EP1447142A1

EP1447142A1 - Fluid applicator and method

Info

Publication number: EP1447142A1
Application number: EP03003051A
Authority: EP
Inventors: Lennart Vesterlund
Original assignee: Akzo Nobel NV
Current assignee: Akzo Nobel NV
Priority date: 2003-02-12
Filing date: 2003-02-12
Publication date: 2004-08-18

Abstract

An applicator (10,20) and method for spreading a fluid to a substrate is disclosed, comprising a housing (11,21) with an inlet end (14,24) and an outlet end (16,26), the inlet end having an inlet (13,23) connectable to a fluid supply, and the outlet end having multiple nozzles (15,25) arranged in at least one row for spreading the fluid in parallel fluid strands. The applicator further comprises a continuous duct (12,22) distributing the fluid from the inlet to the nozzles, the flow duct in a first plane having a length (1) in the flow direction (F) and a width (w) across the direction of flow through the duct, the width increasing from the inlet end to encompass the row of nozzles at the outlet end.

Description

FIELD OF THE INVENTION

The present invention relates to an applicator and method for application of a fluid to a substrate.

BACKGROUND OF THE INVENTION

In the production of laminated structures wherein two or more elements are laminated by being glued together face to face, such as in the production of load-carrying wooden beams or joists for buildings, flooring panels, doors, cabinet doors, furniture etc., adhesive is typically applied through one or several extruders as the elements are continuously advanced below the extruders to receive an adhesive layer that covers the top surface of the elements. The coated elements are then pressed together to form a consolidated laminate structure.
Usually, the adhesive is fed from a reservoir and circulated through an applicator having a number of openings arranged in a discharge end, and through which adhesive strands are discharged transversely to the feed direction of the substrates.
WO 99/65612 discloses an applicator for spreading a fluid, such as an adhesive, in a thin layer on the surface of a substrate. The applicator comprises a plurality of nozzles arranged in rows on an applicator housing, and through which the fluid is discharged towards a receiving substrate. The fluid is distributed in opposite directions from an inlet that mouths in the centre of an elongate channel, connecting all the nozzles to the inlet via common flow paths.
WO 99/67027 discloses an arrangement for separate application of fluid components onto a substrate in a gluing system, such as a system comprising a resin component and a hardener component. Each component is applied from a separate unit, each unit comprising at least one hollow member provided with an inlet and a number of openings through which the component is discharged to be received by the substrate.
Production of laminated wood and glue-laminated timber usually involves gluing together two or more wooden member surfaces by means of a multi-component adhesive system, such as adhesive systems based on urea-formaldehyde (UF) resins, melamine-formaldehyde (MF) resins, melamine-urea-formaldehyde (MUF) resins, phenol-formaldehyde (PF) resins, phenol-resorcinol-formaldehyde (PRF) resins, isocyanate resins, polyurethane (PUR) resins, polyvinyl acetate resins, etc. Such adhesive systems are usually based on at least two components, a resin component and a hardener component.
Conventional pipe spreaders for application of adhesives often suffer from the problem of entrapments unintentionally formed in the flow passage, and where the fluid is susceptible of stagnation, i.e. the fluid being slowed down or completely taken out of circulation. The stagnating adhesive may then harden or cause further stagnation that finally leads to clogging of the spreader/spreader nozzles. Most spreaders therefore require cleaning on a frequent basis, resulting in production stops as well as to an economically and environmentally unfavourable loss of adhesive.
WO 99/65612 addresses the problems connected with cleaning by providing a disposable spreader insert that protects the spreader housing and nozzles.
Another problem related with prior art spreaders is that the amount of adhesive, exiting per unit time through the nozzles, is not uniform over the entire row of nozzles. To be more specific, the volume flow rate through the nozzles decreases with increasing distance between the fluid inlet and the fluid outlet. Consequently, more fluid per unit time exits through a nozzle located close to the inlet, than through a distant nozzle. This effect counteracts a uniform application of adhesive transversely to the feed direction of the substrate, which in turn may cause an irregular bonding between the components in a laminated structure.
Hence there is a need for an improved spreader for applying fluids such as adhesives to a substrate. In particular, the problems of fluid stagnation and clogging should be avoided, as well as the problem of non-uniform application of fluid. Moreover, a spreader is desired that provides extended operational time between cleaning stops, and a reduced wastage of adhesive. The object of the present invention is to provide a fluid applicator and method meeting with these needs.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided a method and an applicator for application of fluids such as adhesive systems, or resin and hardener components of an adhesive system, to a substrate, the applicator comprising a housing with an inlet end and an outlet end: the inlet end is connectable to a fluid supply, and the outlet end has a multiplicity of nozzles arranged in at least one row for discharge of fluid in parallel fluid strands. The housing defines a continuous duct directing a fluid flow from the inlet to the nozzles: in a first plane, the flow duct has a length in the flow direction and a width across the direction of flow. The width of the duct is increasing from the inlet end substantially to encompass the length of the row of nozzles at the outlet end.
The length of the duct preferably is dimensioned such that a flow path length from the inlet to any nozzle in the row of nozzles amounts to at least half the length of the row of nozzles at the outlet end.
An advantageous embodiment foresees, that all nozzles are equally distanced from the inlet by being arranged on the arc of a circle, the centre of which is located at the fluid inlet.
In yet another embodiment the sectional area of the duct is substantially maintained from the inlet end to the outlet end by means of a reducing duct height, the reduction being reciprocally proportional to the increasing width of the duct.
Still another embodiment foresees that a labyrinth is arranged in the duct for splitting the fluid flow into divisional flow paths, further reducing a difference in flow path length between the inlet and any two nozzles in the row of nozzles.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other embodiments and advantageous features of the invention will be more fully described below, reference being made to the attached diagrammatic drawings wherein
Fig 1 is a partially sectioned front view showing a first embodiment of the new applicator;
Fig. 2 is a sectional view along the line II-II of fig. 1;
Fig. 3 is a partially sectioned front view showing a second embodiment of the applicator;
Fig. 4 is a sectional view along the line IV-IV of fig. 3;
Fig. 5 is a horizontal implementation of the embodiment of figs. 3 and 4;
Fig. 6 is vertical implementation of the embodiment of figs. 1 and 2;
Fig. 7 is sectional front view showing the new applicator in a further developed embodiment;
Fig. 8 is a sectional front view showing the new applicator in yet a further developed embodiment;
Fig. 9 illustrates diagrammatically a modulated fluid flow in a method according to the invention;
Fig. 10 illustrates diagrammatically a horizontal assembly of multiple applicators in a production setup, and
Fig. 11 illustrates diagrammatically a vertical assembly of multiple applicators in a production setup.

DETAILED DESCRIPTION OF THE INVENTION

Generally, and a common feature in all embodiments of the new applicator, the geometry is designed to provide substantially identical fluid flow between the fluid inlet and each discharge opening or nozzle in an applicator, capable of a wide and uniform distribution of fluid to a substrate. In this context, flow path length and resistance are considered as decisive parameters for obtaining the uniform discharge of fluid over the entire operational spreading width of the applicator, and hence over the entire width of the substrate.
Basically, the invention suggests a triangular geometry for an applicator wherein a fluid inlet is arranged in the apex of the triangle and one or more rows of nozzles are arranged on the base line. The height of the triangle, i.e. the distance from the fluid inlet transversely to the row of nozzles, will decide the nominal differences in flow path length between the inlet and the nozzles in the row. The greater the height, the smaller the differences. In order to secure an operative effect it is deemed sufficient, in practice, when the height at least amounts to half the length of the base line. In other words: the flow path length between the inlet and any nozzle amounts to at least half the operational width of the applicator. However, other proportions of the triangular geometry may also be effective, specifically in combination with further measures to manipulate the flow path lengths through the applicator as disclosed below. Preferably, the applicator is configured as an isosceles triangle, but other triangular geometries may also be conceivable.
A first embodiment of the new applicator will now be described with reference to figs. 1 and 2. The applicator 10 comprises a housing 11, enclosing a duct 12 directing the flow of a fluid form an inlet 13 at an inlet end 14 of the housing, to at least one row of discharge nozzles 15 arranged at an outlet end 16 of the housing 11. The housing 11 has a front face 17 and a back face 18, spaced in superposed relation by means of an interconnecting frame element 19. The inlet 13 is connectable to a fluid supply, and the nozzles 15 are equally spaced on a rectilinear row and designed to discharge the fluid in the form of parallel fluid strands.
As best seen in fig. 2, the applicator 10 is designed to deflect the incoming fluid F transversely through the duct, and then once more transversely through the nozzles. The applicator of figs. 1 and 2 is thus designed for a horizontal orientation in a production line, discharging the fluid F vertically to a substrate (not shown) that is advanced below the applicator.
As best seen in fig. 1, the applicator 10 basically has a triangular outline, the inlet 13 being arranged in the apex and the row/rows of nozzles 15 being arranged on the base line of the triangle. In a first plane, parallel to the drawing of fig. 1, the flow directing duct 12 has a flow path length 1 and a flow path width w. The duct width w increases from the inlet end towards the outlet end, basically to encompass the entire row of nozzles at the outlet end. The diverging geometry of the duct provides a non-obstructed fluid flow from the inlet 13 to each individual nozzle 15. In other words, each nozzle 15 is provided a direct communication with the inlet, without its flow path crossing or mixing with the flow path of another nozzle in the row. The duct length 1 preferably is dimensioned such that the distance/flow path length between the inlet 13 and any nozzle 15 in the row of nozzles amounts to at least half the length of the row of nozzles at the outlet end.
Modifications to the basic concept realized in the applicator 10 may involve a progressively increasing or flaring duct width w. Another modification may include an inlet that is aligned with the fluid direction through the duct, and mouthing in the very apex of the duct. A further modification may include two or more rows of nozzles, relatively displaced in a zigzag arrangement of the nozzles.
Yet another modification will be explained with reference to fig. 2. In a second plane, transversely to the first plane, the duct 12 has a height h that successively decreases from the inlet end towards the outlet end. Basically, the reduction of the height h is reciprocally proportional to the increasing duct width w in order substantially to maintain the same sectional area from the inlet end to the outlet end of the duct 12. Specifically, the sectional area at the mouth of the inlet may be maintained throughout the duct, all way to the nozzles.
The applicator 10 demonstrates a first solution to the problem of obtaining uniform fluid flow conditions over the width of the applicator. A further development of the applicator will now be explained with reference to figs. 3 and 4.
Like the first applicator, the applicator 20 comprises a housing 21, enclosing a duct 22 directing a fluid flow from an inlet 23 at an inlet end 24 of the housing, to at least one row of discharge nozzles 25 arranged at an outlet end 26 of the housing 21. The housing 21 has a front face 27 and a back face 28, spaced in superposed relation by means of an interconnecting frame element 29. The inlet 23 is connectable to a fluid supply, and the nozzles 25 are equally spaced on a rectilinear row and designed to discharge the fluid in the form of parallel fluid strands.
As best seen in fig. 3 the applicator 20 basically has a triangular outline, the inlet 23 being arranged in the apex and the row of nozzles 25 being arranged on the base line of the triangle. The duct width w diverges continuously from the inlet end towards the outlet end, to encompass the length of the row of nozzles 25.
However, the applicator 20 differs from the first applicator 10 in that the base line is curved, and hence the nominal differences in length from the inlet to the nozzles is further reduced. Preferably, the nozzles 25 are arranged on an arc of a circle. Most preferred, a centre C of the circle is located at the inlet 23, whereby all nozzles are equally spaced on the same radial distance from the inlet. The geometry of applicator 20, wherein the flow paths from the inlet to each nozzle are of equal length, promotes an essentially laminar flow of fluid from the inlet 23 to the nozzles 25.
As best seen in fig. 4, the applicator 20 is designed to deflect the incoming fluid F transversely through the duct, from where the fluid is discharged in the flow direction through the duct. The applicator of figs. 3 and 4 is thus designed for a vertical orientation in a production line, discharging the fluid F vertically to a substrate (not shown) that is advanced below the applicator.
Naturally, the curved base line of applicator 20 may be implemented in an applicator for horizontal orientation in a production line, by arranging the nozzles for a deflected discharge flow as shown in fig. 5. Likewise, the nozzles of applicator 10 may be arranged for a vertical orientation of the applicator, by directing the nozzles to discharge the fluid in the flow direction through the duct 12 as shown in fig. 6.
An advantageous feature of the applicators 10 and 20 is that the distances separating the inlet from each nozzle are equal, or essentially equal. As a result, the amount of fluid exiting from each nozzle by unit time will be essentially equal. In the case of spreading an adhesive system, or adhesive system components, to the surface of a substrate, this provides for a uniform distribution of adhesive to the substrate. In consequence, when the substrate is laminated with other substrates, uniform bonding will be secured.
Advantageously, the volume of the duct may be comparatively small in order to further avoid the generation of air pockets and stagnation within the duct. Specifically, the inlet end of the duct may connect closely to the mouth of the fluid inlet, and the duct width is closely dimensioned to encompass the outmost nozzles, thus eliminating any dead volumes in the duct.
A small duct volume facilitates cleaning of the applicator, and reduces the wastage of fluid upon cleaning. With reference to figs. 7 and 8, further measures will be explained in order to reduce the duct volume and wastage of fluid. The suggested measures are considered also to promote a uniform distribution of fluid to the nozzles by extending the flow paths and thus the dwell time of fluid in the duct.
In the applicator shown in fig. 7 the duct is formed as a labyrinth 30 having prismatic formations 31 for separating the flow F, the formations reaching fully over the section height of the duct and connecting the front and back faces of the applicator housing. Other polygonal or rounded sections of the labyrinth structures may by considered, as well as formations of uniform or increasing/decreasing sectional length and width, as seen in the direction of flow. The labyrinth 30 splits the flow into a number of divisional flows and extends the flow path length, thus further decreasing the nominal differences in length between the inlet and the nozzles in the embodiment of applicator 10.
The applicator of fig. 8 has a labyrinth 40 formed by a multiplicity of spherical elements 41 loosely received in the duct and substantially filling the duct section from the outlet end to the inlet. The spherical elements 41 may be realized as glass pellets, or pellets formed of other low friction material or coated to provide a non-sticky exterior. The diameter of the spherical elements 41 preferably is chosen to exceed half the height h of the duct. A perforated bottom shield 42 or similar structure, straight or arcuate, may be installed to secure that the fluid has free access to the nozzle entries. The operation of the labyrinth 40 is substantially the same as that of the labyrinth 30, but the labyrinth 40 may further reduce the differences in flow path length from the inlet to the nozzles. Both labyrinths 30,40 result in a substantial reduction of fluid waste in the cleaning operation. In this connection it should be pointed out, that the spherical elements need not be removed in the cleaning operation. Advantageously, the applicator is flushed with pressurized water, optionally in combination with pressurized air, for swift and easy cleaning of the duct and the spherical elements.
The adhesive system according to the present invention suitably comprises a resin component and a hardener component. The adhesive system may also comprise hardener, filler, thickener or other component.
The resin and hardener components of the adhesive system may be separately applied through individual applicators arranged in succession in the production line. Alternatively, the resin and hardener may be pre-mixed before application through the applicator.
The present method is particularly suited for applying adhesive systems, or components of adhesive systems, chosen from the group comprising urea-formaldehyde (UF) resin gluing systems, melamine-formaldehyde (MF) resin gluing systems, melamine-urea-formaldehyde (MUF) resin gluing systems, phenol-formaldehyde (PF) resin gluing systems, phenol-resorcinol-formaldehyde (PRF) resin gluing systems, polyurethane (PUR) resin gluing systems, polyvinyl acetate gluing systems, emulsion polymer isocyanate (EPI) resin gluing systems, and various combinations of two or more of these gluing systems. Most preferably, the adhesive system is chosen from melamine-formaldehyde (MF) resin gluing systems, melamine-urea-formaldehyde (MUF) resin gluing systems, phenol-resorcinol-formaldehyde (PRF) resin gluing systems, polyurethane (PUR) resin gluing systems, and emulsion polymer isocyanate (EPI) resin gluing systems.
Regardless of which adhesive system is used the present invention provides an improved method for application of the adhesive system, aiming for a uniform distribution of adhesive to the laminate components.
The suggested method for applying a fluid adhesive system or fluid components of an adhesive system, such as resin and hardener, illustrated in fig. 9, comprises the modulation of a sectional profile of a fluid flow to be distributed to a substrate. From a supply flow having a concentrated sectional profile S, mostly of circular section, the fluid flow is converted into an extended and narrow sectional profile E of a discharge flow feeding at least one row of distributing nozzles at a discharge end. The converted sectional profile has a width w in a first plane transversely to a flow direction F towards the nozzles, the width successively increasing from a supply end to encompass the operational distribution width W of the nozzles at the discharge end. Preferably, the width w of the converted fluid section at discharge end is less than twice the length 1 of the shortest distance from the supply end to the discharge end.
The converted sectional profile has a height h in a second plane, transversely to said first plane. Advantageously, the height is successively decreasing towards the discharge end of the flow. Preferably, the decreasing height of the sectional profile is reciprocally proportional to the increasing width thereof towards the discharge end, in order substantially to maintain the same sectional area from the supply end to the discharge end. Specifically, the sectional area of the concentrated supply flow may be maintained all way to discharge end. The modulation may include one or more deflections of the flow direction before discharge.
The modulation of the fluid flow section as stated above results in a uniform fluid feed to each applicator opening, or nozzle, arranged in at least one row at the discharge end. In other words, each nozzle entry is provided a direct communication with the concentrated supply feed, without its flow path crossing or mixing with the flow path of another nozzle in the row of nozzles.
The method is equally applicable for separate application of adhesive system components, such as resin and hardener, by distribution through individual applicators, and for application of an adhesive system where the components of the adhesive system have been pre-mixed, through a singular applicator.
In order to reduce the spatial requirement in a production line setup, multiple applicators 10,20 may be arranged in an assembly and laterally and/or axially displaced relative to the feed direction of the substrate, thus extending a total operational spreading width W_(1+n) of the system. Fig. 10 illustrates a horizontal assembly of three applicators 10, and in fig. 11, a vertical assembly of three applicators 20 is illustrated. A uniform feed to each applicator in the assembly may be controlled by flow meters and regulators arranged to control the volume flow rate from a supply of adhesive system or adhesive system components.
The invention has been explained with reference to examples, realizing basic means for implementation of the suggested solution. Evidently, several modifications to the structural layout shown herein may be contemplated while still taking advantage of the invention.

Claims

An applicator (10,20) for spreading a fluid to a substrate, comprising a housing (11,21) with an inlet end (14,24) and an outlet end (16,26), the inlet end having an inlet (13,23) connectable to a fluid supply, and the outlet end having multiple nozzles (15,25) arranged in a row for spreading the fluid in parallel fluid strands, the applicator further comprising

a continuous duct (12,22) distributing the fluid from the inlet to the nozzles,

the flow duct in a first plane having a length (1) in the flow direction and a width (w) across the direction of flow through the duct, the applicator characterized by:

the width increasing from the inlet end to encompass the row of nozzles at the outlet end, the duct providing each nozzle (15,25) a direct communication with the inlet (13,23).
The applicator of claim 1, characterized in that the length (1) of the duct amounts to at least half the length of the row of nozzles at the outlet end.
The applicator of claim 1, characterized in that the duct in said first plane has the geometry of an isosceles triangle, the inlet being arranged at the apex and the nozzles being arranged on a base line of the triangle.
The applicator of claim 1, characterized in that the row of nozzles in said first plane are arranged on an arc of a circle.
The applicator of claim 4, characterized in that a centre (C)of said circle is located at the inlet (23).
The applicator of claim 1, characterized in that the fluid flow through the duct (12,22) is split into divisional flow paths by means of a labyrinth (30,40), arranged in the duct.
The applicator of claim 6, characterized in that the labyrinth (30) is realized as rounded or prismatic formations (31), reaching fully over the sectional height (h) of the duct.
The applicator of claim 6, characterized in that the labyrinth (40) is realized as spherical elements (41), loosely received in the duct.
The applicator of any previous claim, characterized in that the duct in a second plane transversely to said first plane has a reducing height towards the outlet end, the reduction being reciprocally proportional to the increasing duct width.
The applicator of claim 9, characterized in that a sectional area at the mouth of the inlet is maintained throughout the duct.
The applicator of any previous claim, characterized in that the duct width is progressively increasing towards the outlet end.
The use of an applicator according to any previous claim 1-11 for separate distribution of resin and hardener of an adhesive system in the production of laminate structures.
The use of an applicator according to any previous claim 1-11 for distribution of an adhesive system wherein resin and hardener are mixed in the production of laminate structures.
The use according to any previous claim 12-13, wherein the adhesive system belongs to the group of melamine-formaldehyde (MF) resin adhesive systems, melamine-urea-formaldehyde (MUF) resin adhesive systems, phenol-resorcinol-formaldehyde (PRF) resin adhesive systems, polyurethane (PUR) resin adhesive systems, and emulsion polymer isocyanate (EPI) resin adhesive systems.
A method for applying a fluid adhesive system or fluid components of an adhesive system to a substrate, comprising the step of feeding a row of distributing nozzles with a modulated fluid flow by converting a concentrated sectional profile (S) of a supply flow into an extended and narrow sectional profile (E) of'a discharge flow, the modulated section having a width (w) in a first plane transversely to a flow direction (F) towards the nozzles, the width successively increasing to encompass an operational distribution width (W) of the nozzles.
The method of claim 15, characterized in that the fluid flow section is modulated to have a width (w) at discharge that is less than twice the length (1) of the shortest distance from supply to discharge.
The method of claim 15 or 16, characterized in that the fluid flow section is modulated to have a successively decreasing height (h) in a second plane, transversely to the first plane, the decreasing height (h) being reciprocally proportional to the increasing width (w) of the sectional profile.
The method of claim 17, characterized in that the fluid flow section is modulated to maintain a sectional area from supply to discharge.
The method of any previous claim 15-18, characterized in that an extended operational distribution width (W_(1+n)) is accomplished by arranging multiple applicators in an assembly, laterally and/or axially displaced relative to a feed direction of the substrate.
The method of any previous claim 15-19, wherein the adhesive system belongs to the group of melamine-formaldehyde (MF) resin adhesive systems, melamine-urea-formaldehyde (MUF) resin adhesive systems, phenol-resorcinol-formaldehyde (PRF) resin adhesive systems, polyurethane (PUR) resin adhesive systems, and emulsion polymer isocyanate (EPI) resin adhesive systems.