Adhesive dispensing nozzles for producing partial spray patterns

0001The invention relates to a system for applying fluids including fiberised adhesives onto a substrate from at least one of three or more different die assemblies mounted on a mounting surface of a manifold that supplies fluid to the at least one die assembly. The purpose of such a system is to dispense fluids onto e.g. moving substrates, and more particularly to dispense adhesives in partial spray patterns for partially covering a substrate, and still more particularly to supply adhesive to a plurality meltblowing die assemblies configured for partially covering a substrate with adhesive.

0002The application of adhesives onto moving substrates is known and has many applications. Adhesives are used, for example, to bond overlapping substrate layers in the production of a variety of bodily fluid absorbing hygienic articles, including disposable diapers and incontinence pads, sanitary napkins, patient underlays, and surgical dressings. Known systems include generally a plurality of adhesive dispensing spray nozzles arranged in one or more arrays extending across a moving substrate for applying an adhesive layer or film thereon. Other systems include one or more die assemblies having a plurality of adhesive dispensing orifices arranged in an array, wherein the die assemblies are sometimes arrangeable side by side to extend the array lengthwise.

0003<patcit id="pcit0001" dnum="EP0872580A"><text>EP-A-0872580</text></patcit> discloses a plurality of meltblowing die assemblies, or nozzles, mountable side by side on one or both ends of a common manifold, or head, which provides a metered supply of adhesive to each die assembly. The die assemblies each comprise a plurality of substantially parallel plate members forming an array of adhesive dispensing orifices on a dispensing surface thereof. The array of fluid dispensing orifices of each die assembly compose a section of a longer array formed by the plurality of adjacent die assemblies disposed along a common end of the manifold. One or both sides of the manifold may be mounted adjacent the side of a similarly configured manifold to form still longer arrays of fluid dispensing orifices, thereby providing a modular meltblowing adhesive dispensing system that accommodates substrates having any dimensional width.

0004In some adhesive dispensing applications, the adhesive is applied to cover the full width of the substrate, and in other applications it is desirable to apply the adhesive to cover only select portions of the substrate leaving other portions thereof without adhesive coverage. In the manufacture of bodily fluid absorbing hygienic articles, for example, it is desirable to film different sized areas of adhesive noncoverage, which may correspond to cut away areas thereof or may be designated for insertion of an elastic band. In these and other applications the areas of adhesive noncoverage may be as narrow as one-eighth of an inch or less and may be as wide as one or many inches, depending on the particular application requirements.

0005In the past, the supply of adhesive from the manifold to one or more die assemblies has been interrupted to provide one or more corresponding gaps in adhesive coverage on the substrate. <patcit id="pcit0002" dnum="US5421941A"><text>US-A-5,421,941</text></patcit> among related patents, for example, disclose a common manifold for selectively intermittently supplying adhesive to a series of meltblowing die assemblies mounted thereon. In FIGS. 1 and 4 of <patcit id="pcit0003" dnum="US5421941A"><text>US-A-5,421,941</text></patcit>, the die assemblies are constructed to leave continuous strips of adhesive non-coverage along the length of the substrate, but the particular structure that provides this effect is not disclosed specifically. Notably, in FIG. 2 of <patcit id="pcit0004" dnum="US5421941A"><text>US-A-5,421,941</text></patcit>, the side by side arrangement of die assemblies does not provide consistent spacing between the fluid dispensing orifices thereof, evidenced by a gap between the orifices of adjacent die assemblies, suggesting that adhesive coverage on the substrate is not continuous, or at least not uniform, particularly in areas between adjacent die assemblies void of fluid dispensing orifices.

0006The selective interruption of adhesive supplied to one or more die assemblies to form areas of adhesive non-coverage limits the corresponding gaps or areas of non-coverage to the width of the die assembly to which fluid flow is interrupted, and more generally in proportion to multiples of the spray pattern width corresponding thereto, provided the system comprises several die assemblies having the same width. In <patcit id="pcit0005" dnum="EP0872580A"><text>EP-A-0872580</text></patcit> the meltblowing die assemblies are one inch wide (2.5mm), and generally produce a substantially correspondingly wide spray pattern on the substrate. Thus, interruption of fluid flow to the die assembly or replacement thereof by a blocking plate, which may recirculate fluid back to the manifold, results in an area of adhesive non-coverage approximately inch wide, depending upon the divergence or convergence of adhesive sprayed from adjacent die assemblies.

0007Some adhesive dispensing manifolds are configured with an array of adhesive dispensing nozzles on opposing end portions thereof, wherein the array of die assemblies on one end of the manifold are offset relative to the array of die assemblies on the other end of the manifold. The offset is usually one-half the width of the die assembly. The gap or area of adhesive non-coverage may thus be reduced to a dimension corresponding to the amount of offset upon interruption of fluid flow to overlapping die assemblies on opposing ends of the manifold. But this approach continues to limit the area of adhesive non-coverage in proportion to multiples of the offset between die assemblies, which is fixed.

0008Others have suggested rotating or otherwise tilting the manifold relative to the moving substrate to variably reduce the areas of adhesive non-coverage resulting from interruption of the fluid supply or removal of one or more die assemblies from the manifold. This approach however does not provide precise and consistent control of the gaps or areas not covered by adhesive. And, as with the other approaches discussed, does not permit variability among more than one area of adhesive non-coverage, since rotating or tilting the manifold reduces each gap the same extent.

0009<patcit id="pcit0006" dnum="US5145689A"><text>US-A-5145689</text></patcit> discloses a meltblowing die assembly capable of intermittent operation by selectively shutting off polymer flow.

0010The present invention is drawn toward advancements in the art of dispensing fluids onto moving substrates that overcome problems in the prior art economically.

0011The present invention exists as a system according to claim 1.

0012Particular embodiments of the invention are the subject of the dependent claims.

0013The invention will now be described with reference to the accompanying drawings; in which:- <ul id="ul0001" list-style="none" compact="compact"><li>FIG. 1 is a modular system for applying fluids including fiberized adhesives onto substrates according to an exemplary embodiment of the invention;</li><li>FIG. 2a is a first modified plate for dispensing partial fluid patterns from a meltblowing die assembly;</li><li>FIG. 2b is a second modified plate for dispensing partial fluid patterns from a meltblowing die assembly;</li><li>FIG. 2c is a third modified plate for dispensing partial fluid patterns meltblowing die assembly; and,</li><li>FIG. 1 is a system 100 for applying fluids including fiberized adhesives onto a substrate S, which in the exemplary embodiment is a material used in the manufacture of bodily fluid absorbing hygienic articles, including disposable diapers and incontinence pads, sanitary napkins, patient underlays, and surgical dressings. The invention is more generally applicable to selectively applying fluids to portions of any substrate.</li></ul>

0014The system 100 comprises generally a plurality of die assemblies 110-116 mountable side by side on a common manifold 120, or head, and more particularly on one or both ends 122 thereof, which provides a metered supply of adhesive thereto, whereby the die assemblies and manifold form a modular assembly as disclosed more fully in <patcit id="pcit0007" dnum="EP0872580A"><text>EP-A-0872580</text></patcit>.

0015The plurality of die assemblies 110 of the exemplary embodiments each include a plurality of fluid dispensing orifices 12 disposed on a dispensing surface 14 thereof. The fluid dispensing orifices 12 are arranged at least partially across a width extending from a right side 16 of the die assembly to a left side 18 thereof. The die assemblies of the exemplary embodiments are, more particularly, meltblowing die assemblies, or nozzles, mountable on a manifold to form a modular assembly useable for dispensing or spraying fiberized hot melt adhesives onto substrates. The meltblowing die assemblies of this preferred exemplary type each comprise generally a plurality of laminated members, or plates, defining the plurality of fluid dispensing orifices 12 as disclosed more fully in <patcit id="pcit0008" dnum="EP0835952A"><text>EP-A-0835952</text></patcit> and in <patcit id="pcit0009" dnum="EP0872580A"><text>EP-A-0872580</text></patcit>. The die assemblies 110 may alternatively be of the type disclosed in <patcit id="pcit0010" dnum="US5421941A"><text>US-A-5,421,941</text></patcit> wherein the orifices are formed by precision drilling operations, among other types of die assemblies mountable onto a manifold to form a modular assembly.

0016In one preferred embodiment, the plurality of die assemblies 110-116 are mountable on a common mounting surface 122 of the manifold 120 to form the modular assembly. And in a related preferred embodiment, the plurality of die assemblies are arranged on the manifold 120 so that the plurality of fluid dispensing orifices 12 thereof form not more than a single substantially linear array of fluid dispensing orifices. The single substantially linear array of fluid dispensing orifices may however be piece-wise linear insofar as the invention is directed toward partially covering the substrate S with fluids dispensed from die assemblies 110 having fluid dispensing orifices selectively disposed on or across portions thereof and not on other remaining portions thereof as discussed further below. And although the plurality of die assemblies are configured to dispense or spray partial fluid patterns onto the substrate S as discussed further below, die assemblies positioned adjacently on the manifold 120 are preferably configured generally to provide a substantially continuous, or seamless, application of fluid onto the substrate, except in areas of the substrate where adhesive non-coverage is desired. Alternatively, the plurality of die assemblies may be arranged to form one or more arrays of fluid dispensing orifices on one or both ends of the manifold 120, wherein the one or more arrays of fluid dispensing orifices are configured selectively to produce areas of adhesive non-coverage onto the substrate.

0017FIG. 1 illustrates generally the plurality of die assemblies 110-116 having a plurality of fluid dispensing orifices 12 disposed on select portions of the dispensing surface 14 and other remaining portions thereof void of fluid dispensing orifices 12. The fluid dispensing orifices 12 are not shown clearly in FIG. 1, but the illustrated partial fluid dispensing, or spraying, patterns corresponding thereto are indicative of the locations of the fluid dispensing orifices 12, which are illustrated more particularly in FIG. 2 and discussed further below. The plurality of die assemblies 110-116 thus apply fluid only to portions of the substrate substantially opposite the fluid dispensing orifices thereon, and not to other portions of the substrate substantially opposite the remaining portions thereof void of fluid dispensing orifices.

0018Generally, each of a plurality of die assemblies mounted on the manifold 120 may be, but is not necessarily, selected from a group consisting essentially of die assemblies that dispense one of the exemplary partial fluid patterns illustrated generally in FIG. 1 and discussed further below to form combinations thereof suitable for a particular application. Notably, the exemplary die assembly configurations of FIG. 1 provide partial dispensing patterns not obtainable by blocking or interrupting fluid supplied to one or more die assemblies having orifices disposed across the full width between right and left sides thereof.

0019FIG. 1 illustrates the exemplary die assembly 110 including a plurality of fluid dispensing orifices 12 disposed across a right side portion 11 of the dispensing surface 14 thereof, and extending from the right side 16 of the die assembly 110 toward an intermediate portion thereof. A remaining portion of the dispensing surface 14 extending from the intermediate portion thereof toward the left side of the die assembly 110 is void of fluid dispensing orifices. The die assembly 110 thus applies fluid to portions of the substrate substantially opposite the fluid dispensing orifices on the right side portion 11 thereof, but not to other portions of the substrate substantially opposite the remaining portion of the die assembly 110 void of fluid dispensing orifices.

0020FIG. 1 illustrates the exemplary die assembly 116 including a plurality of fluid dispensing orifices 12 disposed across a left side portion 13 of the dispensing surface 14 thereof, and extending from the left side 18 of the die assembly 116 toward a first intermediate portion thereof. A remaining portion of the dispensing surface 14 extending from the intermediate portion thereof toward the right side of the die assembly 116 is void of fluid dispensing orifices. The die assembly 116 thus applies fluid to portions of the substrate substantially opposite the fluid dispensing orifices on the left side portion 13 thereof, but not to other portions of the substrate substantially opposite the remaining portion of the die assembly 116 void of fluid dispensing orifices.

0021The die assemblies 110 and 116 are generally reverse configurations of each other, and in some applications may be exact mirror images of each other, wherein generally the fluid dispensing orifices of one die assembly are disposed on the opposite side thereof as the fluid dispensing orifices of the other die assembly. The widthwise portion of the dispensing surface 14 having the fluid dispensing orifices 12 is however generally different for the die assemblies 110 and 116. Generally, the die assemblies 110 and 116 are mountable side by side on the manifold 120 so that the corresponding fluid dispensing orifices 12 thereof are positionable adjacent each other or separated from each other by the corresponding remaining portions thereof void of fluid dispensing orifices.

0022FIG. 1 illustrates the exemplary die assembly 112 including a plurality of fluid dispensing orifices 12 disposed across an intermediate portion 15 of the dispensing surface 14 thereof. The fluid dispensing orifices 12 are spaced away from the right and left sides 16 and 18 of the second die assembly 112, wherein remaining right and left lateral portions of the dispensing surface 14 thereof are void of fluid dispensing orifices. The die assembly 112 thus applies fluid to portions of the substrate substantially opposite the fluid dispensing orifices 12 on the intermediate portion 15 thereof, but not to other portions of the substrate substantially opposite the remaining right and left lateral portions of the die assembly 112 void of fluid dispensing orifices.

0023FIG. 1 illustrates also the exemplary die assembly 114 including a plurality of fluid dispensing orifices 12 disposed across right and left lateral portions 17 and 19 of the dispensing surface 14 thereof, and extending inwardly from the right and left sides 16 and 18 of the die assembly 114. A remaining intermediate portion of the dispensing surface 14 spaced away from the right and left sides 16 and 18 of the die assembly 114 is void of fluid dispensing orifices. The die assembly 114 thus applies fluid to portions of the substrate substantially opposite the fluid dispensing orifices 12 on the right and left lateral portions 17 and 19 thereof, but not to other portions of the substrate substantially opposite the remaining intermediate portion of the die assembly 114 void of fluid dispensing orifices.

0024In hot melt adhesive spraying applications applied with a meltblowing die assembly of the type disclosed in <patcit id="pcit0011" dnum="EP0835952A"><text>EP-A-0835952</text></patcit> and in <patcit id="pcit0012" dnum="EP0872580A"><text>EP-A-0872580</text></patcit> presently, the minimum reasonably controllable area of adhesive coverage or adhesive non-coverage on the substrate is approximately 1/8 inches (4mm). Although in other applications, the minimum controllable area may be less, depending on several parameters including the spacing between the die assembly and the substrate.

0025Thus, in one exemplary embodiment, the right and left side portions 11 and 13 of the dispensing surfaces 14 of the die assemblies 110 and 116 having the plurality of fluid dispensing orifices 12 has a minimum width of approximately 1/16 inches (2mm). Similarly, the remaining portion of the dispensing surface 14 void of fluid dispensing orifices has a minimum width of approximately 1/16 inches (2mm). As discussed above, the die assemblies 110 and 116 may thus be positioned adjacent to each other to form either a minimum 1/8 inch (4mm) wide area of fluid coverage on the substrate or a minimum 1/8 inch (4mm) wide area of fluid non-coverage on the substrate. These widths may generally be much larger so long as the minimum width of the complementary portion with or without fluid dispensing orifices is not less than its specified minimum, which in the exemplary embodiment is 1/16 inches (2mm) for the general configurations of die assemblies 110 and 116.

0026According to the exemplary embodiment, a one inch wide die assembly having fluid dispensing orifices 12 disposed along 1/16 inches (2mm) of the right or left side portion of the dispensing surface 14 thereof thus has approximately 15/16 inches (23mm) of the remaining portion of the dispensing surface 14 void of fluid dispensing orifices. And similarly, a one inch wide die assembly having fluid dispensing orifices 12 disposed along 15/16 inches (23mm) of the right or left side portion of the dispensing surface 14 thereof has approximately 1/16 inches (2mm) of the remaining portion of the dispensing surface 14 void of fluid dispensing orifices.

0027In the exemplary embodiment, the intermediate portion 15 of the die assembly 112 having the plurality of fluid dispensing orifices has a minimum width of approximately 1/8 inches (4mm), and the remaining right and left lateral side portions of the die assembly 112 void of fluid dispensing orifices have minimum widths of approximately 1/16 inches (2mm). Similarly, the right and left lateral side portions 17 and 19 of the die assembly 115 having the plurality of fluid dispensing orifices have minimum widths of approximately 1/16 inches (2mm), and the remaining intermediate portion of the die assembly 114 void of fluid dispensing orifices has a minimum width of approximately 1/8 inches (4mm).

0028The exemplary die assemblies illustrated generally in FIG. 1 and disclosed more particularly above may be used generally in combination with one another and with other die assemblies having fluid dispensing orifices 12 disposed across a full width of the dispensing surface 14, not shown but disclosed in <patcit id="pcit0013" dnum="EP0835952A"><text>EP-A-0835952</text></patcit> and in <patcit id="pcit0014" dnum="EP0872580A"><text>EP-A-0872580</text></patcit>.

0029The fluid supplied to any one or more of the die assemblies mounted on the manifold 120 may be interrupted to provide additional control over fluid applied or sprayed onto the substrate. Additionally, one or more die assemblies, usually those having fluid dispensing orifices disposed across a full width thereof, may be removed and replaced with a blocking plate, which may recirculate fluid back to the manifold, as is known. The particular combination of die assemblies mounted on the manifold 120 is dependant generally on the particular application requirements. The availability of die assemblies that dispense a variety of partial fluid patterns shown generally in FIG. 1 and discussed more particularly herein substantially improves the adaptability and range of applications for modular fluid dispensing systems having three or more die assemblies mountable on a manifold for applying fluids, and especially spraying fiberized hot melt adhesive, onto substrates.

0030As discussed above, the die assemblies 110 of the exemplary embodiment each comprise a plurality of substantially parallel plate members, shown generally in FIG. 1, forming the fluid dispensing orifices 12, wherein each of the plurality of fluid dispensing orifices 12 of the plurality of die assemblies is flanked by an air dispensing orifice disposed on opposing sides of the fluid dispensing orifice, as disclosed more fully in <patcit id="pcit0015" dnum="EP0835952A"><text>EP-A-0835952</text></patcit> and in <patcit id="pcit0016" dnum="EP0872580A"><text>EP-A-0872580</text></patcit>.

0031FIGS.2a-2c illustrate three exemplary plates 130,150 and 170 composing in combination a portion of a meltblowing die assembly comprising a plurality of substantially parallel plates defining a plurality of fluid dispensing orifices arranged partially across a width extending from a right side of the die assembly to a left side thereof. The three plates of FIGS. 2a-2c are, more particularly, useable to replace the three plates illustrated in FIGS. 2d-2f of <patcit id="pcit0017" dnum="EP0872580A"><text>EP-A-0872580</text></patcit> thereby forming a meltblowing die assembly having a partial fluid dispensing pattern illustrated generally by the die assembly 110 in FIG. 1. The plates of FIGS. 2a-2c may also be configured to form meltblowing die assemblies having one of the partial fluid dispensing patterns illustrated generally by the die assemblies 112, 114 and 116 in FIG. 1 and disclosed more particularly hereinabove.

0032The exemplary plate of FIG. 2b includes a plurality of fluid dispensing orifices 12 disposed across a dispensing surface portion 152 between right and left sides 154 and 156 thereof. A remaining dispensing surface portion 158 is void of fluid dispensing orifices 12, whereby the corresponding die assembly incorporating the plate 150 produces a partial fluid dispensing pattern of the form illustrated generally by the die assembly 110 of FIG. 1. The plate 130 includes a corresponding plurality of fluid supply conduit portions 132, which supply fluid from a common fluid cavity 134 of the plate 130, in communication with a corresponding one of the plurality of fluid dispensing orifices 12 of the plate 150 when the plates 130 and 150 are matably coupled as disclosed more fully in <patcit id="pcit0018" dnum="EP0872580A"><text>EP-A-0872580</text></patcit>. The plates 130 and 150 may of course be configured to produce any one of the partial fluid dispensing patterns illustrated generally in FIG. 1 and disclosed more particularly hereinabove. The plate 150 may also include fluid dispensing orifices having greater or lesser density, depending on application requirements.

0033FIG. 2b illustrates each of the plurality of fluid dispensing orifices 12 flanked by an air dispensing orifice 151 disposed on opposing sides of the corresponding fluid dispensing orifice 12. The plate 170 includes a corresponding plurality of air supply conduit portions 172, which supply air from a common air cavity 174 of the plate 170, in communication with a corresponding one of the plurality of air dispensing orifices 151 of the plate 150 when the plates 170 and 150 are matably coupled as disclosed more fully in <patcit id="pcit0019" dnum="EP0872580A"><text>EP-A-0872580</text></patcit>. The spacing and relative angle between the fluid and air orifices affects oscillation parameters of fluid dispensed therefrom including the frequency and amplitude thereof as discussed more fully in <patcit id="pcit0020" dnum="EP0835952A"><text>EP-A-0835952</text></patcit> and in <patcit id="pcit0021" dnum="EP0872580A"><text>EP-A-0872580</text></patcit>.

0034FIG.2b also illustrates an-alternative embodiment wherein the remaining dispensing surface portion 158 void of fluid dispensing orifice 12 includes air dispensing orifices 153. The air dispensing orifices 153 improve fluid flow control by reducing a tendency of fluid dispensed from the endmost fluid dispensing orifices 12 to diverge, or stray laterally, thereby providing a more well defined boundary or interface between areas fluid coverage and non-coverage on the substrate. In the plate of FIG. 2b, for example, without the air dispensing orifices 153, the leftmost fluid dispensing orifices, and particularly the leftmost orifice, has a tendency to diverge toward the left side 158 of the plate or corresponding die assembly. The general concept of providing one or more additional air dispensing orifices adjacent an endmost fluid dispensing orifice to provide improved control over fluid dispensed therefrom, particularly where the endmost fluid dispensing orifice defines an interface between areas of fluid coverage and non-coverage on the substrate, is applicable to any of the die assemblies disclosed herein as well as to the meltblowing die assemblies disclosed in copending <patcit id="pcit0022" dnum="EP0835952A"><text>EP-A-0835952</text></patcit> and in <patcit id="pcit0023" dnum="EP0872580A"><text>EP-A-0872580</text></patcit>.

0035According to another aspect of the invention, control over the boundary or interface between areas of the substrate having fluid coverage and non-coverage is improved by decreasing the amplitude of oscillation of the fluid dispensed from the fluid dispensing orifices on the die assembly approaching and defining the boundary between areas of fluid coverage and non-coverage on the substrate. In one preferred embodiment, the oscillation amplitude of fluid is increasingly decreased in the several fluid dispensing orifices toward at least one endmost fluid dispensing orifice defining the interface between areas of fluid coverage and non-coverage on the substrate, whereby the at least one endmost fluid dispensing orifice has a smallest oscillation amplitude. Each die assembly has at least two and possibly more fluid dispensing orifices, depending on the configuration thereof, that dispense fluid defining boundaries between areas of fluid coverage and non-coverage on the substrate.

0036FIG. 2b illustrates, for example, the air dispensing orifices 151 being disposed increasingly farther away from the corresponding fluid dispensing orifices 12 toward the left side 156 of the plate 150, thereby increasingly decreasing the oscillation amplitude of fluid dispensed from the respective fluid dispensing orifices, whereby fluid dispensed from the endmost fluid dispensing orifice has the smallest oscillation amplitude, which is controllable most accurately, thereby providing a most well defined boundary. The oscillation amplitude may alternatively be controlled, that is increased or decreased, by varying a relative angle between the fluid and air dispensing orifices.

0037According to a related aspect of the invention, the fluid supplied to the fluid dispensing orifices having fluid flows with reduced oscillation amplitudes is correspondingly reduced, since less fluid is required for smaller oscillation amplitude. The corresponding air dispensing orifices may be reduced similarly, since the reduced fluid flows may be controlled with reduced air flows.