The present invention relates to a layer structure for fireproof structures on ships and offshore constructions.

Ships are built mostly of steel and aluminum. The metal plate constructions must be coated with an agreeable material, at least in passenger and crew rooms, because an uncovered metal plate is a cold and dreary furnishing material, even if painted. To attach the coating material various mechanical fasteners or double sided tape are used. The most widespread mechanical fasteners are rivets and screws. When a coating plate is fastened to the metal plate frame an intermediate layer is put ih between the coating and the metal plate. As an intermediate layer double sided tape can be used, while screws only secure the firmness of the coating. Alternatively, chipboards or other furnishing plates can be used. Chipboard or other similar materials improve the insulating qualities of the structure, but at the same time increase the fire load of the cabin construction.

In case of tape fastening wide double sided tape ribbons are attached to the metal plate or the coating plate and the other plate is pressed onto the tapes.

Disadvantages of the mechanical fastening methods are high production costs and increase in weight and fire load of the structure, particularly when an intermediate layer is put under the coating.

Low endurance in prolonged use is a disadvantage of the tape fastening method.

Properties of tape impair with time and it also can unfasten under the influence of humidity and temperature variations of the structure, as well as of stress variations. Treatment of double sided tapes is difficult and it can not easily be automatized, causing thus high production costs. Tape fastening needs large amounts of tape, that furthermore increase the production costs of the structure. Moreover, tape fastening is not homogeneous, because usually gaps are left between the tape ribbons to save

the tape and to facilitate the production. The gaps have many disadvantages. Humi¬ dity can condense in the gaps damaging particularly the coating plate and wrinkling it. Humidity also increases risks of corrosion and moulding. Troubles caused by humidity and temperature variations are particularly serious in tropical and arctical conditions and tape fastening is not a fully acceptable method for these conditions.

Since thin materials are used as coating, the surface of the structure will be uneven, because the coating subsides at the gaps making the surface wavy. Even if the tapes would be fastened side by side without gaps, it is not possible to avoid the uneven surface, because the tapes have an ununiform thickness and they distort differently by the fastening. Therefore there is always a discontinuity at the seams of the tapes. When the structure is subject to stresses, that are normally present in seafaring structures, the coating can split at the discontinuities. Splitted surface has unpleasing appearance and it is very difficult to repair. All in all, the material costs of the layer structure built utilizing the double sided tape are high and the production is expensive and time-consuming.

Gluing would be a cheap method for producing coated metal plate layer structures. However, till now utilizing gluing methods in producing classified fireproof structures has been impossible. Fireproof glues evolve carbon dioxide by hardening and because metal plates and most of the coating materials do not let gases through, at least not in large amounts, the evolved gas develops cavities between the coating and the metal plate and detaches the plates from each other. Thus, fireproof glues are difficult to use for gluing other than porous materials. Besides that, while most of the fireproof glues do not attach smooth metal surfaces properly, very few glued coated layer structures are produced.

The aim of the present invention is to achieve a layer struc-ture whereas the coating plate is attached to the metal plate by gluing.

The invention is based on making holes in the plate acting as the frame of the layer

structure, through which the gas evolving from the glue can exit the glue seam.

More specifically, the layer structure in accordance with the invention is characterized by what is stated in the characterizing part of claim 1.

The invention provides outstanding benefits.

The production cost according to the invention is considerab-ly less than that of the prior art structures. All production stages of a layer structure can be readily automa- tized if necessary, whereas the production will be quick and the production costs per unit will be low. Although if the layer structure would be fabricated mostly by hand, glue is readily spread onto the coating layer or the frame layer using appropriate tools, and the production cost can be low also in this case. Portioning of the glue is easy, for it can be spread by spraying onto the plate, whereas excessive glue is squeezed through the ho-les of the frame plate. The layer structure is very light and almost not inflammable, because there is no need to use easily burning materials, like chipboards. The structure is particularly durable, because in addition to the normal fastening strength of the glue the plates attach to each other by means of glue pins formed in the holes of the metal plate.

Weight and rigidity of the structure can be optimized by varying the size and number of the holes, whereas the most effective use of material is achieved. The gas evolving in hardening of the glue can exit the seam through the holes in the metal plate, whereby no gas cavities form in the seam and it will be durable over all the glued area. Coating material can be thinner than used to be earlier, because the background material is level and no wavelike surface will be formed. Besides that, even fireproof glues are cheaper than relatively expensive double sided tapes. The structure satisfies the fire safety regulations enacted for ship cabins.

The invention is next examined in detail with the help of the attached drawings.

Figure 1 is a sectional side view of a layer structure in accordance with the invention.

Figure 2 is a partially sectioned view from the direction of the coating plate of the layer structure illustrated in Fig. 1.

Figure 3 is a sectional view of an embodiment of the metal plate used in a layer structure in accordance with the invention.

Figure 4 is a view of Fig. 3 from the direction of the plane of the plate.

The layer structure in accordance with the invention comprises of perforated metal plate 3 that is attached by means of glue layer 2 to coating material plate 1. Glue 2 spread between plates 1,3 is squeezed into the holes 5 of the plate and forms glue pins 4. The layer structure is produced as follows. The surface of coating material 1 to be glued is cleaned before gluing and a layer of glue is spread onto the coating material plate 1. Next coating material plate 1 is attached to perforated metal plate 3, whereas the excess of glue 2 spread on coating material 1 penetrates to the holes of metal plate 5 and further to the other side of plate 3. Glue 2 flown into holes 5 forms by levelling behind metal plate 3 glue pin 4 that attaches coating plate 1 and metal plate 3 firmly to each other in all conditions.

Plates 1,3 can be pressed to each other e.g. by layer squeezer or vacuum squeezer. Carbon dioxide evolving in hardening of fire proof glue 2 during the squeezing flows out from the gap between plates 1,3 through holes 5, whereas glue 2 will be levelled against the surfaces 1,3 and no gas bubbles impairing the glue seam form. According to the experiments carried out by the applicant the gas flows out even when the squeezing force is not homogeneous. Also heterogeneous spreading of glue does not impair the quality of the structure because excessive glue can flow out from the seam during the squeeze.

Fig. 3 and 4 show a feasible scheme of perforation of metal plate 3. This perforation scheme is designed for cabin doors. According to the scheme 10% of the area of the metal plate is removed by holes 5. Diameter of a hole d is 7 mm, and distances between central points of holes 5 A and B are 20 mm. The diameter of holes d and distances between them are determined mostly by the required rigidity. Thus, choosing the perforation scheme is quite free. The share of holes may vary at least 5 - 70 % of the area of the metal plate and the shape of holes can be chosen freely. Thus, using a metal plate with ready perforation as a laminate is preferred whenever it is possible. The 10% perforation presented above suits well for manufacturing doors and other analogous structures that need to be comparatively rigid. In components of carrying structures, like walls, a larger share of holes can be used, advantageously 30%, because in this case a carrying structure usually consists of shell structures assembled of several plates, where sufficient carrying strength is ac¬ hieved by smaller rigidities of each individual plate. An important feature of the invention is that it does not restrict in any way the share of holes in the area of the plate, but the share must be reckoned for each structure according to the strength requirements. The examples described above illustrate perforation schemes appropriate only for certain purposes. The glue layer does not have to reach the holes of the metal plate, because the main purpose of the holes is to let the gases flow out of the seam. However, better attachment between the plates is achieved, if glue reaches partly at least to some of the holes. In the most preferable embodiment glue forms pins that improve the attachment strength as illustrated in the examples above.

The layer structure in accordance with the invention is particularly suitable for manufacturing various doors, like WC doors, cabin doors, communicating doors, and maintenance doors. It suits for manufacturing wall and ceiling modules as well as furniture. Coating material, glue and the metal plate acting as frame of the structure can be chosen according to the purpose of the structure. It is even possible to utilize stiffened or folded frame plate, but in that case the coating material must be rigid enough not to allow bending it to the grooves of the folds, or glue must be

used sufficiently to fill the folds of the plate. Obviusly, if the folds are filled with glue these can not be too deep.

The structure in accordance with the invention was tested for temperature changes with simultaneous examination of the strength of attachment. In the test a layer structure as described above was used, with the share of holes being 10%, and the perforation scheme as shown in Fig. 4. The test was carried out as follows:

Samples: Cabin door assembled of three components (two parts 680 x 800 mm ² , one part 680 x 395 mm ² )

Purpose of the To investigate the influence of temperature testxhanges to surfaces of the cabin door

Results: Preparation of the samples

After transportation to the test site the transporting packa¬ ge was opened. Thermoelements were attached to the outer steel surfaces of the larger parts of the doors immediately after unpacking. The larger parts were packed again in the PE-plastic wrapping. The smaller part was transported to a room with constant conditions (23±2°C, relative humidity 50+5%)

Temperature change test

The larger parts of the door were exposed to the following cycle:

1. Freezing -20°C, 18 hours

2. Cycle -20°... +50°C four times (6 h +50°C in the

oven, and 18 h -20°C in the refrigerator)

3. Cycle -10°C...+50°C ten times (3 h +50°C in the oven, and 3 h -10°C, and 18 h +23 °C)

Changing the temperature from -20°C to +50°C took ca 4 hours according to the temperature measurements.

After the test cycle the PE-film was remo-ved and the samples were put into the roomwith constant conditions (23±2°C, relative humidity 50+5%)

After the temperature change test no visible changes were observed.

Attachment strength of the surface laminate

The attachment strength of the samples were examined by the pull test. The pulling hanks (ø 20 mm) were glued to the surface of the door. The area under the hank was removed by boring and the attachment strength was measured utilizing the pneumatic pulling device at speed 4 N/mπAnin.

The results are presented in Table 1. The unfastening occurred in all cases by breaking up the attachment between the steeland the laminate.

Sample Attachment strenght N/mm ² 1 2 3 4 5 6 Av

Reference sample 1,1 1,2 1,0 1,6 1,4 1,2 1,3

Test sample 1 1,4 0,9 1,4 1,4 1,2 1,2 1,2

Test sample 2 1,8 1,4 1,0 1,8 1,4 1,5

Av = average

The reference sample was the sample that was held at constant conditions, and the test samples were the samples tested by changing the temperature.

Conclusions: According to the test results the periodical temperature change test had no influence neither on appearance nor on the attachment strength of the test samples.

In agreement with the test it is apparent that the structure in accordance with the invention endures without any changes the conditions where the structure accomplished utilizing double sided tapes is not applicable.