METAL SANDWICH STRUCTURE

Abstract: The invention relates to a metal sandwich structure, comprising a core which consists of a plurality of individual honeycomb sections (3) spaced from each other, and a first and second cover panel (1, 2) which enclose the honeycomb section therebetween. They are attached to the honeycomb sections (3) by welding in such a way that each honeycomb section (3) has its lateral skirts (3a) attached to the first cover panel (1) and each honeycomb section has its top (3b) attached to the second cover panel (2). The honeycomb sections (3) are terminated in bevels (7) at a distance from the lateral edge of a sandwich structure, and that the cover panels (1, 2) have their skirts brought to the proximity of each other by means of deflections (4a, 4b) made at least in the second cover panel (2). Consequently, the cover panels are provided with adjacent skirts (6.1, 6.2) which constitute an attachment flange.

Description: Metal sandwich structure The invention relates to a metal sandwich structure as defined in the preamble sections of claims 1 and 2. The invention is concerned with joining metal sandwich structures to each other and to another surrounding structure. A typical application comprises e.g. joints for deck and bulkhead elements in ships. It is also possible to find applications for the invention in other vehicular industry, such as trains and buses, as well as in construction industry. Traditionally, e.g. ship structures consist of reinforced panel fields, the panel assemblies having beams affixed thereto by welding for a reinforced structure. Joints for such structures are readily designable in such a way that the structures become continuous with a high load-carrying capacity. However, modern ships require structural applications which are more and more lightweight. Lighter structures contribute to an increased cargo carrying capacity in ships. This is particularly essential for fast ships and large cruise vessels. The engine power and loading capacity in fast ships are highly dependable on the weight of on-board structures. The lighter the structures, the less engine power is needed and, on the other hand, the more cargo can be loaded aboard. As far as large cruise vessels are concerned, the ship's stability is an essential design criterion, which requires lightweight structural designs, particularly in the upper deck structures of a ship. Traditionally reinforced or braced panel fields do not afford lightening of the structures. Metal sandwich structures afford a possible weight reduction of as much as 30-50% as compared to a traditional reinforced panel field. One essential problem regarding more extensive use of sandwich structures has to do with joints for these structures. Thus far, sandwich plates have been joined to each other and to surrounding structures by various types of joint elements, such as a square section or a C-section, reference being made to Patent publication EP 0,789,651 as one example of this. Solutions of this type are awkward in terms of both structural strength and productional aspects. A problem is e.g. the attachment of a core to a joint element. The problem of fitting allowance required by field conditions is yet to be solved with currently available joint solutions. In addition, these joints require two-sided welding. In practice, there is often a need to continue or extend a sandwich structure as a single panel. Studies have shown that leaving a core unattached to a joint profile weakens the structure by about 15-20%, which e.g. makes it impossi- ble to use these joints in the upper structures of a cruise ship. As one example for overcoming productional problems associated with a sandwich structure, reference is made to Patent publication WO 99/20461. The cited document discloses two surface plates, between which is arranged a core-forming continuous third plate which is designed in such a way that the two surface plates remain spaced from each other and in a partial contact with the intermediate plate. The surface plates are in contact with each other by way of planar skirts provided at the edges and used for welding the same together. The edges of an intermediate plate are also provided with a skirt, which is secured by welding between the planar skirts of the surface plates. Here, the skirts have just a single function as a weld surface. According to the teachings of the cited publication, this is the only function for the skirts and, thus, there is no suggestion that the skirt be dimensioned in such a way that it could function as an attachment flange even after the working allowance is gone. Moreover, a continuous core as disclosed in the above- cited publication sets constraints regarding the dimensions of an entire structure. The above problems are eliminated or substantially mitigated by the inven- tion set forth in the characterizing sections of claims 1 and 2. These joint solutions provide extensive applications for metal sandwich structures, e.g. in deck and bulkhead structures of fast ships, as well as in upper structures of cruise ships. The solutions assist also in making sandwich designs more popular in other means of transport, such as trains, as well as generally in various applications of construction industry. The attachment flange construction of the invention enables the easy attachment of a sandwich structure to a basic structure, as well as the substantial mitigation of a problem regarding the fitting allowance between a basic structure and a sandwich structure. In addition, the individual honeycomb sections of a core provide more flexibility in terms of determining the design and strength of a sandwich structure. Preferred embodiments of the invention are disclosed in the non- independent claims. The invention will now be described with reference to the accompanying drawings, in which: Fig. 1 shows the edge of a sandwich structure in an axonometric view. Fig. 2 shows a structural alternative for the sandwich structure of fig. 1. Fig. 3 shows a second structural alternative for the sandwich structure of fig. 1. Fig. 4 shows a fourth panel assembly for the sandwich structure of fig. 1. Fig. 5 shows a second embodiment for the invention. Fig. 1 depicts a metal sandwich structure of the invention. It comprises a core made up from basically honeycomb-shaped sections 3, a first cover panel 1, and a second cover panel 2. The cover panels 1 and 2 enclose the core therebetween. The individual honeycomb section 3 comprises opposite flanks, which extend in cross-section obliquely from a first end to a second end and which are connected to each other at the first end across a substantially flat top 3b. The honeycomb section 3 has the second ends of its flanks extending laterally outward with respect to the plane of the top 3b and constituting flat lat- eral skirts 3a for the open side of the honeycomb section 3. The honeycomb section 3 is terminated in a lengthwise direction in a chamfer or bevel 7, which commences from the top level and finishes at the level of the skirts 3a. The bevel 7 has an extension which comprises a skirt 6.3, which is coplanar with the top 3b and extends laterally a distance lengthwise of the honey- comb section 3. Thus, the skirts 3a and 6.3 constitute a flat or planar collar around the open end of the honeycomb section 3. The first cover panel 1 is attached against the flat collar 3a, 6.3 of the honeycomb section 3. The first cover panel 1 and the honeycomb section 3 are preferably welded together, for example by laser welding, at least along the lateral skirts 3a of the honeycomb section 3. The second cover panel 2 is similarly attached to the honeycomb section 3 by welding it together with the top 3b. The second cover panel 2 is formed with deflections 4a, 4b co-directional with a lengthwise outer skirt of the cover panel 2, said cover panel 2 com- ' prising therebetween a section 5 which is shaped like a ramp. The ramp section 5 has a contour which is complementary to that of the bevel 7 of the honeycomb section 3, the ramp section 5 and the bevel section 7 having their plate surfaces preferably facing and in contact with each other and attachable to each other by welding, if desired. The ramp section 5 has an ex- tension which comprises a flat skirt 6.2, the plane defined thereby being aligned by means of the deflection 4b to be co-directional with the plane defined by the skirt 6.3 of the honeycomb section 3 and a skirt 6.1 of the first cover panel 1. Thus, the skirts 6.1, 6.2 are brought to the proximity of each other by means of the ramp section 5 defined by the deflection 4a, 4b. The skirts 6.1, 6.2 constitute an attachment flange. The honeycomb section 3 has its collar 3a, 6.3 extending at least partially between the attachment-flange forming skirts 6.1, 6.2, preferably up to the outer edge of an attachment flange constituted by the cover panels 1 and 2. Consequently, the attach- ment flange is constituted by three panel layers 6.1, 6.2 and 6.3. Between the cover panels 1 and 2 there is respectively provided a number of honeycomb sections 3 spaced from each other, the intermediate panel layer 6.3 being discontinuous lengthwise of the sandwich structure. The honey- comb sections 3 may have a spacing which is arbitrarily optional within the strength requirements of a sandwich structure prior to welding the honeycomb sections to the cover panels 1 and 2. With this arrangement, the length of a sandwich structure can be selected as desired according to a particular application. Figs. 2, 3 and 4 depict optional means for securing a sandwich structure to a basic structure. The figures show the basic structure in the form of a vertical wall, which is provided with a horizontally projecting bracket 8 for securing an attachment flange thereto. In fig. 2, the attachment flange comprises the skirts 6.1 and 6.3, between which is a gap for the bracket 8. The gap is produced preferably by shaping the skirt 6.3 of the honeycomb sections 3, e.g. by deflecting the skirt 6.3 away from the skirt of the first cover panel 1. The sandwich structure is fit- ted in position by bringing it to rest upon the bracket 8 in such a way that the bracket 8 settles between the skirts 6.1 and 6.3. The attachment flange constituted by the skirts 6.1, 6.2 and 6.3 have an original length which preferably exceeds that shown in the figures, and it is cut to its depicted length in situ. This offers the advantage of facilitating the installation measuring process as flange dimensions can be adapted to real dimensions existing at the installation site. Dimensions of the bracket 8 can also be altered. Preferably, the bracket and the flange are designed in such a way that the bracket 8 extends within the flange across the entire flange. Thus, the weld joining the bracket 8 and the flange can be provided in the longitudinal direction of the honeycomb section 3 with a length which is sufficient for a sturdy joint. Fig. 3 depicts a second joint structure for a flange/bracket joint. It shows the various layers 6.1, 6.2 and 6.3 of an attachment flange directly on top of each other. Thus, the attachment flange can be set in its entirety on top of the bracket 8. Fig. 4 depicts a third joint structure for a flange/bracket joint. It shows the flange provided with a gap as in the first joint structure, but this time the gap is between the skirt 6.2 of the second cover panel 2 and the skirt 6.3 of the honeycomb section 3. Fig. 5 depicts a second embodiment for the invention. Unlike the foregoing structures, the honeycomb sections 3 are set in the longitudinal direction laterally between the two cover panels 1 and 2, the attachment flange being composed in the vicinity of a second lengthwise skirt 3a 1 of the outermost honeycomb section 3. Thus, the honeycomb section 3 has its bevelled flank T and the second cover panel 2 has its ramp section designed complementary to each other. The attachment flange can have its layers 6.1, 6.2 and 3a' directly on top of each other or, as described in a preferred embodiment, the attachment flange can be provided with a gap for a bracket. If necessary, the skirt 3a' of a honeycomb section, which constitutes a part of the attachment flange, can be designed to have a width which exceeds that of other skirts 3a of the honeycomb section 3.

Claims: Claims 1. A metal sandwich structure, comprising a core which consists of a plurality of individual honeycomb sections (3) spaced from each other, and a first and second cover panel (1, 2), which enclose the honeycomb section therebetween and are attached to the honeycomb sections (3) by welding in such a way that each honeycomb section (3) has its lateral skirts (3a) attached to the first cover panel (1) and each honeycomb section has its top (3b) attached to the second cover panel (2), characterized in that the honeycomb sections (3) are terminated in bevels (7) at a distance from the lateral edge of a sandwich structure, and that the cover panels (1, 2) have their skirts brought to the proximity of each other by means of deflections (4a, 4b) made at least in the second cover panel (2), the cover panels being provided with adjacent skirts (6.1, 6.2) which constitute an attachment flange. 2. A metal sandwich structure, comprising a core which consists of a plurality of individual honeycomb sections (3) spaced from each other, and a first and second cover panel (1, 2), which enclose the honeycomb section therebetween and are attached to the honeycomb sections (3) by welding in such a way that each honeycomb section (3) has its lateral skirts (3a) attached to the first cover panel (1) and each honeycomb section has its top (3b) attached to the second cover panel (2), characterized in that the honeycomb section (3) outermost in the core has an outermost bevelled flank (7') at a distance from the lateral edge of a sandwich structure, and that the cover panels (1, 2) have their skirts brought to the proximity of each other by means of deflections (4a, 4b) made at least in the second cover panel (2), the cover panels being provided with adjacent skirts (6.1, 6.2) which constitute an attachment flange. 3. A structure as set forth in claim 1, characterized in that the honeycomb sections (3) have their attachment skirts (3a) and the bevel (7) has its finish- ing skirt (7a) extend between the attachment-flange forming skirts (6.1, 6.2) of the cover panels (1, 2), the attachment flange consisting of three panel layers, including an intermediate layer (6.3) which is discontinuous in the lengthwise direction of the edge of a sandwich structure so as to match the spacing between the honeycomb sections (3), which is arbitrarily optional prior to attaching the honeycomb sections (3) to the cover panels (1, 2) by welding. 4. A sandwich structure as set forth in claim 2, characterized in that the attachment flange is composed at a lengthwise skirt of the honeycomb section (3), whereby a skirt (3a') adjoining the bevelled flank (7 1 ) of the honeycomb section constitutes the intermediate panel layer for an attachment flange (6.1, 3a', 6.2). 5. A structure as set forth in any of preceding claims 1-4, characterized in that there is a gap between the attachment-flange forming panels (6.1, 6.2, 3a', 6.3) for a bracket (8). 6. A structure as set forth in any of preceding claims 1-5, characterized in that the attachment flange has its panel layers (6.1, 6.2, 3a', 6.3) directly on top of each other and thus mountable on top of the bracket (8). 7. A structure as set forth in any of preceding claims 1-6, characterized in that the welding attachments are made by laser welding.

Inventors: IMMONEN VELI-PEKKA, KAINOMAA HANNU, KUJALA PENTTI, SALMINEN ANTTI, IMMONEN, VELI-PEKKA, KAINOMAA, HANNU, KUJALA, PENTTI, SALMINEN, ANTTI
Applicants: IMMONEN VELI PEKKA, KAINOMAA HANNU, KUJALA PENTTI, SALMINEN ANTTI, IMMONEN, VELI-PEKKA, KAINOMAA, HANNU, KUJALA, PENTTI, SALMINEN, ANTTI
Application year: 2001
Main classification: B21D47
IPC codes: E04C2