DE29903734U1 - Pressure element and system of pressure elements for coating straight narrow surfaces of a plate element - Google Patents

Description

Doms Adhesive Technology GmbH & Co. KG

Dr. Mathes/SH

26.02.1999

Utility model application
H3946a

Pressure element and system of pressure elements for coating straight narrow surfaces of a panel element

The invention relates to the gluing of a band-shaped covering to a narrow surface (edge) of a panel element, in particular a chipboard, fiberboard or solid wood panel, whereby the covering is pressed onto the narrow surface using at least one pressure element. For gluing, the covering is usually coated with a hot melt adhesive. Within the scope of the invention, however, it is also fundamentally possible for the adhesive to first be applied to the narrow surface, which is called the "edge" in technical terms, and for the covering to then be pressed onto the narrow surface. It is known that the pressure elements can be designed as a pressure roller or sliding shoe. The panel elements used are usually coated on their top and/or bottom, but such a coating is not necessary for using the sliding shoe according to the invention.

State of the art

Such gluing or coating of straight and profiled narrow surfaces of panel elements, especially wood materials, with coating materials is usually carried out using so-called edge banding machines, over which the panel elements run at high speed. The coating materials can be made of plastic (melamine, PVC, ABS, PP) or be paper-based. In addition to melamine and polyester, veneers can also be processed as edge material. The coating material, on one side of which a hot melt adhesive is applied, is pressed firmly onto the narrow surfaces using suitable pressure devices. Protruding edges are then cut off or milled off with a draw knife.

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The straight surfaces are usually coated using pressure rollers, whose diameter can be up to 200 mm, with the aid of hot melt adhesive and edge banding. The roller pressure is used to fix the coating to the workpiece as it passes by. The process can be carried out using one or more rollers arranged one behind the other. The rolling creates an uneven surface. In addition, the flat pressure does not produce a very tight joint. The factors of waviness and poor joint tightness are particularly disruptive with light, single-colored decors or glossy surfaces.

A method for coating the narrow surfaces of panel elements is known from DE 196 30 273 A1 (Dr. Rudolf Schieber Chemische Fabrik GmbH & Co KG). Here, the pressure surface of the pressure element designed as a sliding shoe is curved outwards when viewed in the longitudinal direction. In this way, the waviness of the glued-on covering in the longitudinal direction of the narrow surface is greatly reduced in a simple and inexpensive way.

Methods for coating narrow surfaces of a panel element using glide shoes have also been known since 1988 from DD 287 606 A7, DE 37 40 964 A1 and DE 43 15 792 A1. An advantage of using slide shoes in contrast to pressure rollers, as known for example from DE 93 06 484 U1, is the significantly lower waviness of the coated narrow surfaces.

Further problems that occur during the production of coated panel elements are described below. For the sake of clarity, the boundary area between the narrow surfaces and the main surfaces (wide surfaces) of the panel elements is referred to as the "boundary edge", as the term "edge" is already used in technical language for the entire narrow surface of panel elements.

With the sliding shoes known from DE 43 15 792 A1, DD 287 606 A7 and DE 196 30 273 A1, a contact pressure is exerted on the entire narrow surface, whereby the contact pressure is constant across the entire width of the narrow surface. Due to the flat pressing, a relatively large force is required on the sliding shoe in order to achieve the necessary contact pressure at every point on the narrow surface.

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A further disadvantage in the state of the art is when, as is usual, several pressure elements arranged one behind the other are provided for pressing the band-shaped covering onto the narrow surface. The hot melt adhesive applied to the back of the band-shaped covering, which cools down when it comes into contact with the raw narrow surface and becomes correspondingly more viscous, cools down so much on the relatively long path from the first to the last pressure element that perfect pressing and adhesion of the covering by the last pressure element is not guaranteed in every case.

The invention therefore relates to a pressure element for an edge banding machine for gluing a strip-shaped covering with an adhesive to a narrow surface (edge) of a panel element with a straight cross-section , in particular a chipboard, fiberboard or solid wood panel. Such a pressure element is known, for example, from DE 196 30 273 A1.

Task and solution regarding the sliding shoe according to the invention

Compared to the state of the art, in particular compared to DE 196 30 273 A1, the invention is based on the task of developing a sliding shoe of the type mentioned with which the surface of the coated narrow surface can be further improved, whereby in particular transverse waves are to be avoided and a particularly tight adhesive joint between the strip-shaped covering and the plate element is to be achieved. The term "transverse waves" refers to waves in the strip-shaped covering whose crests run transversely to the longitudinal direction of the narrow surface. The joint tightness should be so high that the adhesive joint running between the strip-shaped covering and the narrow surface at its boundary edge is no longer or hardly visible to the naked eye after the excess has been cut off. These requirements should be met in the most economical way possible, whereby only minor changes to known edge banding machines should be necessary. In addition, the speed of coating the narrow surfaces should be able to be increased further without having to accept any loss of quality.

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This object is achieved in a pressure element according to the preamble of claim 1 in that the pressure element is designed as a sliding shoe and, in particular over its entire length, has a linear pressure area.

In this application, the "pressure surface" is to be understood as the part of the pressure element that is opposite the narrow surface during operation. The term "pressure area" here is understood as the part of the pressure surface that is directly in contact with the covering during operation, i.e. that touches it. According to the invention and in contrast to the prior art, this pressure area is generally not identical to the "pressure surface", but only represents a part of this pressure surface.

When reference is made to a direction, it is the direction of movement of the narrow surface along the sliding shoes.

Since the covering is pressed onto the narrow surface with the sliding shoe according to the invention on an almost linear contact surface, a high contact pressure can be achieved with only moderate force on the sliding shoe and thus a high joint tightness (particularly narrow adhesive joint). The high contact pressure also ensures particularly good anchoring of the band-shaped covering to the narrow surface, since the hot melt adhesive is pressed into the open-pored chipboard or MDF board.

The waves that occur in the prior art and run transversely to the narrow surface can be almost completely avoided with the sliding shoe according to the invention if its linear pressure area is arranged at an angle to the longitudinal direction of the narrow surface. In this case, the linear pressure area pushes any waves that may be present in front of it before the hot melt adhesive has become too cold and therefore too viscous.

According to the invention, it is not necessary for the linear pressure area to run in the longitudinal direction of the sliding shoe. When using the sliding shoe according to the invention, only the alignment of the linear pressure area to the narrow surface is important, but not the alignment of the entire sliding shoe to the narrow surface. If the linear pressure area runs in the longitudinal direction

H3946a - 5 -

direction of the sliding shoe, the entire sliding shoe is set at an angle to the narrow surface. On the other hand, if the linear pressure area already has the desired angle to the longitudinal direction of the sliding shoe, it can be aligned parallel to the narrow surface of the plate element.

The linear pressure surface can be designed in different ways. In an advantageous embodiment of the invention, it is proposed that the surface of the sliding shoe facing the coating, i.e. the "pressure surface", tapers to a point in cross-section, with the pointed edge forming the "pressure area".

Alternatively, the tip can be rounded. In this case, it is preferred if the radius of curvature of the tip is between 0.5 and 5.0 mm.

In yet another embodiment, it is proposed that the tip is flattened, with the flattened pressure area having a width of at most 5 mm, in particular of at most 3 mm.

In all these cases, in contrast to the state of the art and despite rounding or flattening, there is still an essentially linear pressure area, which leads to the above-mentioned advantages of the lack of waviness and the high joint tightness.

When using the sliding shoe according to the invention, the linear pressure area preferably covers the entire width of the narrow surface. In order to achieve not only a high contact pressure but also an increased contact duration, it can be advantageous if the linear pressure area is set at a particularly small angle to the narrow surface. The linear pressure area and thus also the sliding shoe must then be correspondingly long. It has proven advantageous if the sliding shoe has a length of up to 500 mm and in particular from 30 to 300 mm.

It is also proposed that the linear pressure area runs in a straight line. However, it is also possible and within the scope of the invention for this pressure area to run in a curved line. In this way, a different effect of the sliding shoe can be achieved across the width of the narrow surface, if this is desired.

· I

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Finally, the linear pressure area can run parallel or diagonally to the longitudinal axis of the sliding shoe and, in particular, diagonally to it. The only important thing is that when the sliding shoe is used, the linear pressure area forms an angle with the longitudinal direction of the narrow surface, i.e. does not run parallel to the longitudinal direction of the narrow surface.

The invention also relates to a system of pressure elements for an edge banding machine for pressing a band-shaped covering coated with adhesive onto a narrow surface (edge) of a panel element with a straight cross-section, in particular a chipboard, fiberboard or solid wood panel.

With this system of pressure elements, the entire process for gluing the strip-shaped covering can be carried out, whereby the above-mentioned inventive object is achieved. For this purpose, it is proposed that the pressure element to be used first is designed as a pressure roller known per se, the pressure element to be used after that is designed as the above-mentioned inventive sliding shoe and the pressure element to be used after that is designed as a further sliding shoe which, when pressed, only acts on one or both border areas between the narrow surface and the wide surfaces of the plate element, in particular without the covering being bent in the border areas. In this way, a particularly high contact pressure of the covering in the area of the border edges and thus an extremely narrow adhesive gap in this area is achieved.

This additional sliding shoe can be designed in different ways. It is proposed that the additional sliding shoe has a concave pressure surface, which essentially consists of two flat surfaces, in particular at an angle of 45 to 60° to one another.

To avoid contamination of the contact surface and the edge material, it is also preferred if the inlet zone of this additional sliding shoe is rounded in the longitudinal direction. For the same purpose, it is also suggested that the inlet zone of the sliding shoe is rounded in the transverse direction.

H3946a - 7 -

Strip-shaped coverings, plate elements and adhesives to be processed with the sliding shoe according to the invention

Preferably, the strip-shaped coating used in one of the process variants according to the invention has a thickness of 0.15 to 0.2 mm.

The method according to the invention can also be used particularly well if the plate element has a thickness of 15 to 32 mm.

The sliding shoe according to the invention can be used to process all common panel elements. Possible panel elements include chipboard, but also other panels such as blockboard, plywood, so-called MDF panels (medium-density fiberboard) and solid wood panels.

The choice of coverings (edge materials) to be used is also not critical. Edge materials made of melamine, polyester, PVC, ABS, polypropylene and veneers are suitable. The relatively thin edge materials made of decorative paper, which are based on paper and impregnated with colored plastics and are increasingly used today, can also be processed without any problems.

The choice of adhesive to be used in the process according to the invention is also not critical. Hot melt adhesives are preferably used.

For example, hot melt adhesives made from polymers and copolymers of synthetic resins, rubbers, polyethylene, polypropylene, polyurethane, acrylic, vinyl acetate, ethylene vinyl acetate and polyvinyl alcohol can be used.

Specific examples include hot melt adhesives made from the following components:

1) Elastic polymers such as block copolymers, e.g. styrene-butadiene, styrene-butadiene-styrene, styrene-isoprene-styrene, styrene-ethylene-butylene-styrene, styrene-ethylene-propylene-styrene;

2) Ethylene-vinyl acetate polymers, other ethylene esters and copolymers, e.g. ethylene methacrylate, ethylene n-butyl acrylate and ethylene acrylic acid;

H3946a - 8 -

3) Polyolefins such as polyethylene and polypropylene;

4) Polyvinyl acetate and copolymers thereof;

5) Polyacrylates;

6) Polyamides;

7) Polyesters;

8) Polyvinyl alcohols and copolymers thereof;

9) Polyurethanes;

10) Polystyrenes;

11) Polyepoxides;

12) Copolymers of vinyl monomers and polyalkylene oxide polymers;

13) Aldehydes containing resins such as phenol aldehyde, urea aldehyde, melamine aldehyde and the like.

It may also contain components to enhance adhesion, diluents, stabilizers, antioxidants, colorants and fillers.

Examples of components to improve adhesion include:

1) Natural and modified resins,

2) Polyterpene resins,

3) phenolically modified hydrocarbon resins,

4) aliphatic and aromatic hydrocarbon resins,

5) Phthalate esters and

6) hydrogenated hydrocarbons, hydrogenated resins and hydrogenated resin esters.

Examples of diluents include liquid polybutene or polypropylene, petroleum waxes such as paraffin and microcrystalline waxes, semi-liquid polyethylene, hydrogenated animal, fish and vegetable fats, mineral oil and synthetic waxes as well as hydrocarbon oils.

Examples of the other additives can be found in the literature.

In the following, several embodiments of the invention are explained in more detail using drawings. They show

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Figure 1 shows a sliding shoe according to the invention in perspective view,

Figure 2 is a schematic representation of the use of the sliding shoe

according to Figure 1,

Figures 3a, b each show a section through a sliding shoe according to the invention in different designs,

Figure 4 shows the top view of another sliding shoe according to the

Invention,

Figure 5 is a front view of the inlet side of the sliding shoe according to Figure

4,

Figure 6 is a front view of the sliding shoe according to Figure 4 at the outlet

Figure 7 is a schematic representation of the coating process

according to the state of the art and according to a first step of the method according to the invention,

Figure 8 is a perspective view of the further sliding shoe in the

inventive system of pressure elements,

Figure 9 the implementation of the process step with the sliding shoe

according to Figure 8 in schematic representation and

Figure 10 is a side view of the sliding shoe according to Figures 8 and 9.

In all drawings, the same reference symbols have the same meaning and are therefore only explained once if necessary.

In the state of the art, the straight narrow surfaces of the plate elements are coated with the help of pressure rollers, which can have a diameter of up to 200 mm, as shown in Figure 7. The pressure roller 1 with its rotating

H3946a -10-

Axis 5 presses the band-shaped covering 4, which is coated with the hot melt adhesive 6, onto the narrow surface 3 of the plate element 2. The rolling of the pressure roller 1 on the covering 4 creates the above-mentioned waves on the surface of the finished coated narrow surface 3.

It is also known that several pressure rollers connected in series are used.

According to the invention, however, a sliding shoe 7 is used which has a linear pressure area 12 (Figure 1). In the example according to Figure 1, this pressure area 12 runs over the entire length of the sliding shoe 7 and parallel to the longitudinal direction of this sliding shoe.

When using the sliding shoe 7, it is aligned obliquely to the narrow surface 3 of the plate element moving past at high speed, as shown schematically in Figure 2.

The sliding shoe 7 can have a pointed or circularly rounded (Figure 3a) or straight cut (Figure 3b) pressure area 12. The width d of the pressure area 12 should preferably not be greater than 5 mm, so that an almost linear pressure is achieved.

Figure 4 shows an alternatively designed pressure area 12. Here, the pressure area 12 consists of two rounded edges running at an angle to the longitudinal direction of the sliding shoe, whereby the pressure area 12 in this case does not extend over the entire length of the sliding shoe. The running direction of the plate element 3 is indicated by an arrow. This shows that the band-shaped covering is pressed in the middle area of the inlet zone 9 and in the edge area of the outlet zone 10.

Preferably, a system of pressure elements is used when carrying out the method according to the invention. The first pressure element is the pressure roller shown in Figure 7, which is known per se and has already been explained above.

H3946a -11-

The second pressure element is a sliding shoe according to Figures 1 to 6. The third pressure element is another sliding shoe 8 shown in perspective in Figure 8, in which the pressure surface 13 is concave and consists of two flat surfaces running in the longitudinal direction and inclined towards each other. This ensures that the band-shaped covering 4 is pressed strongly in the area of the outer edge of the narrow surface 3 and only there (Figure 9), so that after the protruding edges 11 have been cut off, an invisible or barely visible adhesive joint is the result between the band-shaped covering 4 and the narrow surface 3. It should also be noted that the ground angle between the partial surfaces of the pressure surface 13 is not too small so that the protruding edges 11 are not bent, but can at most be bent around the edge of the narrow surface.

To increase the contact pressure, it is also advantageous if the sliding shoe 8 is ground in the longitudinal direction, as shown in Figure 10. It is preferred if the contact surface 13 has only been worn down by a value a of about 0.3 mm at both outer ends. This ensures that a particularly high contact pressure is only effective in the middle area 14 of the contact surface 13.

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L ist of references

1 Pressure roller 2 Panel element, chipboard 3 Narrow surface 4 band-shaped covering 5 Rotation axis 6 Hot melt adhesive 7 Sliding shoe 8th additional sliding shoe 9 Inlet zone 10 Run-off area 11 protruding edge 12 Pressure range 13 Pressure surface 14 middle area

Claims (10)

H3946a -13- Protection claims 1. Pressure element (7) for an edge banding machine for gluing a band-shaped covering (4) with an adhesive (6) to a narrow surface (edge) (3) with a straight cross-section of a panel element (2), in particular a chipboard, fiberboard or solid wood panel, characterized, that the pressure element is designed as a sliding shoe (7) and, in particular over its entire length, has a linear pressure region (12). 2. Pressure element according to the preceding claim, characterized in that the surface of the sliding shoe (7) facing the coating (4) tapers to a point in cross-section. 3. Pressure element according to the preceding claim, characterized in that the tip is rounded. 4. Pressure element according to the preceding claim, characterized in that the radius of curvature of the tip is 0.5 to 5.0 mm. 5. Pressure element according to claim 2,
characterized, that the tip is flattened, the flattened pressure area (12) having a width of at most 5 mm, in particular of at most 3 mm. 6. Pressure element according to claim 4 to 5,
characterized, that it has a length of up to 500 mm and in particular of 30 to 300 mm. 7. Pressure element according to one of the preceding claims, characterized in H3946a -14 - that the linear pressure area (12) runs in a straight line. 8. Pressure element according to one of the preceding claims,
characterized, that the linear pressure area (12) runs parallel or obliquely to the longitudinal axis of the sliding shoe and in particular diagonally thereto. 9. System of pressure elements (1, 7, 8) for an edge banding machine for pressing a band-shaped covering (4) coated with adhesive (6) onto a narrow surface (3) (edge) of a panel element (2) with a straight cross-section, in particular a chipboard, fibreboard or solid wood panel,
characterized, that the pressure element to be used first is designed as a pressure roller (1) known per se, the pressure element to be used after that is designed as a sliding shoe (7) according to one of the preceding claims and the pressure element to be used after that is designed as a further sliding shoe (8) which, when pressed, only acts on one or both border areas between the narrow surface (3) and the wide surfaces of the plate element (2), in particular without the covering being bent in the border areas. 10. System according to the preceding claim,
characterized, that the further sliding shoe (8) has a concave pressure surface (13) which essentially consists of two flat surfaces, in particular at an angle of 45 to 60° to one another.