EP0329829B1 - Device for applying glue or a similar product to a surface - Google Patents

Description

The invention relates to a device of the type corresponding to the preamble of claim 1.

The starting point of the invention has been problems which occurred during the production of hygiene articles. This should be understood to mean articles such as diaper pants for babies, diaper pads, sanitary napkins, medical pads, surgical pads and the like, which are used to collect liquid separated from the body and on one side a liquid-impermeable, very flexible film of low thickness, for example made of polypropylene of 12 to 15 My ( Micrometers) to which a flat suction pad made of cellulose or a suitable plastic material is glued, which in turn is covered by a fleece.

The absorbent pad consists of a loose material in the manner of a short-fiber cotton, which must be fixed on the film so that it stays in place and does not slip when handling the article. For this reason, the suction pad is glued to the film.

The difficulty with this bonding stems from the fact that the film to which the glue has to be applied is very sensitive both mechanically and thermally. For this reason, it has already been attempted to use cold glue. Cold glue is, however, an aqueous dispersion and there is therefore a risk that problems with possible moisture trapping will occur with absolutely tight final packaging. The alternative is the use of hot-melt adhesive, in which, however, the uniform distribution of a small application quantity over the application width, which is generally in the range from 200 to 800 mm, is difficult. If, as is assumed in the preamble, an order is made with a uniform application nozzle that is continuous across the application width, considerable effort must be expended to allow the glue to emerge evenly from the slot nozzle in the small amount. A reasonably uniform distribution requires, in particular, a low viscosity of the hot-melt adhesive, which was therefore applied at temperatures of 110 to 140 ^° C. However, the uniformity was unsatisfactory. The high temperature of the hot glue applied and the application quantity of 2 to 4 g / m², which could not be undercut so far, caused the film to deform strongly and the back of the hygiene article produced to have an irregularly wavy relief.

The process is also practiced of applying individual narrow glue traces placed next to one another on the film at intervals. However, these traces of glue are also clearly evident on the back of the film and are also disadvantageous in that form channels between the glue traces, in which the suction pad is not connected to the film and, as experience has shown, can escape through the liquid.

The preamble of claim 1 is based on EP-B1 96 453, in which an application device is disclosed in which slit nozzles which extend closely above the web transversely to the direction of advance thereof lie opposite one another in pairs in the direction of advance and are separated from one another by a separating plate. The two slot nozzles in a pair create a double-layer application and are each supplied by a common pump. Several such arrangements can be provided next to one another in the transverse direction of the web, each of which then has its own separately driven pump, so that differences in the delivery quantities across the web cannot be ruled out.

On the basis of the described problem, the object of the invention is to design a generic device such that very small application quantities per unit area can be applied in a uniformly uniform manner to a leading substrate over its width.

This object is achieved by the invention reproduced in claim 1.

So it is no longer working with a slot nozzle which is continuous over the application width and in which it is very difficult to obtain uniform discharge quantities over the entire length, but instead a number of narrower slot nozzles are placed side by side, so that the width of the individual slot nozzle is correspondingly smaller becomes. With an application width of approximately 240 mm, for example, eight individual slot nozzles, each 30 mm wide, can be present. Within such a narrow single slot nozzle, the uniform distribution across the width is not yet a major problem. The main point is that these individual slot nozzles each have their own glue pump and not via a distributor head of one common glue pump can be supplied. This measure ensures that the same amount of glue is always allocated to each individual slot nozzle and the distribution over the entire width of the application is correspondingly uniform. If a slot nozzle should be preferred hydrodynamically because, for example, due to manufacturing tolerances, it has a slightly larger slot width, or because the flow resistance of the channels to the slot nozzle is somewhat lower, this slot nozzle will only provide exactly the pump that is assigned to it exit the assigned order quantity. If such a hydrodynamically preferred area is present in the case of a slot nozzle that extends over the entire width of the application, the application quantity preferably emerges at this point and the pressure drops sharply towards the sides, so that different application quantities per unit area cannot be avoided.

In order to avoid pressure surges in the glue streams when opening and closing the respective application valve, which lead to impurities in the respective glue track at the beginning or end, a return valve is assigned to the application valve, which e.g. when the application valve closes, the glue stream returns to the supply, so that the glue stream is always exposed to a uniform flow pressure and the glue application is not only very uniform in the transverse direction, but also precisely limited at the ends. The basic idea of the paired order and return valves is known per se from DE-PS 32 00 469.

An application device with several adjacent units is known per se from DE-PS 30 07 031. However, these are not slotted nozzles from which the application medium emerges under pressure, but rather inclined run-off surfaces over which a liquid application medium runs down onto a web in order to produce a strip-by-layer application there. This device is not suitable for higher-viscosity application agents such as glue.

The separate glue streams assigned to the individual slot nozzles are supplied in the invention by a multiple gear pump, in which, for example, against a common central wheel, a corresponding number of planets arranged counter gears works that produce cleanly separated flow rates.

With regard to the hygiene articles mentioned, in which the glue has to be applied to a sensitive film, there are two important advantages. The tests have shown that the application quantity can be reduced to an amount of 0.2 g / m². Quite apart from the saving of glue, this has the effect that the heat capacity of the applied glue is very low and the thermal load on the substrate, ie the film, remains low. Another factor works in the same direction, namely that in order to even out the application, it is no longer necessary to ensure that the glue has as low a viscosity as possible with a continuous slot nozzle. The application is also even when applied with a slightly higher viscosity. This means that the temperature of the glue can be reduced to around 65 ^° C. without loss of uniformity, which also reduces the stress on the film.

The gluing of the film for the hygiene articles mentioned is the starting point and preferred example of application of the invention, but it is understood that the device can also be used for substrates other than the films mentioned, in particular for the uniform application of very small amounts of glue. Likewise, the glue is only the preferred application of the invention and other liquid to highly viscous application agents are by no means excluded.

The adjacent individual slot nozzles can be formed in the manner shown in claim 2.

The two “surfaces” are formed, for example, by an end face of a nozzle plate provided on the device, in which the feed channels open, and a clamping strip extending in front of it, which clamp the slotted plate between them. The feed channels open into the areas of the slotted plate that remain free between the webs, so that the glue passes through the back of the slotted plate and the webs are channeled and a union of the individual glue streams only takes place directly in front of the exit point, so that on the one hand there is a uniform coverage of the application width, and a transfer of glue from a slot nozzle into the neighboring one is practically prevented.

In practice, the nozzle plate is an integral part of the device, as a result of which a distribution of the outlet openings of the feed channels in the end face of the nozzle plate is predetermined at certain distances in the direction of the application width. Now it may happen that the order width has to be changed. To accomplish this task, the intermediate plate according to claim 3 is used, with the aid of which the exit points of the feed channels opening into the individual slot nozzles can be pulled apart or pushed together. In such a case, the slotted plate and the intermediate plate are replaced, and it is therefore possible to work with eight slit nozzles, for example 35 mm wide, instead of eight slit nozzles a 30 mm wide, without any assembly work other than unscrewing the terminal strip and replacing the Slotted sheet and the intermediate plate are required.

The spreading of the outlet mouths of the feed channels can be brought about in the manner set out in claim 4.

• Fig. 1 zeigt eine Seitenansicht der Vorrichtung;
• Fig. 2 zeigt eine Ansicht gemäß Fig. 1 von links;
• Fig. 3 zeigt eine vergrößerte Ansicht des linken unteren Teils von Fig. 1, teilweise im Schnitt;
• Fig. 4 zeigt den unteren Teil von Fig. 3 mit Zwischenplatte;
• Fig. 5 zeigt eine Ansicht des Schlitzbleches;
• Fig. 6 zeigt eine vergrößerter Wiedergabe des in Fig. 5 mit VI bezeichneten, mit einen strichpunktierten Kreis umgebenen Bereichs;
• Fig. 7 zeigt eine Ansicht der Zwischenplatte, gemäß Fig. 4 von links;
• Fig. 8 ist ein Schnitt nach der Linie VIII-VIII in Fig. 7 in vergrößertem Maßstab;
• Fig. 9 ist eine Ansicht der Zwischenplatte von oben;
• Fig. 10 ist eine Ansicht der Rückseite der Zwischenplatte nach Fig. 7.

In the drawing, an embodiment of the invention is shown.

• Fig. 1 shows a side view of the device;
• FIG. 2 shows a view according to FIG. 1 from the left;
• Fig. 3 shows an enlarged view of the lower left part of Fig. 1, partly in section;
• Fig. 4 shows the lower part of Fig. 3 with intermediate plate;
• Fig. 5 shows a view of the slotted plate;
• FIG. 6 shows an enlarged representation of the region designated by VI in FIG. 5 and surrounded by a chain-dotted circle;
• FIG. 7 shows a view of the intermediate plate from FIG. 4 from the left;
• Fig. 8 is a section along the line VIII-VIII in Fig. 7 on an enlarged scale;
• Fig. 9 is a top view of the intermediate plate;
• 10 is a rear view of the intermediate plate of FIG. 7.

The device 100 shown in FIGS. 1 and 2 is used to provide the film web 1 with a very thin layer of hot-melt adhesive over an application width 2 (FIG. 2) evenly. In the exemplary embodiment, the film web 1 consists of polypropylene of 15 my thickness and is guided past the exit point 3 of the hot-melt adhesive in the manner shown in FIG. 1 with a slight wrap angle and a slight longitudinal tension. The film web 1 is therefore not supported at the exit point 3.

The device 100 comprises an application head, designated as a whole by 4, and this in turn comprises an application block 5 with inner channels, which can be seen in detail in FIG. 3. The application block 5 is held by two side walls 6, which are connected by a cross plate 7, which in turn is fastened in a suitable manner above the film web 1 in the machine frame.

A drive motor 8 is fastened to the cross plate 7 and drives an eightfold gear pump 10 mounted on the order block 5 via an angular gear 9. The eightfold gear pump 10 comprises eight individual gear pumps which generate eight metered glue flows which are independent of one another and which are passed through inner channels into the application block 5. The liquid glue brought up from a melting device, not shown, passes through a filter 11 and enters the application block 5 at the channel 12 and into the eight-way gear pump 10 at the mouth 13, which doses the glue in eight independent flows in eight according to FIG 3 gives vertical channels 14, which are distributed across the width of the web in the order block 5. An order valve 15 is assigned to each channel 14 and is connected to the channel 14 via a transverse channel 17. In addition, each channel 14 is assigned a return valve 16 arranged above the application valve 15, which is connected to the channel 14 via a transverse channel 18. A glue return 20 is also connected to the return valve 16 via a transverse channel 19. The valves 15, 16 have the same design in terms of their hydrodynamic resistance and are pneumatically controlled. The air supply lines are labeled 21 and 22, respectively. The design is such that the valves 15, 16 are always controlled alternately, i.e. when the order valve 15 closes, the return valve 16 opens and allows the glue conveyed in the channel 14 by the pump 10 instead of via the cross channel 17 to the order valve 15 via the cross channel 18 to the return valve 16, which is then opened and the glue in forwards the glue return 20. In this way, a glue flow of constant pressure can be maintained in the channel 14 regardless of the actuation of the application valve 15, in which no pressure surges occur due to the closing of the application valve 15.

As can be seen from FIG. 2, eight valve pairs 15, 16 are provided next to one another in accordance with the number of channels 14.

According to FIG. 3, a nozzle plate 23 is screwed under the application block 5 and the application valve 15, which has a vertical or essentially end face 24 which extends substantially perpendicular to the substrate and into which eight glue channels 25, which start from the respective outlet mouth of the application valves 15, open . A slotted plate 30 is arranged in front of the end face 24, the shape of which can be seen in FIG. 5 and which is screwed against the end face 24 by a clamping strip 26 with a flat rear face 27.

The end face 24 and the rear face 27 have lower edges 28 and 29, respectively, which are at the same height.

The slotted plate 30 is made of brass or corrosion-resistant steel and has a thickness of 0.3 mm. It covers the end face 24. On the underside, a rectangular cut-out 31 is formed, which extends over the application width 2 (FIG. 2) and which in the exemplary embodiment has seven webs 32 protruding into the cut-out 31 in equal intervals, in the embodiment 31 Chambers 33 is divided. The webs 32 are about 1 mm wide and tapered at the front. The tip lies at a short distance 34 (FIG. 6), for example 1 mm, above the lower edge 28 of the end face 24 when the slotted plate 30 is mounted in the manner shown in FIG. 3.

The chambers 33 are closed on three sides, but open at the bottom and, together with the surfaces 24 and 27, form downwardly opening, separate slot nozzles 35 (FIG. 2).

As can be seen from Fig. 2, the valves 15, 16 are arranged close to each other. Their width is essentially fixed, so that a certain transverse distance between the glue channels 25 cannot be undershot. If the Order width 2 is dimensioned so that the division of the glue channels 25 coincides with the division of the slot nozzles 35, the glue channels 25 can open directly into the slot nozzles 35 formed, as shown in Fig. 3.

If, however, the division of the slot nozzles 35 does not match the division of the channels 25 and the slot nozzles are narrower than the distances between the application valves 15 (see FIG. 2), an adaptation by an intermediate plate 40 is required, which in the installed state in FIG. 4 and in different views in FIGS. 7 to 10.

The intermediate plate 40 has the same outline as the end face 24 or the slotted plate 30. On the front side shown in FIG. 7, in the longitudinal direction of the intermediate plate 40, there are extending but separate spreading grooves 36, the length of the width of the chambers 33 of the slotted plate 30 correspond. In the assembled state according to FIG. 4, the webs 32 each extend at the locations of the interruptions between successive spreading grooves 36. The middle six spreading grooves 36 have through bores 37 in the middle which pass through to the rear side of the intermediate plate 40 shown in FIG. 10 . From the mouths of the through bores 37 on the back, angled channels 38, formed as grooves, lead to the points 39, which lie opposite the mouths of the glue channels 25 in the end face 24 of the nozzle plate 23. The locations 39 have the distance from one another corresponding to the glue channels 25, the through bores 37 have the distance given by the slot nozzles 35. In the case of the through bores 37 'leading to the two outer spreading grooves 36', the associated channel 38 'is arranged on the front side of the intermediate plate 40 shown in FIG. 7 for spatial reasons. The openings of the through bores 37 in the spreading grooves 36 are denoted by 41 in FIG. 9.

By interposing the intermediate plate 40 according to FIG. 4, it is therefore possible to change from the division of the application valves 15 or glue channels 25 specified for a specific device 100 to another division, for example to a narrower division with a smaller application width 2, as in FIG Fig. 2 shown, but also to a further division, if necessary.

To change the width of the application, all that is required is to unscrew the terminal block 26 ′ and to replace the intermediate plate 40 and the slotted plate 30.

Claims (4)

1. Apparatus for the surface application of glue or the like to a moving substrate, in particular to the thermally sensitive moisture barrier layer of hygienic products,
      with a reservoir for the glue,
      with an applicator head having a slit nozzle arrangement provided transverse to the direction of travel of the substrate for applying the adhesive to the substrate, the slit nozzle arrangement including a number of individual slit nozzles (35) arranged side by side, of which the outlet slots (33) are directly adjacent to one another at the outlet points (3) and in which the streams of adhesive, looked at in the direction of flow of the adhesive, are separated from one another until shortly ahead of the points (3) of emergence and are controlled by respective independent applicator valves (15),
      and with a pump arrangement for delivering the adhesive from the reservoir to the applicator head (4),
      characterised in that
      the slit nozzles (35) have a minimum width of about 30 to 35 mm, within which the uniform distribution of the adhesive is still achieved,
      that the pump arrangement is provided by a multiple gear pump (10) of which the individual gear pumps deliver to the associated slit nozzles (35) mutually independent metered streams of adhesive containing equal quantities,
      and that for maintaining a constant pressure of the flow of adhesive each applicator valve (15) has associated with it a separate non-return valve (16) of equal hydro dynamic resistance actuated alternately with it.
2. Apparatus according to claim 1,
      characterised in that
      the slit nozzles (35) are formed by a slit metal sheet (30) clamped between two flat surfaces (24, 27),
      that adhesive supply passages (25) fed from the multiple gear pump (10) open into one of the faces (27),
      that the lower edges (28, 29) set at the same height, of the faces (24, 27) define the outlet points (3)
      and that the slit metal sheet (30) has, between the outlet slots (33) corresponding to the individual slit nozzles (35), toothcomb-like projecting small webs (32) which terminate shortly ahead of the outlet points (3), looked at in the direction of flow of the adhesive.
3. Apparatus according to claim 1,
      characterised in that,
      the adhesive passages (25) open into a surface (24) of the applicator head (4) which is perpendicular to the direction of travel of the substrate (1) and there is provided an intermediate plate (40) engaging the one face (24) and having its other side engaging a slit metal sheet (30) which has toothcomb-like projecting small webs (32) between the outlet slots (33) corresponding to the individual slit nozzles (35),
      and that the intermediate plate (40) has through passages of which the outlets (41) lead into the individual slit nozzles (35) formed by the slit metal sheet (30) and have a different mutual spacing from the entries (39) placed on the other side.
4. Apparatus according to claim 3, characterised in that the through passages have bores (37,37') extending perpendicular to the intermediate plate (40) and the formation of the different spacings is achieved by transverse grooves (38,38') extending in the transverse direction and provided on at least one side of the intermediate plate (40).

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