appreciated by those skilled in the art that other diverging shapes besides the linear taper of glue flowpath  420 G shown in the figure could be utilized, so long as the flowpath avoids sharp turns and related tortuous paths that could lead to air pockets and an uneven distribution of glue in the plurality of apertures  420 C. For example, glue flowpath  420 G can take on a fluted or parabolic shape. Although shim  420 D is shown as a single layer design in  FIGS. 5A and 5B , it could also employ multiple shim layers, or plates, to increase the vertical dimension of the glue&#39;s flowpath, or to provide different flow channel configurations. For example, as shown in  FIG. 5D. a  multi-layer approach could be used where a plurality of internal apertures making up flowpath  420 G could be arranged on one or more of the plates to ensure a generally even distribution of glue to all of the apertures  420 C. Such a configuration allows the glue flow to be tailored to match differing glue viscosity and pressure. Varying the number of plates, or changing plate thickness can also be used to increase or decrease glue flow, as needed. In operation, glue passing through applicator head  420  passes through the apertures  420 C on the faceted anvil  420 I as the anvil contacts passing sheets. The anvil  420 I gradually tapers inward along the direction of the sheet travel path  430  (shown with particularity in  FIG. 5A ) to coax the sheet away from any normal edges that might otherwise snag a sheet feed edge  13  or  15  (shown in FIG.  2 ). More pronounced lateral tapers lead up to the plurality of apertures  420 C arranged at the anvil&#39;s plateau. Downstream of the plateau and the apertures  420 C disposed therein, the anvil drops off with a pronounced taper to avoid buildup of excess glue along a sheet-engaging surface of the glue outlet  420 B. The apertures  420 C can be recessed slightly from the engaging surface of the plateau, and may further include recessed flow channels  420 H that surround each aperture to promote parallel deposition of the glue to the sheet travel path. This also allows minimum spacing from the orifice to the sheet  10 , thus reducing trailing glue patterns. Referring with particularity to  FIG. 5C , the position of the applicator head  420  relative to a tab  20  of sheet  10  is shown. The faceted head on anvil  420 I stays between the score line  22  and the edge of tab  20  to ensure flat contact between the apertures in the anvil and the tab  20 . 
   Referring next to  FIGS. 7A ,  7 B,  8 A and  8 B in conjunction with  FIG. 2 , elevation views of both “top down” ( FIGS. 7A and 8A ) and “bottom up” ( FIGS. 7B and 8B ) glue deposition are shown. The simultaneous use of two of the gluing stations  400 , such as that of  FIGS. 7A and 8A  together, or  FIGS. 7B and 8B  together, can produce rows of glue on both the aforementioned fourth panel  12  and tab  20  in a single pass. Comparing  FIG. 7A  to  FIG. 7B  (and  FIG. 8A  to FIG.  8 B), it can be seen that the first cartridge  404  is interchangeable with second cartridge  424 , and that regardless of orientation, the continual cooperation between a passing sheet  10  along sheet travel path  430  and the upper cartridge ( 404  in  FIGS. 7A and 8A , and  424  in  FIGS. 7B and 8B ) and spring  438  through coupling  434  and cartridge weight compensator  444  is ensured. 
   Referring next to  FIGS. 9A and 9B , a remote, or “fourth panel” setup of gluing station  400  is shown, with the cartridges removed to show more clearly the construction and vertical movement of the variable coupling  434  in response to the presence of a thick sheet  10  of corrugated cardboard at applicator head (not presently shown). While the bottom mounting block  452  remains stationary (being fixed to the base structure  402 ) the variable coupling  434  (which is coupled to cartridge weight compensator  444  and includes sled  454 , spring  438 , mounting block  452 , gap setting rod  439  with hex nuts and slidable bearing  446  with housing  448 ), translates along the vertical direction (as shown in  FIG. 9B ) in an amount proportional to the thickness of sheet  10 . The restoring force inherent in spring  438  is sufficient to return the variable coupling  434  to its neutral position once the sheet  10  has passed. Sled  454 , which is attached to the top mounting block  452 , acts as a mounting rail to which gap setting rod  439 , bearing  446  and housing  448  and one of the cartridges (not presently shown) are attached. A plunger mounted to sled  454  also moves in and out of cartridge weight compensator  444  in response to sled movement, and its piston-like presence in the compensator produces a resistance therein that keeps the pressure on the passing sheet relatively constant. Cartridge weight compensator  444  is an air cylinder that acts as a counterweight. By applying air pressure to the cylinder, some or all of the weight of the cartridge is relieved or cancelled out, thereby making it easier for the passing sheet  10  to lift the sled  454 . The spring  438  keeps pressure against the cartridge weight compensator  444 , thus allowing the applicator head  420  to stay in contact with the sheet  10  and avoid bouncing. The combination of the spring  438  and cartridge weight compensator  444  results in the applicator head  420  behaving like a spring-mass-damper dashpot: as the sled  454  moves in a downward direction, this dampens the bouncing due to the spring  438 , as the compressed air acts to decelerate the downward motion. 
   While certain representative embodiments and details have been shown for purposes of illustrating the invention, it will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention, which is defined in the appended claims.