FR2614968A1 - Wooden structures which can be delivered as detached parts, particularly furniture or frameworks and construction methods - Google Patents

Abstract

The subject of the invention is wooden structures which can be delivered as detached parts, particularly furniture or frameworks and methods for constructing the latter. A wooden structure according to the invention includes straight or curved elongate wooden pieces which work in bending and which are connected in pairs by crosspieces 5. Each elongate piece is composed of at least two layers 4a, 4b which are applied against each other by keys 9 which interact with bolts 10 which are screwed into metal pieces 12 inserted in the crosspieces. Each layer 4a, 4b is composed of elementary sections which are pressed end to end against each other, the joints 6 between sections of two layers being offset. Prestress cables 11 pass through the crosspieces 5 making it possible to keep the elongate pieces in compression. One application is the construction of furniture or frameworks which can be delivered as detached parts.

Description

DESCRIPTION
Wooden structures available in spare parts, in particular furniture or frames and methods of construction thereof.

 The subject of the present invention is wooden structures which can be supplied in spare parts, in particular furniture or frames and methods of construction thereof.

 The technical sector of the invention is that of wooden constructions.

 The wooden structures generally comprise elongated parts which can be rectilinear or curved, for example beams in the case of a frame or beams of furniture or amounts of ladder etc., which must work in bending .

 Traditionally, these pieces are made of solid wood and the wood fibers are arranged parallel to the longitudinal axis.

 Also known are elongated pieces of glued laminate which are made up of a plurality of lamellas joined side by side and glued together at the factory.

 The transport and handling of elongated parts, whether of solid wood or glulam poses problems because of the dimensions of these parts.

 An object of the present invention is to provide wooden pieces of elongated shape forming part of wooden structures which are composed of elementary sections of reduced length, which are assembled end to end at the very places of use, which allows to deliver these structures in spare parts (in Kit) forming packages of reduced bulk.

 This objective raises the problem of finding an assembly method between successive elementary sections, which makes it possible to withstand bending forces and in particular the tensile stresses in the case of parts which must work in bending and to find at the same time a assembly mode which can be easily carried out by a user without requiring complex bonding installations or special tools.

 The wooden structures according to the invention comprise wooden parts, curved or straight, of elongated shape, which work in bending and which are composed, in known manner, of several layers juxtaposed side by side but not glued together.

 The objectives of the invention are achieved by means of wooden structures of the above type, in which each layer consists of a plurality of elements which are delivered separate and which are assembled by the user who applies them end to end. butt against each other, so that the joints between elements of the various layers are alternated and said structure further comprises prestressing cables which are delivered disassembled and which are laid and tensioned by the user in order to compress said juxtaposed elements longitudinally.

 Advantageously, a structure according to the invention comprises, moreover, crosspieces which connect two by two together two elongated parallel pieces and which comprise, at their end, a tenon which is engaged in a mortise which crosses said juxtaposed layers and it comprises, in addition, keys which bear against the external lateral flank of said elongated parts and which each cooperate with a bolt which passes through said key and which is screwed into a metal part which is inserted into said cross member and which comprises a threaded hole in which said bolt is screwed.

 In this case, a structure according to the invention comprises two prestressing cables which are housed in channels which pass right through said cross members.

 The method for constructing structures according to the invention comprises the following operations: industrially prefabricated wooden elements, curved or straight, of short length, intended to be juxtaposed end to end to constitute elongated parts composed of at least two juxtaposed layers whose joints are alternated and crosspieces intended to connect two to two two elongated parts and to maintain said layers applied against each other, by means of keys and bolts which pass through said keys and which are screwed into pieces of metal inserted into housings perpendicular to said sleepers, packages are delivered to users containing, in separate pieces, said elements, said sleepers, said keys, said metal parts, prestressing cables and tensioning bolts of said cables and the user itself performs the assembly by juxtaposing end to end said elements to constitute said part s elongated, it assembles said crosspieces with said parts by means of said keys and assembly bolts, it sets up the prestressing cables and puts them in tension to obtain overall cohesion.

 The invention results in new wooden structures which are delivered in separate parts and which are assembled by the user himself without requiring any bonding operation or any complex tooling.

 The wooden structures according to the invention can be, for example, furniture frames, in particular armchairs, frames, ladders, railings, gates, etc., and, in general, all structures comprising parts made of parallel, elongated woods. which work in flexion and which are connected to each other by crosspieces.

 The method according to the invention makes it possible to obtain pieces of elongated shape which are composed of much shorter elementary sections, which makes it possible to use wood of small caliber, much cheaper than wood of great length.

 In the case of curved pieces, the method according to the invention makes it possible to cut each curved elementary section, so that the wood fibers are substantially parallel to its mean direction, so that, throughout the elongated piece, the fibers remain substantially parallel to the longitudinal direction of the part, which is favorable for working with wood in compression or in traction.

 the method according to the invention also makes it possible to derive a very significant additional advantage from the cutting of the elongated parts into successive sections. These sections are compact and the method according to the invention makes it possible to deliver the whole of one.

structure in loose parts forming small packages, which are assembled on site by the user. the assembly means are very simple. They consist only of bolts which are screwed at the end of each crosspiece to strongly apply the various layers making up each elongated part against each other and bolts which are screwed on one end of each cable. prestressing.

 The elongated parts of a structure according to the invention are composed of successive elementary sections which are separated from one another by a joint which is perpendicular to the longitudinal direction of the part. This joint therefore has no shear or tensile strength and it is therefore necessary to construct elongated parts composed of at least two juxtaposed layers, the joints of which are offset to avoid having joints which cut across the assembly. of the room. Of course, each elongated part can have a number of layers greater than two.

 The method according to the invention makes it possible to build furniture or other wooden structures without any bonding. It facilitates storage, warehousing, transport and handling operations and reduces the costs of these operations. It allows repetitive and automatic industrialized construction which lowers manufacturing costs.

 The following description refers to the appended drawings which represent, without any limiting character, examples of embodiment of various wooden structures constructed by methods according to the invention.

 Figure 1 is an isometric view of a wooden chair according to the invention.

 Figure 2 is an isometric view of a section of wooden frame according to the ivention.

 Figure 3 is an exploded view of part of a curved structure according to the invention.

 Figure 4 is an exploded view of a portion of straight structure according to the invention.

 Figure 5 is a longitudinal section of a prestressing cable.

 Figures 6 and 7 are elevational views of two other embodiments of armchairs according to the invention.

 The present invention relates to the construction of wooden structures, curved or straight, intended to work in bending.

 The term wooden structures designates all kinds of objects such as, for example, furniture, structural elements, ladders, this list not being exhaustive.

 An object of the invention is to provide users with structures made up of prefabricated wooden elements which are compact and easy to assemble, so that they can be sold in spare parts to be assembled by users.

 Another object of the invention is to provide means for constructing wooden structures making it possible to compose wooden parts by assembling small-caliber woods, which are less expensive than solid wood parts.

 FIG. 1 represents a tilting chair 1 which is made up of two feet 2, interconnected by crosspieces 2a and two parallel lateral beams 4 interconnected by crosspieces 5.

 The feet 2 may be straight or have a curve directed downwards. The side rails 4 are curved. Each lateral spar comprises two layers 4a, 4b juxtaposed. Each layer is composed of several curved elements 3, prefabricated in series, which are cut in the wood, so that they are as parallel as possible to the fibers of the wood. If the radius of curvature is small3 that is to say if the curvature is very pronounced this requires the use of elements of short length. If the radius of curvature is large, that is to say if the curvature is not very pronounced, longer elements 3 can be used.

 The joints 6 between two successive elements of one layer are offset relative to the joints 6 between successive elements of the other layer, so that there is no joint plane cutting across the whole of a spar.

 The prefabricated elements comprise mortises 7 which are aligned when the elements 3 are assembled and the cross members comprise, at each of their two ends, a tenon 8 which is engaged in one of the mortises.

 The longitudinal offset between joints 6 is equal to the distance between two successive mortises 7.

 The assembly in the transverse direction, that is to say in the direction of the crosspieces 5 is carried out by means of keys 9 which are fixed on the ends of the tenons by bolts 10 and which lean against the sides beams. The bolts 10 are screwed onto metal parts 12 which are inserted in the crosspieces and which have a threaded hole 13.

 FIG. 3 represents on an enlarged scale an exploded view of two sections of a spar composed of layered gods 4a, 4b.

We can clearly see in this figure the alternating joints 6, the mortises 7, 'the crosspieces 5 terminated by tenons 8, the keys 9 and the bolts 10 which pass through the keys and are screwed onto the ends of the tenons 8. To facilitate the assembly of the elements end to end, each key 9 has on its internal face, a relief boss which penetrates into the mortise 7.

 The beams 4a, 4b are subjected to bending forces which tend to open the joints 6 in the part which works in extension and the cross section of each beam is reduced by half in the transverse plane of each joint 6. To give the beams sufficient flexural strength, despite the presence of the joints, metallic prestressing cables are used.

 FIG. 3 represents an embodiment of a curved structure comprising two prestressing cables 11 which pass through each cross member 5 near each of its junctions with one of the side members 4.

 A channel 14 is drilled right through each cross member.

The cable 11 is engaged in the channels 14, in which it can slide freely.

 The cable 11 has, at one end, a head 15 which bears on the side of the first crosspiece. I1 comprises 3 at the other end, a sleeve 16 which is internally threaded and into which a bolt 17 is screwed, the head of which bears on the side of the last cross member. By screwing the bolts 17, the cables 11 are put in tension 3 which has the effect that the two end crosspieces are strongly supported on the two ends of the beams 4 and exert on them a pre-stress which compresses the wood in the direction longitudinal. The compressive stress due to the cable is antagonistic to the tensile stresses due to bending and they add up algebraically, which makes it possible to reduce or even, if the preload is sufficient, to entirely eliminate the areas working in traction and therefore to confer the longitudinal members 4 sufficient bending resistance despite the presence of joint planes 6 which cannot exert any tensile strength.

 FIG. 2 represents an isometric view of a portion of a wooden frame which can for example be a frame of a prefabricated building such as a hangar, a shelter, a greenhouse, an indoor sports hall, etc. This frame comprises wooden arches 18 which are interconnected by purlins or wooden sleepers 19.

 Each hoop 18 is composed of at least two identical hoops I8a, 18b joined against each other and each hoop 18a or 18b is composed of prefabricated and curved wooden elements 20 which are joined end to end by joints 21, which are crisscrossed from one layer to another.

 Figure 3 shows both the assembly of the elements of a chair according to Figure 1 as the frame elements according to Figure 2, these assemblies being similar.

 FIG. 4 is an isometric view of part of a wooden structure according to the invention which is composed of two straight elongated pieces 20, for example two wooden beams or two beams which work in bending, and cross members 21 in timber which are perpendicular to said parts and which connect them to each other.

Only one of the two beams 20 is shown in FIG. 4. It can be seen that this beam is made up of two identical half-beams 20a, 20b joined together. As a variant, it may include more than two contiguous beams as in the case of FIGS. 1 to 3. Each half-beam is composed of rectilinear prefabricated elements 22 which are juxtaposed end to end, the joints between elements 21a being located in perpendicular planes to the longitudinal axis of the beams and being crisscrossed from one beam to another.

 Each element 21 comprises a mortise 23 which is located in the center of the element and two half-mortises 24a, 24b which are situated at the two ends and which cooperate with two half-mortises of the two neighboring elements to form two other mortises.

 The crosspieces 21 have at their two ends a tenon 21a which comes into contact with the mortises of the two half-beams which are aligned.

 FIG. 4 represents a key 25 comprising a boss 25a, which fits into the external end of a mortise, the key 25 then coming to bear against the external flank of the external half-beam 20b. It also represents a bolt 26 which passes through the key 25 and which has a countersunk head 26a which bears against it. The bolt 25 enters a hole 27 drilled axially in the end of a cross member 21 and it is screwed into a metal part 28, which has a threaded hole 28a, which part 28 is engaged in a hole 29 drilled perpendicular to the cross member and is positioned in this hole, so that the threaded hole 28a comes out aligned with the hole 27.

 FIG. 4 represents an embodiment in which each half-beam 20a, 20b comprises, on its internal wall, two half-grooves respectively the half-grooves 30a and 31a for the half-beam 20a and 30b, 31b for the half beam 20b. These half-grooves are placed on either side of the median plane containing the mortises 23, 24. When the two beams are joined, the half-grooves 30a and 30b are placed opposite and they define a first groove in which a first prestressing cable 32 is placed.

 Similarly, the two half-grooves 31a and 31b define a groove in which a prestressing cable 33 is placed. The prestressing cables 32 and 33 slide freely in the grooves and they are supported on the two ends of the two half-beams to put them in compression when the cable is prestressed in tension.

 FIG. 4 represents a preferred embodiment in which each beam comprises two prestressing cables placed on either side of the neutral fiber, that is to say an upper cable 32, which is placed in the working zone in compression when the beam bends and a lower cable 33, which is placed in the zone which works in traction when the beam bends.

 This embodiment allows the beams to be assembled and the cables to be prestressed to the ground and thus to be able to handle the assembled beams.

 Alternatively, one could use a single prestressing cable 33 placed in the area that works in compression.

In this case, it is necessary to assemble the beams in place by placing them on props, then put the cable of each beam in tension before removing the props.

 FIG. 4 represents an embodiment in which the prestressing cables are housed in grooves hollowed out in the parts which work in bending. This embodiment has the advantage that the prestressing cables are not visible after assembly. It is well suited for straight pieces.

 In the case of curved parts, if the cables are housed in grooves dug in the wooden parts, they risk shearing them in the plane of the joint between parallel parts.

 I1 is specified that in the case of curved parts, the cables can be placed in metal sheaths, for example sheaths in the form of helical spring with contiguous turns of the type of those used for the passage of the brake cables, which sheaths are housed in grooves located in curved wooden rooms.

 Figure -4 shows an embodiment in which the prestressing cables are housed in grooves formed by two half-grooves hollowed out in the internal walls of the two half-beams.

 This embodiment has the advantage of facilitating the installation of the prestressing cables. It should be noted, however, that the invention is not limited to this case. The prestressing cables can be threaded through channels dug in the mass of each half-beam, which has the advantage of allowing each half-beam to be assembled on the ground.

 Figure 5 is a longitudinal section showing the two ends of a prestressing cable 11 passing through crosspieces 5a, 5b.

 This figure shows the head 15 of the cable which bears against the external flank of an end crosspiece 5a. A washer can be interposed between the head 15 and the cross member to distribute the compression stresses.

 We also see the threaded sleeve 16 which is welded to the other end of the cable and the bolt 17 which is screwed into the threaded sleeve 16 and which is placed inside a housing 34 hollowed out in the other cross member of end 5b, so that after mounting, it is not visible.

 The head of the bolt 17 is supported on a spring 35 which is compressed when the bolt 17 is screwed into the sleeve and which transmits the compressive stresses to the cross-member 5b by means of a metal part 36.

 The presence of a spring makes it possible to maintain a substantially constant cable tension despite the lengthening of the cable over time and the creep of the wood.

 The structures according to the invention are prefabricated in the workshop and are delivered in spare parts having reduced unit dimensions, which makes it possible to transport a structure together in a small volume.

 The user easily assembles the elements together to reconstruct the structure, he sets up the prestressing cables, he tends them and this tension is enough to ensure the cohesion of the assembly and good resistance to bending despite the existence of joints located between the successive elements making up each of the elongated parts of the structure.

 Figure 6 is an elevational view of another model of chair having a structure according to the invention.

 This chair differs from that of Figure 1 in that the legs 37 are curved and are composed of two arches connected to each other by crosspieces and each arch is itself composed of two juxtaposed half-arches, which are kept applied l 'one against the other by keys which are connected to the crosspieces by bolts according to the method of assembly shown in Figure 3.

 Each half-hoop is composed of several elementary sections 38 which are juxtaposed end to end, which are held in this position by prestressed cables connecting the crosspieces. A chair according to Figure 5 is therefore composed of two structures according to the invention, a first structure which constitutes the side rails 4 and the crosspieces which support the cushion and a second structure which constitutes the two legs 37 and the crosspieces which connect them.

 FIG. 7 represents an elevation view of another embodiment of a relaxation chair according to the invention which comprises only two longitudinal members 4, connected together by crosspieces on which a cushion or an air mattress 39 is placed. The longitudinal members 4 and the crosspieces are identical to those of the chair according to FIG. 1.

 Bringing the ends of the pieces of wood perpendicular to the fibers into contact with each other may cause the harder parts to penetrate the softer parts. In the case of high compressive stresses, this difficulty is avoided by interposing a thin metal sheet in the joint planes between successive pieces of wood.

Claims (11)

 1. Wooden structure available in spare parts of the type comprising curved or rectilinear wooden parts (4, 10), of elongated shape, working in bending, which are composed of several juxtaposed layers (4a, 4b, 20a, 20b, 18a , 18b), characterized in that each layer consists of a plurality of elements (3, 20, 22), which are delivered separate, which are assembled by the user who applies them end to end against one another. other, so that the joints (6, 22a) between elements of the various layers are alternated and said structure further comprises cables (11, 32, 33) of prestressing, which are delivered disassembled and which are laid and tensioned by the user in order to compress said juxtaposed elements (3, 20, 22) longitudinally.  2. Wooden structure according to claim 1, characterized in that it further comprises crosspieces (5, 19, 21), which connect two by two together two parallel elongated parts (4; 20). And which comprise, at their end, a tenon (8, 21a) which is engaged in a mortise (7, 23), which crosses said juxtaposed layers and it comprises, - in addition, keys (9, 25) which bear against the external lateral flank of said elongated parts and which each cooperate with a bolt (10, 26) which passes through said key and which is screwed into a metal part (12, 28) which is inserted into said cross member and which comprises a threaded hole in which said bolt is screwed.  3. Structure according to claim 2, characterized in that it comprises two prestressing cables (11) which are housed in channels (14) which pass right through said crosspieces (11).  4. Structure according to any one of claims 1 to 3, characterized in that each of said elongated parts comprises at least one prestressing cable (33) which is housed inside said part in the area which is subjected to tensile stresses.  5. Structure according to claim 4, characterized in that each of said elongated parts comprises a second prestressing cabal (32) which is housed inside said part in the zone which is subjected to compression stresses, so that 'It is possible to assemble the said piece to the ground before putting it in place.  6. Structure according to any one of claims 4 and 5, characterized in that the said prestressing cable (s) (32, 33) are placed in grooves each formed by two half-grooves (30a, 30b and 31a, 31b) dug on the internal faces of two juxtaposed half-beams.  7. Structure according to any one of claims 4 and 5, characterized in that said elongated parts are curved and said preload or cables are housed in metal sheaths which are placed inside said elongated parts.  8. Structure according to any one of claims 1 to 7, characterized in that each of said prestressing cables (11, 32, 33) at one end a head (15) which comes to bear against the side of a crosspiece. (5a) or against one end of an elongated part and it comprises at the other end a threaded sleeve (16) into which a bolt (17) is screwed, the head of which rests on a spring (35) which is placed in a housing (34) hollowed out in an end crosspiece (5b) or in one end of an elongated part.  9. Furniture available in spare parts, characterized in that it comprises a framework according to revtndicatîon 2, which is composed of two curved beams (4), which are interconnected by crosspieces (5) - and each beam has two juxtaposed layers (4a, 4b), each layer being composed of prefabricated elements (3). which are juxtaposed end to end, with intersecting joints and said piece of furniture further comprises two prestressing cables (11) which pass through said cross members (5).  10. Building frame available in separate parts, characterized in that it comprises a structure according to claim 2, which is composed of parallel curved or rectilinear beams (18, 20) which are connected together by crosspieces (19, 21 ) and each beam -is composed of at least two half-beams (18a, 18b or 20a, 20b) which are juxtaposed and kept applied against one another by keys which are fixed to the ends of said crosspieces by means of bolts (26) which are screwed into metal parts (28) inserted in said crosspieces and each half-beam is composed of elementary sections (22) which are juxtaposed end to end, the joints between sections being alternated and-each beam comprises at least one prestressing cable (32, 33) which exerts a compressive force on the two ends of said beam and which keeps said elements assembled end to end and makes it possible to resist bending forces.  11. - A method of constructing wooden structures according to any one of claims 2 to 10, characterized in that it comprises the following operations: industrially prefabricated wooden elements, curved or straight, of short length, intended for be juxtaposed end to end to form elongated parts composed of at least two juxtaposed layers whose joints are alternated and crosspieces intended to connect two to two two elongated parts and to maintain said layers applied one against the other, by means of key and bolts which pass through said keys and which are screwed into metal parts inserted in housings perpendicular to said sleepers, packages are delivered to users containing, in separate pieces, said elements, said sleepers, said keys, said metal pieces, cables prestressing and tensioning bolts of said cables and the user performs juxt assembly himself placing said elements end to end to constitute said elongated parts, it assembles said sleepers with said parts by means of said keys and assembly bolts, it sets up the prestressing cables and puts them in tension to obtain overall cohesion .