DE29622783U1 - Spacer for spacing sheets to be treated in immersion baths - Google Patents

Description

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* ·· Gerhard Ö.Schöfer PO Box 10 11 61
Maximilianstrasse 6
D-30085 Munich ·· European Patent Attorneys
Representatives of European patents e-mail: upon request
Telegram/cable:
MAXIMARK® MQnchtn

Odenwald Chemie GmbH HJM/Sz

Spacers for spacing sheets to be treated in immersion baths

In the automotive industry, it is known to insert spacers between metal sheets using foam, which allow the metal sheets to "float" in a way. The at least partially compressible properties of the foam prevent the "packages" formed from the metal sheets, bows and spacers arranged between them from buckling or collapsing. It is known to insert the foam spacers between the bows and the metal sheet.

It is also known that the treatment agents in immersion baths, spray baths and washing systems, which are used for example for derusting, degreasing, phosphating, painting (KTL) and the like, are partially absorbed by the foam. In subsequent production stages, these media escape in the liquid or vaporous state and then cause sometimes very significant damage. For example, a phosphating agent can lead to the coagulation of the KTL (cathodic (electrophoretic) immersion painting), which results in cross-linking problems. The leakage of solutions from the foam after the immersion bath over finished but not yet hardened sheet metal coatings also destroys the painted surfaces, so that

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the entire treated sheet cannot be reused as "scrap" or must be reworked. Occasionally, the foam also hardens/if the immersion bath agents in it coagulate. This impairs the resilience of the foam, i.e. its elastic compressibility.

It cannot be ruled out that the migration of components from the foam, e.g. through the re-release of previously absorbed solutions, can lead to concentrations of substances building up that cause the immersion bath to "tip over" and require it to be replaced very quickly. Depending on the size of the immersion bath, the costs for disposal, loss of production or possible remedial work on damage can quickly run into millions of DM.

The invention is therefore based on the object of improving such spacers with simple means so that these disadvantages can be avoided.

The invention is characterized in claim 1 and in subclaims preferred embodiments of the invention are claimed.

According to the invention, a foam core is surrounded at least on the largest part of its peripheral surface by a moisture-proof covering film, which can be designed as a tube, for example, and into which the foam core is inserted, or which is made up of two strips laid around the foam core and welded to form a tube, for example. Other covering options are also possible. The ends of the covering film should protrude far enough over the foam core on the front side that the ends can be welded together to seal the foam core on the front side, for example.

can be glued or even just folded over.

It is already known (EP-B-O 201 675) to manufacture blocks for keeping distance from polyethylene foam and to insert them between, for example, door panels of motor vehicles when they are stacked on top of each other, so that the stacked door panels do not line up next to each other during transport and their already painted surfaces are not damaged. If such spacer blocks are covered on the top with, for example, an adhesive film, this serves to attach them to the door panel in question. A solution to the above-mentioned task is not possible with such a spacer.

In addition, it is also known (DE-OS 43 17 693) to insert a molded foam into a cover made of plastic, for example, and to use the entire body as transport protection. The cover consists of paper fiber fleece or similar material that absorbs and allows gas and moisture to pass through, so that the above-mentioned task cannot be solved in this way either.

It is also known (DE-PS 43 06 059) to insert a foam core of cushions for patient beds into a protective cover and to weld this so that, for example, liquid secreted by incontinent patients does not render the cushion core unusable. Since gas exchange between the cushion and the external environment must nevertheless take place, an opening is cut into the outer cover and closed from the inside with an additional film that is liquid-tight but gas-permeable.

Furthermore, it is known (DE 91 15 773 U) to use plastic films

formed pockets, which may be perforated, are filled with elastic grains in order to produce elastic mats that serve as impact sound insulation.

Finally, it is also known (DE-OS 38 26 011 and DE-PS 40 28 895) to insert bags filled with foam components or foam bodies held in a compressed state by a bandage into cavities in vehicle bodies and to heat them on the spot so that the foam components foam up or the plastic bandage melts and the foam expands and can fill the cavities. This does not solve the problem mentioned above either.

In the invention, the spacer serves as an aid during treatment in immersion baths with the purpose that immersion bath liquid cannot penetrate into the foam core and therefore there is no danger that any absorbed immersion bath material will escape from the immersion bath after leaving the sheets, in particular automotive sheets, after the usual draining and dripping at a later undesirable time and cause damage to the further process and/or the environment.

It is recommended to use polyethylene (PE) as the wrapping film, especially a film thickness between 15 and 100 μm.

In addition, it is recommended that the wrapping film be placed as close as possible to the peripheral surface (here: the outer surface) of the foam core; wrapping films that shrink when heated are particularly suitable for this purpose. The spacer is then a "one-piece" component, even if it is made from two or more parts.

The material of the wrapping film is adhesive at temperatures between 70° C and 170° C and at temperatures between 70° C and 170° C the wrapping film can melt.

The foam core can be closed-cell, but a material that is at least partially open-celled and is preferably impregnated with an impregnating agent is recommended. Polyacrylate and/or bitumen are recommended as such. The foam core is preferably made from PUR soft foam, impregnated with modified polyacrylates and bitumen, as foam material. Such impregnated foam cores are preferably made from the material known under the trademark "O.G.-BAND 99", in which mixtures of polyacrylate and bitumen are used as impregnating agents.

The cross-section of the foam core is preferably rectangular in order to enable the sheets to be supported well on top of one another without the spacers rolling away. The ratio of the two side surfaces of the rectangular core cross-section should be approximately 1 to 3, in particular 1.2 to 2.4. Other geometric shapes and dimensions are also possible for special applications.

In the preferred use of spacers according to the invention for separating or floatingly storing Kf&zgr; sheets, the treatment of these in spray or immersion baths takes place according to the invention as follows:

First, the spacers are placed between the bow and the sheet metal before the sheets are placed in the spray or immersion bath. Then the package of surfaces separated from each other by the spacers is passed through the bath.

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and transported out of it again. Finally, the treated sheets with the spacer are then fed into a drying process. It is useful if the material of the wrapping film behaves in such a way during the drying stage that it becomes adhesive and forms an adhesive bond between the sheet and the foam core. The film wrapping melts away at the sides at the temperatures in the drying stage, so that the foam core is then released, while in the area between the foam core and the sheet the melting wrapping film leads to a good bond between the sheet and the foam. This means that the foam core is, in a sense, glued to the bows behind the sheet and to the outer sheet.

Preferred embodiments of the invention are explained in more detail below with reference to the drawings, in which:

Figure 1 is a partial view of a spacer according to the invention, in which part of the wrapping film is cut away;

Figure 2 is a schematic cross-section through the spacer of Figure 1;

Figure 3 shows a schematic cross-section through a tubular wrapping film before being pulled onto the foam core;

Figure 4 shows a schematic cross-section through a foam core;

Figure 5 is a schematic side view of a flat foam core sandwiched between two wrapping film strips;

Figures 6-8 show schematic cross sections of spacers according to the invention and

Figure 9 is a schematic side view of the insert between the bow and the outer panel.

According to Figure 1, the foam core 1, which is essentially rectangular in cross-section and consists of open-cell PüR foam impregnated with impregnating agents, is surrounded by a polyethylene covering film 2. At one end of the foam core 1 hidden within the covering film 2, the protruding ends 2a of the covering film 2 are connected to one another, e.g. welded; there they form a liquid-tight covering of the relevant end face of the foam core 1. On the left side of Figure 1, the covering film 2 is cut away to show the foam core 1.

According to Figure 2, the covering film 2 fits tightly against the peripheral or lateral surfaces of the foam core 1 and forms a kind of "one-piece structural unit" with it.

In fact, according to Figures 3 and 4, the spacer consists of the foam core 1 and the wrapping film 2 placed around it, which is still shown in cross-section as a tube in Figure 3.

The spacer can be manufactured according to Figure 5, for example, by placing the foam core 1 on a lower wrapping film strip 2b and placing an upper wrapping film strip 2b over this in such a way that both wrapping film strips 2b protrude over the foam core 1 at the front with their ends 2bl. In many applications, the over-

standing ends 2bl, for example as shown in Figure 1, are put together and welded together. But even if they are not welded together, they largely fulfill their "sealing tasks" for example in that in immersion baths for cleaning, pretreatment or painting the incoming fluid presses the part of the covering film that protrudes over the foam core 1 - at the ends 2bl - against the front side of the foam core 1 and largely prevents the penetration of the immersion bath medium in the form of solutions or the like.

According to a special embodiment of the invention, the foam cores 1 can be partially or completely provided with a sealing coating, e.g. a "skin" made of PUR, which replaces the wrapping film.

The schematic cross-sectional representation of the spacer according to Figure 6 consists again of the foam core 1 and the covering film 2, which consists of two parts that are placed over the foam core from below and above and are connected to one another, for example thermally welded, along the ends 5 that overlap at the edges.

A corresponding design is shown schematically in cross-section in Figure 7, with the difference that the foam core 1 is oval due to welding punches or the lateral welding of the wrapping film 2, so that the wrapping film 2, consisting of a lower and upper part, also adapts to the outer contours of the foam core I. Here too, the lateral edges 5 of the wrapping film 2 are welded together using a longitudinal welding process.

In the embodiment of Figure 8, the foam core 1 is rectangular in cross-section; the one-piece wrapping film 2 envelops the

Foam core 1 is seamless. The covering film 2 is applied to the foam core, for example, by dipping or spraying.

According to Figure 9, spacers consisting of the foam cores 1 and the wrapping films 2 are inserted between body panels 3 that are many meters long and their support elements 4 in order to store them in a "floating" manner. Such systems of panels 3, support elements 4 and spacers are held together by suitable means and guided through the treatment stages so that most of the surfaces of the panels 3 can be reached by the treatment medium. As a result of the use of the wrapping films, it is avoided that treatment medium is absorbed by the foam cores 1 and, on the one hand, escapes from the foam cores 1 after leaving the relevant treatment stages and hits the treated panel surfaces, causing considerable problems there, or, on the other hand, fills the hollow spaces in the foam and later no longer guarantees "floating" storage.

Further developments of the invention for assembly auxiliary functions are the equipment with self-adhesive coatings on the film that are safe for the KTL process or the pre-compression of the foam parts by applying vacuum technology using film in order to adapt them to predetermined areas of use in, for example, gaps and joints.

The invention is also extremely advantageous for environmental reasons. It prevents environmentally harmful media from collecting in the foam pores and cavities and causing damage during further treatment or recycling of the foam.

It is recommended that the circumference of the tubular

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The wrapping film 2 according to Figure 2 is dimensioned such that it essentially corresponds to the sum of the side lengths of the rectangular cross-section of the foam core 1 of Figure 1. A tolerance of approximately +/- 20% can be accepted without further ado.

The wrapping film 2 can also have self-adhesive properties or be provided with a self-adhesive coating on its outer surface to facilitate adhesion to the objects, such as metal sheets 3.

In some cases it is expedient to form the wrapping film 2 as a composite film including a barrier layer with the polymer component polyamide (PA) in order to prevent the passage of air through the wrapping film 2 during the compression of the foam part by vacuuming. By mechanically destroying it, e.g. piercing the wrapping film, the foam strip expands after application in the desired position.

Claims (17)

Hans-Jürgen Müller Gerhard D. Schupfner e-mail: upon request PO Box 101161 TelegramVcable: Maximilianstraße 6 European Patent Attorneys MAXIMARK® Some * D-300S5 Some European Licensed Agents Odenwald Chemie GmbH HJM/Sz CLAIM FORMULATION 1. Spacer for spacing metal sheets to be treated in immersion baths, made at least partially from compressible or compressible foam, characterized in that the foam is surrounded as a foam core (1) by a moisture-proof covering film (2). 2. Spacer according to claim 1, characterized in that the wrapping film (2) is designed as a tube. 3. Spacer according to claim 2, characterized in that the wrapping film (2) is welded from two webs (2b). 4. Spacer according to claim 2, characterized in that the enveloping film (2) is produced by spraying the film material onto the foam core (1) and solidifying it. 5. Spacer according to one of the preceding claims, &iacgr;&Lgr;&Agr;&KHgr;&Igr;&Mgr;&Lgr;&Bgr;&KHgr; Form III characterized in that ends (2a, 2bl) of the wrapping film (2) protrude beyond the foam core (1) at the front and are connected to one another there to seal the foam core (I) at the front. 6. Spacer according to one of the preceding claims, characterized in that the covering film (2) is a composite film with a barrier layer with the polymer component polyamide (PA). 7. Spacer according to one of the preceding claims, characterized in that the covering film (2) consists of polyethylene (PE) or polyurethane (PU). 8. Spacer according to one of the preceding claims, characterized in that the wrapping film (2) has a film thickness between 15 and 100 µm. 9. Spacer according to one of the preceding claims, characterized in that the wrapping film (2) shrinks when heated. 10. Spacer according to one of the preceding claims, characterized in that the wrapping film (2) has a self-adhesive outer coating or has self-adhesive properties itself. 11. Spacer according to one of the preceding claims, characterized in that the material of the wrapping film (2) at temperatures melts between 70° C and 170° C. 12. Spacer according to one of the preceding claims, characterized in that the material of the wrapping film (2) bonds the foam to the adjacent surfaces at temperatures between 70° C and 170° C. 13. Spacer according to one of the preceding claims, characterized in that the foam core (1) consists of at least partially open-cell material. 14. Spacer according to claim 13,
characterized in that the foam core (1) is impregnated with an impregnating agent. 15. Spacer according to claim 14,
characterized in that the foam core (1) is impregnated with polyacrylate and/or bitumen. 16. Spacer according to one of the preceding claims, characterized in that the foam core (1) has PUR soft foam as the foam material. 17. Spacer according to one of the preceding claims, characterized in that the cross section of the foam core (I) is essentially rectangular with a ratio of the two side surfaces of approximately 1:1 to 1:3.